CNC Education with Heinz Putz

Here is a recent CNC training experience that might help shops looking at used equipment. Courtesy of Heinz at

A company in Las Vegas purchased a Sub spindle CNC lathe, with a 12″ Chuck as the primary chuck and a 6.5″ chuck as the secondary chuck.  My job was to teach Fanuc CNC lathe programming and also program, set up and produce welding samples made from 6″ heavy wall tubing.  The machine was built in 1993, it looked good and seemed to work fine.  The tubing was cut off by saw to be about 5″ long and are goal was to do the 1st.  side in the big chuck, have the machine move the sub chuck jaws into the part, clamp on the inside, release the main chuck jaws, move the part back in Z and finish the other side of the part in the sub chuck.For safety, I made both sides of the part in the big chuck first which turned out to be a good decision.  The small chuck had no feed per rev, which is usually programmed as G99, we had to use feed in inches per minute, G98.  It also had no programming in Constant Surface feet, G96, everything had to be done in RPM, G97.  It was like solving a puzzle as we went along, none of this was documented, the guy I was training must have gotten mighty confused.  Finally, after solving all the motions and codes, the chuck stalled at the smallest cut, I was down to a .05″ per side depth of cut in the G71 cycle and the chuck still stalled.Thank goodness we had our program ready to run by using the big chuck only.  A service call will fix the problem, but it points out not to get a machine with more complexity than absolutely needed, especially if you buy an older machine.  Las Vegas was great, it was over 70 degrees in early February, our hotel was of course also a casino with what seemed like 1000s of slot machines, it was very hard not to be tempted and try my luck…


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