Case prototyping

Lord Steve

I need a custom plastic case for my project.· Plus, it would be nice to have a prototype case.· This project is funded by the company known as My Wallet, so I can't go pay an industrial design firm.· Does anyone have any recommendation or experience with a particular CAD tool and/or prototyping house?

Leon

It would be much cheaper to design the project so that you can use something off the shelf.

Leon

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Amateur radio callsign: G1HSM

RDL2004

Assuming this is for a hobby type project where you will be doing drilling, machining, etc. yourself...

Rule No. 1: What Leon said.

It is generally much easier to fit a project to a case than find a case to fit a project.


Rule No. 2: Use plastic unless metal is absolutely necessary. Plastic is much easier to work.

Rule No. 3: Choose a design where the end panels are separate pieces of flat material.

Unless all you need to do is drill a couple of holes, those cheap metal cases made from two U-shaped pieces of bent metal are very awkward to work with.

For front and rear panels, it's much easier if you have a simple flat piece you can work on (and if you mess up, its much easier to replace also).

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- Rick

Drone

There's a relatively new 3D free-open-source cross-platform development environment that may help in your design. Look here:

openscad.org/

davejames

I have a question for those of you who work with plastic enclosures...what kind/type of drill bit should be used when drilling plastic? Not the real brittle kind of plastic, but the softer stuff (ABS?).

My drilled holes usually turn into jagged messes or I end up with a cracked case. And yes I start with a small bit, working up to the final size.


Thanks,

DJ

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kf4ixm

DJ,
i have found that drilling at a high speed usually gives me better results, just my 2 cents worth though....

Phil Pilgrim (PhiPi)

Small holes are usually not a problem. For larger holes use a Unibit step drill. They're a bit pricey, but they cut plastic very cleanly and won't catch in thin materials during punch-through like a twist drill does.

-Phil

Leon

I use a taper drill.

Leon

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Amateur radio callsign: G1HSM

davejames

kf4ixm - I've tried the high-speed approach, but the punch-through, catchy-thing that Mr. Pilgrim menitoned nearly took off a finger!

Mr. Pilgrim - well actually, I have a Unibit but never thought it would be appropriate for plastic. I'll give it a go.

Leon - by 'taper drill' do you mean a Unibit?


Thanks all,

DJ

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erco

You actually want to dull your drill bits somewhat to use on plastic to avoid catching when drilling through. Counterintuitive, but it works great on styrene & ABS. The idea is to heat the plastic slightly so it softens and won't grab. PhiPi's unistep bits also work well, Harbor Freight even has them on the cheap.

Fabricating with styrene is a breeze. Comes in every sheet thickness and rod diameter you could want. Score a line with an exacto knife & snap it for a perfect edge. Solvent bonds extremely well with MEK or equivalent. Paints well, and pretty tough too.

CA glues (superglues) work very well. Use medium or thick glues with an accelerator (kicker) for good bonding. Another trick is to use thin superglue with baking soda, it forms a rock-hard, strong, machineable blob. Useful for fillets, repairs, or even making small parts from scratch by building up, layer by layer.

You could also start with a Radio-Shack type styre project box for general size & structure, then glue on styrene externally for the final shape.

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·"If you build it, they will come."

davejames

@Lord Steve - sorry, I didn't mean to hijack the thread.

@Erco - baking soda and super glue?!?


DJ

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Thomas Fletcher

I little bit more of a process but if you wanted something unique and able to make duplicates. There
is the ancient art of mold making. Design it in clay. Make mold out of plaster of paris. Then
use plastic resin for the case. A while back I found a site selling a non-toxic plastic resin (most release pretty nasty fumes)
but lost the link.

A video link


Post Edited (Thomas Fletcher) : 12/28/2009 10:13:27 PM GMT

Timothy D. Swieter

For case design the others have mentioned plastic and metal but you could also make it out of wood or fiber glass or other materials. You could design the case in Google Sketchup, which is a free design software. You could also use something like the free version of Alibre, which is 3D CAD/CAM and has a steeper learning curve.

For fabbing the case, you could consider something like laser cutting or 3D routing with machines like ShopBot or similar. If you have a nice design and are easy to work with, you might be able to use the forums to find a hobbyist with a 3D routing machince and would machine the case at a minimum cost. In fact, ShopBot has a program where they are setting up 'garages' around the country so that those who own ShopBots can offer easy to use services for machining.

What is the case going to look like? What do you want it to be? Do you have any hand sketches?

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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com

Leon

davejames said...
kf4ixm - I've tried the high-speed approach, but the punch-through, catchy-thing that Mr. Pilgrim menitoned nearly took off a finger!

Mr. Pilgrim - well actually, I have a Unibit but never thought it would be appropriate for plastic. I'll give it a go.

Leon - by 'taper drill' do you mean a Unibit?


Thanks all,

DJ

No, that's a step drill. It's this sort of thing:

www.machinemart.co.uk/shop/product/details/cht382-3pc-tapered-drill-set

Leon

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Amateur radio callsign: G1HSM

erco

Dave James: Yes, baking soda & superglue (CA)! Exothermic chemical reaction gives off heat and cures very hard & strong. Try it, you'll like it! Works best with thin CA; form your baking soda into a line or blob, saturate with CA and wait ~30 sec, sprinkle more baking soda on top then brush it off after it sets.

Helpful to keep fresh BS in a squeeze bottle with a narrow tip to dispense. Keep CA & BS tips out of the soup or you'll spend half your time unclogging the tip. You heard it here first!

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·"If you build it, they will come."

erco

Useful·random info on fabricating models & robots!:

http://www.core77.com/design.edu/tools/model.html

http://www.scalecorvettes.com/hints%20&%20tips/hints09.htm

http://www.robotbuilders.net/r2/

http://bobgreiner.tripod.com/

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·"If you build it, they will come."

davejames

@Leon - thank you for the info. So it's a "step-bit" without the "step". I'll look for it at the local hardware store.

@Erco - and thank you for the info. From revealing finger prints to hanging hard-hatted people from I-beams to maybe even repairing a cracked engine block...what can super glue NOT do?!?

(...smiles...)

DJ

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TonyWaite

I would buy an off-the-shelf-enclosure significantly larger than your project: the simplest box/lid
construction with easy access to all faces. Either in aluminium or plastic.

Then find your nearest one or two-man sheetmetal workshop: they will have all the punches, drills,
experience and _skill_ required.

For far less than the cost of the tools you can have a professional job in a fraction of the time.

Listen carefully to their advice. And when you're there, try a skills swap. Chances are that they've
got computer/electrical/electronic issues that need sorting and money need not change hands.

This advice may seem counterintuitive. I've got a small milling machine and tooling, a precison pressbrake
etc, but only use them on the weekends when my favorite toolmaker and sheetmetalworker are
unavailable.

T o n y

Scott4

Not sure what your budget is but Polycase (http://www.polycase.com/) has some nice enclosures and can use their high speed milling machines to put in all kinds of cutouts and holes. -Scott