Re: [CAD_CAM_EDM_DRO] Re: servo vs stepper

turbulatordude <davemucha@...> wrote:

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Keith Clark"
wrote:

> As many have read, I have been having a bad time making stepper
> motors work using Gecko drives.

I didn't read the whole thread as you were getting advice from all
quarters.

I did notice some odd things. NEMA42 motors ? Huge, and with high
power needed to overcome the holding torque.


Nema42 motors are standard for Bridgeport CNC's . I've never seen a NEMA34 motor on any commercially available control. Prototrak, Centroid, Fanuc, Anilam, Heidenhein etc. all use NEMA42's for Bridgeports


back-up power supply, I never got one to work as when I turned on the
transformer the BBU/PS when crazy.

I don't recall if you used the recomended non-regulated power supply
or if a regulated one was used. (If switching, did you add a
capacitor after it ?)

Software other than Turbo-CNC to test the machine.

Soooo many people have gotten their systems to work, it is odd that
you have had so many problems.

How well though? Simply getting the table to move can hardly be classified a success. Being marginal on power only invites problems like heating of components, lost steps, ruined parts and the lack of confidence in your mill. The steppers I had on my old Bandit system stalled at about 30 ipm invariably before and after the retrofit. I could never set my speed above that. And if the ways were dry they would stall at 20ipm. My servo system is 5hp at the screw with a 2.5:1 reduction. "Tight spots" and high feed rates are not an issue. At the time of my retrofit, I consulted these lists and nobody knew of a suitable driver for Nema42 steppers. . Some may recall it. Even the old Bandit went through Allen Bradley drivers like socks. Them things were always blowing.

But, if your power supply is not correct, servos will fail too.


If your machine is too tight or has high friction in places, the
overall system will have problems.

If your software is not outputting quality steps, then your motor
cannot work properly.

The reason I use T-CNC for set-up is that it is like a hammer. No
frills, just plain pulses in a DOS environment.

Run whatever you need to make parts, but set-up with the simplest
tools you can.

Switching to Servo's will either solve the problem, probably by
replacing something not matched to the system, or will reveal what
the real problem is like using an extention cord that is too long or
too small, or endswitches that are effecting the logic power by
grounding....

On the good side, if you do swap out, your parts will sell for top $$
on e-bay.

Dave




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