CNC Coil Winding Machine

[Swede]

Thought you IC types might get a kick out of this... it is one of the smaller CNC machines you'll ever see. It is a CNC ignition coil winding machine, powered by 2 stepper motors salvaged from 5.25" floppy drives. The mission was to wind 30,000+ turns of an incredibly fine-guaged copper wire in multiple layers on a Delrin spool. This wire was abysmally fragile, and the slightest drag caused breakage. The wire had to be laid down via 2 shafts in a CNC gear arrangement, with the pitch of the laydown feeder being the diameter of the fine wire - in other words, as the bobbin rotated once, the tiny tygon tube which fed the wire, traversed in X a distance equal to the wire diameter. Thus the coil was laid down in an appearance similar to a spring with no gaps.

Each layer of winds was insulated from the next with a section of kapton tape, very tedious. This was needed because the outer turns of wire ehibit a huge potential (>10,000V) relative to the first turns, and the spark would arc internally without the insulating layers.

The stepper drivers are 1A Ramsey stepper motor kit boards. The software I wrote using VB, directly "printing" to the parallel port.

[Swede]

Here is a picture of the laydown assembly. The wire feeds from the back, and over several very small plastic pulleys, ultimately feeds into a tygon tube and then onto the bobbin. The carriage is on a 40 TPI shaft, and can be repositioned as the coil "fattens". The exit point of the laydown carriage needed to feed the wire directly onto the bobbin.

[Swede]

I've only made 3 or 4 coils, and even with CNC they are very labor intensive, mainly due to the kapton tape insulation. I'd like to find a thin enamel which I can brush onto each layer to insulate, which would wick into the wire and replace the tape.

One of the coils was mounted into a gas turbine "buzz-box" ignitor. Pressing a button on the box causes a continuous buzzing spark through a 1/4 X 32 plug. This caused instant ignition in my MW54 gas turbine, but the stray votages played hell with ECU electronics, so it was shelved in favor of a conventional glo-plug.

[bb99]

Nice Work!

What is the overall size of the machine?

--bb99

[HuFlungDung]

Very interesting, Swede

The professional motor rewinders which we do some work for, use "magnet wire" that is pre-insulated with some kind of high quality lacquer insulation. Is this what you are using, but adding seperate insulation too?

[Swede]

bb99: Thank you! The uprights on the machine which form the supports for both axes (bobbin and laydown carriage) are 2.5" apart. Those little motors are gutsy for their size. I remember (this was about 1999) going through a big box of 5.25" drives at a PC store and buying about 5 for maybe $3 each. There were a number of different steppers in them, some good for this type of project, some not so good. These are 1.8 degree unipolar steppers. Some of the disk drives had steppers which were integrated with their leadscrew device and weren't suitable.

HuFlung, the wire is enamel coated, 44 guage, 0.0026" dia. It is insulated, but the trick with the coils is that each LAYER of winds must be insulated from the others. The coils generate about 20 kV, with a steadily increasing potential from one end to the other. The thing to avoid was allowing the last few turns to arc between layers to the first few turns, as 20,000V will jump a big gap, and once even one arc occurs inside, it leaves behind a trail of carbon, which conducts, making subsequent arcs automatic.

Here is a source of magnet wire online:

http://www.planetengineers.com/defau...Wire%2C+Magnet

Get this, the 54 guage copper is so fine that 1 pound will unwind to a length of 156 miles!

If anyone else is interested, get Bob Shores's wonderful book "Ignition Coils and Magnetos in Miniature. Bob is an older, ultra talented gentleman who has plans for a number of sweet little engines, which I noticed a few of the guys are working on. His book is worth every penny, as it has great info not only on coils, but on ignition circuits and methods for small engines.

Here is one last pic, showing a finished coil potted into a delrin tube. These coils can also be mounted in a wax filled box (like a model T coil) for a cool scale appearance next to a small farm or hit and miss engine.

If I can find some thin liquid insulating enamel, I'd like to resurrect this device and crank out some more. Maybe there's a market for them, as the coils you can rip off from a wrecked 2-stroke garden tool almost always have electronics potted inside, and they aren't suitable for a straight CDI or kettering ignition for our small engines.

[anoel]

Very cool....

I'm into winding guitar pickups. Not exactly the same thing but It involves wrapping 9,000 turns or so of 42-44awg wire onto a bobbin.

I made my own winder. (Cut most of the parts on my homemade CNC machine.) The machine uses a cam driven traverse. It works very well. I've got to clean up a few things but the pickups I have wound sound and function excellent.

[bb99]

anoel,

What is the LED number on the right? Number of windings?

--bb99

[anoel]

It's a digital counter, it can be used as an up or down counter. I use it as a down counter. I placed a small magnet in the faceplate and use a halleffect switch to trigger the counter. Once the counter reaches zero it triggers a relay to shut off power to the motor.

[Bloy2004]

Cool! I like that machine too as well as Swede's...fascinating!

[anoel]

Swede, For pickup coils we pot them in a mixture of 80% Paraffin and 20% BeesWax. Heated up to about 140-150 degrees F. Some of the guys use a vaccum pot to sink th ewax deep into the coil. But just soaking the coil in the wax does a pretty good job on it's own since the wax is of a water consistincy at that temperature. That would work on your coils unless the temperature gets above the wax's melting point.

If it does, you might be able to score some Formvar varnish. A simple vaccum can be made to pot the coil deeply with varnish. THe only draw back is you've got to bake the coil for a good while to cure the varnish. The wax will dry on it's own.

[Swede]

Thanks Nathan. Ignition coils can get pretty hot, so I'd like to try something pretty resistant. What exactly is Formvar? The vacuum is no problem as I have a chamber made from surplus parts, ditto the oven, I've got a nice one for tempering metal. The real trick with HV coils is the interlayer insulation. I think the best would be a two-fold method, with either the kaption tape or some polymer between layers, followed then by the potting. In this size with the ultra-fine secondary, and no potting, even ignoring the arcing, the vibrations would ultimately cause failure. That wire is so darned fine!

Also I never noticed earlier but the prices on those enamel wires at http://www.planetengineers.com/defa...=Wire%2C+Magnet REALLY skyrocket above about 43 guage. THOUSANDS of $$ for a couple pounds of copper! WHOOOOOOO! But one spool of #44 or #45 will last a lifetime, darned near.

I'm psyched to make more coils now. I need to drag out my source code and refine the software.

Nathan, I like your rig and your concept for the hall IC/counter cutoff device. My problem is I have to halt between layers to do the insulating thing, so my software has a built in stop at the end of each layer. It'd be great to totally automate the whole thing, maybe that's be a fun goal for the future.