parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

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rk9268vc
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parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by rk9268vc »

My parts are consistently coming out around 10 thou short in Z. (the machine is milling off 10 thou too much)
I am using the swissi probe app, a touch probe, and a mechanical tool height setter. I am using reference tool height mode, with the probe as the reference tool.
I am probing the parallels in the vice to establish WCS Z0. So in my CAM, the origin is on the bottom center of the part

What I am assuming is going on is that my probe or tool height setter has some pre-travel (probably a little of both, but im thinking mainly the tool height setter)

How do I calibrate this pre-travel out, and where can I adjust it?

I see the setting "Deduct TT pre-travel dist" in the tool offset manager config in the app, is this the setting I want? And is a positive value what I want?
Also, if I change this, do I have to re-probe all my tools, or just the reference tool?

Thanks!
rk9268vc
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by rk9268vc »

so I changed "Deduct TT pre-travel" to 0.01, saved config, and remeasured reference tool, and re probed the WCS. I ran a new part and it made no change to the dimensions. So now what to try?

I know it is not that the tool heights are wrong, because I use 5 tools in this OP, and their geometries all line up, everything is just shifted down in the Z by about 10 thou. Which is a problem because I need to hold +/-2thou for this part

Thanks
swissi
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by swissi »

rk9268vc wrote: Sun Nov 21, 2021 10:40 pm so I changed "Deduct TT pre-travel" to 0.01, saved config, and remeasured reference tool, and re probed the WCS. I ran a new part and it made no change to the dimensions. So now what to try?

I know it is not that the tool heights are wrong, because I use 5 tools in this OP, and their geometries all line up, everything is just shifted down in the Z by about 10 thou. Which is a problem because I need to hold +/-2thou for this part

Thanks
The "Deduct TT pre-travel" is the correct place to account for this situation and should have taken care of the issue unless something else is in play here. Email me a fresh Report of your install and also a copy of the file c:\cncm\probing\ProbeApp.cfg to verify your configuration.

In the mean time, all you need to do is reduce (move up) the height offset value H of the H# that relates to the T# of your TP in the CNC12 Tool Height Offset Library by 0.01". Let us know if that fixed the issue.

-swissi
If you are using Fusion 360, check out my CNC12 specific Post Processor
If you are using a Touch Probe, Tool Touch Off Device or a Triple Corner Finder Plate, check out my ProbeApp

Contact me at swissi2000@gmail.com
rk9268vc
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by rk9268vc »

swissi wrote: Mon Nov 22, 2021 12:56 am Email me a fresh Report of your install and also a copy of the file c:\cncm\probing\ProbeApp.cfg to verify your configuration.
-swissi
find attached


So I changed deduct TT value to 0.01 and saved config. I measured the reference tool to the tool height setter, and reprobed the WCS and it didnt change anything
What am I missing in this process? Do I have to reprobe all the tools with this new value? Do I have to change the vale back to 0 to probe new tools? Where does this fit in the workflow?

"reduce (move up) the height offset value H of the H# that relates to the T# of your TP in the CNC12 Tool Height Offset Library by 0.01"
I dont know what this means, I am not familiar with yall's abbreviations and acronyms. It took me a while to figure out what WCS meant.

Edit, I think I found what you mean but it wont let me change the H of my probe
cant cnage h.PNG
oh but you can change it in here. I changed to -.01 ill give it a try
change h.PNG
Edit: This doesnt work. When I load the probe app to probe it, it resets this offset to 0

Thanks
Attachments
probe app config.zip
(2.36 KiB) Downloaded 5 times
report_E0623479566D-0617214834_2021-11-22_09-19-18.zip
(627.57 KiB) Downloaded 6 times
Last edited by rk9268vc on Mon Nov 22, 2021 12:49 pm, edited 3 times in total.
rk9268vc
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by rk9268vc »

swissi wrote: Mon Nov 22, 2021 12:56 am The "Deduct TT pre-travel" is the correct place to account for this situation and should have taken care of the issue
-swissi
With the offset set to 0, when I measure the reference tool (probe) I get this
tt 00.PNG
Wit the offset set to 0.01" I get this
tt 01.PNG
It didnt change? Shouldnt it have gone down by 0.01? Or am I understanding this wrong?

