.Roll Forming Handbook.MANUFACTURING ENGINEERING AND MATERIALS PROCESSING A Series of Reference pps

double-Although roll forming was already used in the early 1900s, it was only after the Second Word War when it took over a significant percentage of the fabrication of sheet metal produc

Roll Forming Handbook

MANUFACTURING ENGINEERING AND MATERIALS PROCESSING

A Series of Reference Books and Textbooks

SERIES EDITOR

Geoffrey Boothroyd

Boothroyd Dewhurst, Inc.

Wakefield, Rhode Island

and J S Weinstein

2 Cold Rolling of Steel, William L Roberts

Applications, Harry P Kirchner

4 Metal Forming: The Application of Limit Analysis, Betzalel Avitzur

5 Improving Productivity by Classification, Coding, and Data Base Standardization: The Key to Maximizing CAD/CAM and GroupTechnology, William F Hyde

and Laurence E Murch

in Design, David W Richerson

Processes, Ulrich Rembold, Karl Armbruster, and Wolfgang Ülzmann

10 Hot Rolling of Steel, William L Roberts

CAD/CAM Implementation, Joseph Harrington, Jr

13 Industrial Materials Science and Engineering, edited by Lawrence E Murr

14 Lubricants and Lubrication in Metalworking Operations, Elliot S Nachtman and Serope Kalpakjian

15 Manufacturing Engineering: An Introduction to the Basic Functions, John P Tanner

Ulrich Rembold, Christian Blume, and Ruediger Dillman

17 Connections in Electronic Assemblies, Anthony J Bilotta

Edward Walker

19 Nontraditional Manufacturing Processes, Gary F Benedict

Tijunelis and Keith E McKee

23 Factory Information Systems: Design and Implementation for CIM Management and Control, John Gaylord

24 Flat Processing of Steel, William L Roberts

25 Soldering for Electronic Assemblies, Leo P Lambert

26 Flexible Manufacturing Systems in Practice: Applications, Design, and Simulation, Joseph Talavage and Roger G Hannam

27 Flexible Manufacturing Systems: Benefits for the Low InventoryFactory, John E Lenz

Geoffrey Boothroyd and Winston A Knight

Manufacturing, James Nolen

30 Steel-Rolling Technology: Theory and Practice, Vladimir B Ginzburg

Jack Arabian

Alfred F Scheider

36 Manufacturing Engineering: An Introduction to the Basic Functions, Second Edition, Revised and Expanded, John P Tanner

39 High-Quality Steel Rolling: Theory and Practice, Vladimir B Ginzburg

Revised and Expanded, Leo Alting

41 Metalworking Fluids, edited by Jerry P Byers

John A Bosch

44 Facilities Planning and Materials Handling: Methods andRequirements, Vijay S Sheth

Pierre C Guerindon

46 Laser Materials Processing, edited by Leonard Migliore

of Constraints, Robert E Stein

and John S Agapiou

51 Statistical Process Control in Manufacturing Practice, Fred W Kear

James D Meadows

M Ramulu, and Philip Koshy

54 Introduction to Manufacturing Processes and Materials, Robert C Creese

55 Computer-Aided Fixture Design, Yiming (Kevin) Rong and Yaoxiang (Stephens) Zhu

Revised and Expanded, Nello Zuech

57 Flat Rolling Fundamentals, Vladimir B Ginzburg and Robert Ballas

Second Edition, Revised and Expanded, Geoffrey Boothroyd, Peter Dewhurst, and Winston A Knight

Suresh G Advani and E Murat Sozer

Dimensioning and Tolerancing, Robert Campbell

61 Handbook of Induction Heating, edited by Valery I Rudnev, Don Loveless, Raymond Cook and Micah Black

of Constraints, Second Edition, Robert Stein

63 Manufacturing: Design, Production, Automation, and Integration,Beno Benhabib

65 Metallurgical Design of Flat Rolled Steels, Vladimir B Ginzburg

Geoffrey Boothroyd

68 Metal Cutting Theory and Practice, Second Edition, David A Stephenson and John S Agapiou

Geoffrey Boothroyd and Winston A Knight

A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc.

