text:
Secure disposal of 3D prints
The company I work for is protective of IP and has security procedures for disposing of anything that could be stolen for industrial espionage.  Paper gets shredded and sent to trusted recycling center, all old data storage media gets obliterated, but what do we do with 3D prints?  For any functional prototype, I have 10 or more early versions and failed prints.  Is there a good way to dispose of these so that they are unrecognizable?  Given the volume of prints I need to dispose of, it should be safe, cheap, and able to handle large batches.

I doubt that this is a new problem. Maybe the concern around IP is, but design companies should have solved this decades ago.

@SeanHoulihane many design companies destroy prototypes in many ways: some keep a stove to burn their wood/paper prototypes and sketches, others use a waste compactor, others again use old, massive prototypes as stock to machine new, smaller prototypes from. Yet these don't work for 3D printing well

Well, what did you do with prototype models before using 3D printers to produce them?

Big batches need you to be time efficient - or use a method that uses little work. So my suggestions are mainly needing oversight. Keep a fire extinguisher and safety gear handy though!
Melting together
Most filaments are melting at or around 200 °C.
I recently got rid of my box of (PLA) waste material by putting them on a tray and melting them together in a standard kitchen oven at 200 °C for about 1-2 hours. The resulting plate of plastic destroyed all structure that could be identified. This plate can be then broken up or recycled without the risk to disclose any company secrets.
I suggest to use a baking paper under the filament to be molten or a teflon coated tray, as the filament will be REALLY sticky to a blank metal surface.
About 4 liters of broken prints resulted in approximately a 5x450x300 mm sheet. If you make sure that no filament can touch the heating elements, you can get rid of quite a lot of material in each batch.
Don't do this with ABS and don't contaminate your food trays with plastic rests - use specially marked ones that are for disposal of prints only.
Green destruction
If you want to be green when destroying prints: a box solar cooker with a glass lid easily runs at 200 °C, is decently cheap and runs all day on just a couple seconds of adjusting every hour or so. You have to set it up in an access restricted area, but as long as the sun shines, it runs pretty much for free. Just make sure to put the prints to be destroyed onto some kind of non-combustible carriers, like tinfoil or aluminium trays.
ABS in Acetone
If you use ABS, exposing it to acetone fumes for a short time (seconds to half a minute will smooth the surface. Give it some minutes can destroy the structure into a batch of plastic waste without heat that hardens as the acetone evaporates again, though complex structures might need as much as an hour. Dunking ABS into acetone results in pure chemical waste, that is just a waste of acetone.
To save acetone and a way to the chemical waste disposal, try this:
Put a batch of several prints into a large, airtight box that isn't made from ABS. Pour some acetone on a tray and add a paper towel to generate a consistent acetone atmosphere in the box. Make sure to keep the tray on the floor of the box but in a way so no print will fall into it. This should dispose of the prints by merging them into a huge lump within about an hour.
Do this outside & keep fire away.

The acetone merge system leaves a lot of acetone dissolved in the ABS which will be outgassing for months.   If the concern is fumes from the hot ABS, heating in a ventilated oven should be enough.  You might consider disposable aluminum trays to hold the plastics and the resulting slabs.   I have concerns the three shredder solutions would leave too much information.   They are built for separating items into small pieces,  not for information hiding.

A plastic shredder machine it's better then a melting/burning solution. It is faster and it doesn't produce fumes. Imagine burning PET bottles.
For the shredder you need nothing but electricity for the motor. For plastic melting it would be much higher consumption. Additionally you could reuse shredded plastic for filament machine like Filastruder or Strooder.

There is a nice article about shredders on 3dhubs from 2015.
Then it depends on your budget. Around 400$ you can build one. A nice tutorial on preciousplastic.com. For 1000$ you can find shredder machines on Alibaba.

If your company has a shredder which would handle large amounts of paper at one time, it should be able to handle the plastics from 3D printing. Most larger shredders can handle paper clips and staples. 3D plastics would be even less of a burden than them. You may need to break the pieces down into smaller chunks, but I doubt it would be an issue. Even destroying most prints by hand shouldn't be too arduous.
Secondarily, you could also melt them using something hot ... a heat gun would probably do the job without issue. They get in excess of 1100°F. Since we usually melt filament at around 200°C (~392°F), a heat gun should be more than hot enough to make it an unrecognizable blob of plastic.

You can even recycle the failed print to make filament again. One more great use ABS is to make ABS juice.

@Himanshu Recycling prints to filament isn't cost-effective, especially so for an engineer working at a company. I also doubt that anyone needs that much ABS juice (to the tune of using up many failed prints).

Heat is the most easy way

There are industrial shredders that will destroy just about anything. They are not cheap, at least from a hobbyist point of view. You might look into them because they might be right for the size of your company.
Otherwise, you can simply melt them in a hot oven or with a heat gun. I would be careful about getting them too hot because some filaments release toxic fumes when heated and that might pose a hazard risk with potential liability risk.

My 2 cents. If you have a CNC machine, you could "mill" them down. other than that, garden shredder/mulcher might suffice.

PLA is biodegradable, but not in a private compost - you need to put it into an industrial composting setup to destroy it. On the other hand ABS and PC are absolutely not biodegradable, making composting them impossible. Plus, hiding the to be destroyed IP objects in the front garden for months is a lawsuit waiting to happen. Milling down the prints will create a lot of filament shredds and pieces that could give information about some parts of the print if recovered.

@Trish, I never said put it in the garden. After it's shredded, you throw it away.

@Trish Did you ever saw the shreds of a CNC? I bet you you are not able to reconstruct the original part from it not even parts of that part. And at this point I only talk about only the shreds of one part not multiple milled down parts in on batch of shreds.

But using a CNC to shred something down is a missuse of the machine. I blocks the machine for other tasks and just a fine shredder would be better.


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Leapfrog Creatr HS stops mid print (extruders not clogged)
I have tried to print a 3D model with Creatr HS from Leapfrog. This print failed twice. The 3D model is the same, .gcode the same. Surprisingly it failed at different stage. Please look at the pictures. You can see the place where extruder was when print stopped.

I checked the filament and extruders, it is NOT a problem here. Extruders are not clogged, filament is not tangled nor blocked. Stepper motors stopped working, anyway the display shows that print progresses.
I have created a ticket for this issue on Leapfrog support page, but had an answer that this printer is no longer supported.
 Does anyone has an idea what could be the core of the problem?
EDIT
Today I have tried print again to observe and answer questions from the comments. Observations are:
- The process suddenly stops
- Hotend cools down (you can observe it on the picture below - I am using left extruder - as you can see it shows 24/0; 24 is actual hotend temp, 0 - wanted temperature )
- Display shows that print is progressing even faster than it would happen when everything is fine (maybe this is not important)

EDIT2
I have opened the printer to see what is happening inside. The electronics is divided into 2 PCBs. One is an 'heavy job workhorse' (drivers and some logics), the other is a Olimex A20-Olinuxino-Micro. The pendrive with .gcode is connected to this board as well as the display and control joystick (actually encoder).

One of the USB ports from Olinuxino is connected to 'workhorse' board. Next to the USB port here you can see Rx/Tx diodes.
Observations:
When the print is in active state, two Rx/Tx diodes located on workhorse PCB blinking occasionally (mainly when there is a print head direction change), what brings the suggestion, that the data comes from Olinuxino PCB. When the print stops, these two diodes are blinking rapidly. I am thinking that there is some problem with Olimex board (it is sending uncontrolled data or data is being send too quick).
Below you can see image of drivers board with Rx/Tx diodes continuously on. There is also another Rx/Tx pair and these are also both on.

I'm going to do some search on Olinuxino board/system.
EDIT 3
Finding: During board and temperature check I have found that the fan cooling bottom Olimex pcb is dead. I have took it out, connect to +24V and... no spinning.

I have replaced the fan to a new one. Also, I have created a 20mm box model for printing, sliced it and tried to print it. No success here. After 2 lines of print sudden stop and Rx/Tx blink. I have downloaded model of Marvin, sliced it and tried to print: all ok!
Also I want to know if the data is continuously fetched from USB or loaded to Olinuxino and then used to print. So, started the Marvin print, removed USB from Creatr HS and yes, the print continues until the end. I am thinking that the data must be stored in Olimex memory and then fetched and fed to drivers PCB. Question is: where in Olimex the data is stored? Is lack of fan (and possibly overheat) damaged it slightly? If this is stored in onboard NAND memory it could cause a problem after a long time - it has 100 000 write/erase cycles.

New board would be a solution, unfortunately Leapfrog ran out of them. Olimex is selling boards, will try to buy one. I hope that different revision will work.

By 'stopped', I assume the print finished as expected, just with no extrusion? When you say 'not blocked', will another print work straight after? Is the hotend still hot? It's not clear what you say about steppers. Maybe the driver chip is overheating?

By 'stopped' I mean interrupted (without any external forces/actions). The head stops and stays in place.
By stepper motors I mean X/Y/Z axis stepper motors.

so the whole print job crashes? Is is just a print of this duration? Hot location?

I don't think so. I have successfully printed the same model when we had very hot days. Today it is around 19 degrees.

Did you abort the print as it stopped or did you give it a minute? At times a print may halt if the heater block drops below a certain temperature... You should be able to monitor and log temperature via Repetier host just by connecting to the printer with a cable. Just let it print and watch the temperature curves - if it fails again, you might have ruled out temperature droßp or identified it as reason.

is this behavior endemic to this gcode or does a print for a similarly long gcode generate the same error (just to rule out that this file is corrupt)? Can you check the seat of the connectors between the two boards and the temperature of the core chips?

