# Servo running rough



## matthewsx (Jan 23, 2021)

I bought one of these cheap sewing machine servo motors and it seemed fine for a short time then it started running rough at high speed.




So I tore it apart expecting to find a bad bearing but the bearings seem tight and smooth. Now I'm wondering if it might be a problem with the cheap controller. I'm looking for a manual that might specify some kind of tuning operation or anything else that could help. This is the manufacturer but they don't seem to have any more info than the eBay seller.






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I'm pretty clueless on servo operation so anyone who might have insight into this would be appreciated.


John


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## matthewsx (Jan 23, 2021)

Okay, I found my user manual so I guess I should RTFM....

John


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## mmcmdl (Jan 23, 2021)

matthewsx said:


> RTFM....


 Can I guess ?  BTW , we never read manuals .


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## matthewsx (Jan 23, 2021)

mmcmdl said:


> Can I guess ?  BTW , we never read manuals .


Yes,

Read the Favorite Manual.

But it might not be your favorite..........


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## matthewsx (Jan 23, 2021)

Well, that was a short read but I'm no closer to understanding. Just in case someone else wants to check it out.










These little motors are cheap and seem like they would be good for lots of different tool related uses. Just need to wrap my head around it enough to figure out if its broken or just needs tweaking.


John


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## sdelivery (Jan 24, 2021)

More info! Is this a DC motor with brushes?
What if anything are you using for feed back?
Does the drive have a auto tune function?
Where is the gain set at?


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## rwm (Jan 24, 2021)

I just put the 750 watt version on my drill press. So far it has run fine. I have the exact same manual and I have talked with the seller about some of the options. My guess is, you need a new controller, but you could try a factory reset of the controller and see what that gets you. There is a guy in Fl who has new boards for $50.
BEFORE you do this, make sure you know what P17 is set for. You will need to reset it. To enter programming, press P and S at the same time. Then browse up/down thru the functions. 
See the first line under "Special Function" to do the reset.
Also, you might want to play with P6 and P8. I set them as low as possible. P8 set to 0 coasts to a stop and saves wear and tear.
Let me know if I can help.
Robert


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## rwm (Jan 24, 2021)

Here is a cleaner version of the manual:
R


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## rwm (Jan 24, 2021)

I have another document that indicates that for the 550w motor p17 should be set to 8. I guess it depends on whether you have the 6 pole or 8 pole which you probably don't know. See how it is set now. 
R


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## markba633csi (Jan 24, 2021)

As far as I know that is a dc brushless motor which is a multiphase ac motor with a permanent magnet rotor.  So the controller is actually a small VFD.
If it worked initially then the controller may have developed a malfunction.  You might try contacting Pete at
www.olduhfguy.com and see if he can service them
Worst case try to get a replacement or get your money back thru your credit card company
-Mark
You would really need a scope to do any serious troubleshooting- and a schematic


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## Boswell (Jan 24, 2021)

have you been cutting any ferrous metal? Any chance you have iron filings working there way into the permanent magnets?


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## matthewsx (Jan 24, 2021)

sdelivery said:


> More info! Is this a DC motor with brushes?
> What if anything are you using for feed back?
> Does the drive have a auto tune function?
> Where is the gain set at?


Brushless servo


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## matthewsx (Jan 24, 2021)

Boswell said:


> have you been cutting any ferrous metal? Any chance you have iron filings working there way into the permanent magnets?


Only aluminum so far


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## matthewsx (Jan 24, 2021)

rwm said:


> I just put the 750 watt version on my drill press. So far it has run fine. I have the exact same manual and I have talked with the seller about some of the options. My guess is, you need a new controller, but you could try a factory reset of the controller and see what that gets you. There is a guy in Fl who has new boards for $50.
> BEFORE you do this, make sure you know what P17 is set for. You will need to reset it. To enter programming, press P and S at the same time. Then browse up/down thru the functions.
> See the first line under "Special Function" to do the reset.
> Also, you might want to play with P6 and P8. I set them as low as possible. P8 set to 0 coasts to a stop and saves wear and tear.
> ...


I did the reset last night after putting it back together, will try hooking the belt up today to see if it's better. Thanks for the other tips, I'll bet it is a setting that I messed up accidentally, it's been a little too long to get a refund so I don't have anything to loose right now.

Thanks,

John


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## matthewsx (Jan 24, 2021)

So I hooked up the belt and have the same issue, vibration above ~1500 rpm. I'm starting to think it may be an alignment issue or something to do with the mounting, it runs smooth as silk to ~2500 rpm without the belt and only vibrates a little at max 3000rpm.

I'm using the cast pot metal mount that came with the motor and when I play around with alignment it seems to move the vibration up and down in the rpm range. It's probably worth the effort to build a better mount with fine adjustment. 

I'm also using a timing belt arrangement, maybe switching to v-pulleys with a round belt would be better?

John


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## DAT510 (Jan 24, 2021)

If It ran ok to start, then something changed.  Since the motor runs smooth when not hooked to anything.  Could it be swarf in the pulleys, damage or swarf in the belt, bearings going bad in spindle and or motor (when side load is applied)?


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## macardoso (Jan 24, 2021)

If it is a tuning problem, you do have access to the tuning gains. I wouldn’t start there but it might help later on.


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## sdelivery (Jan 24, 2021)

DAT510 said:


> If It ran ok to start, then something changed.  Since the motor runs smooth when not hooked to anything.  Could it be swarf in the pulleys, damage or swarf in the belt, bearings going bad in spindle and or motor (when side load is applied)?


Dat510 is on the right track I think. Run your screw assembly off of a drill at various rpms and see how it feels......


