Manual EDM to CNC conversion

[Jim Estes]

I have an Elox 8-2012 Sinker EDM and I am interested in converting it to CNC. It is a very heavy machine, but there is virtually no load on the movement of the axis other than the weight of the table. I don't think I would have to merge anything with the existing spark control, all I am really interested in is a way to move the table around in 2 axis and a readout of where the electrode is located.

Any suggestions about what type of motors to use or what type of control to use. Is there a control that is only a positioning control and not a true CNC?

Thanks.
Jim

[Al_The_Man]

If you just want to set the table to a position before you use the sinker, would'nt a DRO do the job? With a scale on the X & Y. I assume you have auto control on the Z axis for sinking, the older Elox machines usually had a hydraulic servo valve for that function.
Al

[Jim Estes]

A DRO is what I have now, and I spend a lot of time cranking handwheels back and forth to set up, and then going from position to position. My DRO is damaged and I need to repair it, but I was thinking of trying a retrofit to it to save myself some time and sweat. I think my leadscrews are 10 TPI so I do a lot of cranking to get a part indicated in. Sometimes when burning multiple cavities, I will have a series of electrode that will get used in each cavity, I would save a lot of time if I could program the sequence of moves, (point to point) but not actually having a toolpath to follow. I guess what I am looking for is a very basic 2 axis control, but precision is the most important feature. Speed of the motion is not really a concern because moving the axis takes little time when compared to the burn.
Isn't there a new DRO/CNC retrofit for knee mills that is conversational and does just simple motion, I think it was Newall or maybe Anilam that had it. That is what I am looking for but I don't want to invest $7-8K for it.

Thanks,
Jim

[Konrad]

You might want to have a look at some power feed motor, you could attach easily, just like some Bridgeport Milling machine have.....an easier solution, before you pay big bucks for the real thing, like ballsrew, control and stuff!
Then, it would be, by just a switch or joystick moving your axes, but for positioning acurately, you still have to do it manually with digital readout.
Konrad

[Montana]

Jim,
Do you have the EDM Zap pulser on your Elox or do you use those trode smashing magnets that came with the machine.
I really like the Elox because it burns so fast and the hydraulics are very responsive.
What poser supply do you have?

[Jim Estes]

I have the Ram Pulser Box, (older version) and my power supply is an astra MKII. I also have the programmabel z axis, where you can program the pulse up and down, but it is a pain in the a$$ to program every time you start a burn so it never gets used.

I inquired with EDM Zap about doing an upgrade of this machine they gave me a quote of $23,000.oo to do everything, cnc, dc drive z axis, new pump and filter system, and total machine clean and paint. I just can't see spending that much money on an old machine.

Jim Estes

[accuratemike]

If you want to eliminate the hand cranking you could just hang two steppers on the ends of your existing lead screws. I would use double shafted motors and put the hand wheels on for fine adjustment using the DRO. I use Turbo CNC. In jog, you can go to X, Y position with a couple of strokes. No diagonals but it will get you there. Or you could write code for the positions with stops for the EDM process. Your machine and existing screws may be tunable for sufficient accuracy/repeatability. The DRO would tell the story in any event. I would use jog to get to the X-Y position, then depower the drive and fine tune using the DRO & hand wheels (negating any backlash & slop), lock and cut. Same could be done using code but, you will lose (correct?) position if you then fine tune with the hand wheels/DRO. You wouldn't need earth-stopping power. You could use a smaller board, like Xylotex or HobbyCNC, and affordable motors. ClickAutomation.com has some decent dual shaft motors. Good luck ! MIKE

[Kmed]

Have you thought about possible using the linear scale from your dro and link that to a servo system and controller? This way you dont need to use encoders, and the linear scale should provide the resolutio you need for positioning. (This is assuming that the scales are good and you electronic box is bad. ) I have been considering this on my EMD as well to use multiple electrodes.

[Montana]

I have the idea that the Elox scales are not that good. If it is you scale then what you can do is get some q tips with some alcohol and reach in between the wipers and clean the scale. That should do the trick, however, I still would make sure that you use the dial on the machine to cross check the DRO.

I really like the Newall scales that I attached to my mill some years ago. I think that I should put some on my Elox also to make it reliable.