@Trish: No1. Yes, I gave it about 10 minutes time after print stop to see if it resumes. From the display I can see that demanded temperature goes to 0, so problem is not here.
No2. I have tried to place model at different area of the printing bed and slice it again. Then print. Similar results. Today I will try with different model of similar length. Connectors checked and fine. Temperature: top board ok, bottom to be checked. I have found a dead fan which blows air to the bottom board, but don't think its a core of the problem. Update soon :)

I have solved the problem. After some investigation I have decided to connect directly to the drivers board. It needs to be disconnected from Olimex board and instead connected to the PC, then select 250kbps speed, COM port can be found through Device manager. I have used Repetier-Host in not Easy Mode and all possible messages turned on to see all possible messages. Then I prepared 20mm box to print and tried to print. After two lines voila! Error message:
12:35:32.401 : N187 M105*41
12:35:32.841 : Error:0
12:35:32.841 : : Extruder switched off. MINTEMP triggered !
12:35:32.924 : Error:Printer stopped due to errors.
Fix the error and use M999 to restart!. (Temperature is reset. Set it before restarting)

Now I went for quick search and learned that this can be caused by intermittent fault of thermistor or its wiring.

 So, I disconnected thermistor from the PCB and checked its resistance: 170kohm. Now, when I moved the extruders on X axis there was a particular position when thermistor resistance went to infinity. There is a connector in head which went loose. After refitting the printer is behaving correctly.
Summary:
It is a shame, that the display on this machine does not present any feedback from the drivers board. Also, the PC connectivity on the rear of this printer does not bring any clear information (rear USB is first connected to the Olimex PCB and then to the drivers PCB, some information from drivers PCB are lost). BTW: Leapfrog drivers board is an Arduino based Marlin firmware. Info sent to serial connection after connectivity established is:
Leapfrog Firmware: 2.5
Model: CreatrHS
PROTOCOL_VERSION: 1.0
FIRMWARE_NAME:Marlin V1;
Extruder offset X: 15.23 Y: 0.02

source: Stack Exchange

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

sort: votes


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How are infill paths connect to form an efficient path that respect the object's geometry?
I am attempting to write a basic slicer for some objects I am working with. I need to write a custom slicer as the objects are not polygonal based (they are implicit objects) and therefore cannot be plugged into slic3r. I can easily obtain the perimeter/shell of the objects I am working with and have a few successful prints. What I am having trouble with is how to add infill. I think the biggest hurdle is simply my inability to frame the question properly. How do current software tackle this problem?
I don't know of my current approach is feasible but if I have a collection of vectors that represent the path around the outside of the object and a collection of vectors that represent an arbitrarily large infill pattern is there a way to union the two paths together to from an outer path (the object shell) and an inner path that is the infill pattern cut out in the shape of the object?
EDIT:
Sorry for the lack of clarification. So lets say I cut out the infill pattern to match the inside of the object. How do I then intelligently connect all the broken infill segments together to form an efficient path that doesn't cross gaps or mess the object up in any way?

Based on the answers you have already, it may make sense to edit your question to clarify how the answers don't really address the problem for you (assuming we missed something critical)

You sure it wouldn't be faster and easier to take your objects and run them thru one of the apps that creates a mesh?  What is the exact format and content of your objects --  i.e. how were they generated, are they in any industry-standard format, etc?

@CarlWitthoft Unfortunately the objects are not industry standard and converting them back to a mesh would defeat the purpose of working with the implicit objects.

In my implementation (in c#) I iterated through the list of lines to check if the start point or end point are the same as the start or end point of the current line. If found then I removed it from the list and that new line become the current. All lines found would be added to a queue of points that I then turned into and array of points to make a path.

The answer to this is pretty much basic algebra: The software tackles the problem by using a set of functions that generate the infill pattern for ALL the build volume, then discard anything outside the shells. Which is determined by algebra:
Basics
Outline Function
Assume the outline of the body is a function $O(l)$ that has a parameter $l$ for its length. This function can be calculated into XY coordinates, giving us $y\mapsto O^{xy}(x)$, that is parameterized after $x$, and should give us the values of $y$ for a closed function $O(l)$.
Infill Functions
Now, let's generate a function for infill pattern. Let's make it easy for us and use a diagonals pattern: $I_n(x)=x+n\times d$
where $d$ is a fixed parameter for "distance to last line" and $n\in\mathbb Z$ is the number of the line with 0 passing the origin.
Comparation: Outline=Infill
Now basic algebra! Let the computer solve for each $n$ the term $O(x)=I_n(x)$. The result should be (in the best case) paired points, all on the linear function $I_n(x)$. Sort these points by their correlating $n$ value first, then the $x$ values.
Dealing with the results
Let's assume we have some banana shape and our solutions for n=0 are like this: $P_{i=1 \to 4}=\{\{1,1\},\{2,2\},\{3,3\},\{4,4\}\}$
Modeling starter
On the most simple cases, we hope to only have paired results - the outline is closed and thus each line passing it has to cut it in multiples of two. Because we don't allow geometry to be below $\{0,0\}$, the line in this example will pass into the body at the first solution of these points and pass out of it at the second and so on. Generally: It moves in at odd and exits at even i. So our infill lines in the example need to connect $\{1,1\} \to \{2,2\}$ and $\{3,3\} \to \{4,4\}$.
Enhancing the Modeling
checking for tangents
Now, we might have an odd number of points that solve O(x)=In(x) for a given n. Let's assume $P_{i=1 \to 5}=\{1,1\},\{2,2\},\{3,3\},\{4,4\},\{5,5\}$.
Now we need to be careful as one of these points is guaranteed to be a point in which $I_n(x)$ is a tangent at of $O(x)$. So, we need to know the first differential of $O(x)$ in the points, which is the tangent at $O(x)$. But we don't need to solve all the points: We know the first should enter and the last exit the body, so we need (for most cases) to only solve this for the points $P_i$ with $i=2 \to i_{max-1}$. When $O'(x)=I_n(x)$, we got a tangent and remove this point from the list of points to connect with infill lines.
Because we could have several tangents in a set of points, this check has to be done for all sets of points to eliminate these points.
Also, I used the "usually" there by intent: there are cases where the first or last point is a tangent, and because it is easier to cose, we should run the elimination process over all  $P_1 \to P_{max}$!
The new, reduced set of points will be a paired list: $Q_{i=1 \to 4}=\{1,1\},\{2,2\},\{4,4\},\{5,5\}$. The Infil connects $Q_1 \to Q_2$ and $Q_3\to Q_4$.
Turning Points into vectors
Now, we have our points $Q_1$ and $Q_2$ (or any other pair of $n \land n+1$, where n is an element of the odd numbers), both on $I_{n=0}(x)$. How to connect? Easy! $I{n=0}$ is a function, most likely a linear one. Along this line has to be our connecting line from $Q_1\to Q_2$, so the movement we have to plot is the function of our pattern between the points. For a simple, linear pattern this would be:
$L_1=\frac{I(x)}{|I(x)|} \times |\vec{Q_2}-\vec{Q_1}|+\vec{Q1}$
Optimisation
Sorting properly
Now, we have a set of Lines $L_n$, where, as established in the last paragraph, n is an odd number declaring it has the lower-end $Q_n$, and the upper-end $Q_{n+1}$. How do we sort these lines smartly so we have the least movement? Let's take a look at our lists:

The list of Pi, which contains all tangential points and end points. Not very helpful.
The reduced list of $Q_{n}$, which contains all the start and end points; it is sorted in a way that odd numbers are starts, and even ends.
The list of $L_n$ with i always being an odd number, that contains the movement paths (=lines) from each $Q_{n}$ to its corresponding $Q_{n+1}$

Shortest movement between prints?
Now, let's do some math again: What is the closest $Q_{a}$ to the $Q_{n+1}$ we did end at after doing the $L_n$ movement? Well, first of all, we need to make sure we don't get back to already moved paths so let's make a new list $R_{i}$, which contains all the $Q_{i}$ we have not yet moved to.
So what is the closest $R_{i}$ to the end point of the path $L_e$ we just moved? Well, easy! Solve $min|R_i-L_e|$ with i being all the odd numbers in the list of $R_{i}$ and $L_e$ the point where the printhead was sent to at the end of the last movement
fewest direction changes?
Always moving just the shortest distance might create a large number of direction changes. So it might be a good idea to keep the point-lists sorted by the parameter n of the function $l_n(x)$ that created the points in the first place, and run down that list from minimum n that generated points (which can be below 0) to the maximum n that generated points.
optimizing direction changes & movement paths
Now, we have 2 approaches that pretty much only follow the pattern. However, we might make our average movement paths more efficient by using a simple trick:
Up to now, all our line functions $l_n(x)$ had the same vector and just a different starting point to one another. So all the starts were on one side of the body, all the ends on the opposite. With a very simple trick on the infill function we can generate a group of functions that alternate the sides of the end-points between each line, jsut by adding an inverse element:
$L_n(x)=-1^n\times l_n(x)$
Now, after all the movements with the same $n$ are done, check for the closest starting point (which should be on the same side, but is not necessary the neighboring line), and go down that line fully, eradicating these points from the list of remaining points $R_{i}$. Once back on the side we started first at, we look for the closest unused point again, run down that line, rinse and repeat.

Just a quick clarification. Is this banana oriented so the line at n=0 cuts into it twice with a gap in the middle? The tangent makes sense. I've working with implicit torus/ray intersections and it works the same way. Odd means grazing (tangent ray) and even means penetrating ray.
My question now is, how do you connect the end of this first line to the next line? That is where I'm stuck. Forming a path between all the cut infill lines to form a path.

yes, the banana in exampe 1 is bent in such a way that it bends around the middle of the "gap".

