When Things Go Wrong

Basic Rules

  1. Don't panic.
  2. Sleep on it. Frustration will only compound mistakes.
  3. Persistence and patience debugs all things.
  4. You are not alone. Others can help you.

Common X/Y Table Issues

Overheating the Stepper Driver

MakerBot 000001 experienced an issue during fabrication where sometimes the X-axis stepper motor would fail to fully complete a motion, causing the print head to be displaced, ruining fabrication. It turned out that this problem was caused by the stepper driver chip overheating.

Jas diagnosed this failure by (first grounding herself by touching the metal power supply and then) touching the back of the driver chip on the stepper controller board. The chip was noticeably hot to touch during operation.

We resolved this issue in two ways:

  • First, we adjusted the drive strength of the stepper driver by adjusting the potentiometer on the stepper driver board. It turned out that we had the drive strength set too high, causing the overheating.
  • Second, we lubricated the rods of the MakerBot with a dry silicone grease, to reduce the amount of work done by the stepper motors.

This completely resolved this issue for our MakerBot.

Printing Pause (But extruder keeps Extruding)

This is commonly thought to be a communication error on the Motherboard. There are a couple of methods to fix this:

Swap ethernet cables

Switch out the ethernet cable to the extruder with another one.
Better yet, use shielded cat5e cable instead.
It'll save you a lot of headache trying to figure out why everything is behaving so weirdly.

Print from an SD card

Information can run into a bottleneck thru the FTDI chip going into the Motherboard. Having the gcode loaded onto a card in the SD slot on the Motherboard will prevent this.

Turn off the Control Panel when Printing

Having the Control Panel open when printing causes more information to be sent back and forth to the computer. Which can slow down the info sent to the Cupcake.

Reduce EMI

Use shielded cat5e cable.

Electromagnetic interference may be leaking into the communication cables. Compact fluorescent lights are rumored to cause this. The motors themselves generate a lot of noise. Try to separate communications cables from motor cables and other noise sources. Twist together pairs of feed wires going to the same device where possible. This helps both the communications cables from receiving noise and the motor cables from emitting it. (i.e., twist both.) (The ethernet cables are already constructed this way internally.)

Build a simple noise suppression circuit to reduce back-EMF from the DC extruder motor. See here and
here for more information.

Check RS485 Terminating Resistor

The RS485 bus that is used by the extruder needs a terminating resistor in at least one position on the bus. This means that there should be a resistor in the position next to the RJ45 jack on the upper point of the board. The RapRap Wiki mentions this here and says that it may be omitted, but that at least one device on the bus should have one. Since most setups only use one extruder, installing this may solve the issue. A larger explanation of why this is necessary was made here on the MakerBot Operators group.

Common Plastruder Issues

Plastic Filament Not Feeding

We found it incredibly useful to draw a pattern on our Idler Wheel with a sharpie. In normal operation, the Idler Wheel turns very slowly, and it is very useful to be able to visually see when the Idler Wheel is turning, and when it is stuck.

When the Idler Wheel stopped turning, we knew we had a plastic filament feed problem.

We encountered several different causes:

  • damaged plastic filament
  • misadjusted Idler Wheel tension
  • plastic filament slipping off the Idler Wheel
  • nozzle jammed too closely to part or platform causing increased pressure in the head
  • teeth of the drive pulley filling with plastic during any of the above problems (this usually causes the filament to be stripped and damaged, causing more problems)

Damaged Plastic Filament

Rarely, the toothed drive pulley manages to etch an indentation into the plastic filament. As a consequence, there is nothing for the drive pulley to push against, and the filament doesn't advance.

One way to fix this condition is to apply some physical pressure, pushing the filament into the Plastruder. Eventually, the filament will advance past the damaged section, and the drive pulley will start grabbing the filament again.

Alternatively, you can put the Plastruder into reverse, and gently pull the filament back up and out of the plastruder. You should be able to physically inspect the filament to confirm the problem. Then, use a pair of scissors to snip off the damaged section of filament, and feed it back into the Plastruder.

