Beyond our molding processes, additional processes are critical in the production of your casting.
Aluminum Alloys and Melting
Northwest Casting pours aluminum primary alloys A356 and C355, and secondary alloys 333, 319, and 713. We purchase our aluminum ingot from long-time proven and reliable sources. All ingot chemistry is certified per Aluminum Association specifications and documentation can be provided.
Aluminum ingot is melted in eight natural gas-fired crucible furnaces. The optimum pouring temperature for each casting job, determined during the initial sampling process and confirmed with production history, is documented on each casting’s work instructions (Traveler). Melt temperatures are monitored and controlled using hand-held pyrometers. The melt is degassed prior to pouring and porosity content checked using porosity testers.
For aluminum castings that require tempering (e.g., T6, T61, T7), solution treatment is accomplished by our large High-Temperature Bottom-Drop Oven, followed by our lower temperature large Aging Oven. Honeywell controllers precisely maintain oven temperatures while chart recorders document cycle times and temperatures. We calibrate our ovens regularly and confirm casting hardness with a hardness tester.
Sand cores are produced using the shell, CO2, and oil sand core-making processes. Sand cores are positioned in the mold cavity (sand mold or permanent mold) to form the internal ports, bores, and passageways in the casting. Separate tooling is required to produce the sand cores.
Casting Finishing Operations
Ingates, risers and flash are removed from castings using band saws, abrasive belt and pneumatic grinders, per documented instructions. In most cases, we tumble castings in a shot-blast machine which provides a uniform matte surface finish. We also perform foundry-controlled welding. Should machining and/or painting be required, Northwest has subcontract relationships with several machining and painting/coatings shops in our area.
Initial Tooling Investment (Sand Patterns/Permanent Molds)
The castings we produce directly depend upon high quality, reliable production tooling: permanent mold or sand pattern, and often a core box(es). To determine the most suitable and economical tooling for the casting, we spend critical time with you to understand the casting’s function, define the requirements, and review and confirm all the drawing and CAD model specifications.
We partner with several outside mold/pattern makers in our region for tooling design and construction. These are shops with whom we have had long-term and successful working relationships. They have repeatedly proven their ability to deliver high quality, reliable tooling within their promised lead-time.