Spindle Encoder or resolver?

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02 Apr 2019 04:54 #130133 by Type_Zero_Design
Hey guys,

I'm in the middle of a retrofit on a brother TC225. I have ordered a replacement spindle motor for the machine as a package with drive cables ect.

I originally requested the motor with absolute encoder for rigid taping syncing and orientation. But just got an email that they are recommending a resolver due to the high speeds (10,000 RPM)

Is a resolver sufficent for syncing for rigid tapping?

I'm not very familiar with the resolvers so any input is appreciated.

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02 Apr 2019 06:02 #130137 by pl7i92
Replied by pl7i92 on topic Spindle Encoder or resolver?
the spindel for tapping is not to be run at 10k RPM
is it the right spindle you ordered
it shoudent be greeter then 5k

depending on your control board it is a standard encoder

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02 Apr 2019 11:00 #130150 by Type_Zero_Design
I'm not really sure what your saying. It is unlikely that I would ever try to tap over 5000 RPM I agree.

The spindle motor is 10,000 RPM and will opperate at those speeds when it's milling drilling ect.

I just need to know if a reaolver can work effectively to sync the spindle motor and z axis for rigid tapping using a 7i76e

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02 Apr 2019 15:44 #130159 by Mike_Eitel
Are you sure that you can do rigid tapping, do you have enough Nm on low speed? Or do you intend to do thread milling?

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02 Apr 2019 16:16 #130161 by Type_Zero_Design
Mike,

Rigid tapping should not be an issue it's a 5.5kw spindle with 23nm up to about 3k RPM

The question is will a resolver be accurate enough and interface able with Mesa/lcnc to sync z and spindle for rigid taping?

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02 Apr 2019 16:42 #130164 by biqut2
Replied by biqut2 on topic Spindle Encoder or resolver?
For what it's worth we have a 8k rpm machine here and it has a 4096ppr encoder on it from the factory and it does rigid tapping all day long. Can't comment on the resolver but I wouldn't think that an encoder would have a problem with an extra 2k rpm.

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02 Apr 2019 18:52 #130167 by Mike_Eitel
Ask pcw or study doc of your Mesa manual. They can count quite high, I have something of 2mhz in my greyed cells container.

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03 Apr 2019 16:26 #130211 by andypugh
I think that with filtering off the Mesa cards can track to 10Mhz.

4096 counts at 10,000 rpm = 700kHz, so unless the encoder counts are much higher than that there shouldn't be a problem.

LinuxCNC can use resolvers (all my machines use them) but you need different interface cards (Mesa 7i49 in my case)

Or is the problem that the _drive_ uses the encoder/resolver for commutation feedback? Maybe that is the problem?

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20 Apr 2019 00:12 #131262 by danilom
It might be that the drive has resolver input from motor and outputs encoder signal to the control. Just like my TC211

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03 May 2019 12:40 #132624 by ihavenofish
my tc225 under Linux has rigid tapping working.

the motor is only 6000rpm. the encoder is 1024 line (4096 count) incremental. I do not remember now what speeds I tested, I forgot to film it, but I think I went all the way up to 6000rpm and aside from bad z motor tuning, it worked. it looked crazy doing it :)

this is plain rigid tapping, not sync tapping, which is important. the z is just tracking the spindle encoder, and the spindle is not being used as a c axis like in some peoples setups.

my servo loop had been 1khz -4khz during testing.

the original control ran tapping at 3000rpm - I think this was for torque reasons, as the motor is 3000rpm "base speed' and torque drops off to 6000rpm (like any standard axis servo does). as for the torque, I ran an M12 tap in aluminium for my tests (on the stock control, never cut under Linux). supposedly this is happy tapping M16 in steel and aluminium. its a tapping centre after all! because the spindle motor is a fan cooled axis servo the basic name plate can be deceiving. you've got (in my case) 3.2kw continuous at 3000rpm, 4.1kw for 30 minutes, and up to 10kw for bursts of a few second - which is what tapping is.

if the motor you ordered is not an AC servo, the scenario should be exactly the same, but you will not get anything close to the performance of the original in tapping. They probably tell you to use a resolver because their abs encoder isn't rated for high speeds. I would just go incremental. you don't need an abs encoder though. the brother never had one in the first place.

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