Cutting aluminium foil to a pattern

General
1

Advice please;

I’m wanting to build a bitter plate electromagnet. Essentially this means many (read: hundreds) of layers of foil with an insulating layer between.

An example of a complex pattern;

The holes allow coolant, and structural support. The thin layers allow many “turns” and the width allows high currents.

Also, it’s interesting.

I’ve thought of a couple of ways;

  1. Etching from template
  • placing insulator on one side, foil on the other, with toner transfer or similar resist
  • pros; known technique
  • cons; doesn’t cut the insulator, limited throughput, difficult etching through aluminium oxide, dangerous heat
  1. CnC milling
  • milling a composite of insulator and aluminium foils, or a stack thereof
  • pros; semi-automated, faster than etching, cuts foil and insulator
    -cons; may be single layer at a time; tool head likely to rip foil; ? Feasibility on space hardware
  1. Plasma via CnC
  • making a simple X/Y stage CnC, and using the tried-and-true graphite pencil with 9v battery stack
  • pros; achievable machine build, interesting, able to cut foil
  • cons; not able to cut insulator, spark hazard, special machine build
  1. EDM via CnC
  • pros; interesting machine build, able to cut foil
  • cons; not able to cut insulator, higher degree of difficulty and voltage, spark hazard, special machine build

Truly experimental;
5) Lasercutting foil via matte-coat spraypaint

  • similar to Lasercutting traces in PCB blanks; spraypaint the foil, etch the spray and hope it takes the foil with it
  • pros; existing machine, minimal extra work (spray can also be insulator?)
  • cons; untried (although done with PCBs as above), access to cutter, limited throughput
  1. Press and die
  • pros; once made, reusable, simple mechanically, able to leverage existing equipment
  • cons; making said die, manually pressing each piece, needs to be harder than aluminium foil (I.e machined steel?

I’d appreciate thoughts

Cheers,
Lauren

1 Like
2

You wish to levititate frogs?

Would a photoresist be suitable insulator? I assume the high current means low voltage so the insulator doesn’t need to stand up to high potential.

Then the insulator is already on the foil after etchig. The only con then becomes selectivly removing the insulator from the parts of the disk you want touching then next disk.

3

No, just want to make a strong resistive magnet with a homogeneous field.
I’m unsure normal photoresists are insulating enough, but laptop tape and cling wrap certainly are

4

if gladwrap/cling-film is insulating enough - then dry film photoresist def will be if you pick one designed for tenting vias.

Are you making this from aluminium foil or copper foil? ON al foil I cant see a clean way to selectivly remove the resist though.

Also - have you considered spray painting on the insulation layer after what ever machining happens? I know sprayable epoxy insulation is applied to Cu and Al.

5

How thick a foil are you talking? Could the laser cutter not cut everything if it was coated with your insulator and the aluminium was thin enough?

6

I was going to start with “kitchen” foil, so not thick, but you rely on the paint/resistive covering allaying the metal, because aluminium itself will reflect much of the IR and dissipate heat quickly.

Anyway that was one of my thoughts, but not sure the digital guys would be keep on the experimentation

7

Yeah. It really is test situation… i figured the thin stuff may not be able to dissipate all the energy quick enough and thus get cut…

My other thought was to start with a nonconductive material, cut it then electroplate one side of it…however looking at the currents involved with the magnet this might not work?