Stepper motor help...STM5776

Hi,

So my laser machine has developed an almighty vibration when moving the y axis back and forth. It runs off of a single motor mounted in the center of the machine, attached to a pulley which then transfers into a shaft through couplings and runs dual belts either side...if that makes sense.

We were running some precise but elaborate work this week at 150mm/s and I think this has damaged the motor, everything else seems to be fine so I am guessing that this is the issue.

The motor has the following on the sticker...

Model : STM5776 CE
4.2A (U) 1.8deg/step
www.autospark-tech.com

A+ A-
B+ B-

I have had a google and can only find a couple of pages that don't have any specs that I can figure out. Have any of you seen or used one of these? Any ideas on what I can use to replace it? It is running off of a DM556 if that helps any

Ive tried contacting the supplier but they are next to useless and I need to get the machine back up and running. I also tried the website....I have NO idea what is going on on there lol, there are pictures of scantily clad women and different chats about shipping companies to mobile suppliers and the marketization of Chinese enterprises :disillusionment:

Attachment 25177
Attachment 25178

is the same motor used on the X axis ?

if it is, I would try swapping motors to see if the fault goes with the motor or stays with the stepper driver

what is the supply voltage powering the DM556 ?

using the rule of thumb from Geckodrives web site

ideal supply voltage = the square root of the motor inductance in mH x 32

with a 45V supply I would look for a motor with an inductance of 2.2mH
(you may find the nearest you can find is about 2.8mH )
and going by the label motor current = 4.2A

the NEMA motor sizes relate to the physical imperial dimensions
so a NEMA 17 will be 1.7" square and a NEMA 34 will be 3.4" square

John

Thanks John,

Ok so its a Nema 23. I never knew that about the sizes and Ive been using them for years....mind blown!

I have two power supplies in the machine, one with one live, which I am assuming powers the Nema 34 which raises the machine bed and one with 2 lives coming from it which I am assuming powers the 2 Nema 23s for the X and Y axis.

This is a.....

LRS-100-24
Input 100 - 240
Output 24v @ 4.5a

Attachment 25180Attachment 25181

Pictures for reference.....

24V is lower than the 36V I expected

what is the other power supply rating

have you measured the supply voltage at the DM556 terminals
just in case the bootlace ferrule crimped joint has gone high resistance

John

I haven't checked the voltage but I can do that tomorrow just to make sure.

The other unit is a LRS-350-36 36v @ 9.7a

I'm on my mobile now so can't post a pic of it at the mo. Let me know if you need one. Thanks for the replies by the way John, it's very much appreciated

First check if the vibration is not mechanical.

Second and easiest to do, I would swap the X and Y motor plugs from the drives, the 6 wire connector, assuming two motors are identical and powered by the same psu. Now when you jog the X axis, the Y will be moving and vice versa. If the other axis is vibrating then the drive is faulty. NEVER unplug the motor and power plug from the drives before turning off the power!!
I cannot see if there is a plug at the motor end. If it has a plug, you could easily swap the motors as John said and this way you find if it's the stepper, cable or drive faulty.

Third but most likely, I would check/replace the motor cable, if your Y axis cable is the one that is moving inside a cable chain.

The stepper motor is the last thing I would suspect to fail.

Ok guys, I have just swapped the 6 cable plugs over and its the same issue. The x is running as smooth as and the Y jolts when it moves and stops so violently that the machine visibly shakes.

I'm going to check the connections at the motor end on the Y in a second, the machine will need to be disconnected and pulled out which is why I haven't done it just yet.

Any tips on checking the wiring at the stepper?

The Y wiring is static, the motor is fixed at the end of the axis and doesn't move so unless something has come loose I wouldn't have thought that the wire would have failed but who knows!

Have you checked it mechanically? Check for any play of the motor shaft first and then the pulleys, belt, rails, etc.

edit: Could be the stepper rotor rubbing against the stator... Try turning the motor by hand and see if it is turning smooth.

Hi Paulus,

Yes all checked manually. I've just taken the belt off again and checked the following..

No discernable play in the shaft of the stepper motor.
Pulley grub screw is tight
Moved the Y axis back and forth with the pulley to stepper belt off, everything felt smooth, checked the bearings as best I could but they look fine. They are 6001Z and the shaft is supported twice, either side of the belt pulley at both ends if that makes sense.
Ill take the main Y belts off in a second and see how the axis moves without any resistance at all.
Couplings adjacent to the motor seem fine, no play in them.

Here is a pic of the set up....

Attachment 25201Attachment 25202

How is the cable connected at the motor end? Is there a connector? Or are the wires soldered? Does the motor have 4 or 8 wires? If you disconnect it you can check the impedance of each winding with a multimeter on ohm reading and see if you get same values on each pair. Then connect with another cable or 2 cables with 2 wires, anything you may have around.

By the looks of it at the rear of the motor there is a black block connected to it which has a single black sheathed cable going through the panelling and straight down to the controller unit.

The wire has 4 strands, black, blue, green/yellow and brown. Black and brown are linked together in the controller, green/yellow and blue are on their own. I've attached a picture of the controller unit so you can see how they enter.

Can I just take the connecter block off and check or does it need to be at the stepper end?

Attachment 25203Attachment 25204Attachment 25205

Just as a heads up.

Took the Y axis belts off.

The Y axis free wheeled and had no resistance
The shafts did not free wheel however they moved smoothly
No movement in any of the bearings from what I could see
:dispirited:

Those are not the wires going to the motor but the signal wires going to the drives. The motor wires are connected to the black drives from your first post picture (A+; A-; B+; B-)

So this is where I am at. Ive traced the wires back from the motor.....

1 - Wire direct from Y axis motor, Green, Black, Red, Blue which go into White, Brown, Yellow, Green respectively

Attachment 25206

2 - They then go into this relay RXM 24VDC which Im guessing switches between the Y and the 4th, plug in rotary axis.

Attachment 25207

3 - The wires then exit and come into the controller

Attachment 25208Attachment 25208

Just in case anyone is interested...

This is how a vector cut at 150mm/s looks like when its working correctly...

Attachment 25209

Here is what I am getting at the moment, the speeds are marked in the corner...

Attachment 25210

Could you bypass the relay and connect the motor cable directly to the drive? Blue wire to A+; red wire to A-; green wire to B+and black wire to B-

edit: You can also check the resistance between blue and red and between green and black after you disconnect them.

I guess so yeah, unscrew them from above and below the relay and connect them together. Then turn it on and see if we have the same issue?

Insulated crocodile clips and extra wire is going on my Christmas list!

Quote:

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Originally Posted by SweetAs

I guess so yeah, unscrew them from above and below the relay and connect them together. Then turn it on and see if we have the same issue?

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Better if it is possible to unplug directly the black motor cable from first picture and connect them directly to the motor driver.