Author Topic: Miniature coil winder  (Read 566 times)

Offline Doc

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Miniature coil winder
« on: October 04, 2018, 09:36:24 PM »
Ok going to build (or attempt) to build miniature coils first need to build the winder. I'll post here if there is any interest in it if not no big deal we will see.
Anyway the first thing will be the gear package for it. It will be a version of the Side Winder miniature coil winder from Bob Shores book.  The book is a very good book if you want info on coils and windings  I recommend it.

George

Offline PK

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Re: Miniature coil winder
« Reply #1 on: October 04, 2018, 11:49:08 PM »
Really interested as I may be in the same boat soon....

Offline John Rudd

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Re: Miniature coil winder
« Reply #2 on: October 05, 2018, 03:27:52 AM »
Bring it on Doc, waiting to see it finished.. :dremel:
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Offline ddmckee54

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Re: Miniature coil winder
« Reply #3 on: October 05, 2018, 03:09:42 PM »
Whatcha gonna wind the itty-bitty coils for?

Don
Too many irons, not enough fire.

Offline Doc

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Re: Miniature coil winder
« Reply #4 on: October 05, 2018, 03:42:25 PM »
The IC engines I've built all have ignition systems already. I just want to try and see if I can do it, just to do it. Always wanted to try finally decided to give it a try. And who knows if I do succeed I may have  another IC engine build in the future that could use one ;)
George

Offline Doc

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Re: Miniature coil winder
« Reply #5 on: October 05, 2018, 04:03:05 PM »
Ok setting up machine to cut gears for the winder.

There are several gears needed all are 48dp  need one 16t three 32t one 72t and one 81t. Going to start with the 16t then the 32t after that probably the 72t as my indexer will index even degrees. For the 81t I may set up the machine to make my index strip for me first. Sure wish I would have gotten the A  axis when I got my machine. That would have mad things so simple oh well I always said I like a challenge. Haha


Anyway here is a video of setting up machine.

George

Offline Doc

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Re: Miniature coil winder
« Reply #6 on: October 06, 2018, 09:50:28 AM »
Ok cutting the first gear a 16t x 48dp  After this I will cut the 32t then the 72t and last will be the 81t. But before I cut the 81t I will set up the machine to create my index strip.

Here is #3

George

Online awemawson

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Re: Miniature coil winder
« Reply #7 on: October 06, 2018, 11:19:10 AM »
Interesting way of cutting your gears there Doc  :thumbup:

I'm trying to get my head round whether the gear is actually being 'generated' as it would be with a normal hob that has a lead to the cutter, and the work piece and hob rotate together. I suspect not  :scratch:

Much easier cutter to make though, and you've set me thinking about doing it completely automated with my 4th axis on my CNC mill. The 4th axis cannot be used like a continuously rotating spindle, as you would need for hobbing, but it can easily index tooth by tooth as you were doing manually.
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Offline Doc

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Re: Miniature coil winder
« Reply #8 on: October 06, 2018, 02:46:18 PM »
  I use to cut my gears with a single tooth cutter but after making a hob cutter and cutting them this way I have changed.
I used a spread sheet put together by a member on another board where has posted it. It is a very useful sheet. Gives you all the info for making the hob cutter. I've used this method a couple times now and work's pretty darn good. 
George

Online awemawson

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Re: Miniature coil winder
« Reply #9 on: October 06, 2018, 02:51:02 PM »
I suppose it's akin to a Sunderland Gear Planer in motion, in that you are pushing a rack form through the blank then indexing a tooth. OK the rack is rotating, which makes the cutting action easier
Andrew Mawson
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Offline philf

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Re: Miniature coil winder
« Reply #10 on: October 06, 2018, 06:11:13 PM »
Doc,

Are you just making cuts to full depth with the cutter centred on the gear? (If that makes sense!)

To generate a true involute you'd have to do many cuts rotating the gear slightly each time and raising or lowering the cutter accordingly.

I found a pretty good explanation here http://david.rysdam.org/machining/gears.html.

He got acceptable results just rotating the gear 1/2 tooth between cuts.

With just one pass he could feel the inaccuracy and the gears wouldn't run when fixed at the theoretical centre distance. With two passes the gears ran together smoothly.

