text:
HDPE as the body of a 3-D Printer?
I've been working on my own DIY 3-D printer recently, and I've been trying to experiment a little with different materials for the body. Someone suggested using HDPE (high-density polyethylene), since it works well on a CNC machine, which would make creating a number of prototypes easy. I know HDPE can also be used for filament, but I've never tried it before. Does anybody have any input on HDPE, or other potential materials for the body? I'm trying to avoid using wood, as I've had some poor experiences with it.

Really hard to beat aluminum extrusion frames. Are you particularly wanting a cut-sheet construction printer?

Not necessarily, but I have a lot of experience with CAD/CAM programs, so I'm trying to use this as an oppurtunity to stretch my design muscles a little.

I've used what is commonly described as UHMW-PE, aka, Ultra-high Molecular Weight Polyethylene for various projects. You may know this material is often used in cutting boards, as it cleans easily and doesn't cut easily.
it does machine in a manner similar to aluminum, although the tool should be cooled/lubricated to prevent a build-up of melted plastic on the cutting edges. You can get away without coolant or lubricant if cutting speeds are slow and the swarf is cleared away from the cutter.
I'd not considered such a material for constructing a 3d printer, as it's expensive, but I've also not compared the prices to equivalent sizes of aluminum.
I'd consider that the use in a 3d printer would be a good substitute for lexan, as one can tighten the bolts without fear of cracking. For bolts subject to rotation or vibration, self-locking nuts are a good idea. If you have use of a broach, cutting out a pocket for the nuts would be easily accomplished.
I have downloaded the plans for the open-source 3d printer known as DICE, which calls for aluminum, but the pricing I've found was excessive for the right quantities. I think I'll explore the same bill of materials in HDPE or UHMW-PE (which may be different names for the same substance).
Equally useful to know is that the material is very slippery, effectively self-lubricating under the right conditions. Unfortunately, for a 3d printer application, I don't believe the self-lubricating part would work for carriages but might be fun to try with linear slides.
It is not as stiff as aluminum, so where stiffness is needed and not provided by the architecture, a thicker piece may be indicated. I can just barely bend with my fingers a piece of 3 mm (1/8") a small amount, but cannot do so for aluminum.
Here's the result of a quick search for UHMWPE:
https://www.interstateplastics.com/Uhmw-Natural-Virgin-Sheet-UHMNV~~SH.php?thickness=0.125&dim2=12&dim3=24 which gives a price for 1/8" white sheet 24 x 12" as US\$ 26.06 while the black version is available only as thin as 1/4" for about US$ 28.00
The equivalent size in aluminum 6061T6 at onlinemetals.com is about US\$ 3.00 more expensive. That is lower than I expected, skewing the idea farther away from UHMWPE than one might hope. The equivalent for 1/4" is almost US\$ 60, quite a bit higher.
It would appear that if you need the thicker stuff, the price is better for plastic, not so good for the aluminum.

My biggest problem currently is trying to determine how thick I want/need the sheets to be in order to create a solid object, that's capable of handling the constant vibrations of a 3-D printer, without causing any problems, so until I have a better idea of the exact dimensions, I probably won't be purchasing any materials. Either way, I appreciate the info!

I'm happy to have helped. If you want to perform some inexpensive tests, purchase cutting boards from the local big box store. I'm able to get quite thick material of some size locally at less than ten dollars per board.
If you believe my answer qualifies, please click the check box icon. Thanks

The main consideration when building the body/frame of a 3D printer is the stiffness.  The stiffer the material, the less the frame will deform under load, and the more accurate and repeatable your results will be.
UHMW has a Tensile Modulus of Elasticity around 120,000 psi (http://www.polytechindustrial.com/products/plastic-stock-shapes/uhmw-polyethylene)
Aluminium has a Modulus of Elasticity around 10,000,000 psi (Mott, Applied Strength of Materials, 5th Edition, depends on the specific alloy)
Aluminium is around 100 times stiffer than UHMW.

I'd be curious to know how the figures compare for lexan sheet at 3 or 6 mm thickness, considering how many 3d printers use it for construction.

Lexan (Polycarbonate) has a modulus around 340,000 psi (http://www.sabic-ip.com/resins/DataSheet/Internet/PDF/1002002131_1002003947_1002038344_SI.pdf)

Loving the 'Lets apply science' answer.

One piece of the science I'd like to see applied is what happens to the stiffness of acrylic when the bolts are tightened enough to keep the geometry of the frame from changing. I would expect that the cracks will propagate into the frame and destroy the stiffness.
I'd also suggest that one can crank down pretty heavily on bolts in UHMW-PE without cracking.

I've tried this material (8 mm thickness) for a Prusa i3 clone of my own design but needed to abandon using it as it doesn't allow to be cut by laser easily on my friends laser cutting machine (not a hobby laser cutting machine, it is his business).
HDPE requires lower speed than cutting Plexiglas or Acrylic resulting in more heat input and a small top cut and a large bottom cut width leaving the edges far from being straight.


text:
Slicer that exports vectors or pics for every slice
For a large scale project, I need a slicer which gives me the slices as image (BMP or vector).
I have a 3d model and want to assemble it manually using large printouts on  cardboard. For this I need my 3d model somehow sliced into 2mm layers, get a silhouette of the outline for every layer  and print it in cardboard. Later all cardboard layer will be cutted manually and glued  in the right order.
Does somebody know a slicer, which gives me as output images for every slice?
Or any different idea how to geht my large cardboard 3d model?

Your approach is one of many and you may find that Slic3r will do as you require.
There's a direct reference to generating SVG files (vector) at this link:
http://manual.slic3r.org/advanced/svg-output
You may have to create a printer profile based on irrational figures when compared to conventional 3d printers. Your 2mm "layer height" should be matched in the printer settings to an appropriate nozzle diameter for the desired result.
You may find also that Simplify3d will create such files, but it's not a free program.
An alternative to 3d printer slicing software would be to use OpenSCAD to import your model (or create it directly in code) and use the Projection command to generate the individual layers. I've done this and found it works well, but the process to learning the necessary code was time consuming, as I'm not a programmer.
You would also want to incorporate some form of registration in your model, cylindrical holes or external tabs to enable you to properly align each cardboard layer.
If you have a makerspace nearby or know someone with a suitably sized laser cutter, you may also save some labor cutting each panel, as the laser will accept the vector files easily.

Perfect answer. And thanks for the registration Mark tip.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


text:
Car Body shop Printers
What type of printer would one recommend to print and cast car body parts fast on a large scale? Also if I were to print parts for restoration would I need licences from the manufactures?

3D printers are not typically used for this, maybe just for prototypes by large corporations using very expensive laser metal printers. Have a look into CNCs instead.

Why do you want to 3-D print as the method of production for auto body parts? The main advantage of 3-D printing is the ability to customize each print, rather than requiring large amounts of the same design (as becomes advantageous under mass-production manufacturing methods). In addition, 3-D printing will have structural challenges which are not seen in metallic parts (if that is what you are replicating).

@J.Roibal But what if you want to produce a one-off part for a car that is long out of production?

@TomvanderZanden yeah, that's a valid 3D printing use case. It doesn't seem to be what the asker is asking though: "...print and cast car body parts fast on a large scale"

check out http://web.ornl.gov/sci/manufacturing/media/news/detroit-show/

You may also want to look into something like a CNC Router for cutting molds. You will find you can cut a large shape faster than you can print it.   You could also mix a cut mold with 3D printed inserts into the mold to add features that a 3 Axis CNC Router couldn't make. This could also ease un-molding of your casts.

The Materialise Mammoth printers seem to be the predominant choice for manufacturing car body parts. However, any sufficiently large printer (e.g. bigrep) could work. That said, car body parts are quite a challenge to 3D print given how excruciatingly long such large parts take (exacerbating the probability of failure). You will have to very carefully consider whether 3D printing is right for your application (it probably is not).
The licensing part is extremely complicated. You'll have to deal with patents (perhaps the body part incorporates some clever patented feature), trademarks (you generally can't reproduce manufacturer's logo's) and copyrights (if the part is very "artistic" it might be protected by copyright, but this is unlikely). A simple, functional part such as a body panel would generally not be protected by any of these but these three things are the main reason why you might need a license.
In addition, you have to be careful as to which materials you use, as these will (most probably) not be as strong/durable as those that are produced by car-parts-manufacturers. Furthermore, if you print the parts yourself, install it in a customer's vehicle, and the vehicle malfunctions, as a result, you may find yourself being sued.

Tom, @PMARINA added the last section as a suggested edit. If you feel it is disconnected from your answer, then perhaps PMARINA should add it as a separate answer instead.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What to do with failed/unwanted 3D prints?
I am planning on getting a 3D printer soon and I was just wondering, what do you do with 3D prints that either failed or were prototypes that you no longer want?
I tried looking online but the closest I got was effects on environment, turning prints back into filament, or restarting a failed print half-way, none of which were the information I was looking for.
The solution should be somewhat eco and just keeping unwanted prints in a box somewhere isn't a very good solution either.
Finishing off failed prints isn't totally applicable because it wouldn't apply to prototype prints that you don't want to keep.
Is there anywhere to send failed 3D prints for professional recycling, or are there any recommendations for properly disposing 3D prints?
In case this is of any use, the printer I am planning to get uses filament that can be made of PLA, ABS, Nylon, and possibly other materials. The printer is this one specifically (https://www.kickstarter.com/projects/101hero/101hero-the-world-first-us49-3d-printer) from KickStarter.

