I shall have to show it to the latest crop of engineering graduates. The sad thing is, they come out of uni now with no idea about how anything is made, so un-makeable designs are pretty much par for the course. And now 3D printing has come along, they are designing things that can't be 3D printed!The designer bent across his board,
Wonderful things in his head were stored,
.......
He look again and cried, "At last!
Sucess is mine, it can't even be cast."
I’ve no idea who wrote this, I first saw it in Boston Lodge tea room as a very junior fireman in about 1973 or 1974.
That's a very neat setup. I bought mine with the main intention of making embossing dies for tinplate, but the other thing I am about to try is cutting out the spokes in handwheel blanks, using copper tube with spoke slots cross-cut with a jeweller's saw.I have an EDM sinker in my hobby workshop - but have only used it a couple of times. Once for squaring out a cavity for a motor/gearbox, and for putting dummy
The tungsten copper seen at top is the electrode, the hardened HSS axle material used is at the bottom.
The perspex tube is fixed to the copper electrode. As the electrode oscillates up and down, the perspex slides on the brass bush mounted on the axle. This bush keeps the pointy end of the copper centralised to the axle.
The perspex tube used here is to avoid filling the machine's 200 litre tank with EDM oil (when the front door seals to the tank looked suspect).
The nozzle at right squirts EDM oil through the side hole of the perspex - submerging the tiny area of cutting action with oil - as would happen if the tank was also filled.
One thing I thought of with EDM and 3D printing is that now you can do 8000K 3D prints in lost casting wax, you can make a clutch of brass or bronze lost wax castings, then use them as electrodes for the EDM with enough to make up for wear. It's just an idea at this stage.I also (for a time) injection moulded wagon and locomotive wheel centres using my own produced steel dies and machine. The split spoke wagon wheels were moulded in glass filled acetal, and to get the mould to fill properly, it needed to have 2 x 500 watt cartridge elements added, then water cooling.
In my amateurish setup, it was necessary to heat the acetal to its upper limit, and on one very unpleasant occasion, when it became overheated, the gas given off shut my body down and I flopped outside and lay on the grass to recover.
Other wheels were moulded in the more easily used polythene - for later burning out in the 'lost-wax' process to get brass castings.
It's still early days for 3D printed moulds to achieve anything like the crisply detailed locomotive bodies that we are accustomed to. However, a quite exciting 3D printed use is for sand moulds for casting parts for full-size locomotive builds and repairs, removing the need for conventional patterns and even those lately printed in polystyrene.
Returning to EDM, this process is probably of very limited value to the modeller as electrode wear is horrendous - if making parts in non ferrous metal. Electrode wear is much reduced when burning steel, but it's fairly typical for say four electrodes to be used to rough out and fine finish a cavity.
View attachment 206530
The previously rounded corners of this opening in a block of steel (an O gauge loco test block chassis) were squared out by the suspended copper block electrode - now blackened and partly worn from the process.
That is definitely interesting, I would like to see an example. It does potentially limit one to the lower temp plastics though. Definite possibilities for me but the majority of stuff I do is in metal so pressing, coining and die casting are my major interest areas, hence Mr Sparky still fills a need for me.Whilst not perhaps wholly relevant, it is now possible to produce commercially, for limited length injection moulded runs, moulding tools [complete with liquid cooling channels] that are wholly 3D printed in hard plastic materials. Thus, no longer does a tool have to be made of metal or produced by spark erosion - all of which leads to saving significant quantities of time, money and expertise. It is now possible to economically produce short runs of injection moulded loco bodies - measured in scores rather than tens of thousands.
That's a very neat setup. I bought mine with the main intention of making embossing dies for tinplate,
What model EDM machine do you have?
One thing I thought of with EDM and 3D printing is that now you can do 8000K 3D prints in lost casting wax, you can make a clutch of brass or bronze lost wax castings, then use them as electrodes for the EDM with enough to make up for wear. It's just an idea at this stage.
Wouldn't embossing dies be made more easily by using a milling machine, or by a lamination of steel plates? Presumably, electrodes would need to be milled first, so why do the extra unnecessary step - which end result wouldn't offer as good a finish?
The window frames in this cab side Rivets were pressed using simple tools straight off the milling machine.
Here again, better just to have the waxes used directly for lost-wax cast brass. This then caters for proper oval or H section spokes etc, which otherwise would need more complex moulds if EDM'd. In any case, if making moulds, properly milled cavities would be vastly superior.
Brass wheel centres cast from injection moulded polythene.
I'd be very pleased to see something you eventually produce with your machine.
-Brian McK.