Can't get lathe to Feed

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08 Aug 2021 14:28 #217235 by rider-83
Replied by rider-83 on topic Can't get lathe to Feed
The original issue earlier in this post was the lack of inputs, so this was Andy's solution to use one sensor.
I've got it to feed now by making a few changes, but it will only feed in M3 not M4, I assume because M4 is a negative rotation value.
Also, the actual feed rate looks to be at maximum (near G0 speed) not at the 0.1mm per rev I would expect to see.

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08 Aug 2021 14:35 #217236 by rider-83
Replied by rider-83 on topic Can't get lathe to Feed
I'm beginning to wonder if I would be making life easier for myself if I did add an extra sensor.
I notice on the encoder wheel we have the 100 slots and an additional outer slot.
Am I correct in saying the 100 slots are for reading velocity, and the single outer slot is a strobe for screw cutting?
Is this strobe slot what the 'Z' index pulse looks for ?

Would this be a far more simpler in proven exercise?

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08 Aug 2021 14:41 #217239 by PCW
Replied by PCW on topic Can't get lathe to Feed
The 100 slots are for reading velocity _and_ spindle position feedback
during threading. That is, the Z motion is "geared" to the spindle rotation
by LinuxCNC during threading. The index pulse is used to start synchronized
motion at the same angular position each pass.

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08 Aug 2021 14:49 #217242 by Aciera
Replied by Aciera on topic Can't get lathe to Feed
If 'spindle-at-speed' does not go true for M4 you might want to use the absolute values tor the 'near' component input.

net spindle-cmd-rpm-abs <= spindle.0.speed-out-abs
net spindle-cmd-rps-abs <= spindle.0.speed-out-rps-abs

Not sure which one you are using now (rpm or rps).

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09 Aug 2021 09:37 #217304 by andypugh
Replied by andypugh on topic Can't get lathe to Feed
Note that with the LinuxCNC "master" (development) version you can use a single IO line and use missing-tooth index:

linuxcnc.org/docs/devel/html/man/man9/encoder.9.html

This is a new feature, added since this thread started.

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09 Aug 2021 09:41 #217305 by andypugh
Replied by andypugh on topic Can't get lathe to Feed

Also, the actual feed rate looks to be at maximum (near G0 speed) not at the 0.1mm per rev I would expect to see

Did you set the F-number to 0.1 and mode to G95? 
G95 F0.1

Is spindle.0.speed-in scaled in revs per second? If it is rpm then you might see that problem. 

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09 Aug 2021 09:56 #217307 by rider-83
Replied by rider-83 on topic Can't get lathe to Feed
Yes to G95 F0.1

scaled is RPM, not RPS
It was RPS but I changed it because I didn't understand what was happing with an issue earlier on. I will swap it back

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13 Aug 2021 14:02 #217680 by rider-83
Replied by rider-83 on topic Can't get lathe to Feed
I switched back to RPS and used ABS, now we are feeding in G1 with both M3 & M4.
Thanks fella's

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13 Aug 2021 16:57 #217691 by rider-83
Replied by rider-83 on topic Can't get lathe to Feed
I've run some more test and have been successful with G71 in G96 CSS mode.

Next is to get a functioning G76.
I've wrote a small program to test, and the syntax is correct, only the machine now sits presumably waiting for the strobe signal to begin its traverse .
How do I now set up for this signal using ver2.9?

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16 Aug 2021 07:58 #217860 by rider-83
Replied by rider-83 on topic Can't get lathe to Feed
Andy,

Ref: encoder.N.missing-teeth

My encoder disc has 100 slots. Should I blank out two slots and use this method?
Do we leave the 'scale' still set at 100 ?

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