Threadmill leadout question (flat XY or helical?)

will gilmore · May 18, 2018

I don't have cutter compensation but I can program helical movement. My question is: on the lead out from the cut does the cutter move in a flat arc in XY (Z is axial to thread) or does the cutter arc out in a helix so as to be tangent to cutting tool path. Today I'm working on 1/4-20 but I'm curious about best practices.

I've successfully programmed single point threads on a through hole where I started the helix below the material and ended above. I've done a NPT thread with a multipoint tool. I sketched the helical leadout in CAD and everything was fine. Downside is I had to go back to CAD a couple of times to dial in the fit so I'd like to be able to adjust the program at the machine. Programming the helical leadout will take some thought.

brian.pallas · May 18, 2018

Helical is preferred (in my mind at leat lol) but flat works just fine also. Seems like helical leadout would be smoother on the cutter, but practically I am not sure if it makes a noticeable difference.
I know a lot of the threadmill makers have on their website a page that will make your program for you. Might check those out. Could be an easy way to get the helical leads with out all the hand work?

Nami · May 18, 2018

This is what I do. Start at bottom. The initial and last Z up is the thread pitch divided by 4, and the initial and last K is the thread pitch divided by 2.

;6-32 THREADMILL
M1
:T8 M6
S6000 M3
M8
G0 Z6
G0 X-0.51 Y-0.014
G0 Z0.6
G1 Z0.1 F80
G1 Z-0.122 F2
G1 Y-0.015
G3 X-0.495 Y-0.015 Z-0.1141875 I-0.5025 J-0.015 K0.015625
G3 X-0.495 Y-0.015 Z-0.0829375 I-0.51 J-0.015 K0.03125
G3 X-0.495 Y-0.015 Z-0.0516875 I-0.51 J-0.015 K0.03125
G3 X-0.495 Y-0.015 Z-0.0204375 I-0.51 J-0.015 K0.03125
G3 X-0.495 Y-0.015 Z0.0108125 I-0.51 J-0.015 K0.03125
G3 X-0.51 Y-0.015 Z0.018625 I-0.5025 J-0.015 K0.015625
G1 X-0.51 Y-0.016
G1 Z0.1 F20
G0 Z0.6

will gilmore · May 18, 2018

Thanks. In my mind a flat leadout would cut across the threads. I discounted the code generators because they are all based on cutter comp but I can probably get the z component of the helical lead out.

Larry Dickman · May 18, 2018

If you climb cutting (and, why wouldn't you be) you're out of the hole for the lead out, so it doesn't mean shit.

will gilmore · May 18, 2018

Nami said:
This is what I do. Start at bottom. The initial and last Z up is the thread pitch divided by 4, and the initial and last K is the thread pitch divided by 2.

;6-32 THREADMILL
M1
:T8 M6
S6000 M3
M8
G0 Z6
G0 X-0.51 Y-0.014
G0 Z0.6
G1 Z0.1 F80
G1 Z-0.122 F2
G1 Y-0.015
G3 X-0.495 Y-0.015 Z-0.1141875 I-0.5025 J-0.015 K0.015625
G3 X-0.495 Y-0.015 Z-0.0829375 I-0.51 J-0.015 K0.03125
G3 X-0.495 Y-0.015 Z-0.0516875 I-0.51 J-0.015 K0.03125
G3 X-0.495 Y-0.015 Z-0.0204375 I-0.51 J-0.015 K0.03125
G3 X-0.495 Y-0.015 Z0.0108125 I-0.51 J-0.015 K0.03125
G3 X-0.51 Y-0.015 Z0.018625 I-0.5025 J-0.015 K0.015625
G1 X-0.51 Y-0.016
G1 Z0.1 F20
G0 Z0.6

Thanks for the code. 2 questions: 1) it looks like you do 2 turns. why? 2) I don't understand the use of K in G3

Larry Dickman said:
If you climb cutting (and, why wouldn't you be) you're out of the hole for the lead out, so it doesn't mean shit.

Not with multipoint tool.

sinha · May 18, 2018

will gilmore said:
I don't understand the use of K in G3

Not needed in Fanuc G02/G03 for Z-axis helix.

Larry Dickman · May 18, 2018

will gilmore said:
Not with multipoint tool.

Ah, you are right. So my answer then would be to use a helix move.

will gilmore · May 18, 2018

sinha said:
Not needed in Fanuc G02/G03 for Z-axis helix.

Ok, but why is the z up 1/4 pitch and the k 1/2 pitch. 1/2 pitch makes sense to me for a 1/2 circle lead in. After that the Z ups and Ks match.

sinha · May 18, 2018

You are right. Half pitch for half circle, and quarter pitch for quarter circle.
No K needed. Only Z to be specified properly.

will gilmore · May 18, 2018

Thanks everyone. I have it working now.

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