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How do I determine the acceleration value for my printer?
When the print head changes direction, the printer must accelerate and decelerate the print head. When calibrated correctly, the printer is able to do this quickly and without causing the printer to shake too much, without drastically slowing down the print process.
If I set it too high, my printer shakes violently, especially during infill. If I set it too low, print times are doubled or tripled.
What process can I follow to determine (or how can I calculate) the fastest acceleration value my printer can use without causing problems in my print?
I'd prefer a process I can follow over a formula I can plug values into, especially if the formula includes magic numbers.

Binary search, i.e. trying values until you find one that works.

As Tom pointed out, binary search is the best way. In case that term isn't familiar to all readers, here's a little more detail:

Establish an acceleration value that you're sure is too low (call it $L$), and one that you're sure is too high ($H$). It sounds like you know such values already from experience.
Figure out the speed in the middle: $(L+H)/2$.  Call that $M$.
Try printing at speed $M$. Something like a stepped calibration cube might be a good choice of object (plenty available on Thingiverse).
If $M$ is still too fast, take $M$ as your new high-speed limit (that is, reset $H$ to the value of $M$), and repeat from step #2.
If it's slow enough to work, take $M$ as your new low-speed limit ($L$), and repeat from step #2.

Each repetition will cut the range in half. Keep repeating until $L$ and $H$ get as close as you want; say, within 5 % of each other or so.
I wouldn't bother trying to get super-close, because the workable value will vary somewhat over time (friction from dust getting on various parts; slight voltage differences; different mass and pulling tension for the filament roll, temperature of motors, complexity of the object you're printing, behavior of the slicing program you use, you name it).

That seems like an interesting calibration method! Is there somewhere I can read more about this?

It's a very common method for searching in computer programs. Look up "binary search" and you'll find lots of information. I don't know of any good references on using it for hardware optimization in particular.

A tool that you might find useful for experimenting with acceleration is RepRap Centrals Acceleration Calculator (at the bottom).
By setting an acceleration, length of travel and target speed, you can see:

The theoretical speed that can be achieved during the travel with your set acceleration (yellow line).
The distance required to reach your target speed, and for how long it will hold that speed before slowing down (blue line).

For instance, setting acceleration = 3000, length = 30 and speed = 150 means it will travel 4 mm before reaching its desired speed of 150 mm/s, while that same acceleration theoretically could give a speed of 300 mm/s for the given distance:

Calculating speed, acceleration and jerk:
In many cases your printer will have some limitation in maximum speed or settings given by your provider that can be used as a starting point. If not, trial and error is the most straightforward way of doing it.
I would separate speed calibration into three task:

First find the maximum speed your printer can tolerate. One way of doing this is to print an object with long travel distances, and vary the maximum travel speed.
Using the calculator above, increase the acceleration for various traveling distances until you get suitably smooth acceleration curves for your desired speed for medium to long traveling distances.
Adjust your jerk setting to allow for quick speedup on short traveling distances. Jerk speed is the speed that the printer will immediately jump to before taking acceleration into account. With a jerk of 20mm/s, the printer will make an immediate jump from 0 to 20 mm/s, and thereafter speed up to the desired speed by following the acceleration profile.

As a rule of thumb, it might be smart to then set the actual speed, jerk and acceleration approximately 20% below the the maximum found as a safeguard when printing.
Also, bear in mind that the strength of stepper motors lowers for higher speeds, so that the nozzle will not hold its path very well if obstructed. If this becomes a problem, consider lowering the speed.

Excellent last point -- my printer has a big Y-axis (1200mm), so lots of inertia. I had to run the stepper very slow for it to have enough torque to turn the leadscrew at all. I switched to a "5-start" lead screw (so it spins 1/5 as fast for the same motion), and no more problems.

@TextGeek Thanks! This is the kind of thing you figure out the hard way. My introduction to the stepper motor strength curve was that very minor defects due to leveling the bed too close would push the nozzle off its path during high speed travels.

I do not completely understand how you get to the number of 'somewhat less than 5 seconds'. The calculator should show length on the x-axis and the acceleration could theoretically give a speed of 300 mm/s, on a length of 30 mm as given by you while taking into account that the printer has to accelerate and deaccelerate by the given 3000 mm/s^2.
Do I see this correctly? Otherwise excellent answer!

@kamuro, excellent question! I added an image where I have highlighted the info. Notice where the green line intersects the x-axis (at approximately 4 seconds). :-)

But it cannot be coincidence that the x-axis of the graph scales with field 'distance or axis length', can it?

@kamuro, I think you are absolutely right. The x-axis has to be the distance travelled, and not the time. Then, the green line would mean it takes 4 mm to reach the desired speed, and not seconds. Now that I think about it, 4 seconds is a tremendously long time for a stepper motor to speed up. :-) I have updated the image/explanation.

Most printers use between 2000 and 5000 mm/s2.... extrusion moves are usually 2000 (on average, between different printers), travel is normally seen at 3000-5000, though for most lower end or duel direct drive extruder (heavy) printers, this value should be lower (some as low as 500-1000, some as high as 2000 for travel). Heavier extruders need lower values, as well a slower jerk values, to avoid the motors skipping. The jerk setting being set lower can actually be beneficial, as this makes for smoother extrusion after a corner or a hole (some people will see ripples near these areas as it accelerates out of the direction change - lower values make these ripples smaller, but slightly increase print time).
I've just modified mine with a prototype carriage design that I'm working on. It's added about 100 grams to the stock weight. It was finely tuned before, so this extra weight set it over that pillow of 20-30% in the setting, and makes the X and Y skip as it jerks around the plate; especially in high resolution models, particularly high resolution circles with 200 faces on the vertical axis, because the printer tries to jerk after each node - normally that isn't an issue, but in heavy designs, the jerk setting needs to be lowered. I had my jerk at 20 for XY, and its now at 4, after having tested and failed 8 and 15 values. The acceleration was at 2000 for both extrusion and travel (some firmwares don't allow separate values for travel and extrusion moves, but if yours does, it's best to have travel value about double the print moves - when your travel is twice the speed of extrusion moves - so use that 1-1 formula in relation to speed, scale it for each desired speed set in the slicer). Mine has been tested at 2000, 1500, 1000, and 800, failing all of them, with jerk setting of 5. Now testing 500 for acceleration, and beginning to get a little confused as to why this is happening.
Now I'm having second thoughts... After going as low as 800 from 2000, and still getting skipping (seemingly worse) am I getting this backwards here? Do I need a higher value if the motor is skipping on quick moves? My understanding is that lower is better for those problems, but perhaps I've confused myself.

Hi and welcome to SE 3D Printing. Your answer, whilst informative, seems to include a question. It would be better to ask your own question (using the link at the top of the page), as this is a Q&A site, not a "threaded forum". You could always link back to this answer, in order to maintain the context of your query.


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How do I keep my extruder head from getting clogged?
Using a thermoplastic MDF printer with a 0.4mm extruder nozzle, I frequently have trouble with the nozzle getting clogged.
I am not sure what's causing the clog, but my guesses are dust and/or burnt filament (from leaving the hot end on without extruding).
What can I do to prevent, or at least minimize, the extruder nozzle getting clogged?
Bonus question: What other common causes of clogs are there? (ie what should I watch out for besides dust and leaving the hot end on?)

Perhaps include the brand/make of hotend, printing temperature, type of material and color?

Hello @Martin Carney, I noticed your question has been up for a while now. Have any of the answers below been able to solve your question? If so, would you mind accepting the appropriate answer. If not, what is missing so that we may help you further? Also, if you have figured it out on your own, you can always answer and accept your own solution. Thank you.

Different types of hotends and extruders can lead to different problems associated with clogging. Based on my personal experience the leading causes of clogs and jams are the following

Foreign material in the nozzle (dirt, dust, low quality filament)
Mixing materials in the hotend (running ABS at 220 then switching to PLA without purging the nozzle)
Excessive retraction or "heat soak" in PLA (PLA expands when heated if your retraction is set to high you can actually push the expanded PLA high enough that it cools down and can no longer flow)

To solve these issues I recommend using one type of filament, preferably decent quality (typically $40 per kg), if you swap materials be sure to completely purge your nozzle of the higher temperature material. Set your retraction as low as you can trying to minimize ooze (try .4 mm for all metal hotend or 2-3 mm for makerbot style). To minimize carbonized plastic in your hotend don't leave your hotend's heater on for extended periods of time. One way to keep dust from accumulating on your filament is to cover your rolls when you aren't using them, I personally use hairnets, you can buy a 12 pack for a couple of dollars and they last for a long time.

Lubricating the filament is the most common solution I've heard of to stop filament jams and clogs. Lubricating makes for a smoother ride through the print head. While you're at it, make sure that the filament is clean. The best way to stop jams from dust is to get rid of the dust in the first place.
Some people recommend canola oil, which I've heard works reasonably well for both ABS and PLA (though especially for PLA). You can even 3D-print dust filters/lubricators, if you think this could be a serious issue.
I personally try to clean the print head regularly, after every couple prints or even after each print, if I have time. Something sharp, like tweezers, can pick off bits of filament near the tip of the nozzle. I haven't tried other utensils yet, but there are certainly other tools that would work. I've also heard of people regulating temperature with a fan, in order to prevent partially melted bits of filament clogging up the inside of the nozzle, but I don't know if that's effective.
In some cases, the problem could even be as mundane as a support issue. I once set up a spool of filament, only to have a jam when the support for the spool failed, leaving the line of filament tugging at the nozzle and clogging it. Taking steps to prevent this from happening can be simply and effective. Whatever the cause, preventative measures are always my choice.

