smooth 8 degree edge taper

[ChrisBWW]

I have a client that needs blanks cut, with various shapes, that has 8 degree sides. The 8 degree side is so that when the blank is used as a mold for clay, it will release after forming the clay. The first run I made a select few shapes cutting the finish pass with a .25" ball nose cutter. It all looked great except it had what looked like a contour map on the edge. This made it hard to get the mold to release. I have contacted a bit mfg. company who can make me a 8 degree tapered edge ball nose cutter (.25" D. to .125 D ball with approximately a .5" cutting surface). I simulated running it on Aspire 4 and it still leaves some contour lines. I have, on the program, tried rough cutting and then running a finish cut pass and finally a .25" mill profile as a final pass. My material (HDU foam) is 1.75" thick. I also am having the problem that the roughing and finishing passes won't cut the full thickness. I have made the component 1.75" thick.
I hope that explains my problem well enough so some smart person can help me with what is probably a simple solution.

[dealguy11]

A couple of suggestions:
1. Create the model using a higher resolution. This should reduce some of the choppiness around the edges. Unfortunately, you will need to actually recreate the components used in your model after you increase the resolution of the model, as the old components were created with the lower resolution and won't gain resolution just by increasing the available number of pixels.

2. Try running a profile toolpath around the model with the 8-degree cutter. If you make the model just a smidgen bigger than required, then run this profile toolpath, it should leave a reasonably smooth profile around the outside so long as your machine doesn't have any movement in it that would create chatter.

3. If you haven't tried the "add draft" function, give it a try. Aspire struggles with vertical surfaces due to how the pixels fall on the edge, which is part of what creates the "contour map". Adding an 8-degree draft provides a better transition for the edge and might provide a smoother finish.

[rscrawford]

Some tapered ballnose bits I've seen are pretty close to 8 degrees. Do a clean up pass with one of those (just do a full depth clean up cut so the whole taper is engaged at once).

[fixtureman]

Here is one you can probably find more

http://compare.ebay.com/like/1709561202 ... s&var=sbar

[Seppy]

I have a Customer who requires a 2 degree taper on all profile cuts, for the same reason, mold release. We are having a bit made for us to do exactly as the above post suggests so i think that is probably the easiest way. Save yourself a lot of time and instead of running a finishing path along those edges at all, simply run your taper bit with a profile path. You may have to factor material height x degree of taper to ensure you dont cut into your project accidentally (correct z height/cut depth accordingly). But potentially could save you hours, and give you the smooth shaped edge your client needs.

If you can't find the tool length/taper you need for your particular circumstance you can probably have it made for you, like we did.

[ChrisBWW]

Thanks for all the help. I tried using draft and upping the resolution all the way which both seemed to improve my results but didn't totally solve the problem. The edge still has ridges on it. I have been in communication with a tool mfg. company who can make me any bit I want. The problem is that my client's shapes that he wants me to cut out are very organic with lots of tight curves in them. The largest radius that I can use is .25". With an 8 degree tapered ball-nose cutter the most cutting surface I can get is around .5" and then they need to have about .5" cutting surface at 90 degree's above the 8 degree taper. The material that I am cutting for the project is 1.75" thick (foam) so I can't do a profile in one pass. When I simulate on Aspire doing just the profile cut with the bit that I was considering having made, it leaves a cut that is 90 degree's on top with a 8 degree taper on the bottom.
The test shape that I am using on Aspire is a simple circle with a bite taken out of it. The actual project pieces are quite complex. As it is I can't make the simple test shape with an acceptable edge. I appreciate any more suggestions of what I might try.