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Low gear turning

Hertz

Stainless
Joined
Apr 27, 2009
Location
Sudbury, Ontario, Canada
Good morning. Going someone might know something about this issue. I'm on a BV560 MG CNC lathe and I'm running a large diameter part. I had to put the machine in low gear to run it. This isn't a problem, there's a mechanical lever that switches the gears and then M41 is entered in the program to initiate low gear. The issue I'm facing, is that the RPMs are not matching that of my surface speed and diameter of part. I'm turning a 17.1" diameter piece with a 600 SFM. I expect the rpm to be at 134 rpm, but instead, it's at 37. If I switch to high gear, the rpm is correct at 134. Is there something I don't know about with low gear and why it would change the calculation? Control is Fanuc 21i-T
 
Is it possible that the low gear has a different amount of teeth than what it's supposed to have?
 
So I tried one last thing, and that was to restart the machine after switching gears, and this worked. I'm not sure why it would need a restart, but it must have something to do with the control as well.

All is well now. I'll leave the post here in case someone ever runs into a similar issue.
 
but it must have something to do with the control as well.
Hello Hertz,
Its as Kevin suggests, its all about the MTB and the poor job they did of designing the machine and implementing the control. Your control is a big advance on FS5T and FS6T controls and MTBs were able to build machines using these early control where you didn't have to stop and use a lever to change gear, but where the gear change would happen seamlessly in the program via "M" code.

The only machine I've owned where the Gear Change had to be made with a manual lever was a ancient Nakamura with a Meldas control and even that had a proximity switch to tell the control what gear it was in without also having to specify an "M" Code.

Regards,

Bill
 








 
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