It's a 1987 machine, in general good condition. I've had it about three years. Slowly but surely it has developed a condition where it struggles to make a good cut when moving on the x axis when doing contour work. The cutter starts to 'sing' (scream!!) when it moves from a y axis pass onto the x. Obviously this messes the finish of my job up, makes our ears hurt, blunts our cutters, and tries to vibrate the spindle to bits - not good. I've had a good service guy out to look at it. He confirms the bed is good, no problem with servos, no significant wear or play in the bed etc. We swapped the spindle with our other machine (same spec) just out of unterest and initally the problem was solved! Great joy as we re-discovered what feed rates and speeds we used to be able to achieve! But then it all went sh*t again just a couple of hours later :( . So I ordered new bearings & fitted them - it's improved but still not right! Now getting a bit fed up due to spending lots of money but not the result we want & need. The weird bit is it's only when making x axis cuts that it plays up..

Any thoughts most gratefully received

Al

There are a few variables.
What spindle drive. Contraves or KTK?
What control? Yes, I know it is a Heidenhain, but which model?
Is the "spider" coming up on the control during a cut? This means a hold condition. If the spindle speed drops 20%, the control stops the feed so the spindle speed can catch up.
That is why the cutter is sitting there, singing away.
It may be a problem with worn out Spindle brushes or tach.

George

was gonna say tach problems
dose the feed cursor flash?

Cheers for the thoughts so far.

Not sure which spindle drive - how do i find out?
Heidenhain 155 controller.
No 'spider' issues. No sitting spindle. Spindle tacho cleaned and given a thumbs up from the service guy.

The interesting thing is that it is only a problem when making an X axis cut. For instance, we setup an octaganol test piece which we profiled. The cutter was making the same cut along each face. (I can provide speeds and feeds if interested). It only 'sings' when passing along the back horizontal face. (i.e. when the bed is moving from right to left). The only way to stop it is to reduce the spindle speed RIGHT down slow. I know that sometimes this sort of action is necesarry - but in this instance I'm absolutely sure something is wrong with the machine..

Thanks everyone,
Al

Have you tried swapping the drive cards? Like the X and Y?
Then I would swap the motors. If the problem follows one of these swaps, you will have your answer. If not is it possible that reversing X direction, it will cut different?
Maybe the bearings or ball screw are bad. Do you have excessive backlash in the X axis?

george

I'm going to go and think about the suggestions so far - thanks guys. Will return when I've got something to add!

Al

have you checked the x axis drivetrain? one of mine had a similar problem a while back
the needle rollers on the spindle drive were shot it still traveled the distance
just took a while ,sounded like a missfire on the spindle drive yet ran okay(ish) in reverse.
Mike.