[benscale160]

I acquired a cnc masters cnc jr mill about 2 years ago. Aside from its short comings of being a round column machine and after a fair amount of tweaks, it has become a really decent machine. I threw away the cnc masters controller and am now using a cnc4pc gs11 board running Mach 3 with gecko motor drivers.

I am contemplating installing a 2:1 gear belt on the x and y axis for perhaps more resolution and motor flexing Currently the ratio is 1:1 with the motors rigidly affixed to the ball screws. Cnc masters soliton is to use rubber mounts on the motor mounting screws to allow for motor flex. Kinda a cheap soliton in my opionion. I am currently running the machine at 100 ipm rapid. With the 2:1 that would be 50 ipm rapid. With some tests, the steppers will run 250 ipm without any issue. So I will be able to maintain my current rapid of 100 with the reduction.

Any thoughts?

Thanks

Ben

[CitizenOfDreams]

Do you really need more resolution? If you do, can you achieve it with microstepping instead? Is there something wrong with the current motor/screw setup, besides being "a cheap solution"?

[CS900]

you loose a large amount of torque the more you microstep. If you need more resolution and you have the ability I'd absolutely gear it down.

Might be worth the quick read: https://www.micromo.com/technical-li...-and-realities

[Stigoe]

you loose a large amount of torque the more you microstep. If you need more resolution and you have the ability I'd absolutely gear it down.

Might be worth the quick read: https://www.micromo.com/technical-li...-and-realities

I believe that document has been debunked quite some time ago as misunderstanding the principles by Mariss from Geckodrive (I think it was).

[CS900]

I believe that document has been debunked quite some time ago as misunderstanding the principles by Mariss from Geckodrive (I think it was).

I don't believe that to be true. This has a better explanation as to why you loose torque when microstepping. Nothing's free in this world.... resolution included!

https://hackaday.com/2016/08/29/how-...epping-really/

[arizonavideo]

For a stepper you want micro steps at low RPM for smoothness and at low RPM you make full power even with micro steps. Power is a function of current in the winding and at low RPM below resonance you will always make full current. If the stepper happens to be stopped in a micro step location it will not have full holding power but it will if moved to a full count position by the load.

All Gecko drives will morph to a square wave and will deliver full non micro step power at higher RPM with any micro step selected. Almost 40% more than drivers that remain in a hi micro step mode at high RPM.

The power transfer function could be even better for some drives at high RPM if they compensate for inductive resonance but if they do there not talking.

For a 5 TPI screw and if you say micro stepping might give you a fairly good chance of stopping at half of a 200 point position then you would be at 400 count or about .0005"

I really doubt that the rest of the mill can hold .0005" or less precision.

You will only make the mill slower.

I would change out the rubber motor mounts with something stiffer and if you have any lash in the screws spend time getting that fixed.