Possible duplicate: http://3dprinting.stackexchange.com/questions/59/how-to-recycle-filament-material-from-printed-parts?rq=1

Please note, the 101Hero Kickstarter is widely expected to be either a massive flop or utter garbage. Best case scenario, you get a very low quality printer in something like a year. I strongly recommend you pick a different first printer. See http://3dprinting.stackexchange.com/questions/1211/least-expensive-3d-printer/1212#1212

Some of us mix ABS failed prints with acetone to make "abs slurry" (helps with bed adhesion and gluing ABS prints together) or grind it into pellet and extrude our own filament. Otherwise, printed plastic is just plastic, throw it in the proper recycle bin for plastics, and if there isn't any in your state, just throw it away, the government and giant corporations pollute orders of magnutides more than you will in your whole lifetime, environmental impact of failed prints in the trash can should be the least of your concerns then.

101Hero can only print PLA. The extruder can not get hot enough for ABS, neither is there a heated bed.

I found this website by searching on Google, 3D Printer Filament Recycler l RePLAy 3D. It looks like a recycling club were you get points / can exchange it to buy filament or something like that.

The "obvious" answer is re-grinding the prints and making more filament. Unfortunately, this isn't yet a very economical or simple operation. A decent filament extruder capable of holding acceptable diameter tolerances is around $1000, and even then they can be pretty fidgety to operate. You have to have a LOT of volume throughput in your filament extruder for regrinding to be an economical proposition.
Some of the reasons why recycling prints into filament can be difficult:

Most plastics will degrade to some extent each time they are extruded. (Both by the 3d printer and by the filament extruder.) PLA will thermally degrade with extended exposure to heat. PET will hydrolyze and break down if not meticulously dried to remove moisture prior to heating to the melting temp. (PETG seems to be less prone to hydrolysis damage than plastic bottle PET, but it still happens to a limited degree.) ABS holds up to extrusion conditions better than most, which is part of why it's favored for injection molding, but there's still the potential to affect properties by depleting additives or cooking out plasticizers. In practice, this means regrinds generally need to be mixed with fresh pellets at some ratio. That dilutes the degraded or additive-depleted polymer with good material so you can maintain the material properties and performance.
If you print a variety of different colors, and don't want all your recycled filament to mix and end up a muddy brownish color, it can be difficult to manage the color sorting and matching. Most people don't want different colors along the length of a spool, either. So the regrind has to be mixed evenly in with virgin pellets and a suitable amount of masterbatch colorant to get a reasonable color output. You're not going to run off a new spool with 95% virgin pellets just to recycle a 50 gram failed print, are you? Likewise for material matching. Mixing materials is a bad idea. If you only print white PLA, this is all pretty easy to manage. But if you print a variety of colors and materials, you've got to set up a material tracking, sorting, and storage operation. You can do it... it's just a hassle.
Diameter control is difficult. 3D printers need a fairly tight diameter control for reliable performance and good quality. This is really the key challenge in any filament extrusion process. Extruded polymers like to change shape as they extrude and cool due to molecular alignment effects. You can't just push molten plastic out a 1.75mm nozzle -- "die swell" will make the extrudate bulge to a larger diameter immediately upon exiting the nozzle. Then you have to actually pull on the soft filament as it cools to carefully draw it down to the right diameter. The way the filament extruder measures diameter and controls tension is the key to getting acceptable results. Most hobbyist/desktop filament extruders have not succeeded at this.

Those are just the major issues. Filament extrusion is a complex subject with a lot of depth. For a home user of 3d printers, making filament basically becomes a whole second hobby. In my opinion, it only really makes sense in a commercial production printing environment where paid technicians can run the extruder(s) and a very large print throughput makes the pellets+regrind economics much more favorable than just buying new filament.
Reducing and reusing are preferable to recycling. Making your printer more reliable and gaining experience with calibration/configuration will reduce the volume of waste produced.
There are also some productive uses that let you reuse unwanted prints as-is or "downcycle" them for productive uses.

I personally keep a box of failed prints (and calibration prints and
no-longer-needed prototypes) as showpieces for people who want to
learn about 3D printing, and as toys for my nieces and nephews. I strongly recommend doing your calibration prints with a "toy" calibration model like Benchy or CaliBlocks. 3D printing is still new enough that people will happily take dozens of Benchies off your hands for the novelty value.
Failed and unwanted prints can also be used around the workshop for shims, sacrificial
cushions when clamping or hammering or drilling, or as scrap for experimenting
with adhesives or post-processing techniques.
ABS scraps are good for making ABS-slurry as a print bed adhesion treatment
layer, or for solvent-painting and filling gaps in other prints. Unfortunately, most other filaments do not have such convenient and safe solvents.
Some people have experimented with putting piles of scrap prints on a cookie sheet in an oven and melting them into multicolor cutting boards. There's a lot you can do with this sort of heavy remelt plate if you get creative. (I personally wouldn't use cheap Asian filaments for food contact though, they often have unpleasant contaminants.)

I like your idea of melting scrap parts down into a cutting board. Do you have a link to somewhere that mentions this? I'd do that but want to avoid destroying my oven or cookie sheet.

Hmm, I saw somebody post about it on a forum a couple years ago, can't find a link, sorry. I would assume you cover the cookie sheet with something non-stick (maybe aluminum foil or a silicone baking mat) or use a teflon non-stick sheet, and heat the oven to something resembling 200C/400F. I would also put a little aluminum foil tent over the plastic so you don't get hot spots from the heater elements. Preheat well and leave it in the minimum time to melt into a puddle. Keep a fire extinguisher handy and let us know if you try it :-)

Might be best to try it outside in a cheap toaster oven before using your kitchen oven.

This may be what Ryan Carlyle was referring to https://www.youtube.com/watch?v=G-HWrDMr0ks

It will be very difficult to find a recycling facility that will accept your 3D prints, because they're mainly set up to handle packaging material (which constitutes the vast majority of plastic waste) such as bottles. If you sent your 3D prints to your municipal recycling programme they would at best sort it out from the packaging material and incinerate it, and at worst it would contaminate a batch of recycled plastic (of a different type).
You might be able to find a recycling company that specializes in recycling the plastics used in your printer, but given the extremely low volume involved it is not worth their or your time to handle it.
You should discard your prints as household waste, and offset your environmental impact some other way (by paying for some trees to be planted, or investing in renewable energy,...) - this would be a more viable use of your time and resources.

Exactly what I was going to say. There's a lot of potential for contamination since so many cheap Asian filaments contain garbage and the blends and additive packages used for 3D printing are different from what is needed for injection molding and blow molding.

At Chaos Computer Club summit in Winter there was a talk from a Maker who recycled by himself.
How can be 3d printing a dual use technology? Print more things, produce less waste, save money!
You can see the talk here  https://media.ccc.de/v/32c3-7321-re_cycle
Update: At Fabcon3D in Erfurt/Germany there presented two startups their prototype for filament extruder. You can either recycle old print-puts or compose your own filament with pellets. http://mcubus.com/ and http://3devo.eu/
Im not shure how mature their "product" is. But it will be soon.

If you have a few friends you could pitch in and use a recycling service like Terracycle where you can send your failed prints, rafts and scraps. No affiliation with Terracycle, it's just a service that I found and am considering.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
3D printing with blender
I have an object that I want to print in 3D. But I have a few questions about it. What are the things that I have to watch out for when 3D printing?
I know how to change the metric size etc. Some  people said that it's best to set the thickness to a low amount and not make the object solid (to leave the inside empty/hollow) in order to save money when printing.
Is this true or does it not matter?
Also what if I want two parts of an object to be separate colours or materials?  Do I have to change this in Blender?
Any advice and information would be helpful, thanks.

Information about the printer you are using would be very helpful. Obviously a solid object uses much more material than a hollow one, so you need to find out how the printer interprets your models (do small tests?). Does the printer support multiple materials at the same time? If not, you'll need to pause the print at the right time and swap materials to change colors. You could set colors in blender as a guide, but this won't magically swap spools for you with a basic 3D printer. You may be able to set a stop point programmatically in case you forget, but again, this depends on the hardware.

You are correct about the walls. Using a Solidify object modifier is probably your best bet. A low Thickness: value (0.1 is probably good) helps keep the walls thin but strong. You can monitor the thickness while you adjust the value from Wireframe view.

Additionally, and this is probably the most important thing to know, your mesh must be clean. By clean, I mean it must all be one piece. No separate cubes, cylinders, etc. that you added while modeling, just one solid piece. Think about it this way. If you have added a cube and part of that cube is inside the rest, it might look good from the outside. But the 3D Printer isn't printing the outside, it's printing everything. So that wall, albeit hidden, that is present on the inside of your mesh will be printed.
Bad:

Good:

Lastly, if you have parts of your mesh that can't be printed from the bottom up, or wouldn't stand by itself, consider adding supports. You can always cut these off later.
Leg added because it wouldn't stand by itself:

I have attached 2 images if you look up, i have another question. How should i  place my object for printing? Should i put the text side face down so that it has something to stand on?

@Ulus That would probably be best. If my answer helped, please consider accepting it.

Thanks again, for answering. Also i dont want the object to be solid inside, so would it be best to place a hole behind it? (I saw people do this in video tutorials )And if so where would be the best place? Please let me know if you have an idea i would be pleased :)

@Ulus A hole? The solidify modifier will ensure that it is just walls. Do you want to be able to stick something inside through a hole? If you do, perhaps in the middle-back of the blocky mesh, underneath the center handhold.

Hm ok, i guess extruding and re-sizing the duplicated mesh to the inside will also work, then i will use a Boolean modifier to make a hole with a cylinder, that should work :)

What are the things that i have to watch out for when 3d printing?

non manifold geometry :  geometry that can not exist in the real world.
It's a good idea to check if the dimensions of your mesh are correct before exporting:

Turning on mesh analysis allows visual inspection of problems such as intersecting faces, sharp edges ,edges with thickness below a threshold and other criterias.
the inspection tool will color the faces with those problems.

