MonsieurTox
Master Member
Great ! Thanks !
Molding and Casting Kit Parts for the Y-Wing Project
- Thread starter DaveG
- Start date
Thanks for all the additional tips and tricks! Sharing knowledge is good! Like I said, this is just my way of molding and casting, there is no 'wrong' way, as long as you get good results. And while I have invested in some fairly expensive molding and casting equipment over the years, you can get good results without, it's just might take a little bit more attention and you might have a few more rejects.
My methodologies are constantly evolving. Up until only recently, I was using white glue to stick the parts down like WINGINIT mentioned doing. In fact, several of the early kit parts molds on the Y-Project were done that way, glueing the parts down to an MDF baseboard with Elmers glue. But I use water clay to fill the recesses or undercut voids in some parts and the MDF would tend to absorb water from the clay and swell a little bit, sometimes popping the part up off the board while the mold rubber was curing, I needed to switch to the acrylic mold bases to cure this and white glue will stick, at least temporarily well enough to acrylic, but there was a tendency for parts to get bumped off the mark while the glue set, so I tried double stick tape, worked like a charm!
For years before I learned about the pressure tank casting method I got perfectly fine castings by, after pouring the resin into the mold, using a toothpick to softly run around the recesses knocking bubbles free before putting the backer mold plate down on top of the mold. As bubbles tend to stick in the same places each time you get to know the areas to concentrate on. This method works best with very low viscosity resins, like Alumilite.
My methodologies are constantly evolving. Up until only recently, I was using white glue to stick the parts down like WINGINIT mentioned doing. In fact, several of the early kit parts molds on the Y-Project were done that way, glueing the parts down to an MDF baseboard with Elmers glue. But I use water clay to fill the recesses or undercut voids in some parts and the MDF would tend to absorb water from the clay and swell a little bit, sometimes popping the part up off the board while the mold rubber was curing, I needed to switch to the acrylic mold bases to cure this and white glue will stick, at least temporarily well enough to acrylic, but there was a tendency for parts to get bumped off the mark while the glue set, so I tried double stick tape, worked like a charm!
For years before I learned about the pressure tank casting method I got perfectly fine castings by, after pouring the resin into the mold, using a toothpick to softly run around the recesses knocking bubbles free before putting the backer mold plate down on top of the mold. As bubbles tend to stick in the same places each time you get to know the areas to concentrate on. This method works best with very low viscosity resins, like Alumilite.
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Bigturc
Sr Member
ARCHIVE CASTING PLATE!!! This trick will save me tons .. TONS of time!! DaveG .. this information is priceless!! I can't say how impressed I am with some of the tricks shown here. That will help me a lot for some of the castings I'm doing!
This is what this forum should be about!
:thumbsup
This is what this forum should be about!
:thumbsup
Bigturc
Sr Member
And for those interested in saving all the information here, right click on the page, Save As... choose your folder and it will save all the text and images in a sub folder that you can reopen offline anytime you want!
I was asked for recommendations on casting resins by a member in a PM and thought I'd answer here as the information might be of interest to others.
I am currently using Silpak's Silcast II for casting shells, kit parts, prop parts, for pretty much everything. It's a great general purpose casting resin. Naturally white in color, I add some black tint to the bottle to make the parts grey. It's a little easier to see surface flaws in a grey part. It has a 3 minute pot life before it starts to set but you still need to work pretty fast to mix and pour. Silpak has a variety of other resins and I've tried most of them, settling on Silcast II as my favorite. It doesn't hurt that SilPak has an outlet not far from my Day Job and I can get there, pick up resin, grab a burger and get back during a lunch break! www.silpak.com
Alumi-Lite Regular (Tan) is another resin I like. Back in the "old days" it was my go-to resin for most things. It's thinner so it is a little easier to work out bubbles with a toothpick if you're not pressure casting. It does kick off faster so you've got to mix and pour really quickly, especially if you are mixing larger quantities or working in hot weather. I've found that even though it kicks off faster it can take longer than Silpak to fully cure in thin parts. The thinner the part the less heat generated by the cure and the slower the resin take to fully harden. Alumilite is stocked at many hobby and craft stores and you can order it through Amazon, in addition to their website. www.alumilite.com
Smooth-On is another popular line of casting resins. I've used some of their specialty resins but not their general purpose ones, though I've heard good things about them. The Smooth-Cast 300 looks like it has similar properties to the SilCast II and would work well for kit part and model part casting. Smooth-On products are sold through Reynolds Advanced Materials and they have 8 locations through out the U.S. and Canada, as well as being available online. www.reynoldsam.com
There are certainly other resins out there that will work well, I've just found ones I like and am use to, so there's not much need to go looking for others. There are probably very few resins to be avoided, al though some may have an objectionable oder.
