Machsupport Forum
Mach Discussion => FAQs => Topic started by: eef on January 20, 2023, 05:15:09 PM
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I been searching a lot to find some answers, and guess it must be a FAQ. So I hope someone of you jumps in, and gives the solution :-) This is the issue
The lathe I am working with has a sensor + magnet to get information about the spindle turning.
As far I can see it gives nicely 1 pulse per turn.
We use the threading wizard to input what we want. And then the strange thing happens:
When doing for example a bigger bolt with metric 2mm, it could be just perfect with the G76 string from the wizard.
But as soon we tried to use a pitch of 0.175 and 0.350. we get half of it, so respectivily: about 0,08 and 0.175
We also tried G32. Same effect, everything has half the pitch we want.
What can be wrong here?
We checked the spindle index in config settings. It is set. Low active YES or NO position has no effect.
Somehow it seems it sees two pulses per turn and not one.
BTW all other movements/distances are OK. In G32 and in G76, the Z distances are just perfect. (somehow I guessed it also should be half, but it is not).
Looking forward to get some help. Regards Eef (retired and learning to work modern machinery and software ;-)
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Which threading wizard are you using there are two on a standard install?
Is the feed rate on the G76 line correct?
What happens if you reduce the spindle speed by half?
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Which threading wizard are you using there are two on a standard install?
mm, no luck when showing an image. Please have a look at this link: https://onedrive.live.com/?authkey=%21AFMejeImYzzSy6U&cid=88BBB46E975FEEEA&id=88BBB46E975FEEEA%21210302&parId=root&o=OneUp (https://onedrive.live.com/?authkey=%21AFMejeImYzzSy6U&cid=88BBB46E975FEEEA&id=88BBB46E975FEEEA%21210302&parId=root&o=OneUp) In the manual it is described as: "6.5.4 Threading with a Wizard"
It gives these lines (one for tapered part and one for the main thread).
G76 X2.15 Z1.9 Q1 P0.175 J0.1 L30 H0.15 I29 C0.025 B0.02 T10 (tapered part)
G76 X2.7 Z8 Q1 P0.175 J0.1 L30 H0.15 I29 C0.025 B0.02 (normal part)
To get a workaround, I changed it to:
G76 X2.15 Z-1.9 Q1 P0.35 J0.1 L30 H0.15 I29 C0.025 B0.02 T10 (tapered part)
G76 X2.7 Z-8 Q1 P0.35 J0.1 L30 H0.15 I29 C0.025 B0.02 (normal part)
NB: Pitch from 0.175 -> 0.35 so it is divided by 1/2 and we get the 0.175 we want
NB: And we had to add the - before the Z numbers, because it went in the wrong direction (maybe a bug in the wizard?)
Is the feed rate on the G76 line correct?
See above. The Z-axis numbers are OK. so we get Z-1.9 and Z-8 as exspected.
What happens if you reduce the spindle speed by half?
Everything is slower, but same results.
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What hardware are you using, breakout board etc.
Some pictures would help.
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What hardware are you using, breakout board etc.
Some pictures would help.
for pictures, I will be at the machine in a couple of days/week, so cannot provide those now.
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No pictures etcetera, but we found the answer:
- first we checked if the hall detector did pulse --> YES, worked, and checked the number -> CORRECT
- Input to windows computer --> YES, same results.
- In Mach 3 V2.0, we saw that at:
- at very low spindle speed, the number of pulse were as expected,
- when turning spindel speed up and up,
- the number went up a bit, jumped to to 1/2, went up again, jumped to 1/3 and the same to 1/4
The answer was in the setting of the debounce settings:
Debounce Interval was 500 x40us
Index Debounce was also 500 x40us
After setting both to 50 x 40us, problem solved.
Some recalculations:
At 300 rpm, we saw the pulse was about 1/5 of a turn. ===> 40ms
Debounce setting was 500 x 40 us ==> 20 ms
About 500-600 rpm it started going crazy: a pulse is then about 20 ms, same as debounce time, so it waits till next pulse and so one ==> time in half, etcetera.
With 50 x 40us = 2 ms, we are good for 3000 rpm.
Correct? Regards, Eef
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With hall sensor you may not need any denounce.
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With hall sensor you may not need any denounce.
You are right for the sensor, but there is also some (not perfect wiring) around there what could give EMI.
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which do you use mach 3 card?
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which do you use mach 3 card?
Sorry, no idea, I have to open the control enclosure to check.
Anyway, not relevant for the issue of this thread, what was about a setting of mach3 software