Avoiding machine crashes, part 2

Presented this month are more programming tips to help prevent machine tool crashes:

■ Reduce the “rapid” speed (G00) during setup and debugging by activating a lower rapid-speed percentage button. This is a precaution that gives you more time to hit the feed-hold button if something doesn’t look right. I often use these lower percentages during setup and debugging, especially when machining expensive parts.

A machinist should toggle between the cycle-start button and the feed-hold button as the cutter approaches the part. If there is a programming error, the machinist is in a good position to catch the error before any material is cut. All images courtesy J. Harvey.

■ For first runs and debugging, toggle between the cycle-start button and the feed-hold button on the controller as the cutter approaches the part. It is difficult to see where a cutter is in relation to a part when the spindle is at machine Z zero (retracted). The closer the cutter gets to the part, the easier it is to see the relationship between the part and cutter. Sometimes I toggle half a dozen times when a cutter is on its way down, especially when engraving expensive mold cavities.

■ Insert M1 optional-stop commands in the program before each tool change. For first runs and debugging, it is useful to have the optional stop activated so you can be at the machine when a new tool is actuated. Often, the first few moves a new tool makes will let you know if there is a problem. Once you determine all tools are running OK, you can deactivate the optional stop button and start running.

■ Clamp large remnants in place or remove them so they can’t fall behind the machine table. One time I screwed up one of the back-column sheet metal covers on a machine because I failed to remove a remnant that had fallen behind the machine table. When the table moved toward the column while a program was running, the remnant got jammed between the machine table and the cover, which destroyed the cover.