Machsupport Forum

G-Code, CAD, and CAM => G-Code, CAD, and CAM discussions => Topic started by: Deano on February 12, 2013, 10:54:28 AM

Title: Mach3 adding extra loops in a string of arcs
Post by: Deano on February 12, 2013, 10:54:28 AM
Any ideas why extra "hooks and loops" show up when routing a part outline consisting of a series of arcs? I've been routing about 15 or 20 different outlines
(guitar pickguards) successfully, then suddenly a new wrinkle shows up.  Cad files are created in Flexisign, (poly line curves) exported as .dxf, to BobCad,  .dwg, cleaned up to make arcs tangential and features more dimensionally correct, then BobCam to generate gcode with Mach3 post. 
I struggled through lots of learning re. lead-ins/-outs, and issues with tool path offsets (thanks to many good forum posts as resources)
I can't see any difference in the code from other parts of the same outline. I've zoomed in on the .dxf and .dwg drawings and can see no breaks or flaws in the joining of the arc endpoints. I've tried re-starting Mach, reloading code, re-creating code.  So far, it's the only drawing to show the problem.
I hope the attached files are enough info for a clear understanding. Thanks a bunch.
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Tweakie.CNC on February 12, 2013, 11:52:52 AM
Hi Deano,

I am a bit mystified - in your Mach3screenshot.doc where are the 'hooks and loops' which you are referring to please ?

Tweakie.
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Deano on February 12, 2013, 01:13:02 PM
Tweaky,
Sorry, I've been staring at that part so long I thought everyone could read my mind :D
The lower right large radius part outline is the area of interest.  The resolution is pretty poor, sorry, but if you can see the purple (actual part) is a smooth curve,
the tool path (white) is irregular.  I haven't cut material yet, just did a flyover run and noticed the extra moves, then looked closer at the tool path display to see the anomaly.
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Tweakie.CNC on February 13, 2013, 01:38:26 AM
Hi Deano,

I understand now.  ;)
What you are seeing is just the tool-path display based on the available screen resolution.

In practice the machine will follow a much smoother path when your code is run.

Tweakie.
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Deano on February 14, 2013, 09:00:50 PM
Thanks for the reply, Tweakie
I just ran the gcode again on the router, did a "z axis up" flyover to verify the tool path, and still get the wierd extra moves from about line 1220 to 1300.
Also checked the Mach3 version: R3.042.040
Thanks.
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 14, 2013, 11:21:11 PM
iF you are talking about the squigglies at the lower RH corner(aboutline1220)  that appears to be a glitch in MACH3's comp code it appears the most with G3 code.

(;-) TP
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Deano on February 15, 2013, 08:40:29 AM
Thanks, BR549,
So, it's not Me?  ;D
Is there a fix for that? does the latest rev. of Mach3 overcome that? I'll try that this afternoon for kicks.
I suppose if nothing else, I could skip over that section and run the cutter the other way w/ G2 arcs.  But why does it only do it on this part, this section of the outline and no others ( out of about a dozen similar part outlines)? I guess I just got lucky, eh?

On the other hand, there's a beautiful sunrise over the frozen lake this morning, life is good.  8)
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 15, 2013, 10:03:13 AM
I tried your code 7 ways to Sunday on the latest Version(;-)  Changed the leadin/ outs no luck. There is no ryhm or reason with the tool comp glitchs.

NOW I have seen a total rewrite of new code work just fine. Sometimes editors LEAVE things in the file that we do not see.

Just a thought, (;-) TP
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 15, 2013, 10:42:29 AM
I just reCamed your DXF and it  works fine with the outer profile running as Convential cutting (CCW) Tool comp behaves itself. Tired it as you had it(CW) and it still failed

Just a thought, (;-) TP

Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Tweakie.CNC on February 16, 2013, 03:58:41 AM
Hi Guys,

I am sorry to be an absolute pain but obviously I am missing something here.  ???

I ran the posted ‘fender jaguar.txt’ file last week and could not see any problems – could you please enlighten me on just what the problem is ?

Tweakie.   
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 16, 2013, 09:14:08 AM
Hiya Tweakie, you must not have tool  #4 set in your tool table. He is using tool comp. You should be seeing the OFFSET toolpath as well.
Set tool#4 to .125" diam.

(;-)TP









Title: Re: Mach3 adding extra loops in a string of arcs
Post by: stirling on February 16, 2013, 12:17:25 PM
just for the hell of it try cam'ing this dxf and see what occurs.

Ian
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Deano on February 16, 2013, 12:40:10 PM
Thanks, BR549, I tried loading the latest rev of Mach 3, and ran the part (cutting air). It seemed to be fine, then I noticed I hadn't defined the tool 4 dia. After setting that to .125 dia. it was back to the same problem.
Tweakie, I attached a better screen shot, deleted most of the code so the portion of interest is larger so you can see the extra moves.  Looks like Mach is thinking each arc segment needs a lead-in move.  But why only these few segments and not the rest of the part outline?
Before the original post I tried several times re-drawing the arcs slightly different and re-posting the code. no change.
Will a Fanuc post processor work better? maybe I'll try that after the grandkids go home today.
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 16, 2013, 12:47:06 PM
HIYA IAN , Tried that as well IF you cut the outside profile CCW (Climb)it works (mostly G2's) If you cut it CW(Conv) (mostly G3's) it fails.

even tried moving the Leadins around and doing leadin/out on each section (as it should be done) same thing.

