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# combinatorial blow-moulding

for variety
 (+6) [vote for, against]

It is widely known that people buy bottled water for the packaging.
Clearly, making that packaging more interesting would be an advantage in the market-place. As far as I am aware, all commonly available disposable drinks bottles are highly uniform - perhaps for cost reasons, or in an attempt to imprint the brand on the consumer's subconscious.

The packaging for bottled water is ubiquitously blow-moulded. There are several interesting variations on this, but these all involve (at least) two mould parts which are transiently clamped together to create the moulding cavity.
I propose that multiple interchangable mould designs be used for each partial mould, and these be used cyclically in all combinations. The main restriction is of course that the edge profile of all moulding parts within each set must be identical. An easy way to allow all combinations to be used is to make the set size for each moulding part relatively prime - that is, have no common denominators (other than 1), and simply cyclically iterate through each set.
This has the desirable property that no two bottles in a case (of fewer than the smallest moulding set) will have a part in common.

One variation of blow-moulding which appears superficially amenable to this is "rotary wheel blow moulding". If wikipedia is to be believed, rotary wheels within these machines typically contain from six to thirty moulds. With two moulds, up to 870 combinations would be available (for wheels of 29 and 30 impressions).
It is of course the case that at least one wheel would have to vary its rate of rotation - with one speed matching the other wheel to allow casting, and a second speed to bring the next casing into position. This issue, and the need for a threaded neck, suggest that the injection stretch blow moulding process might be appropriate - which would potentially still be workable with a set of moulding wheels.

 — Loris, Jun 01 2017

The packaging design people are going to love this.
 — normzone, Jun 01 2017

 As an initial step toward this, it could be done if the variable part were not across the whole bottle. The simplest bottles are indeed two-part moulds, but many slightly more complex shapes might use three or four-part moulds, which come together in the same way, but allow the kinds of shape that won't easily 'pop out' of a simple two-part mould.

 Although the situation doesn't demand a three or four-part mould for this reason alone, it would also permit complex jiggery-polkary in one mould part (or two, one on each side of the bottle). This might permit, for example, a customisable shape such as a relief of the face of a random person on the front, and their arse on the back. As is commonly known, no two arses are the same, and the mould would be able to be formed on the fly using localised pneumatic or hydraulic limiting.

This only need to be an oval on the front and back, the rest of the bottle is the usual blow-mould pair.
 — Ian Tindale, Jun 01 2017

 I have logged some time in plastics molding - the people designing and manufacturing your molds will love this.

 The people running and maintaining them? Possibly not so much. But this is the halfbakery.

Can a customer get custom bespoke containers? Perhaps choose from a set of configuration options and have their own signature container, filled and delivered with a minimum case lot order?
 — normzone, Jun 01 2017

as an aside, I have seen screw caps with the mold fill mark on the top surface of the cap, leaving a little rough nub that makes me think "how is this possible in a functional society?" when I see it.
 — beanangel, Jun 01 2017

Yeah, once you get a grounding in plastic molding, using eating and drinking utensils made from plastics becomes amusing. And complex parts become more entertaining.
 — normzone, Jun 01 2017

There will be people who collect these bottles. A mint condition undrunk 843 may have some special value.
 — farble, Jun 02 2017

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