@ChrisUchytil I did work out a few optimizations you could try: for a minimum number of movement changes and then the closest line to print. Mind it is not an optimization of calculation length but of the movement path.

simple answer is math but you know that for sure
more descriptive answer (but still simple and with no math) is more or less as follows

slice an object with a plane to form (calculate) outline perimeter
create a grid of infill according to your needs (ie: lines, grids or honeycombs)
calculate where outline cuts your grid of infill
abandon all what is outside
sort cut points in some order ("some" is definitely the hardest task)
join points according to your sort

and voila ;)
of course there is many details not mentioned in such description as distance between perimeter and infill, layer thickness and many others
this is just very naive and silly description but it's just to direct you where to go further
generally there is great library which you could give a try
https://sourceforge.net/projects/jsclipper/
edit
simple sort (counter)clockwise could be like this

set center point of the object (perimeter)
start from 1200 hour and calculate module and angle of each cut-point
sort them by angle

it's still very simple and it's working only for convex set

Step 5, "sort cut points in some order ("some" is definitely the hardest task)" is where I am stuck.

well the simplest way seems to be sort (counter)clockwise ;)

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


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Weird stepper issue when setting up Marlin printer
When manually controlling the z-axis in reprap, it works fine. If I use the home button, it doesn't move. Instead, it stalls/freezes/hangs. It attempts to turn, but can't successfully make a full turn.

Hi and welcome to 3DP.SE! What is the status of the endstops? Could you send M119 to the printer over USB using a terminal window like can be found in e.g. Pronterface software. Furthermore the question is very terse, please try to add more information and explain what you already tried to do to fix it. Please read this to improve your question.

An alternate software to Pronterface would be Repetier Host. Troubleshooting questions need a maximum of information available to be viable - the more information you can provide, the more likely we'll find a solution with you.

lower the moving speed of the Z-axis motor, search for

homing feed rate

in config.h as it looks like the given speed is to high.

If you run M503 you should be able to see your max speeds. They, along with your homing speeds, are probably far too high and causing skipped steps (no movement). You can lower them down temporarily with M203. http://marlinfw.org/docs/gcode/M203.html

Looks like endstop signal for Z is inverted. In this case Z will move in manual mode but when homing it will try and stop as limit detected immediately. Change Z_MIN_ENDSTOP_INVERTING to opposite value.

Triggered stops cause marlin to only allow the axis to move away from the stop during homing. If it is not moving at all, this couldn't be the cause.


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Ultimaker Original temperature sensor replacement?
The title almost says it all.
I was searching on websites like amazon.com and ebay.com for a replacement of the temperature sensor of my Ultimaker 1, but could only find replacements for Ultimaker 2 (PT100), but I know those aren't compatible.
What specifications have replacement temperature sensors that work with the tc2 signal amplifier of the Ultimaker Original?

Just to clarify, what is the actual chip on the TC2 signal amplifier? Is it AD595 or MAX6675?

You need a thermocouple, not a thermistor. Also, as you say the Ultimaker Original+, and the Ultimaker 2, (which both use version 2.x.x boards) use a PT1001.
According to this post, on E3D Thermocouple mount on UMO+, a k-type thermocouple will do:

I am changing over to E3D V6 on my UMO, and have elected to used the k-type thermocouples sold by e3d with the standard/original UMO amplifier board.

Or to be more precise, from this post, on
THERMOCOUPLE SENSOR REPLACEMENT, it is a 3 mm k-type thermocouple:

I would ask the reseller to measure the thermocouple to be really 3mm. I never bough a thermocoupler so no idea. I know that some aliexpress sellers did sell me a pt100 with 3.05mm (it doesn't fit in) so is good idea to ask for a photo with a caliper before paying.

The thermocouple in question, on AliExpress was this, SWMAKER Thermoelement Typ K (TC) für Ultimaker Original 3D drucker 3mm K thermoelement typ für Ultimaker Original 3D drucker, ~$10
Or this, considerably more expensive at €33, Ultimaker Original - Thermocouple Sensor (out of stock):

With respect to the firmware, from this post, on E3D Thermocouple mount on UMO+

Normally you won't have any modifications to do cause your UMO already works with a thermocouple.

So, assuming that you have an AD595 amplifier and not a MAX6675, ensure that you have
#define TEMP_SENSOR_0 -1

set in Configuration.h
//===========================================================================
//=============================Thermal Settings  ============================
//===========================================================================
//
//--NORMAL IS 4.7kohm PULLUP!-- 1kohm pullup can be used on hotend sensor, using correct resistor and table
//
//// Temperature sensor settings:
// -2 is thermocouple with MAX6675 (only for sensor 0)
// -1 is thermocouple with AD595
// 0 is not used
// 1 is 100k thermistor - best choice for EPCOS 100k (4.7k pullup)
// 2 is 200k thermistor - ATC Semitec 204GT-2 (4.7k pullup)
// 3 is Mendel-parts thermistor (4.7k pullup)
// 4 is 10k thermistor !! do not use it for a hotend. It gives bad resolution at high temp. !!
// 5 is 100K thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (4.7k pullup)
// 6 is 100k EPCOS - Not as accurate as table 1 (created using a fluke thermocouple) (4.7k pullup)
// 7 is 100k Honeywell thermistor 135-104LAG-J01 (4.7k pullup)
// 71 is 100k Honeywell thermistor 135-104LAF-J01 (4.7k pullup)
// 8 is 100k 0603 SMD Vishay NTCS0603E3104FXT (4.7k pullup)
// 9 is 100k GE Sensing AL03006-58.2K-97-G1 (4.7k pullup)
// 10 is 100k RS thermistor 198-961 (4.7k pullup)
// 11 is 100k beta 3950 1% thermistor (4.7k pullup)
// 12 is 100k 0603 SMD Vishay NTCS0603E3104FXT (4.7k pullup) (calibrated for Makibox hot bed)
// 13 is 100k Hisens 3950  1% up to 300°C for hotend "Simple ONE " & "Hotend "All In ONE"
// 20 is the PT100 circuit found in the Ultimainboard V2.x
// 60 is 100k Maker's Tool Works Kapton Bed Thermistor beta=3950
//
//    1k ohm pullup tables - This is not normal, you would have to have changed out your 4.7k for 1k
//                          (but gives greater accuracy and more stable PID)
// 51 is 100k thermistor - EPCOS (1k pullup)
// 52 is 200k thermistor - ATC Semitec 204GT-2 (1k pullup)
// 55 is 100k thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (1k pullup)
//
// 1047 is Pt1000 with 4k7 pullup
// 1010 is Pt1000 with 1k pullup (non standard)
// 147 is Pt100 with 4k7 pullup
// 110 is Pt100 with 1k pullup (non standard)
#define TEMP_SENSOR_0 -1

However, according to
Questions about thermocouple and thermistor, the UMO board is 1.5.7, and can use NTC100K thermistors and (maybe - but it isn't clear) a 4.7K pullup resistor:

Firstly we have to do the Challenge with a Sainsmart UM Kit with that UM 1.5.7 Board.
We also have bought the print heads by E3D model V6 which have including ntc 100k thermistors which have already tables in marlin. As the V1.5.7. Board works with thermocouple, there was the question how to connect this. I got already an answere to just connect Signal and GND, to the board but I'd have to look for the resistors behind the connectors. Is it true, that I need a different resistor for each type of thermistor?

However, it is probably advisable to stick with the 3 mm k-type thermocouple, for simplicity's sake.

Footnote
1 Apparently for these reasons, from this post, on
THERMOCOUPLE SENSOR REPLACEMENT:

The UMO has the 'old' UltiBoard 1.5x which is a shield for an Arduino Mega, with the Pololu / Allegro stepper drivers plugged on it (Like the RAMPS controllers).
At that time RTDs where not very popular, and most printers came with thermistors. To improve the temperature feedback loop Ultimaker decided to use a thermocouple with an amplifier on top of the print head, which gives better results in particular at higher temperatures.
If you want to use a thermsitor instead of the thermcopule, you just have to swap the connections, and add a resistor on the board (the place for the resistor is foreseen on the board).
You can even go for an RTD using E3D's adapter plate.
The UMO+ is using the UltiBoard 2.x which is the same as in the Ultimaker 2, so it is PT100...

Note: RTD = Resistance Temperature Detector (such as a Pt100). A thermistor is similar to an RTD, but contains a ceramic or polymer resistor en lieu of metal.


text:
Given a viscosity is it possible to calculate required pressure for desired output?
The following rheology question relates to predicting the flow of polymer-based non-newtonian fluids extrusion processes. In this case, applied to 3D printing.
I'm trying to calculate the pressure required to produce the desired output based on my current system (pictured). I'm working under the assumption that it can be described in the same way as an MFI test.
Specifically, is it possible to calculate the Melt Flow Index (MFI) of a polymer under different test conditions (dimensions)?
The MFI test is defined by the following:

piston radius (change to match my system)
nozzle radius (change to match my system)
nozzle length (change to match my system)
test load (change to match desired output)

Using either the pre-existing MFI rating or the viscosity (or shear rate and shear stress) is it possible for me to define the test load in order to achieve output (gr/min)?
This paper seems to prove this is possible but I've not yet been able to condense it into a single/understandable equation.
Melt Rheology of Polymer Blends from Melt Flow Index (bottom of page 222, 223, 224)
I know that pressure = force / piston cross-sectional area

Welcome to 3D Printing!

Uhm.. would you please elaborate how this is related to 3D printing? because as it is, this more looks like a question for engineering or physics.

It's a calculation that underlies polymer-based extrusion 3D printing. I considered both and settled on this channel given that it requires knowledge of rheology and the process itself.

please add this to the question primer and explain this significance - and welcome to the stack!

