Solving Customers’ Problems
Several examples show how metalcasters collaborate with customers on design and process improvements.
An MCDP Staff Report
(Click here to see the story as it appears in the September/October issue of Metal Casting Design & Purchasing.)
Unfortunately in manufacturing, not every part is a straightforward design with a straightforward method of production. When you need a component to reduce cost, provide critical properties or be delivered in an abbreviated time frame, working closely with your metalcasting supplier can yield solutions.
Whether it is a conversion to casting from another manufacturing process, a tweak to an initial casting design, or the use of alternative tooling methods, good metalcasting suppliers are often able to match the your concerns with feasible solutions.
Following are instances where casting facilities stepped in to help a customer address and solve a problem through engineering, process control or new technologies to update decades-old patterns. The metals, applications and casting processes may differ, but what remains the same is the open customer-supplier partnership.
Weldment to Casting for Performance, Strength, Appearance
In 2013, agricultural tillage equipment manufacturer Wil-Rich, Wahpeton, N.D., approached Monarch Industries Ltd., Winnipeg, Manitoba, Canada, to explore converting a weldment to a ductile iron casting. The component on the SoilPro 513 double disc ripper provides the main mounting structure for the shank assembly to be attached to the frame of the tillage unit. It also contains three of the major pivot points for the trip assembly.
Originally constructed with eight steel pieces (torch cut and bent or saw cut, then welded and machined), the component was difficult to manufacture consistently and alignment remained a challenge. During welding, the supplier needed to rely on the fixture to hold the pin holes in alignment, and Wil-Rich also had issues with the weld holding the bushings in place.
The casting conversion featured a single core in green sand. With an annual production volume of 2,000 pieces, the D64-45-12 ductile iron casting measures 22 x 12 x 10 in. (55.88 x 30.48 x 25.4 cm) and weighs 55 lbs. (25 kg). The customer realized a number of advantages, including:
- The machined casting provided a 25% reduction in cost over the original weldment.
- By converting the component from a weldment, Wil-Rich freed up plant capacity in the welding and fabrication departments.
- The machined casting, compared to the welded fabrication, resulted in much improved alignment in the holes with tighter hole-to-hole tolerances.
- The cast component eliminated
- issues related to warpage and assembly interferences associated with the weldment.
- Wil-Rich reported the casting increased strength. Monarch designed the casting to add extra material in areas where strength was needed, which was more difficult and costly in a weldment.
“We looked for ways to lighten the part with cast windows but still provide the required strength through varying fillets,” said Matt Downing, pattern shop manager, Monarch Industries. “With good communication, it wasn’t long before we had a cast part that met the customers’ needs and was ready for FEA testing.”
The customer also reported that the cast component improved the overall appearance of the shank arm. The company logo and part number were incorporated into the design.
The castings were machined and painted onsite, allowing Monarch to deliver components ready for assembly.
Reverse Engineering a 30-Year-Old HVAC Duct
When General Dynamics Land Systems, Sterling Heights, Mich., needed to update the heating, ventilation and air conditioning (HVAC) system on the Abrams M1A1 tank, it faced a few obstacles. General Dynamics approached Barron Industries, Oxford, Mich., with potential project, but the investment casting firm decided to no-quote. The particular part’s complexity and relatively small order—only a few dozen would be needed annually—led Barron to assume it couldn’t be competitive price-wise. But General Dynamics, which has worked with Barron since the 1980s, encouraged the engineers to take a second look, and they were awarded the bid.
The next problem: General Dynamics had an example of the part and its blueprint from 1983, but no model. Previously an aluminum fabrication, the duct helps cool electronics on the Abrams tank. Thanks to ongoing redesigns of surrounding components, the duct faced restrictive spatial requirements and multiple attachment points, which made investment casting the logical choice for production.
“We had to reverse engineer it,” said Bruce Barron, president and CEO. “The information we received was minimal, so we generated our own 3-D model data imported from our coordinate-measuring machine. Really, once we could generate a 3-D file, we had something that could be utilized by the toolmaker, process engineer, machinist and final inspection personnel. That put everybody on the same page.”
After generating a model from the nearly 30-year-old blueprints and part, Barron engineers received minor changes from the customer, including the relocation of an outlet to accommodate additional changes in the vehicle’s design. Production began on the 13.39 x 8.27 x 4.33 in. (34 x 21 x 11 cm) duct, with special attention focused on the tapered “necked down” section of the 1.25-lb. casting, which presented the biggest challenge.
“It’s such a long, narrow passage way, in order to apply the ceramic coating and stucco sand, the articulations within the robot program required some modifications,” Barron said. “It required some part-specific process engineering.”
The ceramic removal also proved challenging. Engineers developed a special nozzle for the water jet blasting operation to ensure the thin-walled duct remained fully intact. Castings were pressure tested, and wall thickness was verified via radiography.
“Because of its placement within the already crowded engine compartment, this is not an easy part to install and remove,” Barron said. “When we deliver it to [General Dynamics], we believe that they will never have to touch it again after installation.”
Impeller Cast Using SLA-Printed Patterns
Needing to replace two double suction impellers with 30-in. diameters, SPX, Charlotte, North Carolina, decided to explore alternative casting processes to improve performance and limit lead times. It contacted Tech Cast LLC, Myerstown, Pa., a producer of large, precision engineered investment castings using stereolithography (SLA) rapid prototype technology, an additive manufacturing process that produces objects from CAD models by printing successive layers of curable resin that are hardened via a beam of ultraviolet light.
Because an older wood pattern was the only model for the 500-lb. impeller, Tech Cast needed to generate a 3-D drawing for production of the mold. (The 3-D printing was handled by a third party.) Despite having to generate a 3-D model from scratch, Tech Cast produced two impellers in corrosion-resistant martensitic stainless steel at nearly equal cost in half the time as the traditional method.
“It took us about two weeks to produce an SLA prototype,” said Shawn McKinney, general manager, Tech Cast. “Actual manufacturing time, from receipt of the prototype to delivery of the casting, was four weeks.”
Cast nearly to net shape, the components required significantly less machining and avoided the time-consuming welding/grinding loops that typically were necessary with green sand casting. In all, the lead time dropped to six weeks from the previous 12 weeks. Additionally, no defects were discovered on the impellers.
The order was relatively small, but Tech Cast’s ability to produce the castings quickly and cost effectively has resulted in additional opportunities with SPX.
While Tech Cast plans to continue to receive its 3-D molds from an outside vendor, additive manufacturing can reduce tooling costs and lead times, which can make investment casting more competitive by reducing lead times for short-run components.
“Traditional investment cast tooling can take 8-12 weeks to build and may require significant capital investment, both of which can present barriers to entry into this manufacturing process,” McKinney said. “The use of additive manufacturing technology to produce quality investment castings represents an area of organic growth opportunities for investment casting manufacturers to expand their businesses.”