G98/G99 Introduction to R-planes
OBJECTIVES
After completing this unit, you should be able to:
- Identify and describe two types of R-planes used in CNC codes
- Identify the purpose of G98 and G99 CNC codes
R is for Retract
or
R is for Return
or
R is called “Rapid” because tool rapids to the return plane
Canned cycles require different types of information. Let’s first look at places or planes where we want to put our cutters.
There are two planes to understand:
INITIAL PLANE: This is the plane used for rapiding around the workpiece. This plane should always be set so the cutter does not crash into the workpiece. In industry, CNC operators must also be aware of any clamps or other fixture which olds the workpiece to the table that can be struck by the tool as it moves around the part.
On Fanuc controlled or Haas machine, the initial plane is defined as the last Z position before the canned cycle is called. So in the sample code below:
Z1.00 would be considered the INITIAL PLANE because it is the last Z position prior to the canned cycle command of G81.
R PLANE : The R plane is defined as the plane at which the (drilling, tapping, and/or boring) operation begins. So basically the tool rapids from the Initial Plane to the R plane and then starts the operation. The R plane is defined in the canned cycle command line. So in the example code below, R.050 is defined as the R plane. It is the point where the cutting operation would begin.
From the code, the tool would rapid from the Z1.00 initial plane to the Z.050 R plane.
After drilling
G98 is active by default
- Retracts to last Z move before drilling
G99 must be specified
- Retracts to specified R value
Watch this 7:49 video, “How Canned Cycles Work with G98 & G99 – Haas Automation Tip of the Day” .
G98 and G99 change the way the canned cycles operate.
When G98 is in command, the Z-axis returns to the initial start plane after each hole (programmed) in the canned cycle. This command helps with the tool position up and around different areas of the part and/or its fixtures and clamps. Be sure to watch the video above for a demonstration.
When G99 is in command, it is in the block before the canned cycle in the code.
It controls the return after the cut is finished. The Z-axis returns to the R (rapid) plane after each hole. This plane is the clearance plane for the next X Y location.
