shop edm

[MrFluffy]

I think your on the money on PIKA, when the PIKA relay is engaged a little 4v hf waveform is injected between each pair of contacts. I can't see it, only a mess of sub harmonics so I guess my old tektronic d66 scope can't go high enough, but its there and clears that up thanks. I would guess the pair common'd at the relay should be on the - or earth side of the equation so it doesn't short out the contact block when its injecting the signal.
I also see a pulse between the edm cables, 80v if Im reading my dials correctly but not going the direction I would expect and I can't alter the waveform shape by playing with cutting conditions. I must have them shorting out for that pulse not to be making it to the wire. More sketching.

I have been playing round with the cutting conditions (with the wire not being spooled and a little tape to keep the break sensor from activating ) and it has the same sort of things. Sodick supply a big manual of what to enter in there for each type of material and thickness etc, which also of course I don't have.

I'll be happy to get it to make a spark and break the wire right now. But positive steps. A brew to thaw then back at it...

[MrFluffy]

And some tracing out, and lateral thought and ... WE HAVE SPARKS! I obviously need to set cutting conditions and things and I had z about 8 inches off the workface so I could see what was going on, but it was attempting to cut a lump of steel at 0.4mm/min but eventually the wire made contact with the workpiece and it errored out. Thank you Mr Mawson for your input on pika.

[awemawson]

Superb, excellent news and very glad to help. Do please keep us informed of further progress.

[MrFluffy]

First test cut, I don't have the book as above so guessed at some very very conservative settings, and although it was very slow, it managed a test cut. Here it is, 0.10mm wire, that is a 0.5mm fine point pen for perspective, the cut is above the nib for about 10mm.
I was going to do some Y moves, but I bumped V and I up too much and melted the wire, so have to rethread, although the way forward is to get hold of the official cutting conditions book.
There is a pinhole in the drain from the tank, and a connector on the DI resin system is leaking ,its a hozelock hosepipe qd one, they're often problematic. I'll try a new O ring on it and eliminate it if it continues.
But, feeling very happy with progress. Now to sort out the CAM toolchain so I don't have to stand and enter gcode into the mdi menu, and a pc98 cbus network card arrived from japan today, so I am going to have a go at making it networked so I can drop the code on it via my home network instead of having to write out floppy disks. I may have ordered the wrong model however as it has win95 drivers too indicating it might be for the later 386 based pc98's not my 16 bit one, but I'll just find the right one if so.

[awemawson]

I certainly find it only takes a little bit of progress to wind my enthusiasm for a project back up to where it should be, and it looks as though you are well on the way to having a very useful tool. I rebuild equipment really as a hobby as I like the challenge - certainly it's more the journey than the end point I'm after. But with my wire edm I find it such a versatile tool to have.

[Old Hat]

I rebuild equipment really as a hobby as I like the challenge -
certainly it's more the journey than the end point I'm after.
But with my wire edm I find it such a versatile tool to have.

Ditto That, as with nearly everything, as far as I'm concerned.

[MrFluffy]

Because we're all working on one big project, ourselves. I'm not wanting that end point!

I got the cutting condition tables, 78 page book, and armed with that and some very hard steel out of a old mechanism I set to testing. Still just typing things into MDI mode though.


The cut is so clean on inspection, and this is just a one cut rough cut. I was going to make a 0.2mm thick comb into one of the faces but I'm going to try an actual piece I want to make instead of noodling around making test pieces.


I *think* I have the cam problem sorted, the machine needs the gcode wrapping in quotes and each line needs a semicolon to terminate it. My program isnt writing that, but under linux the following shell command ran against the files makes it work (it passes them through sed and awk). I'll work out the correct way to do this with a post processor now, rather than the old unix hacky admin way :-
sed 's/\r//' WFLUFFY.NC |awk '{print $0 ";"}' - | sed 's/^.*$/\"&\"/'>WFLUFFY-FIXED.NC

Going to order some surgical steel too for those last minute gift requirements for my wife

[Old Hat]

You Gotta be one Happy Camper!

[DICKEYBIRD]

That's a wonderful result! You gotta be "riding tall in the saddle" now. Congrats! There's probably a lot of similar type machines covered in dust lying around in shops & warehouses that'll end up being scrapped out or parted out for pennies...what a shame.

I'm curious, does the type of steel alloy affect the required feed/speed/power level or does the system just see steel & cut away at the a generic rate. I suppose the metal thickness has a large effect on things as well? I've only seen one wire EDM working and that was 10 yrs. ago at a trade show.

[MrFluffy]

Yes, I am feeling pleased with it but tonight I decided to try aluminium cutting again and I have no conditions tables for that, but at least I got lots of practice in rethreading the wire when it broke a lot. I've ordered some new wire as I think that is partially the culprit too and I can reduce breakages by altering some of the conditions but then the cut is very slow. Its a matter of learning it and getting a feel for what works and its going to be frustrating at first. The tool steel cut above just seemed for everything to be right and the machine got into its happy zone.

As for your queries about thickness, the cutting conditions book is a series of tables with all the listed types of a material, and for each grade theres a table for a set thickness and on that table each row lists the parameters for that exact spec. The one I have covers steels, copper, carbide but not aluminium. Its 58 pages thick for just the tables themselves.
The machine parameters mean it cuts slower for thicker materials, they are rated in square inches of cut area or mm2 / hr, so more square inches thick means less linear progress.

