eliminating tool marks on a pocket

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GervRich
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eliminating tool marks on a pocket

Post by GervRich »

Hi, I was wondering if there was any solution to eliminating or at least reducing tool marks when pocketing? Typically use a 1/8 or 1/4 End Mill. Any help would be greatly appreciated.

Thanks Ric

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adze_cnc
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Re: eliminating tool marks on a pocket

Post by adze_cnc »

The flippant answer would be don't cut the pocket in the first place---no toolmarks.

The more serious answer is two questions: what kind(s) of toolmarks are you seeing that you don't want to be seen? Do you have a picture(s) so we can see too?

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Re: eliminating tool marks on a pocket

Post by ger21 »

Make sure your Z axis is trammed perfectly, and try an endmill with a small corner radius, so the tip doesn't dig in.
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TReischl
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Re: eliminating tool marks on a pocket

Post by TReischl »

I know this is heresy, but try doing finish cuts.

Most of us like to cut as fast as we can for all sorts of reasons. I was doing that this morning on a bunch of pockets with a 6mm end mill. After the pocket roughing the sidewalls were a bit rough and the bottom was not spectacular. A .005 finish cut fixed all of that.

I did the rough pocketing at 200 IPM, DOC was 6mm. Then I used an inside profile with a spiral and a pocketing at full depth to clean up the bottom. These cuts were done at 150IPM.

If you are pocketing and you set your feedrate to produce nice smooth cuts on the walls an bottom you are wasting a lot of time not to mention dulling your bit faster.

Edit: I just read your signature line and see you are running a shark. Not to berate your machine but it is not known for its superior rigidity. Taking finish cuts will improve the results a lot.
"If you see a good fight, get in it." Dr. Vernon Jones

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martin54
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Re: eliminating tool marks on a pocket

Post by martin54 »

I tend to use a finishing pass as Ted has already mentioned, hog out most of the material to almost full depth with a large(ish) DOC & a high stepover & then a seperate finish toolpath to ake a small DOC with a smaller stepover & slower feedrate. The 2 toolpaths can use the same bit & output together o there is only one file. Using a bottom cutting bit will also help give a cleaner finish on flat surfaces :lol: :lol:

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Re: eliminating tool marks on a pocket

Post by rscrawford »

The way to have no tool marks is to have a perfectly trammed spindle, a substrate that is securely positioned and doesn't release tension and warp when cut, a heavy, solid machine, and a bit that doesn't flex (either a larger bit, or if you need to use a 1/8" or 1/4" bit then keep it as short as possible in the collet).

Unfortunately with a Shark cnc (extremely light duty machine), you will have a harder time getting perfect bottoms on your pockets. I can flex the router on those with very light hand pressure, so you know it is happening when the router is changing directions and cutting. Compare that to a welded steel gantry with a spindle that I couldn't deflect a thousandth of an inch with all my body weight. But both machines will leave marks if the wood moves or warps during cutting, or if the spindles aren't trammed perfectly.
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GervRich
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Re: eliminating tool marks on a pocket

Post by GervRich »

Folks, Thank you for all the input as I will most definitely try the finishing pass. In regards to what tool marks I am getting, I am pocketing out letters and I am getting the tool path of the pocketing of letters if that makes sense. Hopefully one day I can beef up to a bigger and better machine.

Thanks again
Ric

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adze_cnc
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Re: eliminating tool marks on a pocket

Post by adze_cnc »

GervRich wrote:I am pocketing out letters and I am getting the tool path of the pocketing of letters if that makes sense.
If I can intuit what you are implying does it look like a "zig-zag" / "back-and-forth" path?

If so remember that if this plywood / real wood that the grain has a direction. By cutting against that direction the fibres are "lifted". So you'll get the same effect that groundskeepers at baseball parks with grass fields get when mowing opposite stripes.

See also this table by Ontario (Canada) designer/maker Peter Fleming:

Image

Each square of beech veneer is rotated 180 degrees.

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Re: eliminating tool marks on a pocket

Post by 4DThinker »

Cut your pocket using raster with the grain direction, no last pass, and a small positive pocket allowance (.005" or so). Then follow up with a profile full depth in one pass that cleans up the pocket face.

4D

Mikehell
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Re: eliminating tool marks on a pocket

Post by Mikehell »

Make sure to zero in the exact same spot and with the exact same part if the touch plate.

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Re: eliminating tool marks on a pocket

Post by Rcnewcomb »

Other contributors to toolmarks on the bottom of a pocket are:

Vibration: Check your holddown method. You may need to add more clamps, screws, adhesive, vacuum, etc.

Tool Geometry: For some materials a fishtail end mill gives superior results, but in other materials a fishtail end mill yields a poorer bottom finish.

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- Randall Newcomb
10 fingers in, 10 fingers out
another good day in the shop

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