Scale Brake Light Cover's (split molding) -- Custom Miniature Models and R/C

Miniature Brake Light Len’s Covers (2-part molding)

by:   Lonnie Sexton

This is a tutorial on molding and casting miniature/scale brake light lens covers. I made these for a 1/10^th scale replica remote control Earth Roamer XV-LT. They are molded to fit the custom 1/10^th scale brazed brass rear bumper and ER shell. More details on the entire XV-LT RC build and the bottom.

Parts/Tools:

Amazing Mold Putty - Link

Amazing Clear Casting Resin - Link

Red Dye - Link

Mixing Cup - Link - (a few are included with the clear cast.)

Mixing Stick - Link – (a few are included with the clear cast.)

Mold Release 

Poster Board

Styrene Sheets .30” think - Link
Green Putty
MEK – Styrene Bonder
Masking Tape
Wood / Styrene Rods (dowels) ¼” dia.
Hot Glue Gun
Box Knife (razor for cutting poster board)
Xacto Knife
Ruler
Sharpie
Vacuum Chamber (DYI Vacuum Chamber)
Scale – - Link

Steps:

1. Create Primary Object
2. Prepare the Part for molding
3. Make the mold box
4. Prep for Bottom ½
5. Press Bottom Half – wait for cure
6. Apply Mold Release and Press Top Half –wait for cure
7. Casting and Vacuum
8. Final Prep

Creating the primary object

The primary can be made out of any material. I used basswood to create the primary which gave the finished parts a grain texture. I recommend styrene for creating your primary objects, if you want a smooth surface.

Preparing the part for molding

Prepare the surface of the primary; any sanding, filling, texturing etc. should be done before molding.

Make the mold box

The basic rule to a mold box is it should be 2x the height of your part and .25 - .50” wall around the edges. (if you plan on reusing the mold many times). You can get away with a thinner wall with AMP, but a few extra grams of putty goes a long way.

Lay the primary down on a piece of poster board. Mark and Measure the size of the base. Cut out the parts and Hot Glue the Mold Box together. You can use duct tape or packing tape to hold the box together. I prefer hot glue for large molds.

Prep for Bottom ½

The Styrene or wood dowels are used to create the casting resin and air inlets. They will be pressed into the AMP between the wall of the box and primary object. Place the primary in the box, measure and cut the dowels. Set aside.

Pressing the Bottom

Weight and mix the proper amount of AMP part A and B. It’s important to get them equal. A digital scale is useful.

Press the AMP into the box and flatten it out as best as possible. Align the Part in the box where your pre-cut inlets will fit and press the part firmly into the box. Press the Inlets into place and Finesse the AMP around the edges of the primary. Try to avoid and overlapping of the part. If needed only press the primary partially into the bottom ½ to avoid unwanted undercuts.

I always press alignment dimples into the corners so the half’s line up better.

Let the AMP cure.

Apply Mold Release and Press Top Half

After the bottom is cured, lightly mist the amp and part with mold release.

Mix the AMP and Press it into the top of the box. Working it down into any edges to avoid air pockets and finesse is flat. Scratch a part name or number if you wish.

De-molding and Mold Finishing

Separate the mold carefully. Remove the primary object and trim the inlets.

Casting and Vacuum

I recommend making multiple molds for parts that are dyed and/or needing more than 1. It’s hard to get a consistent color when mixing and casting from 1 mold. I made 6 red Brake light covers and 2 rev light (clear).

Secure the mold together with rubber tough rubber bands. Make inlet funnels with some paper of old business cards (crafting tip: business cards make great crafting disposables. Funnels, mixing, spreading filler, etc.)

Mix the Casting and Dye per instructions, then pour into the funnel until you see it pop out the other hole. Make sure there is enough casting material in the funnel to fill the space the air bubbles take up.

Place in Vacuum chamber, pull a vacuum for aprox 10-15 sec, then release vacuum pressure and let the parts cure.

  

Final Prep

Seperate the mold and remove the parts. Trim the inlet “flash”.

Installed in brace.

Amazing Install!

If you want to see the entire 5 year build unfold part for part, visit the forums on; Scale 4x4rc.org or come back here to see all the parts made with AMP. Link

Please come back and join us for more exciting projects and tutorials.
Coming soon:
*Scale Earth Roamer Windows
*DYI Vacuum Chamber
*Styrene Ninja - Road to Plastic Master
*10th Scale Pin-Ball Machine