CNC Programming & Machine Operation 2 — Questions and Answers
Question 1: What does the CNC G02 code command the machine to do?
- Move in a straight line
- Perform a clockwise circular interpolation (Correct answer)
- Perform a counterclockwise circular interpolation
- Return to the home position
Correct answer: Perform a clockwise circular interpolation
G02 commands the machine to move in a clockwise arc, while G03 commands counterclockwise arc motion.
Question 2: In CNC programming, what is the purpose of the I and J address words used with G02/G03?
- They specify the tool number and offset
- They define the incremental distance from the arc start to the arc center (Correct answer)
- They set the feed rate and spindle speed
- They indicate the depth of cut and step-over distance
Correct answer: They define the incremental distance from the arc start to the arc center
I and J are incremental offsets from the arc start point to the arc center in the X and Y axes respectively.
Question 3: Which modal group do G00 and G01 belong to, and what does this mean?
- Group 1; only one code from the group can be active at a time (Correct answer)
- Group 2; both can be active simultaneously
- Group 3; they cancel each other after one block
- Group 0; they are non-modal and must be repeated each block
Correct answer: Group 1; only one code from the group can be active at a time
G00 and G01 are both in modal Group 1 (motion group), so activating one cancels the other.
Question 4: A CNC operator needs to drill 10 holes using a canned cycle. Which code initiates a standard drilling canned cycle?
- G80
- G81 (Correct answer)
- G83
- G76
Correct answer: G81
G81 is the standard drilling canned cycle that plunges to depth and retracts at rapid speed.
Question 5: What is the function of G83 in CNC machining?
- Boring cycle with spindle stop at bottom
- Peck drilling cycle that retracts fully to clear chips (Correct answer)
- Tapping cycle with controlled feed and speed
- Reaming cycle for finishing holes
Correct answer: Peck drilling cycle that retracts fully to clear chips
G83 is a peck drilling cycle that fully retracts to the R plane between pecks to clear chips from deep holes.
Question 6: When programming with tool length compensation using G43, what does the H address specify?
- The tool diameter offset number
- The tool length offset register number (Correct answer)
- The height of the workpiece
- The coolant nozzle height position
Correct answer: The tool length offset register number
H specifies the tool length offset register number stored in the controller's offset table.
Question 7: In a CNC program, what does the block 'N100 G28 G91 Z0' accomplish?
- Sets the work coordinate origin at the current Z position
- Returns the Z axis to the machine home position incrementally (Correct answer)
- Cancels all tool length offsets and moves Z to zero
- Activates the Z-axis reference return mode and locks it
Correct answer: Returns the Z axis to the machine home position incrementally
G28 with G91 (incremental mode) and Z0 commands the Z axis to return to the machine reference (home) position through the current position.
CNC Programming & Machine Operation 2
What does the CNC G02 code command the machine to do?