AC Servo Drives - Driving me nuts!

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tblough
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Re: AC Servo Drives - Driving me nuts!

Post by tblough »

Does it really matter if the encoder is incremental or absolute, differential or serial? It's used for feedback to the motor controller. As long as the motor controller and the motor are matched, it shouldn't matter.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
slodat
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Re: AC Servo Drives - Driving me nuts!

Post by slodat »

ashesman wrote: Tue Apr 13, 2021 5:20 pmThanks for the suggestion. I dont have my notes with me right now but I am pretty sure that Yaskawa drives require a special serial encoder protocol and dont support incremental encoders. I think the Hitachi drives were the same.

If you have a model number that does work with incremental encoders then I will definitely check it out.
The SJ-P1 is their new(est) series of drives. I have the encoder interface for it so I can run the Yaskawa spindle motor closed loop. I have not installed the interface yet. Other priorities. If I recall correctly I saw a converter board somewhere. There is a manual for the Hitachi encoder interface at the link above.

Another note - I emailed Hitachi application support engineers prior to purchasing the drive and encoder interface option card. They answered my questions and were quite responsive.
ashesman
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Re: AC Servo Drives - Driving me nuts!

Post by ashesman »

slodat wrote: Tue Apr 13, 2021 5:39 pm
ashesman wrote: Tue Apr 13, 2021 5:20 pmThanks for the suggestion. I dont have my notes with me right now but I am pretty sure that Yaskawa drives require a special serial encoder protocol and dont support incremental encoders. I think the Hitachi drives were the same.

If you have a model number that does work with incremental encoders then I will definitely check it out.
The SJ-P1 is their new(est) series of drives. I have the encoder interface for it so I can run the Yaskawa spindle motor closed loop. I have not installed the interface yet. Other priorities. If I recall correctly I saw a converter board somewhere. There is a manual for the Hitachi encoder interface at the link above.

Another note - I emailed Hitachi application support engineers prior to purchasing the drive and encoder interface option card. They answered my questions and were quite responsive.
Cool, thanks for the heads up. I will look into it tonight..
ashesman
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Re: AC Servo Drives - Driving me nuts!

Post by ashesman »

slodat wrote: Tue Apr 13, 2021 5:08 pm Have you looked at Yaskawa spindle motors? I know they are not cheap, but used ones are plentiful and they have the kind of characteristics you are looking for. I'm powering the one that came in my mill with a Hitachi SJ-P1 drive and it's working well.
@sodat The SJ-P1 looks like it would be ideal for the job with the encoder adapter. The only think I found in the manual is that the encoder adapter has a max of 200kpps which is less than the 250kpps I need for a 2500ppR encoder at 6000RPM. The pricing is pretty good compared to the current contender at $2000 USD if I can buy from US or $2970 USD from the local importer. Looks like a suitable SJ-P1 would be around $693 USD from https://www.precision-elec.com. I have not dug deep on where the best place is to buy from.

Shame you have not got it installed and going, I would love to hear how it all worked out.

I am slightly worried that it will be the same as the ABB and unnamed VFDs that I have tried though :?
ashesman
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Re: AC Servo Drives - Driving me nuts!

Post by ashesman »

tblough wrote: Tue Apr 13, 2021 5:27 pm Does it really matter if the encoder is incremental or absolute, differential or serial? It's used for feedback to the motor controller. As long as the motor controller and the motor are matched, it shouldn't matter.
The motor already has a differential 2500ppR incremental encoder, so the drive must support that...
tblough
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Re: AC Servo Drives - Driving me nuts!

Post by tblough »

.....unless you change the encoder.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
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Re: AC Servo Drives - Driving me nuts!

Post by slodat »

I’m with Tom, why not look at replacing the encoder?
ashesman
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Re: AC Servo Drives - Driving me nuts!

Post by ashesman »

slodat wrote: Wed Apr 14, 2021 8:43 am I’m with Tom, why not look at replacing the encoder?
I'd prefer not to. It's all nicely built into the motor. Waterproof with mil spec connector and cables back to the cabinet. I have already made the adapter cabling from the mazak connector.

It seems that cheaper drives only support proprietary encoders so I would need to use a proprietary encoder to support them. Otherwise incremental encoder is standard and supported by every drive that supports non proprietary encoders. It is also suitable to wire directly to the oak if needed.

One option would be to go to a lower count incremental encoder to keep within the hitachi SJ-p1 limit.
tblough
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Re: AC Servo Drives - Driving me nuts!

Post by tblough »

It's suitable to dasiychain to the Oak only if you belt the motor to the spindle at 1:1 with a cog belt, otherwise you need another encoder belted to the spindle at 1:1 for the Oak spindle input.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
ashesman
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Re: AC Servo Drives - Driving me nuts!

Post by ashesman »

tblough wrote: Wed Apr 14, 2021 3:53 pm It's suitable to dasiychain to the Oak only if you belt the motor to the spindle at 1:1 with a cog belt, otherwise you need another encoder belted to the spindle at 1:1 for the Oak spindle input.
Yeah, I was planning on daisy chaining when I was going to use the ABB drive as it had no encoder output. This setup has the spindle direct driven from the motor so no belt and only the one encoder on the back of the motor.
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