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Author Topic: Physical buttons for plasma  (Read 88488 times)

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Offline Davek0974

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Re: Physical buttons for plasma
« Reply #450 on: November 28, 2016, 02:21:55 AM »
What screw pitch do you have on Z?

Needs to be coarse - mine is 10mm i think.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Physical buttons for plasma
« Reply #451 on: November 28, 2016, 03:06:17 AM »
Its only 2.5

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #452 on: November 28, 2016, 03:26:27 AM »
Forgot you are on a servo, maybe its not so critical, stepper driven ones need the coarse pitch so moves only require a step or two to complete - no acceleration/deceleration etc.

Maybe servo does not need it so coarse?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Physical buttons for plasma
« Reply #453 on: November 28, 2016, 03:30:44 AM »
I have no idea Dave but think 2.5mm pitch is about the biggest I can get on an 8mm ballscrew. The reason I have an 8mm ballscrew is it was the one that was on my wee lathes X axis where the motor came from.
I decided as the motor mount/brackets/pulleys/screw was already made up as a unit that I would just use the whole lot. Originally I had intended a bigger motor and a 10mm pitch ballscrew but it was going to be more work.
Re: Physical buttons for plasma
« Reply #454 on: November 28, 2016, 03:45:49 AM »
Would it be possible to change the pulley ratio?
Might be the easy way out.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline Hood

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Re: Physical buttons for plasma
« Reply #455 on: November 28, 2016, 03:52:32 AM »
Was wondering that myself, it is 2:1 at the moment, not sure what I have the driven pulley bored out to but I may be able to swap around so it was 1:2 which would give me 5mm per motor rev rather than the 1.25mm it is at the moment. Whether the motor would be good enough though is another matter as it is a tiny servo, 50w if I recall.

I have also found a lead screw with 8mm lead but not sure how the friction compared to a ballscrew would play with the wee servo. Probably worth a try though as it is dirt cheap and shouldn't need much in the way of alterations.

Offline Hood

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Re: Physical buttons for plasma
« Reply #456 on: November 28, 2016, 04:03:29 AM »
Well just ordered an 8mm lead screw and nut for the princely sum of £4.49 :D
Re: Physical buttons for plasma
« Reply #457 on: November 28, 2016, 04:06:33 AM »
If the Z is dithering up and down that much, isn't there a setting to limit the Z travel? I just did my first CNC plasma work so I am a newbie at this but the one I worked on had all kinds of settings on the screen for THC control. It also wasn't hunting much in the Z. We were cutting at 127 ipm on ~18ga steel which you could actually see warping as we cut and it followed along with out too much drama. It was a stepper motor on the Z with a fairly fine pitch screw.

The system I setup was this one; http://www.vitalsystem.com/portal/cnc/motion/plasma.php

See the screen shot for all of the THC options.


Mike.

P.S. Still suffering from PLASMA envy!!!!!
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline Hood

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Re: Physical buttons for plasma
« Reply #458 on: November 28, 2016, 04:50:53 AM »
No settings for deadband in this THC but from what I can gather, including talking to someone else who makes THC's, is deadband should not be needed nowadays due to the processing power of modern THC's.
 The problem seems to be mainly caused by the way the CSMIO does THC movements, unlike Mach and most other motion controller it adheres to the accel in Machs motor tuning for THC moves. That sounds like the sensible thing to do but it is actually looking like it is not.
 
The CSMIO internal THC does have deadband but I have not used that due to my voltage divider being 50:1 where it would be better 20:1 with the CSMIO.

Re: Physical buttons for plasma
« Reply #459 on: November 28, 2016, 05:32:35 AM »
If you don't adhere to the motor tuning, won't it just fault out the servo drive anyway? If not, crank up the motor tuning!


Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.