Molding a Biomaterial Button

In this class we learned about the different techniques to fabricate a mold and various recipes of bio-based materials. This built upon the Material Intelligence 01 and 02 classes this term.

For our interactive A/V installation we are fabricating biomaterial interfaces. The mold was 3D printed in an Ender 3 Pro. The STL files can be found here.

The 3D-printed mold (manufactured in an Ender 3 Pro).

Recipe

Agar Agar :4g
Water: 80 ml
Glycerin: 15 ml

Our key ingredients: Agar Agar (left) and Glycerin (right).

Process & Observation

To produce, mix everything together while its cold and heat it in glass container for 1.30 minutes in a microwave. Pour while hot.

The Resulting biomaterial takes about 4-5 days to dry completely, assuming a mold thickness of max 2cm. It is wet to the touch at first and prone to deformation after exerting slight pressure. It shrinks about 25% during the resulting drying process and changes from slightly  milky transparent texture to a yellowish opaque appearance . To reduce the shrinkage and control the shrinking dimensions a bit better, we added two pins in the mold that are meant to fixate the mass in place during the drying process.

Mixing the recipe.

Pouring the mixed biomaterial after heating.

The outcome after 2h of drying. As it can be seen, the drying process should be continued to preserve the form and avoid deformations by touch.

Further Links

Molding and Casting

molding
  types
     injection (sprue, runner, gate, vent, parting line, flashing)
     insert, overmolding
     vacuum
     blow
     rototional
     vacuum, pressure assisted
     die, investment casting
     flexible, soft, short-run production
     mold, parts, frame, registration video
  vendors
     Smooth-On
     Reynolds Advanced Materials
     Dick Blick
     West Marine
     USG
     Chockfast
     Aremco
     Protolabs
  materials
     low-temp wax
     machineable wax DIY
     rigid foam
        gesso, epoxy, shrink wrap, hot air
     wood
     alginate gel
     urethane rubber, plastic, colorants
     clear rubber epoxy
     silicone, FAQ, high-temp, PDMS
     latex
     thermoplastic, thermoset polymers
     calcium sulfate
        desicant, coagulant, plaster, gypsum, drywall
        Drystone
     Portland cement
        calcium silicate, aluminum/iron oxide, calcium sulfate
        Hydro-Stone
     metal
        Cerrotru casting polishing
        aluminum clay sand glass
     ceramic
     food
     natural
  additives
     fibers (tension, compression, composites)
     fillers: density, conductivity, flexibility, ...
  processing
     workspace
     testing
     mixing
        water capacity
        weight vs volume
        consistency
        striations
     time
        work
        demold
     filling
        pouring
        starting
        vent location
        submerging
     bubbles
        stirring, pouring, vibrating, painting, vacuum, pressure, time
     curing
        polymerization
        cross-linking
        hydration
        endothermic
        exothermic
     demolding
        draft angle
        release agents
           dilute dish soap, vaseline, talc, ...
        deformation
     storage
     shelf life
  safety
     warnings
     SDS
     ventilation
     protection
     disposal
  machining
     surface finish
     rough, finish, stepover
     tool types
        flat end, ball end, bull nose
        extra long, long neck, tapered
        micro
     strategies
     cut depth, shank, collet, collision, slope
  software
     ShopBot VCarve Pro
     Fusion 360 Moldflow
     Solidworks Plastics
     FreeCAD Path experimental
     mods rough finish

assignment
  group assignment:
     review the safety data sheets for each of your molding and casting materials,
        then make and compare test casts with each of them
     extra credit: try other molding and casting processes
  individual assignment:
     design a mold around the stock and tooling that you'll be using,
        mill it (rough cut + three-axis finish cut),
        and use it to cast parts
     extra credit: use more then two mold parts