The answer hews close to the famous cliche "In theory, theory and practice are the same. In practice, they are not."   That is to say,  yes, there is a nonlinear but repeatable relationship between viscosity and pressure and feed rate.  However, it's strongly dependent on temperature, and further the apparent viscosity is a function of the pressure (think oobleck).
In the end, it depends mostly on whether a couple percent variation matters to the final product.  (and if it did, nearly all hobbyist extrusion printers would fail)

Can you put a figure to the variation found in most FDM extrusion printers?


text:
Route to transform 2d image (depth map) into a curved bracelet (and STL file)?
I've got a bracelet concept that I've sketched up as a flat design. I'm trying to found a route by which I can extrude this into a 3d object (depth map?), curve it into a bracelet, then ultimately create a STL file out of it. I'm having trouble finding a way to do this that allows me to "warp" the flat object into a bracelet before I try to print.
Is there a recommend technique for this? I'm not worried about representation of the picture; it's effectively meant to be an 'etched' pattern.

Welcome to 3D Printing!

Easy peasy.  Go to 3dp.rocks  and select the output shape you desire.  I've had excellent results making flat lithopanes.  I created a couple curved STLs which look fine in Cura; just didn't print them.

I have had a lot of success using this

This may not be your cuppa tea, but if you're willing to learn to use OpenSCAD or already know how, there's a Thingiverse post that appears to directly address your objective.
Correction, this particular post on Thingiverse consists of a series of Python files, of which I have zero experience/qualifications. It may still be of value, if you are Python capable.

Another resource that is strictly OpenSCAD is from Eric Buijs, a rather talented 3D design person. His YouTube channel has a number of useful tutorials for both OpenSCAD and Solvespace. This video in particular describes applying a flat object to a curved one using OpenSCAD, resulting in a lithophane.

As I created this answer, I did not re-watch the 12+ minute video, but I recall how he explains clearly how the program dissects the surface into a number of flat panels and then superimposes the image on each segment. From this presentation, I suspect one could expand to a full cylinder.

This is the best and simplest way I've found to transform a flat design into a 3D object that you can then save as an STL file: Blender-Converting 2D Image to 3D Object
This solution requires you to use Blender and Inkscape, both softwares are open-source and available for free at this time.
As suggested below by @Greenonline, I will provide a step by step in case the video is removed from Youtube. I'm sorry that I cannot provide screenshots at the moment, but I'm on a trip and writing from an old laptop that cannot run either Blender or Inkscape.

Load your image in Inkscape.

Format is unimportant as long as Inkscape can read it. It works with black and white and color images, but please note that color information won't be sent to Blender in the end, you'll have to add color materials yourself once the picture has been converted to a 3D object.

Select the image or the portion of it that you want to turn into a 3D object.

For some unknown reason, Inkscape doesn't automatically select the image you loaded into it, so you have to do it manually. When the image is selected, it will be surrounded by a dotted line and you'll see arrows appear on the sides and corners.

Go to Path > Trace Bitmap, or use Shift+Alt+B, and a pop-up window will appear. Keep the default settings, just make sure that the 'Remove background' option, located at the bottom of the window, is checked, then click OK.

You can see the result of the operation in the 'Preview' window. If the 'Preview' is empty, just click on the 'Update' button located below 'Preview'. If it is still empty after you clicked on 'Update', then you haven't selected your picture as indicated in Step 2!

Got to File > Save As and save your file as 'Plain svg'.

Saving as 'Inkscape svg' should work as well, but it's always best to use the standard format.

And you're done with Inkscape, time to switch to Blender.

Go to File > Import > Scalable Vector Graphics (.svg) and import the picture you just created in Inkscape.

If you do not see Scalable Vector Graphics (.svg) in the list of importable files, it means the add-on hasn't been activated. You can do it by going to File > User Preferences > Add-ons then typing 'svg' in the search field will bring up the relevant add-on (Import-Export: Scalable Vector Graphics (SVG) format). Clicking the checkbox next to it's name will automatically activate it.
The picture will usually appear very small in Blender. Press 5 on the numeric keyboard to home onto it, then you can stretch it to the desired size by using the relevant tools in Blender.
It might be a good idea to move the object center into the middle of the geometry, although, from personal experience, you can do it after it becomes 3D without too much trouble.

Your picture has been loaded in Blender as a Curve object. Go to the 'Curve' tab and in the 'Geometry' sub-menu you can use the 'Extrude' slider to give depth to your picture.
Finally, once you've extruded your curve to your satisfaction, go to Object > Convert To > Mesh from Curve/Meta/Surf/Text, or use Alt+C, and voila, you're done!

You know have a nice 3D object made of polygons that you can modify at your leisure using Blender's tools.

Could you edit your answer to include details (or at least the main points, actions, menu items) from the video, because if the video is ever removed then your answer will not be as useful as it could be.


text:
A4988 driver cooling specifications
When exchanging the mainboard of my Ultimaker Original, I found the new (unoriginal) mainboard to have a condensator that is quite a little higher than on the original, which means the fan duct doesn't fit any more.
I read somewhere that those A4988 stepper motor drivers don't have to be actively cooled, but a heatsink will be sufficient:

After testing the theory I found the heatsinks to be really hot, but not too hot to touch. Sadly I do not have any means of temperature measurement other than my fingers...
How hot do they normally get, when should I abort printing and look for a different solution?
Are there any good solutions other than the original cooler & cooling duct?

Adjust the current according your motor; an excesive current will heat the driver and also the motor.

A4988 become hot when a lot of current draw from them . If it is  more than 1.5 Amp. Also you will notice missing steps, missing layers, abnormal print and Stepper motor become hot .It automatically shutdown at max temp.

That does not really answer my question, given that I didn't change the settings of my printer.

What should I do about high current draw? Can I run the drivers without active cooling as long as they behave normally without risking destruction?

It is good to add active cooling. It also depends on your ambient temperature. My advice you to check stepper motor temperature for high current draw. Because stepper motor become hot on  high current draw.

They do get hot, but they always did. Do I need to fix this?

Not in my opinion

The answer to that question is not as simple as it looks as we don't see the hardware.
Main issue is the current pointed by Himanshu, that generates most of the temperature in the silicon chip.
I was using drivers without active cooling, but my case was open so there was enough heat dispersion.
You could do a dry run - by creating a command file with G-code like below
G28
G1 X200 Y200 F6000
G1 X0 Y0 G1 X200 Y200
...
... copy and paste many times to have a 10 minutes run on the printer

That will keep the stepper busy and you could observe radiator temperature and probably see/hear miss-steps.
other solution could be a duct like this one


text:
3D printer ends print by sinking in to it and getting stuck
I am using cura with M3D entry level printer.
When I print things more than 6-7cm/2.5-3inches, at the end of the print, the hot end sink back into the print then gets stuck as it tries to return to idle position.
Please see the attached photo.  Has anyone had this problem?  Thank you
The last 20 lines of gcode is:
G0 X50.83 Y49.982
G1 F600 X50.541 Y49.975 E4399.62304
G1 X50.268 Y49.985 E4399.62637
G1 X49.999 Y49.999 E4399.63024
G1 X49.73 Y50.012 E4399.6341
G1 X49.457 Y50.023 E4399.63742
G1 X49.168 Y50.016 E4399.63941
G0 F7200 X49.28 Y49.87
;TIME_ELAPSED:6301.614981
G1 F1500 E4393.13941
M107
M104 S0
M140 S0
;Retract the filament
G92 E1
G1 E-1 F300
G28 X0 Y0
M84
M82 ;absolute extrusion mode
M104 S0
;End of Gcode

Hi theMouse and welcome to SE.3D Printing! Please add the last e.g. 20 lines of the G-code file, than people can see if it is instructed to do that, otherwise there may be an other problem (e.g. steppers loosing power leading to sinking of the head).

As Oscar commented, check the tail end of your gcode files.  Most slicing software includes commands to move the head to x=0,y=0 at the very least.  I am a bit surprised that your files don't appear to have this, since Cura does apply said code.
Possiblly there's something lacking in your printer's firmware and it doesn't recognize some of the gcode commands.

The software that came with the printer was proprietary and did not work with my Mac, that is why I used Cura instead.  It seems to only have this problem with taller prints.  I sliced it with the recommended settings.

As can be seen from the G-code file, the head is instructed to travel to x=0, y=0 (G28 X0 Y0 is actually a homing instruction to home the head and label the position with zero X and zero Y). After that it powers off the motors (M84).
From your picture, it looks like the head digs in the print without moving to the home position, so G28 X0 Y0  is not working (although you mention it tries to move while digging in?!?). That is strange as there is no instruction to lower the head. Please alter G28 to G0 so that it reads:
G0 X0 Y0

(or G1 X0 Y0 which does work and will instruct the head to move).
The digging into the print could be explained by the weight of the head/carriage that cannot be held when the steppers are not powered anymore (as instructed by M84). When the nozzle is hot, the nozzle will then dig into your print.

Edit:
Now that I see your comment on another answer, your proprietary software may produce different G-code than Cura does, this could imply that your printer does not use a "standard" G-code interpreter or does not implement all G-codes.

Or maybe move the G28 homing command up 5 or 6 lines

Maybe worth mentioning that G28 is not a move, it is a home instruction, so the '0' should be ignored.Where you say 'alter ... in ...', it would be better as 'alter ... to ...'

From the provided G-code:
G28 X0 Y0

The meaning of the G28 code is move printhead to home.  In theory, the presence or absence of X, Y, and Z values are used to indicate which axes the printhead should move on, but as the RepRap wiki notes, some printers ignore this, typically interpreting any G28 code as "move to 0,0,0".  In particular:

Because the behavior of G28 is unspecified, it is recommended not to automatically include G28 in your ending GCode. On a Cartesian this will result in damaging the printed object. If you need to move the carriage at the completion of a print, use G0 or G1.

