Forging: A Competitive Advantage
Product manufacturers can gain competitive advantages by using forgings--product design flexibility, unmatched product strength, extended service life and consistent quality. A "mature" industry, forging remains an integral part of evolving technologies and continues to adapt to the demands imposed by global competition.
In a recent issue of Design-2-Part Magazine, a discussion of forging begins with reference to old images commonly associated with the process: Primitive Man and The Village Smithy. As has every other manufacturing technology, forging has evolved. Forgers continue to develop new CAD/CAM applications, precision forming technologies and novel methods of technology transfer--putting to rest the industry's "old-fashioned" image.
Product manufacturers can look to forging to improve product design and quality and reduce overall manufacturing costs. In the fierce (and now global) struggle for competitive advantage, the forger can prove to be a worthy ally.
Forging advantages lie mainly in product integrity and production economy.
A forging's structural integrity surpasses that achieved in any other metalworking process. Forging produces a grain flow oriented to part shape; resulting in optimum strength, ductility and resistance to impact. By virtue of the process and controls used to produce them, forgings are dimensionally stable with consistent service properties, part to part.
Forgings can offer decisive cost advantages, especially in high-volume production runs. Forged parts, especially near-net shapes, make better use of material and generate little scrap. They also require less machining and labor time. Properly designed, a forging can replace an entire multicomponent assembly. Such part consolidations can reduce costs considerably.
The forging industry now enters a phase of innovation; using new computer-assisted engineering tools to predict process and enhance product design; implementing automated systems to improve production; and aggressively promoting the technology to offer users and potential users new methods to make better products at lower prices.
CAD/CAM and other computer aided engineering tools help forgers enhance product design, improve quality and economize production.
The use of computers and CAD/CAM analysis has increased significantly in the forging industry over the past 10 years. Now even smaller custom forging companies run analysis software and CAD/CAM systems on personal computers
Forgers are using computer-aided engineering tools to assist forging die design and production as well as press, heat treating, machining and material handling operations. New engineering tools have helped forgers reduce lead times, improve part-to-part uniformity, optimize heat treating and expedite machining.
A good example of CAD/CAM application to forging is metal flow simulation (MFS) software. Although currently used by relatively few custom forgers, MFS is making enormous strides in the industry.
MFS predicts what is going to happen throughout the entire forging process; material movement and flow, pressures, temperature profiles, die strains and strain rates.
Also under development are systems to help "forge it right the first time" tools to help engineers determine the process variables involved in designing dies for a desired forged shape. This type of computer-aided die design can yield even greater economies and may possibly eliminate costly and time consuming "cut and try" die trials. Still, solid modeling techniques (forming plasticene in acrylic dies, for instance) often provide important verification of the results of analytical procedures, for added confidence before hard metal is cut.
Use of microalloyed steels is an innovation that offers greatly enhanced material properties, many new applications and notable production cost savings.
Microalloyed steels are used most successfully to reduce the need for heat treatment after forging. Small additions of vanadium, columbium, and other elements can greatly strengthen plain carbon grades of steel. These materials can be used to forge such parts as crankshafts, connecting rods and front axles.
Now under evaluation and test is a controlled thermo-mechanical process using microalloyed steels to optimize strength and toughness properties in the forged part without heat treating. A number of forging suppliers to major American equipment and automotive manufacturers report that costs can be reduce via this technology.
Microalloyed steel forgings can cost 15 percent less before machining than heat-treated equivalents. Even greater cost reductions are achieved when normalizing is ordinarily specified before quenching and tempering or when post heat-treat straightening and stress-relieving are otherwise required.
Warm forging has a number of economical advantages; lower energy costs, reduced tooling and press loads, controlled material flow and increased material ductility in addition to elimination of pre-forge annealing and heat treatment.
This process combines the advantages of both cold and hot forming and eliminates the principal disadvantages of both. In the warm forging process, billets are cleaned prior to being heated in an induction system designed to utilize inert atmospheres. As is the case with forging microalloyed steel, subsequent heat treatment often can be avoided.
A newly-developed warm forging technique involves using electric induction heating to achieve accurate temperature control, uniform heating, and good surface finish, while applying loads over small areas of the billet to maximize forming pressures.
By strictly controlling billet size and process pressures and heat, this technique has virtually eliminated flash the flow of excess material outside the die cavity--and consequently the need for secondary part trimming.
The process has been used to make a wide range of parts including constant velocity u-joints, bevel pinions, sliding clutch gears and gun barrels.
To the product manufacturer, warm flashless forgings offer great competitive advantages. Improved surface finish of the as-forged part virtually eliminates the need for secondary machining. Tighter dimensional tolerances reduce assembly time and cost. Most significantly, the lower energy costs of the new method, in turn, reduce part costs.
Precision forgings--used primarily in aerospace but rapidly finding new applications in other industrial markets--require little or no machining other than drilling of attachment holes. Terms such as "no draft forging," "close to form" and "net forging" all refer to precision forgings.
Studies have shown that, compared with shapes machined from plate, precision forgings can reduce part cost by 80 to 90 percent and slash machining labor by as much as 95 percent. If there are areas where the standard +0.020/-0.010 in. tolerance is insufficient, minimal machining may be employed.
Compared with conventional closed die forgings, precision forgings can cut final part cost by 60 to 70 percent, reduce machining labor by up to 90 percent and save critical materials.
As a result of the potential savings, many aerospace companies are investing "up front" in the required engineering and tooling in order to use precision forgings instead of costlier production procedures.
Increased size capabilities have reinforced this trend. In the 1950's, size limitation deterred development of aluminum precision forgings. Practical plan view area (PVA) capabilities currently are at 400 sq. in. and efforts are aimed at PVA of 600 to 650 sq. in.
Advances in hot die forging equipment and techniques are critical to continued development of precision forging.
Hot die forging reduces material resistance to deformation by heating the dies to a temperature close to that of the material to be forged. With unit pressures in the range of 35 to 75 tons per sq. in., hot die forging needs sophisticated die materials in order to reach the desired temperatures. As with warm flashless forging, close control of presses and die temperatures enhances productivity and product uniformity.
An important benefit of hot die forging is its effect on forged product properties, such as improved strength and fracture toughness and low cycle fatigue.
These benefits have been achieved, in part, by virtue of control and press equipment upgrades. According to one industry source, three years ago there were only two presses above 3500 tons making precision forgings in the U.S. Today, there are 14, with capacities ranging up to 10,000 tons. Presses are programmable and equipped to control speed, pressure, position and strain rate.
Support facilities are also being upgraded. Heating, material handling and trimming equipment can be organized into flexible manufacturing system cells. In some forges these FMS cells are driven by CAD/CAM techniques.
Today, product manufacturers can demand and get ever higher levels of service from forgers. Not the least important of which is assistance in product design and development which expedites transfer of forging technology to new industrial segments.
To fulfill demand, the industry is literally "taking its show on the road." In 1988, the Forging Industry Association will hold a series of technology clinics to update production manufacturers on new forging developments.
Under the rubric of "Focus on Forging," the series will present and analyze current forging technology; processes; material and production innovations; new CAD/CAM applications in forging design and production; "textbook" case histories of users who have specified forgings and gained advantage of enhanced product quality and reduced manufacturing cost.
Maturity and longevity are the distinguished marks of quality and these terms apply, appropriately, to the forging industry.
As the industry continues to develop in its current phase of innovation, product manufacturers can look to forgers to provide services--advanced product/process design and production capabilities--and products that are essential to achieving and maintaining competitive advantage in domestic and foreign industrial markets.
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