The parameters listed for each include the on time of the pulse, the off time, peak current, voltage, the value which it considers the electrode to be unstable, the delay time to back off and recover from the instability, servo voltage, servo speed, wire tension, wire speed, water flow rate.
The machine itself is constantly doing a balancing act between advancing the feed, controlling the voltage and current etc according to what it senses is happening in the wire to the cut progress. It adapts its feed rate to how its going and you can see the feed figure altering in real time as it does this.
Ultimately I would like the cam system to write the condition values in that table into the actual gcode automatically when the right material is selected, but that may be some time down the road away.

Before it cut the above test piece, I've never seen a wire edm working at all & Its all learning to be done, I'm enjoying it despite the frustration of being a total novice to it.

[DICKEYBIRD]

It's amazing that your machine is able to make all those multitude of on-the-fly changes at this early stage of your refurbishment process without your having had to repair a huge pile of little magic bits & pieces.

The one EDM I saw at the trade show had a big lump of different laminated materials on display next to it that had allegedly been cut with the machine. The lump had been cut into 2 pieces with a wiggly cut line and the lump looked to have layers of steel, brass, aluminum, carbide, stainless and several other materials. The salesman made us run a thumbnail along the edge and see if we could feel the edge of the different materials. Back then, I knew even less about machining equipment and I just assumed it was possible and not that amazing. Who knows, it could have been a hand-fettled piece??

Anyhoo, please keep posting your progress; it's fascinating.

[awemawson]

Mr F, my wire edm has a table of cutting conditions in memory, and under program control you can call up which line in the table is in use. This way you can alter conditions dynamically. The table can be loaded into the machine either manually or via the rs232 link. While it is cutting you can call up a page showing the conditions and manually change them as the machine continues it's cut.

My machine is earlier than yours (1984) and as manufacturers tend to pinch each other's good ideas I'd be surprised if something similar insn't in yours.

Good progress by the way

[George Bulliss]

Just like plunge EDM, flushing is extremely important and with a non-submerged machine you are at a disadvantage to begin with, so flushing is the first thing I would look at. Thicker work is harder to flush and any cross holes will cause problems; best to block any holes before cutting. A large gap between the top of the workpiece and the upper flush will cause problems, too.

I can’t remember the specifics, but the aluminum settings I used weren’t too different from the steel settings and the stuff cuts like butter. Aluminum is pretty dirty to cut though, the tank used to turn black almost immediately; another reason I would look to the flushing before the settings.

[MrFluffy]

The aluminium is thinner in section than the sucessful steel piece above, but noted on the flushing. I've been trying to keep it dialled back a little on that front because the work table has a few small leaks when sprayed with water but the only thing which keeps wire breakage down seems to be to run less v so far. I priced the official rubber seal parts for the Y, UV and Z axis to cure this as they are all showing signs of distress, and the quote came back as the wrong side of $800 + shipping, so I am investigating some alternatives.

For the conditions, yes you can alter them on the machine on the fly, or also put them in the header of gcode programs or mid program to change conditions on the fly, that is the part I would like the toolchain to be able to do and needs some work. Perhaps its possible to set a array of presets and switch between them too, but I don't know the control well enough to know if this is possible.

I'm headed back out there now, I've been cornered into some honey do stuff in the house so its late, but I'll focus tonight on getting the various protective covers back in place instead of test cutting.

[MrFluffy]

One further comment, I haven't got the rs232 link hooked up yet. I was going to use a raspberry pi as a serial -> ethernet bridge inside the cabinet, so I could send programs to the pi via a ethernet cable, then dnc them into the control with rs232, but I've managed to find a CBUS ethernet card for the pc98 control computer, so if I can make that work, I can put the control pc on my local network and use dos netuse to map the storage diskette as a network drive and this will be faster than serial link speeds and not require manually dropping into the dnc communications menu each time. I can also remove the serial card which serves the dnc and tape reader freeing up a slot to take the network card.

The fly in the ointment so far is that I seem to have bought a too new ethernet card, and although it will fit my machine physically being CBUS, the device drivers are for the later 386 cpu architecture and will be binaries which are tied to a particular variant of a cpu.
It mentioned this in the auction but my japanese is non existent, if so I have to find another cbus card for the older chipset, and have it shipped over from Japan. Right now, I can write to the USER (second) disk with a standard PC with a floppy drive in it to put NC files on. The main SYS diskette is pc98 only (and linux! the raw pc98 images can be DD'd under linux 100% sucesfully) but the USER is read/writeable as dos6.0 format.

I would really like to eliminate those floppy disk drives from the control pc also, they are unreliable due to magnetism induced and slow, and they are not even standard 720k and good ones on ebay sell for $400+ apiece. I am in contact with a project in France who have a generic usb->floppy conversion device, but the pc98 lacks a timing signal for standard floppy drives so needs a extra circuit adding in especially for this model (a VFO to produce timing clock) which they have developed already. I'm going to work through getting it working so I can boot from usb flash drives, which hopefully won't be as affected by the magnetic fields generated in a edm machine. Then I can sell my 2 good floppy drives on ebay and recoup some costs

The above are just tweakery, I work with computers for my day job so thats more bread and butter stuff for me. Posting it out there might help someone one day though.