Modern Machine Shop

FEB 2018

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CNC TECH TALK MMS FEBRUARY 2018 34 Processes and Programming Tracking Time with Custom Macro Custom Macro gives you the ability to monitor time from within a CNC program. System vari- ables provide access to two timers (milliseconds and hours), a calendar (year, month, day) and a clock (hours, minutes, seconds): • #3001 millisecond timer • #3002 hour timer • #3011 date (yyyymmdd) • #3012 time (hhmmss) The millisecond timer (#3001) will run for about 600 hours before it automatically resets. The hour timer (#3002) will run for about 9,500 hours before resetting. They are always running, but can be reset at any time. Consider these commands that use the milliseconds timer to cause a 10-second dwell: #3001 = 0 (Reset millisecond timer) N1 IF [#3001 GT 10000] GOTO 5 GOTO 1 N5 … The date and clock functions work differ- ently. If the present date and time is February 3, 2018, at 3:39:02 p.m., the current date and time system variable values will display as follows: #3011: 20180203 #3012: 153902 The clock uses a 24-hour format: 15:39 is, of course, 3:39 p.m. Since these system variables run in sync with the CNC's system clock, it is pos- sible to track events over longer periods of time. These time-related system variables also allow unique time-based applications. Think of situations in which events must be timed: • How long a cutting tool is machining (part of a tool-life monitoring system). • Preventive maintenance tasks, like filter changes. • Time-based sampling inspections. • Machine warm-up after a period of non-use. The following time-based spindle warm-up example was suggested by Ryan McKibbin of the Maryland Institute College of Art. A machine spindle's thermal expansion during warm-up may cause size deviations that make it impossible to run acceptable workpieces until it warms up. The warm-up routine must be run whenever the spindle cools, such as after off-shifts and when- ever the machine is idle for more than an hour. As Mr. McKibbin's program shows, tracking when the warm-up program is required can be programmed by including a few commands at the beginning and end of all programs: % O0001 IF [[[#509 + 010000] GT #3012] AND [#508 EQ #3011]] GOTO 5 #3006 = 1 (Cold spindle – press cycle start) M03 S12000 G04 P120000 M03 S18000 G04 P120000 M03 S23000 G04 P60000 M05 #3006 = 2 (Warm-up over – press cycle start) (Machining program begins here) N5 . . . (At the end of the program:) #508 = #3011 #509 = #3012 M30 % Permanent common variables #508 and #509 keep track of the last date and time when the machine finished running a program. The IF statement tests the last completion time plus MIKE LYNCH | COLUMNIST System variables allow for time-based applications like tool-life monitoring, preventive maintenance, sampling inspections and machine warm-up.

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