spindle encoder

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Re: spindle encoder

Postby cncdrive » Fri Dec 30, 2016 3:21 pm

The UCCNC when the spindle encoder A and B channels are configured then it automatically switches to measure the RPM always with the encoder A and B channels.
When only the encoder index is configured then it uses the encoder index for the measurement.

The loop is not closed, the PWM is output in open loop, the value is what is configured with the PWM min and max. and Spindle speed min and max. and the programmed RPM.
To close this loop there would be a need to add a PID control loop or at least a PI loop with the programmed RPM the input, the encoder the feedback and the PWM the output which is currently not implemented, but we have plans to add this function later.
And running in open loop is not a problem for the thread and tap cutting, because the feed is synced to spindle RPM, to the position of the spindle, so if the RPM drops then the feedrate is automatically adjusted,
so the thread pitch will be still perfect, because the encoder gives enough points, enough resolution to compensate quickly and this is why we don't support single index channel threading and tapping, because that would not give enough resolutions to keep the threads good if the RPM drops fast.
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Re: spindle encoder

Postby mccafferty » Fri Dec 30, 2016 3:50 pm

Sounds like I need to keep the encoder resolution coarse enough that the input won't loose it at high speed. I will plan on 100PPR as you imply earlier that works well on your machines.

Thank you
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Re: spindle encoder

Postby cncdrive » Fri Dec 30, 2016 4:08 pm

Yes, if the encoder resolution and speed are high enough to push the encoder frequency out of the max. which the motion controller can count then at high speeds the Sact value shown will be not correct.
However that will still be only a visual problem and will not cause any machining error, because you won't cut threads and taps with that high RPMs.

And yes, I agree, the best is to remain inside the max. counts frequency and then all will be fine, the 100PPR (400CPR) will be OK with your targeted 500RPM max. spindle speed.
If you will install an AMT102 or AMT103 encoder then you will also have the ability to play and experience with the different encoder resolutions these encoders offer.
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Re: spindle encoder

Postby mccafferty » Fri Dec 30, 2016 6:40 pm

Ok, Thanks
I already have 1000PPR encoders and when I originally found out they would probably be too high, I bought a surplus US Digital Edivide. You set dip switches for the desired division from 1-4096 and it recreates the phased encoder output. I may use that or just buy some 100PPR for a cleaner solution. Since you mention experimenting, I might as well use the divider then I can play with it.
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Re: spindle encoder

Postby cncdrive » Fri Dec 30, 2016 6:50 pm

Yes, these all sounds good options to use, I mean the encoder divider and using a fixed 100PPR encoder.
I've mentioned the AMT102/103 as another option because they are really cheap and we used and sold probably over 10000 pcs of them over the years, so I have experience with them.
We have machines working 10-15 years with these encoders and still working without problems.
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Re: spindle encoder

Postby Derek » Fri Dec 30, 2016 9:51 pm

I'll second the AMT encoders. I have quite a few of them including 2 mills that use them for tapping. One mill has probably tapped 20,000 holes or more with UCCNC and the AMT encoder. Versatile and bullet proof.
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Re: spindle encoder

Postby ger21 » Sat Dec 31, 2016 2:17 am

Vmax549 wrote:I would LOVE to be able to use encoders for FRO and SSO but we do not have the inputs to run them.

(;-) TP


What's wrong with using pots on the analog inputs?
<$5, incredibly simple and easy. If you have a UC300.
This feature alone is worth the $25 extra for the UC300ETH vs a UC400ETH.
Gerry
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Re: spindle encoder

Postby dammogreen » Mon Jan 15, 2018 12:32 am

Not ideal , but it sounds like it would be acceptable to install the INDEX sensor directly on the spindle.... and the quadrature A&B sensors on a motor shaft that is not driving the spindle at 1:1
(Of course with the correctly ratioed ppr in the config.)
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Re: spindle encoder

Postby spumco » Tue Jan 16, 2018 5:33 am

dammogreen wrote:Not ideal , but it sounds like it would be acceptable to install the INDEX sensor directly on the spindle.... and the quadrature A&B sensors on a motor shaft that is not driving the spindle at 1:1
(Of course with the correctly ratioed ppr in the config.)


That's exactly how I have it set up. Index on spindle, encoder on motor, pulley ratio 1:1.56. Rigid taps like a dream.
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Re: spindle encoder

Postby dammogreen » Tue Jan 16, 2018 3:40 pm

Awesome thanks, will make my installation "cleaner"
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