Ridges in v carve

[COWBOY1296]

What causes these ridges in V carve. This is a 90 degree v bit. It shows up not only on the preview but in the carving as well. I would have done a more in depth search but was not sure how to searach

[martin54]

if it shows in the toolpath preview than have a look at your stepover settings, think it might be something to do with the fact that your are using a pointed tool

[ohiolyons]

Could you attach the file?

Interesting the lines don't appear on the inside of the stars.

[adze_cnc]

I expect that the artifacts on the preview image are the result of mathematical rounding errors. Note how those “waterlines” only appear on the convoluted leafy portion and not on the flat planes of the star.

For the physical cut I’d expect that one or more of the old standbys probably apply:

• the bit is not physically 90 degrees but is slightly off (e.g. 89.5 deg or 91 degrees)
• the bit doesn’t come to a sharp enough point (i.e. bit wear) a good loupe will help in inspecting the point
• the feed rate is too fast
• machine flex

[ohiolyons]

If I look real close at your image, the areas with ridges appear to be extremely faceted.

I'm betting that the area of concern was an imported jpeg with a lot of segments.

This would explain why the stars (stars weren't imported) are smooth and flowerily areas have ridges.

If it was an imported STL it was a very low resolution file and the imported STL file has ridges too.

[Tailmaker]

For the physical cut I’d expect that one or more of the old standbys probably apply:

..............
[*]the bit doesn’t come to a sharp enough point (i.e. bit wear) a good loupe will help in inspecting the point
..............

I found that bits with a rounded tip may leave less prominent waterlines. Problem with really sharp and tippy bits (like the CMT Laser Point) is that the surface cutting speed at the very tip is almost zero (since the cutting radius goes to zero) and the flute is not well defined at the tip. That means the tip is not really cutting anymore but dragging and ripping the wood fibers.
My own best recipe for a smooth vcarve is to "rough" the carve with a normal v-bit and step-down as needed and then remove any waterlines by "finishing" with a large 1.5" diameter v-bit of same angle, going to full depth at once and maybe 0.02" deeper. These large bits are cheap on the Internet and cut actually quite well but usually have a 6mm shank (not 1/4").

As for the artefacts in the simulation, well, I have no idea.

[adze_cnc]

My thought re: not sharp tip is that you are telling the software that the tip diameter is 0 but when setting the tool length either manually or via a touch plate the bit is behaving as if it has a flat end. Thus setting the length of the bit too short.

[COWBOY1296]

production time is not important to me since this is a hobby. i was cutting with a short pass depth. i think that each path is seen in the first photo. to clean out the bottom of any v carve i always make a second pass going as deep as i can per pass. i generally cut v carve at 18k at a slow feed rate. here it is with no first tool path, no ridges.

[ohiolyons]

Please post the file

[COWBOY1296]

IT is actually a 3-d file. the file wont post because it is too big. the v carving is done on top of a dome shaped component but here is the eps file.

[COWBOY1296]

every time i increased the pass depth the preview showed a reduced number of ridges

[sharkcutup]

First may have been due to acceleration/deceleration and/or feed rate being to fast along that area.

by ohiolyons

Please post the file

Probably can't post file.

Really ought to be careful requesting files which may have 3D models in them due to copyright infringement.

Sharkcutup

[Adrian]

I expect what you're seeing is the compromises that have to be made machining a piece with a fixed Z axis when the surface isn't at 90 degrees. To maintain a true v-carve the z would need to rotate to match the curvature of the dome. It can't do that so I think it's a compensation effect at each pass.

[COWBOY1296]

the only 3-d purchased component on the actual file was a rope around the border. the above posted eps file is one that i downloaded from brands of the world (i think) years ago. i may have made some improvements to it, but it is all yalls if you should want it.

[COWBOY1296]

Problem solved at least for future cuttings: give Adrian a cigar. I used the tool to cut out components with in a vector, replaced it with a flat component using the same vector. recalculated and like magic no ridges. thanks for your help.

The reason that i use a dome shape with this file is because i always cut from stock that is 1.7 inches thick. my shape for my rope is always .65. so the seal would be cut close to .7 inches beneath the surface with out the dome and i hate making sawdust when not necessary.