I need some help.
Each pass is getting smaller not bigger like it needs to do.
I put this together myself.
G76 P000060 Q0025 R.0005
G76 X1.562 Z-1.250 P0695 Q0005 R-.0387 F.0869
The second line the R value is negative which makes the taper go the right way but nothing I have done so far will make each pass go deeper.
Its bored out to 1.5
What am I doing wrong?
As alluded to by wmpy and Booze Daily, the control determines the direction to apply the DOC by comparing the current X position of the Threading Tool and the X coordinate specified in the second G76 Block. If the Tool is at an X position less than the X coordinate specified in the G76 Block, the DOC will be applied in a plus direction.
In your first G76 Block, you have the minimum DOC increment set at 0.0025", but in the second G76 Block, the first DOC pass is set at 0.0005", which is less than the minimum DOC set in the first G76 Block. The G76 Cycle sets each successive DOC using the following algorithm:
DOC = d x SQR(N)
d = first pass DOC set in the second G76 Block
N = the Nth number of the Threading Pass (1st, 2nd, 3rd etc.)
The control continues applying the DOC based on the above algorithm until the DOC calculated for the next pass, minus the DOC for the previous DOC is less than the minimum DOC set in the first G76 Block.
Accordingly, you should make the first pass DOC at least as large as the minimum DOC set in the first G76 Block. Rule of Thumb, is that the First Pass DOC should be whatever the work-piece set up and the Threading Tool can handle. Of course, you would start off with an initial DOC that is conservative and then increase it to achieve the best cycle time and tool life. Having the whole thread cut with a DOC that doesn't exceed 0.0025" is just wasting time.
Notwithstanding that you say that the taper amount (radius value) has been set as a negative value and you're getting the taper applied in the correct way, this is not the way in which it should be applied, if its a Fanuc control and Negative is towards the centre line of the machine.
For an External Thread, the Minor Diameter of the Large Diameter of the Taper is specified with the X coordinate of the second G76 Block and the Taper specified as the difference in the Thread Radius in a Negative direction.
For an Internal Thread, the Major Diameter of the Small Diameter of the Taper is specified with the X coordinate of the second G76 Block and the Taper specified as the difference in the Thread Radius in a Positive direction.