It's a good idea to only buy the amount of resin you think you will use up in a couple of months. Urethane resin is 'hygroscopic' and absorbs moisture from the air once opened. After a while, this moisture will get to the point that is causes the resin to foam up ever so slightly ruining castings. If you live in a humid climate this will happen faster. Pressure casting can help to minimize this foaming if you are using a tank to cast. I like to pour resin from the larger container into smaller 16 ounce plastic bottles with a capable pour spout, helps the resin to last longer and makes the resin easier to pour and measure. Most of these resins are available in small and large kits. I typically by the large two gallon kits but even with all the casting i'm doing for the Y project it can take awhile to go through a set.
I've been asked about the "archive" nature of these resins. Unlike UV cured resins used for 3D printing, cast urethane parts should last pretty much indefinitely. Just look at the models from ANH, they still look pretty good, even after forty years. Extreme heat can cause parts to warp so don't leave models in the sun or in your car on a hot day.
Urethane resins can be used at pretty much any temperature you are comfortable working at, within reason. If extremely cold, they will take a long time to cure, if extremely hot, they can kick off much faster. While I don't have the cold problems here in Southern California, there are times during the hottest days of summer where my shop can be in the 90's or higher and large batches of resin can kick off before I get it poured. But I usually don't like to work under those conditions anyway...
Other notes... as I said in an earlier post, you can get good bubble-free casting without a pressure chamber, it's just take a bit more work and you might have more reject parts, particularly parts with very thin sections.
Roto Casting is not needed for most kit part and model casting. It really only becomes advantageous when you are trying to create hollow castings from closed molds. On the Y-wing project the only part's I've roto-cast were the L'Eggs engine nose cones. Those could have been done with two part molds and pressure casting instead but roto was the fastest way to crank out the quantity needed and the molds were a lot easier to make. Silpak and Smooth-On do make specialty resins for roto-casting but I've had fine results using good ol' SilCast II with a thixotropic powder added to thicken it up a bit and help it coat the sides of the rotating mold.
I am currently using Silpak's Silcast II for casting shells, kit parts, prop parts, for pretty much everything. It's a great general purpose casting resin. Naturally white in color, I add some black tint to the bottle to make the parts grey. It's a little easier to see surface flaws in a grey part. It has a 3 minute pot life before it starts to set but you still need to work pretty fast to mix and pour. Silpak has a variety of other resins and I've tried most of them, settling on Silcast II as my favorite. It doesn't hurt that SilPak has an outlet not far from my Day Job and I can get there, pick up resin, grab a burger and get back during a lunch break! www.silpak.com
Alumi-Lite Regular (Tan) is another resin I like. Back in the "old days" it was my go-to resin for most things. It's thinner so it is a little easier to work out bubbles with a toothpick if you're not pressure casting. It does kick off faster so you've got to mix and pour really quickly, especially if you are mixing larger quantities or working in hot weather. I've found that even though it kicks off faster it can take longer than Silpak to fully cure in thin parts. The thinner the part the less heat generated by the cure and the slower the resin take to fully harden. Alumilite is stocked at many hobby and craft stores and you can order it through Amazon, in addition to their website. www.alumilite.com
Smooth-On is another popular line of casting resins. I've used some of their specialty resins but not their general purpose ones, though I've heard good things about them. The Smooth-Cast 300 looks like it has similar properties to the SilCast II and would work well for kit part and model part casting. Smooth-On products are sold through Reynolds Advanced Materials and they have 8 locations through out the U.S. and Canada, as well as being available online. www.reynoldsam.com
There are certainly other resins out there that will work well, I've just found ones I like and am use to, so there's not much need to go looking for others. There are probably very few resins to be avoided, al though some may have an objectionable oder.