And lastly you can make selections by traits, such as loose geometry, interior faces or unconnected vertices.

note that those are just tools to help you find the problems , none of them will fix the mesh for 3d printing.


text:
Heated bed thermistor placement
I just recently upgraded my Printrbot Simple Metal with a heated bed (and longer x-axis). I looked up some tutorials, and all of them placed the thermistor as in the picture on the left below, so I did too. However, the design of the heat plate seems to strongly suggest thermistor placement as in the picture on the right, inside the small hole near the center.

I can certainly see the upside of that. The reported temperature may overshoot the average bed temperature (the reasoning used in the tutorials I read), but most of my prints are built in the center of the bed, and the center placement would surely make the temperature control system more responsive.
What are the pros and cons of these placements? And what would be the proper technique for putting the sensor in the center? Should I still use kapton tape? Do I need to make sure the thermistor makes physical contact with the aluminum of the print bed?

Depending on thermistor type you can get values from around 1ohm/C to 0.01ohm/C
so placing it on particulat place on heatbed (HB) could be very important. If objects are placed in the center then it's quite obwious that thermistor should be placed also in the middle.
Another issue in terms of thermistors are the wires. Because thermistors can be so sensitive then wires should have as less influence as possible on its temperature capacity. That's why wires and thermistor legs are so thin. Generally thiner than regular element's legs.
Answering your question - I would say it's better to put thermistor in the center hole, to use thermal grease in the hole so thermistor would have contact with HB. And personally I would use special thin wires to connect thermistor to the board. Kapton tape is then usefull to position thermistor head in the hole and in the thermal grease. Have a look on the picture.

I have such configuration. (In fact I got additional insulation as mentioned in this thread).
I would not recommend to use circuit board tracks as a thermistor connectors at all, but it's my opinion of course.
[edit]
Please be careful - thermal grease can be electrical conductor or insulator. You should choose insulator because short circuit thermistor legs will cause measuring impossible.
[edit2]
As you know HB is not even necessary when you print PLA so in this case it can be even better to not have heating at all than to overheat the bed. Because if you put your thermistor near to the edge of HB then (as said by Leo Ervin) the difference can be at level of 20C so if you heat around 70C and you get 90C your model can become soft on the bed surface and it will loose dimensions or you'll get elephant foot.
As stated in the comments - it's not really big deal whether you measure the temperature in the center of somewhere around. The issue is what level of perfection is ok for you.

Thanks for the advice. But why would you not use the circuit board tracks? They are obviously there for that very purpose.

I disagree with this answer. It's nowhere near this critical, and thermistors are by far not this sensitive. Using the bed tracks is perfectly fine. The purpose of giving a thermistor very thin legs is so that it has less heat capacity (and thus responds to temperature changes more quickly) but given the bed as a whole already has an extremely large heat capacity, anything the thermistor's leads add is completely irrelevant.

@TomvanderZanden I'm a bit confused about what you say. You do confirm that legs are thin to reduce heat capacity, which implies it's is relevant parameter but then you say it's fine to stick thermistor to heating element and you say it's not relevant. It's contradiction, isn't it? ;)

It's not a contradiction. The legs are thin so the thermistor can respond quickly when the temperature is changing quickly. As the temperature is not changing quickly in this application (the heat capacity of the bed is too large for the temperature to change quickly), whether the legs are thin or not becomes irrelevant.

But hot legs and hot wire can be significant component of a measurement. Thermistor wil not measure where it's supposed to. And again you've said it has thin legs (and wires) to respond quickly but you suggest to connect it to thick and capacious tracks (which are hot in fact). IMO this will have influence on the process (of measuring).

The temperature of those tracks is exactly what you're trying to measure. Well, strictly speaking you want the temperature of the bed surface but the two are coupled closely enough that it doesn't matter. Many people just place the thermistor on the underside of the heated PCB (with the PCB separating the thermistor from the build surface) and seem to have no trouble with that. You don't need measurements that are accurate to 0.1 of a degree.

I would use a heatsink plaster instead of thermal grease. Plaster solidifies and sticks to what it is applied to, grease doesn't.

The tracks or wire only matter because (a) they contribute a little resistance to the circuit, and (b) that resistance changes with temperature. But that resistance is in the ballpark of an ohm, and copper changes resistance by about 0.39% (that is, 0.0039) per degree C. The thermistor is about 100,000 ohms. Thermistor resistance change varies a lot, but is typically 100 to 1000 ohms per degree C. A change of 0.39% of 1 ohm in a circuit changing by hundreds of ohms per degree C simply doesn't matter

It doesn't make a great deal of difference where you place the thermistor; do whatever is most convenient for you. The temperature of the heated bed is not very critical, and some inaccuracy in the measurement is perfectly fine. The point is to keep the print from cooling down too fast, and whether the bed is at 95C or 93C makes little difference.
The pros and cons of thermistor placement are exactly as you describe: in either case the center of the bed will be hotter than the edges. Placing the thermistor in the center the temperature of the center will equal the setpoint, while the edges are cooler than the setpoint. Placing the thermistor at the edge the edge will be at the setpoint while the center will be hotter than the setpoint. Placing the sensor at the center you would need to use a slightly lower setpoint to get the same result compared to having the sensor at the edge.
It is possible the holes in the PCB are meant for if the PCB is used with a different printer. In any case, soldering the thermistor to the pads and placing it in the hole is acceptable, kapton tape wouldn't be required then (but can't hurt either). It would be best if the thermistor made good contact with the heated bed surface, using (non-conductive!) thermal paste would be convenient for this (but not strictly required).

Yep, the difference of temperature from the edges to the center is around 20C, however in the center area it is pretty much the same. Here are some thermal images to prove this: http://www.sd3d.com/not-all-heated-beds-are-created-equal/  So unless you decide to put the thermistor very far from the center, it doesn't matter.

How fast do temperature changes in the center propagate to the edges? My main argument for placing the thermistor near the center would be that its reading will more quickly reflect changes from the heat plate, making the whole control system more responsive, resulting in the bed keeping its temperature more consistent.

@mhelvens That's where your PID tuning comes in. If you place the thermistor near the edges, the system will have a greater tendency to oscillate (by the time the edges reach the setpoint the center will have overshot by a great amount) but that's exactly what PID tuning is for: the tuning accounts for the fact there is some delay.


text:
Do I need to recalibrate z-probe offset every time I switch to a different layer height?
It occurs to me that I'm never really thinking about layer height when I calibrate my z-probe offset. This is obviously an oversight, because I'll want my nozzle to start higher for 0.3mm layers than for 0.1mm layers.
After this realization comes the question: Do I need to recalibrate every time I switch to a different layer height? Or can slicers store a reference layer height + probe offset and just deduce the proper starting height for every print? Or is it smartest to keep the 1st layer height constant throughout my prints to spare myself this frustration?
If it matters, my printer is the Printrbot Simple Metal, and my goto slicer is Cura.

All modern slicers adjust the nozzle position for the first layer in accordance with your chosen layer height. You can see this in your gcode if you slice files with different layer heights. Before you add special slicer settings and offsets, if you print 0.1mm layers, the nozzle will start at Z=0.1mm, and if you print 0.3mm layers, the nozzle will start at Z=0.3mm.
There are two reasons this is more complex and less reliable than it seems:
Different slicers assume different initial tramming gaps. And your actual tramming gap may not match that assumption. If the slicer thinks your nozzle is leveled at Z=0 with a real physical gap of 0.1mm to start with, that means gcode Z=0.1mm is actually a 0.2mm gap that must be filled with plastic. So the slicer must compensate by starting lower than the nominal layer height.
So what works perfectly for one slicer won't necessarily work correctly for another slicer. And if you tram with a thinner object than the slicer expects (say a post-it note instead of business card) then your first layer will be off.  This is why I personally prefer physical build plate leveling mid-print using screws while watching the strands go down. It bypasses all the assumptions about tramming gaps and just gives you the correct result. (Or you can do the same thing with babystepping in firmware that supports that.)
The other issue is that people use lots of weird, ad hoc slicer tricks to get their first layer to stick. Things like printing the first layer much hotter, or at half speed, or squashed way down and over-extruded, or at 60% layer height, or at 200% extrusion width, will all affect the extrusion volume calibration and the space-filling behavior of the molten plastic flowing onto the bed. The slicer doesn't really have the ability to understand "your" first-layer adhesion recipe.
The combination of incorrect/unknown tramming gap and person-specific first-layer settings is why the slicer can't always get the first layer height and extrusion volume correct across all layer heights. Within some fairly reasonable assumptions, the slicer is smart enough to always correctly relate extruder flow and nozzle position so it fills the space between the nozzle and whatever surface you're printing onto. But if you break those assumptions, it may perform differently for different settings.

Calibrate to perfection for a specific layer height. When printing in a layer height that is different than what you calibrated for, just set the first layer height in the slicer.
That way, you avoid re-calibration as much as possible.
My experience:
I've overlooked this issue in my experience too. I would usually print in 200 microns. Then for a specific piece I would try to print in 100 microns, and my first layer wouldn't stick. Manually calibrating sucks, setting the first layer height fixes this issue with no discernible drawbacks.

Right, that's what I'm doing now. But if, for some reason, I'd like a different first layer height, it seems like something slicers could support. --- If, for example, we want nuzzle height above the bed to be 60% of first layer height, we would only need to tell the slicer that the probe is calibrated for 200 microns, and it could deduce the proper height for 100 and 300 automatically. --- But I don't think slicers support this. Of course, perhaps the equation isn't that clear-cut.

The first layer is usually squished more to help with the adhesion. On top of that with ABS there's a bit of deformation even if the print doesn't lift. So spare yourself the frustration, FDM 3d printers aren't that precise themselves for you to care about this.

Really? With a print surface like BuildTak it seems to be a very delicate balance between a print sticking too much and a print being too loose. It usually takes some playing around with wrenches for me to get the perfect bed adhesion.

