Pocket depth issue when using multiple bits

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sakle2k
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Pocket depth issue when using multiple bits

Post by sakle2k »

Hi all,

I've cut a pocket set for a 0-degree raster cut using a 1/4", 1/8" & 1/16" endmills, but the smaller tools have cut deeper than the .1" depth selected. All of the bits are upcut and flat bottom. I've searched for posts covering this issue and found a suggestion to use the "Set Last Pass Thickness" setting in the "Specify Pass Depths" property sheet under "Edit Passes". I have never used this before and would like to understand how this should be used when using multiple bits for pocket clearance. Would this help with the issue I'm having? Why would the 1/8" & 1/16" bits cut deeper? BTW I've checked tram and had just resurfaced the spoilboard. The machine is a CAMaster Stinger I.

The link below is a photo of the issue I'm having (I couldn't figure out how to embed a photo, guessing this BB doesn't like https)
https://photos.app.goo.gl/sdAyY5LosgZMu9XB7


Appreciate any help!

Thanks,
Les

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TReischl
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Re: Pocket depth issue when using multiple bits

Post by TReischl »

What you are not telling us is how you are setting the height of the tools in the collet.

As for posting photos? Of course you can, see the little tab down below? Try clicking it and then reading. It will work wonders for you.

BTW, a lot us do not like photos that are posted somewhere else on the internet. They have a way of vanishing and then down the road the post here become useless. By using the ATTACHMENTS tab below the pic is stored on Vectric's servers.
Capture.PNG
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Re: Pocket depth issue when using multiple bits

Post by Rcnewcomb »

Here is a link to the FAQ describing how to upload your file. (How do I upload files or photos to the forum?)
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sakle2k
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Re: Pocket depth issue when using multiple bits

Post by sakle2k »

TReischl wrote:
Sun Jan 16, 2022 7:30 pm
What you are not telling us is how you are setting the height of the tools in the collet.

As for posting photos? Of course you can, see the little tab down below? Try clicking it and then reading. It will work wonders for you.

BTW, a lot us do not like photos that are posted somewhere else on the internet. They have a way of vanishing and then down the road the post here become useless. By using the ATTACHMENTS tab below the pic is stored on Vectric's servers.

Capture.PNG
To set the height of the tool my machine has a FTC (fast tool change) feature so each bit is automatically measured for each tool path that uses a different bit.

And as for the photos, I've done it before but forgot how, lol (I've only posted here a few times). I was looking at the toolbar above the message that only has options to Insert Image which didn't work (which was why I thought it was an https issue) or Insert URL which is what I used. I totally missed the Attachments tab so thanks for pointing it out. I agree it's best to have photos on the server as I've run into the issue you described when looking at older posts and finding the image wasn't there.
Attachments
PXL_20220114_002721434_2.jpg

sakle2k
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Re: Pocket depth issue when using multiple bits

Post by sakle2k »

Rcnewcomb wrote:
Sun Jan 16, 2022 7:46 pm
Here is a link to the FAQ describing how to upload your file. (How do I upload files or photos to the forum?)
Thanks Randall!

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adze_cnc
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Re: Pocket depth issue when using multiple bits

Post by adze_cnc »

sakle2k wrote:
Sun Jan 16, 2022 4:27 pm
Why would the 1/8" & 1/16" bits cut deeper?
Perhaps they are not cutting deeper. Perhaps the material is getting thicker due to wood movement.

sakle2k
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Re: Pocket depth issue when using multiple bits

Post by sakle2k »

adze_cnc wrote:
Sun Jan 16, 2022 9:18 pm
sakle2k wrote:
Sun Jan 16, 2022 4:27 pm
Why would the 1/8" & 1/16" bits cut deeper?
Perhaps they are not cutting deeper. Perhaps the material is getting thicker due to wood movement.
Thanks for the suggestion but I really doubt that. Those toolpaths are being cut maybe 20 minutes after the 1/4" bit finishes the first part of the pocket.

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Re: Pocket depth issue when using multiple bits

Post by Rcnewcomb »

If the problem isn't visible in the preview then it is likely a machine or hold-down issue.

It is easy enough to look at the G-code and rule out that the tool paths are actually cutting at different levels.

I'd look at your material holding method to see if the material is flexing or moving while it is being cut.

I'd also check the machine for something binding or loose in the Z axis.
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sakle2k
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Re: Pocket depth issue when using multiple bits

Post by sakle2k »

Rcnewcomb wrote:
Sun Jan 16, 2022 9:47 pm
If the problem isn't visible in the preview then it is likely a machine or hold-down issue.

