Need Help!- y axis datum/origin loss on bridgeport interact 1 mk2 cnc mill with a TNC 151 control

[leoncurt]

Hi, my name is Leon and i live and work in South Africa as a toolmaker, cnc programmer for a company manufacturing primarily builders hardware. I have been programming and operating the brideport interact 1 mk2 for more than 15 years with no major hassles but recently i noticed a very rough juddery sort of motion when jogging or winding the electronic hand wheel. Initially i thought it might be a lubrication issue since some of the feeder units have blocked up in the past and have been replaced. I had a technician check this and all the feeders are OK with the lead screws and recirculators getting adequate oil. After that i had an electronics specialist remove and test the y- axis motor and it clocked perfectly on the tachometer, it was re- installed and has worked OK for about 2 weeks until the juddery movement began again. This morning i started work and immediately aborted since i could see that the y-axis had positioned incorrectly, this meant that the y-axis origin was lost during power off. I would be most grateful for any advice or suggestions.

[gridley51]

Did the techs test rig test the motor on a drive or was it just connected to dc and spun up?
That problem is quite common on Interacts with Sem motors and Bosch drives and is usually the motor.If you`re sure the motor is 100% the next thing is the cables and then swap drives.
I had the same problem with an Interact last week that has been running a small part for several weeks.The X axis started juddering,in this case it was lack of lube as the table had not been moving far enough to carry the oil right along the slide.The right hand end of the table was bone dry.Cured by brushing some oil on and getting the operator to cycle the table full travel several times at start of the shift.
Mark.

[leoncurt]

Thanks for the response, the motor is a SEM unit but i'm not sure if it was tested connected to a drive board. I suspect it was merely run on a dc supply. I will contact him and check how it was done.

Regards Leon.

[gridley51]

Leon,
usually cleaning the tacho comm with a pencil eraser cures this.
Have you got an email address and I`ll send you out some info on these motors.
Mark.

[machintek]

I know when these motors have a dirty tach by putting it in a slow feedrate and place my hand on the table to feel how it is moving. Any shudder and I know the tach needs cleaning.
Also be advised that Bridgeport recommended a overhaul of these motors every 4000 hours of operation. That is 2 years at 40 hours per week. This is not practical and expensive. I have seen these motors last 7 years with no problems. Some of the interacts at the beginning had Y axis issues with oil and coolant getting in. A cover to protect the motor helped quite a bit.
Note tach resistance is 70 ohms. More than 100 ohms requires attention.
See attachment.

George

[leoncurt]

Thanks for the feedback guys, i have spoken to the technician and he feels based on the symptoms described that the encoder is at fault or maybe even some of the balls in the recirculating assembly are damaged. At any rate dis-assembly and inspection will have to be done! I will keep you posted as to the outcome since it may be helpful to other interact users in the future.

Regards Leon.

[gridley51]

You would get an error message on the screen if the encoder was at fault.