It's a good idea to only buy the amount of resin you think you will use up in a couple of months. Urethane resin is 'hygroscopic' and absorbs moisture from the air once opened. After a while, this moisture will get to the point that is causes the resin to foam up ever so slightly ruining castings. If you live in a humid climate this will happen faster. Pressure casting can help to minimize this foaming if you are using a tank to cast. I like to pour resin from the larger container into smaller 16 ounce plastic bottles with a capable pour spout, helps the resin to last longer and makes the resin easier to pour and measure. Most of these resins are available in small and large kits. I typically by the large two gallon kits but even with all the casting i'm doing for the Y project it can take awhile to go through a set.
I've been asked about the "archive" nature of these resins. Unlike UV cured resins used for 3D printing, cast urethane parts should last pretty much indefinitely. Just look at the models from ANH, they still look pretty good, even after forty years. Extreme heat can cause parts to warp so don't leave models in the sun or in your car on a hot day.
Urethane resins can be used at pretty much any temperature you are comfortable working at, within reason. If extremely cold, they will take a long time to cure, if extremely hot, they can kick off much faster. While I don't have the cold problems here in Southern California, there are times during the hottest days of summer where my shop can be in the 90's or higher and large batches of resin can kick off before I get it poured. But I usually don't like to work under those conditions anyway...
Other notes... as I said in an earlier post, you can get good bubble-free casting without a pressure chamber, it's just take a bit more work and you might have more reject parts, particularly parts with very thin sections.
Roto Casting is not needed for most kit part and model casting. It really only becomes advantageous when you are trying to create hollow castings from closed molds. On the Y-wing project the only part's I've roto-cast were the L'Eggs engine nose cones. Those could have been done with two part molds and pressure casting instead but roto was the fastest way to crank out the quantity needed and the molds were a lot easier to make. Silpak and Smooth-On do make specialty resins for roto-casting but I've had fine results using good ol' SilCast II with a thixotropic powder added to thicken it up a bit and help it coat the sides of the rotating mold.
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I've been using Silcast II for a few years on the recommendation of a Silpak employee in there La Verne facility. I've never used anything else. My only complaint is that it can be a little on the brittle side at times, especially with thin pieces. As you said the white color will give you a false sense of uncrisp detail until you paint it.
Guns Akimbo
Sr Member
This thread is perfect for me timing-wise, because I'm shopping for a degassing chamber right now. Making one vs. buying retail, and advantages/disadvantages for one over the other? Thanks for taking the time to post this in-depth tutorial!
The first thing to say about vacuum chambers is to NEVER under estimate the power of a vacuum! You do not want to be around a chamber when it implodes, I speak from experience here. My first DIY chamber imploded because I didn't know what I was doing. I was standing only two feet away from it and was lucky to have not sustained any injuries. A real "brown stain moment" if you know what I mean!:eek
Some people have made pretty good vacuum chambers from heavy duty professional kitchen stock pots, the kind that are made from 1/4" thick aluminum, and a Lexan (polycarbonate) cover. I recommend a 3/4" or 1" thick polycarbonate cover over acrylic. Less likely to break or shatter. www.bestvaluevacs.com sells these kind of chambers. I've not had any direct experience with their products but that look pretty good and are reasonably priced.
For a vacuum pump you must get one that can pull a vacuum of 29 inches of mercury, or else you're wasting your money. Many cheap pumps that you'll find on EBay won't pull that high.
Good luck!
Some people have made pretty good vacuum chambers from heavy duty professional kitchen stock pots, the kind that are made from 1/4" thick aluminum, and a Lexan (polycarbonate) cover. I recommend a 3/4" or 1" thick polycarbonate cover over acrylic. Less likely to break or shatter. www.bestvaluevacs.com sells these kind of chambers. I've not had any direct experience with their products but that look pretty good and are reasonably priced.
For a vacuum pump you must get one that can pull a vacuum of 29 inches of mercury, or else you're wasting your money. Many cheap pumps that you'll find on EBay won't pull that high.