You should probably replace the code with G1 X0 Y0 Z[value near the top of your printer].  You could simply replace G28 X0 Y0 with G1 X0 Y0, but that risks dragging the tip of the nozzle across the upper surface of the finished print.

Basically exactly the same as this answer, only with a very useful quote.

For some reason the G28 command to home X and Y is not having an effect. I wonder if there is something 'special' in the firmware that affects how it homes.
You can try to replace the G28 with a move (and maybe a different location would be better to place the extruder in the best position for removing your print).
G1 X0 Y0 ;Move to home position

Best would be to look at one of the included 'pre sliced' models that are usually included with a printer to check the manufacturer's default end sequence.
You might also be able to configure Cura to move up at the end of the print (so long as the print is not at maximum height).

What is the difference between 0scar's G0 and your G1? Aren't they pretty similar? Don't they both just move the hotend? G1 in a straight line, and G0 maybe not so straight?

Ah, the typo in 0scar's answer caused me to fail to parse it properly... He doesn't mention homing either (but that doesn't make this a good answer)

@Greenonline, G1 is "move in a straight line".  G0 is "move as fast as possible, trajectory not specified".  In practice, a G0 move will often follow a dogleg path, as one axis finishes its motion before the others.


text:
Using two feeders at the same time
I am using Prusa i3 MK2s with the first version of the multi-material add-on.
As far as I understand, the slicer defined the used feeding motor using the T0-T3 code which defined one feeder at the time.
Is there a way to have two feeder motors working at the same time?

Please add a picture of which feeder system you use.

The first multi material add-on version off J. Prusa includes several separate steppers that load filament into the hot end. Note that selecting an other color will retract the existing filament so that the next filament can be loaded. There is no mixing hotend nozzle. It is therefore working serial, not parallel. Working 2 steppers at the same time will  lead to clogging the filament joining position.


text:
Ender 3 Calibration Cube Fail + Can't Print Circles
After noticing that my ender 3 couldn't print a 'perfect' circle I decided to use a calibration cube to see if that could be the issue. These were my results:

I did have some successful prints before noticing these problems but it would be great if anyone could help/find a solution.
I think it may be because of the belts tension as I had accidentally over stretched it by putting it over the wheels instead of under: is it worth getting a new belt then?
I use 20% infill, with triangle pattern in cura, using the standard 0.4mm nozzle.
Edit
After doing a different testprint and measuring, it revealed that both had an accurate 20mm Y and Z, but only an 18.5mm X. Might I have destroyed my belt when I mounted it overstrained?
Edit2:
After purchasing a new X belt, the calibration cube was much closer at 19 x 20 x 20. But still not at a good enough tolerance for my liking. Additionally, when printing a cylinder, two relatively flat edges were printed with it either side (perpendicular to the x-axis).

what are your slicer's settings for "number of top layers"?

@Trish I used Cura, would Slicer be better? For cura my top/bottom thickness is 0.6 mm; (the layer was 0.1 mm); the top thickness was 0.6 mm and top layers was 6

cura is perfectly fine. Any infill? what's the nozzle diameter?

@Trish 20% triangle infill. I don't know about the nozzle diameter: default for ender 3 1.75mm

Mind updating photos of the new print? the 18.5 for 20 seems consistent as you said in chat.

@jb7852 - I think the 1.75mm is the filament diameter ... it should be stamped directly on your nozzle what size it is. I'd suggest it's probably 0.4mm.

This looks like missing steps or binding in x direction. Does the carriage run smooth with depowered steppers (M84)?

My prints look almost erily identical on the cube test and i am getting bad circles. what was the best solution? did you ever fix it?

Your top layer looks like you need to add additional top layers and there are signs of a slight bit of over-extrusion in that top layer (red). On the other hand, it looks like the top layer is not sliced nicely resulting in gaps and holes (yellow), which might be a fault of the test print.

The X on the file you used is not centered, resulting in the off look in the print.
I suggest you try a different calibration print before starting to tinker with the hardware, for example this.
I suggest to use concentric only for the top layers and instead rely on a simple Zig-Zag pattern for the intermediate layers, as this usually generates a better connection to straight walls.
EDIT1:
After considering the miss-dimension in X only, you might want to look to calibrate your X steps.
The stretching of the belt might be an issue, but you might get away easy if you just check belt tension and manage to get it right again.
As I have an ender-3 myself, I know you might need to flash fresh firmware to get the ability to change the steps/mm.
EDIT2:
The 19x20x20mm cube sounds like the new belt did fix a lot of the dimensioning problem, but the steps/mm might be slightly off - or we have to trace down SOME mechanical error in the movement path. As a 140mm long test print also had a 1mm offset, a steps/mm error should be out.
After examining the machine with jb in chat, the bearing on the X-belt seemed to stick a tiny bit on one side.

Turning the large bolt of the assembly in an attempt to disassemble it without a wrench to hold the self-securing nut on the far side seemed enough to lessen the pressure on the core of the bearing, allowing it to spin freely. In addition, the belt was a little loose.

I 100% agree. Do you have any idea why my main issue was occurring i.e. the X wasn't centered/how squares came out rectangular and circles as ovals. I feel like it must be a belt problem

The x side is 18 mm though as if its squashed

@jb7852 The X of the  calibration cube from Thingiverse that you printed, is not in the center in the STL! I see the X off centered in my test cubes also. Note that this does not explain the 18 mm in size!

First, check that the calibration part you have is actually a cube. Maybe you downloaded a trick 'calibration cube' model. Cura will show he overall dimensions of any model which it is slicing.
Ignore any print quality issues first off. A hollow calibration cube is mainly used to check the X/Y/Z motion and so long as you print at a sensible (slow) speed), the other parameters shouldn't have much effect (so long as the first layer is OK, and you get within 30% of the right extrusion).
If the calibration cube is within +/- 0.5mm on each side, it's probably good. Under/over extrusion, caliper technique, etc, can explain this sort of variation, and you might want to use a bigger test part like this star on my thingiverse account once you think you're close.
The 'steps per mm' setting is determined within the firmware, it is part of how your printer consumes G-code. For a delta printer, for example, there is some fancy maths to combine X/Y/Z into the motor movements. This means that you can't change steps/mm in Cura, you need to either change the firmware defaults and 'reset to factory settings', or modify the parameters in EEPROM by sending G-code.
Seeing too small a calibration part (for a Cartesian printer) can easily be explained by problems in the printer's motion system:

Stepper missing steps due to jerk or acceleration too high
Stepper missing steps due to binding/friction in the bearings (Send M84 to idle the stepper motor, and move X by hand)
Teeth missing on the drive belt (may show up on a diagonal 'bar' print)
Loose drive pinion (maybe backlash on the flat on the spindle means the problem is greater on small parts) - see below
Flex in the drive mechanism (e.g. belt mount to traveller is loose)

An annoying feature of a lot of these problems is that for any particular repetitive sequence of steps, you might see a very consistent result. Even thought to problem is something being badly adjusted, it gives the impression that the problem is calibration.
The drive wheel is held in place with a grub screw, see this diagram from the Anet-A8 assembly diagram.

the inadequate first test cube model was what I suspected, but both having X=18/18.5 instead of 20 as in the model is a good sign something is off.

@Trish So after purchasing a new X belt, the calibration cube was much closer at 19 x 20 x 20. But still not at a good enough tolerance. Additionally, when printing a cylinder, two relatively flat edges were printed with it either side (perpendicular to the x-axis), thoughts?

Similar to this https://www.reddit.com/r/3Dprinting/comments/2zw4zn/flat_sides_on_my_circle_prints_i_have_calibrated/

It feels relatively smooth, no bumps anything

Would tightening the belt in some way help e.g. on the motor or the point pictured here. https://imgur.com/gallery/6nvme2n

@jb7852 I created a chat for this question. https://chat.stackexchange.com/rooms/83007/ender-3-calibration-cube-fail


text:
Why does my part-cooling fan cause stringing?
Really strange observation with my MP Select Mini V2 printing PLA. I've printed a dual-fan shroud so I can have a dedicated part-cooling fan. I've noticed that when I turn it on, the extruder starts stringing everywhere. Little tiny spider-web wisps. No amount of temperature change will make them go away (printing at 200 °C). But if I simply turn off the part-cooling fan, I get a perfect print. This doesn't make sense to me - isn't the part-cooling fan supposed to reduce stringing by cooling the filament faster?
More info: Using Ultimaker Cura 3.4.1, retraction enabled at 3.5 mm and 40 mm/s, which works great when the part-cooling fan is OFF. But when I turn it on without changing any other settings, I get stringing everywhere.
Please see picture below. The part on the left was printed using the part-cooling fan and the one on the right was printed without the part-cooling fan. No other changes. The part-cooling fan is pictured in upper left (bottom fan).

Why does my part-cooling fan cause stringing?
Note that I print at 0.175 mm layer height, or "Normal" for the MP Mini. The cooling fan can be controlled but if I turn it completely off then the cold end part of the nozzle won't get actively cooled. Using Cura I can slowly increase the fan over the first several levels as well, but I'm worried that if the cold end doesn't stay cold it will get clogged up with melted filament. I will try some different fan speed settings and report back - currently running at 100 % all the time.

I went back to the stock shroud with single fan to remove variables. The stock shroud has a small vent at the bottom where air blows over the part, but not much. I had the same problem - I had to put a piece of tape over the blow hole to get the part to print without strings. I also couldn't get the PLA to stick to the bed easily when the blow hole was open. I'm not using the heated bed in any cases - I've found I can print most PLA without heating the bed at all. I'm beginning to think maybe this PLA is just extremely temperature sensitive. The brand is 3D Solutech Printer Filament Real Black.

