CNC G-Code and Programming Flashcards
6 cards from real CNC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CNC G-Code and Programming flashcards as text
What is the purpose of a G54 command in CNC programming?
Answer: Selects work coordinate system 1
G54 selects Work Coordinate System 1, which tells the machine where the workpiece origin is located on the table.
Which canned cycle code is used for a standard drilling operation in CNC?
Answer: G81
G81 is the standard drilling canned cycle that drills to a specified depth and retracts at rapid feed rate.
What does the R-value represent in a canned drilling cycle?
Answer: Retract plane height above the work surface
The R-value in a canned cycle specifies the retract plane, which is the height the tool returns to between drilling operations.
In CNC programming, what does G96 activate?
Answer: Constant surface speed (CSS) mode
G96 activates Constant Surface Speed (CSS) mode, which automatically adjusts spindle RPM as the tool diameter changes.
Which character is used to indicate a program end and rewind in a CNC program?
Answer: M30
M30 ends the CNC program and rewinds it to the beginning, resetting the program pointer for the next run.
What is the purpose of using subroutines (M98/M99) in CNC programming?
Answer: To repeat a set of operations without rewriting the code
M98 calls a subroutine and M99 returns from it, allowing repeated patterns or operations to be written once and reused.