Glossary

To help site visitors understand the roll forming, corrugating, and metal fabricating processes, Corrugated Metals, Inc. has included this one-of-a-kind glossary.

ACCUMULATOR

A device which stores materials in a defined amount so a new coil can be installed and then welded to the old coil ensuring a non-interrupted material flow to the roll forming machine.

ANGULAR TOLERANCE

An angular tolerance of ±1° are typical in the roll forming process. See tolerance types.

ASTM

Stands for American Society for Testing and Materials.

AUXILIARY OPERATIONS

Operations outside the main roll forming process such as prepunching, embossing, curving and coiling, and cutoff. See embossing, pre-notch/pre-punch press, and pre-notching.

B-DECK

B-Deck is currently the most popular and widely used panel for decking. Type B-Deck or Wide Rib is frequently used for several applications such as flooring, siding, and roofing. The two main types of roof deck are B-Deck (HSB-36) or N-Deck (N-24). B-Deck is the most common type of roof deck and is typically used when spans are less than 10 feet. N-Deck is more commonly used in longer spans such as  8 feet to 16 feet.

BEND RADIUS

The inside radius of a formed feature. The bend radius should be equal to, or greater than, the material thickness. A small bend radius can create fracturing at the bend due to the natural thinning that does occur at the bend radius. Also called inside radius.

BENDING

Changing the shape of metal sheet using successive pairs of forming rollers. Bending does not change the thickness of the metal except at the bend radius where a slight thinning occurs. Generally applied to forming it is the creation of a formed feature by angular displacement of a sheet metal workpiece.

BLANKING PRESS

A blanking press is punch press used in a multi-step forming process. The blanking press forms a rough shape which then is subjected to one or more secondary forming processes to produce a finished component.

BLIND CORNERS

A blind corner is a bend in a roll formed piece that cannot be handled by direct roll contact.

BOW

Bow is the variation from a straight line in the vertical plane of a roll formed piece. It can be either cross bow or longitudinal bow. See camber, curve, and twist.

CAMBER

Camber is the variation of a side edge from a straight line, the gradual deviation from straightness of the edge of sheet or coil stock caused during the slitting operation. Camber is the edgewise curvature, a lateral departure of a side edge of sheet or strip metal from a straight line.

Extreme camber contributes to curve, bow, and/or twist in the finished part. See curve, bow, and twist.

CHANGEOVER TIME

The time it takes to change tooling. Long changeover times are costly due to lost productivity.

COIL

A length of steel wound into roll-form.

COIL BREAKS OR CROSSBREAK

Coil breaks are a defective condition composed of ridges or marks across the width of sheet or coil caused by improper coiling or leveling. Creases or ridges which appear as parallel lines, transverse to the direction of rolling, and which generally extend across the width of the sheet. A discontinuous curvature in the strip in the direction in which the material was rolled or uncoiled. Coil breaks are generally found in uncoiled hot rolled strip.

COIL SET

A lengthwise curve or set found in coiled strip metals following its coil pattern. A departure from longitudinal flatness. It can be removed by roller or stretcher leveling from metals in the softer temper ranges.

COILING

Coiling is the process of winding flat material while it is still hot as it exists the extrusion rollers at the mill immediately after it has been formed.

COILS

Sheet metal rolled from slab or ingot that has been wound into coiled roll. Coils are considered the most efficient way to store and transport sheet metal. Master coils are produced at the mill and slit coils are converted from the master coils in narrower widths through the
slitting process. See sheet.

COLD REDUCTION MILL

Sheet and strip are cold reduced to the desired thickness for the following reasons:

  1. To obtain the desired surface.
  2. To impart desired mechanical properties.
  3. To make gauges lighter than the hot strip mill can produce economically.
  4. To produce sheet and strip of more uniform thickness.

COLD ROLLED BASE

Coils that are cold worked or reduced to gauge on the tandem mill.

COLD ROLLED SHEET

A product manufactured from hot rolled, descaled (pickled), coils by cold reducing to the desired thickness, generally followed by annealing and temper rolling. If the sheet is not annealed after cold reduction, it is known as full hard.

