[franzschluter]

Hello guys. I am new to this forum and would like to discuss in detail regarding homemade edm sinkers and wire-edm.

History:
In my 3 year experience of building sinkers I am now planning to go into the next step which is CNC Sinkers (Orbital Axis) and EDM wirecutters.

Machines I built previously were all analog meaning no computers involved and ran on primitive analog circuits. I built 3 machines which were.

EDM Machine #1. RC sinkers directly from Ben Flemings book which was an RC type. It did its job but didn't work nicely with copper electrodes due to high wear outs.

EDM Machine #2. From the disadvantages of the RC machine I built my very own pulse EDM. It runs on 380V 3phase and electrode open voltage is 105.4VDC and can let 120 Amperes flow. It is capable of generating 100Hz to 20kHZ. Some range of frequencies produces DC ARCing depending also on "ON" and "Off" times. This was a big DIY project and I used an OLD Broken AGIE sinker as its structure.

EDM Machine #3. Concluding that Pulse and RC has its own advantages. I combined the two setups into 1 machine that allows RC and Pulse spark generation. Pulse for roughing and RC for finishing jobs. The servo module is also now more complex than the previous versions. Not wanting anything to do with PLCs and PCs I designed a motherboard (LOGIC CARD) that consists of CMOS LOGIC gates for controlling the entire machines process. A software called LOGIC FRIDAY assisted me in creating the complex board. All limit switches and buttons buttons operates on 12V.

Now to discuss my plans on future setups I need advice for a CNC WIRE EDM. I currently have the structure ready. I received an OLD AGIECUT Wirecutter that has been infested literally by RATS. Meaning its connections and circuits were unusable and eaten away. Only structure what I will use is its Table and Wireguides which are still in acceptable conditions.

The IDEA:
There are 4 stepper motors in the table. It has X and Y axis 400x400mm travel and two other axis U and V for producing tapper (Movement of head only). The tapper function seems a bit complex at first to me so I will leave this out. Going back to XY stepper motors I have disassembled them and am disappointed that no make or rating is written on it. There are 9 pins and I believe it is better to replace them with a CNC stepper motor + Driver board kit. What I want is the XY motors to be controlled via MACH3 software. I will make a limit switch of circuit that detects the voltage gap via probably a voltage divider. This send signal to MACH3 and will pause the cycle when triggered. Another voltage divider will be also designed to give another signal telling MACH3 to reverse run to go a few steps back till the gap voltage is finally reached the two voltage divider will have only 1 potentiometer and will be mechanically ganged. If open voltage is open it will advance starting the RUN cycle. Wire tension,flushing,Wire feed controls will be made independent from the program (Since I am a beginner in CNC).

Problems:

CHOOSING STEPPER MOTOR.
I am unsure what type of stepper motor to purchase for this job. The stepper motor that was in the machine has the following dimensions:

Body Length: 92.5mm
Body Radius (Round stepper motor): 83.8mm
Shaft Diameter: 9.5mm
Shaft Length: 32.6mm
Wirings have a common and is integrated inside (I think they call this unipolar). It has a total of 8 coils. Therefore it has 9 pins.

By looking at this perhaps someone here can recommend me what stepper motor is best to use for this application. I would not mind the machine axis to be really slow as long as it can be as accurate as possible. I have also included some pictures of the stepper motor that was mounted on it including the diagram how it was connected.

Software issues and problems:
MACH3 isn't designed for DIY CNC Wirecutters.
STOP OEM CODE:
I intend to use the STOP function as a trigger when the voltage gap is reached. But reading the manual it says that stepper motor may loose steps in this process. What will the real issues be here? I intend a really slow feed rate and I think it is unlikely to loose steps since the process is very slow.

Of course I would love also to use the FEED HOLD function instead. But I see problems that in simulation mode it is not braking fast enough for me. I do not know how to adjust this? We have to assume if it doesn't stop fast enough that it will hit the workpiece and the wire may eventually break.
Perhaps someone can advice me on this.



START OEM CODE:
I will use this to resume feeding the electrode to the workpiece when an OPEN Voltage is detected. When the voltage divider gives no signal it will simply trigger the START OEM CODE. I see also problems in this. As in the initial setup the OPEN VOLTAGE will really trigger the start button initially even when doing nothing. Meaning it would be impossible to work decently.


REVERSE RUN OEM CODE:
This is the key to how to make the wire retract when the gap is too close to the Voltage gap. Problems here include that in MACH3 it requires to be in the
"FEED HOLD" and then press REVERSE RUN. Notice also that this problem is in conjunction with the START BUTTON! Meaning by simply switching ON the machine it will already start because START CYCLE is triggered!

Possible solutions:
Perhaps someone is more familiar with MACH3 than me and can guide or perhaps give me a new light or hope. I have been only trying to use a DEMO version being unsure to purchase it or not. Though the Reverse/Feedhold/Start Cycle seems very useful to me.

Other possibilities is by programming a script or perhaps a macro for this? I have to admit that I have no talent in programming and perhaps this option might be no good for me unless someone could point me out.

Another possibility is perhaps there are other PC CNC controller software that has this function REVERSE RUN, PAUSE, RUN CYCLE.

Another idea which someone has already told me is that Plasma cutters have a function called torch height controller. I have no idea how this works and am also finding trouble where to get materials to read about this. And how it really works.

Any help is really appreciated as I am currently stuck in this phase.

Best of regards
Franz