Boca Raton London New York

Published in 2006 by

CRC Press

Taylor & Francis Group

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Boca Raton, FL 33487-2742

© 2006 by Taylor & Francis Group, LLC

CRC Press is an imprint of Taylor & Francis Group

No claim to original U.S Government works

Printed in the United States of America on acid-free paper

10 9 8 7 6 5 4 3 2 1

International Standard Book Number-10: 0-8247-9563-6 (Hardcover)

International Standard Book Number-13: 978-0-8247-9563-4 (Hardcover)

Library of Congress Card Number 2005048630

This book contains information obtained from authentic and highly regarded sources Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials

or for the consequences of their use.

No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers

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Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe.

Library of Congress Cataloging-in-Publication Data

Roll forming handbook / edited by George T Halmos.

p cm (Manufacturing engineering and materials processing ; 67) Includes bibliographical references and index.

ISBN 0-8247-9563-6 (alk paper)

1 Roll forming (Metalwork) Handbooks, manuals, etc I Halmos, George T II Series.

TS340.R5857 2005

Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com

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is the Academic Division of Informa plc.

DK1201_Discl.fm Page 1 Tuesday, October 4, 2005 10:42 AM

During the 100-year history of roll forming, thousands of knowledgeable tool, equipment, andproduct designers and users have worked and are still working in this industry Unfortunately, most ofthe experience gained by those roll former operators, setup personnel, and designers has never beendocumented in any meaningful way, and it remains the secret of the individuals Of all the publishedpapers and research reports, only a limited number can be readily interpreted and applied in rollforming plants.

The aim of this handbook is to fill this gap in knowledge and to provide comprehensive informationabout roll forming equipment to operators, supervisors, engineers, and tool and equipment designers, aswell as to students interested in this trade The text is based on the authors’ own experience, enrichedwith the experience of other individuals willing to share their knowledge with them

Roll forming is a complex subject It is possible that readers will search for and cannot find certainmissing details As editor and author, I chose to include those subjects that I thought would be mostrelevant to both novices and experienced practitioners Nobody knows everything about roll forming;readers’ experiences may differ from those described in this book because of the multitude of factorsinfluencing the quality and quantity of roll formed products Therefore, readers are encouraged to sendtheir comments, observations, and data to the editor and authors of this book Certainly, their criticismand the new information will enrich subsequent editions of this handbook

I was introduced to roll forming by my former boss in the late 1950s On my first day on the job, hepointed to an uncoiler and explained, “There’s where the material comes from, it’s formed in the nextequipment, which is the mill and then it is cut to length The rest of it you will learn.” And I learned thehard way, by trying to understand the process, reading the few papers on the subject that were available

at that time, and taking courses provided by FMA, SME, and a few other organizations Admittedly, mymost valuable experience stems from setting up mills with rolls I designed and operating the roll formingline I never forgot the mistakes I made However, a lifetime would not be enough to gain all of the

iii

experience that I learned from mill operators, setup personnel, suppliers, colleagues, and friends whowere willing to share their “hard learned” knowledge with me.

Special acknowledgment to Andy Baird, Tony Srnec, and to a long list of co-speakers at roll formingconferences: Tim Gutowski, Don Hill, Joe Ivaska, Barlow Brooks, Leo Gale, and many others I alsolearned a lot from the comments and questions of the audience at my presentations

Thanks to those experts who took the time to read and correct parts of my original manuscript:Roll Design — Tony Rhodes, Fred Gradous; Materials — Shrikant Bhat, Jim Cran, Steve Forrest,Gil Kaufman, Alan Pearson, Paul Schurter, and others

The writing of this book was also made possible by the understanding and support of my family,including the correction of my English grammar by my children, typing of the text by my efficientsecretary Fanny Tam, the preparation of drawings by George A Dobrev and several other engineers, andthe kind cooperation of about 30 companies

George T Halmos

Prefaceiv

George T Halmos, consulting engineer, has been the president of Delta Engineering Inc in Toronto,Canada since 1979 He graduated as a mechanical engineer from the Technical University of Budapest in

1950 He worked for 4 years as a research engineer and was head of the largest material testing laboratory

in middle Europe He was also a lecturer at the Technical University of Budapest from 1950 to 1956 In