COLD ROLLING

Term applied to the operation of passing unheated metal through rolls for the purpose of reducing its gauge.

COLD ROLLING MILL

A mill that reduces the cross sectional area of the metal by rolling at approximately room temperature.

COLD STRIP MILL

A mill that rolls strip without first reheating.

COLD WORK

Plastic deformation at such temperatures and rates that substantial increases occur in the strength and hardness of the metal visible structural changes include changes in grain shape and, in some instances, mechanical twinning or banding.

COMMERCIAL TOLERANCE

A range by which a product’s specifications can deviate from those ordered and still meet the industry accepted ranges (defined in ASTM Standards, etc.)

CONVENTIONAL OR STANDARD ROLL
FORMING MACHINES

Conventional or standard roll forming machines are more adaptable than the single-duty machines which allows the roll tooling to be used with other profiles to make it more able to handle a variety of production needs. See single-duty machines.

CORRUGATED METAL

Metallic coated sheet steel formed to a finished shape by passing the metal sheet through an engineered set of rollers by a metal fabricator. See corrugated metal revetment, roll forming.

CORRUGATED METAL REVETMENT

A military barricade designed to provide shelter or protection for humans and critical infrastructure assets against low angle high velocity fragments, shrapnel, and improvised explosive devices while offering protection as an anti-ram vehicle barrier. A corrugated metal revetment is made from some type of roll formed metal, typically heavy-gauge steel (16-gauge or 18-gauge). The corrugated metal revetment is also referred to as a bin revetment as is normally filled with sand or dirt.

CORRUGATING

The process of forming or ribbing a flat sheet of material into a consistent, symmetrical profile to increase that material’s strength to weight ratio up to 30% over the conventional material. The forming of sheet metal into a series of straight, parallel alternate ridges and grooves with a rolling mill equipped with matched roller dies or a press brake equipped with specially shaped punch and die.

CORRUGATIONS

Transverse ripples caused by a variation in strip shape during hot or cold reduction.

CROSS SECTION DEPTH

The distance between the peak and valley of a corrugation.

CURVE (ALSO REFERRED TO AS SWEEP)

Curve is the variation from a straight line in the horizontal plane measured after the part has been roll formed. Causes of curve included incorrect horizontal roll alignment and uneven forming pressure. See bow, camber, sweep, and twist.

CURVING

Curving is the process of adding curvature to a flat sheet by passing it through a set of rollers using multiple passes to gradually add curvature, radial bending, without kinking or creasing the sheet. Curing adds strength and functionality to a flat sheet.

CUT-TO-LENGTH

Process to uncoil sections of flat-rolled steel and cut them into a desired length. Cut-to-length product is normally shipped flat-stacked.

CUTOFF MACHINE

Mechanical or hydraulic equipment in the corrugating line which shears the material to length immediately following corrugation.

DOUBLE-HEAD MACHINES

Roll forming machines with two sets of housings and roll shafts mounted to face each other. These machines are popular in the shelving industry. These machines do not form the center of a panel effectively. See conventional machines, single-duty machines.

DRIVE SYSTEM

The system or method used to drive the roll forming unit. The five common methods include chain drive, spur gear drive, worm gear drive, square gearing, and universal drive depending on the type of roll forming machine used.

DUCTILITY

The ability of a material to be bent or otherwise formed without fracture. This is very critical in the roll forming process.

ELASTIC LIMIT

The maximum stress that a material will stand before permanent deformation occurs. See springback.

EMBOSSING

A process used for both decorative and functional purposes and typically performed prior to the roll forming operation. The decorative appearance is often a stucco or grained look.

END FLARE

End flare is the deformation at the ends of a roll formed part. End flare can be eliminated or at least reduced through using proper roll forming tool design. End flare is normally apparent after cut off and is caused by the release of residual forming stresses in material being roll formed, where one longitudinal end springs open and the other springs closed.

END JOINER

A system consisting of a shear and a welder used to connect the ends of the coils permitting a continuous strip of metal to enter the roll forming machine.

