Automotive SMC: The wheel comes full circle
The year was 1972, and Dr. Joseph N. Epel, was the director of The Plastics Research and Development Center the Budd Co. Called by some the “grandfather” of sheet molding compound (SMC), Dr. Epel approached Sterling Detroit and asked us to design and build a system to handle SMC.
Sterling went on to design and produce the first automated handling system that could load an SMC “charge” into a compression press and then remove a molded part at the end of the molding cycle. In fact, during the next two decades, Sterling would build a significant number of SMC automation systems for the automotive and heavy-truck industries. These rapid handling systems helped ensure SMC processing could keep pace with the 250,000 to 500,000 vehicle production volumes that characterized the auto industry in those days. The facility where it all began was Budd Co.’s Duralastic Div. plant in Carey, Ohio, and that first part was a grill-opening reinforcement (GOR) panel for the Oldsmobile Toronado. It required a Class A surface, was approximately 66 inches/1,676 mm wide, weighed 12 to 15 lb (5.4 to 6.8 kg) and used between two and four plies to fill out the tool.
It was obvious to us from that first job that this process would require special material handling. First, placement of the charge in the tool required a high level of accuracy and repeatability if quality parts were to come out the other end. Second, the weight of the SMC charge had to be accurate and consistent if molds were to fill out properly. Third, because the presses used to mold SMC parts were quite large, human operators had to reach into the tool to retrieve molded parts and then position charges for the next cycle. This created a potential safety issue for workers. Before automated handling systems were installed, one plant mandated press shut down and placement of safety blocks before workers were permitted to reach in and remove the part and lay up the next charge. And given the size and weight of many of these parts, two workers were required to pull each piece from the tool. However, if they pulled unevenly or were not careful about how they carried and laid down the part, it could crack, which then required either rework or scrapping the large part.
At about this time, one of the largest automotive parts that was processed in SMC was the original, full-size Chevrolet Blazer roof, produced by General Tire Div. (Marion, Ind.) at its Ionia, Mich., plant. The part required a carefully weighted charge and very accurate placement. Given the size of the charge going into the tool and the part coming out, manual handling and unloading of the mold presented many challenges. Sterling was asked to develop an automation system for this plant, and it remained in service until the run of the Blazer ceased in 1994.
Throughout the 1970s, 1980s and 1990s, interest in and production of SMC parts continued to build steam. GM’s Oldsmobile Div. had multiple SMC presses and pushed to manufacture numerous parts. Buick’s Flint, Mich., plant was using injection molded SMC for its grill opening panel. The company was aggressively active in introducing waterjet cutting to trim the sprue and to cut out the headlight opening from demolded parts.
The heavy-truck industry discovered SMC in the late 1970s and early 1980s. Rockwell International began molding very large SMC parts for the entire hood and fender assembly of an International Harvester truck. Rockwell also molded many SMC parts for Ford Motor Co. at the former’s Centralia, Ill., plant, including inner and outer door panels for an early Explorer SUV. At that plant, Rockwell had installed a highly sophisticated MTS compression press (MTS Systems Corp., Eden Prairie, Minn.). This system incorporated numerous load sensors that allowed the press to “load” the platens, an early version of what we now call parallel leveling, on its own mold to create a better part. Other suppliers like General Tire’s parent GenCorp (Rancho Cordova, Calif.) and EaglePicher (Ashley, Ind.) also were increasing their involvement with SMC.
During this period, Sterling developed and patented several novel mechanisms for handling and placement of composite materials, such as SMC and glass mat thermoplastic (GMT) composite. Things were going gangbusters with automotive composites. GM, for example, was planning a major facility expansion in New England to manufacture parts for its “stylized” APV minivans.
And then the wheel almost came to a stop. Seemingly overnight, SMC went from good material to bad. Paint pops, caused by volatiles trapped in the material that surfaced when parts were reheated during paint bake, became a real quality issue and a nightmare for SMC suppliers to solve (see “SMC resin and primer advances prevent paint pops," under "Editor's Picks," at top right). And environmentalists were asking how suppliers would deal with scrap from SMC molding operations. The material was not recyclable, so what was to be done with part trimmings? As Europe began to talk about end-of-life recycling efforts, they asked how would automakers deal with SMC parts on junked cars? All the while, steel manufacturers were there to talk about their new, lighter products that were both recycled and recyclable.
Today, things are changing again.
SMC suppliers solved the paint pop issue around early 2000. During the intervening years, they have reformulated SMC. It is now available in lower densities for lighter parts and requires even less surface prep before painting. The recycling issue has gone away as well. Today, scrap SMC is reclaimed and made into rot-proof “deck wood” posts and other construction materials.
After the 2008 automotive industry crash, a lot of old plants with steel-stamping equipment, and some of the SMC molders mentioned in this article, closed and were written off the books. Although the industry is starting to pick back up again, things are different. As new plants are built and existing plants are refurbished, composites are being considered again, but in production volumes that might be one-fifth of those in the 1980s and 1990s. Now it is easier for purchasing departments to see the cost savings that are possible with composites. Fuel prices are rising once again and tougher regulations loom, so taking mass out of parts is again at the top of every engineer’s to-do list. SMC and other composite material forms are starting to see new growth.
Once again it’s an exciting time to be a part of the automotive composites industry. The wheel has come full circle.
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