Does the oil not cause problems when it's heated along with the plastic? Or does it just get absorbed / mix in?

@MartinCarney I can cause problems if it's applied thickly. A very, very light coating should not affect the composition of the final product too much. In general, it gets mixed in.

As general advice, regardless of your printer, extruders tend to clog if:
[Some of them might not apply to every printer, but they should be as general as possible]

you let the filament run out mid print, most extruders have a "dead zone" between the grinding wheel and the hot end, in which if the filaments stays stuck there, your only option is to open the extruder
you let a filament create knots with no one present to readily fix the knots, or the grinding wheel will saw the filament, leading to (1) plus a clogged grinding wheel: more often than not the quality of a filament brand is measured by the presence or absence of knots.
you let the hot head stay hot without printing for too long, it will fill of melted filament leading to risk of it carbonizing inside the extruder, leading one again to (1)
you use flex or rubber material which have the added complexity of grinding against the common plastic guides of the filaments feeders: depending on the material used, you might decide to avoid using the guides and feeding the extruder directly
you print at higher qualities (e.g. 0.1 mm) leads to lower filament throughput that can become stuck if the nozzle is too wide (and the grinding wheel goes too fast)
you never clean (i.e. blowing will suffice) the grinding wheel: filament dust sticks there increasingly over time.
you let the extruder is too close to the plate: if the filament is not free to fall on plate as it should (settings-wise) it will fill the hot end back up leading to clogs
you print wood, brick and derivate filaments: they are highly unhealthy for the extruder since they are plastic/resin charged with wood powder. The powder tends to a) burn and b) stick to the internal walls of the extruder.

If I can think of more I will add them.

First, you don't.
To reduce the likelyhood, use good plastics without contaminations.
Do not over heat the plastic, causes faster carbon build up.
Buy hand drills, mini drills to clear it.
Don't switch materials around a lot. Low temp plastic residue will cook when you switch to high temp plastic. Again carbon.
Last will come to your extruder is self. Use a hardened extruder tip, less likely to wear. All metal should help a lot too, PTEF tubes often get baked in a jam situation.
Or do what I do. I use a giant 1mm nozzle. I have printed at least 20 lbs of plastic on the same nozzle.
The other solutions say put oil etc.. I will just say that is not a great idea. First you will have terrible bed adhesion, second it just seems wrong. Not to mention it will be out of the extruder within one KG?. The only time its okay to use oil is if you have a bowden setup.

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How can I best clean the print bed after a print?
I've occasionally had issues with excess filament residue getting stuck to the print bed. There are ways to prevent this, but sometimes even these precautions aren't enough. Over time, residue can build up. I've observed this in some printers, though not others.
Are there any techniques to best clean print beds? In the past, I've used various typical cleaning supplies, with different degrees of success. However, I don't know if this will lead to damage to the printer over time.
The printer I'm using has a glass print bed, which I occasionally partially cover with blue painter's tape during printing.

There are too many types of bed material (glass, aluminum, granite, ceramic, plastic, PEI, PET, specific manufacturer material, plastic, garolite, etc) with too many adhesion methods (Kapton, slurry, tape, glue, etc) to be able to answer this.

@tamarintech I narrowed it down to my situation,

If you are printing with ABS (or PLA), acetone will dissolve it.  Simply pour
some on the bed and wipe it off (beware, acetone can damage beds that have a coating or a plastic sheet over them, be sure to test this first).

Heating the bed back up may make the plastic softer and easier to
remove.

If you are using tape on the bed, you could remove the tape to remove
the plastic stuck to the tape.

So, acetone will not work if I'm using PLA?

After doing more research, I stand corrected.  Acetone will dissolve PLA, but it is less efficient that ABS.  It would also turn it white so it is not used for standard printing.  I will edit my answer.

As Eric Johnson says, Acetone will work with PLA, but I've had just as much success with hot soapy water and a sponge on my glass surface.

My usual solution for cleaning the glass bed on my printer is a glass scraper (basically just a razor blade with a handle on it):

Regardless of what kind of filament (abs/pla/nylon) or surface treatment (glue/painters tape/abs slurry) I've used the glass scraper always takes it right off, and with the style I posted a picture of the blade is flexible and thin enough it's also useful for peeling up the edge of prints that are stuck to the bed.

This and warm water should get you taken care of.

I have just now used this exact tool and managed to make a cut into the print bed itself. So a word of warning for everybody, be careful if going this way

When I print PLA on glass plate, I clean the glass with cold water and dishwashing liquid. Cold water! And no wipe! Cold water should take all dishwashing liquid "to the ground". Now you have glass as clean as possible. Now the filament sticks to the glass far better than when glass is not clean.
But of course it doesn't fix problem of cleaning HB after print. To reduce this  problem I use glue stick (paper glue). I don't know if it's common but I do like this technique.
So having clean glass I spread (grease) some glue stick. It doesn't really matter if HB is cold or hot. This gives me a VERY strong adhesive force between the extruded filament and the glass. It's so strong that there is almost no way to detache it by hand. I use a paper knife.
Now you still have thin layer of glue and you can print again / add another layer of glue (but not more than 2..3 times) or wash it with hot water. After few times it's good to clean it again with dishwashing liquid and cold water.
This technique is amazing.

I use hair spray directly on my glass bed , then just a  little bit of rubbing alcohol on a small piece of paper towel to clean it...that removes all surface materials... I don't use tape any more... Russ

Oh I should say that I use hair spray at the start of the print, and a bit of rubbing alcohol to lean it... Russ

I have a glass bed and I use plastic razor blades from Scraperite specifically black blade to clean it up. Looks like it's the best alternative to metal blade so far.

I use a razor blade scraper to get stuff off that is sticking.
Priory to printing I heat and level the build plate, then wipe it down with alcohol to get any greasey fingerprints off of it.
My Scraper

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My heated glass print bed keeps chipping and cracking. How can I prevent this?
My thermoplastic FDM printer has a heated bed and uses glass as the printing surface. Sometimes the glass will chip or break entirely when I'm removing my print. This happens most often when the print has a large area in contact with the glass.
What can I do to keep this from happening?

What kind of glass is your build plate made of?

What filaments are you experiencing this with most? What printer model? And what method are you using when trying to remove items from the glass buildplate?

@PostEpoch Mostly PLA, and a little ABS. The printer is a Zeni Kinetic Origin, which you haven't heard of because the company went bankrupt. To remove parts, I use a scraper to work between the glass and the print.

Again, the type of glass matters. 3mm borosilicate glass should be fine.

don't use metal on glass, it will cause it to break eventually. this is especially true of pyrex.

Some things I've tried that have helped:
Lay down a layer of masking tape. Most people who do this use blue painter's tape. The plastic should stick nicely during printing, yet release reasonably easily when you remove the print from the heated bed.
Lay down a later of Kapton tape. The principle is the same as masking tape, but Kapton tape has a smooth surface and is more durable than masking tape. The down side is Kapton tape is far more expensive, and applying it correctly is a LOT more work, since you have to use water and you have to keep bubbles from getting underneath it.
Put some ABS scraps into a bottle of Acetone, and allow the acetone to break down the ABS til you have a slurry. Spread this slurry as evenly as possible across the build plate, and allow the acetone to evaporate away. This leaves a thin film of ABS on the plate, and will release much better than if you print directly onto the build plate. I recommend using clear ABS if you can, since some of it will stick to your print and clear will be the least visible. You'll need to re-apply it regularly, since it will come off with your print where it touches the build plate. WARNING: Use proper ventilation and avoid contact with acetone. That stuff's not good for you. Also it's flammable, so keep a fire extinguisher nearby.
I prefer the ABS/acetone slurry method, but it requires good ventilation and a handy fire extinguisher. Also note that you don't have to print in ABS to use an ABS/acetone slurry; I print primarily in PLA and it makes no difference.
I've also heard of others using a glue stick or some other surface treatments that allow for good adhesion during printing while still allowing for easy removal.

You mention needing water for applying Kapton… I'm unfamiliar with this. Can you point me somewhere with more details on it? I just apply it very slowly, using a credit card to smooth down and prevent bubbles.

@DustinWheeler The first video tutorial when I google "applying kapton tape" uses this technique.

I don't think you really need a fire extinguisher for acetone, though one is recommended next a 3d printer. The way it burns is not that dangerous  also taking into acount what a thin layer you will be applying https://www.youtube.com/watch?v=ZJWhfpWlGFg

I use the glue stick method. I like to take my build plate out and put it in the freezer. The different coefficients of thermal expansion between the glass and plastic usually means that the part just pops off in the freezer.

You can try using a raft with a bottom that is not 100% solid.  Something with lines or crossing lines will lessen the contact area with the bed making it easier to remove.
Note: reducing the adhesion to the bed will make prints more likely to fail.

Richrap had a detailed blog post on this issue.
TLDR: Glass screen protectors (for ipads or other tablets) are wells suited to protect the glass from chipping.

While links can be useful, it is typically good practice to provide a short overview of what the link explains in the case of link rot. It is currently unclear that the link mentions glass screen protectors.

I have 2 suggestions.
First, get better glass. high quality borosilicate plate glass at least 3 mm thick should shrug off even scraping with a razor.
Second, don't scrape it with a razor, put the whole thing in the freezer (or fridge, or in front of a fan, wherever), borosilicate is known for having a very low thermal coefficient, so the plastic is going to shrink more than the glass and should pop right off

beforre cooling in freezer, let it cool to room temperature or you blow up bed after bed in thermal shock


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How thin can I make the wall of a pipe?
For a science project, I'm 3D-printing some custom pipes and tubes to regulate the flow of gas (a combination of ethyl alcohol and water vapor) through an apparatus. They need to be pretty small, as the entire experiment is designed on a small scale. I'd also like the use a little filament as possible.
How thin can I make the walls of these pipes and tubes before either they collapse or gas leaks out? I know that's possibly an engineering issue, but I'd also need to take resolution into consideration. Ideally, the pipes would be about two centimeters in diameter, possibly a little larger or a little smaller in some parts. I'd most likely use ABS, but PLA is my backup in case there's some unforeseen reaction between the gas and the pipes.
The printer I'm using is an FDM printer, a version of the MakerBot Replicator.

