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Facing problems on the lathe.

No, using G97 the part we are facing is about 15" in OD and about a 12" ID but were using DSSV to change spindle speed while cutting to help in chip breaking.

We've been using the same program but all of a sudden our surface finish went from 0.4um to 1.2 um (RA) and changing inserts is not bringing it back in spec.
 
I have seen chatter in an insert/tool bit that is not sharp enough or has the wrong-rake attitude so needing to generate enough pressure to penetrate the material, and when that is made the insert springs forward, or up..
The same might come from not having enough clearance under the cutting edge, and the insert has to bend down to make it cut.
Another possibility is when the cutting forces are too far forward on the saddle and so the saddle tries to tip/roll forward.... and yet another is when the tool holder is too long sticking out and tends to tilt down and then spring up.

Yes, these are on manual lathes, not CNC , but the factors may be the same.
 
I have seen chatter in an insert/tool bit that is not sharp enough or has the wrong-rake attitude so needing to generate enough pressure to penetrate the material, and when that is made the insert springs forward, or up..
The same might come from not having enough clearance under the cutting edge, and the insert has to bend down to make it cut.
Another possibility is when the cutting forces are too far forward on the saddle and so the saddle tries to tip/roll forward.... and yet another is when the tool holder is too long sticking out and tends to tilt down and then spring up.

Yes, these are on manual lathes, not CNC , but the factors may be the same.
I don't think so because we were able to achieve a 0.2RA um surface finish with our current setup and then all of a sudden it just went out and won't come back into spec we've tried different packs of inserts and different holders and tooling blocks. All with no avail.
 
I have seen this before on a larger box way lathe. The X axis slide was not moving smoothly because of worn gibs and lube issues. The play/stick in the box ways allowed the vibration resulting in surface issues when facing in X axis. The machine also had trouble with very small X moves. When a small X move was programmed over a 20 inch Z move to correct some part taper the X would jump in .0004 or so increments leaving noticeable marks on the diameter every few inches.
 
Start at the spindle, its easy to check endplay, and its a likely cause. I know thats not what you want it to be, but reality vs what you want dont necessarily care to align.

Make sure when checking endplay the indicator base is on the spindle housing, not anywhere else, to eliminate all the other variables. Indicator on the face of the shaft, push and pull in the axial direction and look for movement. You can move the indicator to the od and check radial play while youre there, but typically where there is radial play you also would have axial play and the first test would have sealed the coffin already.
 
Hi All,
This is my first dig at the forum.
I have an issue all of a sudden with my lathe. Same program same setup we have been running for years. I am struggling to get a finish during facing operation. Tried different speeds, inserts, nose radius but in vain. Any help is much appreciated.
Machine in Question is Puma 400 lathe with a fanuc control.
I even got the bearings on the Z-axis ball screw replaced.


View attachment 341810

MATERIAL:1045
DIAMETER:130
Id be wondering about the chuck jaws and if the part is staying secure in the chuck, maybe being bellmouthed or one jaw not tightening it to the part?
 
Start at the spindle, its easy to check endplay, and its a likely cause. I know thats not what you want it to be, but reality vs what you want dont necessarily care to align.

Make sure when checking endplay the indicator base is on the spindle housing, not anywhere else, to eliminate all the other variables. Indicator on the face of the shaft, push and pull in the axial direction and look for movement. You can move the indicator to the od and check radial play while youre there, but typically where there is radial play you also would have axial play and the first test would have sealed the coffin already.
Brand new machine so had Ellison in under warranty. Checked the spindle and turret both. Turret was out .010” over a 4 inch span and spindle and chuck both checked out fine. Relevelled the machine and throughout all of this the surface finish issues still persist. Machine is literally brand new hasn’t ran more than 100 parts. Ran 30 parts with consistent finish after we proofed out a process and then poof the next day after doing some brushing trials at low rpm the surface finish goes out and stays out even with changed tool holding and inserts. Sometimes you can change an insert and it will come back for about 8-10 runs and then surface finish climb out and then you go to turn the insert and it will not effect finish. We’ve tried 2 tooling blocks, 3 tool holders, and about a dozen different inserts.
 
Brand new machine so had Ellison in under warranty. Checked the spindle and turret both. Turret was out .010” over a 4 inch span and spindle and chuck both checked out fine. Relevelled the machine and throughout all of this the surface finish issues still persist. Machine is literally brand new hasn’t ran more than 100 parts. Ran 30 parts with consistent finish after we proofed out a process and then poof the next day after doing some brushing trials at low rpm the surface finish goes out and stays out even with changed tool holding and inserts. Sometimes you can change an insert and it will come back for about 8-10 runs and then surface finish climb out and then you go to turn the insert and it will not effect finish. We’ve tried 2 tooling blocks, 3 tool holders, and about a dozen different inserts.
When I had this happen on a new machine the headstock bolts were literally not tight from the factory by the time we noticed what the actual issue was they could be turned by hand headstock was just heavy enough it sorta worked for a few weeks and slowly got worse and worse.

Machine was a Yama seiki with an 80” bed same design as puma 400l
 
When I had this happen on a new machine the headstock bolts were literally not tight from the factory by the time we noticed what the actual issue was they could be turned by hand headstock was just heavy enough it sorta worked for a few weeks and slowly got worse and worse.

Machine was a Yama seiki with an 80” bed same design as puma 400l
To clarify not sure if I gave full detail but the machine is a Puma V400
 
Brand new machine so had Ellison in under warranty. Checked the spindle and turret both. Turret was out .010” over a 4 inch span and spindle and chuck both checked out fine. Relevelled the machine and throughout all of this the surface finish issues still persist. Machine is literally brand new hasn’t ran more than 100 parts. Ran 30 parts with consistent finish after we proofed out a process and then poof the next day after doing some brushing trials at low rpm the surface finish goes out and stays out even with changed tool holding and inserts. Sometimes you can change an insert and it will come back for about 8-10 runs and then surface finish climb out and then you go to turn the insert and it will not effect finish. We’ve tried 2 tooling blocks, 3 tool holders, and about a dozen different inserts.

Wait, in the original post you said "same program, same setup we have been running for years"

Now you are saying its a new machine...

So, its a program and setup that is tried and true on a different machine? Or am I missing something here?

Either way there is looseness somewhere, or a frequency that is inducing movement between the tool and part.

Have you manipulated the speed to see if it improves going faster or slower?
 
Wait, in the original post you said "same program, same setup we have been running for years"

Now you are saying its a new machine...

So, its a program and setup that is tried and true on a different machine? Or am I missing something here?

Either way there is looseness somewhere, or a frequency that is inducing movement between the tool and part.

Have you manipulated the speed to see if it improves going faster or slower?
No that was the op @Rich I just started having on this new part after running 30 Parts of good surface finish we suddenly lose finish and cannot get it back. I just revived this thread hoping that the OP would give the deets on what actually went wrong with his machine in hopes of fixing mine. But yes we have manipulated speed and feed as well as DSSV to try and correct it. We just proofed out the process so the manager of the division is not wanting to make program changes to mask the real issue.
 
No that was the op @Rich I just started having on this new part after running 30 Parts of good surface finish we suddenly lose finish and cannot get it back. I just revived this thread hoping that the OP would give the deets on what actually went wrong with his machine in hopes of fixing mine. But yes we have manipulated speed and feed as well as DSSV to try and correct it. We just proofed out the process so the manager of the division is not wanting to make program changes to mask the real issue.


Ahh, I was lost, typical.

Definitely understand not covering up the issue, just a short term test to get to the root cause it what I was pitching.
 








 
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