Spindle index / slotted disc

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Spindle index / slotted disc

Postby Robertspark » Mon Jul 16, 2018 10:11 pm

Very easy question to answer I suspect....

I am the owner of a old cnc lathe which is to be upgraded

It has a spindle with a 100 slotted disc AND an index pulse (single slot).

I was thinking about putting a quadrature encoder on it, but I thought I may as well use what it has, given its going to be a PIA to install cheap encoder, with belts and timing pulleys (+ any possible error they induce with spindle rpm fluctuation)

So, question is:
1) is this sufficient for spindle sync for threading? G33 (yes I know turn is not supported, a spindle is a spindle....) :roll:
2) PID needs an A&B channel + an index signal...... do they have to be quadrature..... or could I just invert the 100ppr signal ;)

http://www.denfordata.com/downloads/for ... s-list.pdf
http://www.denfordata.com/pdfs/Orac-Pro ... es-OCR.pdf

Thanks as ususal

{I thought I'd set it up with Mach4.... err with someone elses motion controller (pokeys).... I have been exploring Centroid Acorn (given UCCNC doesn't support turn (hint! :roll: :shock: ).... but then I kind of thought I'd try to use it as a uccnc turn test bed too, in case you see any of my posts anywhere}
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Re: Spindle index / slotted disc

Postby cncdrive » Mon Jul 16, 2018 11:16 pm

1.) G33 is spindle syncronised thread cutting on XZ axes, so yes it is for lathe work.
2.) For G33 and G76 thread cutting you need to have a quadrature encoder A and B and Index channels. And there must be one index signal per turn.
Yes, the signals have to be quadratue otherwise the controller could not detect the direction of rotation which could lead to issues.
Index only threading is not supported, because it is too unprecise solution in our opinion.
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Re: Spindle index / slotted disc

Postby Robertspark » Mon Jul 16, 2018 11:49 pm

Thanks,

Do the signals HAVE to be 90 degrees phase shifted?

Could I just use two optical sensors on the same encoder disk and their exact positioning is not important as long as they are not in sync?
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Re: Spindle index / slotted disc

Postby cncdrive » Tue Jul 17, 2018 12:03 am

Well, there is no need for exact 90 degrees, but the frequency limit will be lower as the more shift from the optimal 90°
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Re: Spindle index / slotted disc

Postby Battwell » Tue Jul 17, 2018 12:19 am

I know jb Cnc ( on this group) has done it by adding another opto
Using uccnc

https://youtu.be/GnDHt4IQdpo
Uc300eth on router and mill
If they say it can't be done- I find a way!
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Re: Spindle index / slotted disc

Postby cncdrive » Tue Jul 17, 2018 12:27 am

We've added an encoder on the motor and an opto and half disk for the index, because however the encoder has an index channel, but the gear ratio between the motor and encoder was not 1:1

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Re: Spindle index / slotted disc

Postby Battwell » Tue Jul 17, 2018 12:31 am

Picture doesn't show up
Uc300eth on router and mill
If they say it can't be done- I find a way!
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Re: Spindle index / slotted disc

Postby cncdrive » Tue Jul 17, 2018 12:33 am

It's not a picture, it is an embedded youtube video. :)
It shows up fine at me. Here is the link: https://www.youtube.com/watch?v=_PVYLCoFoK8
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Re: Spindle index / slotted disc

Postby Robertspark » Tue Jul 17, 2018 6:23 am

Thank you both, I'd seen the cncdrive one before and was very impressed with the synchronization even by hand turning the spindle (but I guess it is encoder feedback). :D

I guess the bit the confuses me is you obviously ran G33 / G76, but to start the spindle you used M3, and to stop it you used M5..... I would have thought that M5 would have cancelled the G33 / G76 and encoder feedback?
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Re: Spindle index / slotted disc

Postby Battwell » Wed Jul 18, 2018 4:58 pm

https://forum.jbcnc.se/viewtopic.php?f=3&t=7

i found his page with full info - shows sensors and signals
Uc300eth on router and mill
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