seeking sheet material ideas for small prototype project

[jkn]

Hi all I'm musing on a suitable sheet material to use for a little experimental prototype I want to make.

some points for consideration:

- we are talking about parts a few cm to a few tens of cm in size

- splashes of liquids are likely; nothing too corrosive, IPA in solution etc.

- I want the material to be fairly easily cuttable/shapeable

- parts will need to be fastened together - screwed or possibly glued

- some strength required, but not massive strength

- I have hand and power tools but no power cutting/shaping tools; so a pillar drill but no router or table saw.

The ideal material for this would probably be polypropylene sheet (old chopping boards?), and it may come to that. But in the absence of power tools I can see the finish of that ending up rather cruder than I would like

Foamboard is probably a bit too lightweight and not quite strong enough. There is also the water resistance to consider.

Wood, perhaps waxed or oiled, I can see working at a pinch. Cleanliness is important though and I am mildly concerned about sealing it properly

I'm really just trying to find out if there is anything else in the ballpark. My Dad would undoubtedly have used red fibreboard, but he didn't leave me enough for this particular project...

Thanks for any thoughts

J^n

[Theo]

What kind of finish do you want? Is this related to surface colour/texture, cleanliness of cuts, or what? Because if the surface finish is important, pick a material with the right surface finish (if 'old chopping boards' aren't good enough, find some PP / LDPE / HDPE / acrylic sheet with an appropriate finish). I'm assuming watertightness isn't a requirement?

It would seem that a food grade plastic would fulfill everything on the list

- just a question of rigidity, fasteners etc. Glue would probably suffice for that, or bolt and glue if appropriate. With heat they can be bent which might help, although bending is not a very exact science unless you make jigs for it.

Theo

[The Natural Philosopher]

?? the sort of foam you will find these days - either polystyrene or whatever laminate underlay is made of - are pretty much fully water proof. Cut with a breadknife, glue with epoxy...

Finish is fine with sanding and then you can uses a waterproof varnish or polyester or epoxy resin with something like brown paper. tissue, or even silk nylon or glass fibre to given them a slick tough finish

Depending on the shape you could even mould the whole shooting natch out of glass fibre.

Again nothing beats a good glass and epoxy fiinish for real toughness sterility and water proofing

I think its still available.

[jkn]

Hi Theo I'm just saying that sawing of PP sheet is likely to give rough edges which I can't easily sand. Water-tightness is not a requirement.

If there is some sort of food grade plastic that is easier to work and finish with what I have available, then that would be great. But I haven't come across one...

Thanks, J^n

[jkn]

It is the surface 'paper/cardboard' coating that I am talking about in the context of water proofing.

Yeah, but have you seen the price? I wasn't expecting to have to *buy* some...

J^n

[Theo]

I'm not sure about PP, but have you looked at acrylic (Perspex)? Edges can be sanded to a polished finish using wet and dry paper.

You can cut it with a hand saw, or by scoring and snapping. It's also feasible to bend with a hot wire (or other hot item).

Theo

[jkn]

Hi Theo my limited experience of Acrylic for anything like this has been unsatisfactory. It is easy to shatter and hard to drill/tap etc. It would be a reasonable choice for a more finished version, but not for the initial lashup I am thinking of.

I am somewhat warming to wood at the moment, with a resin finish perhaps...

J^n

[Chris Green]

Polypropylene is difficult to glue.

[Chris Green]

It does crack very easily though, you have to be very careful when cutting or drilling it.

Sheet, rigid, PVC is what I'd choose if possible.

[Clive Arthur]

Copper clad fibreglass board as used for PCBs?

eBay No. 124757668090 is the first hit. Usually 1.6mm thick, but thinner is readily available and it's easy to join with a solder fillet. Score well and bend to break, clean up with a file.

[Clive Arthur]

<snip>

Far quicker to fun a blowtorch flame along the edge after initial sanding.

[jkn]

Hi Chris

Is that significantly easier to work than Acrylic? I'll take a look, thanks.

I have just had a thought - how about uPVC sheets, like in Double-Glazed windows? I know you can get it in a lot of shapes. Easy to cut, for sure...

J^n

[Steve Walker]

For a first mock-up, how about polystyrene (non-expanded)? It can be bought in sheets at model shops, is easily glued, cut, drilled and can be laminated if you want thicker layers, etc.

[newshound]

Some types of Nylon can be machined giving a relatively good finish. Perhaps sawn edges can be sanded, but it would probably have to be done by hand to prevent melting. Acetyl (e.g. Delrin) is a sort of "grown up" version of nylon. More expensive but very suitable for manufacture by turning or milling. Both are tough and impact resistant. Nylon absorbs up to 6% water and swells, Acetyl only absorbs 0.3% which is negligible in many applications.

PVC, ABS, and PTFE are available in sheet, perhaps too expensive? They will all drill and tap nicely. ABS and PVC can be glued very well by "solvent weld" adhesives.

All of these are available with various types and amounts of filler to improve mechanical and "machining" properties.

[Dave Plowman (News]

Aluminium sheet? You can buy it in various sizes/thickness from Ebay.

[RJH]

Agreed - but it's a nice material if you can cut it. I did it with a battery circular saw and some sort of general blade last time I cut some up. And I've bought an 'acrylic cutter knife' - just looks like a rigid blade to me - but haven't got round to trying it.

[Brian Gaff]

Is this based around a receptacle for a fluid, if so it might be that you could use an existing plastic box for that part, or cut a plastic bottle down the middle or cut the bottom off depending on the shape required. Many moons ago I used an old bulk bleach container cut in half for a film development bath. Brian

[Brian]

uVPC board? Cheap as chips. Easy to cut and glue. Easy to get. It isn?t that strong and glue is probably better than screws. It has a thin skin and a softer core.

[Martin Brown]

Offcuts of foamed PVC board as used for shop signs would be the first thing I would consider. Make a prototype out of cardboard first so you have some templates to work from.

Have a look on Fred Aldous's site for something suitable... (or cheaper plastic sheet offcuts on eBay)

[TimW]

+1 or as someone said upvc , white and 6mm thick of the sort used for soffits and bits of building trim. Stiffen and join if necessary with little Softwood strips, glued and screwed.

TW