Method and apparatus for making molds

Abstract

Apparatus of the invention includes a dispenser for mixing an discharging layers of the molding material onto the mold forming pattern, and means for producing selectively controlled relative movement between the dispenser and the pattern including a control system for varying the ratio of sand and binder in the mixture being dispensed in accordance with the relative position of the dispenser and the pattern. The apparatus may thus be controlled to provide for selectively variable ratios of sand and binder in accordance with the strength required of the mold at a particular position. The system also provides a selectively variable control of the thickness of each layer of molding material as the mixing head or pattern moves on a three axis coordinate system. For relatively small and light castings the mixing and dispensing head may be retained in a relatively fixed position while the pattern is selectively moved in a three axis coordinate grid while with large castings, the pattern is stationary and the mixing head is moved. The mixing and dispensing head is particularly designed for use in the field of 'no-bake' sand-resin-catalyst mixing and includes facilities for controlling the mixing operation so that the mixture does not set up and harden in the mixing head between mixing operations. Also, the constituency of successive layers may be varied and the amount of organic binder material minimized so as to reduce smoke and fumes during the casting operation.