While most CNC Tech Talk columns are technical in nature, every once in a while I hope you'll indulge me as I talk about a topic that is very close to my heart. I'm hoping this issue is of interest to everyone in manufacturing.
One time-consuming task that often goes overlooked is tool maintenance. Tool maintenance is any task that involves upkeep on cutting tools used in the machining cycle.
Almost all current model CNCs allow you to specify an arc size in circular motions with a very convenient "R word. " Here is a tool path (based on cutter centerline motions) for Figure 1 using the R word as allowed by many machining center controls:
O0001 (Program number)N005 G54 G90 S500 M03 (Select coordinate system, abs mode, start spindle)N010 G00 X6.
Though machining center builders have come up with some pretty unique devices to automatically change tools, the programming words related to tool changing are relatively consistent from one machining center to the next.
The "T word" is commonly used to rotate the machine's magazine (or tool storage device) to bring a tool into the ready or waiting position.
Many turning centers, especially larger ones, have more than one spindle range. This allows power at low speeds for powerful machining operations and high speeds for finishing operations.
Spindle range changing on most machining centers is somewhat more transparent than it is on turning centers. With turning centers, the programmer must specify an M code to select the desired spindle range.
As you know, many CNC manufacturers design their controls to be used on a wide variety of machines. One machining center control model, for example, can be used by any number of machine tool builders for all machining centers in their product line.
Today's CNC machining centers and turning centers boast extremely fast rapid rates. It is not unusual to see current model smaller machines (especially those with linear guide ways) having rapid rates in excess of 1500 inches per minute.
Custom macro B (a popular version of parametric programming) gives you the ability to access tool offset values from within your program (with system variables in the #2000 series). It also gives you the ability to make tests (with the IF statement) as well as to generate alarms based upon finding problems.
Almost every offset entry requires some kind of calculation to be made before the offset value can be entered. Say, for example, the target diameter for a turning tool is 3.
While most companies take setup documentation quite seriously, many do little in the way of program running documentation. This is documentation aimed at CNC operators to ensure they understand just how a cycle is to be run.
All companies expect quite a bit from their CNC operators. Minimum responsibilities commonly include workpiece load/unload, cycle activation, offset adjustments to hold size, inspections on completed workpieces, and reporting inspection results to the statistical process control (SPC) system.