EXTRUDING

A process which shapes a piece of metal (typically nonferrous) by forcing the metal bloom, bar, or rod through a die of appropriate shape.

FERROUS METALS

Metals which are iron-based. See non-ferrous metals.

FORM

A bend in a material, or the actual process of bending a metal-formed part.

FORMING

The operation of converting a flat sheet metal workpiece into a three dimensional part.

FORMING ROLLS

Forming rolls are the tools that form the moving material through the roll forming machine.

FUNCTIONALITY

A term used to describe the degree to which the designed part will perform to meet its intended purpose.

GALVANNEALED

Steel sheet that is covered with zinc on both sides and immediately heat-treated so the coating becomes a zinc-iron alloy bonded to the surface.

HARD-ROLLED STEEL

Steel that was formed by rollers from a hot plastic state into its final shape. It is characterized by a rough, scaly surface.

HSB-36

HSB-36 stands for High Shear B Deck. Typically, B-Decking is used in short to medium span conditions ranging from 3 feet to 10 feet in distance for roof decking. B-Deck is 1 1/2″ deep and the panels are corrugated.

HYDRAULIC FRACTURING OR HYDROFRACKING (FRACKING)

Hydraulic fracturing, hydrofracking, or fracking is the process of drilling down deep and horizontally into the earth and injecting water and chemicals into rock layers which creates fractures in the rock. These fractures in the rock release petroleum, natural gas, or other substances that can be extracted at the surface.

INBOARD MILL

A roll forming machine with a housing only on one end of the roll tooling shaft. See outboard spindle support machines and inboard spindle support machines.

INBOARD SPINDLE SUPPORT MACHINES

Inboard-type roll forming machines have spindle shafts supported on only one end. Inboard-type machines are used for forming light-gauge products such as weather strips, moldings, and other simple shapes. See outboard spindle support machines and inboard mill.

INSIDE RADIUS

Another term for bend radius.

INSPECTION CRITERIA

The characteristics by which the part will be evaluated both dimensionally and cosmetically.

JIGS

Jigs are devices set up to control tooling configurations, and provide for repeatable production processes.

LEG

The leg is typically a 90% bend that is used for interconnection, mounting, or added structural support of the final product.

LENGTH OF THE LEG

A good rule of thumb is the leg length should be three times the thickness of the material.

LEVELERS

Mechanical devices used to ensure material fed to the punch press or roll forming machines is flat.

LOAD CAPACITY

Material type and thickness establish the load capacity that a given roll forming machine is required to generate.

MARKING

Marking is the reverse of engraving. As a product passes through the forming roller, a mark is “stamped” into the part.

METAL THINNING

The thickness reduction that occurs during any metal forming operation.

METALITH™

An engineered corrugated steel revetment, or bin revetment, barrier system designed as a blast mitigation and/or blast containment barrier.  The Metalith barrier system has also been certified by the Department of State as a K12 barrier, its highest anti-crash rating. The Metalith corrugated steel revetment system is made form 16-gauge and 18-gauge steel panels. See corrugated metal revetment.

NET SHAPE

Net shape refers to the final dimensions of a product that results after the corrugating or roll forming operation is complete. Typically, the final finished net shape is a reduced size compared to the initial shape.

NON-FERROUS METAL

Metals or metal alloys that do not contain any iron.

NOTCHES/PUNCHED HOLES

Punching dies are incorporated directly into the roll form line to allow notches and holes to be punched during the roll forming process. Place part holes at least three to five times the material thickness past the bend radius.

OIL CANNING

Oil canning is defined as visible waviness in the flat areas of metal roofing and metal wall panels.  Oil canning cannot be a cause of rejection.

OUTBOARD MILL

A roll forming machine with housings that support both ends of the roll tooling shafts. See outboard spindle support machines, inboard spindle support machines, and inboard mills.

OUTBOARD SPINDLE SUPPORT MACHINES

Outboard spindle support machines have spindle shafts are supported by housings at both ends. Outboard machines can be easily set up to handle any width of material by making the spindle lengths to suit the material width. See inboard spindle support machines.