Bed leveling (all points on the bed surface being the same height) is different from what you asked.

Yes. Where did I mention bed leveling?

when you say you have to play around with wrenches all I can assume you mean is moving the nuts up and down of the 3 or 4 screws on the edges of the bed which determine bed leveling

Nope. I meant moving the z-probe up and down.

Honestly, not such a very delicate balance for me.


text:
Creating positives for a food-safe silicone mold: safe?
First, a little background. A couple of years ago, I was researching making my own candy, and I came across this page: Lego brick shaped gummy candies, describing how to use real Lego bricks as a positive to make silicone molds for Lego brick shaped candy. Now that I have a 3D printer, and inspired by the usual description of ABS filament ("It's the same plastic used to make Lego bricks") it occurs to me that I can now make any positive I want.
The question is, would that be safe? I know the filament I'm using is not food safe, but if I create positives for a food safe silicone mold, would toxins leech into the mold? And if so, is there a barrier I can use to prevent this, such as some kind of coating?

In principle, ABS is safe for contact with (cold or room-temperature) food. The two main concerns specific to 3D printing are, assuming you start with a filament that is not itself contaminated:

Pores and holes in the printed part which may harbor bacteria
Impurities introduced into the plastic during the printing process

I doubt that the silicone mold will capture the pores and holes with sufficient detail to be of any concern (it certainly won't capture the internal structure, only the surface).
That leaves us with 2. It has been noted that brass nozzles contain trace amounts of lead. This lead can contaminate the printed part, which may in turn contaminate your mold, which may in turn contaminate your food. I don't think this is of realistic concern, since we're looking at trace amounts of trace amounts of lead. The nozzle might also have burnt plastic stuck to it (which might be carcinogenic) so you should make sure to do the print with a very clean nozzle and at a temperature that is not too high.
ABS is food safe for contact with cold or room-temperature food. It is however not food safe for contact with hot food, because at higher temperatures the food may leach certain chemicals out of the plastic. Your application is one of low temperature, but silicone is not food and might perhaps leach some contaminants out of the plastic, regardless of temperature. However, this concern is not specific to 3D printing, as it applies to the method of making moulds out of Lego bricks as well. Therefore, making moulds from 3D printed positives does not appear to be different in a food safety perspective from making them out of LEGO blocks.

The same grades of brass used to make nozzles are often used to make potable water plumbing fittings... the lead-leaching concern seems really tenuous to me in general with direct FDM part food contact, and even less so for silicone molds.

I'd really like it if this answer included some info on PLA, but I didn't specifically ask for it in my question, and the relative novelty of the material would likely make solid info hard to find.I would assume, however, that PLA would be at least as safe as ABS for this application..

The plastic is not quite your main concern (though it still can be). You should worry about the cracks and crevices in FDM prints. Bacteria loves to hide there. For most people, this is the first concern when it comes to "Is X 3D printed food-safe?" If the end product is a hard material, you should sand or smooth your print to prevent the layer crevices from appearing in the end use product. Also consider food-safe epoxies for filling in gaps. If the end product is made of a flexible silicone, then this is less of a concern.
ABS is not food safe. PLA as a material is considered food safe by the 3D printing community, but I have not seen a scientific study on this. However, many filament makers do not extrude pure PLA. Therefore, the answer to your question is that it depends on the manufacturer. You will need to contact the company to know what is in the filament first. Beware of untrustworthy manufacturers that claim food safety without backing that up.

This seems to pass by the main point of the question entirely: whether it is safe to create silicone molds from 3D printed parts (which would presumably not copy these cracks and crevices from the original part). Note that ABS is a food-safe material if used properly, so your claim about ABS being considered not food safe while PLA is, is wrong.

When comparing PLA vs ABS for this application, basic features like printability and the possibility for acetone smoothing might be of interest. If cracks and crevices turn out to be an issue, then perhaps smoothened ABS parts could be an option provided that the acetone itself doesn't turn the mold toxic.


text:
How to transport a 3D printer? Dismount needed?
I need to transport my FDM 3D Printer because I am moving.
What are the precautions that one should take? Should I dismount the motors and axes? I would definitively unplug the electronics as far as reasonable and fix the motors to the frame so they don't slide during transport. Should I have a housing to avoid dust and other mechanical issues?

If you have PLA parts, protect them from heat. A car can get hot enough to make PLA soft.

Yes, fix the motors and any other loose/movable parts. Remove the bowden tube if it's there, and any other parts that are sticking out. Put the whole thing in a a bag to protect from dust, and put the bag in a box to protect it from getting beat up. Remember to calibrate it when you're ready to set it up again.

I just moved house, and here's what I did: 1) zip-tie moving carriages to a stationary position  2) pack up glass build plates in bubble wrap and boxes  3) remove filament and loose parts like spool holders and feed tubes  4) put the six 3d printers in the back of my SUV, with suitable straps through the frames to keep them from falling over. Worked fine.

sorry for OT, but: 6 printers? Wow. I see now why you call it 'a serious 3D printing addiction' ;)
On topic: Thanks for the info, it could've been it's own answer, in my opinion.

What is the reasoning for removing the bowden tube? Is it just to make the printer more compact and easy to handle during transport, or is it for "safety" reasons?

@TomvanderZanden: Just to make the printer more compact, and to avoid kinking the tube or putting too much strain on the mounting points for the tube. Better safe than sorry. (And at least with my Ultimaker the tube tends to always get in my face when I lift it.)

I also like setting them on a board to prevent flexing of the frame.
My Prusa has a big plastic box I move it around in. A bit like a pelican box. Just dumb luck the top of the printer fits in a grove in the lid so it can't slide around.
My Rostock gets set on it's back on 2 boards that straddle the center column so I don't put pressure on the rods. Support the whole printer to prevent flexing.
Things like to shift forward in a vehicle so orient and protect with this in mind. (Protect from slamming on the brakes).

Transporting a 3D printer does not require special precautions.
Obviously you should package it to protect it from damage (but this depends on the mode of transportation and how sturdy your printer is; if you are just placing it in the back of your car with no chance of it bumping in to anything, no packaging is required at all).
It might be wise to secure the carriage(s) in place so they can't move around, but I would definitely not bother with unplugging anything (apart from the mains power, naturally). Leaving the motors plugged in means they will provide some holding torque, which might be advantageous to keep your axes from sliding around.
Dust is not too great of a concern, as 3D printers can handle it (to some degree) thanks to the seals included on linear bearings.

I would unplug the motors to avoid induced voltages on the motor drivers from sliding axes (which would be fastened anyway, - so that's already contrary to my argument). I've heard that certain drivers are sensitive to induced voltages...

@kamuro Do you have any source stepper drivers are sensitive to this? It seems rather unlikely to me, given that they already have to handle large voltage spikes during normal operation.

It was mentioned in a reprap forum, but I can't find it anymore. Some few people were reporting about burning their stepper drivers by moving carrages by hand. You are right, I also found it hard to believe, but I'd rather be safe and not fry my drivers ;)

One of the youtubers (I forget who) did a test/debunking of that, backdriving the motors at high speeds with the power off, and was unable to damage anything.

You just need to take basic security actions. like fixing all movable parts simple as that

Dan can you expand on your answer? In your opinion, what is the best way to 'fix' (to prevent movement) all of the movable parts?

The way to fix it depends of the printer, but just making it unable to move, that's all


text:
Should I enclose my 3D Printer?
I have a home built RepRap with all sides open..
Would there be any advantage to enclosing the print area in acrylic?

It is hard to tell whether you personally should enclose your printer. However, you asked for the advantages and I will name some of them on which one can base a decision.
A 3D printer enclosure

helps to keep the temperature of the whole print at controlled levels, if you use a heating element, thermocouple and pid regulator. This is one of the most direct uses of the enclosure, which can be achieved by almost no other means. One could sloppily say it does for the whole print what the heatbed does for the initial layers. Controlling the temperature can be beneficial for layer adhesion and can help against delamination problems. This can go as far as fixing cracks and complete delamination (Thanks to @J. Roibal for bringing these cracks to my attention in the comments)
keeps dangerous fumes controlled. Here you can find a scientific study about it, published in Atmospheric Environment 79, titled 'ultrafine particle emission from desktop 3D printers, on exactly that topic. You can embed a filter with a fan in your housing to filter the air from all dangerous fumes that are created when melting certain plastic types. It could just circulate the air inside the chamber or get the filtered air out of the housing. This is another use which cannot be achieved otherwise (afaik).
can keep humidity away from your printer. This is helpful for filaments that attract water (and don't print well under that circumstance). This should be realized separately for stored filament, too, adding some silica gel to regulate humidity. (Thanks to @Obmerk Kronen in the comments)
minimizes losses of your heatbed. This happens in at least two ways, - the heated bed will also heat the surroundings, that is the inside of the enclosure. By raising its temperature, the temperature difference and hence heat loss is minimized. Also wind, introducing high fluctuations in the transfered (i.e. lost) heat is minimized. In that sense, it also
shuts out any wind for print temperature stability. Also dust and particles that could be blown on the print will be shut out (thanks to the addition of dust/particles: @Obmerk Kronen). This is a benefit that comes without having a heated chamber or filter.
helps to keep the printer clean in between use. Your axes will thank you being free from dust.
reduces smell and noise. If you use the printer in you living area, that alone can be a great benefit.
makes sure that your printer is safe during storage, nothing will fall on it.
can look pretty nice and add to the style of your printer, even if selfmade ;-)

There are obviously also downsides, as: connected work/money to make it, increased space used for the printer, and, if not well made for that purpose (which it should be), increased difficulty in repairs and maintenance of the printer itself (i.e. to get the printer out of the enclosure).

From what I understand, certain types of filament must be enclosed to prevent cracking and deformation while printing due to cooling too rapidly.

