- 46″x46″x16″ golf car floorboard
- Convert from steel to plastic.
Eliminate rust and corrosion.
Provide sufficient stability to bolt all critical
components to it.
When E-Z-GO, a leading manufacturer of golf cars and utility vehicles, came to Mack’s Inman, S.C., plant with its design for the new RXV™ golf car, they knew they wanted a plastic floorboard and that any remaining metal in the new design had to withstand a 1000-hour salt spray.
Taking into consideration the square footage of the part and the recommended resin, Mack engineers determined a 3,300-ton press would be needed to injection mold the estimated 35-lb. part. “We priced it accordingly,” says Ken Kincaid, technical engineering manager for Mack’s southern division, “but a competitor came in lower, proposing a low-pressure structural foam process in a multi-nozzle machine.”
With a low-pressure structural foam molding machine, a molder can inject a large amount of resin with less clamp pressure than a typical straight injection molding machine, requiring a smaller and less expensive press. There are trade-offs, however, including a slower cycle and multiple injection points.
“We knew that one gate, rather than the 12 (plus or minus) required for the low pressure structural foam approach, would produce a stronger part with far fewer knit lines,” says Kincaid.
“We also knew that a single nozzle straight injection machine utilizing structural foam would yield a faster cycle time than a multi-nozzle low pressure structural foam machine,” adds Program Manager Steve Langen. “This was critical, not only because of press time, but also because of tool cost. Once the golf car was in full production, a second tool would be needed if the cycle time went over 200 seconds. With injection molding, the OEM was much more confident that we could keep up with the full ramp of their production without adding a second tool.”
An unconventional approach
To be cost-competitive, Mack’s engineers had to think beyond conventional formulas to reduce the press size. “We came up with the concept of building a machine with a 30+ lb. shot size and only 1500 tons of clamp pressure,” says Kincaid. “Based on those new parameters, we quoted it again and won the business.”
In the end, Mack commissioned a 1500-ton press with a 690 oz. shot size to be built especially for this job. “It’s at least twice as big as a normal shot size for that machine,” says Kincaid. Molded of glass-filled polypropylene, the now 26-lb. part is picked by a robot, which articulates it out of a “pretty tight space” for secondary operations at the press. It is then packed and shipped to the customer.
“E-Z-GO was concerned originally that the plastic version wouldn’t be strong enough structurally to pass their rigorous tests,” says Kincaid, which include a five mph side-impact test. “So they really over-engineered the part, with the original samples weighing in at about 35 lbs. To their credit, they went back to the drawing board and reduced the part weight by 29 percent by removing reinforcement ribbing and excess plastic. While it required massive engineering changes to the existing tool, the 9-lb weight reduction paid off in less than a year.”
E-Z-GO RXV meets with success
Launched in November 2007, the E-Z-GO RXV is enjoying unprecedented success in the marketplace. According to a company press release, many E-Z-GO customers “say they have already recognized noticeable benefits from the RXV — from appreciative golfers to simplified maintenance to bottom line savings — due to the vehicle’s unprecedented energy efficiency.” The RXV is available in both electric and gas models.
Contact: Ken Kincaid, Mack Technical Engineering Mgr.
Steve Langen, Mack Program Manager
E-Z-GO, a Textron Inc. company, is a leading manufacturer of golf cars and utility vehicles. E-Z-GO is the preferred golf car fleet provider for many of the world’s most revered golf courses, clubs and resorts. E-Z-GO is also the golf car of choice of nine of the nation’s 10 largest course-management companies. E-Z-GO boasts the largest sales and service network in the industry, with more factory branch locations and independent distributors than any other manufacturer.
More than a maker of golf cars, E-Z-GO is also a leading provider of turf and utility vehicles for a variety of applications and industries. Products under the E-Z-GO flagship include Shuttle personnel carriers, MPT turf-maintenance vehicles, and ST personal utility vehicles. E-Z-GO also produces the Cushman line of heavy-duty burden carriers.
Founded in 1954 in Augusta, Ga., E-Z-GO became part of Textron Inc. in 1960.