605Views33Replies

Author Options:

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.

34 Replies

user
steveastroukBest Answer (author)2012-09-01

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

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-01

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...

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)Kiteman2012-09-01

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

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-01

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).

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-01

Oh, my word, you are a star!

Select as Best AnswerUndo Best Answer

user
RavensCraft (author)2012-09-01

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

Select as Best AnswerUndo Best Answer

user
Kiteman (author)RavensCraft2012-09-02

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.

Select as Best AnswerUndo Best Answer

user
RavensCraft (author)Kiteman2012-09-02

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.

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2012-09-02

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.

Select as Best AnswerUndo Best Answer

user

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.

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)Kiteman2012-09-02

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.

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-02

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

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)Kiteman2012-09-02

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

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-02

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

We'll see...

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)Kiteman2012-09-02

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

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-02

Oh?

What software is this in?

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2012-09-01

What plane is it springing in ?

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-01

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.

Select as Best AnswerUndo Best Answer

user
frollard (author)Kiteman2012-09-01

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

Select as Best AnswerUndo Best Answer

user
Kiteman (author)steveastrouk2012-09-01

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

Select as Best AnswerUndo Best Answer

user
Re-design (author)2012-09-01

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

Select as Best AnswerUndo Best Answer

user
rickharris (author)2012-09-01

Why not use a bit of sponge?

Select as Best AnswerUndo Best Answer

user
Kiteman (author)rickharris2012-09-01

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

Select as Best AnswerUndo Best Answer

user
rickharris (author)Kiteman2012-09-01
user
Kiteman (author)rickharris2012-09-01

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

Select as Best AnswerUndo Best Answer

user
frollard (author)2012-09-01

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.

Select as Best AnswerUndo Best Answer

user
Kiteman (author)frollard2012-09-01

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.

Select as Best AnswerUndo Best Answer

user
rickharris (author)2012-09-01

1 mm ply or polypropylene

Select as Best AnswerUndo Best Answer

user
steveastrouk (author)2012-09-01

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

Select as Best AnswerUndo Best Answer

user
Jayefuu (author)2012-09-01

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

Select as Best AnswerUndo Best Answer