G94 is one of the two feed modes used by the computerized numerical controllers (CNC). From routing, milling to waterjet, lasers, etc., UPM (units per minute) feed mode is used most commonly. These modes could vary in terms of units- G21 for mm/minute or G20 for inches/minute. G94 code instructs the machine controller to feed in UPM.
G94 is also useful to program the machine control in terms of UPR (units per revolution) to conduct lathe works. Plus, the same can be done for inches or cm per revolution. However, the probability of a mill machine to use the UPR programming is quite less if it’s not a Mill-Turn style machine. On the other hand, the use of both UPR and UPM programmings is usually seen in the lathes.
What is a G94?
G94 code is the programming used by the CNC machines that instructs the CNC control to feed in UPM (units per minute).
G94 is a modal G-code programming which tells the CNC controller to decode the feed command in terms of:
- mm per minute or inches per minute- for inches/minute or mm/minute for linear movement
- degrees per minute for circular movements
- mm per minute or inches per minute for the mixture of both roratory and linear moves.
When a composite movement of linear and rotational is programmed, the time taken by the rotary moves becomes equal to the linear moves.
The function of G94 selects the feed “F” either in inches per minute or mm per minute. When G94 code is running active, the feed values will be coded as: F50, F150, F500, F2000, and so on.
G94 G-code (feed per minute) is applied to conduct the movements with work feed while the spindle is not in motion, or when it’s required to release the spindle revolution axis feed. For instance, while using live tooling or milling with motor-based tools.
In order to set the feed rate mode to UPM by using G94 G-code programming:
The controlled point of the machine control must move at (MMPM) mm per minute, or IPM (inches per minute) for a particular number of time, based on the type of length unit being used.
It will be considered an error if:
the new active feed rate is not displayed even after switching to G94 code.
Explanation of the Code Using an Example:
Let’s consider the Fanuc G94 One Pass Facing Cycle:
Before getting directly into the example, it’s important to know that Fanuc G94 modal G-code is applied in rough facing.
Although Fanuc G94 facing cycle is applicable for simple one-pass facing, multiple passes can be accomplished by specifying the location of Z-axis to allow additional passes.
It is quite easy and simple to program and use the Fanuc G94 facing cycle. Here are the following G94 G-code parameters which are to be used in the following program below:
G94 X… Z…
X: end limit in X-axis
Z: end limit in Z-axis
Now, we will check an demo program of CNC code programming with Fanuc G94 facing cycle:
N10 G50 S2500
N20 G96 S180 M03
N40 G00 X55.0 Z2.0 T0101
N50 G94 X15.0 Z-2.0 F0.2
N90 G00 X200.0 Z200.0 T0100
Here is the detailed explanation of each of the CNC program blocks of the above programming:
N40 : implies the tool’s starting position.
N50 : X and Z are the destination values associated with the G94 facing cycle for the cut facing.
N60 : G94 modal G-code is the code that continues to remain in effect unless it is replaced or contradicted by another G-code. That means the G94 turning cycle stays active as long as no other command like G00, G01, or so, is fed to the above programming.
However, as the N60 CNC coding block only displays the Z-axis values, it means the G94 facing cycle will remain in effect and will make the next facing cut, in which the value of the X-axis will remain unchanged but the Z-axis value will be set to -4.0
N70 : the value of Z-axis for the third facing cut will be set to -6.0
N80 : for making the fourth facing cut, the Z-axis value will be set to -8.0
N90 : this program block of CNC indicates an opposing G-code, that is G00 code to contradict G94, which means that the G94 facing cycle of Fanuc is ended. Now, the tool will start to move at a rapid speed to X200 Z200.
Well, that was all about g94 code which you might find useful while setting the CNC machine to conduct any core industrial tasks as mentioned at the beginning of the article.