The adaptation of patterns to the present-day demands on the foundry for large output of duplicate castings makes it imperative to so arrange the equipment that the largest number of castings per molder-day shall be obtained. This will reduce the labor cost per casting, and where machine molding does not increase the output, it will be possible to employ unskilled workmen, which will lessen the cost. To accomplish this, various arrangements of the patterns have been worked out and the castings all come under the heading of machine molded castings.
The concern manufacturing molding machines often contracts to mount on their machines such patterns as are required, and in that case the design and molding operations are worked out by the designing department. However, in many pattern shops the adaptation of the patterns is left wholly to the pattern maker. Now the study of the problems presented is such that the pattern maker soon becomes a specialist, and, if just taking up this work, it will be well to consult the foreman of the foundry, for many questions will arise where the pattern maker would find it difficult to give a practical decision.
Every class of castings calls for a different solution about the equipment that makes the work special. A machine mounted pattern that is a success in one foundry will often be a failure in another. A pattern fitted for machine molding, with the expectation of an order for 1000 castings, probably would not be the same arrangement if the order were for 100,000 castings. Greater expense could be put into the pattern equipment for the larger order, and should be done if the output could be increased. The output per day should be considered, and where a number of small duplicate patterns can be molded in one operation, the flask should not be so large that the operator cannot handle the mold easily.
All in all, this field offers a study of molding and the pattern-making propositions not found in the usual classes of hand-molded patterns. To attempt to offer a complete work on this branch of pattern making would be folly in the extreme. The personal experience of any one expert would require a large amount of space, and the possibilities would only be touched upon.
The changes that have taken place the past few years in the process of machining steel are also evident in the methods of machining castings. In machining large numbers of duplicate castings the machinist resorts to jigs for holding the piece while the work is being completed. It is the case that hand-molded castings will vary in dimensions to some slight amount, due to the slight difference in rapping during molding, which cannot always be kept constant. Patterns are sent first to one foundry and then to another and made today by one molder and tomorrow by another. Even if a machine-molding equipment does not increase the output, the uniformity of castings and the unskilled labor that can be employed will generally pay for the outlay.