Would you mind giving me a sample G76 line of code for say a M10 x 50mm so I can do further tests then I can learn how to program it. I use mm for the lathe.
This is a template so will cover whatever thread size
(ignore the M code, that is just a local one to set the pulley number for correcting the speed)
Code:
;; Threading with G76
;; Speed of 300 is stable and only requires F450 to cut 1.5mm thread
;; P[itch]
;; Z[FinalExtent] - Ensure there is an overrun element so that deceleration happens beyond end of thread, 3 mm sufficient in this example
;; I[ThreadPeakOffset - cant be 0, neg for external pos for internal, if diameter is critical you can add PeakOffset to Diameter to negate this value]
;; J[FirstCutDepth - positive offset]
;; R[DepthDegression 1.0 is constant depth 2.0 is constant area 1-2 depth decreases & area increases 2> area decreases]
;; K[FullThreadDepth positive offset beyond I for root of thread]- Q[CompoundSlideAngle eg 29.5]
;; H[SpringPasses at full thread depth] E[TaperAmount in units - normally 0] L[Taper- L0 None L1 entry L2 Exit L3 Both]
#<_Diameter>=40
#<_Z_LeadIn>=15
#<_Pitch>=1.5
#<_Z_Finish>=-15
#<_PeakOffset>=-0.001
#<_First_Cut_Depth>=0.01
#<_Depth_Regression>=1.0
#<_ThreadDepth>=1.5
#<_CompoundSlideAngle>=0
#<_Spring_Passes>=2
#<_TaperAmount>=0
#<_TaperType>=0
#<_Feed>=1.5
#<_Speed>=300
G18 G21 G40 G49 G54 G80 G95
G90 G7
M101 P3 (SET PULLEY SETTING 3 FOR GOOD TORQUE)
F#<_Feed> S#<_Speed>
M3
G4 P10
M7
(GO TO OS DIA AND Z LEAD IN
G0 X#<_Diameter> Z#<_Z_LeadIn>
G76 P#<_Pitch> Z#<_Z_Finish> I#<_PeakOffset> J#<_First_Cut_Depth> R#<_Depth_Regression> K#<_ThreadDepth> Q#<_CompoundSlideAngle> H#<_Spring_Passes> L#<_TaperType>
G00 X45
M9
M5
G28
M2
The Z lead in figure is quite important, because that is what enables everything to be aligned and at the right speed before cutting commences
I normally allow 10x the thread pitch roughly, so 15mm for a 1.5mm pitch
if you reverse the spindle say 10 revs the go forward again the thread does not start again until the 10revs have been done.
I am not sure why anyone would ever do that, but I suspect it is because you have both A and B channels on your encoder,
so it knows you have moved away from position in reverse and is bringing you back to where you were, before starting.
regards
