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Author Topic: Oscillating bit in Z axis to equalize tool wear  (Read 10285 times)

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Oscillating bit in Z axis to equalize tool wear
« on: September 19, 2011, 01:25:41 PM »
Hello,

I have a grinding application in which I use a cylindrical diamond coated bit to cut 2D parts from sheet stock that must be ground, not milled.  The sheet is a laminate and one layer of it is very hard on the diamond, stripping it quite rapidly.  I can cut more parts before a tool change is required if I oscillate the bit up and down.  At present I do this by post-processing my g-code to add the additional movement, however this carries several disadvantages for me.  It would be convenient to simply turn on a function from within my g-code that causes Z to oscillate up and down about its current position at a specified frequency and amplitude.  Can anyone suggest a means of doing this?

Thanks.

Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #1 on: September 19, 2011, 01:41:54 PM »
THis is a process BEST handled by the Post from your CAM it would be a simple process for most CAMs.

NOW there are several ways it can be done inside MACH but it ain't pretty. I will look back thru the project notes and check it out again.

How complex is the average code you are working with? Do you use offsetts or Tool comp?

(;-) TP
Re: Oscillating bit in Z axis to equalize tool wear
« Reply #2 on: September 19, 2011, 02:32:50 PM »
Thanks for your reply.

My user name is Mach3noob.  There's a reason for that.  CAM program?  We don't need no steenkin' CAM program!  Seriously, Ive gone from coding entirely by hand to using a very nice but quite simple 2D CAM package that does most everything I need but certainly doesn't have this oscillation capability.

My code is quite simple, and at present I do use offsets or tool compensation.
Re: Oscillating bit in Z axis to equalize tool wear
« Reply #3 on: September 19, 2011, 02:34:41 PM »
Sorry, that should have been, "at present I do NOT use offsets or tool compensation."

Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #4 on: September 19, 2011, 04:50:35 PM »
What is the name of the CAM?

(;-) TP
Re: Oscillating bit in Z axis to equalize tool wear
« Reply #5 on: September 19, 2011, 06:30:09 PM »
SheetCAM.  Allthough it has no oscillate feature, I just found out you can write your own post processors for it, and I believe you can access the current feed rate as well as arc and line parameters from within the Lua programming language in which they are written. That is enough info to break the lines and arcs into sections with ascending and descending Z movements to create the desired oscillation. 

Still, I find this a PITA compared to simply turning oscillation on and off as needed.  After all, the nature of the thing is to have Z oscillation that is independent of X and Y; breaking up each X/Y move into a variable number of pieces that depends on the feed rate feels inelegant, like forcing a square peg into a round hole.  And if I ever switch CAM packages, I'll have to do it all over again.

Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #6 on: September 19, 2011, 07:24:11 PM »
That I am aware of there is NO CNC controller that can do z oscilations as a standard motion. (;-) There is NOT a gcode  for it either.

Yes Scam could do it easy enough. You could set the frequency and amplitude based on OnARC()  and ONmove() and then compare to units travel to set the Zdepth to oscillate with xy movement. Then on OnPenUp() you could make sure it  raises Z back to safeZ before it does a rapid.

Like I said CAM is where it is normally done.

Just a thought, (;-) TP
Re: Oscillating bit in Z axis to equalize tool wear
« Reply #7 on: September 19, 2011, 08:06:59 PM »
Okay, I can take a hint - you REALLY think I should do this from within SheetCAM.  Now just suppose I am truly nuts, and despite this excellent advice, I STILL want to do it from within Mach3.  I would like to trigger some code that will start the Z axis oscillating, and another to stop it again.  I would be content to have the frequency and amplitude hard-coded, as I expect to change these very seldom.  How would you pull it off?  I understand that there is no standard G-code for oscillation, but I was thinking the natural thing to do would be to rededicate and hook a pair of on/off M codes that have no meaning on my machine, e.g. M10/M11 or M23/M24.

Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #8 on: September 19, 2011, 10:52:17 PM »
Normally I would say not possible BUT Mach has a few tricks up its sleeve. I will do some testing to see IF I consider it safe to try it.

Can you  post a SMALL program of the code you would normally run as a test base.

(;-) TP

Offline Hood

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #9 on: September 20, 2011, 02:10:18 AM »
Why not have some sort of mechanical/electrical oscillator on the axis in question then you could turn it on and off with a M code.
I occasionally do work for a guy that makes weird and wonderful electronic gizmos for the oil industry and one of them a while back had an oscillating action to it, cant remember the details but sure it was just similar to a solenoid valve with  a few capacitors/resistors thrown in.
Hood