Re: [CAD_CAM_EDM_DRO] Re: need a transformer

rebel307 wrote:

>Thanks to the 3 who replied.
> I am useing basically an isolation tranformer then I got a variac for the power supply. I have been told over and over to get rid of the variac and get a "real" transformer. Art of mach software told me that himself. Mariss of gecko told me that. They both also said to get a transformer that will output the current rated for all 3 steppers put togather and add a tad bit more for a 4th axis.
> I am useing 1200oz/in steppers for X&Y and one 1780oz/in for the Z. All of them came from homeshopcnc.com. the 1200s require 6amp, the 1780 requires 6.2amp. You are saying use less amps, I put smaller resistors on the gecko to see if it would work with less amps, made the problem worse. I took the resistors out, didnt help so I put the values in to give me the motors rated current. Cap in the power supply is a 80,000MFD the caps on the drives are 470uF as gecko said. I am not an electronics expert, dont claim to be but I know that my machine isnt working and nothing anybody has said as helped other then get a real transformer.
> The problem, the motors insted of moving when a program tells them to move lock up. Its actually ok while jogging around, throw a program in and all hell breaks loose, they stall constantly. Make a rapid feed more then 30IPM on X&Y and more then 10IPM on the Z and your asking for it. I am beginning to think I should sell off the control and just go back the reliable way,,, manual.
>
>

OK, this indicates either a problem with the "tuning" of the software,
especially acceleration
parameters, needs to be looked at, or, perhaps, a slower computer is
being used, and the
step pulse train is "ragged". When you jog at close to 30 IPM, do the
motors whine smoothly,
or do they growl, and does the growl get worse as the speed increases?
If so, then pulse
raggedness is highly suspect. Gecko 201 or 202 drives require 2000 step
pulses per rev.
Making the assumption you have 5 TPI screws and a 1:1 drive from the
motors to the
leadscrews, then you have 2000 * 5 step pulses/inch = 10,000. At 30
IPM, that is
300,000 steps/minute, or 5000 steps/second. These larger motors become
quite sensitive
to variations in step pulse timing. These are undoubtedly size 42
motors, there is a jumper
on the Gecko drives that needs to be changed for size 42 motors. You
have to take the case
off the drive (at least for the 201/210 versions) to get to the jumper.
Have you done this?
If not, then there is no surprise at all that you have performance problems.

You don't say what speed computer you are using. I kind of assume you
are using some version
of Mach from your mention of Art Fenerty. Getting good pulse train
stability up to 5000
pulses/second shouldn't be too hard with Mach, but it still requires a
fairly decent computer.
Art or other Mach experts should be able to better advise you on what
CPU speed is required.

In the long term, getting rid of the variac should be a good thing to
do, but I don't think it
is responsible for your problems here.

Jon