[mystiks]

Hello,

Friend has a problem when they turn plastic material in their lathes, they havent found a way to make the chips break, they've had to mill small grooves around the part to make chips break.

I havent tried to give dwell motions within turning cycles, so i was wondering how different controls react to these?, though i havent turned nor milled any plastic myself and i doubt if even a little dwell would help with the problem?.

I dont have the exact shape they try to turn, was only told that it's not for finished shape so any small errors are acceptable.

Small simple example for fanuc..

G0 X81 Z2
G71 U3 R1
G71 P1 Q2
N1 G0 X50
G1 Z-20
G4 X1
G1 Z-40
G4 X1
G1 X80 Z-60
N2 X81

[beege]

I use a G74 for straight cuts.

G74R.003
G74X(target diameter)Z(target length)

There are two others letters used, but I'm not sure (from home) what they are, but they are for depth of cut and length before retract, and the first line R is the distance to retract after each advance. Works great to break up those plastic chips!

[sinha_nsit]

I doubt if dwell would work inside G71. It is not mentioned in Fanuc manuals, nor have I tried this. If it does work, please let us know.

[dcoupar]

Apparently you can include a G04 within the finish shape definition.

[sinha_nsit]

I believe G04 would be used by G70. but not by G71. Somebody may try and confirm.

[mystiks]

Actually tried the dwell motions within G71 cycle and it worked, though i only had one cut and used simulation. Have to try again with multiple cuts on same cycle, and see, if it only applies the dwells on final cut.

One can always break the profile in multiple parts with cam, and do multiple cycles, but i wouldnt count that as solution if your doing multiple different parts, would have to find a way that can be applied easily while hand programming.

Thanks for replies, just seemed bit extreme solution to mill grooves for chip breakage, but then again i have no experience with plastic. And always trying to learn something new

[sinha_nsit]

Have to try again with multiple cuts on same cycle, and see, if it only applies the dwells on final cut.

This is what I suspect.
G71 may ignore G04 while roughing, but consider it during the final step-removal operation.
Simulation cannot be relied upon 100%, especially if it is a third-party software.

[xyzer]

I use a G74 for straight cuts.

G74R.003
G74X(target diameter)Z(target length)

There are two others letters used, but I'm not sure (from home) what they are, but they are for depth of cut and length before retract, and the first line R is the distance to retract after each advance. Works great to break up those plastic chips!

I have used this method also for machining copper, tantalum, Niobium. The concept of breaking a chip is in another world.

G00X5.1
G74R0.005
G74X5.1Z-0.105P0000Q0150R0.010

G0X5.0Z-.75
G01
G74R0.005
G74X5.0Z-.105P0000Q0150R0.010

I called it a stutter cut