On the inside track of the custom rim industry with Ultra Wheel.

This California-based permanent mold foundry uses both design expertise and technology to keep pace with aftermarket demands for aluminum automotive wheels.

When Jim Smith started Ultra Wheel Co., Buena Park, California, in 1985, the automobile aluminum wheel business was already a crowded and highly competitive industry where "giants" had fallen and new-comers were swallowed up. But he saw a void in the industry--the cost of aluminum was low and wheel supply was not as great as demand. Smith, a life-long auto enthusiast with years in the industry, saw a business opportunity in the "aftermarket" segment for a foundry that would produce quality wheel castings with the latest contemporary designs.

Custom automotive wheel manufacturing began to develop in the late 1960s, emerging from the "hot rod" movement in Southern California. The original wheel manufacturers were "all a bunch of car buffs," Smith said. He himself began in the auto industry in 1968 changing tires at the racetrack for driver Parnelli Jones. The tires removed from the racecars were sold to the public, but they did not fit standard wheel rims, and custom wheels had to be made. Smith became fascinated with wheel manufacturing and the auto industry, so much that Ultra Wheel still sponsors a company car on the Nascar racing circuit.

In those early days, custom wheel foundries produced cast aluminum and magnesium wheels. The industry quickly settled on aluminum, and permanent molding became the preferred casting method. From its youth in the 1970s, the aluminum wheel market has grown into an industry that will produce almost 20 million wheels in 1998 for original equipment manufacturing, or wheels made for the major auto manufacturers and used as custom options for new car purchases.

By 2006, approximately 51% of new cars and light trucks will have aluminum wheels, according to Stratecasts, Inc., Fort Myers, Florida. (See "Aluminum Wheel Forecast in the U.S.") Approximately 3 million additional wheels will be produced in 1998 as "aftermarket" wheels, which are sold most often through custom automotive shops and tire/wheel stores to individual owners who want to upgrade their cars. The selling price for an aftermarket wheel ranges from $60 at the low end to $700 for a high-end chromeplated rim.

It was into the volatile aftermarket segment of the industry that Smith sought to carve a niche. Because the aftermarket segment is highly sensitive to consumer whims, it requires anticipating design trends, continually developing new wheel designs to feed public demand and maintaining a distribution network that guarantees availability of those new designs. All the manufacturers "strive to come out with the best designs--the one who does gets the business," Smith said. "The keys to success are design and quality, but most of all service and delivery."

After helping to start several wheel foundries, Smith began Ultra Wheel Co. in a 25,000-sq-ft warehouse in Garden Grove, California. At that time, Ultra Wheel was using gravity permanent mold (GPM) casting to produce three to four wheel designs from a 4500-lb Stahl dry hearth reverberatory furnace. Eleven years later, he is shipping more than 400,000 wheels yearly from his new 250,000-sq-ft plant in Buena Park, California. The product line currently includes 50-70 different styles with various options such as painted, chromed or polished wheels in all standard wheel sizes and bolt patterns.

Engineering

All wheels begin as "styling concepts," according to Ultra Wheel General Manager Ron Schultz. The management and sales groups envision a new wheel style, and the wheel is designed in CAD-CAM, with engineers working to meet all the application specifics such as bolt patterns and mechanical requirements. For many wheels, only the face is changed with each new style so that the most basic engineering and safety features do not need to be recalibrated or reconfigured with each new wheel. A computer-modeling program simulates the wheel in use and performs testing procedures to ensure engineering integrity prior to mold-making. Often, plastic or foamcut models will be produced to show the new style. After the design is approved, the tool is built with an emphasis on ease of production and casting mechanical properties.

Ultra Wheel has full mold-making capabilities and produces molds for both its GPM and low-pressure processes. All molds are made in H-13 steel, with internal air channels for mold cooling. Ultra Wheel does not use solidification modeling. Because the shape and wall thickness of the wheels remain basically the same with all styles, solidification modeling is not widely used in the wheel industry. The designers and engineers draw on their years of experience and production to anticipate problem areas and ensure properties.

