Wotan Rapid 1 LinuxCNC Retrofit

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19 Mar 2021 23:31 - 16 Jan 2022 19:22 #202912 by deerefanatic
Hi all,

I'm in the process of acquiring a Wotan Rapid 1 CNC Horizontal Boring Mill. The mill is in solid shape, and was retrofit back in 1996 to a Dynapath Delta 50M. About 4 years ago, the roof over the machine's electrical cabinet sprung a leak and the motherboard of the control got wet and fried. Now the shop is closing and I'm getting the machine for the cost of moving it.

I have thought about sticking with the Dynapath, as I can buy the parts to get it running again for about $5000, but I think I'd rather go with LinuxCNC instead for a newer system.. The Dynapath is old, has very limited memory, and based on really antiquated hardware. Larger programs would require drip feeding, etc.

I'm thinking of Using a Dell PC that I have with Intel Core2 Quad, and MESA cards.. I have a couple questions...

1: Can you have a mix of both PCI express and ethernet cards in the same machine? I'd like to use PCI cards with daughter boards to control the machine itself, but this machine also has a remote operator interface on a swinging pendant. My thought was have one of the ethernet cards in there for the operators panel buttons and the MPG to interface to, vs having to have a huge bundle of wires running back to the control pc. The dynapath system had a board mounted in the pendant that communcated via CAN bus back to the dynapath control, but I'm guessing that would be a nightmare to reverse engineer.

2: Is there a particular motherboard/pc setup that is recommended for these conversions, like an ideal option? I know that it seems anything with good latency is fair game, but I also seem to gather that with the MESA cards, it's not really so much of an issue.

3: I have to do some digging, but I suspect that this machine uses Resolvers on the servos vs encoders. Is that a deal breaker, or will the mesa cards handle resolvers ok? I know my drives are Allen Bradley 1388's using 0-10v analog signaling. I also see that the machine has Heidenhain Linear scales with EXE 602E interface boxes, but it looks like they were used on the machine's original NC control and not used on the Dynapath retrofit (per the wiring diagram I have) I'd like the machine to be able to hold .0005 tolerances if possible, (assuming it's mechanically sound)

Here is a link to my google photos library of this machine and it's progress. photos.app.goo.gl/qvSGNdDSUBV871R8A

I'll start some separate threads with more specific questions and link them back here as a reference for anyone trying to pursue this in the future.

EDIT: The below links are other topic-specific threads started in regards to this project.. I'm linking them here for the sake of folks in the future undertaking a project like this.

I had trouble with the Y Axis acting crazy. Turned out to be a wiring fault:  Vertical Axis PID Tuning questions - LinuxCNC
 
Last edit: 16 Jan 2022 19:22 by deerefanatic.

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20 Mar 2021 00:54 #202921 by andypugh

1: Can you have a mix of both PCI express and ethernet cards in the same machine?

Yes, you can use any combination of Mesa cards that can be physically connected.


My thought was have one of the ethernet cards in there for the operators panel buttons and the MPG to interface to,


A 7i73 (or two) would be cheaper, and uses exactly the same cabling.

3: I have to do some digging, but I suspect that this machine uses Resolvers on the servos vs encoders. Is that a deal breaker, or will the mesa cards handle resolvers ok? I know my drives are Allen Bradley 1388's using 0-10v analog signaling.


Look at the Mesa 7i49. Probably in conjunction with a 5i24 as the FPGA card. (that is the combo running my lathe) I like resolvers.

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20 Mar 2021 07:18 #202935 by RotarySMP

2: Is there a particular motherboard/pc setup that is recommended for these conversions, like an ideal option? I know that it seems anything with good latency is fair game, but I also seem to gather that with the MESA cards, it's not really so much of an issue.


What a beast of a machine.
You are right, LinuxCNC is not that choosy about the PC. If you are using Mesa Cards, then you can get most to work. SInce you already have it, tr outh the live image, and you can see if it's got anyunacceptable latency behaviours.

You really only need one Mesa FPGA card connected to the PC, as Andy said. you can get basically unlimited I/O, Encoders, Step/DIR, Analog servo etc by adding SS daughter cards.
Mark

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22 Mar 2021 17:24 #203266 by deerefanatic
That's good info to know. I wasn't sure how much adding the daughter cards would affect the I/O and latency of the system. I'll definitely stick with a single FPGA then and just expand it.

On further investigation, it appears that there aren't actually any resolvers on this machine. The servo motors have Tach generators that are fed back into the servo Amps, but the dynapath was reading the glass scales for positional feedback. On one hand, that seems like a good deal as you can elminate backlash from the system, but on the other hand, maybe not such a great idea? Should I be planning to mount encoders to the servos?

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22 Mar 2021 18:00 - 22 Mar 2021 18:03 #203272 by RotarySMP
If the amps and motors work, that is the same starting point I had on my MAHO. All you need to do is connect each axis's two wires for +/-10V analog speed control from the 7i77 to the amp, and feed the linear encoder back to the 7i77. The amp closes the velocity loop and LinuxCNC closes the position loop.

Here is the block diagram from my Indramat manual...

Mark
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Last edit: 22 Mar 2021 18:03 by RotarySMP.

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22 Mar 2021 18:25 #203276 by deerefanatic
Simple.... I like it. It must be a german machine thing then, (not having rotary encoders on the motors).

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22 Mar 2021 19:10 #203282 by andypugh

On further investigation, it appears that there aren't actually any resolvers on this machine. The servo motors have Tach generators that are fed back into the servo Amps, but the dynapath was reading the glass scales for positional feedback. On one hand, that seems like a good deal as you can elminate backlash from the system, but on the other hand, maybe not such a great idea? Should I be planning to mount encoders to the servos?


If you are keeping the drives then just leave the tachos closing the velocity loop and let LinuxCNC use the scales to close the position loop.

This is about as simple as a LinuxCNC servo retrofit gets, and should give excellent results.

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