Air coil (self supporting) mandrel/former help

Question

Air coil (self supporting) mandrel/former help

bwinder (Mechanical)

(OP)

29 Aug 14 11:51

I'm looking for an old tried and true design for a mandrel or former in which to wind or form bondable magnet wire into free standing coils, which will allow the finished coil to be ejected or removed with minimal distortion, ideally none.

The machine I'm winding on has a typical "chuck" found in a drill.

My concerns are with the start position, means in which to hold/anchor the start lead consistently.

Means of which to "fence" additional layers so as they do not "fall over the edge" of underlying layers.

Seen here @ ~ 1:05, automation overkill for my needs.
See here

Thanks for any help

BillPSU (Industrial) · Answer 1 · 2014-08-29 15:37:05

bwinder,
How big of a coil are you making and what kind of volume will it be?

Bill

bwinder (Mechanical) · Answer 2 · 2014-08-29 16:01:04

~0.75" ID

Initial volume is few hundred. Any leads BillPSU?

I've spent the better of 4 years digging through patents but have not turned up a "winner". Right now I'm using an alnico donor from a field sample with multiple layers of kapton. Ideally I'd like to setup something like in the video shown above, even a manual "bolt action" type of mech/mandrel.

BillPSU (Industrial) · Answer 3 · 2014-08-29 17:05:40

This is like any other tooling job. You decide what equipment you need/want and to use and the tooling required to complete the process.

I would start with a small benchtop lathe and design and build a mandrel using a faceplate drive mechanism and the tail stock center. Use a linear actuator to drive the wire feeding mechanism. The wire feed mechanism would probabably need a ceramic guide for the wire. The mandrel would split into two pieces with a slot in the end to feed the wire through for driving the wire around the mandrel.

Two mandrels will be built to allow unloading the mandrel why the other one is running.

The machine in the video is a custom machine built to do just that job. You won't find a 'standard' machine available to do this function.

Bill

bwinder (Mechanical) · Answer 4 · 2014-08-29 17:32:28

The machine in the video is a standard operation for forming self supporting coils. Usually automated, they wind the coil on a former and retract this former into a shaft/fence which allows easy removal of the coil (though sometimes anecdotally have found that automating the "ejection" of coils with a foot that "kicks" the coil free from the "fence" it's pinned against can cause distortions or otherwise oblong coils.)

I'm trying to reproduce the mech of the mandrel in the video for more of a hands on manual process. A bolt action rifle comes to mind, where my coil is wound on the "bolt" and much like how a shell casing is ejected, we retract the bolt which leaves the coil against this fence where I can manually and carefully remove.

I'm all set up with a PWM DC motor with wire feed on a ball screw controlled by stepper motor. I am able to wind with very high resolution.

My bottleneck is the mandrel...

BillPSU (Industrial) · Answer 5 · 2014-09-02 16:35:57

Do a google search on round linear motion rail. Whatever you decide to build you will have to design.
Use the outer bearing and a round shaft. Add a Teflon wiper to push the coil off the shaft.

Bill

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Air coil (self supporting) mandrel/former help