What type of printer are we talking about? I suspect from the context (ABS and PLA) it's an FDM machine, but your question doesn't rule out a hypothetical PLA laser sintering machine.

@TomvanderZanden Ah, yes, it is an FDM machine. I'll specify that.

This might be a question that'd be better answered on the Engineering SO site, where you're more likely to find users with the specific expertise needed to answer a question like this.

@Jeff Good point. I made it a bit clearer that I'm also concerned about printer resolution, but primarily the strength of the filament.

@Jeff I don't think that's the case. Thin walled cylinders present some unique issues with 3D printing.

The thinnest wall your printer can print is determined by its nozzle size, and will be a little thicker than that nozzle size.
A great challenge when dealing with thin, hollow cylinders is that the cross-section has very little surface area and it can delaminate easily, especially if the tube is long.
You could try printing the tube with a very thick extrusion with, and using only a single perimeter. That would give better gas-tightness and layer adhesion than two, thinner perimeters, but it may turn out too fragile for your application. In that case, you'll need to print additional perimeters. Sticking to thicker extrusion widths would still be beneficial.
At a two centimeter diameter I'd say the single perimeter has a decent chance of working if you handle them gingerly.

The thinnest possible will be a single outline, so the best you can possibly do is slightly larger than your nozzle size.
The biggest issues I see in terms of making a thin airtight tubes are:

Complex geometry: anywhere you have overhangs you may need to increase the wall thickness to ensure a sealed overlap.  Bridging will need extra layers to ensure good layer adhesion and any supports will have to be removed carefully to not damage the surface.
Perimeter start/end: The joint where the perimeter starts/ends not only has to seal to the layer below but it has to seal with the now cooling start point.  This could be especially problematic if all of your layers are started at the same point (which visually produces a vertical seam) because you don't have a smooth perimeter on the previous layer and any imperfections in the joint are compounded.

Thoughts:

Print on end where possible: You'll get a higher quality outer perimeter if your layers are full rings instead of printing up both sides of a pipe on its side.
If you can manage a single perimeter when printing on end try using the "spiral vase" setting, which will smoothly raise the z position and print as a spiral instead of printing discrete layers.  This removes any issues related to sealing the start/end of a perimeter.
If you're printing with multiple perimeters increment the wall thickness in multiples of the nozzle size to ensure the perimeters are sealed together.  Having the perimeters not bound together increases the chance of leaks and reduces stiffness.
Do the pipes have to have the same thickness all along them?  You can probably reduce thickness to save material for simple geometry (straight sections) if you change thickness gently.

When printing thin cylinders vertically,

Slow print speed, to avoid rocking the model.
no shells, just one nozzle thick, so you don't need fill.  Fill can easily rock the print.
Print at least 2 at a time at the smallest layer thickness you can do.  This causes the hot end to have to move away from one cylinder to get to the next.  This gives each cylinder layer some extra time too cool and harden before the next layer goes on.  I generally print .1 or .05 for cylinders.
Your slicer may have a setting that tells it to wait between layers so the plastic has more time to cool.   I think the setting is called ORBIT on mine.

Consider following up with an acetone vapor bath to help seal the pores in the print.

This is difficult to give a definitive answer, but I have some thoughts.
For a vertical wall, the minimum thickness is determined by your nozzle size, typically 0.4mm. If you are able to print entirely in a vertical orientation (a pipe standing on end), you may consider using "vase mode" with no top or bottom to print. This can help simplify the CAD modeling, as you don't have to model the hollow interior and wall thickness.
For a horizontal wall, in theory this could be a single layer height, about 0.1mm depending on the printer and settings. Realistically, you will probably need 2 to 4 layers to get something "solid". However, this is not likely to have good results for a hollow pipe due to performance of the printer in bridging and overhangs. A thin, round pipe laying on its side is not likely to be successfully printable.
For printing in a horizontal orientation, I'd recommend a non-circular shape; the specific shape would depend on your overall design and goals. A "teardrop" or "flat teardrop shape can help with horizontal holes through parts.
Also, rather than individual pipes, perhaps you could design a block with hollow passages. This could allow thicker walls, make it much stronger, reduce assembly needs, allow for extremely complex routing and internal connections, and may even allow for functional parts like valves or sensors to be installed.
Finally, I would not expect an FDM-printed part to be airtight. There will most likely be some small gaps between layers and where layers start and stop. As an example, I tried making an ice mold, but almost all the water seeped through before it froze.
Another poster recommended an acetone vapor bath, which should help seal any pores. This only works with ABS. Another idea might be to coat the inner surfaces of the pipes with a resin that can seal everything up.


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How do I set the G-code buffer size on Marlin?
I am reconfiguring a Printrbot Simple Metal that has been retrofitted with a RAMPS+Arduino Mega running Marlin, with a fairly slow feedrate due to mechanical and quality limitations.
I am finding that upon cancelling a print where something goes wrong, I have a long period of time in which the printer is continuing to print from the G-code and movement buffer, although the host software (Octoprint) has long stopped sending G-code.
Is there a way I can either a) configure Marlin to have a smaller print buffer (since Octoprint has no trouble keeping up with the printer as it stands) or b) send a particular signal or G-code to the printer that stops it without continuing to read buffer contents?

Matt: Thanks for the edit suggestion. I rejected it for now since this question isn't Printrbot-specific. It is applicable to almost any Marlin-based printer, that happened to be a Printrbot in this case. If you still feel it's a necessary tag, please resubmit the edit and I'll approve it, or let me know by comment.

Marlin does allow one to change the size of the buffers, in Configuration_adv.h. In the current version there's an ifdef that switches between two cases, one with SD support, and the other without. Both have a movement planner of size 16, which can be adjusted.
Additionally, in the same file, BUFSIZE can be changed to modify the size of the buffer storing unparsed commands before they are parsed and enter the movement planner buffer.
Additionally, for some firmwares, M112 will immediately shut down the printer, no matter what is in the buffer, but the reset button will need to be used, and the axes will not be homed afterward. In Marlin, it's hardcoded to call kill().


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How should I clean my extruder when changing materials?
I often switch my print material, i.e. ABS / PLA / Wood / Flex,
How can I best clean out my extruder between them to ensure I don't contaminate my next print?

I would be particularly interested with materials such as PVA, where temperatures over a certain point carbonize the filament, all but destroying the hotend. How do you switch from PVA to ABS, with the huge temperature gap?

If you feel you need to clean the nozzle the best approach is a cold pull.  You can perform this procedure with many printers, however, you should seek advice from your printer manufacturer before attempting this process if you have any doubts.
With the previously filament still loaded and the tool head cold:

Begin to raise the temperature of the tool to the printing temperature of the next filament you intend to load
As it begins to warm up perform any tasks you normally perform during filament unloading (open the idler, for example). You should not be fighting against the extruder drive gear or any other part of the tool during this process!
With a fair amount of pressure begin pulling on the filament
The old filament should eventually release from inside of the tool leaving the end of the filament roughly in a nice molded shape of the inside of the tool.  Begin loading the next filament you intend to print and manually feed some filament through as the tool finishes heating

Anything left over from the previous filament including pigment or other residue should be stuck to the end of the filament.
You can perform cold pulls as many times as you wish by loading new filament, extruding a small amount, letting it completely cool and repeating the steps.

I typically perform cold pulls on the filament I unload by manually (by hand) pulling the filament back with a temperature setting slightly lower than typical printing temperature. Due to the lower temperature, most residual filament will stick to the filament on the way out.

Great advice.
Like the instructions, I usually just set the temperature and begin pulling while it's cold.  As the temperature rises the filament will generally come loose much earlier than when the printing temperature is reached.  I then load the next filament and feed some through by hand when it reaches printing temperature. :)

In most cases, removing the old filament from the printer, inserting the new filament in, and running the new filament through the printer for a short period of time will clean the nozzle.  The skirt of the print can also be a time during the actual print for the old filament to be flushed.  Assuming the skirt is long enough, all that needs to be done is the new filament inserted and the print started.
Assuming that extruding new filament does not fix the problem, there is a more serious problem such as a clogged extrusion head that needs to be fixed with other methods.

Some people use a nylon "cleaning" filament when switching types of filaments. It heats well to a variety of temperatures and seems to stick well to whatever is in there when pulling it back out. Be sure to heat it up to the temperature of the filament being removed to get that to bind with the nylon.

I always find the best way is to run more filament through the nozzle.  Just enough for a full colour change.

eSun has a cleaning filament that extrudes at a wide range of temperatures.  It may seem ridiculous to use filament that costs over $100 USD per kilo to purge the nozzle, but it's very convenient and in practice, you don't use much each time (it's sold in 100g packs).  I'm still using some samples I received with some filament over a year ago.
Cold pulls will probably be more effective though (as described in another answer), they're just more effort.  I usually use cold pulls with nylon when I want to clear out my nozzle, either as part of routine maintenance or when switching to plastics that are sensitive to contamination (usually PETG or ninjaflex).  I usually use the cleaning filament when I want to change from a dark to a light or clear filament, especially if the new filament is expensive.  Most of the time I just feed in enough of the new filament to purge out the old, with the temperature set to the max of the two.

