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How to Make a 2-Piece Core Mold: Concrete Urn Example
Simplifying An Advanced Mold Making Application
This gallery outlines the steps for creating a two-piece cored mold using
urethane rubber from Smooth-On.
1 - Our model is a detailed urn made of concrete.
2 - Urn is measured for dimensions.
3 - Acrylic coated boards are cut to size.
4 - Mold box walls will follow the contour of the model.
5 - Construct mold box and secure with drywall screws.
6 - Two handles are attached to mold box to make handling easier.
7 - Use a black marker to mark inside edge of mold box to define clay bed perimeter.
8 - Remove mold box to expose perimeter line.
9 - Form a 3/4'' (2 cm) thick clay bed inside marked area.
10 - Place mold box over clay bed.
11 - Fill any voids with additional clay.
12 - Use a rolling pin to smooth out clay bed.
13 - Smooth beveled edge around perimeter.
14 - Drill vent hole: Allows air to escape during mold making process.
15 - Make a clay gasket around perimeter.
16 - Center urn on clay bed.
17 - Firmly push urn into clay bed.
18 - Registration key is cut into clay bed with large paper clip.
19 - Overhead view showing registration key in clay bed.
20 - Apply Superseal® sealing agent to urn surface.
21 - Apply Universal® Mold Release to mold box and urn.
22 - Place mold box over urn.
23 - Seal seams with hot melt glue.
24 - Dispense ReoFlex® 40 mold rubber 1A to 1 B by volume.
25 - Mix thoroughly for three minutes, scraping bottom and sides of container.
26 - Pour rubber into cavity and let mold rubber cure for 16 hours at room temperature (72F / 23C).
27 - DO NOT COVER BOTTOM OF ORIGINAL MODEL. Exposed area will represent pour spout.
28 - Next day, flip over mold box.
29 - Slowly remove baseboard.
30 - Remove rubber flashing.
31 - Carve notch into rubber with a knife for registration.
32 - Inside the mold box is marked to identify registration point.
33 - Apply Superseal® sealing agent to the inside of the urn.
34 - Apply Universal® Mold Release to mold box and urn.
35 - Clean modeling clay off baseboard. Once cleaned this will be used for the core section base.
36 - MAKING THE CORE SECTION. Place a plastic container on the center of baseboard and mark outline.
37 - Drill four 1'' (2.5 cm) holes. This is where the mold rubber will be poured to make the second half.
38 - 1/4'' (6mm) vent holes will be drilled in highlighted areas.
39 - Vent holes will minimize air bubbles in cured rubber.
40 - Hot melt glue is used to adhere plastic container to center of board.
41 - Hold in place for ten seconds.
42 - Place core section into mold caviity. Alignment point is marked on the outside of base and mold box.
43 - Adhere core section with drywall screws.
44 - Use modeling clay to seal seams.
45 - Dispense ReoFlex® 40 mold rubber 1A to 1 B by volume.
46 - Mix thoroughly for three minutes, scraping bottom and sides of container.
47 - Pour rubber into cavity.
48 - Let mold rubber cure for 16 hours at room temperature (72F / 23C).
49 - Remove drywall screws and slowly lift-up core section.
50 - Remove mold box.
51 - A sharp knife is used to extract the original model.
52 - Mold reflects perfect detail captured from the original model.
53 - Apply Ease Release 2831 to all rubber surfaces.
54 - Use alignment point to help assemble mold for casting.
55 - Reproduction will be made with duoMatrix® NEO (Polymer Modifed Gypsum). Mix ratio 2 Parts A to 1 Part B by volume.
56 - One part play sand will be added for addional texture.
57 - Mix all components thoroughly for three minutes, scraping bottom and sides of container.
58 - Add So-Strong® Brown pigment to mix for color.
59 - Pour Matrix NEO slowly into cavity.
60 - After Matrix® NEO cures for 90 minutes remove mold box.
61 - Demold casting from the rubber mold.
62 - Perfectly detailed reproduction of the original model.
63 - Add color to the casting with brown wood stain.
64 - Wipe-off any extra stain with soft towel.
65 - Rubber mold is ready for production casting.
66 - Different finishes can be achieved by varying color, tints and stain.
Simplifying An Advanced Mold Making Application; Making Your Own 2-Piece Core Mold Of A Concrete Urn
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