Do you have a reference for that? I'd love to add the information to the answer!

kamuro - I have been able to find a couple of references including a reddit post which discusses the issue of cracking being solved by an enclosure: https://www.reddit.com/r/3Dprinting/comments/2jn3en/does_abs_always_have_this_cracking/
Additional post by "tommyph1208" goes into depth about this topic: https://ultimaker.com/en/community/9930-help-with-abs-setting-i-have-mad-cracks-between-layers

+1 Very good answer .You might add keeping out humidity . ( That is a plus also for filament chamber ) . and keeping draft ( wind ) from filament and print is a very important point - not just temperature but also dust particles ..

edited the info in, let me know if this is what you thought of.

@kamuro fantastic answer to the question, i'll definitely bookmark this comment for future use.

@kamuro provided an excellent answer, so I'll just try to add by playing devil's advocate.
Possible things to look out for:

Inappropriate enclosure could result in more temperature differences, resulting in higher rates of warping and delamination. For example, if you do not enclose the top of your machine, then the temperature at the beginning of your print will be potentially different than further into the print.
Post-print delamination/warping. The same can be said for a printer without an enclosure. But if you are too eager to remove the print directly after printing, you run the risk of essentially "air quenching" the part. Instead, let the part sit in the warmer ambient temperature and become fully solid again.
Enclosures are not a "fix-all". Enclosures are merely a means of reducing variability in your process. As an operator, you should still fine-tune your process by finding the right extruder/HBP temperatures and quality materials to ensure repeatable, quality prints.
kamuro touched on this a bit, but difficulty performing maintenance. Speaking from experience, removing acrylic panels from a machine not designed to have an enclosure is pretty annoying. However, this could be alleviated with a better design. I chose to bolt my panels to my machine, but a snap design would fair better. Specifically, adjusting my belt tension became very difficult on my Replicator Dual after adding acrylic panels.
Don't make it too hot. I made a rookie mistake after adding an enclosure to my machine by using a space heater in the room next to the printer. The space heater oscillated and occasionally directed the heat at the machine. After a few failed prints, I noticed that the extra ambient heat in the room was causing the ABS arms for my HBP to warp under the heat/weight of the HBP. The enclosure wasn't the root cause, but it helped trap the extra heat inside the machine.

Fantastic addition, I did not consider many of these disadvantages to adding an enclosure.

Yeah, fantastic addition. However I wouldn't call most of these disadvantages, but merely disadvantages that come with design flaws ;) This will help makers tremendously when building their own enclosure!

@kamuro thanks, it was pretty difficult to come up with disadvantages. But I'd agree they're more of things to just look out for when adding an enclosure. Your answer is hard to top lol

People add a "passive heated chamber" when they are printing in ABS. However I personally think the best reason to have a custom chamber is so you can add an air filter. Adding an air filter will reduce your exposure to fine air particulates. It is generally considered a bad idea to breath in particles from plastic.
For PLA you will not want an air chamber. If you want to do an air scrubber they you will need air input to avoid the heat chamber from getting hot.
On that note as we see in the z18, PLA can benefit from an Active heat chamber, but you will have to figure out what the optimal temp is.

Consider the environmental conditions where your printer is.
I have my printer in a garage, where the door is sometimes open, closed, or slightly ajar.  This leads to gusts of wind, causing lifting and ruining multiple prints.
I surrounded the printer on three sides with walls made from the original packing foam, and my lifting problems have utterly vanished.
The top and front side are open, so I have a "four sided" box.  Heat does not build up, but the variable wind gusts are minimised.  Access is slightly reduced, but not a lot.
Ender 3 V2, printing the "Ender" brand of PLA from Creality.  Bed is at 55 °C and print head is 200 °C.

@agarza That is a trivial edit.  Please don't.

If you will be printing PLA, no, or at least not without active cooling of the chamber. PLA's glass transition temperature is sufficiently low that the ambient temperature matters a lot to whether layer N can cool enough before layer N+1 is laid, in order to have a firm surface to extrude against and bond to. This especially matters with overhangs and complex geometry. If you use a heated bed for adhesion, the chamber temperature will tend to reach nearly the bed temperature, keeping your print soft the entire time. In a worst case, it might even cause heat creep and jam the heatbreak. Even if you're not using a heated bed, waste heat from the hotend will warm the chamber somewhat; expect temperatures of at least 35-40 ˚C rather than a (preferred) ambient 19-22 ˚C.

I question the figure of an unheated bed, and hotend alone raising the ambient temperature to 35-40C, when printing PLA. I have thermometers in 2 enclosed printers and see that with the heated bed running 60C for a couple hours- 40C with a styrofoam insulated enclosure, 35 with an acrylic enclosure.
True the enclosure with PLA can lead to heat creep in the hotend, as you are cooling the heat break with hot air. One simple way to get it to work is a heatbreak fan that moves more air. Another is the silicone sock on the heater block, less ambient heat wafting up to the heatbreak.

My TronXY X1 has a 150x150 mm unheated bed and an e3D light6. It can't raise the ambient temperature in its area more than about 1-2 Kelvin. My Ender3 can raise the ambient by 5 Kelvin using the heatbed and the e3D v6. ambient is a whole room here. The actual heating of the room would depend on the machine and the room size.

I'm talking about the temperature inside the chamber, not a whole room. As a reference, on my Ender 3 without a chamber and using an unheated bed, moderate size prints tend to raise the bed temperature from 21˚C to 26˚C or higher even with heavy part cooling. I would expect a much greater effect with a chamber, and you should be able to predict it just from the heat capacity of the PLA and the volume extruded.


text:
How to build CuraEngine?
I've been trying to build CuraEngine on Ubuntu following the Github instructions.
The problem is that it lists some requirements:

Clone the CuraEngine repository;
Install Protobuf (see below);
Install libArcus.

I'm not sure where should I install Protobuf and libArcus. After several tries and locations I've received several errors during the build process.
Does anyone have a more detailed guide on how to build this engine?

This is not a direct answer, but a somewhat large workaround.
Have you considered using OctoPrint? Most installations including Ubuntu, which I use, come with cura-engine installed. If not, it can be easily installed from the plugins menu in OctoPrint settings. OctoPrint is a really nice alternative to native software for various printers.
I had the same struggle with Protobuf and libArcus and OctoPrint worked great.

Have you tried installing using sudo make install in the protobuf and libArcus (after running cmake) directories?

I've tried, but the build does not complete so it is impossible to run the install command.

I'm assuming you actually want to build Cura, rather than simply install Cura. If you instead want to install Cura, you can try sudo apt-get install cura-engine
The following instructions were tested on my own Debian 8 (Jessie) distribution; they should be mostly, if not entirely, the same, for Ubuntu. Note that I did not follow the exact steps as described on the github/Ultimaker/CuraEngine README.
Before we begin, let's make a build directory and do everything in there.
mkdir ~/Downloads/curabuild
cd ~/Downloads/curabuild

The instructions will be broken into
1. Install dependencies
Some or all of these may already be installed on your computer. To be sure, we install them anyways:
sudo apt-get install git curl libtool dh-autoreconf cmake python3-setuptools python3-dev python3-sip sip-dev

2. Install protobuf

Clone and enter the protobuf git repository:
git clone https://github.com/google/protobuf
cd protobuf

Build and install for C++:
./autogen.sh
./configure
make # this will take some time
sudo make install

Install for Python 3:
cd python
sudo python3 setup.py install

3. Install libArcus

Clone and enter the libArcus repository:
cd ../..
git clone https://github.com/Ultimaker/libArcus
cd libArcus

Build and install
cmake .
make
sudo make install

4. Install CuraEngine

Clone and enter repository:
cd ..
git clone https://github.com/Ultimaker/CuraEngine
cd CuraEngine

Build and install
cmake .
make # grab a cup of coffee
sudo make install

5. Celebrate!
If all went well, you're done! You can now use the Cura engine via CuraEngine. Enjoy.

The objective is to build cura engine which runs from the terminal so I can run it from command line, will this end up on installing it without the GUI? That is the objective.

This will not install the GUI. I believe sudo apt-get install cura-engine will not install the GUI either.

I found I also needed sudo apt-get install python3-sip-dev otherwise libArcus would fail on the cmake step.


text:
Not Heated Build Plate Glue Amount and Dry Duration
Background:
I am using the Flux Delta 3d Printer, and it arrived with a glue stick. Now on their forums it said to apply 2 layers of glue and let it dry, there's supposed to be a link there on how long it should dry. However that link is broken.
My question:
On a not heated bed, how much glue-stick should I apply and for how long should I let it dry?

As a fellow Flux Delta owner, I can answer this question with certainty. Two layers is sufficient. Be sure to consider the size of the model being printed and the additional area covered if you are using skirts or rafts.
If you apply the glue stick at the moment you turn on the printer, it will be dry enough to work properly. The printer "uses time" to initialize and to calibrate which provides enough drying time. You will also "use time" to load the software and import the model.
It is not necessary to remove the glue from the plate after a print. For succeeding model printing, ensure that you've filled in the areas missing glue from removing the previous model.
You will want to remove the glue (hot water works good, but the build plate gets hot!) when you feel that the glue build-up changes the texture of the bottom layers.
You may have already learned from the forums that you print on the non-grid side of the build plate.

Thanks so much! That really helped a lot! Can I just as you, did you print out the tutorial print? Because mine came out looking quite weird and uneven...

I never did perform a tutorial print. I'm not sure where it is located.

From Flux Studio, under the help section, there was the tutorial


text:
How often should I replace the glue layers on the bed?
I am printing on a non-heated bed right now, but the question also applies to heated building plates.
How often should you replace the glue layers that's supposed to be applied before printing? Some say you can do up to a few prints, such as in this forum, while others say to replace it every print. What is the correct approach?

