prototype into fridge or freezer

[Ian Henderson]

Do you need to make a box?

Could you not just use a "lock n seal" freezer box and customise that?

[Kristjan Laane]

Thanks for the idea, Ian. A key feature of the device I'm looking to create is restricted access to the container (with a timed lock), so there will be a number of design requirements that will make repurposing an existing lock and seal box difficult. For this reason and in order to tuck away the electronics to-be, sculpting from basic parts with freedom to produce many shapes, sizes and compartments seems an inevitable need. Is working with some kind of suitable plastic in the hackspace a no no? (sorry if this is stupid, I have no idea how to work with materials like that)

Thanks,
Kristjan

[Ian Henderson]

Ok, I understand.

Depending on size, you may want to think about creating a prototype in thin plywood, possibly using the laser cutter, and then fibreglassing it for strength and security

I made a custom freezer box for a sailing boat this way and it lasted for years

I've never seen anyone doing fibre glass work in the space, but a small box shouldn't be a problem

[Kimball Johnson]

>
> I've never seen anyone doing fibre glass work in the space, but a small box shouldn't be a problem

I have, and as long as it's not too busy when you do it and you keep
the workshop ventilated it's no problem. When it's busy the fumes
might be a bit much though :)

Kimball

[Simon Howes]

Polycarbonate sheet (often called "bullet proof glass" although it doesn't get that property till you get to about 3/4" thick). Its a clear material like acrylic, and you can lasercut it. something like 3mm would be good for a pretty tough enclosure. You can solvent weld it together to make a pretty indestructable box.

Don't know about the bio side tho

On Feb 22, 2013 11:58 PM, "Kristjan Laane" <kristja...@gmail.com> wrote:

Dear hackers,

I'm completely new to hackspace, but heard of you in conjunction with some prototyping im stuck with - in short, im trying to create a special-purpose box that will be put in a fridge or a freezer, and that will have some sensors and locks on.
- Putting the electronics aside for now, I would be grateful for any advice on what material to make the box out of, something that could sustain negative temperatures for a long time (maybe some kind of plastic?). The box can also be thought of as a specialised section of the fridge (ideally plug and play looking as if it was part of the fridge in the first place).
- and whether it is possible to actually work with that kind of material in the hackspace?

Finding out about your existence was a great discovery for me and I'd love to hear any suggestions you may have,
Ta,
Kristjan

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[Paddy Duncan]

So have I, it rendered the workshop pretty well unusable for the duration
and some time afterwards. The user wore a gas mask, but no one else had
one...

[Martin Klang]

I think you have to be careful with polycarbonate materials, they're not all safe for laser cutting.
I tried with a translucent blue variety which made a horrible, smelly, probably toxic mess (it had passed the chloride test).
Why not use acrylic?

best,

/m

[Martin Klang]

or I meant to suggest:
make a wooden blank and vacuum-form with smth like high impact polystyrene - gives you much better flexibility in the shapes you can create.

hth,

/m

[Adrian Godwin]

Vacuum formed polystyrene or abs sheet would match the rest of the fridge interior well. Moulded corners rather than lasercut and glued sharp edges.

[Billy]

We can work a wide variety of plastics. Like others have said, check
the ventilaion when working with them.

Chris built a vacuum-former. It's next to the welding gear. Not sure
about the current functionality though.

Chris also worked on fibreglass in the workshop. Definitely think
about the ventilation. Also the dust levels in the workshop may not
help.

As for polycarbonates chat with Sol. He'll show you the materials
testing templates that you can use to test how well materials cut in
the laser. If it's not on the list of materials, test it and add it to
the list.

What about using plywood and marine varnish? As far as making a
composite laminate, marine varnish is designed to deal with harsher
environments than a basic freezer. If 3mm isn't thick enough, then you
could always double-layer it.

Also have a look at the resin-casting equipment. You'll need to check
the MDSS for the various resins to find the most appropriate material.
It'll work for creating a completely custom size and shape. It'll get
past the sharp edges/rounded corners issue.

Please add it to the hackspace blog afterwards. And if you end up
working with materials that we haven't used, log them on the wiki.

On 23 Feb, 15:08, Adrian Godwin <artgod...@gmail.com> wrote:
> Vacuum formed polystyrene or abs sheet would match the rest of the fridge
> interior well. Moulded corners rather than lasercut and glued sharp edges.

[Kristjan Laane]

Thank you for all the suggestions!

I have done a bit of followup research and polycarbonate (bullet-proof glass) seems like the first thing to try for my application (making the box hard to break into with the downside of sharp edges).

The contenders were high impact polystyrene (HIPS) and acrylic, which were also found to be food-safe (FDA approved) and sustain freezer temperatures.

I found that trentplastics.co.uk sells polycarbonate sheets and they can be cut to specific sizes beforehand, so laser-cutting may not be an issue, but I'm a complete noob in terms of putting the parts together - as Simon mentioned solvent welding can be used for walls (for polycarbonate to polycarbonate), but what can I do to affix a lock onto polycarbonate? Can I drill holes somehow and use bolts or use screws even? Is any specialised equipment needed?

Thanks again for your expertise!
Kristjan

P.S. I have attached a snapshot of my research in case someone needs to deal with similar issues..

[Billy]

Yes, you can drill holes, though why not just cut them with the laser?

Have you seen the boxes that Sol designed? They're held together with
bolts. Nice example of a different approach again.

>  container for fridge freezer.pdf
> 657KViewDownload

[Penguin]

I would suggest premade fibreglass sheet and glue it togethercwith epoxy. East Coast Fibreglass sold me a 600mm square sheet for £24 and some very useful west system six10 thickened epoxy in a cartridge gun tube for £15.

Cutting the sheet is a bit of a pain but speed and ease of assembly made up for it.

-matt

[Kristjan Laane]

Thanks Billy and Matt!

I would be keen to check out Sol's boxes and chat to him about working with polycarbonate, but I'm afraid I am completely new to the hackspace and don't know Sol :) Could anyone please provide me his email address, or if you are reading this Sol then are you going to be in the space next week Tuesday evening, the 26th?


Ta,
Kristjan

[Mark Steward]

Sol is Charles Yarnold (see elsewhere on this list).

Cheers,
Mark

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