Author Topic: Can someone explain the current draw of these stepper motors, please.  (Read 9363 times)

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Offline simpson36

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Re: Can someone explain the current draw of these stepper motors, please.
« Reply #10 on: November 14, 2008, 07:27:24 AM »
I read most of the stuff on the Gecko site. I am using 4 of the Gecko 203v drives.

Power is one consideration, certainly, but steppers cannot do tiny jogs accurately and I've been told on this forum that this is inherent in microstepping.

I have had problems with the steppers loosing steps. An interesting paradox of these el-cheapo asian machines (mine is the X2) is that the ways are so crappy and inaccurate that i find I have to run them fairly tight to have any chance of keeping some accuracy in the machine. Moving the tight tables, and especially the head, take more power than cutting the part.

The Y axis on this machine was a huge PIA to get working. If I set the gib for a nice sliding fit at one end of the travel, it would completely jam befor it could get toi the other end. If I set it for a sliding fit and the tight end, it would literally be clunking back and forth at the loose end.

I had a binding problem with the Y axis ball screw which turned out to also be caused by the bad machining on the X2.

You get what you pay for. I did not expect to get a fine accurate machine, and in manual use, it's actually an OK little brute. CNC really showcases the limitations though.


 

Offline HimyKabibble

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Re: Can someone explain the current draw of these stepper motors, please.
« Reply #11 on: November 14, 2008, 10:16:27 AM »
Servos will not magically turn a bad machine into a good machine.  You need to lap the ways, and probably make new gibs, and get it moving smoothly over the entire travel.  If you're losing steps, it's not a function of stepper vs servo, but rather that you're expecting more from the motors than they can deliver.  A servo, under the same conditions, will do the same thing.  Fix the machine, and the motors will be fine.

Regards,
RayL.
Regards,
Ray L.

Offline simpson36

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Re: Can someone explain the current draw of these stepper motors, please.
« Reply #12 on: November 15, 2008, 06:15:15 AM »
That's what I did, Ray.

The Y axis is working OK now, but I think I am going to put jack screws on the bearing block and do a fine adjustment without the table on the machine to get the ball screw lined up properly. The machining on the front of the base is not perpendicular to the ways, so the accuracy in the bearing block is defeated.

I had read a lot about binding ball screws in my intial homework before diving into the retrofit. I never read where anyone had solved the issue though. Now that I've been down that road, I know what causes the problem (in my case anyway) and I think I have a solution other than having the base remachined accurately.

There won't be any servos on this X2. For my purposes, it is not worth the time to get an X2 up to the level I want it, because even if I make it into a 'good machine" it is still going to be too small and not rigid enough for upcoming projects.  I'm hoping the X3 is better quality.

Offline RICH

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Re: Can someone explain the current draw of these stepper motors, please.
« Reply #13 on: November 15, 2008, 08:42:38 AM »
It takes time to get a good ball screw running just so such that there is no binding.
I had to play with my retrofited Atlas mill a far amount. Adjust gibs for best movement across complete
travel ( all things considered ) with the screw mounting not restricting it. Then adjust the ball screw such that there is no binding at table extremes. Just need to spend time to find the best comprimised position.
RICH
« Last Edit: November 15, 2008, 08:44:31 AM by RICH »

Offline HimyKabibble

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Re: Can someone explain the current draw of these stepper motors, please.
« Reply #14 on: November 15, 2008, 10:13:54 AM »
That's what I did, Ray.

The Y axis is working OK now, but I think I am going to put jack screws on the bearing block and do a fine adjustment without the table on the machine to get the ball screw lined up properly. The machining on the front of the base is not perpendicular to the ways, so the accuracy in the bearing block is defeated.

I had read a lot about binding ball screws in my intial homework before diving into the retrofit. I never read where anyone had solved the issue though. Now that I've been down that road, I know what causes the problem (in my case anyway) and I think I have a solution other than having the base remachined accurately.

There won't be any servos on this X2. For my purposes, it is not worth the time to get an X2 up to the level I want it, because even if I make it into a 'good machine" it is still going to be too small and not rigid enough for upcoming projects.  I'm hoping the X3 is better quality.

Rather than jackscrews, I'd suggest going to McMaster-Carr, and getting some shim stock, and shim the bearing cover.  Jackscrews will likely dig into the soft cast iron base, or the bearing support, and change adjustment over time.

I think you'll find the X3 is a FAR better machine in all respects.

Regards,
Ray L.
Regards,
Ray L.