Why G04 Dwell Command used in CNC Programming

G-Code G04 Dwell Command.

G-CODE FORMAT:  

N_G04 X2.0 (Excluding fixed cycle)

N_G04 P2000 (including fixed cycles)

N_G04 U2.0   (only for lathes)

(1 S= 1000 milliseconds)

 Description:

G04 G-code is a Dwell command which may also call as pause in the program, the time period specified in the program any axis can be stopped without affecting the other commands and functions. Dwell during the cut is mainly used for breaking chips in the drilling and counter boring. Dwell can also be used in turning and boring to eliminate the physical marks left on end of the cutting tool.

Calculating dwell:

Minimum dwell is the time required to complete one revolution of the spindle.   

Minimum Dwell (sec) = 60/r/min

For example, calculating Dwell for 600 spindle revolution, divide 60 by r/min I.e, 60/600=0.1seconds.

Calculating Dwell Sec:

Dwell sec = 60 x N / RPM

Where     60 = Number of minutes.

                N= Number of spindle rotations.

                RPM= current spindle speed.

Example: Dwell sec=60 X 3/600 = 0.3

Calculating Dwell Sec:

Dwell rev = RPM x Dwell sec/ 60

Example: Dwell rev = 600 X 0.3 /60 =3 rev

  

Note:

1.        The G04 code is not a modal g-code.

2.        Dwell command is always completed before the next operation begins.

3.       The actual time specified in dwell is either seconds or milliseconds.

4.       Dwell can also be used in the fixed cycles together with cycle data, not in a separate block.

5.    When using Dwell no axis motion will takes place.

6.      Fixed cycles like G76, G82, G88, and G89 in which dwell can be used.

7.     Cycles like G84 and G74 Dwell can be used only by parameter setting. Example:

Example:

N170 G90 G0 Z5

N171 G82 X12 Y6 R2 Z-4 P300 F100 (Dwell command 0.3 seconds)