Aluminium...HELP PLEASE

Mostly Printed CNC - MPCNC Troubleshooting
#1

Hello Everyone,

I have been doing cuts in wood and acrylic, and wanted to try my luck with aluminium. I have 6082-T6 1.5mm (0.06") that I am trying to cut a rounded rectangle through. My first trial was using 1/8" single flute carbide bit, I was using a DOC of 0.3mm at most. Tried it with high and low RPM (I have a Makita Router 10000-30000rpm), high feed and low feed. I noticed the Z axis tilting so lifted the Z axis closer to the gantry with a free Z axis of 2" only.

Things definitely improved but I had a feeling the bit was no good and I was right the flute was chipped and ended up using my 6mm shank by 5mm tool diameter 2 flute bit. The video below is the cut using the 2 flute bit at 200mm/min feed rate and 120mm/min plunge rate with the router at 10000-12000 rpm:

It looked good until the bit broke through the aluminium (I have a plywood wasteboard underneath, i know its not the best), and somehow it started jittering and got stuck at the right side as you can see in the image below, luckily the bit didn’t break or chip.

The part was designed with holding taps that are only 2mm long but as you can see at the bottom the part is somehow failing to get the areas around the holding tabs cleared properly as if when it lifts it has a problem plunging fast enough to get through again. I suspect the aluminium is bent or not flat on the surface. But how can i ensure its 100% perpendicular to the rounder bit and what do I do about the wasteboard catching?

Any suggestions would be appreciated.

Cheers,
Bash

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#2

Raise the material up another 2". With aluminum rigidity is key.

To give you an idea, most other small mill only have a max travel of 3". Raising it up should help a lot. Every single mm counts, Get your bit as far into the collet as you can, raise the tool all the way until the bottom of the z tubes are abut to come out of the lower bearings, mount your spindle as high as posible, the raise your material all the way up.

As for the holding tabs, you could be cutting so shallow that the aluminum is actually bending under the bit. Raise everything up and try to get depth of cut a little deeper. Which would also help cooling, you need to get some chips out of there they carry all the heat with them.

#3

That was kind of a convoluted way to say, Minimize the distance from the tip of the bit to the bottom of the gantry, that is your z measurement. Looks like you are more like 4" or 5". Every time you half that distance you will be about twice as rigid.

#4

Thank a lot of the promot reply.
I will raise the z axis more. The bit is all the way in, lots of chips/dust was coming out it was flying away from the machine the entire time. It was going smoothly until it broke through. One thing i noticed the depth of cut doesnt seem to be constant across the entire rectangle which made me suspect the perpendicularity of the surface, given the cut started at the top so it shouldve broke through there. But how can i align the sheet against the z axis?

Thanks a lot!

#5

Is your machine planer to your work surface?

Check all 4 corners to make sure they are the same height, as close as you can get them, you can tell even .3mm will make a difference. The other way is to just cut further through the material, that is the more common way to compensate, because nothing is perfect. You can also mill your entire work surface flat but then when you raise your material up you can easily get it out of whack again so just cut further through your material.

#6

Well thats what i thought. So i milled it at 2mm when the material is 1.5mm but it got stuck in the wood not even the aluminium!

#7

I have just checked and the surface of the aluminium is just about 7cm from the bottom of the gantry. Is that too low?

#8

It will work, it will just work better if it is closer.

#9

I will do that. And i will give it a few more trials. Should i change the rpm, should i be increasing it or the feedrate?

#10

I am also playing with routing some aluminum. The picture attached is some that I have done successfully. These are my settings (sorry they are in imperial) Material Thickness: .063 inches; Depth of Cut: .010 inches; Feed: 13 inches/minute; Plunge: 8 inches/minute. I have recently cut my corner rails down to where there is only about .375 in. of space between the printed parts. I am using the Dewalt D660 router and I slow it down to about half. The RPM that is advertised for the router is 32,000 RPM. I am using a 1/8 inch diameter cutter with 4 flutes. This cutter was quite expensive $10 and it is also carbide. So far so good but I think I could raise the material a little bit higher and closer to the gantry and cut down on some of the little bit of chatter that i still have. One thing for sure is make sure your bit is able to plunge. Some bits are not made to plunge.
Let me know if I can offer any other advice.

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#11

Thanks for the response wichitpilot. Your settings and situation is quite similar to mine. Perhaps I could try and up the RPM and Feedrate to yours and see if it makes a difference. To improve plunging I changed the setting in Estlcam to plunge at an angle.
My only concern is why the problem happened after it went through the material, there were no issues for 4 passes and then once it managed to break through it got stuck in the wood!
I think trochoidal would probably make it a lot easier and smoother but I first need to understand why is it not happening as it is now.