Extruder motor doesn't turn

Hi everyone,

I am building a I3 Rework and I am having an issue with the extruder stepper motor.

Before mounting all the electronics on the printer, I decided to test it. I am using Repetier-Host and Repetier firmware.

With the manual control of the repetier-host, I am not able to make the extruder motor turn (Neither to extrude nor to retract) whereas the other motors can.

I exchanged the extruder motor with the X-motor, and I had the same problem : so the motor is not the root of my problem.
I exchanged the Pololu A4988 from the extruder to the X-axis, and I had the same problem : so the A4988 is not the root of the problem.

After some searches on the web, I found that it can be due to the temperature of the extruder (In fact I plugged only the thermistor that said 20°C).
So I heated the thermistor with the resistor in the hot-end up to 175°C... I was still unable to make it turn with manual controls!

Is it a common issue ?

Secondly, the two motors of the Z-axis are turning quite slowly (compared to the X and Y motors) and it seems that it is intermittently. Any ideas of what can be the problem?

Thanks in advance

Did you tune the output voltages on your A4988's with a multimeter? The default Z movements in Repetier on a cartesian printer are slower than X and Y by default, and trying to drive two Z motors on one un-tuned A4988 may explain the missing Z steps.....

Thank you for your answer!

Yes I tuned them, but it didn't change anything

Here are the output for the three axis (for 1.2A motor):
X-axis: 0.367V
Y-axis:0.373V
Z-axis:0.370V

What is strange is that when I ask for a move of 10mm on the Z-axis, the motor does only approximately 90°. With a 1.25mm pitch on the nut, I should have much more than 90°. (I am using the default setting)

Any ideas? I tried to increase up to 0.5V, but there was no change

Powers of two problems with stepper motors are usually related to micro-step settings in firmware or jumpers missing from your board. You didn't provide an exact measurement to work from, so I can't say if this applies or not.

Did you try hooking up your extruder to the X axis connector on your board and see if it turns that way? This would rule out the firmware and a controller problem as possible causes.

I bought what is arguably the most expensive Bowden extruder on the market, and it only turned 1/2 revolution before it didn't work any more. Turns out that the set screw on the hobbed gear stuck up ever-so-slightly above the surface of the gear, and it got hooked on the filament guide as it turned. I was cursing the manufacturer for about 10 minutes as I cut a clearance groove into the filament guide with my Dremel, after having gone through all of the electronics and wiring troubleshooting steps. Long story short, check the mechanicals first.....

Hello,

All the jumpers are on the board. I tried to run the Z-stepper motors without the jumpers and they are turning more quickly, but with a lot of noise compared to the X and Y axis. Is there in configuration.h a parameter to change saying that it is a 1/16, 1/8, 1/4 ,1/2 or full step ? Or do we just have to change the steps per mm by calculating the good value?

Yes I hooked up the extruder on the X-axis and it was turning. I even exchange the pololu to be sure that the extruder pololu works. I also hooked up my Z-motors to the X and Y-axis, and they were turning perfectly (same for the Z-pololu). So it is not a problem of motors or Pololu.

It is not a problem of mecanics because for the moment any motor is on the printer. I wanted to try them before mounting them on the printer.

I am pretty sure that it is a problem of configuration of the firmware :/

It could be some sort of "prevent dangerous extrude" where it checks for a certain temperature before letting the extruder motor move. Because if you try extrude with no heat, you could damage the extruder.

In place of extruder thermistor, hook up a test resistor in range of 100 ohms or so. You might need to test different resistor values, in such a way that it will report a temperature around 200C. Or to have a better idea, you can check thermistor datasheet to see which resistance it ought to have at ~200C. Then you can test your extruder motor, hopefully it should work.

Thank you for your answer!

When I was searching on different forums, I read that. So I decided to try it. I hooked up the resistor and the thermistor. I heated it up to 175°C, but there was no change. (The thermistor indicated 175°C on Repetier Host)

I will try with your method

Do you think that there could be a difference between 175°C and 200°C ? I checked on the firmware and it seems that the minimum temperature was below 175°C...

But do we also need to heat up to retract?

