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Chattering Mark - CNC Turing centre

Rishi

Plastic
Joined
May 24, 2023
Hello Experts
We have a two axis (X,Z) CNC turning centre, with Siemens 802D & 611U Drives for turning a sheet metal box of approximately 1500 mm length between Chuck and tailstock. This machine machined approximately 100 components which were fine as per required dimensions. But one day operator did not clamp job properly in chuck and started cycle, turret came down in rapid and collided with component

We have tightened all mounting bolts of turret, checked alignment of tool wrt job centre found ok and then restarted, found turret is shaking during cutting and due to this, we find chattering marks on dia and face of component.

Spindle is fixed in high gear at 190 rpm so spindle rpm can not be altered

Pl refer to attached program. Tool T6 is for finish operation for turning diameter 208.5 then 152.310 (spec is 152.310 to 152.390 mm), chattering mark observed on dia 208.5 and also on 152.310 mm

Request to suggest on how to fix this issue, sometimes 2 to 3 components ok and then we have chattering mark

Regards
 

Attachments

  • Program.pdf
    50.3 KB · Views: 11
If you can see the turret vibrate, I'd say that where you trouble must be.
You could have lost some balls out of a lower truck, which the other 3 may hold it on location when relaxed, but when in use, it could chatter.

Try a pry bar and an indicator to see movement, then try to figger out where that comes from.


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Think Snow Eh!
Ox
 
Thank you so much for your swift response.
Shall check and revert
Do u also please suspect LM Blocks and bearings of axis/slide to have got effected due to sudden impact ?
 
Well, a bad crash could theoretically shear the bolts holding a truck on, but I would not blame a crash on missing balls.
I have had issues with loosing balls from aged trucks - where the plastic end caps get soft, and the action of greasing them may try to push them out.

You can loose quite a few balls w/o any adverse effects, and then one day the straw that broke the camel's back happens, and there is a gap in the string long enough to not have any balls engaged along the rail in that one spot anymore. Then they need replaced. I have one machine needing new trucks for the second time in it's life right now.

Now this may or may not be your problem. Again - I would recommend getting a prybar and an indicator out and go find where your looseness is coming from.


----------------

Think Snow Eh!
Ox
 
Well, a bad crash could theoretically shear the bolts holding a truck on, but I would not blame a crash on missing balls.
I have had issues with loosing balls from aged trucks - where the plastic end caps get soft, and the action of greasing them may try to push them out.

You can loose quite a few balls w/o any adverse effects, and then one day the straw that broke the camel's back happens, and there is a gap in the string long enough to not have any balls engaged along the rail in that one spot anymore. Then they need replaced. I have one machine needing new trucks for the second time in it's life right now.

Now this may or may not be your problem. Again - I would recommend getting a prybar and an indicator out and go find where your looseness is coming from.


----------------

Think Snow Eh!
Ox
Hello

Last saturday, we checked play in turret along both X and Z axes, found upto 70 microns

Sorry I did not get meaning of "trucks" - can you please explain
 
Hello

Last saturday, we checked play in turret along both X and Z axes, found upto 70 microns

Sorry I did not get meaning of "trucks" - can you please explain

I'm on my tablet and that doesn't cut and paste links well. But if you google "linear bearing trucks" you will see.


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Think Snow Eh!
Ox
 








 
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