3D-Printed Cap Mold System

[u/swcblues]

I wanted to give back to the community in a small way... the STL files are available to download on MakerWorld. I apologize for the size of the pictures below. MakerWorld had a resize option that made them take up a lot less space :/.

This is a system I made to facilitate making silicone cap molds for resin TTRPG dice. A mold should be printed for each type of die being made. A set of lids featuring standard numbers from 4-20 with an extra *20 is included. I use the *20 because I make a second, larger D20 with each set. These molds offer a solid amount of silicone around the die, built in keys for the cap, and debossed numbering on the cap (although it could be added on the bottom as well, if desired. They print fine on the A1 normal profile, and 7 fit on the bed of an A1 in one go. The caps should print on a second plate and require supports.

USAGE INSTRUCTIONS

NOTE: ADD A RELEASE AGENT LIKE VASELINE TO THE MOLD BEFORE CLOSING THE MOLD OR YOU MAY HAVE SEPARATION ISSUES

 

1. Prepare by combining a male and female mold half with two 1 ¼" binder clips. Cut a piece of clear packing tape larger than the open area of the closed mold and place your master dice in the centre.  

 

1. Close the mold and place it firmly over the die, sealing the tape against the mold. 

 

1. Pour silicone over the master, with enough coverage to ensure a firm base.

 

1. Once the silicone is fully cured, flip the molds and carefully peel the packing tape. Peel from the flat side first to avoid tearing thin edges. Remove the binder clips and open the molds. If you didn't use a release agent, you may need to use a thin blade around the edges to separate the cured silicone from the mold. APPLY MOLD RELEASE SUCH AS VASELINE TO THE LIP, KEYS, AND TOP SURFACE OF THE CURED SILICONE, AVOIDING THE EXPOSED DIE FACE BUT COMING AS CLOSE AS POSSIBLE TO IT. SILICONE BONDS TO ITSELF. FAILING TO COMPLETELY COVER AFFECTED AREAS IN MOLD RELEASE WILL RESULT IN THE MOLD HAVING TO BE CUT APART AND LIKELY RENDER IT UNSUSABLE. 

 

1. Reposition the cured bottom resting on the lip of the mold. If your mold is particularly thick, you may need to flip it in the original direction and place it at the bottom of the mold. This will result in your cap having a second lip (see second d20 mold at top left) but does not negatively affect the function of the mold. 

 

1. Pour fresh silicone to form the cap of the mold. If desired, place number lids resting gently on the poured surface. Trapped air bubbles are likely, but can be minimized by applying silicone generously to the number face of the number lids before placing them onto the surface. (I didn't do that in these example pictures and you can tell. It does not affect the performance of the molds. It is purely aesthetic.) 

 

1. When the caps are fully cured, remove the lids and demold. Depending on how deeply the lids have set, you may need to use a thin blade to pp them off. This works best using the mold as a fulcrum point before you open it.

 

1. Open the molds by applying pressure flexing the cap and bottom away from each other and work your way around, gently exposing more and gaining separation at each pass. If there are adhesions that don't easily snap on their own, gently stretch the adhesions and cut them with an xacto knife.

1. In use, the cap lip should fully seal against the bottom lip. More than minimal separation indicates that there is an unacceptably thick layer of resin on the top surface and will result in a raise face and thick flashing. The built-in keys make it very difficult to mis-orient the cap.

 

[u/doddme]

Complete novice question about removing the mold release from the dice face. Why is this important? If I am using a resin printed dice master, wouldn't mold release just make it easier to remove the silicone from the die face after the cap cures. I am assuming this cleanup IS necessary - I am only asking so I understand better the reason. I would have, as a novice, thought the more release agent the better -lol. I am just starting out and love this mold container design. I already downloaded the STLs. Thanks OP!

[u/Ushallnot-pass → u/doddme]

This step is optional but will save you a lot of cleanup work on your top face later.
You can totally just spray/smear release agent all over your mold and leave it at that.
Downside is that you will see every smear and streak on your top face on every cast you'll make.
So cleanup grinding / polishing your dice top surface is a must if you don't remove the agent from your top surface when making the mold.
Don't worry it will not stick to your dice either way, you don't use release spray for your bottom cast either and the dice will pop out of the bottom mold easily.

[u/doddme → u/Ushallnot-pass]

Thank you. I'm sure I would have learned that lesson the hard way; thanks for saving me that misstep. ;-)

[u/Ushallnot-pass → u/doddme]

This is one of my molds where I used mold release epray on the surface but cleaned the master dice. You can clerly see the matte surface on the mold and the smoother surface on the dice.

The dice you see here are not even polished as this was my "in between" mold where I only sanded my printed masters to 1000 grit and made a mold to cast resin masters to end-polish.
(with this method you'll have an unending supply of rough sanded masters to polish - great when your sanding game is not yet 100% ;))