It is easy enough to look at the G-code and rule out that the tool paths are actually cutting at different levels.

I'd look at your material holding method to see if the material is flexing or moving while it is being cut.

I'd also check the machine for something binding or loose in the Z axis.
Hi Randall,

I had checked when I noticed this and there are no obvious issues with the Z axis and the workpiece was screwed down. I'm new at this, I just got my machine in June so I'm still learning about reading G-code. But when I looked at the G-code I notice that the Z is consistent at Z-0.100000 for the 1st bit (1/4"), but the 1/8" and 1/16" bits are both less than that - the toolpath with the 1/8" bit varies between Z-0.050000 and Z-0.100000 and the 1/16" between Z-0.033333 and Z0.100000. Why wouldn't they all be Z-0.100000? I've attached a copy of the G-code for the pocket as well as a screenshot of the pocket properties sheet from VCP.

Thanks again.
Attachments
Pocket Toolpath.txt
(1020.98 KiB) Downloaded 36 times
Pocket Toolpath.png

sakle2k
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Re: Pocket depth issue when using multiple bits

Post by sakle2k »

BTW, here's the closeup preview of just the pocket toolpath from VCP.
Attachments
Pocket Closeup.png

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Re: Pocket depth issue when using multiple bits

Post by ohiolyons »

Rcnewcomb wrote:
Sun Jan 16, 2022 9:47 pm
If the problem isn't visible in the preview then it is likely a machine or hold-down issue.
A photo showing your entire piece of wood with clamping methodology would be very helpful.

If you are skimping on clamps and cutting away a lot of material wood can bow due to stress being relieved in cut out areas.

The larger the diameter the greater the potential issue.
So how big is your project?
John Lyons
CNC in Kettering, Ohio

sakle2k
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Re: Pocket depth issue when using multiple bits

Post by sakle2k »

ohiolyons wrote:
Sun Jan 16, 2022 10:54 pm
Rcnewcomb wrote:
Sun Jan 16, 2022 9:47 pm
If the problem isn't visible in the preview then it is likely a machine or hold-down issue.
A photo showing your entire piece of wood with clamping methodology would be very helpful.

If you are skimping on clamps and cutting away a lot of material wood can bow due to stress being relieved in cut out areas.

The larger the diameter the greater the potential issue.
So how big is your project?
The material size is 9.000" x 10.000" x 0.500"]. It's screwed down in all 4 corners to a flattened piece of 3/4" MDF which is held to the MDF spoilboard using 4 t-track clamps. The reason for the extra MDF is that it has an asymmetric hole pattern for dowels that I use for 2 sided projects. The attached photo is of a different plaque design (I didn't take pics of the problem plaque mounted, but basically the same file with just a few changes). This plaque also had the same issue but not nearly as noticeable.
Attachments
PXL_20220113_174802744.jpg

Daniel S
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Re: Pocket depth issue when using multiple bits

Post by Daniel S »

I also have a Stinger 1 and had a issue using 1/4 EM first cut and 1/16 for clean up on (stacked text plaque) that it appeared to be carving deeper, I have the FST for bit changing so I tried to fool the system by inserting a .005 feeler gauge between the bit and FST button and for me it made the difference that I was looking for, I guess what I was doing was changing the Z height by .005 for just that pass.
Dan

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Re: Pocket depth issue when using multiple bits

Post by sakle2k »

Daniel S wrote:
Mon Jan 17, 2022 12:23 am
I also have a Stinger 1 and had a issue using 1/4 EM first cut and 1/16 for clean up on (stacked text plaque) that it appeared to be carving deeper, I have the FST for bit changing so I tried to fool the system by inserting a .005 feeler gauge between the bit and FST button and for me it made the difference that I was looking for, I guess what I was doing was changing the Z height by .005 for just that pass.
Dan
Wow that's interesting. Were you going straight from a 1/4" to 1/16"? (I'm using a 1/8" as well). Did you ever post a question to the CAMheads forum about this?

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Re: Pocket depth issue when using multiple bits

Post by Rcnewcomb »

But when I looked at the G-code I notice that the Z is consistent at Z-0.100000 for the 1st bit (1/4"), but the 1/8" and 1/16" bits are both less than that - the toolpath with the 1/8" bit varies between Z-0.050000 and Z-0.100000 and the 1/16" between Z-0.033333 and Z0.100000. Why wouldn't they all be Z-0.100000?
The smaller bits probably have a pass depth less than 0.1" so it is taking multiple passes to get down to 0.1".

Posting the CRV file would help confirm that.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

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