design and fabrication of multimaterial flexible mechanisms with ...

12between component insertion and component embedding. In the former case componentsare inserted into a cavity inside part material after the surrounding part is builtwhereas the immediate surrounding part material is cast after component placementin component embedding. Kataria et al. have developed methods for inserting componentsin stereo lithographed structures (Kataria and Rosen, 2000). DeLaurentiset al. have produced a robotic vehicle with inserted components also using stereolithography (Mavroidis et al., 2001) (DeLaurentis et al., 2002). These works mentionlimitations related to laser shadowing and obstruction of the material addition dueto the strictly planar layered nature of the fabrication method. This poses numerousconstraints on what can be inserted and when. Besides, the components are simplyinserted into a cavity that is left out during fabrication. Hence, there will be noadhesion of the encasing polymer to the inserted components unlike with embeddedcomponents in which polymer is cast and cured directly around them. For this reason,inserted components may have limited support from the encasing polymer comparedto embedded components.Component embedding has been implemented earlier in mass production. Insertmolding is common in large volume injection molding of thermoplastics and thermoplasticelastomers (Digiantonio, 1992) (Digiantonio, 2005). For example, many cableconnectors for electronic appliances have molded insulation housing over the metalconductors. An in-line skate wheel consists of inserted rigid core material and moldedhigher-friction tire material. (Please note the difference in the use of the word insertin this paragraph and the one before. Insertion in the previous paragraph refers tothat with respect to the polymeric part that is being produced. In this paragraph,it refers to the insertion of the component into the injection mold.) Since it is nota layered manufacturing, the part material can conform and bond to the insertedcomponent surface as it is injected into the mold. Two-shot molding of differentpolymers, as often seen in toothbrushes with hard and soft material, is also a similarprocess. Large volume production also justifies greater time and monetary investmenton creating customized equipment for insert molding or two-shot molding. That isyet another factor that enabled the implementation of component embedding in massmanufacturing.