Servo drive problems

[Tomnewry]

Hi guys I dont know if anyone here can help me but here goes.. The problem I am having is for some reason when i switch on my machine and run the software program the drives just go nuts running up and down the different axis like it's got a mind of its own. It dosent do it all the time only sometimes but more times than not, it runs on three servo drives with encoders on the top of the drives. I have used the machine lots of time with no problems but it's doing my head in I have checked for looses wires but cant find any.
Thanks in advance.

[AdCNC]

Well if all 3 axis are doing it then i will be a problem with whats supplying the signal. so chances are its your board.. what board are you running btw also what software?

[Tomnewry]

Hi the software is amtechs gnc software as for the board im not sure, when i open the controller box there are three mini maestro drive boards and the controller is connected by two scsi cables.
By the way sorry for the delay in replying.
Also i have replaced the wiring from the encoders and its still doing it.
Thanks

[Swarfing]

You talk of scsi cables, is this what connects you controller to the PC? or are you using conventional printer cable to the parallel port? if you are using the later something else may be sharing the interrupt for that port.

[Tomnewry]

Hi the connections are two 37 way scsi connectors which have their own i/O cards in the computer the machine runs fine sometimes and others just goes nuts im thinking of changing the whole controll box if i cant get it sorted, is their any way of checking the drives and encoders before making any drastic decisions.
Thanks

[Tomnewry]

Also the cards are from amtechltd.co.uk hope this helps.

[Gary]

Also the cards are from amtechltd.co.uk hope this helps.
You would be best to contact Amtech.
I dont think the drivers are the problem.

[Tomnewry]

Hi Gary thanks for your reply but i have contacted amtech and they want me to sent them the cards from the computer but its going to cost a lot of money so thats not really an option thats why im trying to see if anyone might know the problem. Is there a way i can run the servo drives from a breakout board and run the cnc from mach 3 or simlair program?
Thanks

[Gary]

Hi Gary thanks for your reply but i have contacted amtech and they want me to sent them the cards from the computer but its going to cost a lot of money so thats not really an option thats why im trying to see if anyone might know the problem. Is there a way i can run the servo drives from a breakout board and run the cnc from mach 3 or simlair program?
Thanks

The driver you have is a very old analogue DC servo driver so the control signals are +/-10V.
Mach 3 and most of the other lower cost CNC controllers send out a step and direction.
So the answer is no.
If you use the machine for production and it being down cost you money, you would be best to just send the boards to Amtech.
I have known Stuart at Amtech for over 15 years and while he will charge you for any work, he is good at what he does and should be able to get you running again.

[Tomnewry]

Hi gary thanks for replying, the machine is only being used for hobby stuff and im in no panic for fixing it i just dont want to start sending away cards to be told the problem is with the encoders or someting else. Hope this makes sense im try to exhaust the less costly options first.
Thanks again

[Jonathan]

Is there a way i can run the servo drives from a breakout board and run the cnc from mach 3 or simlair program?

Plenty of people run LinuxCNC (which is free) with +/-10V analogue signals. You'd probably need to buy a card to enable the computer to output those signals, but it's certainly possible and so long as you do the conversion yourself I expect it would work out cheaper than paying someone to fix it.

Example:
LinuxCNC Support Forum :: Topic: Help please !!! Servo configuration with stepconf. (1/6) (http://www.linuxcnc.org/index.php/english/forum/16-stepconf-wizard/19642-help-please--servo-configuration-with-stepconf#19645)

[Tomnewry]

Hi Johnathon thanks for the reply, i intend to do all the work myself do you have a card in mind i was looking at a card called PMDX 126 i think it will run servos what do you think?
Cheers Tom

[m_c]

To go linuxCNC, you'd need something like the Mesa 5I20 ($199) and the 7I33 ($69) daughterboard, plus you'd proably want a 7I37 ($69) to get 24V tolerant inputs/outputs.
The only reason I know about the Mesa stuff is I did consider LinuxCNC, but other than some very basic details about cards that are compatible, I couldn't find any great details about how to set them up or what scripts would be needed to get them to work.

In the end I opted for a Dynomotion Kflop and Kanalog, as the support for both Mach and Kflop is far better.
There are other motion controllers that will work with +/-10V drives. Galil (pretty highend stuff with pricing accordingly), and CS-Lab (relatively new, but their stuff looks good although pricing is top end hobby/lowed end industrial) are two that spring to mind.
To use servos with Mach, you need something to close the loop outside the computer. As has been said, Mach only ouputs step/dir and isn't capable of closing the loop. You either need to close the loop in the drive (most modern servo drives are capable of this), or the motion controller (i.e. Kflop/Galil/CS-Lab CSMIO-A).

The PMDX126 is essentially just a parallel port break out board with a few extra features. It's certainly not capable of closing the loop for servos.

[Tomnewry]

Hi Johnathon thanks for your reply ill have to have a look into this and think about it, cheers for your help.

[Tomnewry]

Hi Johnathon thanks i have been looking at the klop board is that all i would need to do away with the old boards on the computer that are currently being used.
Thanks

[m_c]

I'm going to assume it's me you're asking about the kflop, and not Jonathan?

What exactly you need depends on what other Inputs and Outputs are required.
For my mill, I've got a spreadsheet where I've listed all Inputs/Outputs I'd like, then mapped them to what's avaiable on the Kflop/Kanalog. I know I'll be pushing certain Inputs/Outpus onto MODbus, as the KFlop doesn't have enough Inputs/Outputs.

Before you make any final decisions, I'd recommend making up a list of what Inputs/Outputs you'll need, then seeing what options are suitable. If you want to PM me your email, I'll send you over the spreadsheet I've started for my mill.

I've got the KFlop/Kanalog, but I've had far too many other projects to do, and the cold weather is putting me of spending any more time that required in the workshop! I might get started on the control cabinet next month..