Depends on the glue and on your tolerance for messy undersides on your prints. It's fairly common for some of the glue to come off with the print. Or you may have marks from scrapers or rafts. Do you want to touch up that spot and have some artifacts on the bottom of the next print, or clean and redo the bed to get everything flat?
Gluestick is pretty easy to wash and reapply. It can also be freshened up with a gentle spray of water, smeared flat, and redried, or more gluestick added on top. It will really come down to your preferred workflow.

I also do freshup with a spray of weter - this flats up the layer and refreshes of glue layer

I usually add some glue each time I print a new part. I re-apply over places where recent part left a visible "footprint". But after a few prints, the glue layer becomes too thick so it has influence on the height of the first layer. If so,  I dismount the glass and clean it with hot water. I do this after about 5 prints... (+/- of course).
Generally the glue becomes white when it dries up, so I use this as an indication or sign for when it has to be cleaned.
I would say there are no strict rules. Do some experiments and observe the first layer surface. Then you'll find your correct way.

As noted in the answer to the other question you asked, the Flux Delta steel plate bed will handle multiple layers of glue. The determining factor regarding this particular printer and specific glue is how many ripples, bumps and/or lines you are willing to tolerate on the first layer of your prints.
You'll notice that a print made with a couple layers of glue, freshly applied, will have a relatively smooth surface. Peel off the model, apply glue over the now-cleared areas, and you've created a slightly-less-than-smooth surface for your next model.
I've found that I can apply six to ten layers before the ripples become objectionable.

I've recently learned that it's easier to merely scrape the glue residue to a nominally flat surface than it is to wash and scrub the entire plate clean prior to a new print.


text:
M3D filament not extruding well (anymore)
I use OctoPrint on an Ubuntu system with a M3D printer.
Midway through a recent print, the filament just stopped extruding although the motor-functions of the printer were proceeding fine. Since then, every print I attempt has trouble extruding proper amounts of filament. It's always not enough. The output is stringy and not cohesive.
I'm thinking there may simply be a clog in the extruder and wondering the safest way to remove it.
The weird thing, though, is that when I use manual control and extrude at, say, 220C, the filament comes out fine.
You can see the raft definitely isn't printing right. Way too little output:

Suggested remedies for 3-D printers which are not extruding required amount of filament:

First, check the temperature of the extruder. Try 220-225C to see if that improves the problem.
The second step is to increase the flow of the filament (increase mm/sec) for extruder speed.
A final step is to increase distance between extruder and base-plate. If the extruder is too close to the baseplate, there may not be enough space for the filament to begin the printing process.

Another possible source of lack of material extrusion is a clogged extruder. To solve this problem:

Retract filament using jog control in software
Heat extruder 20-30 degrees Celsius above normal extrusion temperature
Disassemble Extruder, use small thin wire to remove blockage (guitar wire as suggested below)

Currently 215C. Was always that way before.

what type of filament are you using?

PLA (from M3D company), as always before.

If it prints correctly at 220C, why not leave it there? In addition, have you lowered the bed slightly?

Honestly that's probably the next best step in diagnosis. I'm going to re-calibrate the z=0 bed location and bed height, then try at ~225C

Turns out recalibrating and setting the extrusion temp. to 225C is doing the trick. Thanks.

But didn't work for long. Back to square one. Quite sure the extruder is clogged with plastic that doesn't want to melt out. I may try to burn it out at 250C or something. Maybe a bad idea?

You might have a case of clogged nozzle. You can check this easily by lifting the Z axis and running the extrusion motor. If it's grinding on filament or you notice extruded plastic is curling or going out slow, it's probably partial or total clog.
I have had the latter variant happen to myself recently, with the same symptoms as yours. Fixing it involved disassembly of the hotend and cleaning the clog manually using jet lighter (to heat up the nozzle) and guitar string to pull out clogged PLA.
You might have some other options available:

Try pushing the filament through hotend by hand, it might clear the clog.
Other variant I've heard of is heating up the extruder to 130-150°C (PLA) and just yanking out the filament, and hopefully clog along with it. I wouldn't recommend this if you don't know what you're doing, as it might damage the printer.

In my case things that were causing the clog were the big retraction distance and temperature being set too high.


text:
How to line up (x,y) print area between hardware and software?
I'm trying to line up the physical print bed of my printer (Printrbot  Simple Metal) to the virtual print area of the slicer (Cura). So far, they've never been properly aligned. It was never that big a problem because, worst case scenario, my print would simply not be dead-center on the bed. But I've decided to try and fix it.
Here are pictures of a test model in Cura, and the resulting physical print:

What's the proper way to align the two? It seems I just got lucky with the x-axis here (though note that the BuildTak surface is a bit off center). But obviously the y-axis needs fixing. The print needs to start a little lower, because print-head couldn't reach the highest point, and the y-axis motor slipped to compensate.
Ideally, the fixed parameters of the print bed size and offset would be set by the Marlin firmware (EEPROM?). But I also need to be able to do a little offset tweaking on the software side for when I need to replace the BuildTak mat.

Edit: I tried M206 (home offset) commands, but the result is definitely not what we want. I cancelled these early.

The upper print has M206 Y-15, the lower print has M206 Y15. What seems to happen is that the coordinate system is not physically shifted. Instead, the area is 'cropped'. All filament that should go outside the boundaries is actually extruded 'on the edge', resulting in an ugly blob.

I have not used cura software, but is there a 'calibration' function?

The word 'calibration' is usually used for the number of stepper-motor steps per mm, or bed-leveling (z-axis). That's what Cura uses that term for, anyway, and it doesn't look like it can play with the Firmware. (Also, Cura is not actually connected to my printer in any way. My printer runs from an OctoPrint server.) In any case, I know how to change the EEPROM values, but I don't know which values to change and how.

If there were lines connecting the squares (horizontal and vertical) to make a grid, where would the error begin to be seen? May need to be tested.

Also--what if the upper-left most square (where the extruder is rattling) was lower (say, 2 cm), would the squares still become offset?

I recall experiencing a bug with Marlin, where the auto leveling feature can cause a shift in the axis positions. Basically, if the probing positions aren't symmetric with respect to the bed (e.g. you probe at y=20 and y=160 with a 200mm wide bed) it would offset the y axis. Changing the probe positions to be symmetric (e.g. y=40 and y=160 or y=20 and y=180) fixed this for me. If this turns out to be the issue I can add it to my answer.

The problem you are experiencing is because the position where the y endstop is triggered does not correspond to y = 0, but perhaps corresponds to y = 15 (replace 15 by the offset you're seeing). You can perhaps solve this by adjusting the endstop to trigger at the correct point, but you can also adjust this behavior in software: In your start G-code, after the homing (G28) command, insert a G92 Y15 to tell the printer that the current position (reached after homing) is actually y = 15.
Another option is to use the M206 command to permanently store the offset in EEPROM (rather than needing to provide it in the start code each time).
If your printer moves towards max rather than min, the same applies, but consider that the offset may be caused by the bed size defined in your firmware not corresponding to the bed size set in your slicer.

Great answer Tom. Is this something seen very often, where the 'bounds' of the printer do not match the software? And what is the most common method for solving this problem? Thanks in advance.

Hi @Tom: I'd like to put this in EEPROM, but the M206 command is not the way to go, it seems. I edited the question to show the results.

I tried this solution (two years ago) and it failed. I attached pictures to show the result.

@mhelvens Sadly you failed, but it is the solution. It is very easy to fix your problem with the solution presented. Alternatively read and execute the link I put in comments earlier. You do not necessarily need to print a square from the link, you could have measured the location of the first square of your failed print to update the bed position. All that is needed is to get the offsets from endstop positions to the corner of the bed.

@0scar: I followed the instructions, and they did not fix the problem. You telling me that it is nonetheless the correct solution doesn't really change much. Reality wins. :-) I suppose it's possible you're right. Perhaps I made a mistake. But I can't accept the answer based solely on that possibility. And I'm afraid that printer is currently out of commission, long term, so I can't try anything new with it for the foreseeable future.

@mhelvens Too bad the printer is out of commission and too bad you did not succeed. This is the solution for the problem, hence the link to a question (explaining a little more in detail) above in an earlier comment. We would have liked to help you out! Just edit your question once you are trying to get it to work and it will pop up for us to see it.


text:
How to 3D Print 5-pointed star object that doesn't have flat bottom and hole in the middle?
I'm new to 3D Printing. I've created this star from Blender3d. As far as I know, most printers require a flat bottom.
As you can see (blue line is Z-axis, red line is X-axis, green line Y-axis), the star doesn't have any flat sides or points.

There's a hole in the middle of the star.

Is there a printer (brand/model) that can print this object that doesn't have any flat bottom or sides having a hole that goes through in the middle? Any workarounds to print this object?

Typical FDM desktop 3D printers might struggle with this model as it requires you to either print large overhangs and use support structure (when printed laying down), or lacks a natural flat bottom surface to get good print adhesion (when printed upright). A couple of suggestions:

Some FDM printers are great at printing support, and some even allow you to print dissolvable support structure. If you find one of these, you are home safe.
You could split the model in two, print those parts separately, and then glue them together afterwards. This is quite common for complex models, and allows you to print your model on even basic FDM printers. Tom's answer illustrates this well.

There are naturally other 3D printer technologies too (SLA, resin etc.), but I have no practical experience with these myself, and leave it up to others to give you a good answer regarding these.

If you don't like the idea of cutting the star in two, the support material is a good route. Even non-dissolvable supports will work, but would leave attach "dots" on the model.
I have a dual extruder printer which uses PVA support material and the surface contact isn't flawless, but it's superior to attempting bridging out to the ends. I think most slicers will create a flat spot of some size, perhaps not as small desired.

It seems that, for this particular 'star' model, that splitting the star in half (to create a flat bottom and remove any overhangs) will be the best solution, and especially because the top and bottom will be identical.

