Z-axis and extruder stepper motor troubles with a Alunar m508/ Prusa i3

So I'm assembling this Alunar m508 3d printer for a friend and I'm done. Easy.

I powered it up and had it auto home. The X- and Y-axis works just fine. The z-axis doesn't work. Now, I'm not using software on my pc. I'm doing this all through the display/ knob. I tried to move the z-axis manually with the knob and it won't move. Both z-axis steppers have this faint whine to them. If I try to move them with my fingers while they whine, I can feel that the steppers are locked/ very hard to turn. I made sure that the whole y-axis gantry is leveled. I unscrewed the brass z-axis nut things so only the acme rods would turn with the Z steppers. I then connected the z-axis steppers to the X- and Y-axis pins on the main board to see if the steppers work at all, and they do. I was able to get the z steppers moving so I know the z steppers work fine. I know the z stepper wires are fine as well. I checked the z axis limit switch the switch itself works fine. the switch was open when I tired to get the steppers working. Closing the switch had no effect.

Also. the extruder stepper doesn't work as well. I checked the extruder stepper the same way I did for the z steppers and the extruder stepper works. Just not when connected to the extruder pins. It doesn't whine or anything.

I am 120% I have everything connected properly. Any ideas?

So when I try to move the z-axis... the z steppers appear as if they want to move. There's a tiny click like jolt. They dont actually turn but you can feel them trying to. Everything else, except for the extruder stepper works fine.

So, despite my issues I popped in the sd card and tried printing the test file on the card as a dry run (no filament). I unbolted the z-axis threaded nuts so the threaded rods are rotating freely with the steppers (no resistance whatsoever). I initiated the test print. It auto homed the X and Y no problem, but then got hung up with homing the Z-axis. When I hit the limit switch for the Z-axis... it began printing. The Z-axis steppers were firm in place and the X and Y were going at it no problem. I even noticed that the extruder stepper was working! I don't get it. Maybe there isnt anything wrong with the extruder, even though it wouldnt turn manually with the know in settings. The bed heated up nicely and so di the nozzle.

The Z-axis will not move though. Any help would be appreciated.

I checked the voltages across the current driver pots and all were 0.84v. I have the LSEE 3D V1 mainboard. I connected the Y-axis stepper to one of the sets of Z-axis pins and the y stepper began doing the same thing. Has to be something with the board. I also noticed that theres 5v and a 12v LEDs on the board... the 5v LED is lit.

Usually you can't move extruder before hotend is heated; this is a safety feature as extruding to unheated hotend might break things.

For Z-axis, you could try:
- connect only one motor at a time, just to see if they work individually
- rotate only other connector
- check the amps the stepper drivers are outputting. I don't know what kind of board that printer has so it's either measuring voltages with multimeter or mucking around in the firmware.
- check the steps/mm in firmware or in the printer menu. If it's Marlin, it's Control->Motion->ZSteps/mm

This machine has a LSEE 3D V1 board.

About the extruder.... that makes sense. So the extruder is fine then.

I tried one z stepper at a time, using the z stepper pin sets on the board. Does not work. I checked the z steppers using the x and y stepper pin sets on the board and the z stepper motors work. I tried the x and y steppers on the ztepper pin sets and they dont work. I has to be the z stepper pin sets on the board.

I tried the connectors red wire up, down, and alternated the connectors. The steppers are holding as in there is a magnetic field within the stepper holding the shaft. Sometimes the steppers even click and I hear whine as if they're moving and then the whining stops.

I checked the voltage across the driver pots and I got 0.84v for each pot. I haven't measured current. Can I even measure current?

The steps/mm for the z axis is +0400.0.

Quote:

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Originally Posted by spegelius

Usually you can't move extruder before hotend is heated; this is a safety feature as extruding to unheated hotend might break things.

For Z-axis, you could try:
- connect only one motor at a time, just to see if they work individually
- rotate only other connector
- check the amps the stepper drivers are outputting. I don't know what kind of board that printer has so it's either measuring voltages with multimeter or mucking around in the firmware.
- check the steps/mm in firmware or in the printer menu. If it's Marlin, it's Control->Motion->ZSteps/mm

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Ok so it seems that the problem is with the Z-drivers. MEasuring the amps is possible, but usually it's just easier to check the Vref, as you already have done. 0.84v itself doesn't tell much, it depends of the stepper drivers chips. For example with A4988 driver, 0.84v can mean either 1.05A or 2.1A, depending of the resistor on the pololu pcb. If the Z-drivers are indeed A4988, try to turn to pot so that the voltage lowers to something like 0.4V. Do it with the printer powered off just to be safe. Try turning a little at the time to see which way to go. On my pololu's counterclockwise lowers the vref.

Ok. I tried that. I lowered the voltage to 0.4v and even lower. I raised the voltage as well, as high as 1.4v. They still don't want to move. I lowered all the pot to 0.4V to see if the X and Y would work at 0.4v and they still worked fine. I'm just lost here. The crazy thing is that I have two more of these to build. The boards for the other two are different. I think the other two boards are newer than this board. Any other suggestions? Remember, the z steppers have zero load so it can only be a board/ firmware thing. I know the steppers work fine.

Attachment 10458

Well to me it starts to look like the board is defective, might be that there's bad connection somewhere and the motor cannot move as one of the phases doesn't work (or something...). Of course you could try to re-flash the firmware if not already done so. Also check for bad solder joints on the Z-pins. I don't recommend trying to remove the heatsink that's on top pf the stepper drivers, I'm assuming there's some kind of warranty on the printer.
Are the other boards are working?

Im pretty sure the warranty is already up because the machine has been boxed up in my friends garage for about a year. She got it for her kid and didn't realize how complicated it was. Later on today I'm going to hook the board up to my oscilloscope and see what the z pins sets are doing. After that I'll probably assume the board is shot and just tell her she most likely needs a new one. At that point I'll have no problem removing the heatsink to see whats under it. What I'll do is put her machine off to the side and build my printers first. See how different my machines are to hers. This way if they are very similar i'll have her buy the newer board.

So I built one of my printers and it works beautifully. I haven't done an actual print yet but I did do a dry run print and everything seems to be operational. I couldn't figure out how to hook up my oscilloscope to the bad board to see whats going on with it. I'll save that for another time. I'm going to clean up and start building my second one now.