Z axis won't move with both motors connected - squeals and grinds

Hello!
I am building my first non kit printer.

All is moving except the Z axis.

Playing around with it tonight;

1: move the Z and it just screams and grinds - will not move.

2: raised (and lowered) the pololu pot voltages.

3: replaced with a brand new pololu (current ones have never been used)

4: unplug one motor and it works flawlessly!

Hardware;
TAURINO power
RAMPS 1.4

PSU seems fine. I use it in my prusa i2.

This seems to be my last hurdle.
Extruder works (I think), hotbed works and extruder heaters work.

Just about working fine except the Z..

Anyone have any idea?
I am at a loss. Power does not Seem to be an issue?
Blown steppers?
Doesn't seem like it if they work alone?

Thanks!!

kingoddball Wrote:
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> 4: unplug one motor and it works flawlessly!

Is that true of both motors?

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Waitaki 3D Printer

have you checked your z threads are perfectly vertical?

if you turn them by hand is it easy to turn?

when assembling mine, I found the x clamps ( idler and motor ) were really stiff and not the correct width pulling on the threaded rod of the motor making it grind because of the pressure.

Edited 1 time(s). Last edit at 10/17/2013 06:37AM by clack.

Do you have them connected in series or parallel? My motors did not have enough torque to turn the lead screws when connected in parallel, but in series they are more than adequate.

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[blog.bodgycorp.com]

Are the two motors turning in the same direction?

...R

Hi All,

Motors - Both work when separate.

They turn easily by hand (will double check)

Both motors are turning in the same direction.

Parallel or series?
What is this and how can I tell?


Thank you all!

Edit: More Info:
I remember - When I try to turn the motors (Printerface or LCD controller), after a few seconds of moving (i.e: 10mm moves) the pololu heat sink is HOT!! Cant keep finger on it...

Which is why I changed it.. New one - Same thing. No other axis does it.


Had a thought...

The power connectors:

4 pins; 2+ and 2-

I have it wired as 2+ / 2- but where it connects to the PSU, I spliced the two together...

The 2 POS lines go into one when connected to PSU (wire guage is fine) (same for NEG).. Could this be an issue?
Only done it this way, as I do it this way for my i2.

Edited 1 time(s). Last edit at 10/17/2013 06:15PM by kingoddball.

what is the motor you are using?

If you have plugged your steppers into the two Z-motor headers on your RAMPS board then you have your motors in parallel.

This diagram is from the Mendel90 instructions (thanks Nophead!)



I'm not 100% sure on the technical explanation, but I'm fairly certain that running the motors in parallel decreases the resistance, hence requires more current from your stepper drivers.

Edited 1 time(s). Last edit at 10/17/2013 09:35PM by pnit.

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[blog.bodgycorp.com]

After playing around with it...
Seems like a power issue. Turn 0.1m works. Turn 1m it squeels for about 5 seconds then turns.
If I turn two or three clicks (LCD panel) it just screams until it moves once then screams..

Rods are fine, motors or not stiff or hard to move..

I was fiddling with an option in the controller settings to raise VMax or something which slightly fixes it..

Will wiring in series lower the power required?

I think series could be the solution. So close!

I'm not an expert, but my MendelMax runs both Z motors in parallel and I've not had any problems.

Technically @pnit is correct. Putting 2 motors in parallel, will require the Z stepper driver to deliver twice as much current as for a single motor.

I'd go for a process of elimination to determine the problem. Its possible that one of your Z motors is defective.

Try connecting the X and the Y motors into the Z output and see if you get the same result.

I think you said that you've replaced the Z stepper driver. If not you could try swapping the X and Z stepper drivers and confirm that the driver works for the X motor.


Note. I've blown up 4 stepper drivers in the past, due to a problem with my Arduino, so be very careful not to let the stepper drivers get hot.

Wouldn't it be easier and more logical to give each stepper its own driver but to parallel the step and direction signals that control the drivers so both receive the same data?

...R

You can do that and get better performance but it costs more. Series will always work as you get the full torque on each motor. If you get enough torque with parallel it should have a higher top speed.

Edited 1 time(s). Last edit at 10/18/2013 04:14PM by nophead.

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[www.hydraraptor.blogspot.com]

I have the same problem. I have located it down to the linearity of the motors. There is a 5% tolerance in position from motor to motor. There is a possibility of a 10% spread beteen two motors (just like there is a posibility they could be right on). Effectively they just fight each other on a back emf level. If your motors dont happen to be matched/linear then driving motors in series or paralell is technically a bad idea. I think I will use the extruder 2 stepper drive and tweak the firmware instead.

I also read that the micro stepping gets messed up when you do this too. At speed they resonate against each other. While running slow things are not too bad. Its possible the original post here had a 0.9 degree and 1.8 degree motor to get such bad performance.


Am I full of it? or can other people qualify this?

I had this happen when my z axis wasn't level. One side was slightly higher than the other. Initially it would move but then just start to squeal as they moved more until eventually they wouldn't move at all and only squeal. It was only the slightest out of level and making it perfect made all the difference.

I have had this issue, I twas as simple as turning up the current and also slow down the speed of the z axis...
or its the wiring

Could you provide the final solution to this? I have the same situation. Parallel motors on RAMPS. Either motor works, both whine for 5 seconds or so and don't move.

I have a 3DP11 and 3DP12 alone the stepper motors require a current setting of .452 with the stepper in parallel they require .710

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