The question then becomes: "how do I clean the nozzle from the cleaning filament?" :)


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Bulging filaments - How can catch them before they go in the printer
After multiple jams from bulging filaments on two spools I'm getting frustrated.  One, right before a job was done.
Is there something I can do to prevent these bulges in filaments from ruining jobs?
What can I do to prevent this from happening in the future before it's a disaster?
He's a picture of one I found using google.

What are you looking for in an answer? Do you reckon there is a better way than painstakinly physically inspecting the filament or just buying better quality filament to begin with?

I'm not sure what you don't understand. I have two questions in the post.  I can put them in here I guess.   Is there something I can do to prevent these bulges in filaments from ruining jobs?
What can I do to prevent this from happening in the future before it's a disaster?

That's my picture :-)
I use a filament monitor with an encoder wheel that pauses the print if the filament stops moving (because a bulge got stuck, or filament ran out, or the hot end jammed, or whatever). I have a bunch of these on multiple printers: http://www.toybuilderlabs.com/products/tunell-3d-printer-filament-monitor
The Tunell monitor works with Sailfish, Marlin, and Smoothie to my knowledge. This particular one doesn't work with Repetier, but you can wire up a simple encoder wheel to use Repetier's filament monitor functionality.
Like other people have mentioned, you should avoid cheap filament, and return spools with bulges. I personally only see bulges like that maybe every 20 spools or less.

I couldn't get a good picture so pulled one off google.   :-) hope your ok with that.

No worries! Link to the original post if anyone wants it: https://plus.google.com/114722716901025057698/posts/aioDrYXYe3J

That's why "The Google" has it.  :-)  I understand now.

How to catch and fix these on the fly? That would be difficult..
But this is an issue you really should not have.
Could it be an issue with filament storage?
Or is it coming from the manufacturer with these bulges? If so, I would try contacting ( you may have gotten a bad batch? ), or finding a new retailer if this happens often.
I have gone through a lot of pounds of both ABS and PLA and never come across this.

I agree. I have never seen this myself.

I can't determine where the incident occurs.  In the supply chain?  With my friends kid running around like a banshee?  Who knows.  I've just had it happen to me twice.  A bit frustrating.

Short of doing a bare eye inspection, or rolling out and rewrapping every single roll, I don't see how these could easily be detected when you first get them. My best suggestion would to get a plasticware tote and keep all of your filament in there. This will prevent them for getting moisture damage, and potential damage from being moved around often; if you keep seeing these, make note of on which filament, if they all came from the same place, or were all port of the same order, I would be contacting them for a refund / replacement.

Bottom line: The easiest way to prevent this is to avoid cheap filament.
You can get mid-grade filament for a few dollars more than the ultra cheap stuff.
In other words I tried out some 10$ stuff from ebay, and while it might print for a little while it notoriously clogged in any prints greater than 1hr.
20-25$ is the going rate for mid-grade filament on amazon and check the reviews I've had good consistency there.

There's a distinct possibility that something physical happened after I purchased it and it got into my hands.  I don't have 24/7 surveillance on them.  I know it's not my labrador because it didn't have teeth marks anywhere.  Other than that, it's a mystery.   :-)

@Citizen could have been the humidity in the air too.  I don't remember what all filaments are sensitive to that, but some are.

@BrainSlugs83 maybe the Labrador was standing there breathing on it. My dog stands and sniffs this stuff for as long as we let her ...

There is a filament width sensor design at http://www.thingiverse.com/thing:454584 -- cleverly, the author tweaked Marlin so it adjusts extrusion in real time to correct for variations.
That said, I agree with several others that buying filament with better quality control, and keeping it dry and unchewed by Labradors, should be enough. :)


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Issue with weird heated bed temperature fluctuations
I have a strange issue with my heated bed. It has been working well for a long time, but recently it has developed an issue where the temperature reported by the thermistor will occasionally jump by around 10 degrees.

My setup is a 600W, 240V silicone heater mat, with integrated 100k thermistor, that is switched with a solid state relay. The mat is fixed to a 4mm thick aluminium plate. It seems unlikely that these fluctuations are due to bad PID tuning since the reported temperature changes much more quickly than is physically possible.
I've checked the wiring, tried using a different thermistor port and making sure the connector was properly plugged in, but to no avail. The fluctuations are brief enough that they don't cause any problems when printing, but I'm worried about the issue getting worse.
I have a RAMBo board 1.1b, and I've tried using both the integrated 5V SMPS supply and an external USB supply.
The issue is not limited to the start of printing, the temperature reported can be stable for a long time before the issue pops up. The issue also occurs during cooldown (further confirming that PID has nothing to do with it):

In fact, the issue seems slightly more common during heat up and cool down, but is not limited to these times.
I would like to know what might be causing this issue, and if there's a way to solve it without replacing the thermistor (which would be a pain, since it's integrated into the heater mat).

Do you have a cooling fan installed that potentially could change speed mid-print and cool the bed in the process?

I don't, and it seems unlikely that a cooling fan could make the temperature jump up by 10 degrees in a matter of seconds.

You are probably right about that, Tom. Could it be that the actual temperature sensor attached to the bed is exposed to cooling? And btw, what is the time scale on the x-axis of the graphs you are have posted?

I would be concerned about the routing of wires within and outside the heating pad.  Perhaps there is inductive or other coupling between the thermistor wire and the 240V supply for the bed?

@hexafraction Yes, I'm worried about interference, the thermistor cable runs right next to the power wires and also right next to stepper motor wires. However, the issue also occurs when the bed is cooling down after a print, when those cables are not in use.

Forgive me if this is a naive question, but: I don't suppose your printer is on a circuit with a lot of other power-heavy appliances? I've seen weird spikes and drops in my bed and/or extruder temperatures when someone is, say, ironing during one of my prints on the same circuit as my printer. You'd likely see variations in both extruder and bed temp, though...

It really looks like either a bad thermistor or bad electrical joints. Are the connections to the thermistor itself crimped, or soldered? Are there connectors near the thermistor that can get heated up by the bed?
Electrical connections that are mechanical in nature (such as crimped, or using a connector) can degrade quickly in heated situations, particularly when the heating is intermittent.  Consider replacing crimped connections with soldered joints where possible, and where not possible use gold plated connectors and crimps to avoid oxidation issues. Oxidation and poor mechanical connections will change resistance based on movement, giving you apparent increases or decreases in sensor readings even when the sensor output is unchanged.
Chances are good that the thermistor itself is fine, but that the connection nearest the thermistor, between the wires and the thermistor, is faulty. If it's crimped, you may be able to simply add flux, then solder it to increase the bonding between the wires and the thermistor and decrease future issues with oxidation.
Note that soldering is really only useful for the thermistor on the bed.  The head thermistor must be crimped, as the head temperatures can exceed solder temperatures depending on the target temperature and the solder alloy.

It sounds like EM interference to me, though Adam's points about connections are also a good bet. I would try re-routing the thermistor wires far away from other wires. If that helps, then either leave them re-routed, or shield them. In any case, please let us know what you find.

From the decay curve of the temperature graph, it appears that the firmware is filtering the temperature signal.  Since it jumps up so quickly, I suspect that the thermister is indicating a much higher than 10-degree temperature change, but after filtering the result is a ten-degree change.
If the problem were a bad connection to the typical thermistor, the temperature would appear to be much lower, not much higher.
An electrical fault that would cause a typical negative temperature coefficient thermistor to indicate an intermittent high temperature could be a short circuit or some other condition that could cause 0 voltage across the thermister.
Your circuitry may be different, but I would suggest that several circuits I've seen on 3D printers to sense temperature have one side of the thermistor connected to ground, with the other side connected both to a pull-up resistor to Vcc (+5 or +3.3 depending on the electronics) and to an analog input which samples (measures) the voltage.  If the powered thermistor line shorts to ground anywhere, it will show 0 volts.  If the pull-up resistor is disconnected from the power source, it will show 0 volts.  If either thermistor line has extra connection resistance or has a bad connection, the voltage will be closer to Vcc than it should be.
You could check this possibility by connecting a voltmeter or oscilloscope to the non-grounded thermister line, and then monitoring the voltage.  The voltage should always appear to smoothly change (limited by the thermal physics of the bed. Try moving the bed and/or head through the range.  Try tapping the bed, cables, and electronics while looking for a change.  Any sudden change indicated a connection problem.  The voltage going up indicates an open circuit to the thermistor.  The voltage going down indicates a short.

So it seems it's neither the PID, nor the outside wiring. It also seems unreasonable that these temperature jumps reflect reality (too quick both up and down).
You say that you have a heater mat with:

with integrated 100k thermistor

This seems to be a thing you haven't checked out, if it's broken / got its wires pulled out a bit, it could explain these jumps in temperature.
Try using another thermistor, at least to see if those temperature jumps occurs with it or not.
HTH


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Marlin menu navigation slow while printing
My Kossel Mini printer (delta) has RAMPS1.4/Arduino Mega electronics configured to use a standard 20x4 LCD display with Marlin during printing.
Often, navigating the menus during print can be painfully slow, and I occasionally end up making the wrong selections due to lag.
Without starving the actual printing process of CPU resources, is there any way of speeding up the menu navigation?

What speed are you printing at? If I understand correctly, Marlin's interrupt frequency for stepping is based on the print speed (more correctly the necessary steps per second).

@hexafraction I don't think the interrupts are the problem, as they're very fast. The problem is that the planner is simply very slow, because delta's require complex arithmetic.

@TomvanderZanden Ah, I didn't realize Kossel is a delta. I should have googled first.

