Cnc error

[wirralcnc]

I have a boxford 190 cnc mill. Running mach 3.
When I program and run part, it's fine. Then after about 40-60 minutes. I put fourth component in (same program ) it has an error on the axis and the datum has move 3-5mm making component scrap. The error seems to be on the x axis.
Any ideas???

 

[xpylonracer]

Are the 2nd and 3rd parts to spec ?

 

[wirralcnc]

Yes around 20 minute machine time each part. First 3 parts are fine then the 4th part goes out about 5mm. All parts are up to a stop. It roughed the 4th part ok then the finish cycle machined the lugs of the part.

 

[Cogsy]

Just a guess, but is something heating up, getting tight and causing a motor to lose steps maybe? What happens if you re-zero and put part number 5 straight in?

 

[wirralcnc]

I have taken the x axis apart. When I unscrewed the ball screw all the balls fell out the nut. The motor sounds a little rough as well. When ran on its own. Can someone tell me what the details are on the motor? Also if I replace ballscrew/ nut will I need same pitch or can I configure this with motor?

View attachment 1442084456358.jpg

 

[stevehuckss396]

You should be able to buy precision balls from VXB and reload the nut.

Stepper motors can make a wide range of noises. Its pretty normal for them to hiss and "play notes". As long as the noise isn't a grinding noise you should be fine.

Is it possible a chip got into something and bound up the axis?

 

[RonGinger]

I think its unlikely that a mechanical component has been overheated to cause this. I suspect that the driver board or power supply has overheated and becomes weaker. From the round body of the motor its clear these are very old steppers. Before I spent a lot of time or effort in finding the problem I wold just replace the motor and driver with a new hybrid style stepper. You will get significantly better and smoother performance.

Tough luck on dumping the ball screw. They can be reloaded if you can find all the balls, or buy some new ones- they are very cheap and can be had in a very wide range of size- measure a few of the ones that escaped and determine the best size. Loading a ball screw is tricky until you get it partly loaded. You will need some kind of spacer to hold the screw central in the body of the nut until you get enough balls in it to hold the alignment. I'm sure there must be a you tube video showing how to do this.

 

[wirralcnc]

Can anyone recommend stepper motors etc
Robbie

 

[kf2qd]

Ball screws are easy to reload. Need a little light grease to help keep then from wandering on their own. Like he said, getting the first half dozen in is the hard part.

Will still work if you are missing 1 or 2, but if you replace any, replace them all. if you get a slightly bigger ball, (talking tenths here) you can even eliminate some backlash, though it will run a bit stiffer.

 

[willburrrr2003]

Can anyone recommend stepper motors etc
Robbie

I purchased 305oz steppers from Dave at HobbyCNC, for about $75 each.

Regards,

Will