Copyright Goodheart-Willcox Co., Inc. Chapter 9 CNC Mill Programming 203 necessary tools and holders. When building tools, make sure they extend far enough to reach all of the programmed depths. All required tools will be placed in the tool changer according to their programmed tool number. For example, when a program defines tool #1 as a 1/2″ end mill, place that tool in the designated tool #1 position. 9.9.1 Length Offsets Now it is time to tell the controller the distance from the bottom of the tool at the machine home position to the programmed part Z0. The con- troller does not know how long the tool extends from the holder without the programmer defining this dimension. This is accomplished using G43, which establishes tool length compensation for each tool. Within the program, tool #1 will normally be designated as G43 H1, or Height 1. Although not required, it makes sense to match the height offset number to the tool number in this manner. Occasionally you might assign different height offsets to the same tool so that they can be offset independently. Next, you will need to determine the tool height for your G43 code. If programming from the top of the part, this is the distance shown in Figure 9-21. To measure this distance, move the tool down to touch the part Z0 position. While the tool is at this position, push the Tool Offset Measure button on the control panel, Figure 9-22. This will record the Machine home Distance is tool height Part Z Goodheart-Willcox Publisher Figure 9-21. The distance from tool end to programmed Z0. is the tool height offset value. POWER UP RESTART TOOL OFSET MESUR CHIP STOP JOG LOCK CHIP REV –10 FEED RATE +10 FEED RATE 5% RAPID 25% RAPID 50% RAPID 100% RAPID STOP 100% SPINDE 100% FEED RATE –10 SPINDLE +10 SPINDLE HAND CNTRL SPIN HAND CNTRL FEED SELECT PROG SEND RS232 RECV RS232 ERASE PROG ALL AXES ORIGIN SINGL AXIS HOME G28 .0001 .1 .001 1. .01 10. .1 100. COOLNT ORIENT SPINDLE ATC FWD ATC REV SINGLE BLOCK DISPLAY PRGRM CONVRS POSIT OFFSET CURNT COMDS ALARM MESGS HOME PAGE UP PAGE DOWN END PARAM DGNOS SETNG GRAPH HELP CALC DRY RUN OPTION STOP BLOCK DELETE INSERT LIST PROG ZERO RET HAND JOG MDI DNC MEM EDIT ALTER DELETE UNDO CW CCW SPINDLE SHIFT F L R X A G M S Y B H N T Z C D J P V ( E 7 & % * + @ $ , = : ! ? # 8 9 4 5 6 1 2 3 – 0 . CANCEL SPACE WRITE ENTER K Q W ) ] [ / I O U EOB NEXT TOOL TOOL RELEASE PART ZERO SET TOOL CHANGER RESTORE RESET F1 F2 F3 F4 CHIP FWD CLNT DOWN AUX CLNT OVERRIDES CLNT UP +B +A +X +Z –Y –X –A –B –Z +Y CURSOR Goodheart-Willcox Publisher Figure 9-22. The Tool Offset Measure button on a Haas controller.