Reviewing Aluminum Gating Systems
Video technology has allowed the testing of several mold fi lling notions the metalcasting industry has long held dear.
S. Nafi si1 1
, B. Mosleh2 , G.R. Kazazie2 , M.A. Boutorabi3
EVRAZ Inc. NA, Regina, SK, Canada 2
SAPCO, Tehran, Iran 3 Iran Univ. of Science and Technology, Tehran, Iran M
old fi lling has a great im- pact on defect formation. Most casting defects, such as gas and shrinkage po- rosity, inclusions, erosion
and misruns, are initiated from inap- propriate mold fi lling within the fi rst few seconds of the pouring stage. Ideal gating systems, on the other hand, can trap inclusions and oxide fi lms and minimize and control fl uid turbulence. The fi lling patterns of various alu-
minum gating systems for sand casting were investigated by observing both water modeling and molten aluminum via a video capturing technique. Non- pressurized systems were shown to produce lower metal velocities and minimize the possibility of inclusion
and oxide entrance. In addition to the lower velocities, design enhance- ments, like positioning the gates above runners, contributed to minimizing the defects. The measured coeffi cients of dis-
charge showed that the distance be- tween gates and sprues, gating ratios, fl uid velocity, area-to-perimeter ratios, gate width-to-length ratios, and runner length were critical for producing sound castings. Generally, greater gate-to- sprue and runner-to-sprue ratios and smaller ratios of thickness to width will
Online Resource
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www.moderncasting.com for video of the water modeling experiments described in this article.
result in higher coeffi cients of discharge and increased fl ow rates. Following is an examination of
the results of the water model test- ing performed on seven different aluminum gating systems.
7 Systems Analyzed Seven aluminum gating systems,
both pressurized and non-pressurized, were examined in the modeling ex- periments. All of the models were manufactured with transparent Perspex and assembled with PVC glue. (Due to
Fig. 1. Shown are the pouring basin (top) and seven gating systems studied: System 1, System 2, System 3, System 3A, System 4, System 5 and System 5A.
MODERN CASTING / September 2010 35
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