I would suggest to experiment with Meshmixer application and its function to auto calculate position and support pointes. This app is really great with that (while it's not perfect for sure). What is the most important - it can propose orentation which human wouldn't even think of :) Just give it a try.

@darthpixel, that is good advice! Perhaps this model could be printed upright with some decent support pillars?

The existing answer seems to suggest printing the model in the orientation as shown (e.g. with the Z-axis of the part corresponding to the Z-axis to the printer) with either support or splitting it in half.
Using supports in this way is a bad idea, because it will leave a very rough surface finish due to the geometry (and be very hard to remove, unless you want to deal with troublesome support material). The model also will have no contact with the build plate at all, making it very likely that it will detach (even when you're using support, you want a reasonable amount of surface area making contact with the build plate). You'd have to drill out the hole in the middle (since support can not be removed there).
The approach of splitting it in half and printing in this orientation isn't ideal either, because the surface finish will again be very rough due to the very gentle curves of the star. The hole in the middle will also turn out a bit deformed and flattened and require support.
Instead, for this model, a much better approach is to split it like this:

The top half has no overhang at all, and the bottom half only has gentle overhangs that are easy to print without support. The surface finish will be much better compared to printing in the other orientation. Moreover, the hole can also be printed in the XY plane leaving it cleaner as well.

On a side note, slicing the model along this axis will also reduce the chance of the first layer lifting thereby avoiding a "seam" when you glue it together afterwards.

Great suggestion Tom. My question is, how did you 'come to understand' this line of symmetry? Was there some type of software or just plain and simple intuition and experience? Thanks in advance.

Just intuition.

The split can be done easily in OpenScad.  import the existing model and subtract out a large cube where the top is.  rotate the other piece so the cut side is down on the print bed.  Save it.    Then do another one where you subtract a large box from the big side.  Rotate it and save it.


text:
Pulling filament through long tubes
I'm setting up my printer in a small room, and I thought I'd come up with a system for more easily swapping filaments, but I'm not yet sure it is feasible.
Rather than physically replace the spool, I'd like to hang most of my spools on the wall, where they can rotate, and only swap filament leads in the (direct drive) extruder. The spools would be placed at some distance from the extruder, and at various angles. So to make sure the filament is pulled from the spool at the proper angle, and to avoid breaking it, I think it should probably run through a flexible tube to reach the printer.
I know such tubes are used for Bowden style extruders, but what I'm proposing is different in at least two ways: [1] the extruder motor would be pulling (not pushing) filament through the tube and [2] the tube would be longer than normal, e.g., between 1 and 2 meters.
Is this plan feasible? Or are the problems I am not foreseeing?

Edit 1: I don't know where I got 1-2 meters from. The distance is actually closer to 50cm.
Edit 2: To clarify my proposed setup, here's a crude mockup:

Fantastic approach and I really like the possibilities that this idea creates. My questions: How would the printer know to swap filaments, and which filaments to swap? (potentially written into the G-Code?) How will the printer swap the filament? In answer to the second question, I am envisioning some type of cutter which then melts (fuses) the second filament to the first, but how can this be accomplished in a uniform fashion? Anyways, I think this is a fantastic idea, I'll be watching this thread closely! Contact me if I can help in any way.

@J.Roibal: Your interpretation is a bit more ambitious than my actual idea. :-) I was still thinking of swapping filaments manually, just minimizing the time and effort required. This would certainly help you to hot-swap filaments during a print, but I currently have no plans to fully automate this. --- I know about another recent project you may be interested in. But it's a bit more pricey than what I have in mind.

my heavens, mhelvens! I can totally see how this could become automated, removing the necessity of dual-extruder 3-d printers while adding the capability to print in dozens of colors and types of materials, automatically.

@J.Roibal: Sure. I can see that too. And I may automate the process in the future. But it would be a hobby project, as this is, and I would not achieve the precision required for multi-color prints. Developing that technology would be a full-time effort, because it is more complicated than you might think. --- Anyway, as I hinted in my previous comment, the technology you want does already exist. Have a look at the Palette. I wish I could afford one.

@J.Roibal: The Palette splices multiple filaments into a single stream, as you suggest. The problem is that colors mix together in the hot-end. To get crisp color-swaps, they build a 'transition tower' on the side of the main print, to purge the mixed plastic. --- The solution we're talking about here would work differently. For every swap, it would retract the current filament, and start extruding another. This would probably evolve into multiple Bowden extruders feeding the same hot-end, and might not produce as much waste. Sounds like a fun project. But I do have a day job. ;-)

Interesting idea. Sadly you are overthinking it.
At the hackerspace we have plenty of setups like this, but we do not bother with tubes. Just hang it and go :-)

@StarWind: Could you link me to some examples, perhaps? With pictures / descriptions?

Yeah so it is the guys who make the Flexon extruder.. here is their site with photos
http://diabasepe.com/

I would say it's not the best approach.
In the situation you've described I would rather install some kind of vertical ring a bit above your printer. This ring would organize your filament going from any direction.
So let's assume you got one spool on the right and one on the left of your printer, both are 1m away from the printer itself. If you get filament and put throught the ring then to your extruder.
In my opinion the ring should be around 15..20cm over the printer, it should have around 10..15cm diameter and spools should not be too low.
The only issue I see is unwinding spools which are too far from the printer because then filament would be unwinded angular but the same issue would be with and without teflon tube.
[edit]
Here is a simple change of your design

[edit2]
Please also note that you can assure proper angle of unwinding filament by installing small rings ("eyes") next to spools. These eyes will direct filament out of spool and then filament will turn to your big ring mounted on the printer. This is common solution in textile industry

Thanx Tormod. Acording to my experience - tube longer than 1m is not a good idea. #1 it's harder to pull/push filament. #2 such long/heavy tube has influence on movement of the caret. #3 it's uncomfortable to install/uninstall filament

I absolutely agree, Darth! :-)

I'm not sure I understand your proposed setup with the ring. Would it be too much trouble to ask for a quick mockup image (like the one I added to the question)?

And the issue of pulling filament at an angle (and expecting the spool to keep up) is the reason I'm suggesting tubes. If the filament angle is properly guided at the source, I don't see that as a problem. Thoughts?

@mhelvens please take a look on my post (edit). Please also note that rings can be used on both sides of the design (Thanx Tormod). You can apply little "eye" next to the spool which will assure the filament is unwinded at proper angle, then there could be a loooong way to the ring proposed by me :) (of course on that way there could be even more rings which will direct filament properly)... assuming you are pulling, which you do

This is somewhat similar to a question I asked a while back. Pay attention to Ryan Carlyle's response in the question I posted. His post essentially explains various ways that guide tubes may hinder extrusion due to drag. In regards to the length of your guide tubes, ensure that the tube is relatively straight.
If you are holding the filament above the machine, chances are that you wont really need the tubes anyways and the distance between the spool and the extruder won't matter either. The point of tube is to ensure the filament doesn't bind coming from the back of the machine, thus potentially clogging your extruder.
Update
Based on the OP's drawing, I think it would benefit to change the design to drop the tubes all together. The tubes can provide many point of contact and managing so many lines at once may become problematic. So, possibly drop the tubes and intend on not drawing your filament unless they are fed into the extruder. You could install smaller ends of tubes at either end of assembly (one at the storage rack, the other above the extruder) to ensure the filament is being fed/pulled straight. The space between the storage rack and the machine doesn't matter. Here's a basic edit of your design that might be easier to manage. For kicks, here's a design I made for my own machine as a "quick-change" design.

Even if the spools hang above the printer (which is the plan), I feel like things might go wrong if the extruder tries to pull filament from the spool at an awkward angle. Anyway, the answer you're referring to is useful. Thanks!

Thank you for uploading your sketch, it helped understand more of what you're trying to achieve! +1

I would like to add to the already great discussion, that this general approach is prone to filament degradation by water intake. That is, if you are using filament for which this is an issue (PLA as the most prominent example).
Also, your goal is to exchange more quickly, that is without (un-)mounting whole spools each time. Basically you want to have a multi-filament spool holder, if I understand correctly. If you design an enclosed box with a single outlet you could incorporate silica gel inside and a reduced effort to swap the filament. I would still avoid a nice free-hanging spool solution due to the degradation issue.

A good point! An enclosed box would definitely be a good move. This also seems to be an argument in favor of tubes all the way, rather than short filament guides on both ends. --- I don't understand your "box with a single outlet" plan, though. I don't see the point, and it would probably complicate filament swapping, because I'd have to open up the spool enclosure to feed a new strand through the tube. Right now I'm still inclined to run a bunch of separate tubes to slightly above the extruder, like in my mockup image.

Yes, if you can get the tubes somewhat airtight or don't use the first part of the filament each time you swap, your idea works better. Why wouldn't you want the whole box very close to the printer so that you wouldn't need the individual tubes altogether? Having 5 tubes being moved by the carriage is additional load to the motor that doesn't benefit the print itself.

The placement of the spools is purely a matter of constraints in the printer-room. It turns out the spools would have to be at a distance of about 50cm. --- Moreover, as J. Roibal has suggested in a comment, it may be fun to try to fully automate filament swapping some day. I'd definitely need individual tubes for that. Would multiple tubes really add significantly to the load? I'll have to experiment.

The load may depend on how the tubes are directed to the printer. I had a problem when building a repstrap, - as soon as the bowden tube was attached, the motor wouldn't move anymore. Truth be told, it was a tiny cd laser carriage drive motor, but but it moved flawlessly without the tube. You can easily find out how much you have to increase the current at the border to losing steps. I would guess that it doesn't influence your printer too much (watch ghosting), but if it can be easily avoided, why shouldn't one think about it when designing ;) Fully automated sounds like real fun ;)

Yes, this is feasible. You should constrain the tube at both ends, this prevents the spool from pulling up on the extruder. This approach is known as reverse bowden setup.