1957, he joined a subsidiary of Alcan in Toronto as a design engineer For the next 17 years, he workedfor the largest sheet metal manufacturing company in Canada (Westeel-Rosco Ltd.) in the positions

of project engineer, then works manager and chief engineer In 1976, he joined B&K MachineryInternational Ltd as general manager of the Roll Forming Division He has participated in theengineering committees of the Canadian Steel Sheet Building Institute, the Canadian Steel Pipe Institute,and the Canadian Standards Association Metric Committee He is a member of several professionalassociations and is a registered consulting engineer He authored approximately 50 technical papers andhas made over 100 presentations on various subjects on roll forming

Currently, he provides consulting and troubleshooting services, conducts management and operatortraining courses, and carries out research and development in all aspects of sheet metal manufacturingtechnologies, with special emphasis on roll forming; customers range from the smallest shops to theword’s largest manufacturing companies

v

Ashok Shah

The Lockformer Company Gerard International Corporation Naperville, IL

3 Presses and Die Accelerators George T Halmos 3-13.1 General 3-13.2 Mechanical Presses 3-63.3 Pneumatic Presses 3-103.4 Hydraulic Presses 3-123.5 Information and Dimensions for Press/Die Purchasing and Installation 3-153.6 Rotary and Other Cutting, Punching Equipment 3-153.7 Flying Die Accelerators 3-20

4 Secondary Operations in the Roll Forming Line George T Halmos 4-14.1 Secondary Operations 4-24.2 Straightening 4-34.3 Tight or Loose Line: Cutting Before, In-Between, or After Roll Forming 4-94.4 Location of the Secondary Operations 4-144.5 Stationary and Flying Dies 4-144.6 Punching, Perforating, Notching, and Mitering 4-164.7 Piercing and Partial Punching 4-194.8 Flanging, Louvering, and Lancing 4-204.9 Embossing and Drawing 4-204.10 Bending 4-224.11 Curving (Sweeping) 4-244.12 Marking 4-464.13 Swedging (Off Setting) 4-464.14 Rotary Dies 4-46

ix

4.15 Mechanical Joining of Different Strips or Parts 4-564.16 Adhesive Bonding 4-604.17 Soldering and Brazing 4-604.18 Resistance Welding 4-604.19 Painting 4-624.20 Foaming 4-624.21 Packaging 4-62References 4-62

5 Roll Design George T Halmos 5-15.1 Roll Design Process 5-25.2 Cross-Section 5-45.3 Product Orientation and Other Operations in the Line 5-135.4 Materials 5-195.5 Roll Forming Mill 5-285.6 Other Tool Design Considerations 5-405.7 Spacers and Shims 5-485.8 Calculating Strip Width 5-525.9 Bend Lines 5-555.10 Number of Passes 5-645.11 Flower Diagram 5-735.12 Roll Design 5-785.13 Calculating Roll Dimensions Manually 5-945.14 Computer-Aided Roll Design 5-955.15 Examples 5-1005.16 Roll Marking System 5-1035.17 Roll Orientation 5-1075.18 Setup Charts 5-107References 5-111

6 Materials George T Halmos 6-16.1 Design Considerations 6-16.2 Mechanical Properties 6-26.3 Crystalline Structure of Metals 6-76.4 Forming Metals 6-76.5 Increasing the Strength of Metals by Cold Working 6-106.6 Hot Rolling 6-106.7 H.R and H.R.P.O Steels 6-126.8 Cold Rolled Steel 6-126.9 Carbon Steel 6-126.10 Alloyed Steel 6-136.11 Stainless Steel 6-156.12 Metallic Coatings 6-166.13 Nonmetallic Coating and Laminating 6-176.14 Joining Different Materials in the Roll Forming Process 6-186.15 Aluminum 6-186.16 Other Metals and Materials 6-20

Contentsx

6.17 Influence of Primary Metal Processes on Roll Forming 6-206.18 Guideline to Steel Prices 6-24References 6-24

7 Lubrication Joseph Ivaska 7-17.1 Tribology of Lubrication 7-17.2 Selection of Lubricants 7-57.3 Surface Properties of Formed Material 7-87.4 Lubricants for the Secondary Operations 7-107.5 Application Techniques 7-117.6 Preparation and Maintenance of Lubricants 7-127.7 Operating Problems during Production 7-18

