Fabricated Metal Products Industry
This group contains establishments engaged in manufacturing metal products. Its industries include:
-Metal Cans and Shipping Containers
-Cuttery, Handtools, and General Hardware
-Heating Equipment (except electric and plumbing)
-Fabricated Structural Metal Products
-Screw Machine Products (bolts, nuts, screws, and rivets)
-Metal Forgings and Stampings
-Coating, Engraving, and Allied Services
-Ordnance and Accessories (except vehicles and guided missiles)
-Miscellaneous Fabricated Metal Products
Forming: Formation of metal is extensive in this group because actual finished products are desired.
CASTING is one of the oldest and most common methods of forming. It requires the melting of a solid, heating it to the proper temperature, treating it to produce a desired chemical composition, and then pouring it into a cavity or mold for solidification. A wide range of sizes and shapes are possible with casting including large and bulky to small and detailed products. Some common casting processes include:
Some machining is required in casting processes to remove cores, gates, fins, left by air holes in the molds. Casted pans offer the best resistance to working stresses because they are melted for forming and not mechanically worked.
POWDERED METALLURGY is a material formation process that is similar to casting in that some type of mold is used. Fine metal powders are blended, pressed within a mold, and then heated or sintered. Powdered metallurgy is used for its ability to produce many complex shapes in one step. Machining is many times unnecessary for a part produced with powdered metallurgy. Melt atomization and electrolytic deposition are the most common processes used to produce the often expensive metal powder.
Hot working forming processes require that the material be mechanically worked or deformed when heated. Hot working is attractive because it is very easy to shape materials at higher temperatures. Massive deformation is available without sacrificing much strength. Some disadvantages include the need for machining after the process and the presence of poor dimensional accuracy.
ROLLING is usually the first step in converting cast products (such as ingots) into finished wrought products. It consists of passing heated metal between two rolls that revolve in opposite directions, the space between the rolls being somewhat less than the thickness of the entering metal. Rolled products have minimum directional properties; this means that they aren't strong in one direction and weaker in another. Heat treatment can also be performed along with rolling; this is referred to as controlled rolling.
FORGING is the plastic working of metal by means of localized compressive forces exerted by manual or power hammers. Forging is used to maintain or increase strength, while shaping a part. Common forging processes include:
EXTRUSION requires that the material be compressively forced to through a suitable shape (called a die) to form a product with reduced cross section. The extrusion process is like squeezing toothpaste out of a tube. The two types of extrusion used in hot working are direct and indirect. In direct extrusion, a ram pushes the material through the die. In indirect extrusion, the ram pushes the die back around the material.
DRAWING is a plastic forming process in which a flat sheet or plate of material is formed into a recessed, three-dimensional part with depth several times the thickness of the material. Hot drawing is used, primarily, for forming thick-walled parts of simple geometry. An example of drawing is the production of metal cans and containers.
Other hot working processes include HOT SPINNING, PIPE WELDING, and PIERCING. Hot spinning is the plastic forming of parts from a flat rotating disk of metal. Pipe welding is the forming of metal strips into seamed pipe and the use of the heat contained in the metal to weld the seam. Finally, piercing is the production of thin walled, seamless tubing by center punching solid, circular stock with a bullet like tool.
Cold working forces require the material to be mechanically worked or deformed cold. Such processes are advantageous because they provide good dimensional accuracy and good surface finish. Greater forces are required to cold work, and there are also losses in strength. However, machining can sometimes be eliminated with proper working.
SQUEEZING is a forming process where the material is forced to compact. It is used to produce features such as sudden tapers, rounded ends, and thinner sections. Numerous cold worked products include nuts, bolts, and nails. Common squeezing techniques include:
BENDING requires deformation of the workpiece about a linear axis. It is used to form metal to numerous geometric shapes such as right angles, rounded corners, and tight seams. Common bending applications include:
SHEARING is a mechanical forming process for metal sheets or plates where material is cut without the formation of chips or the use of burning or melting techniques. Shear forces are applied to produce dislocations along grain boundaries of the material. Common shearing applications include:
DRAWING is a forming process where plastic (permanent) flow occurs over a curved axis. A good way to envision drawing is taking a flat sheet of material and using a punch to push a cup-like shape from the sheet. Some common drawing techniques include:
Machining: All of the industries in this major group use machining processes. Machining deals with removing material (usually in the form of chips) so as to obtain a finished product of desired size, shape, and finish. Machining that does not produce chips is classified as non-traditional machining.