This can also be a symptom of the idler wheel being too loose to adequately grip the filament. If the teeth of the pulley do not sufficiently indent the filament, the teeth created will have insufficient strength and be striped away, creating a 'flat spot' where it will be unable to advance. Try adjusting the idler wheel slightly tighter than the 2mm guide rod, or even as tight as possible as it will not adversely affect its operation.

Misadjusted Idler Wheel Tension

It's easy to get the tension in the Idler Wheel wrong. If the Idler Wheel is too loose, the drive pulley won't grab and push the filament.

We had difficulty with our Idler Wheel tension because we tried to adjust the tension after fully assembling our Plastruder, with the Plastruder electronics in place. It turns out that it's hard to get a wrench in the right place if the Plastruder is fully assembled. Instead, it was useful to adjust the Idler Wheel tension with the Plastruder on a benchtop, with the electronics off to the side.

Initially, our team was concerned that making the Idler Wheel too tight might be problematic. We found that we were able to fix the Idler Wheel at its closes position to the drive pulley, and everything worked great. The plastic filament was crushed between the pulley and idler wheel, but this turned out to be a good thing. The pulley applied good, constant pressure to the filament.

One word to the wise: do be careful when tightening down the nuts holding the Idler Wheel in place: acrylic cracks easily under pressure. Using washers to properly fill the space along the Idler Wheel bearing is crucial to having a snug fit without breaking the acrylic.

Filament Slipping Off Idler Wheel

On one Plastruder, we observed the plastic filament slipping to the side of the Idler Wheel. The filament would then be pushed against the wall of the Plastruder, where it would jam.

Some customers were able to adjust the position of the Idler Wheel by moving washers from one side of the wheel to the other. However, my team resolved this problem by taking two Idler Wheels and super-gluing them together, creating a two-panel-thick Idler Wheel. This Idler Wheel was easier to position and worked perfectly the first time. Note: we don't recommend using this technique on mk4 or later extruders! See a more detailed discussion of this technique here:

Filament not going through the nozzle

If you find that your filament is blocked somewhere inside the white thermal barrier, it may well be that it got blocked at the entrance of the heater barrel: the thermal barrier hole may be larger than the heater barrel hole, creating a thing edge around. First, make sure that you have heated the plastruder well (a good 2 minutes at working temperature) before inserting the filament. That should help soften it to negotiate the opening. Second, if you still are having problems, before inserting the filament take some sanding paper and sand the edge of the filament into a point. That should make the filament properly align itself in the hole.

Flossing the teeth

If you get repeated jams that seem to go away if you push on the filament from the top or if you back the filament out and cut off the stripped piece and put it back in, then you probably have clogged driver pulley teeth. The only effective way to fix this is to take apart the plastruder and pick the plastic out. If you find yourself doing this frequently, it might be helpful to leave out the first screw on the motor (the inside one) so you can easily remove the motor by taking out the other three instead of disassembling the whole plastruder.

If, however, pressing down on the filament only helps a little and it just gets more stuck and stops, then you probably have a clog in your nozzle (possibly caused by Burning Plastic).

Burning Plastic

If the ABS plastic burns inside the Plastruder, it can create an oxidized ABS plastic byproduct that will occlude the Plastruder print head. This is difficult to repair, and can be caused by setting the temperature of your Plastruder too high.

The ideal temperature for melting ABS plastic is around 220 degrees-C.

To avoid this condition:

  • Every time you remove the ceramic tape, visually inspect your nozzle and make sure the thermistor is well placed and not peeling off.
  • Validate that your thermocouple works. You should see the thermocouple reading change soon after turning on the heating element. Be suspicious if your thermocouple reading does not change.
  • Don't set the target temperature for the Plastruder higher than 225.

Hypothetically, the ABS plastic could get scorched if the plastic filament feed gets stuck, and the same chunk of plastic heats in the print head for too long a time. In practice, however, we've cooked ABS plastic in the print head for extended periods (10-20 minutes) without adverse effect. But: don't run this risk unnecessarily.

