3D printers print very, very slowly and the filament can be expensive. For this project, I printed a single prototype and used it to make a reusable silicone mold. The mold was used to make multiple heart-shaped boxes out of just a few cents-worth of concrete. 3D printers are still expensive, but strategies like this can result in the ability to make sellable products and can justify the expense. I modeled the box with FormZ and printed it on my 5th generation Makerbot Replicator. Then I used Mold Star 30 to make the silicone mold.

SUPPLIES:

Mold Star 30
I used Mold Star 30 to make the silicone mold.


Quikrete Countertop Mix
Available at Home Depot
I used Quikrete Countertop Mix in white to make the white box.





Quikrete 5000
Available at Home Depot
I used Quikrete 5000 to make the grey box.

TOOLS:

RYOBI 18 Volt Cordless Drill
Available at Home Depot






Box Cutter
Available at Home Depot

Diagonal Pliers
Available at The Home Depot

INSTRUCTIONS:

STEP 1: Print the Prototype
After modeling the heart-shaped box in FormZ, I printed it on my 5th generation Makerbot. I used the finest setting, so it took about 16 hours to print.



STEP 2: Make the Mold
I used a hot glue gun to glue both pieces of the prototype to the bottom of a plastic container.





STEP 3: Mix + Pour the Silicone
Mold Star 30 comes in two parts. I mixed them together and poured the mixture into the plastic container.







STEP 4: Remove the Prototype
Once the silicone cures, use diagonal pliers to remove the plastic container. The printed prototypes wouldn’t come out, so I had to make some cuts to get them free. I probably should have made molds with thinner walls so I could save silicone and make removal easier.









STEP 5: Pour Concrete
Rinse the molds with water and let them dry before mixing and pouring Quikrete Countertop Mix into them. Add water and stir until the concrete mixture is the consistency of oatmeal. Spoon and pour the concrete into the silicone molds. Tap and vibrate the molds to get out the air bubbles and to settle the wet concrete into all the corners.









STEP 6: Remove the Concrete
After letting the concrete cure about 20 hours I removed the box. The concrete was still fragile, so I had to make some additional cuts in the silicone to avoid breaking the box.







STEP 7: Modify the Mold for Production Runs
The silicone mold I made is reusable but I added quite a few cuts to it. I took another plastic container that was identical to the first and made a shell that held all the silicone pieces in place. Using my cordless drill, I drilled a series of holes and used diagonal pliers to clip the plastic in-between the holes. Creating holes in the plastic shell allows you to pour concrete through.









STEP 8: Pour Additional Boxes
I rinsed the molds to made sure there was no dust or concrete crumbs left in them and then mixed concrete for the second box. For the next box, I used Quikrete 5000 with the gravel picked out of it. The boxes are small and intricate, so I didn’t want the gravel to get stuck. I placed the plastic shell around the silicone molds, poured the concrete into it and vibrated the mold by tapping the sides with my hands to get out the air bubbles.



STEP 9: Remove the Second Box
This box was easier to remove since I had made additional cuts. Now I have a mold that can be use over and over again to produce heart-shaped boxes with.











Good luck making your own heart box and please email, tweet or hashtag photos to @benuyeda, ben@homemade-modern.com or #homemademodern. For more detailed instructions, dimensioned drawings and different variations of the project, check out our soon-to-be-released book.

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