8 Coil Processing, Material Handling, and Plant Layout

George T Halmos and Joseph Horvath 8-18.1 Flow of Material 8-28.2 Coil Handling and Storage 8-38.3 Sheet Handling and Storage 8-68.4 In-Line Coil Handling 8-98.5 Coil End Welding 8-148.6 Strip (Coil) Accumulators 8-168.7 Flattening and Leveling 8-198.8 In-Line Sheet Handling 8-228.9 Finished Product Handling 8-238.10 Finished Product Storage 8-318.11 Material Handling Equipment 8-348.12 Material Handling Accessories 8-388.13 Crane Controls 8-408.14 Plant Layout 8-41References 8-43

9 Designing Products for Roll Forming George T Halmos 9-19.1 Developing Light Gage Products 9-19.2 Design Considerations 9-29.3 Secondary Operations 9-109.4 Profiles Manufactured in Different Sizes 9-209.5 Design of Specific Products 9-229.6 Dimensioning and Tolerancing 9-22References 9-29

10 Equipment Installation, Roll Setup, Maintenance, and Troubleshooting

George T Halmos 10-110.1 Installation of Roll Forming Lines 10-110.2 Roll Installation and Setup 10-810.3 Maintenance and Spare Parts 10-1410.4 Troubleshooting and Trouble Prevention 10-32

11 Behavior of Metal Strip during Roll Forming Manabu Kiuchi 11-111.1 Various Types of Deformations 11-111.2 Causes of Redundant Deformations 11-311.3 Effects of Redundant Deformations on Product Defects 11-611.4 Mathematical Simulation of the Deformation of a Metal Strip 11-1911.5 Computerized Design System for Roll Profiles 11-2911.6 CAE for Roll Forming 11-34

12 Acquiring Roll Forming Lines, Education, and Training George T Halmos 12-112.1 Why Roll Form Products? 12-112.2 Different Paths to Start Roll Forming 12-212.3 Evaluating the Product 12-312.4 Selecting Line Components 12-412.5 Procuring Roll Forming Tooling 12-712.6 Equipment and Tool Specifications 12-712.7 Acceptance Test 12-712.8 Education and Training 12-712.9 Motivation 12-11References 12-11

13 Safety Ashok Shah 13-113.1 Safety 13-113.2 Common Safety-Related Definitions 13-213.3 Safety Design Procedure 13-213.4 Determining Limits of the Machinery or System 13-313.5 Determining Hazards/Risk Estimation 13-313.6 Risk Reduction by Design 13-813.7 Safeguarding 13-913.8 Selection of Guards and Protective Devices 13-1313.9 Required Characteristics of Guards and Protection Devices 13-1313.10 Signals and Warning Devices 13-1413.11 Personal Protective Equipment 13-1413.12 Training 13-1413.13 Summary 13-15References 13-16

14 Increasing Efficiency of Roll Forming Lines and Case Studies George T Halmos 14-114.1 Output, Productivity, and Efficiency 14-114.2 Line Utilization 14-214.3 Improving Productivity 14-314.4 Case Studies 14-414.5 Preliminary Tool and Equipment Cost Analysis 14-1014.6 Preliminary Cost Analysis 14-10

15 Unusual, New, and Future Roll Forming Technologies George T Halmos 15-115.1 The Last 100 Years 15-215.2 The Future of Roll Forming 15-2

Contentsxii

15.3 Pull-Through Mills: Nondriven Rolls 15-515.4 Tension Roll Forming 15-615.5 Combining Roll Forming and Cold Drawing 15-715.6 Developing New Roll Forming Methods 15-715.7 Roll Forming Tools 15-915.8 Reducing the Thickness of the Starting Material 15-1015.9 Forming at Elevated Temperature 15-1115.10 Hot Roll Forming Variable Cross-Sections 15-1115.11 Hot Thickness Reduction along the Length of the Strip 15-1215.12 Welding Hot Roll Formed Sections 15-1215.13 Other “Hot” Processes 15-1315.14 In-Line Soldering, Brazing, and Heat Treating 15-1315.15 Equipment and Tooling Requirements for Hot Roll Forming 15-1415.16 Press Tooling for Conventional Roll Forming Lines 15-1615.17 Computer-Controlled Roll Forming Lines 15-16References 15-17

Appendices A-1

References R-1

Index I-1

Introduction to Roll

Forming

George T Halmos

Delta Engineering Inc.

