Jashley73
Titanium
- Joined
- Jan 24, 2013
- Location
- Louisville, KY
Ok guys, I have a problem that is driving me crazy. One of our machines is having trouble holding size on a part we run every day in production. This part runs on another machine without issues, so the problem is isolated to this one machine.
Part is a forging, gets two bearing diameters turned. One at 1.75", one at 2.625" +/- .0004" tolerance. Part is held between centers.
Here's the tricky part.
The 2.625" diameter (closer to the headstock) is no problem. +/- .0002" or less, ALL-DAY-LONG!
The 1.75" diameter (closer to the tailstock) is a wild card. Operators have been writing down sizes of every part, including any adjustments made, and results from re-running the parts... It will hold .0001-.0002" for 5-6 parts, and then suddenly drop -.0004". Occasionally it will go the other way, and jump oversize as well. Likewise, it will jump oversize on occasion.
But, ONLY on this ONE diameter...
It will also jump high/low, and be back at nominal on the next part.
The parts are measured with snap-gages with electronic indicators with 1-micron resolution. Everything indicates that the gaging is accurate, repeatable, and in good working order. (We use these everywhere, and are aware of common issues to look out for...)
Anyone have any ideas? I am grasping at straws trying to figure out why only ONE diameter would behave erratically like this. Maintenance just aligned the turret for center-height via Radial turret alignment. (Ex CNC field-service BTW - very sharp, capable & knowledgeable.) If you setup an indicator in the machine & test positioning & repeatability, it will repeat, DEAD-NUTS, every time!
I even went so far as to install a freshly-cut part, setup an indicator in an empty tool pocket & "scan" these diameters with my indicator, with code yanked right from the main program. Repeats with less than .0001" T.I.R. on a test indicator, on BOTH diameters...
Has anyone ever seen anything bizarre like this before?
Part is a forging, gets two bearing diameters turned. One at 1.75", one at 2.625" +/- .0004" tolerance. Part is held between centers.
Here's the tricky part.
The 2.625" diameter (closer to the headstock) is no problem. +/- .0002" or less, ALL-DAY-LONG!
The 1.75" diameter (closer to the tailstock) is a wild card. Operators have been writing down sizes of every part, including any adjustments made, and results from re-running the parts... It will hold .0001-.0002" for 5-6 parts, and then suddenly drop -.0004". Occasionally it will go the other way, and jump oversize as well. Likewise, it will jump oversize on occasion.
But, ONLY on this ONE diameter...
It will also jump high/low, and be back at nominal on the next part.
The parts are measured with snap-gages with electronic indicators with 1-micron resolution. Everything indicates that the gaging is accurate, repeatable, and in good working order. (We use these everywhere, and are aware of common issues to look out for...)
Anyone have any ideas? I am grasping at straws trying to figure out why only ONE diameter would behave erratically like this. Maintenance just aligned the turret for center-height via Radial turret alignment. (Ex CNC field-service BTW - very sharp, capable & knowledgeable.) If you setup an indicator in the machine & test positioning & repeatability, it will repeat, DEAD-NUTS, every time!
I even went so far as to install a freshly-cut part, setup an indicator in an empty tool pocket & "scan" these diameters with my indicator, with code yanked right from the main program. Repeats with less than .0001" T.I.R. on a test indicator, on BOTH diameters...
Has anyone ever seen anything bizarre like this before?