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Messages - Eradicatore

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1
General Mach Discussion / Re: Arcs and cutter comp
« on: March 31, 2013, 01:07:38 AM »
OK, My 1st program. 

In regards to making arcs, is I and J incremental or absolute in Mach3?  What if I am in G90 mode? 

I plan on cutting a path by programming the points of the outline and using both G41 and G42.  You see, I have a .375" cutter and I am going to for the first pass, G41 and use a P variable of .375 ( .750" diameter cutter), get to the end of the pass and then switch to G42 w/ a P of .3125, go back up that path but in reverse.  I want to go back and forth getting closer each time to the final dimension until I use a final P of .1854 as this whole operation has been a roughing cut in 4140 PH.  I will not be making any tool changes so I won't be using D variables.  From what I understand, I don't need any lead in moves when hitting the end of the path and changing between G41 and G42.  My question is this, will I need to include lead in moves because I am changing my P values?

Hi Mountainman,
   Too funny, I just noticed your post right after I posted a very similar question and have been beating my head trying to understand G02 and G42 for a few hours.  I think we may have similar questions, but also you seem to have a question that I have just learned the answer to I think.

   Go to the "Config" pull down menu and select "General Config...".  There in the middle you'll see "IJ mode" and you can select relative or absolute.

   For some reason this is "absolute" by default I think.  And it would seem that doing G02's with relative IJ's is way easier to code by hand.

   Anyway, I got that working fine, but see my other questions here:

http://www.machsupport.com/forum/index.php/topic,24178.0.html

2
Yup, I totally agree.  I ran about a 30 minute cut and observed the whole time to make sure nothing funny happened.  I will update maybe in a week or two if there are any issues ever again.  Thanks again!

Justin

Well, just a quick update.  Been busy so haven't used the mill as much as I would have liked.  But I can now say that I've used it enough to be 100% sure that this buffer was my whole problem.  Thanks again MaNo!  You really were a life saver on this one!!

3
Hi,
   I'm learning to write Gcode by hand.  I have a project where I want to cut 7 full circle arcs out, and I thought using G42 to account for the cutter diameter would be pretty straight forward.  My code does show in the tool path the nice purple lines for the circles, but then it also shows a white spiral line which when I run the program seems to be the true cutter motion.  So I'm totally confused why it won't just follow out the purple arc lines.  Where is the spiral coming from?? 

   Here is my program.  Note that I've tried both settings for IJ being relative or absolute.  Doesn't change the behavior at all.  Let me know if you need me to include a screen shot of the sprials.  I've also tried putting G42 on the same line as G02.  Didn't help either.  When I did that, the arc actually didn't cut out at ALL!  It would plunge to start the cut, and then just raise again and move to the next hole location.  I did learn that the spiral depends on where I put the G42 line in sequence of the other lines. 

Code: [Select]
% 6 LEDS and reset button
G40
G01 F20 S5000
M03
G21
(-----hole1------)
G00 Z5.0
G00 X25.0
G00 X25.0 Y19.0
G42 P3.175
G01 Z-5.0 F80
G02 X25.0 Y19.0 I25.0 J15.0
G40
(-----hole2------)
G00 Z5.0
G42 P3.175
G00 X40.0 Y34.0
G01 Z-5.0 F80
G02 X40.0 Y34.0 I40.0 J30.0
G40
(-----hole3------)
G00 Z5.0
G00 X55.0 Y49.0
G01 Z-5.0 F80
G02 X55.0 Y49.0 I55.0 J45.0
G40
(-----hole4------)
G00 Z5.0
G00 X70.0 Y49.0
G01 Z-5.0 F80
G02 X70.0 Y49.0 I70.0 J45.0
G40
(-----hole2------)
G00 Z5.0
G00 X85.0 Y34.0
G01 Z-5.0 F80
G02 X85.0 Y34.0 I85.0 J30.0
G40
(-----hole1------)
G00 Z5.0
G00 X100.0 Y19.0
G01 Z-5.0 F80
G02 X100.0 Y19.0 I100.0 J15.0
G40
(-----reset hole------)
G00 Z5.0
G00 X62.5 Y21.625
G01 Z-5.0 F80
G02 X62.5 Y21.625 I62.5 J15.0
G40
G00 Z5.0
G00 X0.0 Y0.0

4
Yup, I totally agree.  I ran about a 30 minute cut and observed the whole time to make sure nothing funny happened.  I will update maybe in a week or two if there are any issues ever again.  Thanks again!

Justin

5
Excellent!!!!  I'm doing a cut now that never worked and now it works perfect.  Thanks MaNo for the 20 dollar patch to my problem!!!  

Sherline was nice about trying to look into it, but they now I think need to make sure to warn all future customers of this potentially very dangerous issue.  Especially since it sounds like the newer  your computer is the more likely it will fail with their CNC driver box alone.

