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I've just had a thought about thread cutting with a VSD and using a stop switch on the carriage. Has anyone tried setting their lath at say 400rpm and the VSD to 10Hz? Would that help it stop faster?(maybe this only allpies to my inverter that can only start dc braking at 10Hz).
Stuart
Hi Stuart,
I think it's a good idea and one that would work fine. What I've noticed with the lathe stop, is that you tend to get more consistent stopping accuracy at lower speeds, when I was doing the wooden threads, I was running 50 rpm on the gearbox and 15 hz on the vfd, so the spindle was a nice sedate 15 rpm. At that slow speed it stops right on the button every time.
Even if you do find it overruns a little, you can always move the stop to trip a fraction early, as long as the speed is constant the stops should be pretty consistent.
In any event, I don't like the idea of going from full bore to dead stop too quickly I think it risks the possibility of putting undue load on the gear train.
Much nicer to ramp gently to a stop.
Regards
Ray
Hi Ray
I didn't mean to try and stop it super fast, just that if it isn't going as fast so for the same braking settings and pretty much the same loads it would stop faster hopefully being more consistent. I guess I'll have to get a 3 phase motor up and running.
Stuart
Hi Stuart,
Just clarify a minor point, for your drive..
How does the dc braking function work?
Is it..
When you select a decelleration ramp, it ramps down until it gets to the set dc injection frequency and then starts injecting dc into the windings to perform the braking function?
That is with no stop input active, just run signals removed.
Or...
Does dc braking only apply when you activate the stop input and the frequency drops below 10hz ( or whatever Fn16 is set to) ?
I find the FM50 manual a bit unclear.
Regards
Ray
If you select controlled stop, you get ramp down then braking. No other input required.
Stuart