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my first project
« on: May 08, 2009, 01:38:45 AM »
Hi everyone-

My name is Steve, and I am in the process of building a plasma table.  I have been working on this project on and off for some time now.  I finally have the mechanical and most of the electronics installed and wired up.  I have started to configure Mach 3, and that is where some of my problems are starting.  So I am hoping that someone can get me pointed in the right direction.


Here is what I have so far.

My cutting area of the table is 6 x 12 foot, I also have 2 feet of extra running room at each end.   This allows the gantry to travel the entire area of the cutting space.
-   I am using 2  - 1125 in oz servos with 1250 US Digital encoders for the X
-   I am using 1 880 in oz servo with 1250 US Digital encoders for the Y
-   I am using 1 600 in oz servo with 1250 US Digital encoders for the  z with a ballscrew
-   I am using a rack and pinion for the movement
-   I am using 5 to 1 Thopmson DuraTrue planetary gearboxes
-   I am using VSD-E servo drives from Granite devices
-   I am using linear rails and bearings
-   I am using the C23 breakout board
-   I am using the Smooth Stepper motion controller
-   and I am using a Modbus I/O board

That is a list of most of the stuff I have installed so far. 

I tuned the VSD-E servo drive according to the manufacturer, this took awhile (long Story), now when I try to control the servos with Mach, the servos will start to spin, then speed up out of control.  This is my biggest problem.  I am not sure if it is a Mach 3 problem, a servo drive problem, or something else.  If I can not figure this out, I see a major CRASH in my future.

My next issue is with the E-stop.  I have an E-stop located at each corner of my machine.  When the button is pressed, nothing happens.  The servos keep running.  The BOB shows that it received the e-stop signal, but that is all.  So is this a BOB problem, a Smooth Stepper problem, or a servo drive problem?

The last question for now is can I or should I connect my over travel limit switches directly to my BOB or can I connect them to the Modbus I/O board?   My over travel switches are one of the last items I need to wire.

I will try to post some pictures in the next few days.

thanks for the help, and let me know if you need more information.


Steve

Offline Jeff_Birt

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Re: my first project
« Reply #1 on: May 08, 2009, 10:38:52 AM »
Quote
the servos will start to spin, then speed up out of control.


Sounds like the servo drives are not seeing the encoders...If you can control the servos with the drive mfg software then it could be a configuration problem with Mach/SS.


Quote
I have an E-stop located at each corner of my machine.  When the button is pressed, nothing happens.


Your E-stop should remove power from the drives by breaking the AC connection to the drive power supply. The E-Stop input into the BOB and mach is just to let them know what is going on. You cannot depend on your controller to stop the drives.


Quote
The last question for now is can I or should I connect my over travel limit switches directly to my BOB or can I connect them to the Modbus I/O board?

Limit switches should go through the BOB and should wind up at the VSD-E too. Never, ever, ever, ever try to run a motion control input or E-Stop through modbus.
Happy machining , Jeff Birt
 
Re: my first project
« Reply #2 on: May 08, 2009, 01:09:28 PM »
Jeff-

Thanks for the help. 


I can use the software from Granite Devices to monitor the encoder values when I am setting the parameters of the servo drive.  Is it possible that I am loosing the signal from the encoders?   I am using differential encoders, and shielded wire.

I will wire in relays for the e-stops.

I was hoping that I could use the Modbus for over travel limit switches, because wiring would be easier, but I will run them to the BOB.


Thanks again.



Steve
Re: my first project
« Reply #3 on: May 29, 2009, 12:43:13 PM »
OK-  The relays are installed.  I have 3 relays, 1 for each axis.

Everything for the e-stops is now working.

Now for the next problem.  I can not get the two servo motors for the x axis to spin at the same rate.

This is what I have tried so far--

- the settings in the VSD-e servo drivers are set the same
-I have Mach 3 set to slave X axis and A axis together
-I have the motor tuning portion for mach 3 the same for both x and a axis

Both servos are spinning the correct direction.


Any ideas if this is a servo driver setting  problem, a Mach 3 motor tuning problem, or something else????


Thanks for the help


Steve