Good luck!
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navajo bro
New Member
This is great! I've been making costumes for 10 years or so and have decided to start looking into making my own molds for some props, greeblies and bits. I'm chiming in here so I can find this later, as I have some questions and def want to re-read your tutorial man!!
A little addition about keeping resin from absorbing moisture while in storage:
There are several "air displacement" products that come in spray paint-like cans. One I have used is called "Burp", but there are others. I'm not sure what is in them, but they push out the moisture-laden ambient air with a dry air ( maybe straight nitrogen or CO2? ). You spray it into the jug of resin before sealing it for storage. This will allow you to store your resins longer, as they are sealed well.
There are several "air displacement" products that come in spray paint-like cans. One I have used is called "Burp", but there are others. I'm not sure what is in them, but they push out the moisture-laden ambient air with a dry air ( maybe straight nitrogen or CO2? ). You spray it into the jug of resin before sealing it for storage. This will allow you to store your resins longer, as they are sealed well.
navajo bro
New Member
Figured I'd ask here first, I'm still searching as well.
What are the best places to get silicone rubber casting itself? The only thing I can find here in NJ storewise are places like Hobby Lobby or A.C. Moore, and they only offer small little project type kits. For example, I have created a clay mold of a 10"x4"x4" spike, so math tells me I'll have about 160 cubic inches to fill in the mold box I'll make. If I'm correct it takes about 1lb of silicone rubber to fill 21 cubic inches so I'll need around 8lbs? Rather then buy 16 boxes of the small 1/2 lb bottles at these stores is there a good site to get it in larger quantities?
I'm looking at something like this in the gallon size:
http://specialtyresin.com/silicones.html?gclid=CP-TxJDe9M4CFUxbhgodC_gJgQ
Again, sorry for the newbie question but I'm still learning the differences on types and brands for what I need. I want to create a rubber mold of the clay spike, then cast it in plastic or resin (which I think I have figured out).
What are the best places to get silicone rubber casting itself? The only thing I can find here in NJ storewise are places like Hobby Lobby or A.C. Moore, and they only offer small little project type kits. For example, I have created a clay mold of a 10"x4"x4" spike, so math tells me I'll have about 160 cubic inches to fill in the mold box I'll make. If I'm correct it takes about 1lb of silicone rubber to fill 21 cubic inches so I'll need around 8lbs? Rather then buy 16 boxes of the small 1/2 lb bottles at these stores is there a good site to get it in larger quantities?
I'm looking at something like this in the gallon size:
http://specialtyresin.com/silicones.html?gclid=CP-TxJDe9M4CFUxbhgodC_gJgQ
Again, sorry for the newbie question but I'm still learning the differences on types and brands for what I need. I want to create a rubber mold of the clay spike, then cast it in plastic or resin (which I think I have figured out).
Terry, no worries. These materials can be hard to find locally. Check out www.reynoldsam.com they make the Smooth-On line of products and all are available on-line. There's a lot of good information for newbies on their website. There's also Silpak.com, I use their materials almost exclusively, but their website isn't as user friendly. It assumes you already know what you're doing.
navajo bro
New Member
and Ladies and Gentleman.. that's exactly how its done. Great work Dave.
Terry, I've used RTV silicone from Hobby Silicone, Aeromarine, Raw Material Suppliers and Specialty Resin (the one you linked) and the rubber from Specialty Resin has been the most resistant to breaking down over time.
Molds will begin to dry out and "fray" with use, with little pieces flaking off as you do repeated castings. All the above rubbers have performed well in my work...but the one from SR has been a clear winner in the longevity race. I use both talc to aid in bubble reduction and Stoner's Rocket Release to help preserve the molds.
Just my .02
Molds will begin to dry out and "fray" with use, with little pieces flaking off as you do repeated castings. All the above rubbers have performed well in my work...but the one from SR has been a clear winner in the longevity race. I use both talc to aid in bubble reduction and Stoner's Rocket Release to help preserve the molds.
Just my .02
navajo bro
New Member
That's awesome man thanks! I believe I'm on the right track, I'll have to start my own thread as I'm getting started
