CAM Pocketing/Contouring Methods

[Cory]

Originally Posted by btslaser

Perfect. Do you spiral through the material? If so, what ramp angle do you use?

I try to drill plunge points with a larger tool. That can be a pain on a machine without a tool changer.

If the pocket is big enough I will use the helical entry option, with the default parameters. If not I'll just plunge slowly (10 IPM or so, with full flood coolant).

You can get a recommended ramp angle from your end mill manufacturer.

[FenixPheonix]

In my experience, helixing in at a 4 degree angle is quite decent (that's on high-end VMC's with aluminum optimized tooling, though. Your mileage may vary.) One good way to tell is how the chips accumulate. If they're birdnesting around the top of your tool, ramp in slower, and get better coolant. Flood, if possible (although you don't have an enclosure. Mist coolant and air jet, probably.) Ramp along pass isn't quite as good, if you've got that option, but it can do a better job sometimes of keeping the entry contained within the machined area.

Cory's suggestion of drilling the entry points is a good one, if possible. End mills hate, hate, hate, cutting down. Even ramping isn't very good. Your mill has the option of having a toolchanger, it says (CAT40? Seems overkill for 5HP...) For cutting the outside, your tool shouldn't have to plunge through the part, just profile from the outside in. Internal pockets, use whatever stepdown your cutter can take (may or may not require multiple passes.) If you leave maybe 2-3% of your cutter diameter for a finish pass, you can take all of that in one pass for finish and accuracy. Same rule for finishing outer walls.

Last note: I don't know whether HSMExpress has any constant-engagement toolpaths (trochoidal?) If so, use them. They'll limit the engagement in corners (where engagement angle normally spikes. For example, 50% cutter engagement turns into 75% when you hit an internal 90 degree corner), allowing you to turn the whole cut up, and keeping your tool safe.

EDIT: Sorry, that 50% cutter engagement spikes to 100%. My bad, long day.

[Mr. Mike]

Originally Posted by FenixPheonix

Last note: I don't know whether HSMExpress has any constant-engagement toolpaths (trochoidal?) If so, use them. They'll limit the engagement in corners (where engagement angle normally spikes. For example, 50% cutter engagement turns into 75% when you hit an internal 90 degree corner), allowing you to turn the whole cut up, and keeping your tool safe.

A cutter programmed for a 40% step over will see nearly 100% engagement when it hits inside corners of the same radius size. An inside corner radius that is 3 times the cutter radius will see the engagement of 52%.