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I've been recently building a 3D printer and I'm having issues testing it.

This is my hardware:

  • RAMPS 1.4
  • Arduino Mega 2560
  • 4x Pololu Motor shields A4988
  • 1x Nema 17 extruder
  • 2x floppy stepper motor
  • 1x DVD stepper motor
  • Generic hotend with 0,4 mm nozzle

Then I assembled everything and I started testing... I tried the RAMPS test code and it didn't work (motors did not move, but I'm sure they are OK), then I tried using Marlin and Pronterface; it showed hotend temperature stuck at 150°C, but the hotend was not hot. Moreover the motors would not move.

I also tried Repetier host and it returned an M999 error without any further explanation.

I had no problem installing firmware on the Arduino and the fan of the hotend is working. I also tried changing baud rate but it seemed not to work.

1 Answer 1

Two immediate issues I can think of are:

  • Do the floppy drive and DVD drive stepper motors have sufficient torque to turn whatever you have connected them to? You don't say what sort of printer you have built, but a holding toque of 44 N·cm (62oz·in, 4.5kg·cm) or more, is desirable. Maybe you should consider upgrading your floppy ad DVD drive motors to Nema 17 motors... See RepRapWiki - Nema 17 for more details.
  • Do you have the correct thermistor selected in the firmware? Check your firmware configuration file.

To further check the thermistor, disconnect it from the RAMPS board, and using a multimeter, check its resistance at room temperature. Then compare it with the temperature characteristic graph of your thermistor type. A general 10K thermistor has the following response curve (source):

Thermistor response curve

Does the reading that your multimeter gives, seem reasonable?

Also check the RAMPS thermistor input, by shorting the thermistor pins on the RAMPS board (using a jumper). What is the temperature reading now? It should be whatever MAX_TEMP is defined as, typically around 400°C. Again, check your firmware configuration file.


In addition, M999 is not an error, but a command used to reset the firmware/printer, after an error has occurred.