Today’s Machining World Archives February 2008 Volume 04 Issue 02
Dear Shop Doc,
Dear Shop Doc. I’m milling a slot along the length of the part on .875 aluminum hex parts with a Mitsubishi M635 controlled Citizen-Cincom C32. In the process, my hex stock sometimes has a large twist in the bar, resulting in up to 8 degrees of rotational error from the hex fat to the milled slot. What can I do to get rid of this error?
Twist and Shout
All of the Mitsubishi M635/M700 con-trolled Citizen-Cincom machines come standard with a torque sensing feature “G160” that can be used for many interesting applications such as yours. We helped a customer a while back with the exact same problem as yours. The following is what we did.
To be quick and simple for the customer, we installed a .187 ball nose end mill in an unused live tooling station. We then programmed the tool as a probe and touched it to one side of the hex; recording the position it touched (Fig-1). We then touched the other side of the hex the same way (Fig-2). With two points known, we did a macro calculation to figure the amount of error (Fig-3), and then positioned the C axis to that value. This process only added about 3 seconds to the cycle time.
See the program example below…
M18C0 (C axis to zero)
Y.35(a Y position good for checking)
G160Q30.X.7F10.(check Y+ side When X axis reached 30% of load stop)
#100=#5041 (record the X value on the Y+ side)
#3000=1(—ERROR -CHECK PART ROTATION)
Y-.35(same as above but negative)
G160Q30.X.7F10.(check Y- side When X axis reached 30% of load stop)
#101=#5041 (record the X value on the Y- side)
#3000=1(—ERROR -CHECK PART ROTATION IS TOO BIG)
#103=ATAN[#102/.35](Find the rotation error)
G0H-#103 (re-position the C axis incrementally)
Here are a few other applications you can use the “G160” for:
- To check if a cross drill or face drill was broken.
- To find the location of special extruded stock with a special multi-shaped ID.
- Often it’s used to check the collet pressure on the main- or sub-spindle to confirm clamping pressure before heavy drilling/turning.
- You can even use it for in-process gauging to set and check offsets while running.
Good luck with your problem. If you can follow these instructions these twisting problems should get under control.
Marubeni Citizen-Cincom Inc.,
Cust. Support Group Manager www.marucit.com