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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

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steveastrouk

Best Answer 7 years ago

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
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Kitemansteveastrouk

Answer 7 years ago

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...

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steveastroukKiteman

Answer 7 years ago

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

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Kitemansteveastrouk

Answer 7 years ago

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).

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RavensCraft

7 years ago

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
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KitemanRavensCraft

Answer 7 years ago

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.

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RavensCraftKiteman

Answer 7 years ago

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
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steveastrouk

7 years ago

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.

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steveastrouksteveastrouk

Answer 7 years ago

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.

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steveastroukKiteman

Answer 7 years ago

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.

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Kitemansteveastrouk

Answer 7 years ago

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

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steveastroukKiteman

Answer 7 years ago

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

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Kitemansteveastrouk

Answer 7 years ago

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

We'll see...

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steveastroukKiteman

Answer 7 years ago

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

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steveastrouk

7 years ago

What plane is it springing in ?

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Kitemansteveastrouk

Answer 7 years ago

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
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frollardKiteman

Answer 7 years ago

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

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Kitemansteveastrouk

Answer 7 years ago

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

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Re-design

7 years ago

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

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rickharris

7 years ago

Why not use a bit of sponge?

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Kitemanrickharris

Answer 7 years ago

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

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Kitemanrickharris

Answer 7 years ago

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

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frollard

7 years ago

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.

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Kitemanfrollard

Answer 7 years ago

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.

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rickharris

7 years ago

1 mm ply or polypropylene

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steveastrouk

7 years ago

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

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Jayefuu

7 years ago

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