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Abstract

Three dimensional objects or models, such as three dimensional images or shapes stored in a computer, are generated as real models by addition of material to a base, such as with photo-hardenable liquid, or by removal of material from an initially oversized mass. Optical feedback is employed to monotor the actual condition of the model being formed, at each work site. The condition of the model at the work site, e.g. the presence or absence of material, is fed back to the machine or building tool, or to a computer controlling the tool. On the basis of such monitoring and feedback, decisions are made whether or not to perform more work at any particular work site. In this way, the actual three dimensional model being constructed is made to conform substantially to stored information relative to the desired dimensions of the model. In a preferred embodiment, models are produced by ablating a mass of small spheres held together by a relatively weak wax or cement. The spheres are cemented together preferably only at their small areas of contact. The ablating may be accomplished by a laser beam whose energy is focused in succession on balls which are to be removed, heating them and breaking the wax or cement bonds. Feedback of the model condition may be optical, e.g. by laser distance measuring non-contact sensors. Alternatively, the spherical balls may be removed by blasts of hot air or gas delivered through a narrow tube. In this case monitoring and feedback may be via measuring of capacitance between the air-delivering tube and the model, representing distance, or by monitoring of the pressure in the tube, indicating distance from the model.

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First Claim