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Jogging in the Zed goes the wrong direction for a tiny amount
« on: January 03, 2013, 12:00:12 AM »
Hi,
   So I have a sherline 3 axis metric mill and their CNC driver box with 4 outputs (I'm not using the "A" output).  I grabbed the xml for the setup from the xml ftp site Mach3 has.  The X and Y motors run quite smooth both in 50% and 100% (shift key) jogging.  I can change directions without issue.  But on the Zed axis, I page down and it goes down every time, but if I try to go up after going down previously, the only way to get it to really go up is to do a quick tap of the page up key a few times.  Then it will go up on subsequent presses of the page up key.  Very strange. 

   So to debug it, I've tried a few things but they all seem intermittent.  I unplugged Z motor from the Z output and instead connected the Z motor to the the "A" output of the cnc driver box.  I updated the pins in the pin config of course, and then Z was working.  Seemed perfect so I figured my Z output of the box or PC port was bad.  But then it started doing it again.  So I tried swapping the X and Z and similar story.   

   What is very odd is the behavior when it fails.  I just can't switch from jogging Zed down to then jogging it up without the difficulty.  It goes down even when I try to go up until I tap quickly the up jog key on the keyboard a few times.  It's like its remembering that I'm going down.  Note that switching  from jogging up (after I finally get it working) to jogging down always works the very first try.

    I will try to reverse the zed direction now to see if then I have the opposite issue. 

   I looked and I don't think I have any "backlash" turned on.  But I'm quite new to mach3 so I could be wrong there? 

   So do I have a bad motor, a bad cnc box, a bad parallel port, or just a bad mach3 setup?  ANY HELP APPRECIATED! 

Justin
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #1 on: January 03, 2013, 12:43:39 AM »
Hi Justin,
  Could be your keyboard.
Assign a different key for the Z+ and see if it works.
Or, try another keyboaed if you have one handy.
Russ
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #2 on: January 03, 2013, 01:23:26 AM »
Also, are you running a licensed install ? or the Demo version ?
Pirated SW does strange things similar to this too.
Russ
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #3 on: January 03, 2013, 01:32:25 AM »
Thanks.  Good idea.  Let me try a new usb keyboard. 

One thing I did notice after playing around more.  It seems worse when I have Zed reversed.  I.e. all the way up zero, and down towards the table being negative.  That's how I want to obviously run it, but it seemed to work fine if I was running NOT reversed?  Again though, it may be just intermittent.  Its very hard to tell due to the problem seeming to come and go.

The other thing it may be related to, is a question I have.  Do I need to turn off the CNC driver box any time I'm changing the pin settings or the polarity (reversed or not reversed)?  I assume it's a good idea if not absolutely required.  And again maybe that was part of my problem?  I'll keep looking.

Even when its "working" it seems to me that the direction voltage may just not be fast enough out the printer port?  That may be consistent with the issue only being in one direction?  Could the rise voltage maybe take longer or shorter than the fall votage?  I did put the meter on the pins on the side of the cable that plugs into the cnc box, and I only saw 3.3 V high and 0.6 or lower for low.  I used pin 25 for a ground, so is my computer not putting out the required 5V possibly?  Any idea how to raise that?
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #4 on: January 03, 2013, 08:07:28 AM »
having never used a Sherline, just guessing here.
Assuming you are in Sherline Mode.
Many breakout boards accept 3.3v and are externally powered which provides 5v for the I/O, if all else is OK, this may not be a problem.
I never turn anything off to make config. changes.
The pulse polarity can cause problems if reversed, but the dir polarity sould not make much difference.
Lots of Sherlin folks here that will most likely help you out.
Greetings,
Russ
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #5 on: January 03, 2013, 08:08:53 AM »
Also, are you running a licensed install ? or the Demo version ?
Pirated SW does strange things similar to this too.
Russ
Hi,
   I'm running the demo.  I've only been up and running for a few days now.  I plan on buying the software but was just checking out the system.  I had linux CNC loaded on ubuntu on this machine but the learning curve was a bit steep on their instructions.  My friends at the real machine shop I know use mach3 and told me about the videos and I'm very very happy now learning on this program.  Can't wait to watch more vids.  :-)
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #6 on: January 03, 2013, 09:46:05 AM »
having never used a Sherline, just guessing here.
Assuming you are in Sherline Mode.
Many breakout boards accept 3.3v and are externally powered which provides 5v for the I/O, if all else is OK, this may not be a problem.
I never turn anything off to make config. changes.
The pulse polarity can cause problems if reversed, but the dir polarity sould not make much difference.
Lots of Sherlin folks here that will most likely help you out.
Greetings,
Russ
Hi,
   So here is the spec:  http://www.sherline.com/8760pg.htm

   It doesn't appear as if my 3.3V is a problem.  I'll have to go back and make sure my low voltage was lower than 0.5V which I think it probably was.  Also, the thing is that ONLY the Zed direction is failing, and even then, when it fails it's not a massive failure.  Its just this tiny period of time where it goes in the wrong direction.  I will hook up my logic analyzer tonight and get a graph output of the PC controls for a good (X and/or Y) and bad (Zed) case.  That should completely rule out mach3/configuration/PC port issue.  Then it would be just the CNC box which could be bad.  I need to talk with Sherline if that's the case since I don't want to really touch anything in that box without their input first.
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #7 on: January 04, 2013, 01:16:32 AM »
Ok, so I was about to connect up the logic analyzer tonight and debug, but then when I powered up, it worked perfectly.  Then after maybe 20 min it started failing again.  I think that's the smoking gun.  Seems like a bad solder or something else heating up that is causing ohmic connection.  I let it cool, and again it worked perfectly.  No changes to config of mach3, no changes to wiring or connection changes to motors. 

Time to talk with sherline about the CNC driver box.
Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #8 on: January 26, 2013, 04:10:43 PM »
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

Re: Jogging in the Zed goes the wrong direction for a tiny amount
« Reply #9 on: January 26, 2013, 10:28:44 PM »
Eradicatore

I had the same problem except in my case it was mostly the Z axis.....it would mainly go down even when receiving a signal to go raise the spindle.

X and Y would behave erratically too but not as often.

Sherline replaced the controller twice but no improvement at my end. We tried everything you could think of and in the end, what did help was this  http://www.cnc4pc.com/Store/osc/product_info.php?products_id=203 .

An alternative would be to find an old PC XP computer. I found out about that after I got the buffer.