Automotive wheels must meet Society of Automotive Engineers and U.S. Dept. of Transportation safety standards for aftermarket wheels. The wheels undergo fatigue testing for cornering, impact and radial properties. For the cornering and radial tests, a tire is mounted in the rim and the wheel is mounted on an axle to simulate operating conditions. The cornering test requires 100,000 cycles to confirm the integrity of the spokes. The radial fatigue test measures the impact of the wheel to direct hits such as potholes in the road (500,000 cycles). The side impact test involves a free weight dropped onto the side rim.

Foundry Procedure

Although for many years aluminum wheels were centrifugally-cast in permanent molds, "spinning" is less common today. Most wheels today use GPM casting or low-pressure permanent mold casting, which is gaining an increasing proportion of the total production. Ultra also produces wheels with "counter-pressure" permanent mold (CPPM) casting, a popular wheel industry casting method similar to low-pressure casting. Counter Pressure Casting Technology, Inc., Laguna Hills, California, produces the CPPM machines.

All wheels are poured from A-356 aluminum, degassed, strontium-modified, grain-refined and heat-treated to T-6. Metal samples are taken every 2 hr during the production shifts. The metallurgical lab checks chemistry and specific gravity, and the melts are adjusted accordingly. Ultra Wheel does not use fluxes, due to the restrictions of California air pollution standards. The company uses a real-time X-ray fluoroscope to confirm quality, and all wheels are pressure-tested for leaks. Because all wheels are polished and many are chrome-plated, porosity and cosmetics are major quality concerns.

Wheel molds are typically cast with the wheel on its rim. Two mold halves, called side cores or clamshells, form the inner surface of the wheel or the wheel/tire air chamber. The outer design is cast face down, and a removable top core casts the back of the wheel. Ultra Wheel gates its GPM wheels from the side (Fig. 1).

[Figure 1 ILLUSTRATION OMITTED]

The GPM wheels are cast both with an auto-pouring six-station carousel and in static, hand-poured molds. On the carousel, the wheels are single-poured into one of two side gates, while the other gate is blocked with a mold insert to become a blind riser. A different insert is used and the second side gate is opened, at which point static hand-pourwheels are poured "two-up." All GPM wheels are cast with a riser on the center hub and the upper rim (a ring-riser). Although some older styles still use a shell core for the center hub, which is produced in-house, all molds are now made with steel cores.

Ultra Wheel has customized a carousel to produce most of its GPM wheels. Carousels excel when running multiple molds of the same casting, in which cycle and pour times for each mold are equal. But the wide variety of designs produced in an aftermarket wheel foundry created the challenge of trying to run different wheels of varying sizes, weights and cycle times on the same carousel (Fig. 2).

[Figure 2 ILLUSTRATION OMITTED]

The current carousel machine holds six molds and each mold station is programmable for pouring time and weight. The molds are air-cooled and the cooling time is adjustable to help control cycle times, so that the cycle time of the largest mold at maximum cooling determines the cycle for the carousel. The carousel typically runs on a 7-min cycle (1 min 15 sec/mold). The carousel line averages about 350 wheels per 8-hr shift.

The molds are poured by robotic ladling from the dip well of an 8000-lb dry hearth reverb. The computer-aided robot is preset, with each mold station individually programmed for pour time and casting weight. After pouring, the molds are automatically opened and the casting is removed by a robotic casting extractor. The average wheel casting weight of 45 lb includes the two side gates and the risers. The carousel production includes a cell-like arrangement featuring three operators. One worker oversees the carousel operation, a second performs hot inspection of all wheels and a third cuts the side gates. The wheels are immediately sent to a degating machine that removes the center and ring risers.

Like other aftermarket manufacturers, Ultra also produces a two-piece cast wheel. The wheel centers in the various designs are static cast individually, poured through a center riser (Fig. 3). The wheel outer rim is also gravity-cast, in all the different wheel sizes and widths (15 ft wheel x 5 in, 15 ft x 7 in, 16 ft x 8 in, etc.). After machining, the centers are pressed into the rims and welded. The two-piece wheel allows many customized options for the wheel buyer because the center can be placed in the rim with various depths to provide different looks for the same design. Approximately 20% of Ultra Wheel's current sales are two-piece wheels.

