Roll Forming Technology Terminology Guide

Fabricators & Manufacturers Association, Intl.

Roll Forming Technology Council

Copyright 2008

This guide was created by the Fabricators & Manufacturers Association, Internationals Roll Forming Technology Council to help increase the terminology knowledge of those working in the roll forming industry. The council will continue to expand as new and updated information becomes available.

The council encourages the reader to submit additional terminology for consideration by sending an e-mail to any of the members listed on the next page or through the FMA website www.fmanet.org

FMA ROLL FORMING TECHNOLOGY COUNCIL

Paul Williams - Chair Mgr. Formtek Sales for Hill Engineering Hill Engineering 373 Randy Road Carol Stream, IL 60188 630-834-4430 630-834-4755 pwilliams@formtekgroup.com

Scott McMeekan Vice Chair President Ferret, Inc. 28459 Laura Ct Elhart, IN 46517 574-295-1482 574-293-9994 scott@ferretrollforming.com

Kevin Dierking Engineering and Technology Manager Roll Forming Corporation 1070 Brooks Lane Shelbyville, KY 40065 502-633-4437 x262 502-633-5824 kdierking@rfcorp.com

Steve Ebel President Roll Form Solutions, Inc. 1130 E. Mt. Garfield Road Muskegon, MI 49441 231-799-9551 231-799-9559 steveebe@rollformsolutions.com

Brett Krause Metallurgical Services Gerdau AmeriSteel 1500 West 3rd Street Wilton, IA 52778 563-732-4571 BKrause@GerdauAmeriSteel.com

Dale Kroskey VP - Roll Forming Technology Metalforming, Inc. 100 International Drive Peachtree, GA 30269 678-554-2185 770-631-7776 dkroshey@metalforming-usa.com

Kirk McCubbin President and CEO Tower Oil & Technology, Inc. 205 West Randolph Street Chicago, IL 60606 773-927-6161 773-927-3105 kirk@toweroil.com

Al Patty Corporate Manager, Roll Form Engineering Dietrich Industries, Inc. 1435 W. 165th St. Hammond, IN 46320 219-931-3741 219-853-9467 apatty@dietrichindustries.com

Brian Rodgers Roll Forming Corporation 1070 Brooks Lane Shelbyville, KY 40065 502-633-4437 502-633-5824 brodgers@rfcorp.com

Jim Rosasco VP - Diversified Products Shape Corporation 1900 Hayes Grand Haven, MI 49417 616-847-8700 616-846-3464 rosascoj@shape-corp.com

Charles Summerhill VP - US Operations Roll-Kraft 8901 Tyler Blvd Mentor, OH 44060 440-205-3100 440-205-3110 csummerhill@roll-kraft.com

Paul Tiefentahal Vice President, Engineering Tru-Tech Tool and Machine Corp. 1030 Gateway Blvd Muskegon, MI 49441 231-798-7237 231-798-3628 paul.t@trutech-rollform.com

David Voth Product Line Manager - B&K Systems Formtek Metal Forming, Inc. 4899 Commerce Parkway Cleveland, OH 44128 216-360-7682 216-831-7948 dvoth@formtekcleveland.com

Rollforming Terminology

Accumulator: A device that 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 is typical in the roll forming process.

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. Back Bend: A process the roll designer may use to allow for more bending in a specific area to help control flatness or assist in getting more bending into a corner because of a blind corner condition.

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: When the product is designed in such a way that the roll tooling cannot cover the bend points or radius of the cross section on either the male or female portion of the roll. 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.

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.

Centerline side rolls: Side rolls that work in conjunction with the forming rolls of a given forming station. Usually mounted on custom designed brackets that straddle the roll shafts of the station, their primary function is to either access the inner forming corners that have become inaccessible using the main forming rolls, or to support the outer surface of the vertical feature of the profile to prevent scuffing of the material. Another term used to describe these rolls is cluster side rolls.

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 a coil form. Typically 16-20 ID x 60-72 OD.

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 exits 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.

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.

Combination Tooling: This is the term used to describe roll form tooling that has been designed with the ability to make more than one cross section.

Commercial tolerance: A range where a product's specifications can deviate from those ordered and still meet the industry accepted ranges (defined in ASTM Standards, etc.) Constant Radius: In the constant radius method, the form radius of a bend is constant from pass to pass. Since a smaller angle bend uses less material than a larger bend of the same radius, there is extra material in any incomplete bend. This extra material is added to segments on either side of the bend. The simplicity of these radii made it very common on rolls cut on engine lathes. The constant radius development method usually gives a more broken or choppy radius and is therefore less used today than in the past.