There be GLITCHES  in TC (;-) 

(;-) TP
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: stirling on February 16, 2013, 01:02:14 PM
Terry - phew! - I thought I'd turned invisible for a minute there!!!

Did you try the .dxf I posted?

Ian
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 16, 2013, 04:22:31 PM
HIYA Ian, Yes I did. As draw it will not cam correctly. The outer contour leadin/out lines overlap the contour lines The cam does not know what you were intending to do. I fixed the leadin/outs BUT it still will not cut correctly as a Climb milling. Turn the direction around to Conv milling and it profiles correctly every time.

I even tried taking OUT the drawn leadin/outs and let the CAM apply them, same problem.

Here is an example of the Glitchs in the offsetting AND "this" is as good as it has been, and can be a lot worse.

(;-) TP
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Tweakie.CNC on February 17, 2013, 04:11:11 AM
Hi Guys,

Thanks for taking the time to explain the problem to a dumbo – finally I understand (or at least I think I do).

I fully appreciate that this is not the answer to the problem but for me the solution would be to CAM the tool radius offset profiles and leads (the downside is the cost of the CAD/CAM software, if you don’t already have it).

Tweakie.

Title: Re: Mach3 adding extra loops in a string of arcs
Post by: RICH on February 17, 2013, 05:46:13 AM
Hey Tweakie,
Don't feel bad as i had the same problem when monitoring this thread.
Also agree that using a low cost CAM program solves the issue for doing the work but dosen't address the quirk in Mach.

RICH
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 17, 2013, 10:56:54 AM
IAN, overlaped the contour line was NOT the correct explantion. THe lines CROSSED over the contour line and stopped on the far side of the line. The Cam saw it as a seperate entity not as a leadin/out
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 17, 2013, 11:03:36 AM
HIYA Tweaky, In the general scheme of things I agree that most can use the Standard CAM offsetting. BUT in the Part machining world where precision is required then TOOL COMP is preferred. You need to be able to adjust the TC to make the part to precise dimensions.

With Cam comped code you have no choice on precision you get what you get and there is no way to adjust the final dimension OTHER than RECAMing the part again and possibly having to cut a new part .

In the ART world "Cam" is king(;-)

Just a thought, (;-) TP

Title: Re: Mach3 adding extra loops in a string of arcs
Post by: stirling on February 17, 2013, 11:22:13 AM
Hi Terry - the reason for my leadin/out cockup was I rebuilt the original curve simply by doing a 1 thou outside offset curve of it in Rhino but like a muppet I forgot to move those (manual) leadins/outs by a thou.  :-[

Had a bit more of a play and of course you're quite right that Mach has an issue with cutter comp and climb milling. However there were a few things I noticed about the dxf. Mainly that there ARE gaps between some segments - small - but there none the less. Also some curves didn't meet other curves or line segments at tangents (not that they should have to) - again very slight deviations but there. Anyway I cleaned up the dxf to address these two "issues" (just the scratch plate profile) and now Mach seems much happier - see enclosed .tap.

That said - as you say - there IS an issue with Mach but maybe this might go some way to explaining why the OP had some drawings that worked and this one that didn't.

Ian
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 17, 2013, 01:18:03 PM
HIYA Ian , Yes I saw the glitches in the DXF but the cam stiched it back together as a contour.

Your code STILL produced glitches in the offset toolpath.(;-)  Notice that the TC path crosses back over the original path to the INSIDE and then crosses back over again to get to the outside.

I can change the code all around and get different reactions from the TC but never does it make it perfect on THIS example. Another different DXF example MAY run just fine.


(;-) TP
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: stirling on February 17, 2013, 01:43:50 PM
oops - missed that one. :o

Don't get me wrong Terry - I'm not disputing anything you've said - I fully eccept that Mach has issues and how. (triggers for example ::)). After the OP said "some" worked "some" didn't all I was doing was just trying to see why that was.

Cheers

Ian
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: BR549 on February 17, 2013, 01:55:11 PM
Ian, not a problem I understand(;-)  I have tried for hours now trying to see "IF" I could get it to run correctly(taken as a challenge). The easy way was to reverse the direction of cut(;-)

There were also several other FINE detailed glitches I did not show(;-)

I am still trying different approaches to that contour but I don't expect any other outcome. But being hard headed I carry on testing and throwing rocks at it.(;-)

About like trying to get TC to work with SUB programing a LOST cause.

(;-) TP



Title: Re: Mach3 adding extra loops in a string of arcs
Post by: Deano on March 24, 2013, 08:54:13 AM
Thanks for all the intense effort to attempt to get to the bottom of my original problem.  I've been running a number of new pickguard files using Conv. cutting path with no problems.
It's great to know there are so many experienced operators willing to help.
Terry, I can't help calling you "Rainman"  ;D.  Thanks again.
Title: Re: Mach3 adding extra loops in a string of arcs
Post by: brcarls on April 03, 2013, 10:15:54 AM
I am not sure if this is your problem, but I ran into an issue where I would do a G41 and then position the cutter with an X,Y move at the same time (as opposed to X, then Y, and it made Mach3 flip out...   

No error code was given, and the DROs kept moving, but my mill jerked to a stop and the stepper motors howled like the table had crashed at the end of travel, but it wasn't even close to a crash.   

I changed the X,Y move to a different spot and re-ran the program and the mill did a big loop to get there (It was supposed to be a G01 move, not an arc)

I then changed it to move X then Y after the G41 and it worked correctly.   I assumed I was just breaking some rule of G-code programming since I'm new at this.

I see you did an X,Y move immediately after G41 on line N0480.