Gear selection...my rapids are too rapid!

[benjamint76]

I built my CNC Router about 2 to three years ago and I just keep upgrading...or trying. I have NEMA 34 motors moving my X and 2 moving the Y axis, driven by Gecko 203v and a PDMX breakout board. Power supply is unregulated 48v 12.5A. This is a rack and pinion system with dual-vee wheels.

I used to be happy with rapids of 350ipm and machining wood at around 250 ipm. I used to have planetary gears(5:1) on my Y axis, which really limited me to 350ipm. I just removed them last night and in order for the the gecko drives to get or give the motors "full power", I have to set my rapids at 2200ipm!!! While that would be awesome on a daily basis...not very practical.

Any suggestions?
I thinks a Gecko manual said to use a smaller power supply?
Use different ratio of planetary gear? (Expensive!)

Thanks
Ben

[ger21]

There's no rule that says you need to run your motors as fast as they can spin. You can just set your velocity in Motor tuning to whatever you want your rapids to be.
That's all you really need to do, if your happy with your resolution.

Are you running direct drive?

Do you have enough resolution? You could always fabricate a belt reduction, which is cheaper than gearboxes.

Reducing the power supply voltage will slow it down, and the motors will run cooler. But I don't really see the point in doing that. If it were me, I'd do a 2:1 or 3:1 belt reduction to increase resolution.

[benjamint76]

I am running direct drive(for the purpose of this thread, I just changed it last night). I was fairly happy with the setup(5:1 reduction), but my ego got to me. The big boy machines can really fly! I strive for my machine to be like theirs!

I think the best option is the gear reduction. I figure if I go to a 3:1 may rapid will be close to 600 ipm. 2:1 will put me closer to 850ipm. But these planetary gears are just over $300 each...and I need 2. Ouch!

I was hoping there was some magical answer for the setup of my electronics.

Something just dawned on me. Awhile ago, I changed my Y axis motors from serial to parallel and I did not change my resistors on the gecko drives until last night. Maybe I should put my 5:1 reductions back on with this addition of the proper resistors and see if my rapids can increase.
Thanks
Ben

[lukewarm]

Yeah I'm not sure I understand why you feel you need to regear. You can set your rapids lower in your motion control settings as long as your low speed resolution and torque is adaquate.