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## matthewsx (Jan 24, 2021)

Think I'm going to try changing pulleys and belts to see if that smooths things out, I should probably make a better motor mount first though.

John


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## markba633csi (Jan 24, 2021)

Could be a funny harmonic due to the mount- try working on that first
And the belt drive could be a factor too- you might want to move the motor in closer to the spindle if possible- less belt whip
I like your design- did you make all the slides or buy them? 
-M


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## matthewsx (Jan 25, 2021)

So now I'm looking for some material. I'm thinking 3" x 3" angle would be good 1/2" thick would make a nice bracket for the motor. Any suggestions on where to get such a piece?

John


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## fitterman1 (Feb 22, 2022)

So how did you go?
I've just bought one of these to drive my dbit grinder and want to know if you retained the pedal controller or changed it out for another method.
My pedal controller has a magnet and what looks like a hall effect sensor.
I think these motors have a great future in driving smaller power tools.


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## matthewsx (Feb 22, 2022)

Embarrassed to say I haven't made much progress since the last post. I did get my "new" lathe up and running and will modify or make new pulleys as I don't think the stepped ones are appropriate for this application.

I do think the price point on these things makes them very appealing and will let folks know when I dig back into the control for it.

John


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## matthewsx (May 22, 2022)

finally got a Round Tuit....


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## rwm (May 24, 2022)

Those round tuits work very well. I made a modification to the control circuit so that I can turn it on without turning the speed to zero and also get a greater range of speed control. I can share it if you want? If you bought it from that guy on eBay, it may already have my modification since I gave him the schematic?


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## matthewsx (May 24, 2022)

rwm said:


> Those round tuits work very well. I made a modification to the control circuit so that I can turn it on without turning the speed to zero and also get a greater range of speed control. I can share it if you want? If you bought it from that guy on eBay, it may already have my modification since I gave him the schematic?


I’d love a copy of your schematic. Sure I could figure it out but be better not to wait another year


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## fitterman1 (May 24, 2022)

Do tell Robert


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## rwm (May 24, 2022)

Took me a while to find it!
First you might find the attached manual helpful if you don't have it. It allow you to change the start and stop speeds and other parameters. Also shows the error codes.

Here is my schematic:


This replaces the foot pedal speed control that I assume your motor came with? If not, it plugs into the back of the controller. The pin inputs are also shown on the attached manual. 
My circuit is basically just a voltage divider circuit but the resistances were carefully selected by trial and error. The power switch on the controller is still used as a master power switch. That switch also turns on my work light. The run/stop switch is added. For my application I used the factory switch on my drill press. The speed control is a 1K potentiometer with the signal to the controller coming off the center tap. I mounted this in the controller box for convenience.
You may note that the motor starts when the input voltage is around 2.4volts and hits max at 4.2 volts (delta voltage 1.8v.)  The response is non-linear so I had to buy a reverse audio taper pot for optimum performance. I am assuming all of these controllers are very similar if not identical. I would mock it up on a breadboard first and make sure it works for your controller.


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## matthewsx (May 24, 2022)

fitterman1 said:


> Do tell Robert





rwm said:


> Took me a while to find it!
> First you might find the attached manual helpful if you don't have it. It allow you to change the start and stop speeds and other parameters. Also shows the error codes.
> 
> Here is my schematic:
> ...


Awesome, just what I needed to move forward....

And encouraging to see that it works for your application, should be fine for mine too.

Thanks,

John


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## fitterman1 (May 24, 2022)

Brilliant, should have learnt electronics when younger.
Revision number is exactly the same as mine.
I will get all the components as used by yourself and build and test.
Can't possibly go wrong if we share the same software.
Thank you for your efforts and willingness to share them.
Robert, you should save this data in the downloads section for others willing to use these small motors for their projects.
Best regards


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## matthewsx (May 24, 2022)

After reading another thread I may stock up on them....


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## fitterman1 (Jun 28, 2022)

Finally got all my bits and pieces together along with my act and assembled this for my grinder motor controller.
As per Roberts schematic further back I knocked this up using the suggested resistors, with one change. I used a simple 102 trimpot instead of the C1K potentiometer he used. I adjusted the pot until my preset full speed came up on the fascia tacho and it ran.
Works great.
Resistors are sized 2 watt, the switch is a household light switch fitted to a small box from a local electronics store.


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## fitterman1 (Jun 28, 2022)

More pix.


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## fitterman1 (Jun 29, 2022)

Hopefully it will not get too hot in the box as its a sealed box.
And here it is mounted.right under the front for easy access.


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## fitterman1 (Jun 29, 2022)

matthewsx said:


> So I hooked up the belt and have the same issue, vibration above ~1500 rpm. I'm starting to think it may be an alignment issue or something to do with the mounting, it runs smooth as silk to ~2500 rpm without the belt and only vibrates a little at max 3000rpm.
> 
> I'm using the cast pot metal mount that came with the motor and when I play around with alignment it seems to move the vibration up and down in the rpm range. It's probably worth the effort to build a better mount with fine adjustment.
> 
> ...


John, i think your vibration is due to the timing belt itself. This type of belt really requires an idler pulley to tame it. My G0602 lathe came with one standard and I had the same problem which was causing a dirty surface finish. When I changed the motor to a dc treadmill version i machined the pulley teeth off and machined it to take a ribbed belt where the grooves run the length of the belt. I used the treadmill pulley on the motor.
Like a car belt. All vibration and chatter disappeared.
Cogged belts are fine for timing applications but I don't understand why the Chinese use them on lathes.
You should be ok with the original bracket. For driving a spindle go with a Vee or ribbed belt.
Cheers Alby.


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