1.1 Introduction to Roll Forming 1-1

A Short History of Using Metals † Forming of Sheet Metals † What is Roll Forming? † Basic Requirements

1.1 Introduction to Roll Forming

1.1.1 A Short History of Using Metals

Our ancestors used wood and stone tools for over 1.7 million years, give or take a few hundred thousandyears, before making use of metals It was only around 6000 B.C when naturally available gold (and latercopper), meteorite iron, and a few other metals were shaped by hammering to make ornaments, tools,and weapons Afterwards, our forefathers discovered how to reduce ores, melt and alloy metals, andutilize them for more elaborate products

Gold was mainly used for jewelry because it is too soft for implements Copper was only slightlyharder, but by adding arsenic and tin to copper, the early Bronze Age smiths could produce good-qualityaxes and other articles Gradually, more and more bronze articles were used and the Bronze Agesuperseded the Stone Age

Gold, copper, tin, lead, silver, iron, and mercury were the only seven known and used metals until thethirteenth century and only five more metals were discovered up until the seventeenth century Today, weknow that about two thirds of all known elements are metals

The first iron products dated back to 3000 to 4000 B.C., but they were scarce and expensive The edges

of iron implements were too soft; therefore, iron articles were suitable for ornaments but not for tool andweapons The discovery of carbonizing around 1200 to 1300 B.C brought major change and heralded thebeginning of the Iron Age Steel products became better for tools and weapons Transition was slow, buteventually cast and forged iron products replaced bronze in most areas Furnaces became larger and steelbecame better The early smiths produced excellent quality axes, chisels, hoes, swords, and otherimplements In 1350, the ironmakers of central Europe succeeded in melting and casting iron trough theuse of primitive blast furnaces [438]

Making complex items, such as body armor assembled from hundreds of matching pieces ofhammered plates and wires, required considerable skill and experience The process was extremelylabor-intensive because of the long hours of hammering required Actually, up to the seventeenthcentury, to the dawn of the Industrial Revolution, every noncast item, from ornamental to utility wasmade by hand, through labor-intensive forging Not many people could afford to own metal products

1-1

During the Industrial Revolution of the eighteenth and nineteenth centuries, many of the handtoolsused in metal manufacturing were gradually replaced by power-driven machinery Water wheels, steamengines, and, later on, electrical motors provided an abundant quantity of power In 1855, Bessemerpatented the first modern steel-making method in England, a process that provided large quantities ofbetter quality steel Originally, steel was intended for castings (canons), but eventually most of it wasprocessed by forging, using big, powered presses.

One of the most significant and least-heralded achievements of the Industrial Revolution wasthe replacement of the ancient art of hammering (forging) with pairs of rotating rolls to change the shape

or the thickness of the metals Based on the forging experience, and knowing that steel is morepliable when it is hot, the rolling process was completed at high temperatures Rolling reducedthe thickness and increased the surface area in contact with air The rapid cooling of the largesurfaces limits the minimum thickness achievable by hot rolling The introduction of flywheels, clutches,reversible steam engines, and electrical motors contributed to faster steel forming processes, permittingfurther reduction of the minimum thickness of the rolled products However, the thinner the metal gets,the larger its surface and the faster the rate of cooling Therefore, even with the most modern equipment,the minimum thickness of commercially available hot rolled steel is still about 0.060 to 0.070 in.(1.5 to 1.8 mm)

Rolling at room temperature is not a new technology Primitive cold rolling was used in thefourteenth century for gold and silver The first true rolling mills of which any record exists weredesigned by Leonardo da Vinci in 1480 [437] In the late sixteenth and early seventeenth centuries,pairs of rolls were used to roll flats from soft materials such as gold, lead, and tin, probably at roomtemperature Cold rolling was also used to planish tin plates Room temperature (cold) rolling of steelcommenced in the late eighteenth century and became more widely used in the nineteenth century Bythe late nineteenth and in the twentieth centuries, an immense variety of hot and cold rolledaluminum, copper, brass, lead, tin, titanium, zirconium, and specialty alloys sheet becamecommercially available Without these rolled flat products, our current life and our living standardwould be unimaginable

