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

Ball bearings are classed as grade 1, 5 7 and 9. These grades refer to
Bearing tolerances with grade 9 having the most precise tolerances.
Therfore using grade 5 bearings means low tolerance bearings are being
used...an indication of a low quality machine.

Smoke

>Jon,
>
>For this mill as configured with the Fagor control it is slow. I
>don't know the price complete with Fagor, but if in 20 quantity less
>control etc it's $3750 ( I think that's what I read here) then it
>must be at least $12K complete in single quantity. For that price I
>would expect much better performance, wouldn't you?
>
>I thought this machine had grade 5 ball screws, whatever that means.
>So speed limitations of Acme screws are not an issue here. Also, I
>assume it has servos, I can't imagine any machines are still being
>built with factory made controls and running steppers.
>
>At any rate the specs have errors and are very incomplete which makes
>me wonder about the builder.
>
>thanks,
>
>Doug
>
>
>
>--- In CAD_CAM_EDM_DRO@y..., Jon Elson <jmelson@a...> wrote:
>> dougrasmussen@c... 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
>
>
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