I’m running a contour toolpath in the shape of a heart. As the tool rounds the lower part of the heart, more times than not, It is producing considerable chip-out. The wood is purpleheart so it is quite hard which does not help.
The generated path is running counterclockwise. I’m taking multiple passes at 0.12 depth per pass with a feed rate of 90 inches/min. I’ve tried as slow as 50 inches/min and it is still prone to chipping. Also, I’m doing a rough cut slightly larger than the final, then running a finishing pass to take the last 0.04". FYI - Brand new 1/4 downcut bit.
Because the bit is rotating clockwise, the cutting action pulls the chips away from the finished product. It seems that if the path were in the clockwise direction around the heart, it would be less likely to chip, as the cutting action would be towards the final product. Is my theory sound, and if so, is there any way to force the clockwise direction of the toolpath in CC?
Yes, it looks like the direction=climb would be the feature I need to change the direction.
I’m not sure if this will solve the problem but would like to try it. About 6 months ago I did a trial of the Pro version to see if there were any features I could use. I didn’t see any (I don’t do 3D carving) so I let the trial expire. I wonder if there is a way to get another trial to see if that will solve my problem (you probably don’t know). If so, I will gladly purchase the PRO version.
Quick and dirty workaround if you don’t need to use this feature a lot:
Create an offset vector from your original heart, by 1 cutter diameter.
Select the offset vector and cut on it’s inside. That will effectively reverse the cutting direction.
Purple Heart like you said is very hard to machine even when using a router table and hand tools.
It may help if you post a picture of your problem.
You can try the following
Rotate rotate your project to a position where a majority of the cuts will be with the grain. This may reduce the amount of the chip out.
If your chip out is in the same area and on the top or bottom of the material you could try flipping your material (this will change the direction of cut from the original setup) and change to a mirror image in CC and try cutting from a different side. I don’t know what else you are machining on the face but this could help if you are not machining anything else.
Slow the feed and speed set router at #1
I have had a lot of luck using a 1/8 down cut bit going slow.
Another thing you could do is set an outside offset of .010 to .015 and do a full depth finish cut.
Chip out in purple heart is going to happen and it even happens when sanding sometimes
Another option is a downcut endmill. If the material is flat to the bed of the machine, then you shouldn’t get chip-out on the bottom. But with the hardness of the wood, you may have to reduce your depth of cut sinch the chips are harder to evacuate.
If you are still getting tearout with a downcut bit, that’s terrible. I tend to use bits on the smaller side, and smaller bit = smaller tearout (if it happens), so maybe do as others have suggested and make your initial cut offset from the final dimension - and get as close as you can to the final dimension you think you can without the tearout affecting it - and then switch to a smaller diameter downcut bit, like 0.125" if the depth you are going would not prohibit it.
Another option that is less desirable is to use a bit with more flutes, so each one takes a smaller piece of wood and if you are not already doing it, point an air-blast nozzle on the end mill and really blow out the chips before they can get re-cut.
Thanks for everyone’s interest and suggestions (all good). I decided to go ahead and purchase CC Pro and use Direction=Climb to reverse the cut directions. This worked perfectly. I have had the same problem on Walnut, but not as bad. I’ve attached 2 images. One shows Conventional and the other Climb. The first one shows the solution. Sorry for the bad photos.
I have had chip out issues with soft wood, typically Aspen. I have found that a down spiral bit as well as spraying the material with shellac prior to cutting works amazing. The shellac easily sands off as well.
