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Random Loss of Position
« on: December 04, 2010, 02:26:29 PM »
So,  First of all,  Hi everyone!

Green Horn Here.

 I just finished a retrofit of a Anilam knee mill.

 I used the  4 axix AC servo Kit from Dmm Technologies.  

Peak 7.2Nm(1015 OZ-In) high torque AC servo motor, 3 Axis CNC kit for MACH3

Here's some specs:
- 3 x Peak 7.2Nm(1015 Oz-In), rated 2.9Nm(408 Oz-In), Peak power 900W, AC servo motors
- 3 x Dyn2-H AC servo drives for very smooth,quiet,very high efficient driving
- 1 x DMB4250-8B breakout board, fully buffered Opto-isolated I/O, isolated PWM analog output
for spindle speed control,and charge pump. Hardware generated X secondary X' for CNC Gantry with
jump selectable motor turning direction.
- 1 x 6ft DB25 parallel port cable
- 1 x 6ft USB cable
- 2 x 120 or 220Vac input, 350w,+48Vdc, 7.3A output DC power supply
- 3 x 1ft cables between breakout board and drives
- 3 x 10ft differential signal encoder extension cable
- 3 x inductive, non contact , LED indicated proximity Home/Limit Switches
- 1 x Emergency STOP Switch
- Necessary Cables, DMM software for tune up servo

http://www.dmm-tech.com/Products.html

I have everything working good....Except one glitch... Randomly on long runs when the x axis is traversing it will stall or freeze for a 1/4 second or so, suddenly and abruptly. When it continues its motion  it causes the axis to loose its position.  I've checked the PC to make sure nothing is running in the back ground.  I've changed the driver.  I've checked for loose wires.  I don't know where to go from here so any help will greatly be appreciated.

Thanks
Steve
Re: Random Loss of Position
« Reply #1 on: December 05, 2010, 12:09:14 PM »
Check your sensor, I just retrofitted a machine with these and had a bad one.
If they are NPN NO type, you should have 12v open (24V supply) and <1volt closed.
The voltage should not wander,(my bad one wandered between 2v - 4v open)
please not that the light on mine worked right, but I had random events.
You can get these on Ebay for about $8, direct from China.
Re: Random Loss of Position
« Reply #2 on: December 05, 2010, 12:18:03 PM »
Check your sensor, I just retrofitted a machine with these and had a bad one.
If they are NPN NO type, you should have 12v open (24V supply) and <1volt closed.
The voltage should not wander,(my bad one wandered between 2v - 4v open)
please not that the light on mine worked right, but I had random events.
You can get these on Ebay for about $8, direct from China.
I,m not quite sure what you mean by sensor. 
Re: Random Loss of Position
« Reply #3 on: December 05, 2010, 01:24:17 PM »
The Blue proximity sensor, check between the blue and black wires with a multimeter set on dc volts
what is your power supply voltage on the sensors?

Offline BR549

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Re: Random Loss of Position
« Reply #4 on: December 05, 2010, 01:33:16 PM »
iF it were a limit switch activating it would stop mach as a limit trip. Check the mach driver test and look for something causing a pause in mach.

Just a thought(;-) TP
Re: Random Loss of Position
« Reply #5 on: December 05, 2010, 04:06:16 PM »
BR549 is probably right, my sensors are wired into the amp. I do not know how fast Mach3 would trip on
one of them. These sensors do not go out often, and I would not have suggested it except that I seen
your sensors are the same as the ones as I put on my last machine. The test I suggested will rule them out
at least. I still have have the bad one, I think I will wire it into mach just to see what will happen.
Re: Random Loss of Position
« Reply #6 on: December 05, 2010, 08:23:37 PM »

Well,

I disconnected the limit switch and it ran flawlessly all day. 

When I set up the machine I didn't use the blue limit switch s in my set up since my machine was already set up with mechanical switches.    I did notice when I disconected the wires at the breakout board one seem like it might have been loose.  I should have been a little more careful because that might have been the culprit.

Anyway
Thanks Everyone!
Re: Random Loss of Position
« Reply #7 on: December 06, 2010, 02:12:55 PM »
iF it were a limit switch activating it would stop mach as a limit trip. Check the mach driver test and look for something causing a pause in mach.

Just a thought(;-) TP

Well now it pauses in The Y axis as well.  I ran the driver test.  The first time I ran it it said pulse too slow in Red. is that normal?  Is there some where where I can read or find information on how to use the driver test?  I'm really not even sure of what the driver test is doing.

Steve



Offline Hood

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Re: Random Loss of Position
« Reply #8 on: December 06, 2010, 02:21:18 PM »
You need to male sure Mach is shut down when you run the driver test or you will not get a true reading. The important thing in the driver test is that the graph looks smooth with no big spikes.
Hood
Re: Random Loss of Position
« Reply #9 on: December 06, 2010, 02:24:54 PM »
So when it counts down to "Mach 3 taking over"  and you see a initial spike then clean after a second or two.  is that ok?