@hexafraction I added "delta" to the description so that you don't have to google next time. :)

@TomvanderZanden, are you suggesting that it could be is the path planning algorithm that occasionally require too much processing? In that case, I believe the menus would be slower for complex movements, such as circles or polynomial paths. I will investigate that tonight, but I believe you might be right about that.

@TormodHaugene No. Even a straight line is "complex" for a delta to print, because straight lines do not correspond to linear movement of the carriages.

@TomvanderZanden, you are right, of course. My bad. If I remember my radial math correctly, I believe it rather would be the other way around...

A Delta printer requires constant complex calculations to produce straight lines while printing.  The firmware, therefore, spends most of its time figuring out the step and timing sequence, and only the little remaining time between interrupts and these calculations is given to the user interface.
Marlin doesn't document any configuration parameters that would improve the user interface responsiveness, and in any case such improvement must necessarily come at the cost of printing speed and/or accuracy.  The processor is being used to its maximum capacity.  The only thing you might be able to do is dig into the firmware and try to change it yourself, as this is not a clear option within Marlin.
If working with the user interface while printing is important to you, your next step should probably be to change to a faster 32 bit processor. There are a few firmwares available for ARM and other architectures which may resolve your situation.

Thank you for taking your time with this. I have had this suspicion for some time, but not really known where to start. I don't think fiddling with the firmware really is the way to go, as that could be a huge time investment!  At some point I might upgrade the electronics, but for now I will just accept that it is somewhat slow at times.


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How to print an overhanging arc
I am designing a part that has to clamp around a 11mm bushing, and due to other design constraints, it has to be printed with a semicircle-shaped overhang:

This is proving very challenging to print. Two copies of this part have to clamp tightly around the bushing in all directions. Support material is rather hard to remove from the very top of the arc (where the overhang angle is the highest) and I often end up removing just too little of the support material (so the part doesn't fit around the bushing) or too much (and the bushing can wobble around).
Is there any way I can modify the design of this part (bearing in mind that it absolutely has to be printed in this orientation) to make it more tolerant of my inaccuracy when removing supports, or is there perhaps some way to manually design supports that are easier to remove (Simplify3D and Cura both don't quite cut it)?

Is it possible to print it laying down so that your arch is not built over open air? If not, why not?

@MattClark No, and the reason is not relevant to the question. The part shown here is oversimplified, the real part has additional geometry that makes printing in any other orientation impossible.

could you briefly explain why it has to be printed in exactly that orientation?

The part is under a lot of strain, if I printed it in a different orientation it would delaminate too easily. The scope of this question is only about possible ways to get this to print acceptably in this specific orientation, I do not care about any other solution. It might be possible to redesign the part to not require this orientation but I can just barely get a good enough print this way, so something that drastic isn't needed, but I'd still like to know if I could improve it without too much effort.

What does this additional geometry look like?

@thethirddimension It's irrelevant - please don't try to sidestep the question. It needs to be printed in this orientation, period. I might be suffering from the XY-problem, but I am generally just curious if there's a way to get this kind of geometry to print better than jus using supports. I am not interested in overhauling the entire part.

I wasn't really a fan of cura and I never used simplify3d, but Slic3r may solve some of your problems. Notably, setting interface layers to 2 or 3 will make it easier to remove support material.

You could modify it as shown in my picture.  I added lines tangent to the 11mm circle and in this example I set them to a 40 degree overhang which should be fine, the top line is also tangent to the circle and in my experience it's easier to bridge a small section rather than do a bunch of small overhangs like an arc would do.  You still end up with quite a bit of contact but also easy to print.
I did something similar to this on my printer where the smooth rods enter horizontal holes.

I think a lot of this depends on the slicing engine you're using as to what options you have. I use MakerWare (now MakerBot Desktop) which has many options for the support scaffolding as well as other useful settings for your situation. As someone else stated, adjusting the distance (even slightly) can make a world of difference in how easy the supports are removed. Also bear in mind that supports can be more difficult to remove with larger layer heights, so try printing in a lower layer height.
Often times, you shouldn't need to use support structures for a feature like this. I might suggest printing without supports at a reduced speed and lowered nozzle temperature. This will help ensure that the material hardens quicker, which becomes helpful higher along the arc.
Related to the suggestion above, you can focus your slicing setting on better bridging. This should give better control on feeds/speeds while "bridging" a gap between overhanging features. Some slicing engines allow you to specify a different layer height for these areas on the print.
So, I would try printing with reduced print speed, nozzle temperature(s), and layer height with supports. My machine has a range of 0.1mm to 0.3, but I've had more success printing between 0.12mm and 0.15mm layer height with scaffolding in mind.
Last suggestion (when absolutely all else fails) purchase some sort of dissolvable filament (ie PVA - water soluble) and set your scaffolding-to-part distance really close and print. Obviously this only works if you have a multi-extruder head or a lot of time on your hands to swap the materials and adjust the nozzle temperature for each layer (please don't do that...)

If your printer is printing support material that is too strongly attached, you can increase the space between the support and the part in some slicing softwares. On Cura it is located in the "expert settings" menu (you can open it by pressing Ctrl + E), under the "Support" text. Try fiddling with the "Z distance" setting until you find the right setting. You can also change the type of support and support infill amount and see if it have any positive or negative effect.
Edit : I think you should also redesign your part : it seems that it cannot lock the bushing on. The semicircle should be a bit smaller to have a bit of space between your two parts. This way the bushing will be secured firmly by the tightening force of the screws and precision should be less of an issue.

Thank you for your answer. Unfortunately, increasing separation distance means the overhang will sag more, rendering the part unusable. I'm specifically looking for ways to redesign this part to make it print better (bearing in mind this is the orientation it absolutely has to be printed in) or a way to create support manually (without letting the slicer do it) that will make it print better.

I believe the post by @tbm0115, covers many of the general options. However, I would also consider installing additional fans to improve cooling of the model during printing.
As pointed out by this excellent article, installing a fan can significantly reduce issues the from printing overhangs. Regarding the type of fan to get, they stated that:

It seems that the fan shroud you choose is less important than the fan type. The blower fan was consistently weighted above the stock 40 mm fan regardless of shroud. Using a blower also gives you the best possible airflow through any shroud you decide to use.

In addition - in my experience - adding having two or more fans blowing on the model from different directions will further improve overhang performance. This is because all parts of the print are less likely to experience lack of cooling due to wind shadow - or drag.

Is this true for materials other than PLA as well? I would think that materials such as ABS would be more prone to warping mid-print.

@tbm0115, Some materials benefit from active cooling, while others don't. I have not printed ABS much myself, but most advice points out that ABS should be printed with active cooling off. :-)

Here are all the ways I can think of:

Turn the temperature down just a little, which may reduce sagging
Crank up cooling, like bigger fan(s) aimed at the print, so it solidifies faster
Change orientation when possible (not in this case)
Use soluble support material, and wash it away afterwards (requires 2-head printer)
Pause the print as you go up, and insert support material manually (ick)
Omit support material at the very top
Machine out the support material afterwards with a more precise tool, like a drill or sander the same diameter as the bearing. I'm eagerly waiting for a BoxZY printer that can swap in a milling head in place of the extruder.
Remove support material as now, but if you remove too much, fill the gap after installing the bearing to prevent wobbling -- epoxy, hot-melt glue, melted PLA, etc. might work, depending on how the part will end up being used.
Add a set-screw to secure the bearing

Of course, these all have tradeoffs; but I hope at least one of them might help.
Steve

if I printed it in a different orientation it would delaminate too easily

If you flip it around, the orientation of the layers would be the same, except that you would print from top to bottom instead of bottom to top.
With the arch opening to the top, there would be no overhang. Without overhang, you don't need support structures (red). The holes for screw heads have flat roofs (green) that the printer should be able to gap by moving over them quickly.
Here's an image that shows the original orientation at the top and my proposed flipped orientation at the bottom. The blue lien is the print bed.

I had to design something rather like this, but I made the part that wraps around the pipe (pipe in my case - bushing in yours) into a separate piece that slotted into the main arch.
That way, the main arch could be printed with poor precision on the overhang, and the sleeve was printed on its side. It took a little work to make the slotting system fit well, but it was fine. The two arches screwed together to grip two sleeve sections. It also meant I could print the big parts quickly because their precision was less critical.
If - as you suggest - you absolutely have to print it this way, then how about pulling the top of the arch up a little; make it a bit "gothic" if you see what I mean. This is a variation on tjb1's idea above, but rather than have a flat at the top, organize it so there's a gentle point. That way, the printer isn't trying to draw a critical fitting over empty space, and the area that prints poorly is away from the bushing. You might have the slack to put supports back in.


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Can I mix ABS and PLA when recycling filament?
I'm thinking of recycling some filament from a couple of recently failed prints. I can reuse them in the future for basic prototypes, so I'm not concerned with whatever weird mixture of colors come out (they are of a few different colors).
The thing is, I have both PLA and ABS, in small quantities. I originally intended to simply use each one separately, but it occurred to me that they could be mixed.
If I recycle PLA and ABS together into one strand of filament, will there be any negative side effects (e.g. reduced strength)?

See also: What is PLA+

This is not a good idea. Both filaments have different melting points, that of ABS being much higher than that of PLA. To melt the ABS you have to heat the plastic to the point where the PLA starts to degrade.

While I agree it's not a good idea, I don't think it's completely improbable. I've had success in the past with printing ABS and PLA (separately) between 220-225C with no issues printing. In the end, if you combined the two materials, you would need to relearn what extrusion temperatures work for the new material. You'll probably lose a lot of the strength of ABS and rigidity in the PLA by combining them, however it would be a nice cheap alternative if you have a bunch of scrap material and need a simple knick-knack.

