V-bit not cutting to same depth as pocket tool in advance v-carve operation

Hi there. I’m using a Shapeoko Pro XXL with the latest Carbide Create software and a BitSetter, and I’ve set up and run several advanced v-carve operations where the v-bit cuts to a depth a few millimeters above the depth of the pocket end mill. This issue shows up in both the simulation and in the milling operation.

Here’s an example. I’m running an advanced v-carve using a Carbide #201 for the pocket and CIC’s 30-degree VSC30 for the v-bit, using standard settings for both, with the exception that I’m using a smaller stepover for the VSC30 (0.050 instead of the standard 0.2). I’ve seen this same result using different bits, so I don’t think it’s related to the specific bits or settings, though I could easily be missing something. In this case, I tried to make an 8-mm-deep cut. The VSC30’s max cutting depth is 7/16" (over 11 mm) and there’s plenty of room for the v-bit to fit between the letters, so I don’t think any of those things are the issue.

In both the simulation and the actual milling operation, the pocket tool goes down to the full depth but the v-bit does not–it leaves a ledge of equal height everywhere it cuts, even in open corners.

Out of curiosity, after cutting the sign below, I decreased the cut depth to 5 mm in Carbide Create, and I see what appears to be the same height difference between the pocket depth and the v-carve depth in the simulation, though now the “ledge” is over 50% of the height of the letters. I’ve used these same v-bits to do inlays with predictable results, so I’m wondering if I’m misunderstanding something with the advanced v-carve or if possible there’s a different issue. Any help would be appreciated!

Upload your C2D file.

Hi Michael. Here’s the C2D file with that 8-mm advanced V-carve. Thanks for any help!

Example V-Carve.c2d (1.4 MB)

This is really weird. I can replicate the problem in simulation on CC 836. I created a new V Carve toolpath, using a 30 deg and #201, and that one come out fine.

The only thing I can see is that the file was created with CC 835. The changelog doesn’t really indicate anything that would cause / fix this problem though.

EDIT: The V bit is ‘cutting’ consistently about 2.5mm more shallow than the clearance bit. Set the depth to 3mm, and it cut very shallow in the V Bit.

Set the depth to 2.5mm, and it doesn’t cut at all. The toolpath is not empty, it just doesn’t cut.

V Bit Toolpath for D=2.5mm (partial view):

Result:

EDIT 2: Wait, the one I created was fine, now it is broken as well! I haven’t been able to figure what triggered it though.

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I see the issue as well. I replaced the 30° tool with one from my library & it cuts correctly.

Still happening in the 837 beta;

Screen grab of your tool definition?

If I change to one I made for a 30 degree tool:

(see below for a different definition)

then the simulation is as-expected.

Hi guys. Thanks for your responses. Here are the tool details for the VSC30; I used the default settings except for decreasing the stepover. I noticed that the finish allowance is set to 0 in the CIC database, while Will’s setup for the Amana bit has a finish allowance of 2.54 mm. I’m still learning about these variables, but if applied, I would have expected that a 0 finish allowance would result in a deeper cut, rather than a shallower one. Based on Michael’s message above, it seems like something is happening at around the 2.5 mm mark…so maybe it’s related to that?

Not sure why the tool definition I have for a 30 degree tool has 15 degrees for Included Angle — please test carefully before using it — I’ll have to check.

EDIT: There was a bug ages ago (long since fixed) which was halving Included Angle for custom tooling — must have missed fixing that entry (it’s been a long while since I used that tool).

Note that the last time I posted this tool definition, it did have 30.0 for Included Angle:

Hmm, interesting. Temporarily changing the VSC30’s included angle to 15 degrees results in the simulation below; the v-bit now appears to reach the bottom (or very close to it), but there are some strange artifacts on some of the corners of the letters that weren’t there before.

All the Carbide v-bits in my library also have included angles which match the nominal bit angle (i.e., not half), so this might explain why I’ve seen this before with other v-bits when doing an advanced v-carve.

Draw the cut up in profile — is it possible that you are cutting to a greater depth than a 30 degree tool at this diameter can cut? The more acute tool would have a longer cutting flute length.

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Hi Will. That was my first thought as well, but this is an 8-mm-deep cut and the VSC30’s max cutting depth is 7/16" (over 11 mm)–I verified the flute length is 0.4375 in the tool database. In the earlier posts above, Michael and I discussed how decreasing the depth of the advanced v-carve cut doesn’t seem to help.

