Cerealbot/Failures

Experienced Types of Failure

Clogged Print Nozzle

Symptom:

The printer gradually or suddenly ceases to extrude filament, although the extruder stepper motor appears to be working and the filament is now pinched.

Abatement:

Manual Maintenance. I will try cleaning my print head with a 0.4mm drill bit and report my findings.

• 25-1-2015
  • Possibly a welding torch cleaning wire can unclog the nozzle. Will test soon.
    • Welding torch wire did NOT work. I ended up forcing plastic through the nozzle to dislodge the obstruction. A special cleaning kit has been ordered for testing.
• 31-1-2015
  • The nozzle cleaning kit from Amazon worked well. I mounted the bit in a drill press, and gently bored out of the damaged print nozzle. Extruded filament is now 0.6mm in diameter, which means I must update all gcode to continue printing.

Loss of filament

Symptom:

The printer continues printing even after the filament is either used, or accidentally breaks due to stress.

Abatement Procedure:

Prints cannot be saved from this error, but I believe a small analog sensor with wires on the extruder GT2 gear and ball bearing roller can detect the contact between the two items that results from a lack of filament, thus the printer can be autonomously stopped and self-report the situation.

Part traveling

Symptom:

Sometimes a part will break free from the print bed before it is supposed to, and will drag under the extruder.

Abatement Procedure:

Possibly a switch attached to a servo with a long wire on it can be swung into contact with the first few layers of a print, and if it detects the print move the job can be stopped and amended remotely?

Warping

A subset of Part Travelling in which the part continues to be printed, but is deformed.

Symptom:

The edges of a part curl up.

Abatement:

This is usually caused by cold air getting to the part too quickly. Placing a container around the printer which keeps the air static should limit part warping.

Plastic Adhering to Extruder Nozzle

Symptom:

The plastic is either pushed up by the plate, or wraps up on its own and become stuck on the print head. Generally this requires manual intervention to chip off the plastic.

Abatement Procedure:

I believe that large amounts of plastic may be slowly melted off of the print head, and that the remaining plastic which may interfere with a print can be cleaned by a small field of silicon walls, which can be tested but cutting up a kitchen mitt.

• 22-1-2015
  • I will attempt to remove cooled plastic from the print head by turning on the extruder fan, and then heating the extruder to 180C. I hope and anticipate that the plastic will slough off and cool on the print bed, where it can be removed remotely.
  • visual contact with the underside of the print head is lost, I will have to go on-location to check the progress of this test.
  • 90 minutes of heat appears to have dislodges most of the plastic. The extruder is now cooling down and I will inspect it in person later tonight.
  • Alright! Most of the plastic sloughed off very cleanly from the extruder, so much so that i left it as-is and started printing again. I'm putting a note here: great success!

This system may be augment-able with a custom g-code file which first performs the above to get most of the plastic off, and then has the print head mix up a small sphere of plastic on the print bed, which it then melts and very slowly rises out of to get remaining spots of plastic which may interfere with printing. More testing is required.

Software / Connection Issues

Symptoms:

It stops printing.

Misc:

The connection could accidentally be reset by my improperly wired killswitch, I shall need to go back and calculate the appropriate resistor values for the NPN transistor I'm using.

OR

The connection could accidentally be reset by a loose USB cable which drops the serial port momentarily as the printer shakes while running.

Needs further investigation.

Misalignment

Symptom:

The z-axis can become misaligned which may result in damage to the printer.

Belt slippage

Symptom:

The x and y axis belts may slip during fast travel on a print, this results in the part printing with slosh or cliffs in either direction.

Failed Prints

Date	Failure Type	Details	Image
21-1-2015	Molten Plastic on Extruder	Part quickly came unadhered to print surface and began pushing plastic back up past the print nozzle. Recovering from this remotely was the first successful attempt at melting of plastic with gravity.	Example
22-1-2015	Serial Communication Error	It appears that the arduino killswitch malfunctioned and disabled the printer 2/3rds through a print.	Example