Thanks, as always, for the the kind words and positive feedback. It's the reception as a whole that I've been getting from the community that has really fueled me to try to push my work to the next level and see if a studio can actually become real. I've found such an enjoyment out of it all that I really want to make this a livelihood; my choice to start studying for a bachelors degree in Industrial Design is in no small part due to my obsession with creating and building for this hobby.
~ 2-Part Mould Making ~ Part 2
After 7+ hours of curing under 50+PSI of pressure the rubber as close to perfect as you can get.
Now that the RTV rubber is solid and locked in place it's as easy as flipping the Mould Box and peeling the Plasticine away. Sometimes the pressure has a way of forcing rubber under the piece in a few places, but that can be cleaned up; I'll show some of that next...
After removing the Plasticine it's time for some cleanup.
It's not uncommon for the odd seam to leak a little. The rubber gets thick enough to stop flowing in the first hour or so in the Pressure Chamber, so it's not enough to be a problem but it needs to be cleaned up at this point. Note: If you are not careful handling your mould boxes you can break the seal it has with the Plasticine. This can cause a large enough leak that will let much more of the rubber ooze out before curing.
Also, a few spots usually get a bit of rubber forced under by the pressure. It's usually a thin film that can be easily trimmed away. A fresh #11 scalpel blade is my go to favorite for this job, but it's my favorite blade for almost everything. Carefully cut along the edge of the object and use a set of tweezers to pick and peel away the unwanted rubber.
After cleanup it's a simple matter of building up the Lego to create a box for the second half of the mould.
With the walls built up there are two final steps before pouring the second half of the mould. First, input/output gates need to be attached to the sprew. These will pass right through the second half of the mould that is about to be poured. Once they're glued in place the entire cavity is sprayed liberally with some Mould Release. Be sure to spray the rubber areas well; note enough Mould Release will make the two halves of the mould stick together, and very hard to split apart.
Just like the first half of the mould, an even smooth pour starting in one corner is all that's needed.
Just like before, once I have the moulds poured I stack them up before returning them to the Pressure Chamber for the second high pressure curing.
Now it’s time to dismantle the Lego Mould Box and reveal the newly completed mould.
As Lego blocks are pulled away each of the seams will leave thin flash. It likes to stick to the Lego, but it peels away very easily; it’s just a bit fiddly and annoying, really. Once all of the Lego is gone it’s simple to pick this flash away by hand.
Now the Prototype needs to be freed from the new 2-Part Mould.
The Mould Release spray used earlier will help the two parts split apart. The Pins can be a bit stubborn at this point, as they each pop free for the first time. Working slowly around the part you can open the entire seam. From there just peel the mould open.
A press on the Inlet/Outlet Gates should push the Prototype away from the mould.
Slip the Prototype free and the mould is ready to use. With the pressure during curing, the RTV rubber has been formed flawlessly. Even the shine left from the glue I used during the build can be seen in the mould surface - amazing.
Now, since I created this article I’ve done many more moulds (most successful, several others… not so much
) And I figured it would be a good spot to show how this method can be taken to do larger and more complex objects. Plasticine is an excellent base and temporary filler and it can be used suspend complex objects.
It’s all in the layering; build a base slab, and place your prototypes on shelves made from plasticine.
It takes some practice, and a willingness to cut certain slabs several times until the correct shape is achieved; but fitting the object like this will let you completely control where the mould split will be. In this case I get it along the outside edge where it will be very easy to clean. Any major overhangs that could grab at the second half of the mould are filled with plasticine, and will be removed and cleaned in the next step. Getting the seal of the component to the plasticine is the trickiest part at this point. A little Mould Release brushed on along the seam can help. Getting it as clean as possible will make for clean mould lines that are easier to remove from the final resin casts.
After pouring and curing the first half, just like the simpler flat-back mould, remove the plasticine and clean things up.
Building the plasticine up is more complex in this case, but taking it out is the same principle. Getting the ‘stump’ of plasticine out can be a bit of a pin, but once it starts it usually rolls out as pictured. Traces of plasticine in nooks-and-crannies can be cleaned out with rubbing alcohol and/or Mould Release. As before, some rubber will get forced under the parts in a few places, they will need to be cleaned up. Beyond that, the Mould Box is built up again, injection vents are added, everything is sprayed with Mould Release, and the parts are ready for the pouring of the second half of this mould.
De-moulding parts from moulds like this becomes more difficult; shapes like these like to bent and warp as you try to free it from the mould. So just how complex they can get is somewhat limited, but they can easily be large enough for most war-gaming model needs.
So, that's it for now. Any questions, comments, ideas, or other general musings are always welcome.
Up next... I have no idea... But I'm sure I'll come up with a little something.
Thanks for reading.
~ 2-Part Mould Making ~ Part 2

After 7+ hours of curing under 50+PSI of pressure the rubber as close to perfect as you can get.
Now that the RTV rubber is solid and locked in place it's as easy as flipping the Mould Box and peeling the Plasticine away. Sometimes the pressure has a way of forcing rubber under the piece in a few places, but that can be cleaned up; I'll show some of that next...