Thanks
rk9268vc
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by rk9268vc »

still havent figured it out, but I did some tests to see if it could be something else

I measured the probe with the mechanical tool height setter 10 times. The max-min value (range) is 0.0015 with a stdev of 0.00051 (3sigma +/-0.00153)
I took the probe off and put it back on and measured, repeating 10 times. The range was 0.0017 with stdev of 0.000508 (3sigma +/-0.001525)
I used the probe to measure the height of a part 10 times. The range was 0.0016 with stdev of 0.000582 (3sigma +/- 0.001746)

TLDR
Measuring ref tool 10 (probe) with mechanical tool height setter for me will be +/-1.5thou 99.999% of the time (6 sigma)
Probing the height of a part will be +/-1.7thou 99.999% of the time (6 sigma)

I am kind of surprised these numbers are that big, but this still doesnt explain being consistently short 10 thou in z when machining the parts. Especially when using 5 or more tools in the OP, and having all their geometry line up with each other (meaning it isnt just one tool that is off or worn)
(also I have 3 thou of backlash in Z, but am using lash comp)
tblough
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by tblough »

Put an indicator on the table and indicate the Z-direction on the toolholder. Push and pull the toolholder up and down. How much deflection do you have? Is it possible the cutter helix is pulling the tool deeper into the work?
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
rk9268vc
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by rk9268vc »

tblough wrote: Mon Nov 22, 2021 4:03 pm Is it possible the cutter helix is pulling the tool deeper into the work?
That is initially what I was suspecting as well. However, only one of the tools, a 1/2 in 4 flute, even has a helix. The other tools are a 3in fly cutter, 2in indexable face mill, 1/4" chamfer bit, countersink, and drills and reamers.

All of the geometry lines up with each other. For example, I deck the part off with a fly cutter and then am putting a 10 thou 45degree chamfer on the corners, which is comes out to exactly 10 thou, just everything is 10 thou lower than it should be.

The other thing is that I am consistently cutting undersize in the Z, not just this operation, not just this part. And it is repeatable part to part. I am making 10 of each part, and all 10 are within 1 thou of each other, but 10 ish thou undersize from the CAD/ CAM

That being said, I am suspecting the probe or tool height setter to be the culprit, because either have the ability to shift all tools up and down. I just cant figure out how to fix it. My bandaid has been to manually go into the WCS table and bump up the Z origin by 10 thou so I can get these parts out, but this is a pain and not ideal
swissi
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Re: parts are short by 10 thou. How adjust pretravel in TT? (using probe app, probe, and tool height setter)

Post by swissi »

rk9268vc wrote: Mon Nov 22, 2021 4:17 pm
tblough wrote: Mon Nov 22, 2021 4:03 pm Is it possible the cutter helix is pulling the tool deeper into the work?
That is initially what I was suspecting as well. However, only one of the tools, a 1/2 in 4 flute, even has a helix. The other tools are a 3in fly cutter, 2in indexable face mill, 1/4" chamfer bit, countersink, and drills and reamers.

All of the geometry lines up with each other. For example, I deck the part off with a fly cutter and then am putting a 10 thou 45degree chamfer on the corners, which is comes out to exactly 10 thou, just everything is 10 thou lower than it should be.

The other thing is that I am consistently cutting undersize in the Z, not just this operation, not just this part. And it is repeatable part to part. I am making 10 of each part, and all 10 are within 1 thou of each other, but 10 ish thou undersize from the CAD/ CAM

That being said, I am suspecting the probe or tool height setter to be the culprit, because either have the ability to shift all tools up and down. I just cant figure out how to fix it. My bandaid has been to manually go into the WCS table and bump up the Z origin by 10 thou so I can get these parts out, but this is a pain and not ideal
I haven't found any Touch probe that has any significant pre-travel in the axial direction (Z-axis) and most of the Tool Setter don't have one either but there are some that do, especially the wireless model DT02 that is very popular. This becomes a problem when the Height Offset of the Touch Probe is measured with the Tool Setter. Usually the TP has a weaker spring load than the TT which causes a measuring error in the amount of the TT's pre-travel because the TT is not being pushed down by the TP and it will be the TP that will create the trip signal.

You can check if your TT has any pre-travel by placing the finger of a dial indicator on the side of the surface plate of the TT and zero it out. Then slowly lower a tool onto the TT with very small steps until the dial indicator shows a movement. Zero out the DRO of the Z axis at this point and then keep stepping down the Z axis until the TT trips. The Z-Axis DRO will then show you the pre-travel distance of your TT that you need to compensate for in the ProbeApp configuration screen.

P26.PNG
-swissi
If you are using Fusion 360, check out my CNC12 specific Post Processor
If you are using a Touch Probe, Tool Touch Off Device or a Triple Corner Finder Plate, check out my ProbeApp

Contact me at swissi2000@gmail.com
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