The Mishima shell is fabricated through a proprietary high-speed Direct Energy Deposition (DED) process that uses lasers to melt and consolidate a pre-impregnated filament composed of a high strength polymer and a high modulus carbon fiber
in an additive fashion.
The process begins with polyamide (PA), an engineering-grade thermoplastic polymer specially formulated for its exceptional strength, impact resistance, and fracture toughness. This is used to form the surrounding matrix for the pre-impregnated filament that is custom made for creating the shell. PA composites are an exotic material more commonly found in aerospace, or other high performance applications such as hypercars. PA particularly excels at processability, as well as being exceptionally moisture resistant, a property most other polyamide-class polymers are weak at.
The other component of the material is the carbon fiber. For this, we use an aerospace grade carbon fiber with an exceptional balance of strength and stiffness. The carbon fiber gives us a tensile strength of more than 680 MPa (megapascals) and a Young’s modulus of more than 75 GPa (gigapascals). The fiber is created through a complex process that oxidizes a precursor material which then undergoes carbonization followed by graphitization to produce linear graphene sheets.
The combination of these materials, as well as some key enhancing agents, gives the material an extraordinary strength-to-weight ratio. This highly anisotropic material is maximized to its fullest with the use of an ultra-rapid robotically driven process, placing and aligning each individual fiber bundle for optimal strength.
We have selected these materials and processes due to the extreme strength to density ratio and stiffness requirements imposed by the mechanical design specification. An additive fabrication approach (as opposed to traditional subtractive methods) is taken due to the multidirectional load requirements of the structure: here both flexion back as the user sits back in the chair, torsional stiffness along the sagittal y-axis (for swiveling) as well as stiffness along the vertical z-axis (so the chair does not bend to the right when a person is sitting on it) are all part of the functional requirements of the asymmetric design.
Once they are fabricated, each shell goes through a series of treatment and post-processing steps to ensure an incredibly smooth and consistent feel. The unit is then primed and coated with multiple coats of paint.