[Jim Estes]

I hadn't given the EDM project any thought until the DRO quit on me. Since I am going to have to fix that, I was hoping to maybe improve the machine in the process. I am interested in CNC retrofits and was looking for a good project to get my feet wet on. This seems like the right project for me to work on, since I can use the machine like it is until I can get the retrofit up and running.

I have been interested in retrofits and home cnc for years, but haven't built anything as of yet. The biggest problem I have had with this stuff is the fact that there is so many options and so much information to wade through to find "the right system".

I guess what I am looking for is a very accurate system that can be changed and adapted without too much hassle. Speed is not a priority, however accuracy is paramount. I was thinking that I should just drop the DRO and build a closed loop system with rotary encoders. I would need a control that I could have a feedback input connected to in order to detect electrode "touch-offs" so that I could write programs to find the center of a block or the corner of a block. I used to work with CNC EDM's and they have a lot of neat tricks for locating workpiece.

The leadscrews are in good shape but they do have some backlash that would need to be accounted for, however I am not completely opposed to adding ballscrew.

I have a spare PC that I can use to run a control, so where do I start with putting a system together? How expensive would it be to do a full blown 2 axis closed loop system? I am thinking that I would need motors sized about like on a Mill/Drill.

Any suggestions you guys have are greatly appreciated.

Jim

[Jim Estes]

After a bit of research here, I am leaning toward using the Gecko G340 servo drivers. I dowloaded a wiring diagram from: http://www.timgoldstein.com/cnc/GeckoG320Wiring.pdf

and I have some questions.

Do I need to get the Camtronics Servo System LED Module?

The connections shown are for the EMC, I am assuming that is the Enhanced Machine Controller, from NIST? What are my other options for wiring this up, i.e. TurboCNC, MACH1, MACH2, etc. etc.?

Is there nothing else needed between the software and the Parrallel port connections to the drives other than the breakout board to wire it all up?

After hooking all of this hardware together, how hard is the process of getting the system configured to work with my motors, ballscrews, and pulleys, and switches?

The 12 vdc 1A Linear Power Supply, is that just a transformer to run the fans?

There are notes in the upper left hand corner of the diagram, is this the only capacitor in this system? The resistor the same thing?

What about the bridge rectifier, is that part of the power supply, or would I need to build that in?

If I choose much larger servos for my application, do I need to up the Voltage of the Power Supply? If so, how would that change the wiring of the system?

I haven't gotten into figuring out what servos to get, but I was thinking that the Gecko's would drive anything I would want to buy so they would be upgradable in case I wanted to build another system in the future.

Thanks,

Jim

[balsaman]

After a bit of research here, I am leaning toward using the Gecko G340 servo drivers. I dowloaded a wiring diagram from: http://www.timgoldstein.com/cnc/GeckoG320Wiring.pdf

and I have some questions.

Do I need to get the Camtronics Servo System LED Module? No


The connections shown are for the EMC, I am assuming that is the Enhanced Machine Controller, from NIST? What are my other options for wiring this up, i.e. TurboCNC, MACH1, MACH2, etc. etc.? You can use any of those

Is there nothing else needed between the software and the Parrallel port connections to the drives other than the breakout board to wire it all up? That is correct

After hooking all of this hardware together, how hard is the process of getting the system configured to work with my motors, ballscrews, and pulleys, and switches? Not too bad. We will help you along.

The 12 vdc 1A Linear Power Supply, is that just a transformer to run the fans? Not required, depending on what motors are used etc.

There are notes in the upper left hand corner of the diagram, is this the only capacitor in this system? The resistor the same thing? If using a transformer you need a rectifier and cap to make DC power. You can also just buy a ready made DC power supply.

What about the bridge rectifier, is that part of the power supply, or would I need to build that in? Part of the power supply

If I choose much larger servos for my application, do I need to up the Voltage of the Power Supply? If so, how would that change the wiring of the system? You likely don't need tons of power (big motors). The power supply voltage and current rating is based on the motor rated voltage and current

I haven't gotten into figuring out what servos to get, but I was thinking that the Gecko's would drive anything I would want to buy so they would be upgradable in case I wanted to build another system in the future. True

Thanks,

Jim