After removing the Plasticine it's time for some cleanup.
It's not uncommon for the odd seam to leak a little. The rubber gets thick enough to stop flowing in the first hour or so in the Pressure Chamber, so it's not enough to be a problem but it needs to be cleaned up at this point. Note: If you are not careful handling your mould boxes you can break the seal it has with the Plasticine. This can cause a large enough leak that will let much more of the rubber ooze out before curing.
Also, a few spots usually get a bit of rubber forced under by the pressure. It's usually a thin film that can be easily trimmed away. A fresh #11 scalpel blade is my go to favorite for this job, but it's my favorite blade for almost everything. Carefully cut along the edge of the object and use a set of tweezers to pick and peel away the unwanted rubber.

After cleanup it's a simple matter of building up the Lego to create a box for the second half of the mould.
With the walls built up there are two final steps before pouring the second half of the mould. First, input/output gates need to be attached to the sprew. These will pass right through the second half of the mould that is about to be poured. Once they're glued in place the entire cavity is sprayed liberally with some Mould Release. Be sure to spray the rubber areas well; note enough Mould Release will make the two halves of the mould stick together, and very hard to split apart.

Just like the first half of the mould, an even smooth pour starting in one corner is all that's needed.
Just like before, once I have the moulds poured I stack them up before returning them to the Pressure Chamber for the second high pressure curing.

Now it’s time to dismantle the Lego Mould Box and reveal the newly completed mould.
As Lego blocks are pulled away each of the seams will leave thin flash. It likes to stick to the Lego, but it peels away very easily; it’s just a bit fiddly and annoying, really. Once all of the Lego is gone it’s simple to pick this flash away by hand.

Now the Prototype needs to be freed from the new 2-Part Mould.
The Mould Release spray used earlier will help the two parts split apart. The Pins can be a bit stubborn at this point, as they each pop free for the first time. Working slowly around the part you can open the entire seam. From there just peel the mould open.

A press on the Inlet/Outlet Gates should push the Prototype away from the mould.
Slip the Prototype free and the mould is ready to use. With the pressure during curing, the RTV rubber has been formed flawlessly. Even the shine left from the glue I used during the build can be seen in the mould surface - amazing.
Now, since I created this article I’ve done many more moulds (most successful, several others… not so much


It’s all in the layering; build a base slab, and place your prototypes on shelves made from plasticine.
It takes some practice, and a willingness to cut certain slabs several times until the correct shape is achieved; but fitting the object like this will let you completely control where the mould split will be. In this case I get it along the outside edge where it will be very easy to clean. Any major overhangs that could grab at the second half of the mould are filled with plasticine, and will be removed and cleaned in the next step. Getting the seal of the component to the plasticine is the trickiest part at this point. A little Mould Release brushed on along the seam can help. Getting it as clean as possible will make for clean mould lines that are easier to remove from the final resin casts.

After pouring and curing the first half, just like the simpler flat-back mould, remove the plasticine and clean things up.
Building the plasticine up is more complex in this case, but taking it out is the same principle. Getting the ‘stump’ of plasticine out can be a bit of a pin, but once it starts it usually rolls out as pictured. Traces of plasticine in nooks-and-crannies can be cleaned out with rubbing alcohol and/or Mould Release. As before, some rubber will get forced under the parts in a few places, they will need to be cleaned up. Beyond that, the Mould Box is built up again, injection vents are added, everything is sprayed with Mould Release, and the parts are ready for the pouring of the second half of this mould.
De-moulding parts from moulds like this becomes more difficult; shapes like these like to bent and warp as you try to free it from the mould. So just how complex they can get is somewhat limited, but they can easily be large enough for most war-gaming model needs.
So, that's it for now. Any questions, comments, ideas, or other general musings are always welcome.
Up next... I have no idea... But I'm sure I'll come up with a little something.
Thanks for reading.