Product: Mold
Rapid prototype vacuum thermoforming   (+6)  [vote for, against]
vacuum thermoformer + pin array

Take one of the home made vacuum formers, where the top of the box is usually a peg board (ie an array of drilled holes to let the air be sucked out), and replace that with a pin board similar to what's used for art or as a childrend's toy.

Use it by lifting the top off and placing over an object to set the pin heights, then lock the pins in place, and replace on the vacuum former. Do vacuum forming as normal. Bingo - rapid prototyping without the need to create a model.

(Below: link to a vacuum former and a pin box toy for illustration)
-- gtoal, Feb 05 2021

pin array toy
pin array would look a little like this [gtoal, Feb 05 2021]

vacuum former
this style of vacuum former [gtoal, Feb 05 2021]

DYNAPIXEL: automated, reconfigurable molds
By means of a discretization of the tool surface with actuated pins, rapid prototypes or customer-specific components can be created without recurring tooling costs. [xaviergisz, Feb 06 2021]

1d: contour gauge
a 2d version of this...? [gtoal, Feb 10 2021]

similar to dynapixel but clunkier - with video...
rather chunky computer-controlled version [gtoal, Feb 10 2021]

As one who's done thermoforming in the real world, I can tell you that you'll have a hard time extracting the pinheads off of the plastic.
-- RayfordSteele, Feb 05 2021

The important thing is not to use too much force; just go and get a bigger hammer.
-- 8th of 7, Feb 05 2021

I use and teach the use of a vac former to Art students of all disciplines and the one thing that you can never do is use an object with undercuts. You can put it in, but once the plastic is sucked around the undercut, the object is captured and must be cut open to free it. Combining vac forming with rapid prototyping sounds like an interesting prospect, but to what advantage?
-- xenzag, Feb 06 2021

Well played, [xaviergisz].
-- pertinax, Feb 07 2021

Yep, that dynapixel sure looks like what I was thinking of. Well found.
-- gtoal, Feb 08 2021

Eh, you get a bun anyway. Clever idea.
-- doctorremulac3, Feb 08 2021

Actually the linked device (and others from this older idea 'Pin Matrix Terminal') are overkill compared to what I was suggesting - just a mechanical matrix like the toy, not a computer-controlled one... More a 2-dimensional version of a contour gauge.
-- gtoal, Feb 10 2021

random, halfbakery