1. #1
    I am VERY new to the CNC world, and wondered if anyone could offer any advice for the following. I am attempting to cut 1.15mm sheet aluminium which has a white polyester coating on one side, protected by a plastic film, which is used within the world of photography!

    To date, I am dry cutting the sheet with the coating face down and getting very mixed results. The biggest issues appear to be that chips are getting between the spoil board and the sheet, which in turn the tool is beginning to lift the sheet causing jagged edges. The edge cut quality is paramount and on part of the cuts it meets the grade, and other parts it doesn't. I have asked a few CNC users that have cut aluminium and of course each has a different answer for RPM/Feed rate etc, but currently I use a 6mm carbide tool @4000RPM with a feedrate of 0.5.

    Any advice would be gratefully received in terms of tools / rates / technique!

  2. #2
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,170. Received thanks 84 times, giving thanks to others 54 times.
    Quote Originally Posted by Drucook View Post
    I am VERY new to the CNC world, and wondered if anyone could offer any advice for the following. I am attempting to cut 1.15mm sheet aluminium which has a white polyester coating on one side, protected by a plastic film, which is used within the world of photography!

    To date, I am dry cutting the sheet with the coating face down and getting very mixed results. The biggest issues appear to be that chips are getting between the spoil board and the sheet, which in turn the tool is beginning to lift the sheet causing jagged edges. The edge cut quality is paramount and on part of the cuts it meets the grade, and other parts it doesn't. I have asked a few CNC users that have cut aluminium and of course each has a different answer for RPM/Feed rate etc, but currently I use a 6mm carbide tool @4000RPM with a feedrate of 0.5.

    Any advice would be gratefully received in terms of tools / rates / technique!
    For alu you need to clear the chips and lubricate. A drop of WD40 does wonders.

    Feedrate of 0.5 is in what unit of measure? Is that 500mm/min?

  3. #3
    Quote Originally Posted by Chaz View Post
    For alu you need to clear the chips and lubricate. A drop of WD40 does wonders.

    Feedrate of 0.5 is in what unit of measure? Is that 500mm/min?

  4. #4
    500mm per minute - correct - is it simply a case of spraying a bit of WD40 on the tool? I was planning to direct an air coolant spray at the tool/cutting surface to try to clear the chips....

  5. #5
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,170. Received thanks 84 times, giving thanks to others 54 times.
    Quote Originally Posted by Drucook View Post
    500mm per minute - correct - is it simply a case of spraying a bit of WD40 on the tool? I was planning to direct an air coolant spray at the tool/cutting surface to try to clear the chips....
    You need both ideally. Some cut fairly dry, just spraying air but WD40 helps lubricate. The issue with Aluminium is that it builds up on the edge of the endmill's cutting edge and then starts to gum up. If you dont have air, a few squirts of WD40 should help a lot.

  6. #6
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,170. Received thanks 84 times, giving thanks to others 54 times.
    In terms of Speeds / Feeds, there is variance depending on your machine.

    For Aluminium, 2 flute uncoated endmills are good. You did not mention depth or width of cut, or if you are slotting or not. You can try different methods, look up NYC CNC on Youtube, has many videos around Speeds and Feeds. Ideally you want to cut as deep as possible and take 10-15% of the Width as a cut. If you cant (because you are slotting), then Id probably go around at 1mm DOC at the speeds / feeds you mention. If you can vary your feeds during the cut, you will see and hear when the machine seems happiest.

    Just keep the chips clear and some lube on the cutter. No need to overkill it.

    You can see here, same size endmill, but loads more RPM and a sturdy machine = 4000 mm/min cutting, but lots (probably too much) lube.

    https://www.youtube.com/watch?v=QAv-q9P4FjA&t=67s

  7. #7
    How is your sheet held down apart from clamps at the edges?
    Are you using vacuum or tape to hold down areas away from the edges?

    Try a single flute cutter with air to remove chips and lube to reduce chip welding to the cutter, 4k rpm sounds a bit low for ally sheet, what speed/feed calculator are you using?
    You think that's too expensive? You're not a Model Engineer are you? :D

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