OUTSIDE RADIUS

The formed outside radius of a bend. See inside or bend radius.

PART LENGTH

The length of the cut metal part. Design for cutoff so the shortest length for precut parts is no less than twice the horizontal center distance between roll forming stations.

PLASTIC DEFORMATION

The permanent deformation that occurs in the forming of metal after the elastic limits have been exceeded. See elastic limit and springback.

PICKLING

Pickling is name given to the process of cleaning a steel coil through a series of hydrochloric acid baths that remove the oxides (rust), dirt, and oil so that further work, such as roll forming, can be done to the metal.

POST-CUT ROLL FORMING

A roll forming process that uses continuous rolls of metal and does not cut the piece to size until after it has been roll formed. This process is the most common, efficient, consistent, and least troublesome roll forming method. See precut roll forming.

PRECUT ROLL FORMING

A roll forming process that uses material that has been cut-to-length before entering the roll forming machine. This method is primarily used for low-volume applications. See post-cut roll forming.

PRE-NOTCH/PRE-PUNCH PRESS

A device used to stamp a hole or notch pattern in incoming material on a roll forming line prior to roll forming.

PRE-NOTCHING

The process of placing notches or punches into a metal sheet or roll before the roll forming process.

PRE-PUNCH OR PRE-NOTCH TABLES

A table used to support material exiting a punch press before it enters the roll forming machine. See runout table.

PRESS BRAKING

A process that typically includes metal being manually fed by an operator who then holds a metal workpiece between a punch and die and against a gauge to provide a pre-set bend or series of bends in the metal, making it ideal for producing bent parts such as enclosures and cabinets.

PRODUCTION SPEED

The speed the metal sheets or rolls as they are passed under the roll forming rollers typically measured in feet per minute. Most roll forming equipment used in the US averages a production speed between 100 to 180 feet per minute.

PROTOTYPE

The first part of a design which is made to test tolerance capability, tooling concepts, and manufacturability of the intended production part.

PUNCHING

The process of piercing a metal product to a desired design. See notching and notches/punched holes.

REEL BREAKS

Fractured base metal normally caused by poor leveling. It is indicated by light kinks across the width of the winding coil.

REEL KINKS

Damage on the strip in the core of a coil.

ROLL CHANGING

The process of changing the rolls in a roll forming machine. This process is time consuming and costly.

ROLL FORMED SHAPE, HOLLOW

A roll formed shape that is closed by mechanically fastening or welding the two strip edges together.

ROLL FORMED SHAPE, OPEN

A roll formed shape with a linear or curved contour in which the two ends of the shape are not brought together.

ROLL FORMING

Is a continuous metal forming process taking sheet, strip, or coiled stock and bending or forming it into shapes of essentially identical cross section by feeding the metal between successive pairs of rolls that increasingly shape it until the desired cross section is completed adding both strength and rigidity to lightweight materials.

ROLL FORMING MACHINE

A machine capable of press metal sheet or roll through two sets of rollers to form materials with nearly identical cross sections.

ROLL FORMING METALS

The roll forming process can handle a wide variety of metals including ferrous, nonferrous, hot rolled, cold rolled, polished, plated, and pre painted metals.

ROLL FORMING TOOLING

The tooling used in roll forming includes the forming rolls and the dies for punching and cutting off the material.

ROLL STATIONS

Tandem sets of rolls used in roll forming to shape the metal stock in a series of progressive stages to form the desired cross-sectional configuration.

RUNOUT TABLE

A table designed to handle the roll formed part after it has been cut off. See pre-punch or pre-notch table.

SECTION SHAPE

The final profile of a roll formed piece. A complex shape may require multiple passes through the rollers to roll form the section correctly.

SECTION WIDTH

The width of the roll formed section or the width of the piece or roll to be roll formed.

SHEET

A wide, but thin (down to .05″), flat rolled metal mass in widths typically provided in widths from 24″ to 80″. It can be sold either in cut-to-length pieces or rolled into large, heavy coils. See coils.

