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Author Topic: Gantry Router  (Read 3512 times)

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Gantry Router
« on: June 11, 2013, 04:26:28 PM »
Hi All,
          I have recently built a CNC router with the idea being that if could build a small router table, why couldnt i build a 8' X 4' plasma table (thats what i really want!)
So, i got to the point where all mechanics were done and its all wired in, excitedley purchased a mach3 lisence...............and for the last 3 weeks have been tearing my hair out (on and off). If anyone would care to read on, and offer any advise i would greatly appreciate it.

Machine: 3 axis gantry type router as below, if the pic uploads.

Mechanics: 16mm linear bearings, 20 x 8 trapaziodal leadscrews with brass nuts, Nema 23 (3.1Nm) motors

Hardware: http://www.ebay.co.uk/itm/261190737455?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D261190737455%26_rdc%3D1

48v power supply

The machine works as a whole, so i think i have correctly set the ports and pins etc.......all axis' move on jog and running code.
Drivers are set to: step angle 0.025 , pulse/rev 1600 and on half current
All settings in mach are the same with all axis'. steps per 200, vel 2000, accel 170

Problem: The X axis does not measure up, mach will read 207mm to a physical 200mm its actually travelled, and it seems to grow 7mm (ish) every 100mm it travels
on numerous tests just running the x, with the aid of a digital height gauge on its side, every result (measurement) comes out different, this confused me because the other 2 axis' work great and to quite a tight tolerence.

I have checked all mechanics, they are free moving , tight and inline

I swapped the Z mototr for the X , leaving it so that when i jogged the Z in mach it moved the X on machine, it measured up! i thought it was the motor that had gone, so i bought a new and fitted it, but got the same problem, i then replaced the driver, same problem. I then wired in a motor on the Y axis to the X driver, and told mach accordingly what was going on so the machine would still operate, low and behold the Y motor started playing up!

I know the mechanics are good, its not the motor, its not the driver, its not the parallel port cable.So ive boiled it down to either the breakout board, my computer (which is dedicated to the machine)or its something in mach i havnt done correctly, i just find it very strange that everything is set up the same with good results, yet something is is very badly wrong running through the X path somewhere!

Sorry to bore you all........i really hope you can help, its so frustrating when your so close, cheers

Offline ger21

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Re: Gantry Router
« Reply #1 on: June 11, 2013, 05:30:46 PM »
Quote
I swapped the Z mototr for the X , leaving it so that when i jogged the Z in mach it moved the X on machine, it measured up! i thought it was the motor that had gone, so i bought a new and fitted it, but got the same problem, i then replaced the driver, same problem. I then wired in a motor on the Y axis to the X driver, and told mach accordingly what was going on so the machine would still operate, low and behold the Y motor started playing up!

Sure sounds like the X axis drive.
Gerry

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JointCAM Dovetail and Box Joint software
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Re: Gantry Router
« Reply #2 on: June 12, 2013, 01:44:20 PM »
It cant be the driver for the x axis, because i replaced it with another driver and same result, i even put what was the x driver onto the z axis and it worked ok. Is there any way to make the B axis on the breakout board run as the X?? If i could do that and it worked, it would prove its the x on the breakout. Or is there another way to test the breakout board? If its not that, it must be my computer, everything else checks out.

Thanks for your time and help.
Re: Gantry Router
« Reply #3 on: June 13, 2013, 07:44:12 AM »
What are you running for drives and a breakout board?

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline Chaoticone

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Re: Gantry Router
« Reply #4 on: June 13, 2013, 08:16:22 AM »
Have you tried changing you step signals to active low?

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Gantry Router
« Reply #5 on: June 13, 2013, 08:35:47 AM »
Hi,
      I have MA860H drivers, but don't know what breakout board it is, there is a link in my first post to the eBay auction I purchased the kit from.
   Where do I change my step signals to low, in ports and pins? Should I just change the offending axis to low, or all of them? I will try it out when I get back from work. Thanks for your help.

Offline Chaoticone

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Re: Gantry Router
« Reply #6 on: June 13, 2013, 09:01:57 AM »
Quote
Where do I change my step signals to low, in ports and pins? Should I just change the offending axis to low, or all of them?

Yup, motor outputs.  You could change it on just the one for a test but I think they should all be set to active low for those drives.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline stirling

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Re: Gantry Router
« Reply #7 on: June 13, 2013, 11:13:32 AM »
I agree with Brett that they should be active low (though the DS isn't exactly clear).

However I'd guess you have BOB issues. Try switching (say) X and Y driver connections at the BOB and see what happens. One of the reasons I dislike BOBs is that they seem to think it's a good idea to have optos on everything. Optos on the BOB driving optos on the driver is (IMHO) a recipe for unreliability. I also love this bullet point on the fleabay add re: the BOB - "Upgraded circuit, work more peacefully and steady than the previous version" Hmmmmm.

Ian
Re: Gantry Router
« Reply #8 on: June 13, 2013, 03:46:39 PM »
Ian/Brett,
              I have changed all step signals to active low, and......it seems to have worked. I set up the height gauge on its side again and did several runs on the x axis. Over 200mm in mach, the gauge read a constant 199.85, although its not on the mark i can play about with the steps per to get that right, but i am relieved and very thankful to you both, this was really getting to me! Can i ask why the stepper drivers i have need to run on active low? also,, what is "optos"?
I will play about with it more at weekend and let you know how its performing, maybe with some pics if i can get to grips with the upload of them!

William

Offline stirling

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Re: Gantry Router
« Reply #9 on: June 14, 2013, 02:35:45 AM »
Good you're making progress William.

Can i ask why the stepper drivers i have need to run on active low?

see section 10. "Sequence Chart of Control Signals" in your driver data sheet here.

also,, what is "optos"?
See Optocouplers

Ian