## Five axis slow progress

Wednesday, June 18th, 2008 at 3:19 pm

Unless you can see what you are doing, it’s hard to program it. I’m trying to make some algorithms which work, before I have time to make them fast. As you can see, the model has very few triangles to make the holder collision calculations quick. But it is also an extremely hard case.

Current strategy involves creating a waterline pass for a sphere (a ball-nosed cutter without the shaft) and then find a smooth trajectory of holder orientations that do not collide with it.

Step one is to find any trajectory that works. Step two will be to make it go smoothly.

• 1. anders replies at 19th June 2008, 5:25 am :

Obviously having the tool holder collide with the stock is a bad thing, but for 5-axis machining, isn’t there another objective also: optimizing the cutting conditions? I imagine you could take the CC point and see where on the sphere it is and try to orient the tool so that the surface speed is just right.

I’m slowly working on my own 3-axis things, I’ll get back to you when something is working.

Anders

• 2. Julian replies at 19th June 2008, 9:43 am :

When we visited the five-axis expert in Copenhagen I held one of his ball-nosed lollipop cutters at various angles against the surface, and he was adamant that none of these directions made any difference to the result. Not even scraping along on the tip, which you’ve have thought was the worst case.

So I guess this part of our intuition as programmers may be incorrect. What they do worry about are large changes in direction of the axis because that can cause the machine to have to move itself from one side to the other of the entire (rotated) part.

• 3. NeelD replies at 20th June 2008, 10:54 am :

>>When we visited the five-axis expert in Copenhagen I >>held one of his ball-nosed lollipop cutters at >>various angles against the surface, and he was >>adamant that none of these directions made any >>difference to the result.

The various angles do make difference to the surface finish, because a ball nose end mill has a zero surface feet per minute (SFM) in the center of the end mill. Giving some tilt in cutting direction or normal to cutting direction gives better surface finish.

• 4. Julian replies at 20th June 2008, 3:01 pm :

Yes I know the argument, and that’s what I believe.

However, when someone I can see is doing lots of five-axis work in his shop and is known as the best guy in Denmark, then I’ll take his word. I know it’s taking a chance, but I’m willing to do it.

• 5. NeelD replies at 30th June 2008, 11:22 am :

Hi Julian,
Do you have a gif or avi file of the simulation. Do you tilt the tool perpendicular to cutting direction, what happens at the internal corners? Looking at the tool axis vectors in the picture it looks like the holder is colliding at the internal corner.

• 6. Denys Plakhotnik replies at 14th August 2008, 2:06 pm :

Could you give me a name of “five-axis expert in Copenhagen”, please? I read tons of articles about five-axis toolpath generation. I did top five-axis experts list. There is no any one from Denmark.