SINGLE-DUTY MACHINE

A single duty machine is a roll forming machine built and designed to process one specific profile or one set of roll forming tooling. Single duty machines are not designed for convenient roll changing. See conventional machines.

SLIT EDGES

The edges of sheet or strip metal resulting from cutting to width by rotary slitters.

SLITTING

(1) The process of taking the wide rolls or sheets provided by the mills and cutting them down to narrower width strips or rolls by service centers to meet the needs of their customers, such as roll formers.
(2) Cutting or shearing along single lines to cut strips from a sheet or to cut along lines of a given length or contour in a sheet or workpiece.
(3) Cutting sheet or strip metal to width by rotary slitters.

SPRINGBACK

A condition of a roll formed piece that occurs when the material to be formed has not been stressed past its elastic limit. See elastic limit.

STAINLESS STEEL

Corrosion resistant steel of a wide variety, but always containing a high percentage of chromium. These steels are highly resistant to corrosion attack by organic acids, weak mineral acids, atmospheric oxidation, and other corroding materials.

STAMPING

A metal fabricating process that can compete with roll forming that presses a metal blank with powerful dies into a predetermined shape (or pattern). Stamping utilizes mechanically or hydraulically powered presses that are fed by continuous strips of metal or individual blanks. The strips or blanks are positioned in the press and shaped between tooling forced into the materials by a powerful stamping action.

STATION CONFIGURATION

The term used to describe how the individual roll forming units are mounted. The station configuration usually determines the type of shapes that can be formed on that machine. There are six basic station configurations. They are single-duty machine, conventional/standard machines, and double-head machines.

STEEL

Iron, malleable in at least one range of temperature below its melting point without special heat treatment substantially free from slag, and containing carbon more than about 0.05% and less than about 2.00%. Other alloying elements may be present in significant quantities, but all steels contain at least small amounts of manganese and silicon, and usually as undesirable constituents, also sulfur and phosphorus.

SWEEP (ALSO KNOWN AS CURVE)

Sweep is the variation from a straight line in the horizontal plane measured after the part has been roll formed. Causes of sweep included incorrect horizontal roll alignment and uneven forming pressure. See bow, curve, camber, and twist.

THICKNESS

The gauge or depth of a material.

TOLERANCE

The permissible variation from a specification for any characteristic of the product.

TOLERANCE TYPES

In the roll forming process four types of tolerances are routinely measured including dimensional cross-sectional, length, angular, and material straightness.

TOOL LONGEVITY

The time a tool lasts before it must be replaced since it can no longer hold the required tolerances. Long-lasting tools are made from high-carbon, high-chrome hardened tool steel.

TRUCKLOAD OR TRAILER LOAD

A quantity of commodities, including primary and secondary metals, weighing as much as 44,000 pounds, the standard weight limit on U.S. highways.

TRIMMING

Removing excess metal from a sheet to slightly adjust width or length dimensions. Cutting scrap off a partially or fully shaped part to an established trim line.

TWIST

Twist is a term used to define parts when they resemble a corkscrew effect. This is often caused by excessive forming pressure in the final formed part. Twist should be less than 5° in 10 feet of roll formed parts. See bow, curve, camber, and sweep.

UNCOILER

A device that supports the coil while allowing the material to be fed into the roll forming machine without causing extreme drag and overrun.

WHEELING CORRUGATING COMPANY

A now defunct manufacturer of roll formed products for residential, agricultural, construction, highway, and bridge building markets.  Wheeling Corrugating Company offered roofing and siding products, as well as decking products, including composite floor decks (B-deck), steel roof decks, and form decks. It also provided highway products, such as bridge forms and heavy duty steel systems for forming concrete bridge deck slabs; and painted coil products for HVAC, doors, lawnmower decks, light fixtures, ceiling grids, stove pipes, and shelving applications. Wheeling Corrugating Company was founded in 1890 was based in Wheeling, West Virginia and closed its doors in 2012.

YIELD STRENGTH

The maximum stress that can be applied to a material without permanent deformation of that material.

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