Ans.
About vibration at the bottom while cutting long keyway (210mm) , our reply as below:
In the beginning we would like to inform you that 210mm long keyway is belong to a difficult slotting job , So you need to
try the best cutting conditions
- Please understand that long keyway slotting , You need to have super rigidity slotting bar , Usually the slotting bar diameter L/D <= 3 -5 , Use good material slotting bar material , the L/D can be 4 , So your case which L (Slotting bar out length 210+40=250mm) , The Diameter of slotting bar should be 60-65mm
- Each cut (cutter width) as possible as small to let the cutting smoothly , You can test , 8mm, 10mm , 12mm .
- Each slotting feed rate test from 0.03mm , If 0.03mm OK. then test 0.04 , then test 0.05mm , Work-piece material hard and keyway long the feed should be smaller to let the cutting from top to bottom smoothly.
- The cutter (Insert) bottom rake angle suggest 5 – 8 degree and with a little arc to let cutting chip formed as roll type , Because long keyway cutting , You need thinking how to let the cutting from top to bottom always smoothly , You need let the cutting chip formed as rolled shape per 20mm then break then formed next rolled chip.(Cutting chip shape good , Slotting processing will be good)
- Let the slotting bar out bottom position more , Maybe let slotting bar out 25mm
- Try higher slotting speed with 0.03mm feed rate. (Slotting linear speed 15-20M/Min. , So you can try 31, 39, 44 SPM , Stroke length 250mm)
- Because long keyway slotting , The cutter will be hot while cutting to bottom position , So you need let the cutting oil feed to cutter during cutter at bottom position , Good cutting lubricating may be able to improve the slotting vibrating .
In our experience , normal length keyway (Less 150mm long keyway) , the Slotting process is easy , Over 150mm keyway , operator need to try slotting conditions , You can try to cutting 100mm keyway , If slotting is no problem , It mean machine is no problem , If you test 100mm long keyway, The CNC-350 can’t cut keyway well , It just mean machine have problem.
In our experience , the long length keyway cutting is always challenge for slotting processing , Operator need try and get the know how knowledge .
Solution:
- Improve Slotting bar rigidity (D>=60mm)
- Improve the cutting rake bottom angle to let the cutting chip shape as good rolled shape
- Add enough cutting oil during slotting at bottom
- Try faster slotting speed with 0.03mm feed rate
- Use smaller cutter (8mm or 10mm) several cuts