What do you mean by 'constrain the tube at both ends'? Are you simply suggesting that neither end should hang loose? Please have a quick look at the image I added to the question, to see if it matches your meaning.

Yes, this matches what I mean. Without the tube, the force required to get the spools to unwind is transferred to the extruder (possibly moving it around and decreasing print quality). With the tube in place, that force is instead applied to the mount of the tube.

This shouldn't be too much of an issue, as long as:

You guide the filament properly to avoid breakage (at both ends as Tom mentions)
You avoid too much friction between the pulling extruder motor and the spool itself.

You mention that you consider using a 1-2 meter teflon tube to guide the filament. Although this might work, long teflon tubes will increase the friction from pulling the filament. Furthermore, I really doubt having such a long tube will be beneficial at all; quite on the contrary, I think it could be rather impractical. Most likely, having simple guides at both ends (whether its tube stubs or rings) will suffice.

Aha. Guides at both ends, rather than a tube all the way. I can see the sense in that. Now that I think about it, other answers (like darth pixel's) may also have hinted at this.

@mhelvens, I believe that both Tom and Darth hinted at this. Whether it's a tube or rings probably doesn't really matter that much. :-)

@TormodHaugene Actually, tube v.s. rings makes a difference. A tube has the advantage I mentioned in my answer, rings don't.

Your idea is actually good, but i would add some edits to it. First of all, to keep your equipment clean, you would like to add little foam rubbers to clean the filament at the entrance of the tubes, to clean out the dust that will be accumulating over the rolls.
Another thing that i would recommend is to hang the tubes on a separate support for them and not on the extruder head, as it would add some additional friction to it and can cause the 3d model with additional friction making it distorted.

Can you discuss your improvements further? I am interested in the maintenance portion of your answer, in particular.

@DanBoyko: I'd be interested to see you finish that last sentence. :-)

i am really sorry, don't know why it cut the answer, i was about to say that i would damage the 3d model with additional friction making it distorted


text:
What is the easiest way to modify/resize an object inside a STL file?
I have this GoPro mount for a quadcopter as STL file. It looks as follows.

How do I modify it so that it is wider and longer by a few millimeters but the screw holes stay the exact same size? Additionally the angle of the upper surface must stay the same. Please suggest the easiest solution for someone like me who as no idea about CAD software.
The perfect solution for me would be to just import it in Tinkercad and then modify it however I have no idea what the steps are.

If you only need a few millimeters, you can probably just stretch/scale the entire model by the required amount in all directions (to maintain angles/proportions) and the screw holes will still be close enough to the correct size to work fine. You can do that kind of scaling in your slicer slicer without even changing the model file.

I have no idea which answer is the best. I ended up diving into Tinkercad, measuring everything and designing something similar (see http://www.thingiverse.com/thing:1624957).

Many resources are available for modification using 3D CAD (including learning a tool such as sketchup, which is VERY beginner friendly). The easiest and fastest solution to your particular problem may be the reddit community "3D Print My Thing" which was created for EXACTLY this type of situation (help with modelling parts which will be 3D printed.) Another potential useful reddit community is "3D Modelling" which will have many people who are able to help you with this quadcopter/Go-Pro attachment 3D model.
Third solution: Thingiverse has a customize option for 3D models (including this one). have you explored using this interface to edit the model? This is most likely the easiest DIY solution.

Unfortunately, there is no simple method for modifying specific features of an STL. You are pretty much limited to the following actions:

Scaling (The entire model along three independent axis)
Breaking the model into parts/chunks
Mirroring or Rotating the object
Skewing an object (twisting)

Even the last action requires a 3D CAD program. I would suggest you develop your own model. OpenSCAD is a free 3D CAD program that works well. If you are comfortable with TinkerCAD, you should be able to easily develop your own version of this mount.
Good luck!

I think what you are trying to do is somewhat non-trivial so whatever tool you choose there will be some learning curve.
OpenSCAD, as mentioned above, is pretty well established as an open source tool for modifying STLs; however you have to be comfortable writing programmatic CAD instead of using GUI tools.  Personally, I think programmatic CAD is MUCH easier but I realize not everyone feels that way.  FWIW, I would probably break this into three STLs using a DIFFERENCE method, stretch the outer ones using a SCALE method, then use a UNION to put them back together.
The one problem that I've had with OpenSCAD is that it will frequently crash unexpectedly or run incredibly slowly when dealing with an STL with a large number of triangles.
AtomicCompiler.com is very similar to OpenSCAD but runs as a web service and seems to do a bit better when dealing with large STLs.  I might try that first, as it doesn't require  a download or even a login.

Well. I would cut it into two STLs, using netfabb slice / split tool.
in 123d I would fill in the hole with the merge union (with a cylinder object), scale it, and either keep it unfilled and drill it, or do a subtraction union on where you want the holes. (again with a cylinder)
Scaling otherwise you need the original model and solidworks..
Split in 2, scale the piece you want and re-add the other half is probably the best way.

I would suggest using Blender for this purpose. It has excellent selection tools, you can undo/redo selection and obviously you can resize any portion without affecting the others. However, you may need to learn Blender to an intermediate level to be able to effectively do that.

By far the easiest program to use is Tinkercad and it's free.

Hi welcome to 3DPrinting.SE! Thanks for your answer but we are looking for comprehensive answers that provide some explanation and context. Very short answers cannot do this, so please [edit] your answer to explain how you would do that in the referenced tool. Additionally, we prefer answers to be self contained where possible. If you add more context and detail, it is more likely that people will find your answer useful.

This really doesn't answer the question. How does it explain resizing/modifying an object? Explain how to modify/resize in TInkercad, if that is your preferred application. Otherwise, this answer should be considered just SPAM and deleted.

I've tried many tools, and many ways. The easiest way I found was to use Blender as previously mention.
A good (and fast) tutorial to expand pieces without stretching them is

Welcome to 3D Printing! Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference.

I like to use Slic3r for simplest slicing and rearranging operations.


text:
How to connect filament end-to-end?
Is it possible to connect two pieces of 1.75 mm filament end to end, with no change in width? I am asking the question because I am interested in creating a multi-filament feeder to a single extruder, and I am curious about the process of changing filament while the 3-d printer extruder continues uninterrupted. My current best-guess at the optimal solution is to someone 'cut' one end of the filament and 'melt' it to the end of another filament.

You'd have to ensure that the joining portion of the two filaments do not "bloom" or increase in diameter, which would happen if unconstrained at the melting and joining time. Alignment is also critical, otherwise you have a varying diameter from one color to the next at the point of join.
There's an item on ebay which is precision drilled and has precision machined mating surfaces to ensure alignment of the filament. The filament is extended through the two components, heated (in the case of the video, with a match) and the two metal parts are pushed together. The joining of the metal parts also cuts away the excess bulge of the melted filament, ensuring correct diameter.
In the case of the above item, the joining devices have to be threaded with the filament prior to the joining process and then have to be threaded off the filament by pushing them the entire length of the filament.
This would be okay if one were joining short lengths only. Consider how much fun it isn't to have to slide these two pieces over an entire full spool of filament.
A split device which would enable one to un-latch or otherwise open a clamshell to release the filament would require much more challenging machining to achieve the necessary precision, which is probably why we don't see such a product.

There is a device which can do what fred_dot_u describes in his otherwise explanatorily good answer: the easywelder, made by I3D Inno.
It fixes the filament in a separate part so that the faces are adjoined perpendicularly and then heats the joint electrically with a device that at first sight reminds me of a hair straightening iron.
I am not sure about the joint quality this machine produces, but I am skeptical whether the it is good enough for high accuracy 3d printing. Especially if you take the history of the device into account (he wanted to create a custom O-ring from Ninjaflex), which the inventor shortly describes on this instructable: http://www.instructables.com/id/Welding-tool-for-plastic-filaments

Here is a neat method I came up with:
- cut both ends diagonally
- insert them in a piece of heat-shrink tubing, making sure the diagonal cuts overlap
- protect everything but the overlap with Kapton tape
- heat the overlap with a heat gun.
- you will need to monitor and experiment with the temperature. too much heat will deform and bubble the filament, too less heat will  result in a poor join
- use a multimiter with temperature probe.
How it works ?
The heat shrink tubing encloses the filament ends and also pushes them together when it shrinks. The diagonal cuts increase the joint area. Results are super strong and seamless joints. You might need to do a little sanding until you establish the right temperature for your setup.
I made a video how to do it :
https://youtu.be/eJeU9lXiQPE

Rather than just posting a video link, it is better to describe answer and provide the link for more detail on the technique.

Nice method but it takes so much time it doesn't seem worth it to spare a few meters of filament. Time is money :-)

I haven't tried this but it is something I have thought about. The simplest way to try this that I could think of was to try cutting the ends flat and then using a soldering iron or just the printers printing nozzle to melt the ends and then quickly press them together, then you could sand the filamelt to try and clean up the join.
I think what would work better than trying to get the width perfect would be to make sure your printer is doing infill when it hits the join so over or under extrusion wont matter as much or have the printer move to the side of the print and extrude in thin air while getting past the join. I have done this when swapping filaments during a print by pausing the printer, and changing the filament.

idea is good and i know for sure many are working on it but if you want this to work smoothly you may need to fix the device (that is joining two filaments) somewhere near your cutter assembly (if any)arranged to cut the filament...this is the another way to perform the task automatically but you can do it separately with devices available to cut and join the two filaments together.
links below:
http://diy3dprinting.blogspot.in/2014/07/fuse-clamp-filament-welding-device-for.html

Please describe the process rather than linking it, links can become broken and information lost.  Links are fine as long as you describe the process here.  Right now I have no idea what your answer says.