Conventional or standard roll forming machines: Conventional or standard roll forming machines are more adaptable than single-duty machines and allows the machine to be used for a variety of other profiles (roll sets). 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.

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: This term describes the geometric shape around the outer perimeter of the product being roll formed. 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.

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 and/or 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, pneumatic or hydraulic equipment in the roll forming line which shears the material to length immediately following forming. Dove Tail: This describes a specific shape that is triangular in appearance and is within the cross section of the roll formed shape.

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.

Dual Head or Duplex Roll Former: This machine is built with two separate heads, with one side fixed stationary and the other side adjustable to accommodate product width changes without changing roll tooling.

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.

Embossing: A process used for both decorative and functional purposes and is 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.

Entry table: A guide stand that mounts prior to the first forming station and is adjusted to guide the strip or coil properly into the rolls.

Equal and Unequal Gearing: Roll form machines are typically built with equal gearing on the drive; however, when a section that will be roll formed is unusually deep or may have drive problems, the roll former manufacturer may elect to change the gearing on the drive to help reduce roll fight and galling.

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.

Finish Pass: This refers to the final forming pass or passes of the set of roll tooling that is made to the final product dimensions.

Fixed Gear: This term refers to a specific way a roll form machine gearing is set up to allow for an adjustable vertical range of about 1.5.

Flower: A drawing or layout showing a cross-section of the strip at each forming stage or station. Generally used during the design stage to determine the number of passes required to form the product, the drawing shows all the cross-sections layered together to review and revise the forming flow, prior to design of the tooling.

Form: A bend in a material, or the actual process of bending a metalformed part.

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

Forming rolls: Forming rolls are the tools which forms 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.

Hem: This refers to the condition when the material is roll formed back onto itself, sometimes with and sometimes without any air gap.

Horizontal Centers: The distance between the centerline of a shaft on one station to the centerline of the shaft on the next station is referred to as the machines horizontal centers.

Inboard: Term used to describe the gearbox side of the roll-space. A.K.A. Back side

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 Spacers: The spacers that go between the mill face alignment spacers and the roll tooling.

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 at least 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.

Lift Angle: This term refers to amount of bending that will be done in each pass of roll tooling.

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

Lock Seam: Refers to the mechanical locking of the outer edges of the material being roll formed together.

Machine Face Alignment: This is the alignment of the mill face alignment spacer or shaft alignment shoulder from pass to pass and top to bottom.

Machine Face Alignment Spacers: The innermost spacer that is up against the shaft hub in which the machine alignment is made.

Mandrel: An apparatus put inside of the cross section mounted to the roll former to support the part being roll formed, sweep the part, or to lock seam the part.

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. Metal thinning generally occurs at the bend & is also known as necking.

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.

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: Another term for cross bow and shows up in flat areas between bends.

Outboard: Term used to describe the operator side of the roll space. A.K.A. Front side

Outboard mill: A roll forming machine with housings that support both ends of the roll tooling shafts.

Outboard Spacers: The spacers that go in between the roll tooling and the outboard stand.

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.

Outside radius: The formed outside radius of a bend.

Over Bend Pass: This is the pass or passes that are designed into the set of roll tooling that takes the product and forms the material past the product design intent, so that springback and some material variations can be controlled.

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.

Pass: This refers to the group of roll tooling that goes onto one station.

Pass Line Height: This refers to the distance between the floor and the bottom of the part. Plastic deformation: The permanent deformation that occurs in the forming of metal after the elastic limits have been exceeded.

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.

Pitch Diameter: Points in each pass where the top roll diameter and the bottom roll diameter are equal.

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.

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 or when post cutting is limited due to the profile geometry.

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 or guide used to support material exiting a punch press before it enters the roll forming machine.

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.

Rafted Roll Former: This refers to a type of machine that is specifically designed to leave the roll tooling on the spindles during changeover, which is considered to be a quick change feature, as it removes the whole top of the machine.

Reducing Radius: This method of radius design is also referred to as a diminishing radius. It relies on the material usage in the radius to remain a constant. To do this, the radius starts large, as the bend angle is small. As the angle of the bend increases in later passes, the radius reduces in size. This method of bending develops a truer radius than other methods. Reducing radius is more complex, but it has become the most common means of bending since CAD and CNC lathes have made it easier.

