Finished The Eighth Passenger

Re: The Eighth Passenger

It all sounds pretty complicated :confused Thanks for the detailed reply :)

Looks like I've got my work cut out when I eventually get some time to get on with mine :unsure

...Or you could make a mold with the silicone rubber and casting a transparent resin? The difficult, would be to get a uniform thickness, because one side copy it with the rubber, but for the other side how would you do? Perhaps layering fiberglass and then sand the very finely, to get the other side with silicone rubber? There is a casting resin, flexible and durable?


I apologize, because I the wrong line of the mold division :wacko


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Re: The Eighth Passenger

I have put some thought into casting in clear resin & yes definitely doable but bubbles would be a major PITA.

I'd like to vac-form mine in 3mm polycarbonate, tough stuff! :)
 
Re: The Eighth Passenger

I have put some thought into casting in clear resin & yes definitely doable but bubbles would be a major PITA.

I'd like to vac-form mine in 3mm polycarbonate, tough stuff! :)

Hello Leigh,
I think you should change the section of your mold, from blue to red, because that as it is now, I am sure that the thermoformed absolutely can not get out from the mold.

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Re: The Eighth Passenger

Hey Guys, When i eventually do my dome i will be trying a negative form instead of the positive. Cavx gave me the idea you can see it on pg 2 of my thread. I'll basically am planning to do a 2 part fiberglass mould like you have done to make your positive.
STAMPO 1.jpg
you would need to have small holes around the under cuts and top of the dome to remove the air and have suction. i plan on using small pipes moulded into the fiberglass shell. you could then just separate the shell and avoid the undercut issue. i'm thinking of using silicone sealant on all the seams and flanges to get good suction.
Just thought i would share the idea to help out :)

Basic idea behind it:
fetch.png
Hello Leigh,
I think you should change the section of your mold, from blue to red, because that as it is now, I am sure that the thermoformed absolutely can not get out from the mold.

View attachment 559136
 
Re: The Eighth Passenger

Hey Guys, When i eventually do my dome i will be trying a negative form instead of the positive. Cavx gave me the idea you can see it on pg 2 of my thread. I'll basically am planning to do a 2 part fiberglass mould like you have done to make your positive.
View attachment 559151
you would need to have small holes around the under cuts and top of the dome to remove the air and have suction. i plan on using small pipes moulded into the fiberglass shell. you could then just separate the shell and avoid the undercut issue. i'm thinking of using silicone sealant on all the seams and flanges to get good suction.
Just thought i would share the idea to help out :)

Basic idea behind it:
View attachment 559152

Interesting! Not remain signs of mold separation?
 
Re: The Eighth Passenger

i'm planning on bolting the flanges together every 2 inches and also using silicone sealant so i don't think there would be separation issues.
 
Re: The Eighth Passenger

This what I've based mine on. What you can't see is if there are any holes drilled in the undercut? it worked for them though :)
 
Re: The Eighth Passenger

This what I've based mine on. What you can't see is if there are any holes drilled in the undercut? it worked for them though :)

What is seen is only that they managed to thermoformed, but no one knows how did they remove it from the mold.:confused:facepalm
 
Re: The Eighth Passenger

Years ago I read that that vacuum form had to be cut off the buck in sections. The undercuts were far too drastic that the back bottom and side undercuts were trimmed a little more flush to allow it to be removed from the buck.
It was from an Alien or Giger Art-book...I honestly dont remember which one but the article fascinated me back then because I was taking a plastics class in college.

David
 
Re: The Eighth Passenger

What is seen is only that they managed to thermoformed, but no one knows how did they remove it from the mold.:confused:facepalm

Brute force!! :D

I appreciate that mine wont come off easily & will most likely need to be cut while still on the mould but it absolutely has to have those undercuts! I'm thinking about knocking up my own vacuum forming table just for this as I have a feeling a company wont take on the job :$
 
Re: The Eighth Passenger

Brute force!! :D

I appreciate that mine wont come off easily & will most likely need to be cut while still on the mould but it absolutely has to have those undercuts! I'm thinking about knocking up my own vacuum forming table just for this as I have a feeling a company wont take on the job :$

It is right to pursue its objectives. :)

And, if I have not misunderstood, you do not accept the half results: or the dome is with all undercut that you have created, or leave your sculpture without dome. so it is?
 
Re: The Eighth Passenger

Could the buck be made in two halves? Cut down the middle, but with a wedge shaped part in the center on the underside. When the piece has been formed, turn it over pull out the wedge and the two halves should have room to be taken out.
 
Re: The Eighth Passenger

Could the buck be made in two halves? Cut down the middle, but with a wedge shaped part in the center on the underside. When the piece has been formed, turn it over pull out the wedge and the two halves should have room to be taken out.
I had thought. where there are separations,they remain impressions. and unfortunately this is not a piece that can be sanded,unless it is known a method to return to polish the plastic.
 
Re: The Eighth Passenger

Could the buck be made in two halves? Cut down the middle, but with a wedge shaped part in the center on the underside. When the piece has been formed, turn it over pull out the wedge and the two halves should have room to be taken out.

I thought of something like this when I was planning my buck (mould) but as DD says my concern would be leaving impressions in the form which would be difficult if not impossible to remove. I'm going to drill the row of small holes along the perimeter of mine & try it out using a thinner material than DD has used. I'm thinking 3mm Polycarbonate. It should stretch to leave 1mm thickness at the thinnest areas, it'll be strong (used on RC buggy body's) & hopefully flexible enough to go over the undercuts for removal. I expect it'll still put up a bit of a fight though :)

DD have you tried a thinner material?
 
Re: The Eighth Passenger

I thought of something like this when I was planning my buck (mould) but as DD says my concern would be leaving impressions in the form which would be difficult if not impossible to remove. I'm going to drill the row of small holes along the perimeter of mine & try it out using a thinner material than DD has used. I'm thinking 3mm Polycarbonate. It should stretch to leave 1mm thickness at the thinnest areas, it'll be strong (used on RC buggy body's) & hopefully flexible enough to go over the undercuts for removal. I expect it'll still put up a bit of a fight though :)

DD have you tried a thinner material?

For the first alien, they made the first printed with a departure of 3 mm sheet. I did not like, because in the upper part (where the material becomes thinner), was too soft (question of taste). But the extraction remained a problem. But I never tried to cut the piece, leaving the mold. If you build the machine vacuum, you can do all the tests you want, for both thicknesses, and for cutting. I still doubt if you can not damage the mold along the cutting line. You have to try and take risks. :)
 

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