Plunging and ramping speeds

[gavztheouch]

When cutting plywood I ramp the tool down into the wood rather than a straight plunge If I can.

Do you normally reduce the feedrates when entering the wood or is it better to use the same feedrate as your cutting feedrate?

Is there a way of calculating the best angle to ramp down with?

Gav

[Lee Roberts]

I would say ramp slower, as it can only but help in machining any material, typically ramping is used to for hard materials so as not to "ding" the cutter and things like that.

Find a happy medium for your machine, tooling and or application?

.Me

[Neale]

I thought that ramping was used because a typical cutter does not like cutting to its centre, or at least doesn't cut too well. I use it in ply and similar as it's trivial to do with vCarve, and I aim at maybe a couple of cutter diameters for ramp length with DOC about half cutter dia. Not very scientific but it works for me! Slightly lengthens cut time as vCarve ramps down, and then has to cut an extra ramp length on each pass to bring the whole cut to depth, but that's not really an issue in my non-production situation. I don't (not sure that I can) change any feedrates for ramping without editing gcode; you already have plunge rate which is probably limiting things, and during the cut you are removing less material than during the cut proper. Works for me, but I'm sure that there is a proper answer...

[Ger21]

With really small tools (<= 1/16"), ramping slower can actually cause them to break, as the cutting force goes from very light to very high as soon as the ramp ends, and the feedrate goes up. Ramping at full feedrate gives a gradual "ramp up" of cutting forces.

With larger tools, this isn't an issue, and ramping is mainly just to avoid plunging. If your ramp is very short, then you want to go a bit slower. The longer the ramp, the better, if you have the room, and it's not so long that your increasing cut times. With our Morbidelli, I keep AlphCAM set up to make the ramps 5x the tool diameter.