Are you experiencing problems that the part cooling fan solves? If you get a perfect print with it turned off, what feature does it provide when on?

@fred_dot_u Originally I was hoping to improve the bridging capability by forcing more air over the extruded PLA to cool it faster. I just can't figure out why more air moving over the nozzle makes strings when the whole point of part-cooling I thought was to improve bridging and decrease stringing, not increase it?

Prior to a move the print cooling fan causes the filament to cool on the outside while the nozzle is still hot, when it then moves it causes a strings to form that will be cooled instantly. This means that the cooling you have is too much and should be reduced.
This printer has a single fan to cool the cold-end and the print through a slot with the same fan. As this fan can be scheduled, it would be recommended to create a dual fan on the carriage where you have a dedicated fan cooling the cold end at a fixed voltage, while the print is cooled by a separate fan that can be scheduled through slicer settings.

Too much cooling can't make strings unless there's already oozing material to make them out of.

The fans are allowing the strings to harden instead of break. Maybe you should use more retraction or wipe before crossing perimeters to reduce material ooze during moves.

This is the answer. OP had insufficient or no retraction and was depending on the tension on molten strings to break them and let them spring back.


text:
Does Octoprint stop printing on Crash Detection?
A corner of my model curled up, causing the head to crash into it.  The Prusa MK3 detected the error, printed a message to that effect, and moved the print head to the home position.
I was surprised when printing immediately resumed, and of course immediately went awry as it pulled the model off the print bed and dragged it around.
My questions:

Is it expected that printing stops when a head crash is detected?
If so, does Octoprint recognize this condition and stop printing?

You are describing precisely how the crash detection should work on the Prusa Mk3, so it is doing exactly what it should do. If you look into this video from Jozef Prusa you will see him explaining that in case a crash is detected (steps missed are registered because the Mk3 uses trinamic stepper drivers), the print head is homed and will immediately restart printing.
Please do read this interesting post; it describes your similar problems: after detection it resumes. He noteworthy mentions that even a few lines of G-code went missing, this is probably caused by the fact that OctoPrint buffers a few commands or something that get lost because the Pruse Mk3 crash fail safe kicks in.
In effect, OctoPrint is just a simple supplier of G-code commands and does not recognize the problem to act on it and will therefore continue sending new commands after the Prusa Mk3 crash has recovered (sending ok to OctoPrint for receiving new commands) from the crash and re-homed and got the temperatures back to normal levels.
An existing plugin for OctoPrint may help you in this case. The Action Trigger Plugin is able to detect events, but have to be implemented in your firmware. E.g. the action for filament describes:

This trigger will pause the print and home the X and Y axis, giving
  the user the opportunity to change out the filament. The print needs
  to be resumed manually through the UI.

Maybe it can be configured to pick up the existing event and issue a pause. It could be worth looking into this.

EDIT
Looking closer to the ActionTrigger plugin I noticed that you cannot configure it and the "manual" is very terse. I guess this might involve some serious hacking...


text:
How to remove unwanted filament trails from sharp corners
I'm a 2-week newbie at 3D printing, working on a new Qidi Xpro machine (that is solid and one that I like). So, I do not want to believe that this issue is caused by my printer itself. I'm hoping that my settings have something to do with it.
The problem is all the filament lines (travel lines, I think) that start at a sharp corner and go somewhere else. Most often, the lines go to another sharp corner but sometimes can intersect the middle of a side. See the image below for many examples. I have drawn white lines parallel to the unwanted filament lines in case they are hard to spot.
The unwanted lines also appear in the infill underneath the surface lines. They look like porous infill grid lines since they should probably not be there, and they do not get a full load of filament extrusion. You could easily say "Oh, they are the result of a "leaky" nozzle with poor retraction, but I think it's more complicated than that. I have done a full load of retraction tests and calibrations to optimize retraction lengths and speeds to minimize hairs.
Here is an image showing the problem:

My Cura settings seem reasonable for PLA: bed 50C, nozzle 200C, print speed 40mm, travel speed 90mm (100-110 makes no difference), retraction length 8.5-9.5mm (makes no big difference), retraction speed 35mm, infill: density 20% (line, grid, makes no difference), z-seam set to random, retract at new layer = enabled.
I want to believe that something in my settings is telling the machine to extrude a 1/2 or 1/3 amount of filament when it starts those travels from sharp corners to somewhere else. But, I have not been able to solve the problem.
Everything else works fine in a print (IMHO) except for another problem that I described here. I thought I fixed that one, but I saw it occur on the image shown above (inside the infill, under the surface that is shown above).
Does anyone have any ideas that I might try to solve the problem? Thank you.
UPDATE: Here's an image with Zhop when retracted enabled at zhop height 1mm. This is an infill picture, so it cannot be directly compared to the surfaced original. But, the unwanted trails are all still there (although very thin). Maybe 2mm hop height will do it. I will run another test.

UPDATE:
I ran a second test with zhop 2.0mm, but without success. The problem was still there. (Retraction on, 8.5mm, min distance 0.8mm). Here is a comparison picture. I think the gcode is definitely telling my printer to do what it does, because the problem is not just a random leak. I think I'll try a different slicer in hopes that it generates different gcode.

UPDATE ON COMBING
Oscar pointed me to the Cura "combing" setting in his comment below. He nailed teh problem perfectly. Combing means "don't retract, and ooze as you please while you move in a straight line to the destination." That's exactly what I've been showing in my images.
The default for Cura combing is enabled. As a newbie, I didn't know enough to turn it off. Worse yet, if combing is enabled ("don't retract"), it prevents "Zhop When Retracted" from zhopping. So, all my zhop experiments did exactly nothing and had zero effect because no zhopping was occurring. After I disabled combing, then for the first time in my life I actually saw what a zhop looked like. (And thus I can assert that zhopping was not happening with combining=enabled.)
Here is an image of my new "perfect" prints thanks to Oscar's pointer on combing. The left two prints have combing off, zhop off. They are almost perfect, inside and out. The infill walls are generally solid and smooth (20% infill) and without the globs and gaps in the image on the right (with combing on).

As a closing note, I think the combing setting was probably also responsible for the problem of missing infill grids in the corner, as described in this question. The problem doesn't happen with combing off. My theory is that with combing on (as it was for that question), the oozing pulls filament out of the nozzle during the travel, so there's not enough filament at the destination to bite and bond to the corner. So, turning combing off solved 3 problems for me: the awful surface lines, the unwanted trails in the infill, and the missing infills in the corner. It also greatly improved the quality of the infill walls, too.

Could it be, that you are overextruding? Maybe you can also try a print with lower temperatures such has 190 and 180. Maybe your thermristor is off..

@dgrat, thank you for your help. I did try reducing print temp to 195, but it made no difference. It could be that my thermistor is off and that my filament is runny. (But, the machine is <2 wks old...) If the thermistor was off, then everything would be runny, yes? But for the most part, my prints and walls are smooth without overextrusion issues. I printed one of those calibration prints from Thingiverse, and it didn't look bad (not perfect, of course). I will reduce print temp as you say, to 190 then 180 and will report back.

You can Z-hop what you like, but if it is oozing it is oozing, you will always see the effects of that as it just drops down.
Basically you have multiple issues, first the oozing, second the line markings on the top.
First
Oozing is fought by applying correct settings for e.g. print temperature, retraction, coasting, travel speed, as is explained in an answer on one of your own questions. Note that you have not explorer the coasting option as far as I understand from your question. Coasting means that you stop extruding filament prior to a move when the head is still printing. This is explained by the pressure build-up in the hotend; ideally you set the coasting length as such that all the material that is pressed out as a result of the pressure build-up is extruded just before the head moves/travels to another location. Specific calibration prints can be found to tune this for your printer.

Second
The markings on the top can be removed by setting the correct combing setting. Combing does not use retraction and uses straight moves, this saves a lot of time in printing, but it makes those ugly scars on bottom and top faces. You can set the option to not comb on those surfaces, and frankly, what happens on the inside stays in the inside, I would not worry about that. A good read with additional info on combing is this post.

@Oscar, you nailed the problem perfectly! Combing was the problem, for sure. The Cura default for combining was enabled; I show my updated pics above. Thank you SO much for your help and time spent making the posts. I read your link on combing and it explained it more. If you ever write a book on all this, I would buy it in an instant. Your blue image above reminds me exactly of the calibration test I printed and illustrates exactly the stringing I had between pillars. I will study coasting next. Thank you, thank you.

Having run into this type of problem at the library makerspace, under a different slicer, I had a good idea where to start the search. It is, in your case, "z-hop cura slicer" and the best return came from Polar3D.
Keep in mind that this post is more than 2 years old, but if the feature was there before, it should be there now.
Summary (okay, dead straight copy/paste):

Cura settings > Basic > Enable Retraction - details (click the little
  gear/cog) > "Z hop when retracting (mm)"
You may see it default to 0.3mm, try raising this somewhere around
  0.8mm - 1.0mm.

thank you for your reply. You are correct, my Cura Z Hop When Retracted setting is disabled by default. I will enable it now (it is set to 1.0mm) and report back.


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Simplified 3d will not run extruder
I downloaded simplified 3d to use with Mach 3 everything seems to work properly except for the extruder which will not communicate with the new software. Not moving filament that is my only problem what is going on?

welcome to 3dprintingstack.