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 caused by the uncoiler.

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-space: The linear space of the roll shafts (spindles) where the roll tooling and alignment spacers are mounted.

Roll Stamp Ring: A recessed ring cut into the operator side of the flat face of a roll detail where the roll information is stamped or etched. A -- Roll Manufacturer; B -- Design Number; C -- Date of Manufacture; D -- Tool Steel Type (D2, O1, L6); E -- Section Number, or Name; F -- Pass Number (pass number 2); G -- Spindle (B-Bottom / T-Top); H -- Roll Section Number, or Spacer; I -- Rework Date

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.

Roll Stops or Traps: The area of the roll where the steel strip or coil is contained, thereby limiting the amount of stretching or walking from side to side.

Rotary Embossing or Rotary Piercing: This refers to the process where a male and female roll are made with a specific pattern that is then pressed or pierced into the material that is being roll formed.

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

Scoring or Grooving: This term refers to a specific process where the roll tooling is designed with sharp corners that cut or displace the material being roll formed.

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.

Self Threading: This is the term used when the material will go through the complete set of roll tooling without any help from the operator bending or moving the material going from pass to pass.

Shaft / Spindle / Arbor: Refers to the portion of the machine that the roll tooling mounts onto.

Shear Form: This term refers to the shearing and moving of the material to make tabs or depressions into the material during the roll forming process

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.

Shoulder: A step in the roll shaft that protrudes from the gearbox or inboard towers (stands) and acts as the tooling seat where all stations are aligned to a common point.

Side Roll Stand: Stands located between two stations with vertical spindles (generally non-driven). Side rolls mounted to these stands are vital in both the formation of the profile as well as guiding the material into the next station. A.K.A. Idler roll stand

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.

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.

Split rolls: Where two or more roll segments make up an assembled pass of rolls. Rolls are split into segments for various reasons such as: ease of machining, ability to place shims or spacers between segments for gauge or width changes, weight considerations, less expensive replacement parts and easier installation of top and bottom rolls

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

Stacking the Rolls and Wiring: This is a process during the manufacture of the roll tooling and also during troubleshooting, when the rolls of an individual pass are stacked on a surface plate and the top rolls are mated to the bottom rolls. A predetermined plug gage is passed through the area where the material is being formed to make sure the pass is made properly.

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: This is referred to as the individual portion of the machine that holds one complete top and bottom roll set.

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.

Step Off Roll Alignment: This is the term used when the roll tooling is designed in such a way that spacers of different lengths are used to save on the amount of tool steel used to manufacture the roll tooling.

Step-up: A small increase in roll diameters from pass to pass, resulting in greater surface speeds which creates a desired tension (pulling) of the strip during forming. The use of step-up is primarily done when running light gauges (.01 to .05) and in the early forming stages. Typically the amount of step-up is between .020 and .030 diameter.

Straightness: This is the term used to define how flat the finished shape comes out of the roll form tooling.

Straightening fixture: A stand or fixture mounted after the last forming station and adjusted to eliminate unwanted twist, camber and bow. When running pre-cut-to-length strips, the stand is often mounted between the last two stations so the part can be pulled out of the straightener. There are many variations of straightening devices, but most are either a block or roller style.

Straight Roll Alignment: This is the term used when the roll tooling is designed with the first pass the same width as the last pass and all the inboard spacers the same length.

Strip Width and Strip Width Calculation: This refers to the calculation the roll designer makes to determine what the width should be for the material that will be roll formed.

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 include incorrect horizontal roll alignment, camber in the coil and uneven forming pressure.

Sweep Unit: Much like the straightener stand it holds the sweep blocks or roller unit, which puts in the continuous sweep into the roll formed part.

Tear Drop: This is a term used when the material is roll formed back onto itself and leaves an air gap that resembles a drop of water.

Thickness: The gauge or depth of a material.

Toggle Gear: This term refers to a specific gear arrangement that allows for an adjustable vertical range of about 3.

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, powdered metals or carbides.

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 or when forming an asymmetrical profile. Twist should be less than 5 in 10 feet of length of the roll formed parts.

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.

Vertical Centers: The distance between the centerline of the bottom shaft and the centerline of the top shaft is referred to as the machines vertical centers.

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