Robin Hewitt
14-05-2010, 01:22 AM
Milling a round pocket with no islands in it. I think it's a special case, on account of it being a common requirement and easy to spot and cater for. Need to choose a method.
There's the centre, plunge, expand, centre, plunge, expand, over and over again method.
Not bad, but there is also the spiral straight down to the bottom method which gives a deliciously constant cut, and, often as not can work with a non-centre cutting end mill.
Plunging without zero backlash is not friendly, the faintest slop on the table can make for ghastly vibration as it tries to cut a slighthly out of round geometry. Plus the cutting force gives a powerful downward component on the screw least well positioned to take it.
Tempting to slow the feed rate near the bottom, but then I run the risk of getting in to cut/no cut territory, a rub/snatch cycle due to flex in the system.
Is a roughing out plunge with a horizontal component a bad idea? I've never tried it.
Anyone seen a super smooth round pocket cutting algorythm in action that I can stea... er, 'borrow' from?
Robin
There's the centre, plunge, expand, centre, plunge, expand, over and over again method.
Not bad, but there is also the spiral straight down to the bottom method which gives a deliciously constant cut, and, often as not can work with a non-centre cutting end mill.
Plunging without zero backlash is not friendly, the faintest slop on the table can make for ghastly vibration as it tries to cut a slighthly out of round geometry. Plus the cutting force gives a powerful downward component on the screw least well positioned to take it.
Tempting to slow the feed rate near the bottom, but then I run the risk of getting in to cut/no cut territory, a rub/snatch cycle due to flex in the system.
Is a roughing out plunge with a horizontal component a bad idea? I've never tried it.
Anyone seen a super smooth round pocket cutting algorythm in action that I can stea... er, 'borrow' from?
Robin