how fast do you plunge into aluminum?

[Mini Beast]

Sunday, I cut my first part out of aluminum. In the end, everything came out great. However, I e-stopped the program early on to edit the code and restart. The reason was that the first plunge at 2.5ipm with a 1/4" 2 flute endmill made the little guy shake violently. I think it was on 2600 rpm.

I changed the code to plunge at .3 ipm and it liked that better. I don't know if I need an endmill that can plunge better, or if I should just learn to program the machine to ramp its way into the material. My cuts were about .060 deep and I cut at 5ipm, with about a .125 stepover. That part seemed to work fine, I actually feel like I was a bit conservative there. Even at .3ipm the plunging seemed to put the most strain on the machine.

[Geof]

Even with a center cutting endmill plunging straight in can make a machine shake if it is not really rigid. Unlike a drill and endmill does not have a tapered point that tends to self center so the endmill tries to walk around the center web which does not cut efficiently. The best approach is to ramp in either with a circle or straight line; or drill a small hole and plunge down that.

[DareBee]

Simple.
I don't plunge (full dia anyway).
I always ramp or helix.

[Mini Beast]

Thanks for the replies. I will figure out how to do the ramping next time I cut a pocket.

Yeah, I decided that I'll probably build my enclosure with flood coolant a lot sooner than planned. I underestimated the mess it would make, and manually squirting the cutting fluid through an hour long program gets old REALLY fast. I don't plan on cutting a whole bunch more aluminum before I do this mod. Oh, and walking barefoot in the garage is a thing of the past now too.

[noisillator]

Originally Posted by Mini Beast Yeah, I decided that I'll probably build my enclosure with flood coolant a lot sooner than planned. I underestimated the mess it would make, and manually squirting the cutting fluid through an hour long program gets old REALLY fast. I don't plan on cutting a whole bunch more aluminum before I do this mod. Oh, and walking barefoot in the garage is a thing of the past now too.

You are exactly where I hope to be within the next two or three weeks. I've tested the controller and steppers, and now planning to order the Taig this week or next. Please try to shoot a few photos and post your work regarding the enclosure and cooling system. It will be very helpful to those of use who are also just getting started in this.

[Mini Beast]

Originally Posted by noisillator You are exactly where I hope to be within the next two or three weeks. I've tested the controller and steppers, and now planning to order the Taig this week or next. Please try to shoot a few photos and post your work regarding the enclosure and cooling system. It will be very helpful to those of use who are also just getting started in this.

Good to hear. Let us know how the new machine works out when you get it. This has been a lot of fun for me, and I'm happy with the purchase. I just wish I had more time with it. Unfortunately, working full time and going to school only leaves a couple hours a week to play with the Taig.

I'll post up with the enclosure project. I've been looking at other people's setups trying to get ideas. Fretman has a really nice looking one. I'll start another thread when I start planning more seriously.

Tuesday night I ran the same part again (I needed 2). My buddy at work gave me a 3 flute endmill that has kind of a void in the middle. There's probably a term for it, but I'm not familiar with it. It plunged into the aluminum like butter. The 2 flute left a better finish at the bottom of the pocket, but that particular 3 flute was able to plunge without chattering at all. I still plan on learning to write in a ramp function though as a normal practice as others have suggested.

[noisillator]

Which software are you using? Vectric Cut2D has an adjustable ramp plunge function built-in.

[Mini Beast]

This part was for work, so I programmed it there where I have access to Mastercam. I've been looking at some more affordable programs to use at home. I tried this part with the vectric demo, but it kept wanting to surface the top of the part instead of just going straight to the pocket. Maybe it was because I was using cut3D and not cut2D...

[noisillator]

Originally Posted by Mini Beast This part was for work, so I programmed it there where I have access to Mastercam. I've been looking at some more affordable programs to use at home. I tried this part with the vectric demo, but it kept wanting to surface the top of the part instead of just going straight to the pocket. Maybe it was because I was using cut3D and not cut2D...

I'm not familiar with Cut3D, but 2D lets you save G-code to cut just the vectors (pockets) you select at the time the code is generated. I've also simulated 3D pockets I built in AutoCAD 2000, then transferred to MeshCAM. The G-code generated by MeshCAM went straight to the pocket, and didn't cut anything else. there must be a switch or something in Cut3D that you haven't found yet. I'm sure it wouldn't force you to surface a workpiece before cutting holes. If you haven't found it by the time you read this, maybe a quick question on the Vectric forums is in order (either Yahoo or CNC Zone).

[MechanoMan]

0.3ipm is ludicrously low.

Higher RPMs may help.

Chatter can also be due to your mounting solution not being tight enough.
Lubricant is a good thing. Don't worry about the mess. In fact just spraying down a part with a water-based cutting lube in a sprayer beforehand is better than nothing.

See the problem is that if you gum up the cutting surfaces with aluminum, things get real bad real quick. The cutting power goes to zero and it just melts more on, as pressure increases as it tries to move into work it can't cut, you'll probably break the tool. Lube can prevent this. Also any methods that improve chip clearance- helixing in, using flood coolant, or compressed air- can improve it.