This can be fixed by totally disassembling the heater barrel and nozzle and cleaning out all plastic and other debris from the nozzle and barrel. Acetone and several other solvents dissolve ABS, but very slowly and only with some physical help. (This may take several hours to a day with frequent agitation and prodding.) Pouring almost pure acetone into the barrel while keeping the barrel+nozzle assembly vertical (for example inside a shotglass) will weaken after 24-30 hours the ABS enough that it will be pushed out on the next extrusion. Also don't forget that acetone evaporates quickly. Other more violent methods are known to work but should be taken at your own risk. (Someone want to describe those?)

Insane plastruder controller

Occasionally, the plastruder goes insane, possibly because it loses its firmware. This is characterized by messages in ReplicatorG like "Error: Payload is not big enough." and the temperature reading in the control panel is zero even when the thermistor has the correct resistance. Other more subtle signs may occur before this, like the control pannel extruder stop button not exactly stopping the motor.

There are two ways to fix corrupted firmware. The hard way is to follow the Plastruder Firmware Update instructions. You could also update your thermistor table or firmware version at the same time. The easy way is to use ReplicatorG itself to update the firmware as follows:

  1. Power off your cupcake and disconnect the ethernet cable from the plastruder controller
  2. Connect the usb-ttl cable directly to the plastruder controller
  3. In ReplicatorG, choose Machine—>Upload new Firmware
  4. choose Extruder Controller and click Next
  5. Choose the version of the firmware you want to load from the list
  6. Choose the serial port

You may need to mess with the reset sequence, same as listed in the (hard) firmware update procedure above.

If ReplicatorG fails to load the firmware, and the reset sequence doesn't help, you may have to reload the bootloader too with the programing cable included in the delux kit.

also it's a good idea to switch to using shielded cat5e cable to help keep the firmware from becoming corrupted in the first place.

Plastruder temperature is not stable or not heating

*MK5 Plastruder- If you fire up your plastruder and it holds a steady temperature, just below the target, you may need to check the solder connections of the PTFE coated wires connected to the Power resistors on the steel Thermal Core. If you have a broken solder joint, and one resistor is not heating, the temperature will rise and hold, just at the wrong temperature. This would be the same situation if one of your resistors has bitten the dust.

If you see the temperature graph in Replicator G, when up to full heat, the graph should be a steady straight line showing the Plastruder temperature on the target temperature. If the graph of your Plastruder temperature looks like a sinewave, you need to change your extruder controllers' PID values. This can be accomplished in Replicator G, Machine menu, Extruder Parameters Menu. There are some specific wiki pages devoted to determining PID values PID Controller Tuning The PID settings will keep the extruder hot and keep the temperature steady, making for consistent extrusion.

*MK4 Plastruder- Signs of this could be subtle, but the most obvious is that immediately after aborting a build due to a stalled extruder, the temperature in control panel is much lower than it should be for the cooling time between abort and opening the panel. The wires on your nozzle may be damaged. To test this, turn off the system and measure both the thermistor and the nichrome heater.

The heater can be measured easily without disconnecting it. Turn off the machine, and measure the voltage across the nicrhome terminals. (It should be zero with the machine off, but there may be some residual voltage for a short while.) If the voltage is zero, switch to resistance, and check if the nichrome measures around 6-8 ohms, as it did when it was built. (You can also disconnect the wires and measure it, which may be a bit safer.) After you've initially measured, gently wiggle the wires from the loose ends to the nozzle and make sure that the reading doesn't fluctuate. If it does, you have a intermittent connection somewhere. As the nichrome doesn't solder, the joint between the wires and the nichrome is a likely spot.

*Thermistor Readings- The easiest way to test the thermistor is to check the control panel with the power on. Check if the temperature reading is reasonable. If the nozzle is cool, heat the thermistor directly with your finger (not on a hot nozzle!!) and see if you can get the temperature to change by a degree or so. Gently wiggle the wires and see if the temperature jumps. If it does, you have an intermittent connection somewhere.

If the thermistor temperature is not reasonable, with the machine off, disconnect the wires for the thermistor and check the resistance directly. A room temperature nozzle should be 90k-110k ohms. If it reads as open circuit or short circuit, your thermistor could be damaged or the leads to it touching, etc. If it looks ok when measured directly but wrong in the control panel, your extruder controller might be damaged or insane — try reflashing it. (see above)

Unless otherwise stated, the content of this page is licensed under GNU Free Documentation License.