Bridgeport interact4 x axis violent chatter

[ronmarkum]

I have an Bridgeport Series 2 Interact4 with a SEM MT30Z4-61 X axis motor. The machine runs but the X motor violently chatters and sounds like it is constantly drawing power (hums louder that the Y motor). With the belt cover off I can get the motor to momentarily stop the vibration by holding a block against the belt. I removed the brushes and they are about 3/8" long and seem in good shape. What things should I check next. I read in some posts that the Bosch drives may need to be tuned. How is this done? Any advice is appreciated.

Thanks
Ron

[gus]

I think it is more likely the tach is dirty or the tach brushes are worn.

There is a setting for display that sets it to 'lag' write a program that runs the x back and forth at rapid, turn the feedrate override to 0. the bosch drives[if they are the same as the S1 interact and r2c3] have a pot labeled 'tacho'

run the program and slowly turn the feedrate up till it will run and show you a lag error on the screen. it will vary at the ends of travel as it accels and decels. only watch the error at level feed rate[IE center of travel] Turn the pot in the direction that makes the number go down[duh] run faster and faster tweeking the pot until you get as small a number as you can, usually a few tenths.

It should not require a great deal of pot rotation, less than a turn say.

remember where you started so you get get back there.

If it does not work there is something else going on

[ronmarkum]

Thank you very much. I'll give this a try tonight. Ron

[machintek]

Attached are some service bulletins and notes relevant to BOSCH drive tuning and SEM motor brush life etc.

George

[ronmarkum]

Thanks for the service bulletins and the advice. Went through the tuning proceedure and found that the lag was about .016 instead of a few tenths. After adjustment the behaviour was better but still chattered though not as bad. Next went through the tach-brush cleaning described in the service bulletin. I measured the tach resistance at the terminal strip on the SEM and got 687 ohms. Disassembled as much of the SEM as I could and gave it a good cleaning. Boy, was it dirty. Reassembled, the resistance measured 433 ohms. Retuned the drives and it purrs like a kitten.

Thanks Gus amd Machintek for your help!!!

PS. Is there web site where all of the Bridgeport manuals and service bulletins are available?

[gus]

glad it worked out. appreciate the response; so many times you never hear the 'end of the story'

[machintek]

Private stash. I started working for Bridgeport in 1982 for the Bristol, PA sales service center. My service manager was Norb Lion Jr. Probably one of the smartest people BPT ever had. I learned from him to ask for any and all documentation and "squirrel" it away. Still don't have it all but enough to fix most Bridgeports. I have a span of about 3 years where I have a gap. Don't know much about the Bridgeport/Southbend Hydraulic positioning lathes, and never had a chance to work on the Alan Bradley controlled VMCs and the old BTC2s. Also back then, I asked that a BBS be set up for service techs to help each other and to have bulletins such as those you have seen to be posted. It was shot down because they were afraid that the competition would use that against them. The competition did not need it as it turns out. I still do not know how legit it is to distribute this material but people need it and Hardinge cannot supply it.

George

[aanvat]

It could be that you have a motor / commutation problem rather than a drive problem.
Have you checked the brushes and comm on the motor?

Clvie lunn

[ronmarkum]

Yes, that could have been all or part of the problem. I completely cleaned the motor and tach. After reassembly everything was greatly improved.