[Danny]

Hi folks,

I'm working on a '86 Daewoo Puma 10 turning center, the only CNC in our shop. I'm the only person that runs it. We bought it used about 4 years ago. Up 'till now it's been doing well for us. We machine smallish parts mainly from DOM tubing up to 2-3/8 OD with some basic operations. We also machine parts from 4140 HR 2" shaft. We only do about 20 different parts over and over and are fairly low volume (averaging maybe 50 or so parts of each variety every 2 months if you need an idea), and they aren't any more than 6" long that we put through this machine (part stick-out from the chuck), and never had to use the tail stock before.

It has started to develop some diametral inconsistancies and now some severe chatter , without changing the programs, offsets, RPM, or feed. From the inconsistancies to the now severe chatter, the time span has been rapid, about 15 hours in working time. By "severe", I mean it doesn't produce a good part, the chatter won't go away by decreasing the RPM, or by either reducing or increasing the feed rate.

I've made sure all the tools in the turret are still tight, new inserts, greased the chuck again, and made sure the chucking pressure didn't change. I'm out of ideas.

I fear that either the main spindle bearings or the ways are wearing on the axes.

Does anybody have any ideas? Are there any adjusments on tightening the main spindle bearings? How do I adjust the tapered gibs in the ways?

The parts book and manual don't explain this very well, and doesn't mention at all adjustment of the spindle bearings.

Thanks in advance,
Dan

[underthetire]

No adjustment on spindle bearings, without complete evaluation. My guess is your turret is not clamping. I had to repair a 87 machine with the same problems. Orings get hard not allowing the turret to clamp all the way, and chips get stuck in the coupling from the front seal. When you index the turret, does it look like it kinda falls when you unclamp it ?

[Danny]

No adjustment on spindle bearings, without complete evaluation. My guess is your turret is not clamping. I had to repair a 87 machine with the same problems. Orings get hard not allowing the turret to clamp all the way, and chips get stuck in the coupling from the front seal. When you index the turret, does it look like it kinda falls when you unclamp it ?

I'll have to look for that turret "falling" as you describe. Is that a tell-tell sign of a turret clamping issue? What else could I look for?

Thanks,
Dan

[underthetire]

I'll have to look for that turret "falling" as you describe. Is that a tell-tell sign of a turret clamping issue? What else could I look for?

Thanks,
Dan

Set up a repeatability test. Zero an indicator on the slide somewhere, and move away, index the turret, come back to your zero point. Thats usually a give away. You can also just put a indicator on the turret, bolt a bar in one of the turning tool spots, and see if you can man handle the turret around.

[Danny]

Set up a repeatability test. Zero an indicator on the slide somewhere, and move away, index the turret, come back to your zero point. Thats usually a give away. You can also just put a indicator on the turret, bolt a bar in one of the turning tool spots, and see if you can man handle the turret around.

Yeah, that sounds like a good idea. I'm gonna work on that later tonight.

Anyother ideas at all?

Thanks again,
Dan

[MysticMonkey]

Hi, Sorry to hear your problems.

I would try a few geometrical/accuracy tests first.

1. Put a clock in/on the spindle and run it round one of the boring bar holders
if it is out in imaginary Y-Axis your going to get a lot of chatter.

2 Test the turret squareness run a clock along the face of the turret

3. Put the clock on the X-Axis ballscrew and put pressure in the X-Axis direction if you see any movement there is most likely a problem with the X-Axis bearings. If it doesn' put a clock on the turret and test again if there is movement then probably a fault with the ballscrew nut/bearings

4. Do the same for the Z-Axis.

5. Change the tip on your cutter


Is the spindle actually noisy? If so I would remove the chucking cylinder and test the spindle then.