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  1. #1
    I was just about to hit the buy button on a 900x1800 machine when someone questioned the feedrate I should be using on 19mm melamine faced chipboard or melamine faced MDF. I'd mistakenly asked for 2000mm/min or more (based on production time).

    The machine is designed for about 3500mm/min. The suggestion was that I should be using 6000 to 10000mm/min.

    A quick search on this subject reveals plenty of woodworking forum posts, where whatever speed someone says, someone else always say you need to cut faster eg someone says 15000mm/min and tool lasts 40 sheets, someone else will say "too slow, use 22000mmm/min and tool will last 80sheets" !

    Now, I'm not going to be a jobbing shop. The machine will probably be cutting less than 1 hour a week (at 3000mm/min) to make 1 product. And the profit margin on the product would allow for a new 30 cutter every hour. That's being extreme, but I would prefer to spend and extra 10 per job on cutters than an extra say 2000 up front on the machine.

    That kind of answers the economics of cutting speed, so next is quality of cut.

    I've only manually routed the MFC panels to date, and I get a good enough result with that. The customer doesn't see any edge faces, so I've never though much about the quality of the edge, as long as the melamine doesn't chip I've been happy.

    I'm getting a vacumm bed if that's relevant.

    I will be cutting a few 6mm wide grooves, some 19mm wide grooves, and then cutting out the profile. So I was thinking to use a 6mm cutter for the lot.

    I realise there isn't a question there, just some kind of self justification for buying a machine that feeds at 3500mm/min. I guess I'm hoping someone will say they cut at that kind of speed. And tell me what cutters they use and how fast they wear out.

    thoughts?
    Last edited by jimbo_cnc; 04-03-2015 at 03:12 PM. Reason: removed machine specifics

  2. #2
    (which I think is a problem for a ballscrew machine if I want good precision too).
    Where did you get that information from.
    From what I have seen on their website is that they appear to use a lot of supported rails and only a 1.5Kw spindle. I think you need to do some proper research into feed and speeds before buying anything. Are you sure the their machines on designed to run at those speeds or are they just the rapid speeds .. Clive

  3. #3
    I just knew I shouldn't have mentioned the machine or ballscrew design. It's removed now.

    This thread is part of my research into feed rates.

    Everywhere I look I get a different answer, but most of them are 6000mm/min plus.

    I want to know if I can get away with 3500mm/min given the cutting does not need to be at the economic sweet spot for tool life or machine productivity.
    Last edited by jimbo_cnc; 04-03-2015 at 03:28 PM.

  4. #4
    6mm 2flute down spiral
    0.15mm chipload
    10k rpm
    = 3000mm/min

    That might work ?

  5. #5
    Hi jimbo,

    If 3500mm/min is the max rapids of the machine then I doubt you'll be cutting with any decent DOC at 3m/min. For me that's too close for comfort to the performance headroom. I might be wrong and they can run the machine at 5m/min or whatever and just choose 3.5m/min to be conservative.

    I can tell you cutting MDF slowly quickly dulls TCT bits and I wouldn't even bother with HSS as they'll last even less.

    I cut around 6-7m/min with 6-9mm DOC in MDF but really depends on your machine. Spindle speed and the number of flutes is important too. If your really going to cut at slow speeds then definitely stick to single flutes. Don't thrash the shit out the spindle either. MDF doesn't need 24k rpm and the slower you go the less rpm you'll ideally use. There's a point where you'll run out of torque on your spindle though so I've found 10-12k rpm is fine for the feeds I mentioned above.

    You can get away with cutting at slow speeds such as 2-3m/min but make sure your using the right cutter and keep you spindle speed as low as you can otherwise the cutter rubs rather than cuts and that leads to burning and short tool life.

    For wood people think speed is a luxury but having had a machine that cuts at similar rate to what your looking at and now one that cuts it how its supposed to I can tell you its world of difference.
    Last edited by Shinobiwan; 04-03-2015 at 07:28 PM.

  6. #6
    OK thanks.

    You are correct, I need single flute to get the chip load OK. They are a bit harder to find and more expensive than 2 flute it looks like.

    For 19mm MFC I think I need 22mm or 25mm cutting length? I have seen some 20mm length is that too short?



    6mm 1flute down spiral
    0.3mm chipload
    10k rpm
    = 3000mm/min feed
    = 3.1 m/s cutter speed

    Is that getting better. Now I've lost the cutter speed tables I saw earlier.
    Last edited by jimbo_cnc; 04-03-2015 at 06:30 PM.

  7. #7
    If you really are just cutting for an hour every week then the this machine should do you fine. The feedrates of 22m/min in 18mm birch you were quoting are for big industrial routers that have big spindles, servos, vacuum systems and possibly tooling ( You can only push a 6mm cutter so fast) Any small scale machine is not going to match that performance in terms of 1. cut quailty 2. Last any time before something breaks/shifts/loosens/bends.
    CNC routing and prototyping services www.cncscotland.co.uk

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  8. #8
    Quote Originally Posted by jimbo_cnc View Post
    OK thanks.

    You are correct, I need single flute to get the chip load OK. They are a bit harder to find and more expensive than 2 flute it looks like.

    For 19mm MFC I think I need 22mm or 25mm cutting length? I have seen some 20mm length is that too short?



    6mm 1flute down spiral
    0.3mm chipload
    10k rpm
    = 3000mm/min feed
    = 3.1 m/s cutter speed

    Is that getting better. Now I've lost the cutter speed tables I saw earlier.
    What about a compression cutter to prevent chipping that melamine facing?
    CNC routing and prototyping services www.cncscotland.co.uk

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  9. #9
    Isn't compression cutter just a different name for down spiral?

  10. #10
    Compression cutters have both up cut and down cut flute patterns.
    Last edited by Shinobiwan; 04-03-2015 at 07:31 PM.

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