Re: [CAD_CAM_EDM_DRO] Re: GEM-500PCN bedmill - CNC ready

dougrasmussen@... wrote:

> Guys,
>
> I checked out the specs for the above mill. Errors in their
> specifications!!!! As I mentioned several weeks ago, this may be a
> clue as to the overall quality of a machine.
>
> They note the feedrate at 2000mm/rev for the CNC version. Do they
> mean 2000mm/min, which would translate to 79/min? 79 in/min is
> painfully slow, if that's the correct value, why can this machine
> only go that fast?

79 IPM is painfully slow? Talking with Sherline owners with Microkinetics
drivers, they were getting 14 IPM rapid feed rates, and at least some of
them thought that was OK. With my stepper rate generator board I got
25 - 30 IPM. On my servo-controlled Bridgeport mill I can go to 105 IPM,
but I rarely take it over 45 IPM because I have a tendency to cause
catastrophic crashes.

Now, for a real commercial shop, they want 400 IPM rapids, but most people
discussing this and similar machines are not doing commercial production.
Going much faster than this may cause real problems with Acme screws.
Anyway, with steppers, the power decreases very fast with increasing speed,
so that may be the cause of the speed limit.

Jon