[Figure 3 ILLUSTRATION OMITTED]

Counter-Pressure Casting

As wheel designs become more complex, the casting of those designs also requires increased technology. Ultra began CPPM wheels last year when it installed four CPPM machines. Counter-pressure casting, like low-pressure permanent mold casting, draws the aluminum up into the mold cavity from the crucible underneath. In CPPM casting, both the metal bath and the mold cavity are pressurized. As pressure is slowly released from the mold cavity, the pressure difference draws the aluminum into the mold. Both the bath and the mold are held under a pressure of 4.5 bars. For most wheels, only about 0.5 bar pressure released from the mold cavity creates a sufficient pressure differential to draw the metal into the mold cavity through a steel filter screen. The process allows the rate of the draw to be varied with the casting design and size, and the precise metal flow control virtually eliminates turbulence. The casting then solidifies under 4 bars of pressure (about 60 psi).

The machines are entirely computer process-controlled and are "very demanding for precision," according to Ultra Wheel Foundry Manager Art Graciano, a veteran gravity pour wheel foundryman, who said that there is a learning curve with the new process.

"You can't rush," Graciano said. "You must be very precise or the downtime can be intensive. You must do it right from the start."

However, Graciano is now sold on the benefits of the system. Once you "control the human errors and efficiencies, the machines perform great," he said.

Each CPPM machine has an 800-lb crucible under the mold. The "up-tube" that draws the molten aluminum into the mold cavity is the only connection to the wheel casting--there are no gates or risers. The molds are air-cooled, and the machine itself has a water-cooling system to prevent overheating of the machine contact plates. The CPPM wheel castings average about 25 lb and are cast during a 5-6-min cycle (Fig. 4).

[Figure 4 ILLUSTRATION OMITTED]

Consistent cycle time is critical to maintaining quality for most permanent molds, and this is especially so with CPPM. To maintain consistent cycle time, Graciano and the Ultra staff have converted most of their high-volume jobs to CPPM to ensure long production runs. Where some castings might require slowing down production to assure care and quality, with these machines, "cycle time means productivity--and productivity means quality," according to Graciano. "Quantity makes quality because of the consistent cycle times."

By working with the mold-coating suppliers and machine manufacturer to achieve a long-lasting mold coating for these long production runs, Graciano and staff have achieved four to five day production runs without substantial coating retouch. That is, "if we do it right the first time," Graciano said.

Another reason to schedule long-running designs is the mold change process. Although the molds are prepared, coated and preheated to 50% of operating temperature before the mold change is initiated, the actual changing and mounting of the mold on the machine requires 30-45 min. With additional time to bring the mold to operating temperature, the total changeover time probably averages close to 2 hr.

While the gravity-pour line requires three workers to oversee the molding process (not including the furnace tender), the fully automated CPPM machines require only one worker to operate three machines. With each machine producing 10 wheels/hr, the CPPM line out-produces the carousel in efficiency (40-60% less time per mold) with less manpower. But beyond the efficiency, there are "immeasurable other benefits" of the system, according to Graciano. Because there is no gating or risers, the melt needs of the CPPM castings are almost 33% less than those needed for comparable gravity-cast wheels. While the average wheel weight (gating included) on the gravity-pour line is 45 lb, it is only 25 lb in CPPM (a difference of 5-6 lb in wheel weight alone). This reduction in metal need means less metal loss and less energy use, resulting in substantial savings, according to Graciano.

Adding to the reduction in metal due to the elimination of the gating system, the CPPM wheels can run with thinner walls than GPM wheels, reducing machine stock and machining time. The GPM wheels typically are cast with about 0.2 machine stock. The precision of CPPM molds and the uniformity of temperature in the mold due to the elimination of the risers and gates allows CPPM wheels to be cast with only about 0.05 machine stock per wall (0.1 overall--a 50% reduction in machining). Graciano further speculates that there may be no way to measure the ergonomic effects of handling a substantially lighter wheel throughout all the production and packaging stages.

