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Laser cutting a spring - choice of material? Answered

I have a scheme that requires a flat, non-conducting spring.

Acrylic it too brittle for my needs, but I know that some plastics can, when cut with a laser, give off fumes and gases that will damage the laser cutter (eg PVC gives off gases that will cloud the mirrors).

What materials would you recommend?

(I've attached a quick sketch of the general shape of the planned spring.)

EDIT: I've added a rough sketch of the project - a torch, cut from acrylic. The four projections are to bind it together with an elastic band.  The switch operates like a syringe.

Discussions

I see what you're after, I don't think it will work as you've drawn it. Try this design instead.

kitemans spring.jpg

Oh, that makes much more sense (I had a mental image of a 2d sponge), thanks.

If that will work in acrylic, I could make it part of the middle layer...

It'll work fine in Acrylic - give me some working dimensions.

The CR2032 is 20mm x 3.2mm, so something around that?

It's not vital at this stage, I'm just trying to make a laser-cut version of a demo model that my boss made on a CNC machine in two layers (we don't have a CNC machine).

This might work a little better.
You will have to make the case a little wider to accommodate the wider spring and push button.

Spring Mod.jpg

I see what you're doing, but the plan is to make everything in that middle layer - the spring, plunger, & acrylic - all the same thickness as the battery.

You could do away with the spring if you make a push /pull plunger
like this. It could be the same thickness as the middle layer,
but you will have to widen the middle layer to accommodate the wider
plunger.

Plunger.jpg

Incidentally, this is a parametric model, you say how wide the spring is, how thick and how many turns there are and it renders it for you.

Alibre - there are similar facilities though in most modern CAD packages.
Alibre PE's about 140 quid. Mine's the 1400 quid version, with all the bells and whistles.

Yeah, well you only buy it once, and I can use it on three computers for the same licence. The top version includes CAM, FEA and sheetmetal working toolsets as well.

Haha, school would need it on at least 30 computers...

Well, you could always ask Alibre about academic discounts - Solidworks and Autocad do it, to sucker you into their 20,000 pound offerings

No point, the HoD has already paid out for something called Techsoft 2D

We'll see...

Oh god, that's an AWFUL package - its one of the ones the boys use at school.
Have fun/

What plane is it springing in ?

Flat - in the first sketch, compression would be left-to-right. In the second (just added), it would be from below. I want it to push a watch cell out from a pair of LED legs.

Laser Cut torch.png

Steveastro's drawing is almost exactly what we have working as a working spring inside a 'fake transistor' valve :)

Unsure right now - 50-75% of the uncompressed spring? ~5-10mm?

I don't know which is cooler, laser cut stuff or that Steve jumped on this so fast and did it.

Why not use a bit of sponge?

I need to retain the "cool, it's all been lasercut" factor - this is going to be a demonstration piece for a class.

Steve's modification actually makes it cheaper - the spring will be formed from the acrylic that is already there, and would otherwise be discarded.

I've personally cut springs out of 2mm acrylic and used them as compression springs - but again it all depends on how much force it has to withstand, and in what direction.

It's not the amount of force, it's the amount of deformation I need it to survive.

I've added another diagram to the question.

1 mm ply or polypropylene

Yeah, Delrin should cut very well - no nasties in the fume.
But what's wrong with plywood ?

Delrin is supposed to laser cut nicely and be more sturdy than acrylic. I never got a chance to try it though.