Need advice on cutting sharp corners/ends

[awalt1250]

I was wondering what the best plan is for cutting sharp ends/corners, without the cutter causing the point on the to end pop off during the cut. I'm trying to cut a dog silhouette and when it gets to the ears, the corners of the ears always come off. I'm using a 1/4 upcut spiral in 3/4" material.

[scottp55]

Andy, can you please post a pic, with feeds,speeds, depth of cut and direction of cut etc. to help us out. My first thought is to get away from up cut, but need more info. Oh, exact bit used also.

[steve_g]

Andy...

Random thoughts...

I’m assuming you’re cutting in wood and the ear tip is splitting off with the grain of the wood...

1. Are you cutting in a climb mode? This mode has the least propensity for chipping with the grain, although it isn’t the smoothest cut in our arsenal.
2. Can you reorient the part to not have the ear tip with the grain crossing the short direction? This might fix the ear but cause issues other places...
3. A down cut bit will let the remaining uncut wood support the cut portion above...
4. You may have to modify the ear to be better attached to the body of the dog... less fragile.
5. How aggressive are you cutting? You may have to take shallower step downs.
6. How are you holding the material down? Perhaps some double stick tape under the ear will support it better.

SG

[awalt1250]

These are the areas that are breaking off. Speeds and Feeds: 1.0 in/sec feed and plunge; running at 14K on the spindle.

My initial thought was that the points are too sharp for this type of work

[srwtlc]

Those aren't going to work nice no matter how you orientate the grain. Along with the others suggestions, make sure that 'Sharp External Corners' is not selected (see attached pic). This will allow the toolpath to kind of roll around the corner instead of a sharp direction change. The finished cut remains the same, but it's gentler on the corners. You can see the difference in the toolpath preview when toolpaths are shown.

You can node edit the corners to have a slight radius to them.

Try a compression spiral. Leave some allowance on the edge and bottom with the first pass and follow up with a full depth profile pass with no allowance. I generally run the first pass a bit faster with lower RPM to limit heat on the cutter (larger chipload) and then a slower higher RPM final clean up pass.

[scottp55]

Andy, Used Scott W's advice(except for compression bit) on a sharp unsupported corner we were having problems with. Toolpaths got rid of most of it and editing a 1/16" radius onto it got rid of the rest. Running a full depth .015" skin pass also got rid of "waterline" chatter marks, and saved a lot of sanding as well as a better quality cut. With 3 cuts/bits we had to leave .02" skin and reverse cut direction, but we also went WAY aggressive on the roughing cut and wound up getting a better cut faster. Added a whole different folder in database for full depth/skin passes which really speeds up drawing.