Tormach PCNC 770 Series 3 -- Updated 3/26/2020

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Dave_C
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Re: Tormach PCNC 770 Series 3 -- Updated 2/15/2020

Post by Dave_C »

Also, what is the "reference mark" and is it needed?
The reference mark is what Acorn uses to index the start of the thread! This is also what causes the asterisk to appear when you are looking at the encoder counts and turning the spindle by hand.

If you look at the wire labels of a differential output encoder cable you will see how the index is labeled.

You have to have the index pulse to thread.

Dave C.
Grizzly G0678 Mill ,CNC conversion with Acorn. G4004G Lathe, Mach 3 conversion to Acorn.
briuz
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Re: Tormach PCNC 770 Series 3 -- Updated 2/15/2020

Post by briuz »

Ok. I thought the "reference mark" was some sort of laser engraved mark from the description I was reading.

How about the 6-Bit (06B) interpolation on the read head is 64 and the ring has 72 poles. I am unsure as to how this equates to the "Spindle Encoder Counts" in Acorn: Would this be 4608 (64 x 72) Spindle Encoder Counts or something else?

Thanks!

Dave_C wrote: Mon Feb 17, 2020 1:00 pm
Also, what is the "reference mark" and is it needed?
The reference mark is what Acorn uses to index the start of the thread! This is also what causes the asterisk to appear when you are looking at the encoder counts and turning the spindle by hand.

If you look at the wire labels of a differential output encoder cable you will see how the index is labeled.

You have to have the index pulse to thread.

Dave C.
Dave_C
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by Dave_C »

How about the 6-Bit (06B) interpolation on the read head is 64 and the ring has 72 poles. I am unsure as to how this equates to the "Spindle Encoder Counts" in Acorn: Would this be 4608 (64 x 72) Spindle Encoder Counts or something else?
Hum, not sure just what those specs are saying. The 72 poles makes sense but the 64 on the read head throws me off a bit.

If it is a quadrature encoder, then you get four pulses per line on the encoder so 4 x 72 = 288

It real simple to figure out though. Just wire up the encoder to acorn, turn the spindle by hand one full turn while you have the software open to the "Motor" tab.

F1 setup, then F3 config, then F2 Machine and last hit F2 for Motor and then watch the encoder counts as you turn the spindle by hand one exact turn, or as close as you can to one exact turn.

That reading will be close and you can do the math to get the exact reading. So lets say it read 285. Then you will know that it should be 288!

I'm not familiar with your encoder but I would guess it will output much higher pulse train than 288. Maybe 4,608 or 18,432 (just a guess)

Dave C.
Grizzly G0678 Mill ,CNC conversion with Acorn. G4004G Lathe, Mach 3 conversion to Acorn.
briuz
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by briuz »

I am not sure what it means, either. I didn't order the encoder yet as I don't want to order the wrong thing.
Dave_C wrote: Tue Feb 18, 2020 10:38 am
How about the 6-Bit (06B) interpolation on the read head is 64 and the ring has 72 poles. I am unsure as to how this equates to the "Spindle Encoder Counts" in Acorn: Would this be 4608 (64 x 72) Spindle Encoder Counts or something else?
Hum, not sure just what those specs are saying. The 72 poles makes sense but the 64 on the read head throws me off a bit.

If it is a quadrature encoder, then you get four pulses per line on the encoder so 4 x 72 = 288

It real simple to figure out though. Just wire up the encoder to acorn, turn the spindle by hand one full turn while you have the software open to the "Motor" tab.

F1 setup, then F3 config, then F2 Machine and last hit F2 for Motor and then watch the encoder counts as you turn the spindle by hand one exact turn, or as close as you can to one exact turn.

That reading will be close and you can do the math to get the exact reading. So lets say it read 285. Then you will know that it should be 288!

I'm not familiar with your encoder but I would guess it will output much higher pulse train than 288. Maybe 4,608 or 18,432 (just a guess)

Dave C.
briuz
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by briuz »

Ok. I am confident enough that I got it all figured out and ordered the following from here https://www.rls.si/eng/products/rotary- ... ic-encoder


RLC2IC miniature rotary PCB level incremental magnetic encoder:

Output type: Incremental, RS422, 5V
Interpolation factor: D10 - 100 (20 um)
Minimum edge separation (Frequency): B - 0.5 us (2 MHz) (u is micro)
Reference: A - With Reference

