Need advice

[zoltan]

Hi,

I am trying to cut some parts for my new machine with the old machine and got in trouble. First of all, I used 2 flute end mill 2 mm diameter, 40 mm long with 8 mm cutting length and I intended to profiling parts from polyamide with thickness of 15 mm. I used 100 mm/min, 20000 rpm at 2 mm depth pass. Total disaster. After the first pass, at the second one the material melted and at the third one it was not possible to cut as at the first pass level the material closed the path. I need advice, what I should do? Is the end mill not appropriate as the cutting length is only 8 mm and at third pass the path is closed and there are no cutting edges to reopen the path or I must change the parameters and the material will not melt and the path will keep open? What will be these parameters? Secondly, I intended to cut MDF with same parameters. It was OK, except the fact that MDF started burn and it was smoke all around. What parameters I must use? Please, advise. My intention is to cut also AL, and I think is better to ask now, before starting to cut, so, what parameters to use for AL, too?

Thank you.

Zoltan

[ViperTX]

Well for MDF using a HSS cutter...20000 RPM is much too high, go with 10,000 RPM...your feed rate may be a bit slow for MDF....experiment at the lower RPM...

[mxtras]

Sounds like you need to make room for chip extraction.

Not knowing the details - can you use a large diameter cutter with more cutting length? Or use a larger tool then come back with a smaller tool for the details? If not, use a directed stream of high volume air to make sure the cutter remains clear. You may also want to try to grind some free length but the rigidity of the cutter would be sacrificed.

Sounds like a larger diameter cutter with more flute length is the answer.

Scott

[zoltan]

Hi,

Thank you. Still, I am not clarified about the issue. I understand that my feed rate is too small for the rotation speed. I do not believe that I can increase the feed rate due to losing steps, so I must lower the rotation speed. Could someone give me as a guideline some sets of parameters - feed rate, rotation speed for MDF, Polyamide, and AL for bits of 2-3 mm?

Thank you.

Zoltan

[kong]

When using a 2mm cutter in aluminium, you need to take lighter cuts, perhaps 0.5mm deep. Use lots of coolant, if the aluminium chips weld to the cutter, it will break easily. Use around 10-15000 rpm for ali.

[zoltan]

Thank you.

I am extremly frustrated. The machine is working. I learned how to get the g-code from designed parts. I have cutted a lot of foam pieces as trials. Everything was above the expectations, but now, I am not able to cut MDF or polyamide. I did try wood or AL. The MDF is burned and the plastics is melting. I change the dremel rpm but then it is stopping and...I could not setup a higher speed of CNC due to the Kcam which is not finding a time constant higher of 500. Who can help with complete advices. How is cutting - speed, bit, etc...

Thank you.

Zoltan