Stepper motor help on a Bridgeport

[Under dog]

New to the forum, first post. been lurking and reading alot. Name is Bob from upstate NY. I run an internet based shop building and modifying/porting gasoline engines for the remote control hobby. I also produce a few parts for the cars.

What I just purchased was a J head varispeed Bridgeport CNC with an old bandit controler. I picked it up for a song and figured I couldn't loose. If the cnc took a trip south I could allways convert it back to a manual machine and replace my Wells Index vertical mill with this one. Well after a short time the cnc took a trip south.

Before I was even able to cut the first part on it the X axis stepper motor stopped working. At first no matter what direction you tried to jog the table in X the table would only go left. This only happened a few times in a row then it stopped working all together. The display reads as if it was moving but the table doesn't. I found a blown fuse on the controller board, replaced it to find it just pops again. I took the stepper motor apart and found nothing burnt or shorted. All windings meter the same with no shorts to the chassis. Looks good. As this is an older machine I removed the wiring in the liquidtight conduit to inspect and that is all good. There was one white wire hooked to the board that I would get an intermitten short to ground on after toggling the power. After checking the wiring and the stepper I figured it is a problem or normal in the board. With the stepper unhooked the board does not blow the fuse.

I caught an article about stepper motors being overworked and loosing thier magnatism. Wondering if this could be my problem. The x axis stepper turns alot more smooth then the the others.

On the fence about repairing the cnc portion of the machine and just converting it to a manual. I do have a couple projects I would like to do production on the cnc but without it I would have to farm them out.

Anyone with any experience or helpfull advise on how to repair this would be greatly appreciated. Opinions are appreciated also. Thanks for reading this short book and looking forward to any help.

Thanks
Bob

[machintek]

I am not familiar with the bandit control but the favorite thing the BOSS machines liked to do is short the output transistors. From experience I know that one should not exceed 64 VAC nor 8.2 amps going to one of the axis. Also never press Emergency stop while a axis is running. The spike will short a transistor. Start there. You may resurrect it.
Also as the motors get old and weak, I lower the rapid thus the accel rate and it buys you a few more years of running.

George

[Under dog]

Originally Posted by machintek I am not familiar with the bandit control but the favorite thing the BOSS machines liked to do is short the output transistors. From experience I know that one should not exceed 64 VAC nor 8.2 amps going to one of the axis. Also never press Emergency stop while a axis is running. The spike will short a transistor. Start there. You may resurrect it. Also as the motors get old and weak, I lower the rapid thus the accel rate and it buys you a few more years of running. George

I do have experience with board repair at component level. If I can trouble shoot it to the board I may be able to repair it. If there is an econimical solution out there to upgrade to a pc based controller I would much rather do that. Ebay seems to have alot of systems but there isn't alot of feedback on them.

[Under dog]

Well today I hooked the good stepper to the questionable board, the board is no longer questionable but broken. So at minimum I have a bad driver board and most likely a stepper to replace.

Has anyone had any luck running Mach3 with say a Nema 42 stepper kit from ebay? Any help is greatly appreciated. If all else fails she will become a very nice manual machine and the hunt for an affordable cnc will continue.

[nate]

I run nema 34 870 OzIn steppers (pacific scientific hybrids) Single stack with a 2.2:1 belt reduction and have 80IN/MIN rapids and very robust cutting power.

With a decent quality motor, decent power supply and drivers, Mach 3 as a control, I have a PC based CNC Bridgeport for about 3K including the machine and a ballscrew kit.

Worth every penny, easy to build, all parts replaceable, good performance...I will never even go back!

Here is a list of components I used-

Mach 3 running on a laptop. 159.00 for the software.
Smooth stepper USB controler board. 165.00
CNC4PC C11 Break out board. 100.00
Keiling 70VDC power supply 180.00
Gecko drives G203V stepper drivers 139.00 each x3= 417.00
Pacific Scientific nema 34 870 OzIn steppers 65.00 each on ebay (NOS)

So... for $1216.00 I got a good pc based control and motor setup. Great deal if you ask me.

[Under dog]

Thank you very much for the info. I would think running the belts off of the handle you can also use it as a manual machine?

Originally Posted by nate I run nema 34 870 OzIn steppers (pacific scientific hybrids) Single stack with a 2.2:1 belt reduction and have 80IN/MIN rapids and very robust cutting power. With a decent quality motor, decent power supply and drivers, Mach 3 as a control, I have a PC based CNC Bridgeport for about 3K including the machine and a ballscrew kit. Worth every penny, easy to build, all parts replaceable, good performance...I will never even go back! Here is a list of components I used- Mach 3 running on a laptop. 159.00 for the software. Smooth stepper USB controler board. 165.00 CNC4PC C11 Break out board. 100.00 Keiling 70VDC power supply 180.00 Gecko drives G203V stepper drivers 139.00 each x3= 417.00 Pacific Scientific nema 34 870 OzIn steppers 65.00 each on ebay (NOS) So... for $1216.00 I got a good pc based control and motor setup. Great deal if you ask me.

[HawkJET]

Originally Posted by Under dog I took the stepper motor apart and found nothing burnt or shorted.

If you removed the rotor from the motor, you will have demagnetized the rotor and the motor performance will be significantly degraded.

Originally Posted by Under dog On the fence about repairing the cnc portion of the machine and just converting it to a manual.

It is so simple to replace the control with a computer and Mach3, I don't see why you would need to make it a manual machine.

[nate]

"Thank you very much for the info. I would think running the belts off of the handle you can also use it as a manual machine?"

no problem!

Trust me. dont bother with trying to incorporate handles. you will find that the Mach3 interface allows you to easily push a button and move an axis left or right. you can also adjust the feedrate from virtually nothing to fast as hell with the click of a mouse. You wont want handles after a day or two of running the machine under mach 3 control.



Go Mach 3/steppers/Gecko203v's and you will never regret it!!!!!

[Under dog]

Originally Posted by nate "Thank you very much for the info. I would think running the belts off of the handle you can also use it as a manual machine?" no problem! Trust me. dont bother with trying to incorporate handles. you will find that the Mach3 interface allows you to easily push a button and move an axis left or right. you can also adjust the feedrate from virtually nothing to fast as hell with the click of a mouse. You wont want handles after a day or two of running the machine under mach 3 control. Go Mach 3/steppers/Gecko203v's and you will never regret it!!!!!

One of the possitive points to this machine is it allready has ball screws on all three axis. I started stripping the old Bandit system off for a refinish and a refresh. Basically the only info I think I am missing is a specific link to the steppers and matching controls I will need. Sure I can find Gecko 203v's but what stepper motors will work with them?