Re: Hemisphere surface finish problem
Originally Posted by
MFchief
Hi All,
I'm hoping for some advice on getting a better finish on a part I'm working on. It's a 2.6" diameter hemispherical cavity in 6061 Al. As you can see from the photo the surface finish leaves something to be desired!
I used Meshcam to generate the code, the finish pass is with a 3/4" HHS ball endmill cutting waterline only, mostly 0.01 to 0.02 inches per pass. Meshcam uses "adaptive step down", depending on angle. The step over is 0.02". Spindle was at 5100 rpm, and feed was 15.00 ipm.
Am I completely off base here? Tooling or F & S or something else? I chose the largest ball mill I had for rigidity. By the way, I would trade complete accuracy of the hemisphere for a better surface.
I appreciate any inputs you might have.
Terry
How much are you leaving for your finish cut? Your ,020 step over for your finish cut is fine, but as Ray said, your spindle speed is WAY too fast.
Slow gour spindle down to 3,500 RPM and increase your feed to 30 IPM and you'll see a world of difference. And only leave .015 to .020 stock for your finish cut.
It's OK ro ruff machine your part at 5,000 RPM, but I would only tale about a ,1 step over and no more than .150 deep. Yeah, it;s going to take a long time but it's only one part and you'll like the results.
I NEVER use HSS end mills. I ALWAYS use carbide. I know, it's a lot more expensive, but it works SO much better.
You can buy GOOD PARTS or you can buy CHEAP PARTS, but you can't buy GOOD CHEAP PARTS.