Hey guys,
I make Ghostbusters props and one of the props I make is the PKE meter from the Real Ghosbtusters cartoon:
As you can see, this one is built from wood. And that's fine, it's nice and sturdy... but mass producing them is a pain in the butt.
To alleviate this issue, I've decided to start molding the body and cowl from resin. And to this end, and to make sure I get it right the first time, I've been doing research on the various silicones and resins that are available, and watching tutorials on youtube to learn the best technique.
Initially, I'd been looking at Smooth-On's Oomoo to make my molds, because the speed at which it sets and the fact that you don't need to degass it were appealing to me. (I don't have a vaccuum chamber, and I live in an apartment, so if my mold has to set in a well ventilated area, it will have to sit outside.) However, I have since seen a youtube video where a fellow easily snapped an inch thick Oomoo mold in two, but head great difficulty tearing a thin piece of Mold Max 30 apart... so I've decided to go for the Mold Max 30, which I believe is what folks generally reccomend for mold making anyway.
As for resin, I've been looking at Smooth On's 300 series white liquid plastic. I want a fairly hard plastic which won't break easily if dropped or crack when drilled, so I know I want a urethane, and I think this is a good hardness, though I'm not entirely certain. I haven't yet found any videos of people knocking it around a bit.
Here's links to those two products btw:
http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1135/index.html
http://www.smooth-on.com/Urethane-Plastic-a/c5_1120_1209/index.html
Anyway, now that you know what materials I intend to work with, here's my problem:
That PKE meter you see there will need to be built using several two part molds. The interior needs to be hollow, and the top needs to be removable. So to build the main body, I will have one mold for the base, one for the cover, one for the cowl around the screen, and one for the handle. (Unless I decide to mold the handle as one solid part of the base, which I suppose I could do.)
The issue I am concerned about is that base, and the cowl. The walls of the base will be 1/8" thick, while the cowl's walls are only 1/16". I don't know how thick the resin I've chosen will be, but I am worried that if I put a pour hole and vent at the top of that PKE body, that the resin won't flow up both sides and over the top.
The way I intend to construct the mold is to lay the shell of the PKE flat on its back, embed it half in clay, put pour and vent holes at the top of the screen, then pour one half of the mold over and into the body to create the void inside, then flip it over after to pour the second half of the mold which will form the details on the back and the other half of of the sides.
Do you see any problem with this? Will I end up with tons of bubbles in my final casting? Is there anyhting I can do to help prevent this without spending a lot of money on an expensive pressure chamber I can't afford?
I'm not worried so much about bubbles in the mold itself, since the silicone won't have to flow through any tight spaces and I should be okay if I pour it from a great height into the lowest spot of the mold. It's the resin I'm worried about, and all three of the molds I need to make for this will have fairly thin areas the resin needs to flow through.
I make Ghostbusters props and one of the props I make is the PKE meter from the Real Ghosbtusters cartoon:
As you can see, this one is built from wood. And that's fine, it's nice and sturdy... but mass producing them is a pain in the butt.
To alleviate this issue, I've decided to start molding the body and cowl from resin. And to this end, and to make sure I get it right the first time, I've been doing research on the various silicones and resins that are available, and watching tutorials on youtube to learn the best technique.
Initially, I'd been looking at Smooth-On's Oomoo to make my molds, because the speed at which it sets and the fact that you don't need to degass it were appealing to me. (I don't have a vaccuum chamber, and I live in an apartment, so if my mold has to set in a well ventilated area, it will have to sit outside.) However, I have since seen a youtube video where a fellow easily snapped an inch thick Oomoo mold in two, but head great difficulty tearing a thin piece of Mold Max 30 apart... so I've decided to go for the Mold Max 30, which I believe is what folks generally reccomend for mold making anyway.
As for resin, I've been looking at Smooth On's 300 series white liquid plastic. I want a fairly hard plastic which won't break easily if dropped or crack when drilled, so I know I want a urethane, and I think this is a good hardness, though I'm not entirely certain. I haven't yet found any videos of people knocking it around a bit.
Here's links to those two products btw:
http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1135/index.html
http://www.smooth-on.com/Urethane-Plastic-a/c5_1120_1209/index.html
Anyway, now that you know what materials I intend to work with, here's my problem:
That PKE meter you see there will need to be built using several two part molds. The interior needs to be hollow, and the top needs to be removable. So to build the main body, I will have one mold for the base, one for the cover, one for the cowl around the screen, and one for the handle. (Unless I decide to mold the handle as one solid part of the base, which I suppose I could do.)
The issue I am concerned about is that base, and the cowl. The walls of the base will be 1/8" thick, while the cowl's walls are only 1/16". I don't know how thick the resin I've chosen will be, but I am worried that if I put a pour hole and vent at the top of that PKE body, that the resin won't flow up both sides and over the top.
The way I intend to construct the mold is to lay the shell of the PKE flat on its back, embed it half in clay, put pour and vent holes at the top of the screen, then pour one half of the mold over and into the body to create the void inside, then flip it over after to pour the second half of the mold which will form the details on the back and the other half of of the sides.
Do you see any problem with this? Will I end up with tons of bubbles in my final casting? Is there anyhting I can do to help prevent this without spending a lot of money on an expensive pressure chamber I can't afford?
I'm not worried so much about bubbles in the mold itself, since the silicone won't have to flow through any tight spaces and I should be okay if I pour it from a great height into the lowest spot of the mold. It's the resin I'm worried about, and all three of the molds I need to make for this will have fairly thin areas the resin needs to flow through.