That process would be very easy to automate on a cnc mill with a 4th axis. (Maybe a cnc 4th axis should be another project for you!)

Phil.
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Offline Doc

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Re: Miniature coil winder
« Reply #11 on: October 06, 2018, 07:27:50 PM »
Using the hob method each pass actually cuts 3 teeth on the gear at different angles. I've used this method before and works like a charm. Yes you probably won't get an absolute perfect gear but you will get a gear dam close and usable.
George

Online awemawson

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Re: Miniature coil winder
« Reply #12 on: October 07, 2018, 02:13:41 AM »
If the cross sectional form of your cutter is that of a rack of the correct dimensions, and it is long enough to encompass any teeth in mesh then surely by definition it must cut the correct profile.

Obviously the teeth in mesh will vary dependent on the tooth count
Andrew Mawson
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Offline philf

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Re: Miniature coil winder
« Reply #13 on: October 07, 2018, 02:53:04 PM »
If the cross sectional form of your cutter is that of a rack of the correct dimensions, and it is long enough to encompass any teeth in mesh then surely by definition it must cut the correct profile.

Obviously the teeth in mesh will vary dependent on the tooth count

Not so Andrew!

In a gear planer the cutting rack moves tangentially between strokes and the gear blank rotates a small amount generating the involute form.

With just one pass of a rack form cutter at centre height you get:



Rotating the blank a tooth (in this case 30 degrees for 12 teeth) you get:



That's as good as it gets - the involute is approximated with 2 flats.

Add a pass where you rotate the blank 1/2 tooth and raise the cutter the equivalent of 1/2 tooth you get:



The next pass would be another 1/2 tooth rotation dropping the cutter down to it's original height producing:



The involute is now approximated with three flats but some horrible looking artefacts at the root of the teeth.

So to generate a perfect involute you'd have to do an infinite number of passes rotating the blank and adjusting the cutter height accordingly. A compromise somewhere in between would give a very acceptable gear.

I chose a 12 tooth gear because this would accentuate the problem.

Hope this makes sense.

Cheers.

Phil.
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Re: Miniature coil winder
« Reply #14 on: October 07, 2018, 03:40:07 PM »
Makes sense, I'll stick to normal hobs  :thumbup:
Andrew Mawson
East Sussex

Offline Doc

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Re: Miniature coil winder
« Reply #15 on: October 07, 2018, 06:25:32 PM »
Yes it is not a perfect tooth profile you end up with 3 small flats on each side of the tooth profile. That being said the profile is plenty good enough for small model engines unless you are building a very high rpm engine. And you need ultra precision gears. I used this process in several motors now and they work just fine. As for the flats after running for some time they are pretty much gone. Unless you spin the gear at the same time as the hob is cutting it is truly not really a hob cutter.
George

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Re: Miniature coil winder
« Reply #16 on: October 07, 2018, 09:09:39 PM »
Preparing to cut final gear for build. Set up and let machine create the indexing strip.


George

Offline Doc

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Re: Miniature coil winder
« Reply #17 on: October 08, 2018, 07:34:36 PM »
Ok I setup machine and machined the last gear so the gears are completed. Next I'll start on the side plates and spacer block. The gears went pretty good. I'll have to remember to do my index strips like I did this one sure beats laying them out by hand. If I was still working I could have plotted them out on the plotter but the machine came through for me and did it correctly. Any way here is some clips of the last gear getting machined.



George

Offline tom osselton

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Re: Miniature coil winder
« Reply #18 on: October 08, 2018, 08:58:56 PM »
Seems to worked out I was wondering about the mesh because the tape was crooked in places.

Offline Doc

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Re: Miniature coil winder
« Reply #19 on: October 08, 2018, 09:35:57 PM »
I think I maybe not to good with the scissors the ends matched up fine when I put it on the indexer. So I'm thinking I cut it a little off. I noticed it when I put it on but the ends lined up so I went forward with it the way it was. Gear looks fine so it didn't effect it to much if at all.
George

Offline tom osselton

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Re: Miniature coil winder
« Reply #20 on: October 09, 2018, 03:07:54 PM »
It should still run in ok.