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Offline JtheB

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Tool Offset Trouble
« on: February 18, 2023, 01:09:28 PM »
I've followed the Avid/Mach4 tool offset procedure to the letter and still struggling.
Master tool is a 0.25" steel dowel and I've been using the Avid touch plate (1.0000" Gage Block Height).
The master tool baseline seems to be establishing fine and for some tools it seems to accurately gauge the offset.....
But I just got an offset for one of my tools of -10.4847 which isn't even possible on my z-axis.
I'm missing a setting or a step in the procedure that's basing the registrations off some other point....
Any ideas?

Thanks

Offline Graham Waterworth

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Re: Tool Offset Trouble
« Reply #1 on: February 19, 2023, 09:49:44 AM »
We need more details to give an answer:-

Machine type, lathe, mill etc.

Are you swapping tools in a single holder or swapping holders with tools.

What is the setup of the machine

Pictures always help.
« Last Edit: February 22, 2023, 06:36:55 PM by Graham Waterworth »
Without engineers the world stops

Offline JtheB

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Re: Tool Offset Trouble
« Reply #2 on: February 21, 2023, 09:49:27 AM »
Apologies Graham,
Avid CNC, Mach4, S30 ATC spindle
All tools are in their ISO30 holders and mounted in their respective magazine stations.
The largest measurement discrepancies seem to be associated with me having missed Mach4 error code "Lua: Error running chunk" when hitting the "Set Tool" command while measuring offset. I'd restart the entire machine and program, home and get a reliable result thereafter.
There do seen to be some remaining discrepancies though relative to hand measuring with calipers.
Some are off by up to 0.03" by that is probably human error?
Thanks
Re: Tool Offset Trouble
« Reply #3 on: February 22, 2023, 08:57:42 AM »
I would ask Avid to fix the script so you no longer get a LUA error.
For now put your master tool in and call the length offset G43 H# then zero the tool to your work cords.
Once you've done this, jog up and swap tools. Jog the new tool down to the block and compare the work cords DRO to the master tool.
Input the TLO in the tool table View > Tool table
Now that the TLO is in the table, call the new G43 number and see if tool tip work cords zero is the same :)

I'm unsure of Avids TLO setup procedure they recommend but that should work until you get your script fixed.
« Last Edit: February 22, 2023, 09:01:38 AM by GOOMBA »

Offline JtheB

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Re: Tool Offset Trouble
« Reply #4 on: February 22, 2023, 11:05:49 AM »
Goomba,
I will look into this, thank you.
It occurs to me that this may be linked to a pattern I've also noticed of cuts getting too deep.
I'm working with mostly 3/4" baltic birch ply and the initial downcut passes of 0.1" are fine.
Once I switch to the upcut bits the remainder of the cuts seem to be deeper per pass than the 0.03" discrepancy in offset.
The cut stack can easily accumulate to cutting through the bottom of the material and into the wasteboard before the final pass is even started.
Initially I misunderstood how Mach4 was calculating cut depth during toolpath setup (having only been familiar with a different software interface) but I've corrected myself and the issue remains to a degree.

After some research I'm now wondering if my Z-axis is missing steps or something related...
Here are some details which may be unrelated but are worth considering as a whole:
1) My newly assembled Avid has developed a "click" during jogging in the -Z direction. Though only audible during jogging (600ipm) it's cadence seems directly related to screw drive velocity. I've read about some components possibly being loose but have yet to disassemble and inspect.
2) Though I've trammed the Z-axis precisely, when surfacing wasteboard or a slab (rastering left/right on the X-axis), there remains a cut ridge left by the back edge of the bit. The ridges ramp rearward are much more prevalent after each right-to-left pass... which would be a climb-cut in relation to the tool and material. The spindle seems to be rocked back a little so the front edge of the bit is a little higher than the rear edge. There is no adjustment for this plain sans shimming the spindle itself. I don't like band-aid fixes.

I'm prolly gonna bite the bullet and tear this thing down but was hoping to not have to start over.
Re: Tool Offset Trouble
« Reply #5 on: February 22, 2023, 01:13:10 PM »
1:
It really sounds like you're missing steps, you'll hear steppers make some funny noises once in awhile but consistency with the axis also being an issue... I'd say it's missing steps or your ball screw is slipping etc.

2:
I think you've already got this figured out.
Tear it down, sometimes the only way forward is backward!

Offline JtheB

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Re: Tool Offset Trouble
« Reply #6 on: February 22, 2023, 01:32:26 PM »
Thank you for the wisdom and encouragement Goomba.
I'll return with results.

Offline JtheB

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Re: Tool Offset Trouble
« Reply #7 on: February 23, 2023, 10:21:18 AM »
Rebuilt the whole z-axis assembly.
Found the support housing for the brake bearing at the bottom of the ball screw to be a little loose. It's only held in with s spring pin and is apparently not an uncommon source of the "click" noise during jogging. Probably doesn't account for the deep cuts.
Observations update:
1) To be thorough my process is to set the master tool Z and then go down the line of 10 subsequent tools in the magazine.
The "inaccuracy" of some of the tool offsets (relative to my hand measurements) ranges from 0.0085" to 0.0451". Regardless of how many times I run through the process each tool remains off by it's given proportion. At least there's a consistency of outcome in that process...
2) I've had some random traverse stoppages while running the gcode and at one point the spindle decided to randomly open and drop the tool/holder. I've been eclectically shocked recently when touching the spindle casing. May not be related but seems possible the randomness of actions and cutting too deep after initial passes could be attributed to EMI from the dust collection system?  EMI-induced missed steps? I will test the cutting depth again w/o the dust collection running.
The dust collection hose mounts to the cnc machine via wooden brackets though.... maybe the hose gets close enough to shed charge to the spindle?

Offline JtheB

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Re: Tool Offset Trouble
« Reply #8 on: February 25, 2023, 02:22:53 PM »
Sooo.....
After some experiments I'm now suspecting the tool offsets being recorded in Mach4 are not being applied to their given tools.
I even manually changed a tool and used the touchplate to set the tool height above the material and what was supposed to be a 0.1" doc turned out to be 0.44" doc.
I always call for a tool with it's respective height: T# M6 G43 H#
And my post processor is up to date with the required atc code.
What am I missing?

Offline JtheB

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Re: Tool Offset Trouble
« Reply #9 on: February 25, 2023, 02:52:28 PM »
I just realized the Height Offset Active light in not illuminated in my Offsets tab.
The Toggle Height Offsets button doesn't change it's status.

If I load the wxRouter.set screen I can get the offsets to toggle, but not it the AvidCNC.set
What gives?