Shrink up Art handwheel castings

Household sewing machine handwheel last round structure is complicated, hand wheel rim to the outer surface of chrome-plated, with holes such defects are not allowed.
        The last round of the handwheel original use of open--0.6: 1.1: 1. Each hand wheel has six within the gate, the gate and the workpiece results form a hot junction section, not feeding produce cratering. Slag also easy access to the cavity, causing eye slag, increasing the difficulty of the gate in the clear, easy to produce defects such as lack of meat.
        Later modified to a high trapezoid runner, flat thin inner convoluted, but not resolved shrinkage defects. Also due to the flat thin increases the gate of the mold surface lift force, increasing the expansion tank defects.
        Finally, we use has cast a dark riser feeding system. Each hand wheel within just one gate to produce a dense qualified hand wheel casting, the yield from 45% to 95%.
        Its main features are:
        1. The molten iron is poured into the casting riser after dark, causing solidification to improve the feeding capacity at the gate, thus ensuring the compactness of the hub and the rim.
        2. Using high casting temperature and casting speed slow. Prevents handwheel shrinkage, cold traps, oxide slag and other defects.
        3. Change and change the chemical composition of pig origin, the formation of rival round hole type defect little effect.