Programming & Machine Operation Flashcards

A machinist is setting up a CNC machining center and needs to establish the work coordinate system. Which G-code group handles work offset selection?

Answer: G54–G59

G54 through G59 are the standard work coordinate system offsets that define the workpiece datum relative to the machine home.

What does activating G41 do in a CNC milling program?

Answer: Applies cutter radius compensation to the left of the programmed path

G41 applies cutter radius compensation (CRC) to the left of the programmed tool path, which is used for conventional milling on the outside of a part.

Which code cancels cutter radius compensation in CNC milling?

Answer: G40

G40 cancels any active cutter radius compensation (G41 or G42) and returns the tool to the programmed centerline path.

In CNC subprogramming, which M-code is typically used to call a subprogram on Fanuc-style controllers?

Answer: M98

M98 calls a subprogram, with the P address specifying the subprogram number, and M99 in the subprogram returns control to the main program.

A CNC program includes the line 'M98 P0050 L4'. What does the L4 parameter specify?

Answer: The number of times the subprogram should be repeated

The L address in an M98 block specifies the number of times the subprogram is to be executed (repeated).

What is the purpose of a fixture offset (G54-G59) in CNC machining?

Answer: To define the part zero location relative to machine zero for each setup

Fixture offsets define the X, Y, Z distance from machine zero to the workpiece datum, allowing programs to reference the part geometry directly.

During setup, an operator uses an edge finder to locate a workpiece corner and finds the X machine position reads -8.4325 at the part edge. After accounting for the 0.200" edge finder diameter, what X offset value is entered into G54?

Answer: -8.5325

The edge finder center is 0.100" away from the actual edge, so the true edge X position is -8.4325 - 0.100 = -8.5325.