This pure dry goods explains three contents:
 
1. What is a variable pitch thread.

2. G code for variable pitch thread

3. Macro program of variable pitch thread

 
1. What is a variable pitch thread

The so-called variable pitch thread means that the pitch is not fixed, but gradually changes along the axis.

 
Variable pitch threads often have two forms:

1. Constant pitch thread with variable pitch, (as shown in the figure below):




 That is: the width of the tooth does not change, the groove gradually changes

2. Equal groove width variable pitch thread (as shown in the figure below):





That is: the groove width does not change, the tooth width gradually changes
 
2. G code for machining variable pitch thread (fanuc)

G34 X__ Z__ F__K__

1. F is the initial pitch of the processed variable pitch thread.

2. K value is the increment or decrement of the pitch when the spindle rotates one circle.

If K is positive, then the pitch is increasing, and K is negative, that is, decreasing.



For example: machining a thread with equal groove width and variable pitch on a workpiece with a diameter of D50;

Starting pitch: F3.25;

When the spindle rotates once, the pitch increases by 0.5mm

 

The procedure is as follows

%

O0001 (sosweetmum)

T0101

S500 M03

G0X47 Z20

G34 Z-100 F3.25 K0.5 (first radial cut)

G0X60.

Z20.

X44.8

G34 Z-100 F3.25 K0.5 (2nd radial cut)

G0X60.

Z20.

X44.

G34 Z-100 F3.25 K0.5 (3rd radial cut)

G0X60.

Z20.

M01

M30

%
Note: The above procedure is to use the forming knife and the layered car, and the calculation is based on 3 knifes for reference.


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Actually, the equal area cutting method can be used, or the thread with large pitch can be written by alternate borrowing method; how to use the macro program to write?