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Coil winding machine

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John Haine05/03/2021 17:50:45
3784 forum posts
220 photos

Being as how the next clock needs a coil with a lot of turns on it I thought I would lash up a cnc coil winder, since I have a couple of spare steppers, a GRBL Arduino controller that can accommodate another driver, and a driver to fit on it. The idea is to use one stepper driving the bobbin and pretending to be say the X axis while the Y axis stepper drives an M6 leadscrew backwards and forwards. On the leadscrew an anti-backlash nut will drive a carriage with a guide for the wire. Just to keep myself motivated I thought I'd log the build as I go...

To attach the bobbin to the motor I will use a mandrel in an ER16 collet so I'll need a suitable chuck. I've got a full set of collets and various closers, so the options were either to butcher a chuck extension, which would be a shame and anyway they are made of tough and hard steel, or make one. I chose the latter just for fun...


Turned down a length of 1" FCMS to 22mm by CNC and threaded a 15mm length M22 x 1.5 using Mach 3 - yes it does do threading, I was quite pleased with this thread, made my own tool as well. Nut fits very smooth and shake free...


Next to bore out the taper.


8 degrees half-angle, 16mm dia at the mouth and 20mm deep. Body was drilled 10mm dia x 22mm first.

John Haine05/03/2021 17:56:28
3784 forum posts
220 photos


A collet in the closer nut fitted to the taper. Back of the taper was drilled to the full length of the chock and reamed out 1/4" to fit the stepper shaft.


Then I transferred the bar in the collet to the mill and added 19mm a/f spanner flats. Then back on the lathe, parted off to 30mm LOA. This is the finished article temporarily fitted to the motor - need a set screw to fix on to the shaft.


All that went quite well! Next to start on the machine frame.

David George 106/03/2021 07:58:25
1525 forum posts
472 photos

Hi John. An interesting project what lathe are you using and did you convert it to CNC.


SillyOldDuffer06/03/2021 08:49:47
7042 forum posts
1549 photos

What a good idea! I'm sure it will work. How many turns do the coils need? Anything over about 30 turns takes ages, it's a tedious job - worse the coil is wound neatly - and I always lose count!


John Haine06/03/2021 09:43:59
3784 forum posts
220 photos

David, it's a Super 7, which I converted 10 years ago. Dave, at least 1000 turns, as many as I can get on a certain bobbin size. I tried a "manudraulic" method using my motorised DH to turn the bobbin and guiding the wire by hand but it was tedious and not very successful. Need to get better feed and more consistent tension.

duncan webster06/03/2021 09:56:32
3141 forum posts
52 photos

Excellent, keep the write ups coming. Will at least save me from butchering more relays when I need coils

Martin Kyte06/03/2021 17:04:06
2313 forum posts
38 photos

Are you making provision for coil tape between layers?

regards Martin

John Haine06/03/2021 22:07:48
3784 forum posts
220 photos

Ah, should I? The voltage and current in my application will be very low, is there any reason other than for insulation.

Martin Kyte07/03/2021 13:31:41
2313 forum posts
38 photos

It does help prevent the coils from the next layer burying themselves in the layer beneath and making an untidy coil. I have only would coils by 'hand' before but by that I mean on a mandrel in the Myford using the auto feed to traverse the winding with the wire lead throgh a friction device in the toolpost. The feed being reversed at the end of each layer. I found a layer of transformer tape when reaching each end helped to give a flat surface for the next layer and prevented the burying issue. You may find that you have enough control especially on wire tension to eliminate the problem.

regards Martin

John Haine07/03/2021 16:45:39
3784 forum posts
220 photos

Thanks for the explanation Martin. I want to maximise the number of turns on a given size bobbin and using only 0.15mm wire so I think tape would probably take more space than would be lost with a bit of untidiness. There's a few YouTube videos of diy coil winders that show pretty neat layering without tape so I hope it will work OK.

John Haine15/03/2021 12:22:16
3784 forum posts
220 photos

Slow progress but have got the basic framework together.


Back left motor drives the bobbin, front right the carriage. The carriage will run on linear bearings on 2 silver steel 8mm rails - these left over from a previous project to build a 3D printer. 3D printer inspired (if that's the word...) the use of M8 studding and 8mm Valchromat (left over from clock case) for the framework. The rails are also captive on M5 bolts clamping them on to the end plates, so the whole structure is very rigid. Definitely for function not looks. I have to admit that the chuck and the leadscrew coupling are both loctited in place on the stepper shafts. Next bit to make is the carriage.

John Haine17/03/2021 08:59:36
3784 forum posts
220 photos


Carriage made, a block of Corian with linear bearings and threaded hole for leadscrew. Trial assembly. Need to figure out spool mounting and wire run now.

John Haine02/04/2021 14:50:16
3784 forum posts
220 photos
I added an extra stepper driver to the Uno in the electronics box that normally runs the mill power feed, generated a simple text file of G code and downloaded it to my phone, works exactly as expected.  Next step, add something to hold the wire reel and run the wire onto the bobbin.  Just posted my first video!

Edited By John Haine on 02/04/2021 14:53:13

Edited By John Haine on 02/04/2021 14:53:37

John Haine06/04/2021 13:07:06
3784 forum posts
220 photos

First coil wind completed. Not too bad for 1st attempt. 300 turns of 0.27mm at 60 per layer.


Bobbin made from a bit of 16 od / 8 id SRBP tube from the scrap box. New phone posts photos on their sides!

So far just typing G code into GRBL Controller app on my phone a line at a time.  First a G91 to select incremental mode.  Then, for one layer the statement is

G01 X18 Z60 F50

For the next layer the same but X-18....and so on.


Edited By John Haine on 06/04/2021 13:17:57

SillyOldDuffer06/04/2021 19:42:30
7042 forum posts
1549 photos

I'm impressed!


John Haine07/04/2021 18:21:53
3784 forum posts
220 photos

thanks Dave! There were quite a few breakages and pileups before getting this one, still need practice. Now I just need to remember what I needed to wind a coil for...

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