To use Mach3 to send printing you need to define the extruder as A instead E, since Mach3 only drives X,Y,Z,A and B motors. you can see an explanation here on is possible to send printing with mach3? Question.
I haven't tried to see if is possible to change this letters directly on 3D simplify, because i'm using ramps 1.4 instead the CNC driver control. But there is an ADDON to slice your gcode with Mach3 called gnexlab, try to find it on google search. I've downloded few years ago.
Added Link
gnexlab Addon


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CoreXY Calibration Issue
I have a Tronxy X5S and I am having issues calibrating my X and Y axis. When I print a 20 mm3 cube it comes out 19.9 mm x 20.4 mm x 20 mm. I have already made the belt tensions as even as I can get them but it did not change the calibration cube size.
I have added this upgrade to my printer for the idlers and motor mounts:

I have also upgraded the hotend to a V6 clone, after this change is when I noticed the discrepancy in the calibration print.
What else can cause the X and Y axis to be uneven in a CoreXY printer besides uneven tension in the belts?
UPDATE:
Its seems Oscar was correct in his assessment that my printer is not printing square. I printed this calibration square to measure the diagonals and I got: $ \overline{AC} = 141.82 $, $ \overline{BD} = 141.35 $. I believe the correct value for these diagonals should be $ \sqrt{2} \times 100 \approx 141.42 $.

Oscar also mentioned that I can adjust my firmware to correct this but I would rather fix the problem than apply a band-aid. Does this indicate that I did not assemble the printer frame correctly?

To be honest, the values are not too bad, it could be that the cube itself is not perfectly square. Just apply the values in the firmware and you're good to go. Also please read "How do I calibrate the extruder of my printer?"

Indeed, even belt tension is important, what helped me enormously to set the same tension in the belts on my self build CoreXY is a tool like this:

Furthermore, be sure that you do not have any binding on the Y carriages over the whole range. This causes inaccurate printing, e.g. outer walls not adhering to the inner walls (as I encountered myself in the beginning when tuning the printer), and thus inaccurate dimensions.
Also make sure that the print is not skew, i.e. are you sure that the printer prints squares? This can be easily checked by printing a large square and measure the diagonals; I used this as it will also help you find the center of the bed and the level of the bed all at once:

but many calibration prints can be found on the internet, e.g. this one but this requires way more filament to print). Schematically this results in something like depicted below:

If it is not square, you can adjust this by using a different firmware like e.g. Marlin Firmware which has options for skewness compensation that can be addressed in the Marlin Configuration.h file. A "cube" that is printed by stacking parallelograms also shows different dimensions is X and Y (one being smaller, the other being larger).
Edit
You mention that you changed the hotend; it is recommended to calibrate the extruder after changing. Note that a few tenths of a mm are very common, usually X and Y should be in the range of 20.1 mm ± 0.1 mm for such a calibration cube.

Oscar's answer is the correct solution to this issue. My printer was printing skewed and there is a built in correction for this in Marlin. Unfortunately the X5S does not have a boot loader and I don't have an ISP programmer (yet), so I am unable to re-flash my board at the moment.
In the mean time I created a software fix for this issue. I used a script to add a Affine Shear Transformation to the stl file. This adds a reverse skew to the model so the print comes out (closer to) square. Basically read all the points from the triangle mesh (STL file), apply XY shear transformation preserving Z, re-save the STL.

Nice solution to circumvent not being able to get to the firmware! +1 for this innovative solution!

aye, very creative!


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Filament Balling up on random parts of a print
The skirt prints out ok, but there is balling up of filament on some of the prints.
I am printing 50 small parts at a go, and the last 4 batches were perfect, but the fifth batch had filament problems like on the photo.
Any advice?
Thanks

I experienced that several times if my print temperature was too low. Then, the filament does not stick to the plate very well and prefers to stick to the nozzle which pulls it away. Solution is to increase the temperature by 5 to 10 degrees, at least for the first layers..

I think I found the solution, someone (not me) left greasy finger marks on the bed.  I only noticed it when the light was at a certain angle and the grease marks were under the problem items. I cleaned the bed it with acetone + microfibre, and it sticks fine as before.  But if it happens again, I will take your advice and raise the temp. BTW, is acetone ok for de-greasing the print bed? thanks!

Depends on the bed, I prefer Isoprop for that because Acetone is more volatile and agressive.

It's not available in the shops here, you think hand sanitiser is ok?

Normally, not. Hand sanitizer often contains incredients which do not evaporate away. In this case acetone is better :D I just buy Isoprop at ebay.


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20x20x20 calibration cube size change after switching filament
I used to print with PLA and everything in my printer was calibrated. But I got a new type of filament called Poly Hybrid from a friend of mine. When I print a 20 mm cube, the x and y axes are fine but z axis in cube is about 18 mm.
Should I calibrate my printer z axis again for this new filament type? Because I couldn't find any option in Slic3r in filament tab to set layer height.

Have you measured your filament, with calipers, at several locations, and compared this to readings from the other filament?

@Davo Yes I measured new filament diameter in first 1 meter and it was exactly 1.75 mm. But i didn't do it for my previous filament. OMG I calibrated my printer with previous one

could you tell what kind of printer do you have?

@profesor79 Good call, maybe the OP can add an image of the print as well!

Either your drivers miss a step, your axis connectors are loose or your steps/mm config is faulty.

Go back and re-try with the old filament to verify that does -- or doesn't -- move correctly in Z.  But Oscar's answer pretty much proves it can't be a problem with the filament itself.

@HamidFzM Please add your printer brand/type and an image of the test print to your question.

Filament type should have nothing to do with the issues you are facing. This is a mechanical issue or a slicing/scaling issue. The hotend should, if instructed to go to 20 mm height actually go to 20 mm (it did do that before!), it cannot "lose" 2 mm on the way up unless you have a lot of lost steps (e.g. too much load on the carriage pressing it down, but that seems pretty unlikely). Typical variations for Z are in the order of a few tenths of a mm for a properly dialed in printer.
Please note that the Z axis is usually controlled by a leadscrew (your printer type and brand is not known, but if you have a Prusa style printer or some sort of a cube you'll have a leadscrew, Delta's have belts), so once you dialed this in, the head will go to the instructed height.
Reasoning to your observations: If it was under-extrusion because of lower diameter filament, the last few layers should have been falling out of the hotend (considering the head goes to 20 mm and the print is 18 mm high). This is not the case; you have not described that kind of behavior.
The most likely problem is a slicing or scaling problem.
The answer to your question is therefore: "No you do not need to calibrate the Z height.". But when changing to another filament you could calibrate the extruder for this new filament; if the diameter is not far off you do not need to do that, but you could if you are into details.

Preferably questions like these need to include a picture of the print and the printer type!


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Monoprice Select Mini V2 retraction/stringing problem
I have a Monoprice Select Mini V2 and I’ve recently been having issues with little strings that are thick and sturdy sticking off of models:

I used Ultimaker Cura v3.4.1 to slice this model: Basic Retraction test using Hatchbox Black PLA filament
And the following settings:

Layer Height: 0.1313 mm
Wall Thickness 1.05 mm
Infill: 22%
Extruder Temp: 200 °C
Bed Temp: 55 °C
Retraction Distance: 4 mm
Retraction Speed: 40 mm/s
Speed: 50 mm/s
Z-Hop When Retracted: Off
Supports: Off
Adhesion: Brim

I’d appreciate any advice on how to fix this problem.

What I ended up doing was using the settings from the cat.gcode that came with the printer. It has a retraction of 10 mm specified, which I thought was a bit much, but if it works, it works.

If you haven't already, you can tweak the setting and find the minimum distance. 10 mm does seem high, would 8 mm still work? etc...

The Monoprice Select Mini V2 uses a Bowden style extrusion system. Bowden extruders compress the filament in the tube where the gap between the filament and inner tube diameter allow for the filament to buckle slightly and compress causing a pressure build-up in the hotend. Without retraction this implies that the filament will start to ooze out of the hotend once you stop extruding.
From your settings can be seen that you are using retraction. The question now arises whether you retract enough? Furthermore, this stringing can be reduced by setting the correct settings for e.g. print temperature, retraction, coasting, travel speed. It is up to you to find the correct settings; test print objects like calibration prints (like in the image you showed) help you with finding the correct settings.
Apparently, the retraction you use still allows for some filament to ooze out of the hotend as shown in your image. This means that prior to the travel move there is still some pressure left in the hotend. A parameter that reduced the pressure prior to the travel movement is called "coasting"; basically you define to stop extruding while the head is still completing the printing moves prior to the travel move. It is advised to explore this setting. Other options to investigate further include lowering filament print temperature or increase travel movement.


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Simplify3D setup for Athorbot Brother 3D Printer
Using Simplyfy3D printing software I am not sure which printer mine is called in the list (or which substitute to use).
I have an Athorbot Brother 3D Printer.
On the screen of the controller, it says "Mendel Ready".
So any help with this would be greatly appreciated.

Hi Steve and welcome to SE.3DPrinting! Did you change the firmware of the printer? Usually that message is displayed after you "booted up" the firmware. "Mendel ready" would suggest that the incorrect firmware is loaded onto your printer as you do not have a "Mendel". Please add some more info to the question whether or not you changed the firmware. When that is clear, people can write better tailored answers for you. If this is the stock firmware, the message is configured by the manufacturer of the printer probably they did not pay attention in setting the correct CUSTOM_MACHINE_NAME.

This is a Mendel


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Using multiple infill types within one model
When modelling for 3D printing, can I distinguish somehow the type of infill in various areas of the model? Say there may be some areas in the model where I want 100% infill (maximum strength) but some areas where the infill can be less (maybe 25%).
I am new to 3D printing, doing my first model (enclosure for electronics - camera module). Using tinkercad.com only so far. Places where 100% infill is wanted are usually walls of the case and "threads" for the bolts but I want to make the enclosure as stiff as possible as a whole so I am thinking about using some sparse infill in the "free space" inside of the enclosure (so that it does not break so easily when it falls to the ground etc). I just do not know how to define this within the model.

