Recommendations for stepper motor debug / repair

Hi all,
I have a home made (not by me) cnc which I have been using for 5 years with no problems. Yesterday one of the stepper motors stopped working so I only have a y & z axis. The motor makes its usual wizzing & whistling noises but the spindle doesn't move. I am looking for someone, preferably in the Britol/Bath/South West area who could troubleshoot & hopefully fix the stepper. I am wondering if it could be the controller though? Any help, advice, pointers gratefully appreciated. The motor is a Sanyo Denki 103H89222-5241.
Thanks.
Steve

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Originally Posted by Cotswold Woody

Hi all,
I have a home made (not by me) cnc which I have been using for 5 years with no problems. Yesterday one of the stepper motors stopped working so I only have a y & z axis. The motor makes its usual wizzing & whistling noises but the spindle doesn't move. I am looking for someone, preferably in the Britol/Bath/South West area who could troubleshoot & hopefully fix the stepper. I am wondering if it could be the controller though? Any help, advice, pointers gratefully appreciated. The motor is a Sanyo Denki 103H89222-5241.
Thanks.
Steve

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Hi Steve

Just for testing you could swap the y or x axis stepper for the z axis and if the z axis works correctly, then you know it is the stepper motor which is faulty. As far as I know, there is no repair you could do and it would be simpler to replace the stepper with a new one. If the same thing happens then check is the connection between your z axis ballscrew and the stepper motor. This could be slipping. After that, check the stepper motor cabling etc. The standard type of fault checking process. Check every element in the connection from pc to z axis.

Hope this helps.

Mike

Could be anything.
Photos and details?
Guessing otherwise!

Thanks for the reply Mike.
The Z & Y axis stepper motors are a lot smaller than the X axis motor and have 6 wires, where the X has 4, with different wire colours, so it doesn't look like a direct swap. I did disconnect the motor completely from the ballscrew & it was making noises but the spindle was still not moving. I know the forum here is full of enthusiasts who know their machines inside & out, but I use my machine as a tool to quicken up production of parts for my business so I don't mind paying someone to fix it for me, it's just finding someone who can.
I am assuming that the motor is similar to a normal motor so can be tested & fixed - the only replacement units I can find online are in the states & cost $900 - so based on that if the motor can't be fixed then I may just get a X-carve.

Cheers,

Steve

Highly recommend you check all mechanical connections first. If the motor is 'whizzing' it could be something as simple as a loose coupling.

If you do get to the stage of replacing the motor, you would probably be better off changing the motor and maybe the driver. Without knowing what driver you have, and how it is wired, then it is difficult to advise you properly. 6 and 8 wire motors can be wired in different configurations and I would GUESS that you have a fairly common bipolar connection where the centre taps of the motor coils are ignored.

As Magicniner says - more details please !

its possible the motors OK and the stepper driver has failed and is only driving one of the 2 coils

a quick web search found a new motor at Newark.com for $378

http://www.newark.com/sanyo-denki-sa...ase/dp/20T1472

103H89222-5241 - Stepper Motor, SANMOTION F2, 1.8° per Step, Circular, Bipolar, 13.2 N-m, 6 A, Two Phase, 0.45 ohm

Attachment 24632
photos & details of the X axis stepper driver will be useful



whats the part number of the Y & Z stepper motors ?

Photo & details of the Y & Z stepper drives will be useful
to work out how the motors are being driven
6 wire unipolar or 4 bipolar with 2 wires not being connected

John

Quote:

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Originally Posted by Cotswold Woody

I did disconnect the motor completely from the ballscrew & it was making noises but the spindle was still not moving.

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Have you run the motor disconnected from the ballscrew? have you tried turning the ballscrew by hand? first check if the screw turns without the motor if it does then check the motor turns and put some weight on it to make a load on it.
If none of this works then time to buy a new one.

Phill

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Originally Posted by john swift

its possible the motors OK and the stepper driver has failed and is only driving one of the 2 coils

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Or a coil connection wire has broken.

Quote:

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Originally Posted by Cotswold Woody

I am assuming that the motor is similar to a normal motor so can be tested & fixed

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If it's just a connection that's externally accessible then yes, but as a rule a dismantled stepper is scrap the instant it comes apart.

I've just broken open the controller box to see what type of driver I have & looks like I've got a blown fuse on the board. Hopefully this is the cause of my problem - if it is I think even I cn fix this one!

But why did the fuse blow?

From what we read down-under, I think it may have summat to do with Brexit?

Just replaced the fuse & fired her up - fuse blew again! The stepper controller is from a Canadian company called Larken automation.

the odds are one or more of the transistors in a H bridge has failed short circuit (NPN bipolar in old designs or FET's in later designs)

a shorted or broken cable would be high on my list of causes

John

Hi John,
Apologies for my lack of knowledge, this is all new territory for me. I have just tried another fuse & the motor is now not making any noise or movement, the fuse is now no longer blowing. I am assuming that the short or break is most likely in the stepper motor itself, if so can I get it re-wound like a normal motor? If so does anyone know a company that can diagnose this & fix it?

not sure how many companies like MASSEY COGGINS LIMITED in liverpool that rewound motors are still in business these days

I expect too many potential customers bought new chinese motors instead of spending as much (if not more) on a rewind

cables that are constantly are being flexed very often break just after a connector or clamp

breaking the current through an inductive load like a motor produces a large back emf that is likely to damage any semiconductor its connected to

after repeated replacement of the fuse its likely that either a transistor or the current sense resistor is now become open circuit

for example if you look at figure 12 on page 14 of the data sheet of the L6208 H bridge
Attachment 24633

the pairs of FET's H1 & L1 or H2 & L2 must never be on at the same time only as that will short circuit the supply

one FET from different pairs can be on
eg H1 & L2 or H2 & L1

if a FET goes short circuit
the current sense resistor connecting FET's L1 & L2 to the negative supply can go open circuit

John

Quote:

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Originally Posted by john swift

not sure how many companies like MASSEY COGGINS LIMITED in liverpool that rewound motors are still in business these days

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Plenty, Browill Rewinds in Sheffield are my supplier of choice, but I don't think they have the equipment to re-magnetise a stepper motor after you've stripped it and killed it ;-)

How big a machine is this?

Without seeing the machine, my guess is the wiring (or connector) to the motor has failed, resulting the in the driver going pop.
Easiest solution would be a suitable new driver, and replace any wiring between the driver and motor that flexes. It's unlikely the motor will of been damaged, but even if it has, a more modern square style motor shouldn't be that expensive.

However, without any photos or details about the existing control box, we can't really offer much advise.
To suggest replacements, we'd need to know what controller is being used, and the voltage the existing drives are using (along with a make/model number or a link to a datasheet so we can see what signals they need/provide).