Excerpt from the October 2013 issue of Foundry Management & Technology by Mark Riekert and John Kuhn
Robotic sand core setting into a mold has the potential to increase molding productivity and reduce casting scrap.
With the evolution of casting designs, driven by requirements for lower-weight parts and (in automotive applications) a desire to minimize assemblies, there follow designs with thinner walls and smaller openings/cavities. These structures need cores to create those thin wall sections, and in some examples these walls are as thin as 4 mm. In addition, small cores are used to create small openings and cavities.
Adding to the difficulty of the arrangement, gripping the core was a very specific challenge. The end-of-arm tool (EOAT) or end effector uses a rubber "squash" ring to expand inside a hole in the core, and a parallel gripper to contain the tail section of the core without actually gripping it. The core was specially designed with a hole to allow the tool to grip it.
But, small cores are fragile and prone to crack, and when they do crack the result is a scrap casting. Usually, that scrap is not detected until the finishing stage, or under X-ray analysis, and sometimes it’s not discovered at all.
Scrap reduces profitability, and so for foundries that produce thin-wall castings to achieve competitiveness, the core handling and setting process must be gentle and repeatable.
Obviously, good cores are the starting point. Proper resin levels, adequate definning, and accurate assembly are the foundation of that effort. Transporting these cores and core assemblies to the molding machine without breaking them is the next critical step. The final step is setting the core into the mold.
Setting the core in the mold -- specifically into a permanent mold -- can be a delicate procedure. Done manually, there is potential to cause damage to the core and leave loose sand inside the mold. Further, the machine operator is at risk of burns, crush injuries, back strains, and carpal tunnel syndrome in the wrist thanks to the strain of repetitive awkward motions required to place the core properly. Automating this core setting operation with a six-axis, foundry-hardened robot (which will replicate the movements of an operator), addresses the issues of core damage during setting and sand inclusion, as well as removes the operator from the hazards mentioned above.
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