SAWING produces chips by a succession of small cutting edges or teeth arranged in a narrow line on a saw blades. Saws can be classified into three distinct types; reciprocating, band, and circular.
MILLING is a type of cutting process where a surface is generated progressively as it is fed to a rotating tool in a direction perpendicular to the tool motion. It differs from sawing in that the tool is much thicker than a narrow blade. Milling is often used to produce patterns of lumber, plastic, and metal. Milling is faster than sawing, but it often leaves surfaces that are too rough for many applications.
OXYGEN TORCH cutting uses oxyfuel gas to cut metal, wherein the material is actually melted by the flame. It is by far the most used means of cutting metal. Acetylene, propane, and natural gases, mixed appropriately with oxygen, are used as fuel for the torch.
ARC cutting uses an intense electrical arc to melt metal and force it to flow. Types of arc cutting include; oxygen, air carbon, gas metal, and plasma.
LASER BEAM cutting uses intense heat from a focused laser beam to melt and/or evaporate the metal. T aver cutting devices are used for their ability to make precise cuts with little material waste. It is often difficult, however, to cut thick metal in a laser cutting process.
WATER JET machining removes material through erosion effects of a high velocity, small diameter jet of water. It is commonly used for cutting and slitting of wire, and for cable stripping. Abrasives can be added to the water to handle stronger materials.
SHAPING is the simplest form of machining relative to motion. It uses a single point cutting tool that moves in a straight line across the workpiece. Types of shaping include horizontal push and pull, and vertical cutting. A variety of tool geometries can be used to create many different shapes.
PLANING has the workpiece move past a single point cutting tool (the opposite of shaping). It is a simple form of machining that has its limitations due to slow feed rates and low productivity. It can be used to produce shapes from different tool geometries and reduce thickness of metal when appropriate.
TURNING is a high speed process where the workpiece rotates and a longitudinally fed, single point tool does the cutting. Variations of turning include tapering, facing, and boring. Turning requires the use of a lathe except in some boring operations. Multiple diameter poles and rods are easily produced in a turning process.
DRILLING uses a rotating tool with two edges that is pressed into the workpiece to produce a hole or void. Types of drilling tools include; straight and taper shank, deep hole, combination, subland, and spade. Feed rates depend on the type and thickness of the material. Drilling is often followed by counterboring or countersinking to accommodate fastening devices.
REAMING is a process that can only follow a drilling or drilling related process. It uses a multi-edged cutting tool (often on the same machine used for drilling) to bring holes to a more exact size. Types of reamers include; hand, machine, shell, expansion, and adjustable. Common drilling machines used for reaming include; upright, radial, gang, deep-hole, and transfer.
BROACHING uses a tool (called a broach) that contains a series of circular, single point, cutting edges around a bar that gradually increases in diameter. This process is unique in that the feed rate is determined by the tool. Types of broaching include; roughing, sizing, and burnishing. Metal is the typical work material for a broaching process.
FILING requires cutting teeth arranged in succession along the same plane on the surface of a file to remove material chips. Types of files include; single-cut, double-cut, vixen-cut, and rasp-cut. Files are also classified by coarseness and construction. Filing is important to furniture industries in easily removing sharp edges that could cause injury in finished products.
ABRASIVE machining uses very small cutting edges that are integral parts of abrasive particles to produce chips from the material. A good example is using sandpaper to smooth a rough surface. Types of abrasives include; quartz, aluminum oxide, silicon carbide, and diamond. Some common types of abrasive processes include grinding and lapping. Grinding uses a wheel of some shape on which abrasives are bonded. Lapping requires that fine particles be embedded into a soft material (like paper) which serves to finish the part. Abrasive machining is limited to small amounts of metal removal. However, it can provide extremely smooth surfaces.
