Need Help!- Finishing Vertical Surfaces

[jt83byrne]

Hello, I have a Haas CNC. I am constantly milling deep pockets and the outside profile of tall cylinders in the 1-4" range. I have been using a .75"OD endmill with a 4" cutting length. However the surface finish on the side walls of the pockets and cylinders comes out terrible and the sound of the tool chattering drives me crazy. Is there a better tool for this job? I have been looking at facemill/profile cutters with 90 degree cutting faces but they all have very large diameters and can not fit into smaller pockets or do the outside profile depth I need.

[SRT Mike]

Originally Posted by jt83byrne Hello, I have a Haas CNC. I am constantly milling deep pockets and the outside profile of tall cylinders in the 1-4" range. I have been using a .75"OD endmill with a 4" cutting length. However the surface finish on the side walls of the pockets and cylinders comes out terrible and the sound of the tool chattering drives me crazy. Is there a better tool for this job? I have been looking at facemill/profile cutters with 90 degree cutting faces but they all have very large diameters and can not fit into smaller pockets or do the outside profile depth I need.

What are your cutting parameters (feed/speed), and what material are you cutting? What is the depth of cut?

The sound of tool chattering is flex... either in the fixture or in the tool. 4" is a pretty long tool, even for 3/4" diameter.

I had some pretty bad chatter using a 1/2" end mill that was 3" long... but I had to have that small a mill for the corners.

-Make sure your part is held securely
-Try carbide over HSS cutters, they have less flex
-Pick a mill designed for your material... variable helix, high helix, etc
-Take light cut (maybe .015") on the last pass
-Try taking your finish pass in depths... like maybe 1/2" deep per pass at 0.015" or something.

[Boots]

Tool Chatter can also be cause by too much contact by the tool. I would use a 2 flute carbide high helix to limit tool contact and slower than normal rpm.

[Delw]

Use an Aluminum cutting carbide endmill, it makes all the difference in the world. stand carbide endmills chatter in alum very easy.
also make sure you have support up where your cutting as well.

[BobWarfield]

I would think you are seeing some tool deflection unless you're really babying the cut. When you're 4" deep, how much width of cut are you taking?

FWIW, there is a tool rigidity calculator built into G-Wizard. Going to a 1.25" diameter tool will get you a setup that is nearly 8x more rigid, all other things being equal:



I allowed an extra 1/2" of stick out from the toolholder for clearance. The less you can get away with the better.

In a week or two I will also add tool deflection calculation. The experimental version of the tool deflector predicts the 3/4" tool would chatter and suggests the 1 1/4" should not take more than 20-30 thou width of cut or it will chatter too.

Cheers,

BW