Strange drive problem on ’95 Partner 1.

[moldcore]

After machining a pocket that was supposed to be in the middle of a block, upon inspection I noticed it was off center by .004. I used an edge finder to center the block originally and check it again using an edge finder and the block was still on center, so I thought. I then checked using an Indicol and the block was indeed off by .004. My first thought was that the backlash was way out, so I check it and it wasn’t more than .0003, but adjusted it to less than .0001 anyway. I Started to set up another block only this time the drive would give me the 450 error when I used the hand wheel but seemed to worked OK when I used the jog mode. Anyone have a clue on what may be the cause? This is the first major problem I’ve had with this machine in over 12 years.

[moldcore]

No One?

The service tech from the dealer was here late yesterday and was baffled and will return this morning hopefully with some answers. The machine will error only when using the hand wheel and at the same position every time. I’m thinking the screw may be misaligned putting an extra load on the drive. But why all of a sudden? Nothing has changed in 12 years. And why the .004 error?

[moldcore]

Follow up:

It was decided that the ball screw was defective and will need to be replaced. There can be no other explanation for the .004 error, actually .008 over 20 inches. Not sure at this point if I should fix it or just replace the machine with a new one. It’s a shame, the machine has been excellent for over 12 years. Maybe Milltronics will have some IMTS show specials worth looking into.

[LYN BYRD]

YOU CAN HAVE THE BALLSCREW REGROUND TO BE LIKE NEW.

[moldcore]

I’ve thought of that but the machine is old school (slow) and needs a major upgrade and new spindle bearings as well. Not sure how long the screw has been bad, we only used it for blocking material the past few years and only recently used it to cut some cavity for a hot job when we found the problem.

How long does it take to regrind the screw and who can you recommend to do it?

Milltronics wants over $2000 for the screw and another $2000 for the spindle rebuild. It going to be hard to sell in its present condition so I’m not sure what to do. I have a need for a running, accurate machine now, and can’t wait the 8 weeks it will take to get a new one from Milltronics. Just may have to go with Haas, who can have a machine here next week.

[LYN BYRD]

I have purchased ballscrews from Rockford Ballscrew in the past. Don't know if they repair, but I would bet that they do.
Or just do a Google search on ballscrew repair.
Where are you located?

[moldcore]

I did a search and found a few ball screw places in California that would be the closest around. Called one and they said I would have to send them the screw for them to inspect and quote. Not sure if I have the time to disassemble the machine, ship, and wait for an answer. Could be weeks without a machine. I’m waiting for the dealer to give me a quote for the trade in value of this one towards the purchase of a new VM 20. If the trade-in value isn’t high enough I’ll keep the machine and rebuild it later. I could use an enclosed machine for making blocks for the molds we make. I couldn’t replace it for what they will give me for it I’m sure.

Milltronics has come back with a three week delivery now if I order before IMTS with some discounting on the option package. They also said that all their prices are going up 8% after IMTS. Not sure if I can believe that one with the economy the way it is.

[LYN BYRD]

You could buy new precision ballscrew stock (& nut) and hard turn the ends yourself to fit the Milltronics.

[bborb]

Has anyone pulled covers off and inspected ANYTHING? There's been no mention of what the ballscrew feels like when turned by hand, belt integrity, and many other mechanical checks.

[moldcore]

Of course, we’re not that stupid, just a little slow at times. The dealer’s service tech was pretty thorough, spent a few hours here. We haven’t had time to do anything with the machine since. We’re only going to use the machine for basic operations such as blocking material for now.

The Milltronics dealer never got back to us on the trade in value but the Hass dealer would give us $10k. However, the price of their machine is not favorable with the same options.