In the metalcasting industry, the green-sand process has emerged as an ideal choice for nonferrous casting, offering a blend of speed, quality, and cost-effectiveness that is tailor-made for aluminum, copper alloy, and other nonferrous parts. This versatile process can accommodate castings of varying sizes, in low, medium, or high volumes, and cater to the diverse needs of foundries pouring metals like aluminum, brass, and bronze.
Green sand is not just a cost-effective choice; it's a highly flexible solution that allows fast pattern changes, perfect for short runs. Compared to diecasting, the tooling costs are significantly lower, making updates to component designs quick and hassle-free. Moreover, the absence of energy-hungry tooling temperature control adds to the overall efficiency of the process.
Two notable success stories exhibit these capabilities.
Transformation in aluminum casting
Boose Quality Castings in Lebanon, PA, installed a DISA MATCH 16/20 machine at its aluminum foundry, which has been a transformative decision. The change has reduced scrap rates considerably, and also improved the surface finish of castings, leading to substantial labor cost savings. BQC operates three molding lines, all of them fed by a single 100B Speedmullor that can mix up to 100 tons of sand every hour. All the castings are all gravity poured, mostly by hand but at times by a robot.
Seeking higher-quality aluminum castings, v.p. of Operations Brandon Boose decided to replace the foundry’s former molding lines with new machines. There were several other quality-related investments in melting, melt hydrogen level testing, and mold handling too. Two years into operation, the higher-quality molds have improved Boose’s ability to produce aluminum castings with high dimensional accuracy and excellent surface finish.
Running the old molding lines, the foundry consistently recorded weekly scrap rates of 4-5%. Even running at higher speeds (up to 187 molds per hour) the new machine’s scrap rates are less than 2% in an average week, for the same product mix.
A bonus for BQC ‘going green’ has been the cost savings. The new line’s green-sand molds produce a fine surface finish in the final casting, typically around 300-325 RMS (AA-CS-E18-92); Products with releases or very tall risers can come close to 250 RMS.
What’s more, Brandon Boose explained, is that “there’s far less fettling and grinding required to satisfy our clients’ surface-finish requirements, which has reduced our labor costs significantly.”
Intricate pattern designs that the foundry previously struggled with have become a lot easier to produce, too. Rather than being forced to put sand in the cope wherever there were pockets, BQC operators just blow the mold. Tooling costs are low compared to diecasting, and this makes prototyping much faster and inexpensive too, as green-sand tooling is over 90% cheaper compared to permanent molds, and each plate has a performance life that’s now about six-times longer.
A low-alloy-steel DISA MATCH plate can create up to 500,000 green-sand molds, while a permanent mold made from the same material typically will only last for 70,000 gravity diecasting shots. BQC’s most heavily used tooling has so far made 20,000 molds with no detectable wear.
BQC's focus on quality has not just raised quality standards; it's opening new doors. The foundry's expertise in delivering high-quality castings swiftly and at lower costs is a magnet for casting buyers. Recognition of BQC's cost and quality strengths has driven a surge in RFQs for components previously produced only by diecasting, and now the foundry is competing for jobs that traditionally veered towards permanent molding or diecasting.
Around the world, foundries pouring aluminum are taking a closer look at the green-sand process’s potential for high-volume, high-quality production. It fits a wide range of aluminum applications and, depending on the part, foundries can combine the advantages of horizontal or vertical green-sand molding with different pouring methods. Manual or automatic gravity pouring from the top of the mold can be the perfect solution for most aluminum components with less demanding mechanical properties. For the most mechanically demanding castings like safety-critical automotive parts, low-pressure, bottom-filling technology gives the best conditions for the casting to exhibit the highest mechanical properties.
Maximizing quality in brass casting
The DISA MATCH 14/19 machine has assumed a central role at Ford Meter Box in Wabash, IN, bringing notable production advantages for casting brass hardware for water systems. Together with an automatic core setter and cutting-edge digital capabilities, Ford Meter Box is maximizing the quality of its brass casting, and increasing productivity at the same time. It achieved both these while streamlining maintenance processes.
Because many of the castings are produced to carry water, Ford Meter Box needs to set a lot of cores to form the required channels. Unfortunately, its legacy molding machines required manual core-setting, which made cycle time and quality very dependent on operator skill and the size and number of the cores involved.
A DISA MATCH machine with DISA’s Automatic Core Setter was selected to improve brass casting quality and productivity. The result: higher and more consistent brass casting quality, minimal machine mismatch, and the eradication of manual core-setting errors, such as finger holes in the sand. Molding and auto core-setting speeds have surpassed expectations, enabling them to swiftly complete short runs in a working week.
The integration of digital features amplifies the efficiency of the green-sand process. Modern machines like DISA's MATCH incorporate digital functions for data collection, analysis, and recipe management. This ensures optimum machine settings for each pattern, and contributes to consistent mold quality, reducing errors and enhancing the overall work environment.
Green-sand molding, with its matchplate and vertical methods, is gaining recognition as an affordable, high-performance alternative to nonferrous casting processes, such as diecasting. Its advantages, from efficient production for short runs to exceptional quality and rapid pattern changes, position green-sand molding as a versatile option for various non-iron applications.
The successes of BQC and Ford Meter Box are compelling evidence of the transformative potential of adopting green-sand processes. Its eco-friendly and cost-effective nature of this approach will convince foundries to embrace its possibilities especially for aluminum and copper-alloy castings.
Sandy Calabrese is the director of Sales for DISA – North America, a Norican Group Technology.