Re: The Eighth Passenger
This is Awesome!!!
How did the Vacuum forming process go? Did it all form around your mould easily?? Did it need any persuasion???
Since our moulds are very similar in design & you've been able to get on with yours, I've been looking forward to this update
Hello Leigh,
Premise that this piece that Giger designed, is tremendous. :wacko
I think to make the original, have troubled a lot, that, in fact, in the scenes of the film and in the various images, it is always a bit 'ramshackle. For other people who have replicated the head of ALIEN, hiding the outline behind the tube, rather than above as in the original. In this way they avoid all the difficulties of the undercut of the dome.
For the vacuum, I brought the mold at a company that makes thermoformed. The material for the sheet to be thermoformed, I used the PETG, which is resistant to normal cans of acrylic paint and alcohol, which I use to airbrush and paint to clean up any mistakes. The slab of origin has a thickness of 5 mm to obtain a thickness of 3mm printed. The size of the sheets is 1.5 x 1 m.
The mold came out well, without fatigue or persuasion, but I think the die maker could pull more on the boundary, practicing more suction holes. I have to ask for confirmation of this question and then I will make you know.
However I think it is impossible, with a normal thermoforming, get the piece as in the original, with so much undercut. I think that the piece does not come out from the mold and you should cut without removing it from the mold. Leaving a deep groove in the mold, on the contour of the cut, so that the plastic does not reach that depth and it can be cut without damaging the mold. But this is just my idea never proven. So I chose a compromise between putting the dome in front of the tube, as in the original, but to limit the undercut, dividing it between the head and the dome.
The plaster mold is cracked in several places, probably because it was too hard. Fortunately he not scored too dome. The mold will be adjusted with filler, but I intend to do it again with a special resin charged aluminum, which probably allows casting in a mold made of fiberglass (Iam informing). This casting resin should have an exothermic peak of max 50 °, a processing time of between 2.5 and 3 hours, and a time of demoulding of 20-24 hours. This resin is made for thermoforming, because, unlike the plaster has superior mechanical characteristics and a lower cost than machined from solid metal.
For these reasons, I believe that your mold fiberglass can not resist the pressure, vacuum and temperature of the thermo-formed (130 °). I think you should follow my concept. You should build two half-shells on your mold, for casting in a resin and obtain the same form of your mold. But I think the critical point is that you also reduce undercuts, dividing them in half between the head and the dome. So change the molds of the head. Moreover, having to manually trim thermoformed, it is impossible to have a sharp coincidence of contours and will always require a minimum grouting.
You could try to make a plaster casting standard, which costs very little. This way you may see if the thermoformed out of the mold. But you still have to do at least two half-shells made of fiberglass.
It is a complicated big job! Why did a monster so complicated ?! :wacko