[crtroyer]

Greetings,

I am currently in the planning phase of retrofitting my 1989 Lagunmatic 310 control.
I recently purchased this machine from someone who had bought it from an auction, running at the time of the auction, and then stored in a garage for two years. It was well cared for in storage, and after the usual heartaches and $$ to move and set up and clean, the DynaPath20 control worked long enough for me to learn enough about it to really like it. But an unclearable E-Stop condition has convinced me to upgrade from the 26 year old control hardware. I'm grateful that the control worked long enough to demonstrate the mechanical soundness of the machine, as now I know that the machine is worth some investment of time and money.
My current plan is to use LinuxCNC running on a TBD desktop computer ( on my way to the computer store to do some latency testing today), with a Mesa 6I25, connected to a 7I77 with the 7I77ISOL (there's a lot of TIG and stick welding in the shop, and the 7I77ISOL seems like a sensible precaution.) As I understand it, the 7I77 card will control a 7I29 H-Bridge to provide the power to the Baldor brushed DC servos. The X and Y axes are Baldor MTE-4090-FL-5B servos, and the Z axis is an MTE-4070-FL-7B. The rotary encoders are BEI-Duncan E206-500-1 units, and seem to be working just fine.
Currently the only issues I see with this plan are the current unavailability of the 7I29 (out of stock on 5/16/15), the time required, and my general ignorance of electrical engineering. I'm a long time Linux user, so the command line and .ini files don't frighten me.
Any and all constructive input will be cheerfully accepted.

Thanks, Cyprian.

[dave3431]

What is the encoder count per user unit, lcnc tends to run best with higher count encoders.

[crtroyer]

What is the encoder count per user unit, lcnc tends to run best with higher count encoders.

Near as I can tell from the documentation I have at hand, they are 500 count/rev. But it is entirely possible that I am failing to understand something.
Thx.

[dave3431]

AFAIK the 7i29 can only be used in a torque mode which needs a higher resolution encoder for good stability.
If your motors have tachometer feedback to the original amps you are probably better re-using them, if they except analog input.

[crtroyer]

Dave,

The motors do have tachometer feedback, but I am planning to replace the original amps, both to upgrade to a more modern system, and to get away from parts that are well past their designed lifetimes where I can. Looks like I will be including higher resolution encoders in the project. Probably not a bad idea; as I calculate it, the maximum resolution on the existing system is/was .0002". Not at all bad for the time of manufacture, but we can do better today.
The reason I am looking at the 7I29 is that it seems to be the only part in the Mesa product line that can handle output power to match the servo motors. I would much rather overbuild the control side by 25%, and set it up conservatively, than underbuild the control and create problems for myself down the road.

Looks like I can get compatible encoders from US Digital. I figure that a 2048 count/rev encoder should be adequate for my needs, provided that is enough resolution to keep LinuxCNC happy.



Thx,
Cyprian

[dave3431]

Dave,
Looks like I can get compatible encoders from US Digital. I figure that a 2048 count/rev encoder should be adequate for my needs, provided that is enough resolution to keep LinuxCNC happy.
Thx,
Cyprian

I have had very positive experience's with US Digital, if you intend going with a simple amp, you also have the option of using Pico Systems PWM servo amps, they are similar price to a 7i29 per axis and AFAIK an equal capacity.

[crtroyer]

Update:

Turns out that my existing encoders will be entirely adequate for the project. They are 500 count /rev units, but as I understand it, LinuxCNC employs x4 logic on the encoder input section, resulting in an input resolution of 2000 pulses/rev. Coupled with ball screws that are actually .200"/turn lead, that gives a base resolution on the system of .0001" . I'd be kidding myself if I thought I actually needed better than .0005" accuracy or repeatability.
Maybe in the future I will upgrade the encoders to see what kind of results I can ultimately obtain, but for now, the emphasis has to be on getting the mill functional again.

Based on responsiveness of suppliers, looks like I will be going with the PICO systems Universal PWM Servo Controller and PWM input Servo Amplifiers. Per Mr. Elson's suggestion, I will also be incorporating differential receivers between the encoders and the PWM controller.

Back to work.

[NitroCH3NO2]

crtroyer,

I would agree that I don't think you can go wrong with the Pico systems equipment. I am also currently in the middle of a retrofit using the same equipment. The PWM Servo Controller and PWM Brushless Servo Amps. Jon Elson has possibly the best customer service out there. He has been willing to answer any question that I have had along the way. I am also using differential receivers on my setup.

I just removed all of the old controls from my machine today. I hope to get some of the new equipment installed tomorrow. I hope to get power back to the machine next weekend and start troubleshooting and tuning the servo system.

Good luck with your retrofit.

[JAKEFREESE]

Your Lagun retrofit sounds just about like my Hurco retrofit will be.

[extdrive]

Greetings,

I am currently in the planning phase of retrofitting my 1989 Lagunmatic 310 control.
I recently purchased this machine from someone who had bought it from an auction, running at the time of the auction, and then stored in a garage for two years. It was well cared for in storage, and after the usual heartaches and $$ to move and set up and clean, the DynaPath20 control worked long enough for me to learn enough about it to really like it. But an unclearable E-Stop condition has convinced me to upgrade from the 26 year old control hardware. I'm grateful that the control worked long enough to demonstrate the mechanical soundness of the machine, as now I know that the machine is worth some investment of time and money.
My current plan is to use LinuxCNC running on a TBD desktop computer ( on my way to the computer store to do some latency testing today), with a Mesa 6I25, connected to a 7I77 with the 7I77ISOL (there's a lot of TIG and stick welding in the shop, and the 7I77ISOL seems like a sensible precaution.) As I understand it, the 7I77 card will control a 7I29 H-Bridge to provide the power to the Baldor brushed DC servos. The X and Y axes are Baldor MTE-4090-FL-5B servos, and the Z axis is an MTE-4070-FL-7B. The rotary encoders are BEI-Duncan E206-500-1 units, and seem to be working just fine.
Currently the only issues I see with this plan are the current unavailability of the 7I29 (out of stock on 5/16/15), the time required, and my general ignorance of electrical engineering. I'm a long time Linux user, so the command line and .ini files don't frighten me.
Any and all constructive input will be cheerfully accepted.

Thanks, Cyprian.

Hi crtroyer,

Interested to hear how this retrofit turned out for you. I'm contemplating a very similar retrofit. I've got the same Baldor servos you have, so I'm very interested in your hardware selection. To be honest I'm still having a hard time wrapping my head around the whole thing. I think part of my problem is I'm still struggling with the terminology. Makes it hard for me to even conduct educated searches. Could someone point me to a good resource I can study to get the basics of a linuxcnc retrofit. My very basic understanding is that my servos, which have both an encoder and tachometer, interface with a servo driver which in turn interfaces with a linuxcnc computer. The more I look into it though the more I find terms like amp, daughter cards, encoder cards, etc and I don't know where they fit into the equation. I'm willing to put some time into research this all, but if someone could nudge me in the right direction I would surely appreciate it.

FWIW my setup is a wells index mill with an AB 8400MB controller that is getting too costly to maintain.

Thanks in advance.

[motoguy]

I would be interested in hearing how this is going as well. I've got an old Hurco BMC30 w/ Delta 20 controller, and I'm considering a swapout to Linux CNC as well. I've seen a lot about home builds and kits using it, but not much on refurbing industrial machines.