Currently about 33% of the total foundry production is CPPM wheels. But management is so sure of the system that it has ordered eight more machines, due for installation this summer. CPPM may not be cost-effective for small order designs and Ultra Wheel will always use GPM for some jobs, but it envisions a slow reduction in GPM as it converts most of its wheels to CPPM.

Graciano and his staff have had to work on the downtime during refill of the crucible under the mold. The prepared molten aluminum is brought from the primary reverb melter to the machine casting station in a transfer ladle on a fork-truck. They originally started with about a 6-min refill time, but that meant disrupted cycle time that occasionally caused the drawtube to freeze up due to the cooling. Ultra developed a rail system for the transfer ladle that eliminated the fork truck during filling and helped decrease the fill time. This modification and other minor improvements, as well as diligence, have reduced the fill time to almost 3 min, so on some wheels they can actually refill without losing cycle time.

Wheel Finishing

Ultra Wheel heat-treats all its wheels at its facility. A complete CNC machine shop fully machines all wheels. Although painted wheels have long been a part of the industry, most car owners want the high-polished look. Ultra Wheel offers wheels that are polished (at its plant in Mexico) and chromed wheels.

Most of today's aluminum wheels are chrome-plated. Plated wheels are polished and etched prior to plating for best surface finish and adhesion. Ultra Wheel has its own plating facility that includes copper plating prior to the chrome-plating application. After plating, the finished wheels are packaged and distributed to retail outlets where America's automobile-loving public is waiting for the company's custom accessories.

RELATED ARTICLE: Ultra Wheel Co.

Buena Park, California

Sites; 2 (1 casting, 1 polishing).

Casting Data: 356 aluminum--grain-refined and strontium-modified; T-6 heat treatment; multiple designs of one-piece aluminum cast wheels, two-piece cast wheels (cast centers and cast rims) and cast caps (center hub covers).

Total Annual Sales: $50 million.

Annual Shipments: 391,000 wheels (1997).

Markets Served: Automobile aftermarket.

Processes: Gravity-pour permanent mold--on carousel with auto-lading and casting extractors; counter-pressure cast permanent mold; melting in gas reverbs; shell coremaking.

Value-Added Capabilities: Design and built tooling; machining; chrome plating; heat treating; polishing; painting; metallurgical lab; testing capability; distribution.

Size: 255,000-sq-ft manufacturing facility in Buena Park, California; 46,000-sq-ft polishing facility in Mexicali, Mexico.

Customers: General public through automotive specialty shops and tire/wheels dealers and automobile parts wholesalers.

Employees: Buena Park, California-280; Mexicali, Mexico-125.

Year Founded: 1985.

Staff Officials: President Jim Smith, General Manager Ron Schultz and Foundry Manager Art Graciano.

RELATED ARTICLE: Aluminum Wheel Forecast in the U.S.

Aluminum wheel consumption in the U.S. is expected to grow 48% over the next eight years, according to Ken Kirgin of Stratecasts, Inc., Fort Myers, Florida.

Based on the estimates of users, 17.2 million cast wheels, or 150,000 tons of castings, are consumed, and that number is expected to grow to 19.9 million wheels in 1998 and 29.4 million wheels in 2006.

Styled aluminum wheels are expected to grow in popularity due to their distinctive styling, the capability to restyle for model year differentiation, the reduction of un-sprung weight, brake cooling capability, lower investment cost, improved fuel economy, shorter lead time and the lucrative options for the automotive manufacturer.

Currently, demand exceeds the domestic supply of the wheels, and imports are expected to decline, according to Kirgin. Reasons for the decline in foreign imports include a decline in the value of the U.S. dollar, planned major expansion programs among domestic suppliers, Japanese transplants that use a higher domestic material content and the trend for foreign producers to locate facilities in the U.S. or Canada.

Cast aluminum wheels produced in North America are usually cast using the low-pressure permanent mold process. However, some wheels are produced with other casting processes including centrifugal, gravity permanent mold, diecasting and squeeze casting methods.