Hi all,
I know this has been discussed many times, and I have perused many related threads here and elsewhere, but my first attempt at cutting aluminium sheet on my OmioCNC X4-800L (800W spindle) failed miserably and snapped the cutter :tired: I would greatly appreciate a sanity check of my method before trying again as I have a very limited supply of aluminium, cutters and cash...
The intended result is a small panel, 235x110mm and 1.5mm thick, for mounting a row of eight rocker switches into, which I have modelled using FreeCAD:
Attachment 498326
The CNC operation consists of a single "profile" job, since I'm skipping machining the drilled holes for now. For my initial attempt I used a 2mm single flute cutter, 12000 rpm, 0.2mm DoC and 1500mm/min feed rate. Foolishly without lubrication. The aluminium sheet was held down on a piece of MDF only by means of edge clamps. And I failed to notice at the time but the path moved the bit CCW around the cut, which I'm pretty sure is the wrong way for a right-handed cutter. The bit snapped about half way through cutting the first switch hole, and the cut was very rough with lots of gummed up aluminium along the top edges. For my second attempt I intend to make the following changes:
- Make the paths go clockwise
- 4mm single flute carbide cutter
- 18000 rpm
- 0.5mm DoC
- 1200mm/min feed (300mm/min vertical)
- Lubricating with WD40 spray
- Removing chips with a brush
- Improve work holding somehow
I used this formula for calculating the feed rate:
Chip load x RPM x number of flutes = feed rate
0.08 x 18000 x 1 = 1440mm/min
The 0.08mm chip load I got from here. It's on the lower end of their estimate for a 4mm cutter.
I'm taking it back a notch to 1200mm/min. The aluminium stock I have is the cheap horrible stuff, which I realise may not be possible to mill cleanly, but I want to give it the best possible chance under the circumstances. I did notice increasing noise levels as I made the first attempt, and I suspect the work not being held firmly down may have contributed to the problems. Certainly neglecting to lubricate was a big mistake. I'm hoping that a higher spindle speed and deeper DoC will produce actual chips as opposed to the fine powder I got on my first attempt - though I freely confess that's purely based on numbers I've seen in some other posts and has no theoretical foundation whatsoever.
Will any of these changes improve my chance of success, or perhaps only make things worse?