Copyright Goodheart-Willcox Co., Inc. 190 CNC Manufacturing Technology The toolpath in our example needs to move to the left-hand side of the plan geometry, to compensate for climb cutting with end mills in a contour. There are two ways to make this adjustment. The first way requires recalcu- lating all movements and positions. Since this program uses a 1/2″ end mill, this potential solution requires moving the radius of the tool, or .250″, to the left of all the geometry. This will be time consuming and lead to possible programming errors. The second solution is to let the computer do the calcu- lations by using G code commands. Turn on cutter compensation left (G41) in the first move into the part, and then cancel cutter compensation (G40) on the exit move off the part. Review the adjusted program and new results: O3283 Program number G20 G17 G40 G80 Default line G91 G28 Z0. Send machine to Z0. home T1 M6 (1/2” End mill) Tool change to tool #1 G0 G90 G54 X−.5 Y0. M3 S5000 Rapid, G54 WCS, go to XY position, spindle on to 5 000 rpm G43 H1 Z2. M8 Height offset 1, move to Z2., coolant on G01 Z−.5 F30. Feed to Z−.5 at 30 inches per minute G41 D1 X0. Turn on cutter comp left tool 1, move to X position Y3. X5.5 X6.0 Y2.5 X and Y on same line create angle Y0. X0. G40 X−.5 Turn off cutter comp, exit move off part G0 Z1. Rapid to Z1. M9 Coolant off G91 G28 Z0. M5 Incremental mode, home in Z, spindle off G28 Y0. Home in Y M30 Program rewind The resulting toolpath appears in Figure 9-10. This is the part the program should produce to match the plan. Without cutter compensation, the programmer must calculate the coordinates for the path of motion of the center of the tool. With cutter compensation, the programmer simply needs to enter the coordinates for the geometry of the part. The simple addition of G41 on the initial entry move and G40 on the exit move has moved the toolpath outside the part. There are two keys to make this work. First, for the control to correctly offset the tool, the initial entry move has to be larger than the tool radius. For example, this part is using a 1/2″ tool, so the initial move must start more than 1/4″ off the part. A good practice is to make the first positioning move the same distance as the tool diameter. This program started at X−.5 and moved Goodheart-Willcox Publisher Figure 9-10. This contour toolpath, which includes cutter compensation, will produce the part as specified on the print. Toolpath