Velociraptor Project

[krfitz]

I did think of removing some material before the bit got to it, but I was very unsure of what would appear where, so I pretty much left stuff alone until about the last pass. I was smart enough to use the slowest router speed though.

I have a very thick spoil board, and the longest bit I can use for this project is 4" long. I even had to do some customizing of the Z-zero routine to get it to work, like changing the pullup to 1/16". I also used 1mm as the safe z to avoid losing z at the top.

When I rerun the right side, I am going to use a much faster feed speed, and I am going to keep a sharp, long-bladed knife handy for excess material removal. Must be very careful to keep the X-Y force on the foam very small while manually cutting so as not to move the material relative to the table. I like the idea of a hot knife...hmmmm...maybe use my paint stripping gun to heat the blade? That should work...

[Brady Watson]

Kevin,
Your machine may be different than mine as far as losing steps go. I had to adjust ramping on mine when rastering at a high rate of speed. I had one file that would lose steps in the same spot every time at 3IPS, in mahogany. I slowed the speed down to 2,1 and it was fine. I normally run foam at 2.5 to 3 IPS with no problems.

Just make sure the bit's flutes are long enough to get everything in one pass. If it isn't, it will gouge the foam at the top of the part because only the shank will be touching at that part.

I'm not sure if you do a roughing pass on it or not. That would help out to clear out the big chunks and reduce cutting force. THere is an option in MW to put a border around the file. If you use this, it will help clear out the high spots as well. Use the largest end mill you can for the rough pass. If you only have a ballnose, tell MW that it is an end mill. MW takes forever to rough out if you tell it is a ballnose.

-Brady

[krfitz]

OK, I found the border option in MW. Please explain to me exactly what this does? Another MW question: when you run a finishing pass, does it only cut the area of the model itself, or does it also "cut" those areas that have nothing there?

[Brady Watson]

Kevin,
In the MW Manual "The border added is set to the last value you used, or the radius of the largest tool you have specified, whichever is the larger of the two, to ensure that you can machine around the sides of your object. You are able to change this value to zero if you wish."

Unfortunately, you are going to have areas where it is just cutting the flat area using MW. I think that there are options to just mill the 3D part in other programs like VisualMill and ArtCam. What I do is set up multiple toolpaths on one sheet of foam and position them as close as I can to one another. I either overlap the dead flat areas in Rhino with my STL or 3DS files or just eyeball it when defining my 0,0 on the foam to save material.

-Brady