Regarding the profile view of the cut, can you clarify what you’re looking for (i.e., what I’m aiming for, what I’m seeing in the simulation with the 30-degree included angle, what I’m seeing in the simulation with the 15-degree included angle, etc.?)?

In case this is helpful to see, here is another photo. The (insufficient) cut depth for the v-bit was consistent across the whole workpiece–even when following along a wall in open areas with no other features. While I can’t guarantee my caliper measurement is precise enough to be certain, it does not appear that the v-bit cut laterally all the way to the vector lines, so it’s as if the v-carve operation just stopped before making the final pass and should have cut more both vertically and laterally. (Incidentally, I tried decreasing the depth per pass, which was another difference between the CIC bit and the Amana, but that didn’t seem to make a difference.)

Lie to the program and tell it the diameter is sufficiently greater to cause the V tool to be able to cut at the desired depth?

Thanks for the suggestion! Can you explain more? It isn’t obvious to me why increasing the diameter of the bit would make the v-bit carve deeper, and why the v-carve operation would have worked as expected with the Amana bit (which has the same diameter). Are you thinking the underlying issue is related to that included angle?

Here’s a photo of the bit, so you can see the flute length relative to the cutting depth.

The cut is set up to a depth of 8mm:

a 30 degree tool should be able to cut to a depth of 11.849mm:

Updating the 30 degree tool definition I have to 30 degrees:

also works as expected, so there would seem to be a problem with your tool definition.

I think you have an error in your tool definition.

I use that same 30-degree V-bit from the CIC workshop.
Here’s my tool definition and a screenshot of the simulation results.


Example V-SDGUY TOOL.c2d (620 KB)

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Hi Will. The VSC30 tool definitions are included in the tool library I downloaded from CIC’s webpage, if you want to take a look (STREAMLINE YOUR CNC PROJECTS WITH PRE-CONFIGURED TOOL LIBRARIES — CIC Workshop). I made no edits to this file (just redownloaded and verified), and only changed the default stepover when setting up my toolpaths.

Except for the more-aggressive speeds and feeds, the fact that it uses Imperial units, and the finish allowance, I don’t see an obvious difference with your Amana setup, but I’d love to get your take.

SDGuy, thanks for chiming in. The screenshot you posted doesn’t quite match the definitions for the VSC30; it looks like yours is a 2-flute bit with a larger flute length.

The tool definition in question seems to be:

32,CIC Workshop,VSC30,,VSC30 - 30 Deg V-Groove - 3-Flute - 1/4 Shank,vee,0.25,0.125,0.4375,0,30,3,2,,0,,,,25,50,18000,0.125,,0,15,50,18000

The matching definition for the 30 degree Amana is:

45771,Amana,(30 degree),,Amana 45771-K Vee (30 degrees),vee,6.35,0,12.267,0,30,2,38.1,,1,,,,203.2,1016,17000,1.27,,2.54,20,1016,10000

Putting them together:

32   ,CIC Workshop,VSC30      ,,VSC30 - 30 Deg V-Groove - 3-Flute - 1/4 Shank,vee,0.25,0.125   ,0.4375,0 ,30,3   ,2, ,0,,,,25   ,50  ,18000,0.125,,0   ,15,50  ,18000
45771,Amana       ,(30 degree),,Amana 45771-K Vee (30 degrees)               ,vee,6.35,0,12.267,0     ,30,2 ,38.1, ,1,  ,,,203.2,1016,17000,1.27 ,,2.54,20,1016,10000

and working out the differences other than metric vs. Imperial is left as an exercise for the reader.

Just killing time between giving final exams. Threw them both in excel
The differences appear to be in:
Flute length 0.483 Amana 0.4375 CIC
Number of flutes
Stickout 1.5 Amana 2 CIC
Plungerate 8 Amana 25 CIC
feedrate 40 Amana 50 CIC
RPM 17000 Amana 18000 CIC
Depth 0.05 Amana 0.125 CIC
Finishallowance 0.1 Amana 0 CIC
3D stepover 20 Amana 15 CIC
3D feedrate 40 Amana 50 CIC
3Drpm 10000 Amana 18000 CIC

John (psyching up to be amazingly bored for two hours watching folks take a chemistry exam)

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Thanks John! I shot CIC Workshop a quick email this morning to see if by chance they know the answer; I’ll do the brute-force trial-and-error experimentation if I have to, but I’m hoping someone with more experience than me can spot the culprit or at least make an informed guess to guide that effort.

Good luck to your students!