Ring
MR - Axial magnetic ring for RLC2IC encoder
OD 061 - 61mm
ID 051 - 51mm

With reference mark
92 poles

Special requirements
02 - With back adhesion tape


Looking at the website, I was most concerned with making sure the CPR was correct. (All described here: https://www.cuidevices.com/blog/what-is ... pr-and-lpr)

With 92 poles and an interpolation factor of 100, this should give me a CPR of 9200 or a PPR of 2300. (I finally figured this out by seeing their claim of "Resolutions up to 622,592 cpr" with a 76 pole ring and doing some math.)
tblough
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by tblough »

Sorry late getting back to this. What is your max spindle speed? More lines is not always better as you can exceed the 2MHz bandwidth of the encoder port, or the bandwidth of the encoder itself. Centroid has stated that 1024 lines is sufficient for a spindle encoder so I'm not sure you gain anything by going higher, especially when the increased resolution is all in software and not an increase in the underlying physical components. For the RLS Encoders, "counts" per rev is the number of poles in the magnetic ring * the number of interpolated steps between poles. Which, as you figured out, is 9200 for your configuration.

And as has already been pointed out, you need the reference (index) mark.

Looking at the RLS maximum speed tables, a MR061 axial encoder with D10 interpolation and B edge separation has a maximum RPM of 3042rpm. If your spindle top speed is greater than this, you'll need switch to a lower interpolation factor.
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.
briuz
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by briuz »

Then it looks like I should have ordered the D08 read head. I'll see if I can send them a message and change to the D08....

On the low speed pulley the max spindle speed is 3,250 RPM. (I never use the 10k RPM pulleys as a spindle failed on me during the warranty period when I tried it.) If I can't change the order I'll limit the spindle speed to 3,000 RPM's and order the D08 read head at some time in the future.

I think the bandwidth will be fine as if I understand it correctly the frequency at 3,000 RPM's is 460 KHz. (9,200 x 3,000 = 276,000,000 pulses per minute or 276,000,000 / 60 = 460,000 pulses per second)

I ordered it with the reference mark. I was confused about the reference mark as it almost appeared that it is a visible mark that is laser inscribed for some reason.

Thanks!
tblough wrote: Tue Feb 18, 2020 1:40 pm Sorry late getting back to this. What is your max spindle speed? More lines is not always better as you can exceed the 2MHz bandwidth of the encoder port, or the bandwidth of the encoder itself. Centroid has stated that 1024 lines is sufficient for a spindle encoder so I'm not sure you gain anything by going higher, especially when the increased resolution is all in software and not an increase in the underlying physical components. For the RLS Encoders, "counts" per rev is the number of poles in the magnetic ring * the number of interpolated steps between poles. Which, as you figured out, is 9200 for your configuration.

And as has already been pointed out, you need the reference (index) mark.

Looking at the RLS maximum speed tables, a MR061 axial encoder with D10 interpolation and B edge separation has a maximum RPM of 3042rpm. If your spindle top speed is greater than this, you'll need switch to a lower interpolation factor.
tblough
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by tblough »

Nope on the D08. D08 actually has a lower max speed of 1904 RPM. The better one would have been 06B at 9511 RPM, or 07B at 4753 RPM. These are little tiny microprocessors in the readers and the time taken calculating numbers limits the bandwidth. Powers of 10 (the "D") math takes a lot of computing power hence the lower max RPMs for these numbers. Binary math (powers of 2) can be accomplished with shifting and hence much faster to accomplish. That's why the "B" RPM values in the table are greater even though the resolution may be higher than a "comparable" "D" value.
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.
briuz
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by briuz »

Thanks for pointing this out so quickly. I just sent a request to change my order to 06B. Your description makes a lot of sense. I think we need some sort of ordering FAQ on these as I've spent hours reading through things to try to get this right.
tblough wrote: Tue Feb 18, 2020 2:25 pm Nope on the D08. D08 actually has a lower max speed of 1904 RPM. The better one would have been 06B at 9511 RPM, or 07B at 4753 RPM. These are little tiny microprocessors in the readers and the time taken calculating numbers limits the bandwidth. Powers of 10 (the "D") math takes a lot of computing power hence the lower max RPMs for these numbers. Binary math (powers of 2) can be accomplished with shifting and hence much faster to accomplish. That's why the "B" RPM values in the table are greater even though the resolution may be higher than a "comparable" "D" value.
briuz
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Re: Tormach PCNC 770 Series 3 -- Updated 2/17/2020

Post by briuz »

Only a week and a day since the I started the upgrade and the Tormach is back into service making parts. :D
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