What are the principles of pattern making?

Answer 1

Pattern making in reference to foundry production involves making a wooden (generally, however polystyrene, plastic and metal patterns exist as well) relipica of the final product however different in very distinct ways. The difference between a a true replica and that of a pattern is that a pattern is used to make the imprint in either green sand or chemical sand (look up sand casting in Google for better explanations) to produce a mould. This mould however must also include things such as core prints so that cores can be inserted. The pattern must factor in taper, contraction (change in size of the metal as it cools in its solid form to room temperature- thus the pattern will be made slightly larger then its final metal product), grain direction is also important in considering what direction the mould goes in and out, and the use of paints in many cases . Taper (essentially sloping a surface) is so the pattern can be removed easily from the sand. If this isnt done or not enough enough taper is applied then the sand mould could be damaged or in the case of chemical sand it could be stuck.