ABRASIVE JET machining removes material through the action of a focused stream of abrasive laden gas. Common abrasives include; aluminum oxide, silicon carbide, sodium bicarbonate, and glass beads. AJM is used to debur plastic parts, deflash small castings, and touch up molds. AJM is very cheap and good for difficult to reach areas. It can machine very hard materials, but it has a slow material removal rate. Stray cutting may occur, along with the embedding of particles in the workpiece.
CHEMICAL machining is classified as non-traditional machining in that it doesn't produce chips. It employs some type of chemical reaction (sometimes enhanced by electrical or thermal energy) to remove material. Chemical machining often take the place of processes such as deburring, grinding, and polishing.
ULTRASONIC machining is a material removal process used to erode holes and cavities in hard workpieces. It uses shaped tools and high frequency mechanical motion. Another form of ultrasonic material removal is the stripping of finishes via underwater ultrasonic wave emission.
Assembly: The actual putting together, joining, and additional finishing of components constitutes assembly. Not many processes define a fashion in which parts and components are put together, it's just done in (hopefully) the fastest, most efficient manner. Once together, there has to be a means of joining the components. Other materials may be assembled onto primarily metal parts in this group.
WELDING is a process where two materials (usually metals) are permanently joined together through localized coalescence. Weld quality and strength depend on a combination of temperature, pressure, metallurgical conditions, and skill of the welder. Various forms of welding include:
SURFACING is the deposition of a layer of metal or other material upon the surface of some base metal. The layer of material can be applied with nearly all gas flame and arc welding methods.
METALLIZING is the surfacing of a base metal by melting and atomizing material in a special torch and spraying the resulting liquid onto a surface. Metallizing is used to protect, harden, reflect, and provide electrical conductivity.
BRAZING is the joining of metal components through the use of heat and filler material whose melting temperature is above 450 degrees Fahrenheit, but below the melting point of the metal to be joined. Common fillers include; brass, bronze, copper silicon, and silver alloys. Brazing is not as strong as welding, but can be used on virtually all metals. Less heat is required than welding, and brazing iS good for mass production.
SOLDERING is the joining of metal components through the use of heat and filler material whose melting temperature is below 450 degrees Fahrenheit. Common fillers include; lead alloys and aluminum. Dip type soldering is used extensively when many parts can be joined at once. Soldered joints are weaker than brazed joints, but less heat and effort are required to perform soldering.
ADHESIVE BONDING uses composite systems with several compounds to join two surfaces together. The bonding material may exist as liquids, pastes, solids, tapes, or films. Common types of adhesives include:
The surfaces of all components to be joined must be clean and dry to insure proper bonding.
MECHANICAL FASTENING requires that a joint be formed by mechanically interlocking or interfering with no fusion or bonding present. Fastener types include integral and discrete. Integral fasteners are machined areas of metal such as tabs and seams that fit into other parts. Discrete fasteners are separate pieces such as nails, bolts, screws, rivets, and wires.
COATING is performed to impart certain properties to surfaces - ^h as resistance to weather and wear, different colors, and smoother finishes. Coatings can be classified into organic and inorganic types. Common coatings include paint, enamel, anodization, and plastic laminations.
Inspection and Testing: Most of the processes already described in the fabricated metal products group occur at only one point in the overall manufacturing path. Inspecting and testing, however, are performed numerously throughout all processes. It can consist of a simple check to see if a piece is present, or a minute measurement of the surface of a finished part. Inspection and testing tell whether or not a particular process was performed adequately.
DESTRUCTIVE TESTING does not allow for use of the tested part after inspection because it imparts some type of mechanical deformation. This type of testing is done on a sampling basis. Other types of destructive testing include fatigue, impact, creep, torsion, and shearing.
NON-DESTRUCTIVE TESTING allows for use of the part after inspection. It includes a wide range of optical and mechanical techniques. Mechanical techniques using instruments such as calipers, micrometers, and scales may contact the part, but they leave no significant mechanical deformation. Optical techniques include structured light, triangulation, holography, and interferometry. An example of a NDT application is the use of an optical surface profiler to map surface finish.