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G41 and G42 Help Request! Example given
« on: January 18, 2009, 08:21:51 AM »
Hi, I'm having trouble with tip radius comp in Mach3Turn and I'd really appreciate some help.

Tool table is set with Tool 1 as a normal DCMT tip cutting to the left with a 0.4mm radius, no offsets and "tip direction" is set to 1.

Working in Diameter mode and using R3.042.020.

My G-Code (pls. excuse my comments):

(MT2 Test Taper)
g21 (metric)
g61 (exact stop)
g18 (xz)
g90 (absolute)
g40 (off radius compensation)
g95 (mm per revolution feed mode)

T0101 M06 (Select Tool 1 data and do a tool change)
M03 S1000 (Start Spindle at 1000rpm)

G0 x0 Z3.0 (move to safe position)
G41 (Left tool tip compensation, rad is from the tool table for tool 1)

g1 x0.0 z0.0 F0.1
g1 x8.0 z0.0
x10.0 z-1.0
x10.0 z-10
x12.53 z-10.0
x14.53 z-11.0
x17.78 z-76.065
x17.78 z-78.72
x19.0 z-79.5
x19.0 z-97.0

G40 (off radius compensation)
M05 (Stop Spindle)
M30 (End and Rewind)

If I remove G41, it shows the profile I want in the path display, but it won't cut the right size as the G1 points are the finished article surface.

If I use G41, then I get the attached:


I've tried changing abs and inc IJ mode with no effect. Did I miss something? Any ideas?

Also, is there information anywhere on "tip direction", I can't find that.

Just got spindle feedback and threading working a treat (mesmerising) but this G41/42 has me stumped.

Final point, why do I get the jagged edges in the tool path display of the work piece? Is there a setting for this?

Thanks very much for your help.

Richard.

Offline Hood

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Re: G41 and G42 Help Request! Example given
« Reply #1 on: January 18, 2009, 09:19:29 AM »
Use  R3.043.000 as that is the version tool comp has been sorted for Mill . Not sure if comp works properly in turn even with that version so you will need to test but certainly have more chance.
 In your pic above however I think you may be needing the reversed arcs box the opposite way from what  you have it. You will see this from Config menu, ports and pins then Turn Options.

Hood

Edit, just looked at the pic full size and I see the toolpath is showing the  comp so disregard the arcs reversal.
« Last Edit: January 18, 2009, 01:48:50 PM by Hood »

Offline jimpinder

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Re: G41 and G42 Help Request! Example given
« Reply #2 on: January 18, 2009, 01:33:32 PM »
As with Hood - I am not sure whether the compensation has been sorted in turn, or not.

The "jagged" edges on your tool display are becasue you have a a G61 - exact stop instruction in your code.

In continuous velosity mode, one line begines, before the last line finished, and the software medls the acceleration and deceleration into one continuous movement. In exact stop, it does what it says - one line comes to a stop before the next line starts.

CV tends to smooth out arcs (it never reaches the finish and start points), but constant velocity cuts it as you wrote it.
Not me driving the engine - I'm better looking.
Re: G41 and G42 Help Request! Example given
« Reply #3 on: January 18, 2009, 03:45:15 PM »
Thanks for your help Hood and jimpinder,

I updated to 3.043.000 and shortened my test a little:

(Diameter Mode)
g21 (metric)
g18 (xz)
G61 (exact)
g90 (absolute)
g95 (mm per revolution feed mode)

T0101 M06
M03 S1000
g0 x0.0 z0.0

g41
g1 x8.0 z0.0 F1.0
x10.0 z-1.0
x10.0 z-10
x12.53 z-10.0
x14.53 z-11.0
x14.53 z-15
g0 x14.53 z0
g0 x0
g40

M05 (Stop Spindle)
M30 (End and Rewind)

I ran this without the G41 first and tried various Tip Directions and this provided a fixed offset as per the "LatheOffsetsSystem.doc" that I had. So, the Tip Direction seems to work. But I set this to zero to not confuse things.

With G41 set and with zero tip radius, no problems (but obviously no offset).

With 0.4 tip radius in the tool table, it stops just before finishing the G0 X8 ... In fact, any tip radius over 0.01 crashes it.

Does G41 and G42 work yet in Mach3Turn vn. '42 and '43?

Is anyone using them in Turn? I'd be really grateful to see some working examples of G-code - I'm sure its probably an error in my set-up somewhere.

Or, is there a better way? I want to try and do it in G-code with the off-set calculated in Mach3 and I assume G41 and G42 is the way?

Thanks, Richard.

Offline Hood

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Re: G41 and G42 Help Request! Example given
« Reply #4 on: January 18, 2009, 04:50:36 PM »
Sorry dont use offsets on the lathe, my CAM calculates a true path, the guy who may know is Graham Waterworth but he is at  cabin fever at the moment.
Hood

Offline RICH

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Re: G41 and G42 Help Request! Example given
« Reply #5 on: January 18, 2009, 05:09:17 PM »
RICHARD,
Compensation has been changed in mill. In mill you need to have a lead in and lead out > 1/2 tool diameter before and after g41 & g42. The next version of the wizards ( New Fangled Solutions ) will be fixed / updated  for the new compensation. Never used / tried compensation while using turn so don't know if it even worked in other versions. Turn will be recieving attention in the upcoming months.
RICH
Re: G41 and G42 Help Request! Example given
« Reply #6 on: January 19, 2009, 04:19:36 AM »
Thanks Rich and Hood,

I'll try and learn a little more on this, try out a few different approaches and keep watching this forum on G41. If I discover anything, I'll let you know.

At the moment, yes, I don't think G41 and G42 are working in Turn, at least, not as I've read they might. If anyone knows otherwise, please share how!

Richard.

Re: G41 and G42 Help Request! Example given
« Reply #7 on: January 20, 2009, 08:25:46 AM »
Hi.

More or less four months ago, I had a work were I receive a Fanuc Gcode for a lathe machine, and due to particular reasons I am not able to change the original code (I can and I should not), but I must use it on my mach3 machine. So I began to work on a software that uses the fanuc gcode with and without compensation (G41 G42 G76 ....) and outputs a code that is ready to use on mach3. It is almost stable and I a very few bugs are known.

I do not know if this is could be used for many users, but if so, and since it gave me many, many work I could think in sell it for a small fee. Or if interests Mach developers. If anyone that is reading this post is able to give me the answers, please let me know.
How many lathe users are there ?
Re: G41 and G42 Help Request! Example given
« Reply #8 on: January 20, 2009, 08:46:48 AM »
One thing important that I did not mentioned (and I should tell before my client reads the last post !)

My client is thinking in buying the source code and the right to use the software, so only after a decision from him, I could sell the software. Nevertheless it would be fine to know if there are people interested in it.