I think this answer is factually incorrect, since PLA won't degrade up to 250 °C and blends may print properly even when colder than the pure components, e.g. PC-ABS.  The difference in melting temperature PC and ABS is as big as PLA and ABS, yet they work. You may be right for other reasons, but the explanation you provide as basis for the answer is IMHO wrong. See my answer.

Simply put, PLA and ABS should not be mixed into a filament.
The most common issues most printers experience, such as delayering, warping, etc., are addressed completely differently based on the material you are working with. There are many examples of this, and I will attempt to go over some of the basic ones.
You will have extreme difficulty getting proper layer adhesion. Assuming you have a level, flat, semi-coarse (helps) surface for the first layer, the recommended heated bed temperature is 70C for PLA. With ABS, you will experience warping by the 5th layer at that temperature. ABS prefers 110C for a heated bed, and 80C for a heated chamber (personal experience for most reliable results).
Next issue is going to be delayering and stringing. There is no happy medium! Matter of fact, the number of issues even attempting this is almost too many to list. The quality will be complete garbage. On one hand you will have delayering, warping, and jamming of the ABS when set to PLA specs, and stringing, leaking, etc., when set to ABS specs.
I hope this helps.

PLA-ABS blends are known to be strong: https://www.terrafilum.com/products/composite/

Mix 'em, let us know how you go. You're unlikely to damage your printer, and you're only 'wasting' scrap.
I suspect that if you mix in small quantities of ABS (30% or less) you'll end up with a PLA mix similar to a 'wood' or 'metal' PLA filament.
To that end, recommend trying to print with PLA settings first, and going from there.
Make sure you let us know how you go, it'll be real interesting to see the results!

CNC Kitchen tested PLA up to 265 °C or 270 °C in a couple of videos, for example

The plastic (it may depend on the brand) holds just fine up to 250 °C, but (from personal experience) bridges become really difficult to tune. Strength is very good.
ABS can be printed properly starting from 235 °C (depending on the brand). At 235 °C layer adhesion may be suboptimal, but you are mixing it, so it's not obvious that the result will be poor.
So, to summarise you have a common range 235-250 °C where you can print both plastics properly when pure, so it is reasonable to think that by mixing them you will have at least the same temperature range (the bottom may even be extended a bit, as it happens with PC-ABS which prints properly colder than pure PC).
So I would say that it is a worth test with likely positive results.
In fact, ABS-PLA blends exist and are very good blends for industrial use as the Terrafilum site states:

ABS_PLA_Blend
Strong PLA Industrial Grade PLA with superior flow and
strength performance; designed for parts where PLA is desired but
where the parts will be subjected to repeated use; ideal for parts
that may need bend slightly without breaking during use.

If the amount of ABS is kept low, OP basically just reinvented generic-brand "PLA+". :-)

Or, OP also just re-created Tiertime PLA

First, I print ABS and PLA models.  I have accidentally printed PLA at ABS settings with absolutely no strange effects (being printed at 100 °C heat bed and 225-240 °C extruder temperature).  If the mixture is truly homogenized  together,  I do not see a problem  in mixing the two materials, however,  the cost of a recycler and winder are still cost prohibitive. Like the above poster said, experimenting would be necessary to get the settings right.
Technically, it should work .

Your model certainly must have deformed with such a hot bed underneath and nozzle above.  100°C is far above PLA's glass transition temperature, and I would also presume that if you are using an ABS profile your parts cooling fan is set to low or off, slowing the rate at which the hot plastic solidifies.

yes but you would have to experiment with the settings to see were it afectivly melts.


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Optimal ratio of fresh to used nylon powder
I am operating a laser sintering machine, using polyamide 2200 powder (with a grain size of approximately 50 micrometers). During a print, a lot of powder goes unsintered and can theoretically be reused. However, using purely recycled powder degrades print quality to an unacceptable level.
Mixing a little used powder into a larger amount of fresh powder seems to work well though. What is the greatest ratio of used to fresh powder that still gives good results, and is there anything I can do (pre- postprocessing) to allow more powder to be reused?

This site seems to be getting almost exclusively FDM questions, I thought it would be nice to have a question about a different type of process. Unfortunately I do not actually own a million dollar printer :-(

I noticed that your question has not had much activity lately, are you still looking for an answer to this question? How might we be able to close some gaps?

You'll find generally that mixing 40% new polyamide with 60% recycled polyamide will result in a reasonable finish and part. You will obviously want to use all new for parts requiring the best possible finish and mechanical properties, but this mixture will be very difficult to tell apart from a fully new mixture part:
http://www.paramountind.com/pdfs/eos_pa2200_mds.pdf
This is more detailed research showing how used powder changes and how that affects print quality here:
http://www.emeraldinsight.com/doi/abs/10.1108/13552540910960299
Searching for the research paper title may find a free source, but the linked resource does require a subscription or payment to that service.

I currently use the 60/40 recycling mix ratio and find that it works very well.  I do however wonder if there is an even more effective ratio in order to recycle used powder.  I currently discard all "cake" powder (powder remaining in the build piston) and am only "recycling" the push off powder.  I found this paper but it's unclear if they are reusing just the push off or both push off and cake.  Any further opinions/ideas would be greatly appreciated.
http://www.internationaljournalssrg.org/IJME/2015/Volume2-Issue7/IJME-V2I7P106.pdf


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How to minimize damage when removing an ABS print from a heated glass print bed?
Usually it will either will rip the tape, or break the print somehow. Currently using ABS on a taped glass bed with a layer of hairspray for adhesion.

After the glass cools throw it in the refridgerator. The print should pop off.

I moved to a plain glass heated bed with a brush applied acetone and ABS mixture. Using an old emptied nail polish bottle with brush, I added some acetone and then threw in ABS pieces until it reached a brush-able consistency. I then brush it on the glass build plate where I believe the print will occur, and it works very well. On removal of the part the coating comes with it.
I just found previously that ABS would adhere to my kapton taped heated bed too strongly to use, and so while this involves a little work before each print, it's overall better than kapton for me.
I did experiment with sheet metal beds coated with kapton, but they curl during printing due to the ABS thermal stress, allowing my parts to be concave on the bottom side. Easy to remove from the plate, though, since it flexed. There may be a good middle ground material but I didn't experiment further.

Any tips on part removal methods? Do you just lift it off or use a tool?

Most prints pull off without him too much trouble after they cool. Particularly solid prints with lots of bed surface area might require a little coaxing with a knife and perhaps a putty knife and some patience.

Might be worth to explain why such an "ABS slurry" works so well. Melted ABS merges with ABS well. But molten ABS doesn't stick to glass very well. However, if you create an ABS/acetone solution, it is far less viscous and can get in microscopic cracks and holes on the glass. Then the acetone will evaporate leaving the ABS layer which has "penetrated" the glass and pretty hard to come off. Since it's pure ABS now hot ABS comign out of the nozzle will stick to it well, but it is also better physically stuck to the bed too, so it won't lift like "regular" ABS layers do.

Hairspray on the other hand is more like glue, I think.

@LeoErvin many hairsprays are PVA based afaik.

I have had best results with ABS on a heated printbed
(untaped) with a thin coat of UHU Stic. It can be a little tricky to remove but minimizes damage.

UHU-Stick is a PVA based glue, which is also water soluble.

Glass has a very peculiar effect under heating, that can be used to remove extremely delicate parts from the surface of it:
Glass expands and shrinks differently to the ABS under temperature. Letting the glass bed cool down has it shrink, creating tension on the interface layer which can be exploited with a thin scraper. Putting the bed with the print into the fridge increases the tension to a point at which the bonding breaks. This results in the part popping free in several areas (sometimes everywhere) and easing the removal.

I'm not using ABS, but find that PLA parts printed on 60C bed with PEX coating glued on flexible steel are coming off pretty darn easy!  At 9:50 into this video, ABS was printed on a 125C bed, and after very little cooling of the flex steel sheet (on a metal table) the printed part came right off.  https://youtu.be/pSXgYwEcO6s  The Pex/flexsteel/magnet system is great.

@CrossRoads the question was about a heated glass bed with ABS. Your combination is different and has different treatment needs. However, yes, flex metal sheets (removable ones) are very helpful in removing, they use a similar effect than the glass bed in the fridge: breaking the bonds in a way that usually keeps stresses minimal.

Maybe my comment should have been: don't use glass, convert to something else!

@CrossRoads Glass has its benefits, for example being super flat.

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


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Does the material a bed is made out of affect the cooling time of a part?
Let's say I print a part out of ABS and wait for it to cool. I could theoretically do this with several copies of the same printer, modified to use print beds of different compositions.
Will the material a bed is made out of affect how long it takes a part to cool?

Is the bed heated? You're printing ABS so presumably yes but if the bed is heated the question isn't how quickly the part cools, the question is how quickly the bed cools.

What bed material cools faster?
I found an extensive list which relates various materials to their thermal conductivity, k [W/mK]; the lower thermal conductivity, the better the material insulates, and the slower the print bed will resist changes in temperature - both heating up, and cooling down.
Here are the thermal conductivity for some common materials for 3d printer beds:
Aluminum    205
Glass       1.05
Acrylic     0.2
Air         0.024 (for reference)

There is also the matter of thermal capacity, but I will not go into that right now (need to do some research myself first!).
Will bed material affect cooling time?
Bed material, I believe, is not necessarily related to print cooldown time: it depends on the situation, such as whether we are discussing cooldown during or after printing, and if the bed is heated or not.

If you are not using a heated bed, I believe the bed material doesn't matter at all.
With a heated bed while printing, only the first dozen layers or so are probably affected by the rising heat sufficiently that it affects the printing process.
With a heated bed after printing, the thermal characteristics of the bed will determine how quickly the print cools (and thus can be removed).