To achieve additional localised stiffness, you can also insert small voids (gaps) inside the model. These become double thickness walls once sliced and can be used to support things like screw holes.
See the 'negative' parts used with a cube, and the sliced result here:

Can you elaborate on this? I am not sure what the negative piece is showing and how to use it to bolster the number of walls when sliced. I would like to be able to define the reinforcement of holes in my model not the slicer for things like heat set inserts.

I found out I misunderstood some principles of designing/modelling for 3D printing.
I designed my object for 100% infill which is not really necessary. It turned out that one does not mostly have to take care of the infill % and just model the object for example as solid 3D cube and the printing service will then take care of it to print well, hopefully slicing it well for printing and choosing the correct infill percentage.
So instead of designing a "hollow" cube with 3mm thick walls filled with 100% infill and free space inside, one can design a solid cube and the printing service will then print it "somehow" - they may make the walls only 1 mm thick but fill the inside of the cube with 10% infill which may work just fine for final object stiffness etc.

if you send to a printing service, yes. If you print yourself, you have to choose your own infil. I know of no printing service, that sets up varied infill in an object unless specifically asked for and then they charge extra.

This does not seem to be an answer on your question, this is more a comment or extra info. Parts could be included in the question instead. Once you'll have more reputation you can add comments on other people's answers; you can always comment on your own question.


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Tell tale signs bed tape has given up the ghost
I use blue 3M Painter's tape to help with bed adhesion on my heated bed. Are there any tell tale signs which would lead me to believe I need to change the tape out?
For reference, I haven't been printing all that much, so the tape has been on there for some time. I took a look at it today and see there are some bubbles in the tape in the places where the last print I did was laid down. It appears the tape has lost some adhesion to the bed. I can run my fingers over it and it will re-stick to the bed, but is that good enough? (Obviously I'd re-clean the tape surface with isopropyl before I'd use it again, so not an issue there.)
The last thing I want to do is waste time and materials printing when I can be more proactive, so the real question here is:
What signs might the tape be giving me it's time to change it out?

Obviously, if the tape is torn or gouged in area that you intend to print on, you will need to replace it to have a good surface. If the damage is well clear of your first layer and will not risk snagging on printer mechanisms during movement, you may disregard it.
I can't really tell you how much bubbling is acceptable. If your prints still come out in with an acceptable quality, then it's OK. If it causes defects that you don't accept, or failed prints due to a loss of adhesion, then it's not.
When I started printing, I used painters tape, and would change it every few prints. To be honest, I was not very careful about protecting the tape when removing a print, and would often damage it. I also often found it easier to just peel the tape from the print bed as a way to remove a print. I don't even think I finished a single roll of tape before I eventually switched to glass/hairspray.
I never used isopropyl or other things to clean it between prints. If you are concerned with cost and waste, I would think this would be even more than simply changing the tape frequently.


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What is the best method of printing joints for action figures?
I'm interested in 3D printing toy action figures, but what I don't quite know how the joints should be designed to allow flexibility.
I could imagine maybe something like a screw and nut for the arms and legs that are separated with a hole in the middle that can join them, but I don't know how to get a wider range of motion on shoulders and hips.

(NOTE: Converting comments to an answer.)
An interference fit would probably work. There are a couple of styles I can think of which would do. Here are some ideas from thingiverse.com which may work for your needs.

(image taken from this design by OgoSport)
With this style of ball/socket, you'd have very good articulation. More than enough movement to allow for a posable action figure.
Another idea from thingiverse.com is this:

(image from this design by NEMO_from_saturn)
The idea behind this style of joint is to insert it into each part (part fits over the end). This is premade and would be easy to utilize. The thing about this is, they are covered by the licensing involved with patterns found on thingiverse.
As with anything printed or mechanical, it will wear over time. You won't ever get anything which doesn't wear. It's just a fact of how it works. Some printed filaments will have better wear properties than others, like ABS, NylonX (polyamide with chopped carbon fiber strands), nylon, PET (PETG/PETT), or polypropylene (this is not all inclusive). Each filament has its own printing properties and idiosyncrasies, so pay attention to what needs to be done to print with them. This doesn't mean all of the parts need to be printed out of this material, but rather if using a joint (like the second image), you could print it out of the better wear material and print the rest out of filament which is cheaper and is easier to work with.

Are there other options though? These aren't aesthetically appealing for something that's supposed to look realistic at all.

@VaneVoe - These were meant to be examples of what you could do. Both would work, but maybe you can come up with something which suits your need a little better. You should be able to take the second one and create something directly in your design which would work fairly easily.


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slic3r: Can I vary the infill percentage for different heights of my model?
How can I vary the infill percentage for different layer heights of my model?
Context: The bottom part of my model needs about 20% infill.  The geometry of the top part of the model (mostly cones of various sizes) prints well with 0% infill and is of course a lot faster to print if I can specify this.

@SeanHoulihane, no that does not work (not in this case), as this works the other way around, it increases infill percentage to the top, instead of lowering it. It would be unwise to print cones up side down, but in that case you are right. Therefore you need to rely on an additional mesh/volume to modify the infill settings using "per model settings", and thus it is a similar question but differently formulated in my opinion. Whether it is a duplicate or not, the community decides.

I have updated the answer of Different infill in the same part to include Slic3r. In effect if works similar as it does in Ultimaker Cura.

Let's assume the model is 75mm high; the bottom portion (which needs 20% infill) is 40mm, and the top portion (which needs 0% infill) is 35mm.

Load your model into Slic3r.
Be sure your default fill is 20%.
Right click on the model, and select Settings.
Click "Load Generic".
Select Slab. This represents a cube which is the same X,Y dimensions of your model.
Specify H=35 (the height of the slab) and Initial Z=40 (where the base of slab starts).
This creates a new part for your object.  Select it and click "+" to add a new setting.
Select Infill/Fill Density and set it to 0%.

As a result of this, the bottom part of your model (which is not enclosed in the slab) will print at the default fill setting of 20%, and the top part of your model (which is enclosed in the slab) will print with 0% fill.
You can verify this by slicing and looking at the preview.  You will see the base with your default infill, and the top with no infill.  The slic3r docs mentions several other ways to customize parameters for your model.

Your question is very similar to Different infill in the same part and Using multiple infill types within one model [duplicate]. The difference is that you specifically ask for Slic3r and a variation in layer height infill percentage.

Actually this answer describes using "helper volumes" in Ultimaker Cura to set different properties for certain parts of the model (UPDATE: that answer now includes also Slic3r instructions), but it appears that this answer is very much applicable to Slic3r also. Please read this posting. Quoting from the reference:

Finally, I fired Slic3r up and loaded the main part, then clicked on
  Settings... and then hit Load modifier... I loaded the new volume as a
  modifier mesh and I applied 100% solid infill...

Secondly, this answer where 2 different infill percentage sliced models are manually combined at a certain height may also work for you (this is a perfect valid solution for Slic3r, but requires some editing skills).
Basically, although you request for a solution for a slicer other than already described in other questions, boils down to a similar answer, the only difference is the implementation in Slic3r is called differently.

To do this in Slic3r see this reference.
The blog describes the use of a simple volume (the green volume loaded from an STL file). After loading:

Right-clicking on the main part brought up the object settings menu.
  From there, clicking "Load Modifier" and selecting the previously
  saved model adds it to the part as a modifier.
The green "+" was selected and "Fill Density" was added to modifier
  list and set to 100%.

This shows that the functionality in Slic3r is very similar to the functionality in Ultimaker Cura.

@Oscar, thanks for this answer.  I will give it a try this evening. Regarding general Stack Exchange operation, if a user's  question is flagged as a duplicate, that user receives a prompt to either (a) acknowledge the question is a duplicate or (b) edit the question to explain why it's not a duplicate.  That's why I edited my answer.  Thanks again for your excellent help!


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Anet A8 prints not good
I bought my Anet A8 less than 2 weeks ago. The setup went fine. In the first 1 week, I printed a lot, and the quality was really good. Now, the quality of prints is really bad. The infill is terrible, like little individual sticks and there are strands of PLA attached to the object(see picture). My Cura settings are:

layer height: 0.15 mm
infill: 70 %
infill pattern: grid
printing temperature: 205 °C
bed temperature: 55 °C
print speed:35 mm/s (I reduced it from 60 to 35 thinking it might fix the issue, but no luck)

Any help would greatly be appreciated.

Welcome to 3D Printing! Did you change filament, brand or color? If you did, go back to a known good filament and try your print again to see if it comes out right. Poor filament quality can cause issues. Even color variance within the same brand can give different results.

No, it's the same filament.

This effect you see is called stringing. Stringing can be reduced by changing any or a combination of the following slicer settings:

lowering hot-end temperature, (less heat means less heat input so less runny filament oozing out),
increasing travel speed, (increase in travel speed reduces the time to move to another point implying less filament oozing),
retraction, (increased filament retraction reduces the pressure build-up in the hot-end decreasing the filament oozing)
increasing coasting length (coasting means that you stop extruding filament prior to a move when the head is still printing, this is explained by the pressure build-up in the hot-end; ideally you set the coasting length as such that all the material that is pressed out as a result of the pressure build-up is extruded just before the head moves/travels to another location),
print part cooling, (see this topic)

In order to find the correct settings you will need to print so called calibration test prints. There are a lot to find on Thingiverse, just search for "stringing".
Your print temperature may be a bit high, but some PLA filament brands require that, I don't know if that is the case with your filament, but you could start try lowering that by 5 °C a time.

I think the temperature's the problem. I increased it by 10 degrees thinking it might help prints(not sure why). I'll try again. Thanks a lot!

Decreasing the temperature and increasing the print speed helped cut down the stringing. Thanks a lot!