You didn't happen to set Repetier's "dry run" mode for your testing? That could stop the extruder from working.....

I tried with and without the dry run activated.

Hello all,

Following Noobman advices, I replaced the thermistor with a classical resistor : i obtained 192.7°C on Repetier-Host, but the extruder motor still doesn't want to run. Nevertheless, when I click on extrud or retract (in the manual control tab), I can hear a very very little noise coming from the motor. It disappears when I disconnect and then reconnect the printer to my computer. I don't think that it is a problem of voltage or current on the pololu because when I exchanged the pololu with the one for the X-axis, the X-motor runs well, but not the extruder one.

Moreover, concerning the Z-motor, now they run well. With the manual control, I can go up and down without any problem. But when i click on the "Home Z position" button, I can hear a high-pitched sound without any move of the motor until I press manually the Zmin endstop.

Any ideas for these two problems ?

Thanks

For Z homing, perhaps the z homing speed is too big in config.h, you could try post your config.h in attachment.

For E to recap, you have the resistor with 192C, and you changed the motor to x so the motor wiring is good. Can you change the pololu driver to slot of x, to check that the pololu driver is good also?

For E, I have 192°C, I have already exchanged the motor and the pololu, and both are working
It can only be a problem of the host, the Arduino Mega, the Ramps 1.4 or the firmware.
Do you know how and where I can measure, with an oscilloscope, on the Arduino Mega to check if it is a problem of Host/firmware or Arduino/Ramps? I mean which pin and what signal do I need to have?

For the Z homing, here is the config.h file (generated with the configuration tool of the repetier firmware). If I decide to remove the jumpers, or not, is there any line to change on the config.h file except the number of steps per mm?

Thanks

Quote
petitchti
[...]Do you know how and where I can measure, with an oscilloscope, on the Arduino Mega to check if it is a problem of Host/firmware or Arduino/Ramps? I mean which pin and what signal do I need to have?

If you want you can measure the voltage on enable, dir and step (for the last one you do need a scope). Enable needs to be low, and if it is high the driver outputs are off. Dir gives direction, when its 0v it moves one way and when its 5v moves the other. For step you need a scope to view it and it looks like a sort of pwm signal. Also you can measure driver points sleep and reset, normally these are not "command lines", but still need to be high (5v) in order for the driver to operate - if these measure other than ~5v then driver shuts itself down. Be careful to not make any shorts. One probe can always sit on gnd so you need one probe to move around. Have the probe tips sharp and dont slip the hand because again, shorts are easy to get at this size and probably fatal.

Quote
petitchti
For the Z homing, here is the config.h file (generated with the configuration tool of the repetier firmware).

Min endstops for all axis are the same, so i suppose you have same mechanical switches on all 3 axes. But if on Z you have optoendstop, then it needs to be different.

Quote
petitchti
If I decide to remove the jumpers, or not, is there any line to change on the config.h file except the number of steps per mm?

The jumpers near stepper drivers those set the microstepping rate, and you only need to change steps per mm accordingly. IMO, would be good to have a lower microstep on Z, like 1/8 or so, and perhaps more or less like that on E. But anyway changing those jumpers is not likely to solve the problem of motor not moving.

Edited 2 time(s). Last edit at 05/24/2014 12:28AM by NoobMan.

This sounds related to my DRV8825 problem..

Ok, Thank you all!

I finally found the problem...

In fact the Ramps 1.4 was not totally inserted on the Arduino Mega... And so, just a few pins of the Ramps were not connected to the pins of the Arduino (and among them, the E0-step pin...)

As it was very difficult the first time to insert the Ramps on the Arduino, I didn't push it to the bottom...Shame on me!

I will buy some nylon screws to insert on the Arduino Mega, and then I will insert again the Ramps 1.4, pushing it to the bottom! (So that I will not need to remove the Ramps again to insert the screws)

I hope that all my problems were related to this mistake! I will let you know

Thank you again all

Thats has to be best way of solving it - so glad it works for you

Yes, everything is working correctly now

Thank you all and particularly to Noobman and Vreihen.

If I have other problems in the building of my I3, I will let you know

Thanks again