Also remember that other physical properties, such as flatness (both cold and during heating) of the bed material is vital for successful prints, and that not all materials can tolerate heating equally well!

Looks like you beat me to it lol Very well explained!

This image from "A Visual Ultimaker Troubleshooting Guide" shows an example of point number 2:
http://d33v4339jhl8k0.cloudfront.net/docs/assets/53970867e4b0c76107b1091a/images/53bd576ae4b01e9403f73b56/file-BVBVby1244.jpg
A lot of the difference in layer widths is attributable to differences in cooling between the first bunch of layers in contact with the heated bed and the layers above it, which don't receive much heat from the bed.

Assuming you are meaning the build plate and not confusing it with a printed raft, yes, different materials for the build plate will have different cooling rates. I don't know the values of hand, but a Google search can get you to a formula to calculate how long a certain size build plate of a given material type should roughly take to cool. (I'm using the mobile app right now, so I'll have to get back to this answer later to give links and more details)


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When to use 1.75 mm vs 3 mm filament?
Why do we have two standard filament sizes, 1.75 mm and 3 mm? Does it really make a difference when printing? Or is the 1.75 mm just for smaller printers?
In what situations should I be using 1.75 mm?
When should I be using 3 mm?

There's no appreciable difference. Just use the filament that fits your particular printer.
If you don't yet have a printer, then I'd get one that uses 1.75 mm filament:

1.75 mm is increasingly becoming the "standard", thus being easier to get. Some filaments are not available as 3 mm.
1.75 mm filament allows for finer control, because feeding in 1 mm of filament corresponds to less plastic extruded.
1.75 mm filament requires less force to extrude. Compressing 1.75 mm down to 0.3 mm takes less force than doing the same to 3 mm filament.

However, the advantages are fairly minor. I don't see any reason to replace a functioning 3 mm extruder with a 1.75 mm one (yet).

You mention some very good points! Do you think this mean printers with 1.75 mm extruders struggle less with - for instance - stringing?

Do note that 3 mm filament is becoming rare, 2.85 mm is more common (but not so common as 1.75 mm filament) and for instance used by Ultimaker printers and to date easily available.

There are a few factors to consider those two:
3 mm

More rigid - easier to print with flexible plastics. I couldn't make my 1.75 mm printer print with NinjaFlex using standard Bowden extruder.
Can extrude faster
Quality is less affected by changes in diameter - it is a concern mostly when using cheap plastics

1.75 mm

More popular, easier to buy
Needs smaller extruder than 3 mm
Easier to use with Bowden tube
More precise when printing

I generally agree with the points in masteusz's and Tom van der Zanden's answers, but I would add a bit more detail. Generally, the differences are minimal, however:

Generally speaking, a 1.75 mm filament will make it easier to use a smaller nozzle diameter (<0.4 mm), allowing for more precise prints in some cases.
1.75 mm filament will give you better flexibility with flow rates as it has a higher surface to volume ratio, allowing for faster melting in the nozzle, and allowing you to push your printer to higher volume extrusion rates.
The converse of the above points is also usually true. "3 mm" filament (which is usually actually 2.85 mm) will allow for better control and higher extrusion rates on wider nozzle diameters.
1.75 mm filament is indeed more popular than 2.85 mm, however the smaller diameter means that manufacturing tolerances really need to be tighter along the length of the filament—a ±0.1 mm difference in width along the length of your filament is only ±3.5 % for 2.85 mm and more like ±6.7 % for 1.75 mm, so you're going to have a bigger difference in actual flow rates compared to your expected flow rate set in your slicer, resulting in lower-than-expected print quality. That means you're probably going to want to spring for more expensive, higher quality 1.75 mm filament in order to get good prints.
Your printer's hardware setup matters, too: Bowden-based printers, like the Ultimaker 2, generally have more luck with the thicker filament because thinner stuff will usually compress more in the Bowden tube and create a stronger spring effect, causing extra pressure in the nozzle. This will often cause blobbing, stringing, and over-extrusion and hamper the positive effect of your retractions.

Ultimately, you can tune your printer and slicer settings to create or negate most any of the differences in print quality caused by filament diameter, but you may have an easier time with certain prints and printers with one diameter over the other.

I think (as do a lot of others) that the differences are rather minor. So just my 2 things I know from experience. We've been using 3 mm for some years and now we are moving towards 1.75.
1.75 mm filament is very easy to entangle, especially, if it is not on spool. You can even easily create knots on the filament and it is very hard to untangle. As long as you keep it on spool and always buy on spool, you should be fine.
3 mm filament on the other hand, creates very high tension when the spool is about to end. Sometimes the last couple of meters are unusable because of this and you have to throw the rest of the spool away.

As I read the history, 3 mm filament was an accident of the supply chain when 3D filament printers were first being developed by hobbyists.  There was a product called a "plastic welder" which consisted of a melting device and a source of filler material.  This filler was 3 mm plastic.
As the techniques and equipment developed, the market for filament grew to a size where it could support companies producing filament specifically for 3D printing.  The benefits of 1.75 mm filament over 3 mm were, IMO, huge -- especially the easier melting and lower force needed by the extruder.
Except for special purposes like pushing soft plastics through Bowden tubes, it seems from the marketplace that 1.75 mm filament as completely overtaken 3 mm filament.
A possible second-order disadvantage of 1.75 mm filament can be water absorption.  The surface-to-volume ratio is higher -- there is more surface per unit of the filament through which water vapor can be absorbed.  It is important to keep filament dry, and sometimes necessary with both 3 mm and 1.75 mm to dry the filament in an oven before use.

+1 for the historical context. From mass produced printers appearing (2010-2012?) to 1.75mm filament becoming the norm for new printers (2017?) shows how long this iteration took. I base these dates on Prusa, but don't really know the history.

I agree with all the answers above but only would  like to add if you want to build a very large printer using 0.8 mm or 1.2 mm nozzle, i would advice to go 3 mm. 1.75 mm filament then just can't be fed in fast enough.

Actually the opposite is true, since the 1.75 mm is easier to heat up since it is thinner. But that is only a problem at the high speeds you need for 1.2 mm nozzles.

One thing I haven't seen anyone mention yet is the issue of the size vis-a-vis time of the final print. 3 mm filament allows the printer to spit out a lot of plastic at once, letting you build must taller prints much faster. Larger filament can also provide a much wider base for the next layer to rest on; smaller filament needs to print multiple times side-by-side to get the same width.
Of course the fineness of the layers will suffer, but you can go about twice as high in one pass compared to when you use the smaller filament. On the flip side, the smaller filament will more easily print extremely fine layers than the bigger filament. So it's a trade off.
Consider the printers building items feet or tens of feet in height. They use "filaments" that are measured in centimeters or decimeter a instead of millimeters.

Actually, this is a pretty common misconception. I've done a fair few tests, and the filament diameter is basically irrellevant. The main factors in determining how much material your printer can spit out in a period of time (volume extrusion rate, commonly measured in mm^3/sec) are the nozzle diameter of the extruder and rate that your heating element can transmit heat to melt the filament. In fact, if you can hold everything else constant, 3mm filament typically cannot print as quickly as 1.75mm filament because it takes longer to heat the filament through to the core.

Now, to add to my above comment, in practice, your filament feed rate is usually limited (due to firmware, mechanics of nozzle pressure, or something else) in such a way that you'll rarely hit the point where you can't heat the material fast enough, so nozzle diameter is usually your limiting factor, since it tends to be quite small.

@PostEpoch - IMHO, you should turn these two comments into an answer - referring back to this answer if need be, or adding a comment here to refer forward to your newly posted answer.


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Can 1.75 mm filament be used in a printer that takes 3 mm filament?
As an extension from this question, is there any reason that you would not be able to use 1.75 mm filament in a printer that takes 3mm filament?  I know you would have to change the filament size in the slicing of prints but would there be any other problems?
Also, would using 1.75 mm filament be possible if the nozzle diameter was greater than 1.75 mm but less than 3 mm?

Perhaps you should restrict the question to a specific printer, and the part about the 1.75mm nozzle should probably be a question in its own right (though it is right on the edge of what I'd consider a good-quality question, considering the answer will just be "no").

I was mainly asking this as a hypothetical question based off the previous question I mentioned.  For the 1.75mm nozzle, I added that part to clarify what I assume the answer to the first part will be.  I assume that 1.75mm could be used, but only if it was smaller than the nozzle.  if you normally were using 3mm with a 2.5mm nozzle, 1.75 should not work.

There are some setups that can accept both with only minor configuration changes.  The stock hotend for the H-1 is one example.  You slip you mostly slip in an extra tube, and slide the hot end over to the over end of the knurled bolt and you're good to go.

Typically an extruder and hot end are designed for one or the other, and cannot support the other without mechanical changes.
The extruder may not be able to grip a smaller diameter filament with enough force to assure even feeding and retraction.
The hot end, however, is much more complex. The filament has to be pushed with force into the melting zone, which means the filament has to slide along an area inside the hot end where the filament is plastic but still put pressure on the filament ahead of it.
When you put filament into a hot end, the filament softens before the melt zone, but since the walls of the hot end are just barely larger than the filament it has no choice but to continue pressing down on the liquid filament below.
With a narrower diameter filament, though, the filament can heat, soften, then travel backwards along the sides of the hot end and cool in place, jamming the hot end, or at least preventing an even continuous flow of plastic.
Some hot ends will accept a small Teflon tube that takes this space up and allows you to do this with fewer issues, and if you like to tinker you can experiment with this, but be prepared to learn a lot and fail a lot as you find out the hard lessons of hot end design.
Generally you should upgrade your entire extruder and hot end setup to the size you want to use.

