3D Finish Strange Results

Making good headway trying to create a moose in CC Pro. Good at least for CNC novice, I hope.

For testing / learning I picked up a piece of 2x10 Southern pine to play with. Way cheaper than cherry or maple.

A couple hours rough cutting yielded the following:


Lots of fuzz and a lot less wood on the table.

FYI, the “carving area is 13.5” wide. The center “bowl” is 1/2" deep and the moose is .5" thick. All more or less.

I also tried using a 1/16" Tapered Bit to finish the rim with the stars. Bad choice given the surface area. Ran complete 3D Finish using 1/8" round nose and either .03 or .013 Stepover at a 135° angle. Not certain which. I Couldn’t stand watching the entire 4 hour run, but it was certainly interesting to watch for Periodically. When it finished, this is what I had. It even gave me time to fix the switch on my Shop Vac!

Very happy initially. Figured a little light sanding or a second pass at 90° to the first would finish it. Haven’t done that yet, because looking closer, this is what I saw:

Small ridges about 0.11" apart (steel rule is in tenths) separated by three much smaller ridges. When the job was running, all I could tell was that that bit moved over a tiny amount on each path. Repeatedly!! What caused this?

The cd2 file is nearly 9MB so I couldn’t upload it.

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Interesting. No idea what caused it. The ridges look to be closer to 1/8" apart. They also are not parallel to the direction of cut, and appear to be a few degrees off. But the spots where each pass is off does seem to be parallel with the XY axes of the machine. ???

It could be a slight discrepancy in the 3D model when it’s interpreted for the 3D toolpath. Can you share the .nc file? We could simulate it in a 3rd party simulation like Camotics, NCViewer, et.al. to see if the anomaly is in the toolpath.

I assume that part is a “flat” 3D component. So a way to avoid it would be to cut that portion of the job with a 2D path, and only cut the moose & stars with 3D. You would offset the outer boundary of the moose by 1/2 dia of the ball mill plus a tiny bit. Use the offset vectors as the boundary for the 3D path. And use the original vectors as the boundary for a flat pocket. This would also give you a nicer wall between the raised edge & the center pocket.

Everything you see was modeled / cut using 3D. The only flat area is on the rim where the stars are.

The rough cut was horizontal, of course. The Fine ran NE - SW. All parallel. I figure the grain could cause a little deflection some places but this looked like fancy corduroy to me. I had one idea about 2:00 this morning.

If I inadvertently gave it a 0.xxx stepover rather than a 0.xx stepover, could whatever rounding the system does have periodically moved a step just a bit farther?
Example:
Stepover .013 @ 45° yields an X and Y axis movement of 0.01838477 etc

Depending on what the system does with that unrounded number I can somehow see the possibility of it rounding entering into the rounded step movements at a consistent interval, which is what I think I see here. Just don’t know how to deal with it.

As you suggested, I’m attaching the Finish NC file
22 - Interior - Finish 1-8 Ball - 135°.nc (2.9 MB)

It looks like the striations are present in the G-code:

Could you try re-making the 3D Finishing toolpath at a different angle? If the striations are still present and show at that different angle it would seem to be a problem in the G-code generation/calculation — if they are still present at the original angle that would point to a problem in the 3D model/pixel image.

The only time I saw a similar pattern was when I used 0.25mm ball-ended cutter on a raster finishing toolpath. The fine furrows look like they are a product of the stepover of the ball-ended finishing cutter. The angle of that finish is a bit mystifying and looks as if it does not belong there.

My solution to these kind of finish markings was to stop using a raster finishing toolpath and use a circular toolpath. That means the cutter is not replicating a linear pathway and just moving in one direction according to the set stepover. The circular finish from inside to outside places the cutter tip in a new spot in X & Y directions for each pass.

If you had some scrap, you could try adjusting the stepover. The furrow pattern suggests that the stepover was set to 100%. Has the c2d file (toolpaths) become misaligned in some way before you saved it?

The roughing pass could use some help. What wood are you machining? For roughing I generally use a 1/4 x 2 flute straight edged cutter. I set stepover to 50% and stepdown to 1mm with a feed speed of somehwere between 1000 ~ 2000 mm/min at 18,000 RPM. The attached image shows a roughing pass in olive wood.

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Will do some testing, probably next week. Heading out of town for a graduation.

On roughing, I used a 1/4 endmill with 50% stepover. For the test, I’m using Lowe’s finest Southern Pine - 2x10. Mostly concerned with the modelling function at this point - is everything shaped and positioned right? I deliberately choose to run the Finish at 135° anticipating a final Finish at 90° to that.

The weird Finish pattern was NOT expected.

To clarify the closeup picture, what it shows is a raised ridge separated by several smaller raised ridges. More testing will come next week.

Please would you clarify this statement for me.

Do I understand correctly that you set the finishing pass to carve at 135°?

I used NC Viewer to look at your file. It shows the file as it was cut. The attached image displays the file with the curious ridges at the angle to which you set them.

The question is, if the 3D Finishing toolpath was regenerated would the ridges still show? If so, would they show at the original angle or a different one?

@QCDvacuum What CAD package do you use to generate the circular finishing pass toolpath?

I don’t have an answer without running the file myself. If the angle was set to 135°, there would be no reason for the feature to be positioned elsewhere. Possibly the stepover is the cause of these ridges but I do not know enough about GCode to analyse that aspect of the file.

Carveco Maker ($18 per month) and the toolpath is spiral in a box.

EDIT: Spiral in a box mp4 file… short video clip to download from my dropbox

https://www.dropbox.com/t/RNWDG3SYvIi6DJj6

Finished file:

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Looking at the moose with my son, we noticed that while all the bowl surfaces consistently have the higher ridges, the rounded moose body and the rack only has nice neat fine lines. Go figger.

My suggestion is to check the stepover setting of your finish cut is what you intended it to be. Please explain to me the purpose of the 135 degree setting for the finish cut and what you had hoped the outcome would be. I don’t understand why there was a need to specify this setting.

What I have found in doing relief carvings, is that you need 2 finishing passes: The first across the grain and the second along the grain, so that any tooling marks aren’t as visible. Both finishing passes should be about 10% step over.

This is an example I’m just finishing.

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That would make for an interesting clock face.

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Ran 2nd Finish Path today. Wood may may shrunk slightly over the weekend. Reset “Z” down by .006

Not impressed by results. Bowl had strange cutting. Set to 45°. Ran for about two and a half hours.
Cuts over moose appeared reasonable, but not so for the cuts on the bowl in front of him. See picture


Notice the wider ridges this time. Could it be that it doesn’t like doing concave surfaces but convex or flat is OK? The passes over the moose look fine. Ditto for the rim where the stars are.
23 - Interior - FInish 1-8 Ball - 45°.nc (2.8 MB)
Will attach the NC file.

Intend to create simplified version of this and will start testing with that tomorrow with any luck.

Upload your .c2d file?

Does the 3D preview in it show this?

The G-code matches the cut, so no mechanical issue:

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CC Preview doesn’t show the weird path at all. Tried using both .06, .03 and .013 stepovers and nothing looks at all strange.

Finished running East West Finish with .06 stepover and it came out clean. Running 90° at the moment, with .013 stepover. Thirty minutes in and it looks good. Apparently the gCode generator doesn’t like the diagonals. Will be tomorrow before that gets tested.