Looking to offset dramatic material and transportation cost increases, Raymond Corp. turned to Design for Manufacture and Assembly (DFMA) software when performing a detailed part count reduction study and product design optimization of its Model 7400 Reach-Fork forklift truck.
Not only was Raymond able to cut part count by 10% and reduce total assembly cost by 18% in the 7400’s hydraulic cylinders, but it also saw positive effects from the design optimization trickle down the supply chain into savings on factory-floor space, manufacturing time, and ease of maintenance for customers. “We now have an enhanced cylinder design, and the patented part of it still performs the way it always has,” said Matthew Miles, Raymond Mechanical Engineer.
The patented part is the staging cylinder, which provides the capability to raise and lower a load of product with reduced noise and staging impact.
This technology, first incorporated in newer operator-up lift trucks in late 2003, proved popular with Raymond customers. But in recent years, skyrocketing material and transportation costs began impacting the manufacturing costs of the material-handling solutions Raymond offers its customers. “We needed the weight and strength of steel for our trucks, so we couldn’t go to other materials,” Miles said.
In addition, the rising price of fuel was impacting the company’s transportation costs since it manufactured different components of the 7400 in different locations in North America. “We wanted to maintain the performance of our product while managing value pricing for our customers,” Miles said. “The solution was to reduce our manufacturing costs through part-count reduction to offset those factors we couldn’t control. That’s where DFMA came in because it allowed us to maintain quality and reliability.”
DFMA software is a combination of two complementary tools: Design for Assembly (DFA) and Design for Manufacture (DFM) Concurrent Costing, both from Boothroyd Dewhurst. DFA software is used to reduce the complexity of a product by consolidating parts into elegant, multifunctional designs. DFM software then allows the design engineer to quickly judge the cost of producing the new design and compare it against the original.
Using DFMA to investigate the 7400 design, Raymond’s Mechanical Design Engineering group studied everything from the elevating section to the tractor and operator’s area and found that the hydraulic cylinders—particularly the patented free-lift cylinders—yielded the most significant manufacturing cost savings potential.
The first step in the process was to examine the current staging cylinder and brainstorm ideas about how to reduce part count of the patented component without losing any cushioning or causing an increase in noise during staging. “This is where the DFMA software was effectively used to estimate potential changes in cost with each of our new design ideas,” said Miles. “We used DFA to analyze the cylinder assemblies and determine the feasibility of each new design idea. We next projected its cost using DFM, and then decided on the best course of action.”
The analysis involved determining the baseline cost of the cylinders, developing new designs, and then costing those against the baseline. “The DFMA tools helped us reach certain decisions like substituting a snap ring or a spring-loaded plunger for design ideas that called for screwing parts together—which were ultimately ruled out,” said Miles.
When promising results were identified with the software, prototypes of the design-optimized cylinders were built and test-cycled to measure function and durability. “Once in production, the design-optimized cylinders delivered virtually the same performance from the cushioning and noise reduction standpoint,” said Miles. “And the patent was unaffected.” The original design used 37 parts, the new one only 28. Cylinder assemblies for the free lift went from eight to six and for the main lift from four to one.
Raymond’s DFMA project was a collaborative effort that included the company’s manufacturing operations team, which was in the process of reconfiguring a new layout for its hydraulic cylinder assembly area (the “ram cell”) to increase operating efficiency. “We were working closely with manufacturing and asked them what we could do with the product design to make their job easier and streamline the process in the ram cell,” said Miles.
The operations team contributed to the design optimization with suggestions for improved manufacturing methods, such as eliminating machining operations on the cylinder housing by reducing a traditional two-part design to one part. A combination end cap/manifold eliminated welding the existing manifold to the tubing side, removing machining from the tubing and reducing welding times considerably. The top end cap was also changed to a screw-on configuration instead of being retained by a snap ring, further reducing machining. Lowering the chain anchor also allowed manufacturing to weld the anchor in a different order, saving more time in the assembly process.
Using more common parts between cylinders brought further economies to the design optimization. The free lift chain anchors were reduced from right- and left-hand parts to a common part used on either side. Analyses of the internal assembly also led to using more common parts on both the main and free lift cylinders. Changes such as these generally increased total annual part quantities ordered, lowering part costs in some cases.
Factory floor space reductions were an additional benefit of common parts. “When we used common bleed screws, instead of four or five buckets of different screws, you only needed one,” said Miles. “This saved space on the factory floor and cut manufacturing time. It also led us to the idea of moving the location of the bleed screws into the end cap, which removed a machining operation out of the weldment and put it right into a piece part.
“When you add up all the small things in a project like this it really comes together,” says Miles. Total estimated labor time per cylinder was reduced by 24%. The number of cylinder housings produced per hour increased from about four to 13.
“It’s difficult to put a price tag on using common parts, or reducing part number inventories, but everyone knows that if you have fewer parts, that means fewer part numbers to produce and track,” said Miles. “So many different areas and departments are impacted by having to work on, or track, fewer parts. The downstream effects of implementing DFMA are considerable.”
Raymond is now implementing DFMA across its entire lift-truck line to identify the most cost-effective designs that match the original intent of each model.
Lynn Manning, Senior Writer, Parker Group, wrote this article for SAE Off-Highway Engineering.