It may work for a short time but you're going to fill the melt chamber quickly and possibly overflow to a point where the filament isn't constrained causing a messy jam.  All the molten plastic will likely flow backwards to a point where the diameter isn't 3mm any longer (probably next to your drive gear) but depending on the length it may just flow up, cool down and jam the extruder.
No, the filament would just pass through unheated and not do anything.

I don't understand why it would overflow. OP correctly mentioned that the settings would have to be changed; but once that's done, wouldn't the software turn the extruder motor only 1/3 as far to extrude the same volume of filament?

In most cases, the gap around the filament would be larger than the hole in the nozzle. I don't know the math to figure it out but I am assuming it would take less pressure for the molten plastic to go backwards through the larger gap than through the nozzle itself.

Now I have to go try this. My intuition differs, but the best way to know for sure is for us to try it... :)

You just need a teflon liner to prevent this issue (that's what the H-1 used to overcome this problem).


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Troubleshooting poor adhesion at the edge of the bed
I've been printing for a week now on my new printer and have been getting great results, including great adhesion. However, most of my prints have had a fairly small footprint.
Now, I'm stepping up the types of items I'm printing, and I've started to run into a problem. Long, thin parts are starting to lift off the bed, especially at the edges of the bed.
I've read the question dealing with this issue with ABS and realize some (most) could apply to me. However, I'm printing entirely in PLA on a non-heated bed.
My question is: What is the best way to go about troubleshooting this problem? In which order should I attempt fixes to narrow down the problem most quickly?
Printer: Monoprice Maker Architect 3D (Very similar to Makerbot)
Material: PLA
Heated Bed: No
Bed Material: Something similar to BuildTak on top of an acrylic bed. (The sheet of material came unlabeled with the printer and I haven't been able to track down exactly what it is.)

There are several things you could try without spending much but even PLA will warp on an unheated bed.  I had a Legacy Kossel that I switched to an acrylic bed and had many issues with warping and prints pulling off the bed.
Some cheap things to try would be...

Adding a brim to the print.
Blue painters tape on the acrylic, remove the other material if doing this.
Place cheap piece of glass/mirror on bed and use hairspray/gluestick.
Use hairspray/gluestick directly on acrylic.  You must be careful here because first layer height is very critical to prevent damage to the acrylic from the plastic welding.  A layer of hairspray or glue should prevent it but dial in your height before printing.
If you aren't currently using a fan, you could try sealing the sides to prevent drafts.  I doubt this would change much since you are using PLA but it's an option.
If these are your designs, there are steps you can take to reduce warping as seen here.

Also many other suggestions here.

Agreed on all points. Also, remember to keep the surface clean. I couldn't get PLA to adhere to blue painters tape until I cleaned it with alcohol (even with a heated bed).

In addition, a raft will make the prints wider so it would take more force to warp.

You might also suggest the benefits of using a larger raft next to your suggestion about brims. Very good answer by the way.

You mean a brim? Rafts typically aren't larger than the print.

I use 3DLAC from Reprapworld on a heated bed. People I meet once a month during our 3D Printer meets use this stuff on non-heated beds.
I suspect it is just hairspray, but for me it did miracles. Especially printing large objects that go all the way up to the edge.

3DLAC indeed is wonderful stuff; have been using it for years on aluminium heatbed and glass. But, the tackiness of 3DLAC strongly increases with temperature up to about 90 ºC, Dimafix would even be more tacky upto higher temperatures.

Try a dilute solution of PVA glue (approx. 5:1 water:PVA) applied to the bed or the BuildTak like sheet and allowed to dry.
Keep the ambient temperature as high as possible (but not so high as to soften any plastic on the printer obviously).
Big brims help - consider adding them to the model rather than just applying them in the slicer. I've used 12 mm by 0.5 mm deep circles to good effect, particularly on acutely angled parts of the model or the extremities.


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Is packing multiple prints into the build volume a feasible workflow for powderbed printers?
With fdm printers, the 3D object that should be printed can be positioned anywhere in the build volume. But it's only practical to place it on the bottom, because otherwise support material would be necessary.
stereolithography has the same problem. Even though the photopolymer can be cured at any position in the build volume, the result would drift away if it was not held in place by support material.
The powderbed based printers (either powder+binder or any of the laser/electron beam sintering/melting variants) do not have this problem, because they continuously fill the entire build volume with powder. The support material that other printing technologies require is part of the powder based printing anyway. It would be possible to pack the build volume with many prints and print them in one go.
Given that the machines are relatively expensive, it would be economical to increase the throughput. A company that does use such printers heavily could wait a certain amount of time until a few print queued up that fit together in the build volume and only then start the process. Do people do this?

Yes, this is very popular. Look into the site Shapeways and you will see that this is exactly what they do. I've also personally seen a local 3D print shop do this with their machine. It's called batching. I similar technique can be used in traditional machine shops (mills/lathes).

Yes. And people try to pack the parts as densly as possible leaving only little space between to safe costs. There is even (expensive!) software to optimize the packing, e.g. http://www.netfabb.com/news.php?nid=29 or http://software.materialise.com/magics-sintermodule

The print speed for powderbed printing depends primarily on the height of the print; the lateral extent doesn't really matter.  Since powderbed printing provides its own easily-removed support structure, a packing that maximizes the number of items and minimizes the height will maximize throughput.


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Applying Kapton Tape To Bed Plate
There must be a trick to doing a good job of applying Kapton tape on a printer bed plate…
We built a Bukobot and even with a great deal of care ended up with bubbles under the tape and occasional overlaps. I'd appreciate any pointers.

Try using a solution made for applying window tint, maybe even soapy water.  Squeegee it out, heat the bed for a bit and you should be good to go.
This video demonstrates the process.

Does the solution go between the tape and the bed plate?

I added a link to a video showing the process in my original answer.

I like to heat my build plate up a bit before I begin. Just warm to touch. I feel that this will help prevent bubbling so soon. I would think that since the build plate is expanded with the heat, that when the tape is applied it will shrink with the build plate. I was also told that the heat would help the adhesive stick better.
The other thing I do when applying kapton tape is apply one end of the tape to a ruler, place the ruler on the far side of the build plate, and slowly begin working the tape evenly across the plate. I find it much easier to apply tape this way.


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E3D Thermistor Alternative
E3D hotends use a thermistor whose legs are insulated with glass fiber sleeving and clamped down with a screw and washer:

This solution enables the printing of high temperature materials, but it's a bit fragile and after reassembling the hotend a couple of times, the screw will have thoroughly mangled the thermistor's legs and sleeving.
Some knockoff E3D hotends use a (horrible) solution where the thermistor is just loose in its respective hole, and kapton taped to the heater cartridge wires which holds it in place:

This solution seems kind of ad-hoc, and I'm worried about the thermistor coming loose. One advantage is that it can be reassembled arbitrarily often, since just pulling out the heater cartridge also pulls out the thermistor without damaging it. Note that the picture shows PTFE sleeving which restricts the temperature, but you could easily use fibreglass in this situation as well.
Another solution is the stud thermistor:

It screws into the hole that is normally used for the clamping screw. Unfortunately you're limited to around 250C because of the epoxy used in the stud. I've also found that the epoxy fails after a while (regardless of temperature) and the thermistor isn't locked in place any more (it still works, by virtue of being constrained by the heater cartridge wires as in the previous solution but that's not ideal).
Are there any solutions, compatible with genuine E3D hotends, that:

are not limited in temperature by epoxy or PTFE,
can withstand being disassembled and reassembled better than the standard fiberglass sleeving,
is a bit less hokey than a kapton taping the thermistor's wires to the heater cartridge and hoping that holds it in place?

I like the mounting method on my Mk9 extruder: there's a small hole drilled into the heat block, parallel to the heater hole. B3 Innovations sells a thermistor packaged into a small spring. The whole assembly goes in the hole, and a setscrew (gently!) secures it. You could just as well put a bare thermistor into a spring or something similar; it's mainly to protect the thermistor from the setscrew, and from excessive bending.
From your photo, it looks like the same thing would work fine for your hotend.
However you mount it, adding some thermal grease can help conduction from the surroundings.

I have now purchased a hot-end block from here, that has a "cartridge style" cylindrical thermistor that fits into a drilled hole of the hot-end block, and is fixed by an additional screw. This system makes maintenance much easier, the thermistor slides in and out without force, and it has a connector to change only thermistor (or unscrew hot-end block without removing cables if your hot-end also has a connector).

I highly recommend this upgrade, if you are using older-style hot-ends, because it makes maintenance much easier.


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How is a J-Head Extruder Head attached to the Prusa i3 rework?
I am building a Prusa i3 Rework, and I haven't been able to find out how to attach my J-Head extruder (see below), at the moment it's just kind of held there by pressure, but it seems there are two holes on ether side of it; not sure if they're meant to hold it in place, but it seems that way.

Any suggestions as to what I should use to hold it in place?  This is definitely a part that gets moved around alot.
update

It looks like the hotend may not be all the way in, are you sure it's not stuck?
If it's stuck and you can get it in further, those holes should go directly through the smaller ring on top of the J-Head.  You just need to run a machine screw into each hole to secure the hotend. The screw will need to at least be flush with the other side to work correctly.

Oh I see what you mean...there's an indentation at the top and that seems to go higher when I push it in to the J-Head extruder.  So I just push that in further and the screws will hold it up from there?

The ring I'm talking about appears to just be visible in your picture, you have a long way to go to line that up with the holes.  Are you able to get it in far enough to do that?

It looks that way, but I didn't really push it that far up.

Is that better (see second image above)?

Yes, placing two screws in should hold it fine.