Step/Dir out of mesa 7i77

Hello,

my name is Sebastian, and my actual project is a Retrofit of a Metba MB25 CNC with El.Ge. Drives and brushed DC Servos.
I managed to tune all three axis, but now the z-axis-driver shows the error Led.(Shortcircuit Power Stage). After I have changed the Darligtontransistors the Problem already exists and the Transistors are broken again.

Now I have three possibilities: 1st to spend a lot of time in finding the error of the old drives without any manual or schematic.
(Perhaps i have luck)

2nd finding controllers for the old servodrives which can be controlled via +/-10V because of my mesa
7i77 card (or is it possible to get two +/-10V and one Step/Dir out of this card?)

3rd purchase three compleed new servo axis for example delta-drives.

Which possibility would be the best for my project and iss the 2nd one realistic.

Thank you for your help in advance

Sebastian

Personally, I'd probably just replace the one bad drive with a new one (with one that has +/-10v input)

I would tend to agree with Todd, just get a replacement analog drive

If you cannot do this, the best way to add a step/dir output to a 7I77 system is to use a separate daughtercard on the other FPGA connector.

This BOB/ daughtercard may be as simple as a $5.00 Ebay 5 Axis parallel port breakout or something fancier like a 7I76.

Sebastian. you didn't mention what the requirements of the your motor are? Does the Metba have a Tacho feedback loop or Encoder? What voltage and Amperage are motor rated for?

Before switching over to a new motor, needing a new pulley wheel, new belt, new cable, new drive, and breakout board, I'd go searching for someone who can troubleshoot and repair the current drive, and/or search for a surplus drive of the same model.
Mark

First of all thank you for your help.

To your Questions: The metba has DC-Servos running at 116V Z-axis has18A const. and 146A peak. max ref. are 3000 1/s. The Servos have Tacho feedback.
My actuall config is a Mesa 5i25 and a 7i77.
The costs for troubleshooting the old Z-driver are very high. And without any schematic its not possible to find the fault on my own.
I could get used mitsubishi AC-Drives+Servos 2x 1kW and 1x 1,5kW. Perhaps this could be a good alternative, because then I will not need the trafo and the line inductivities (for the servos) any more and have enough space for a frequency converter for the main spindle.

Sebastian

(Open for your thoughts)

There are plenty of old CNC machines from that generation with similar analog drives. Have you put out feelers on one of the bigger CNC forums like CNCZone, to ask if someone has drives sitting around for a complete retrofit? Someone like Stig Ove Ruud...


Also there are commercial vendors whos drives might seem expensive, until you consider the cost of everything you will have to replace.
www.cncpd.com/product/glentek-sma7115hp-...ush-servo-amplifier/

Hello,

I could buy some aerotech BA 30 drives which would meet my requirements. Only the max current isnt`t enoug for the max.PeakTorque of the servos (145A). If I am able to get the x-y-axis to work with these drives I will search a ba100 for the z-axis. The big ammount of these old drives iss that they have +/-10V Inputs a tach-feedback-input and are powered form 230V/50Hz Supply.
A question is, do I have to use the induktivities which are in row to the servo-motors, or are these not neccessary.

Thank you for your help