I owe you a pint MaNo! Cheers!

6
Ok, finally got 2 db25 gender benders from amazon prime.  You wouldn't believe how hard it is (around me anyway) to find a store that sells db25 gender benders!!  Its now all hooked up and working perfectly.  I do however need to test it for a few hours I think to make sure it doesn't fail again once it gets warm.  fingers crossed.  So far so good.

7
Doh!  I got the buffer and driver box back today, went to hook it up, and realized I need two gender benders!  :(  I should have checked when I ordered it.  Now I have to wait another day to test.  the suspense is killing me!  :)

8
Thanks again MaNo!  I ordered the $20 buffer and my sherline box is on it's way back too.  I hope by the end of this week I can confirm your analysis and put this to bed.  I will be so happy when I can finally get to trusting my cut and making some real stuff.  I'm totally new to CNC, so I'm having fun learning along with all this debugging.

So just out of curiousity, did all 4 of your chips have the white dot on them?  Or just the X and Y PIC chips?

Cheers
Justin

9
MaNo,
  Thanks so much for the advice!  I was really hoping to find someone with the same issue possibly.  It sounds like we have the exact same issue.  You mention yours is mostly Z, and so is mine.  Did you try using A axis to control Z instead of Z?  Did that show the same issues?  Did your issue show up right away or only after the box warmed up?  Also, that's very concerning that you saw X and Y issues but just rarely.  Makes me think I could see them too possibly if I use it a lot more. 

   So this buffer you mention sounds like an excellent way to ensure that the signal out of the parallel port is the proper levels.  Are you suggesting that an older PC may also have a better on board parallel port that isn't "low voltage"?  Do you know if getting a PCI parallel port may also do the trick?  I guess for 20 bucks, this buffer you're pointing out seems to be about the same price as a pci parallel port card anyway, and be a good safey precaution overall.  I think I'll give it a go. 

   One question.  Could you look in your driver box and do you see the same "two white, two black" PIC chip situation?  Not sure how many versions of that box they have out there too though I guess.  Mine is very recently purchased (Oct 2012). 

   

10
Just a courtesy update.  I've sent my box back to Sherline and they have been checking it out on EMC2.  They found one "bad" cable, but it was Y and not Z or A which are my issue.  Just to recap my issue and what testing I did:

The issue: When jogging Zed down, it will work 100% fine.  When CHANGING from down to jog up (not rapid jog btw) it fails to change direction until you try it a few times.  Eventually it will change to going up, and then every jog up from that point (until I ever jog down again) is 100% fine.  So my whole issue is just changing from down to up in the Zed direction.  This failure happens not just with jogging by the way.  It fails during a full run of a cut too, causing my Zed to be actually lower than mach3 thinks based on DRO's.  DANGEROUS/VERY BAD!!!

The testing I've tried:
  • Swap out the Zed cable of the CNC driver box to the A cable.  I of course changed the pin out settings also in mach3 so A parallel port pins now controlled Zed.  Both A and Zed fail the same way.  That rules out the parallel port signal for Zed alone being bad.  A and Zed could both be bad but seems unlikely.
  • Tried swaping Zed and X.  The failure described above follows the Zed cable output of the CNC driver Box.  So that rules out the motor being bad.
  • Verified my settings in motor tuning (that I got from the mach3 FTP site with xml setups for different machines) was the same for X,Y, and Zed
  • Oddly if you let the CNC box sit off for a while, the issue goes away until it's allowed to warm up for 15-20 minutes. 

Sherline has tested my box, but I've not yet been able to ensure they were really testing for the right failure.  I'm still in talks now live rather than email to try to make a break through.  They don't have a computer tech yet, or at least one that I've been able to talk to.  Which is very interesting because of one more piece of information I haven't mentioned yet.

See the photo below.  When looking at the circuit board inside the box for cold solder joints or anything bad, I noticed a strange thing.  X and Y have PIC16F627 chips with a white dot on them.  Zed and A have the same chip (in a socket btw) that has NO WHITE DOT!.  The person I talked to so far at sherline didn't know why, but did confirm that the chips are programmed with different firmware!  So the mystery is why would two of the linear axis' be using one firmware, and one other linear axis (along with the rotational A axis) have different firmware?  And does this firmware mean I need different motor tuning settings for Zed compared with X and Y?  Recall that Zed works mostly.  Just has issues with changing direction.  So is there a strange timing issue with just the Zed and A firmware?

Does anyone know of a good test with a logic analyzer to do on the direction change signal versus the square wave pulse train for stepping?  What is the critical separation in time between those two different signals?  I have a logic analyzer so I could monitor the parallel port.  But I'm more thinking I need to monitor whats coming out of the CNC box.

Justin


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