TOMATECH AUTOMATION
G92 X58.7 Z-28 F3 J3 K1; (Machine thread with 4 times cutting, the first tool infeed
1.3mm)
X57.7 ; (The second tool infeed 1mm)
X57; (The third tool infeed 0.7mm)
X56.9; (The fourth tool infeed 0.1mm)
M30;
3.21.7 Multiple thread cutting cycle G76
Command format: G76 P(m) (r) (a) Q(△dmin) R(d) ;
G76 X(U) Z(W) R(i) P(k) Q(△d) F(I) ;
Command function: Machining thread with specified depth of thread (total cutting
depth)is completed by multiple roughing and finishing, if the defined angle of
thread is not 0°, thread run-in path of roughing is from its top to bottom,
and angle of neighboring thread teeth is the defined angle of thread. G76
can be used for machining the straight and taper thread with thread
run-out path, which is contributed to thread cutting with single tool edge to
reduce the wear of tool and to improve the precision of machining thread.
But G76 cannot be used for machining the face thread. machining path is
shown in Fig. 3-48(a):
Relevant definitions:
Starting point(end point): Position before block runs and behind blocks run, defined by
A point;
End point of thread(D point): End point of thread cutting defined by X(U) Z(W) .The tool
will not reach the point in cutting if there is the thread run-out path;
Starting point of thread: Its absolute coordinates is the same that of A point and the
different value of X absolute coordinates between C and D is i(thread taper with radius
value). The tool cannot reach C point in cutting when the defined angle of thread is not 0°;
Reference point of thread cutting depth (B point) : Its absolute coordinates is the
same that of A point and the different value of X absolute coordinate between B and C is
k(thread taper with radius value).The cutting depth of thread at B point is 0 which is the
reference point used for counting each thread cutting depth by the system;
Thread cutting depth: It is the cutting depth for each thread cutting cycle. It is the
different value(radius value, without signs) of X absolute coordinate between B and
intersection of reversal extension line for each thread cutting path and straight line BC.
The cutting depth for each roughing is n ×△d, n is the current roughing cycle times, △d is
the thread cutting depth of first roughing;
Thread cutting amount: Different value between the current thread current depth and
the previous one:( n − n −1 ) ×△d;
End point of tool retraction: It is the end position of radial (X) tool retraction after the
thread cutting in each thread roughing, finishing cycle is completed, defining with E point;
Thread cut-in point: Bn (n is the cutting cycle times) is the actual thread cutting starting
point in each thread roughing cycle and finishing cycle, B1 is the first thread roughing
cutting-in point, Bf is the last thread roughing cut-in point, Be is the thread finishing
cutting-in point. Bn is X, Z replacement formula corresponding to B.
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