Feed Rates and cutters for wood panels

[Shinobiwan]

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.

[jimbo_cnc]

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.

[gavztheouch]

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?

[jimbo_cnc]

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

[Shinobiwan]

Compression cutters have both up cut and down cut flute patterns.

[jimbo_cnc]

Ah right. I see a lot of them have mostly down flute and a small up flute, that explains how I got confused because people were talking about them pushing the work down.

I've cut a few small pieces of MFC on my little 6040 using my standard manual tools, 1/4" with 2 straight flutes. They haven't damaged the melamine edge.

I was hoping to use the same tool for cutting the 19mm edge and for grooves which are about 6mm deep. It looks like I might be lucky and that the melamine will still be on the down flute for grooving.

[JAZZCNC]

You can ask 1000 people and they will all tell you a differant feed n speed, WHY.? . . . Because every machine is differant.

No one tell you exact speed N feeds you'll get away with unless they have the exact same machine and even then material and tool grades play some part.
They can only guide you to small degree based on machine spec which is what I did on the phone, the fact you have removed the machine spec makes this harder for folks to help. (And giving attitude when spec is questioned isn't endering)

Now if it was the same you told me with single 32mm ballscrew using steppers then 3500mm/min will be close to rapid speeds which is differant to what you'll get cutting making things worse. Hence why I told you it would be too slow for cutting MFC or MDF and maintain any decent tool life. The spec you told me was IME mixed up and wrong for any decent machine for cutting wood.

By your own searching you can see that average feeds are much higher so what do you want to hear.? . . Best advise in the world isn't worth a cracker if it's ignored, like wise all the sweet words you'd like to hear don't mean a thing if there wrong. They won't make the machine any better suited.!!

[jimbo_cnc]

As I've said, I'm trying to get away with a slower machine than what is recommended for tool life and productivity. And I'm hoping I can because my requirements are very different to a cnc shop.

And I wanted this thread to be about minimal requirements for a machine, not about any particular machine I'm looking at.

I'd be happy to hear about what machine design WILL fit my needs though, if anyone wants to make suggestions.

I've got another thread about designing a machine, it's still at the stage of choosing steel frame or aluminium extrusion. I got a bit hung up with straightness of rails I think after reading all Sylvaskis epoxy endeavours. So it hasn't got on to drive system yet.

[gavztheouch]

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.