1.1.2 Forming of Sheet Metals

The name “manufacturing” originates from the Latin manu (hand) and factura (making) When rolled sheets became commercially available, for a long time, the final products were manufactured,formed, and shaped by hand Gradually, machines, particularly presses, substituted for most of the handforming

flat-A variety of mechanical presses (single-action screw, friction, link-and-crank, and different action draw presses) and hydraulic presses were used almost exclusively to blank, form, or draw all sheetmetal products until the early twentieth century Other processes, such as curving, profile drawing,stretch bending, spinning, winding, beading, explosive forming, electromagnetic forming, and hydroforming are also used for forming sheets and plates However, the combined output of these processes isconsiderably less than that produced by the presses and later on by roll formers

double-Although roll forming was already used in the early 1900s, it was only after the Second Word War when

it took over a significant percentage of the fabrication of sheet metal products from press brakes andother types of forming Owing to the high efficiency of roll forming, the labor content of many productswas drastically reduced

Roofing, siding, farm buildings, grain storage bins (silos), shelving, storage racks, fluorescent lightfixtures, electrical products, refrigeration, heating, ventilation, railway cars, power plants, doors,windows, toilet partitions, bicycle wheels, fire places, furniture, appliances, airplanes, spacecraft,swimming pools, and countless other products have all been efficiently roll formed

In the 1950s and 1960s, rotary encoders were introduced and the applications of pneumatic presses,in-line welding, prepunching, and roll forming prepainted metals spread widely Eventually, more andmore other operations were incorporated into the roll forming lines

Roll Forming Handbook1-2

In the 1970s and 1980s, prepunching became more sophisticated through the use of different controlsand gagged punches Innovations were introduced to reduce tool changeover time using raftedconstruction,1side-by-side rolls and other devices Die accelerating systems became more sophisticatedand lengths more accurate Steels with up to 200,000 psi (1960 MPa) yield strength and many exoticmetals were successfully roll formed In the late 1970s and early 1980s, computer-aided roll designsystems were introduced.

In the 1990s, an increased number of programmable controllers and computers have been added tocontrol the lines The product, as well as the material tolerances, has become tighter and the demand formanufacturing flexibility has increased Customers pressed equipment suppliers for better quality andmore efficient lines, including automated finished-product handling Competitiveness has necessitatedthe reduction of the number of operators and in some cases one operator to run two or more lines, at anincreased speed, and at a higher utilization rate

By the 1970s, about 35 to 40% of all sheet products produced by the North American steel mills wereprocessed through roll formers In the last decades of the twentieth century, roll forming of automotiveproducts became the fastest growing segment of the industry

The roll forming industry is still growing strongly in the twenty-first century

1.1.3 What is Roll Forming?

It is not a simple task to describe or explain the concept of roll forming A frequently used definitiondemonstrates the complexity:

To form sheet metal strip along straight, longitudinal, parallel bend lines with multiple pairs ofcontoured rolls without changing the thickness of the material at room temperature

Similar to many other definitions, the above one also has exceptions

To form sheet metal strip along straight, longitudinal, parallel bend lines, but

* The products often exit the roll former curved or in a spiral form

* The products can have bend lines 908 to the longitudinal bend line

* The bend lines are not always parallel (intentionally)

* The bend lines are not always straight (occasionally unintentionally)

with multiple pairs of contoured rolls, but

* To achieve the desired shape, the roll formers may apply bronze shoes, plastic guides and,especially during setup, 2 £ 4s If the wood pieces are effective during the setup, then they areclamped to the machine Once the clamps are taken away, the 2 £ 4s are strapped to theequipment If they are still functioning well after a month or so, then they are painted in green andbecame part of the line [431]

without changing the thickness of the material, but

* The thickness is almost always reduced at the bend lines

* In thin curved products, the outside fibers are thinner than the inside ones

* Mills are built with special passes to reduce the strip thickness at specified locations

* Contrary to good practice, the thickness of the material is occasionally

reduced by bent shafts, and far too frequently by the operators

1 Raftedw Rollformer is a registered trade name of The Bradbury Group.

at room temperature, but

* To eliminate the cracking of paint at the bend lines, the material can be preheated just beforeforming

* Plastic can be roll formed at elevated temperature

* In-line soldering, brazing, or annealing requires elevating the temperature of metal whileprocessing through the equipment

* Titanium was hot roll formed in the late 1960s

* Hot roll forming is a potential new technology

Roll forming is a flexible process, where both the fundamental rules and the exceptions can be utilized Ithas been proven several times that even seemingly impossible roll forming tasks can be accomplished,although it may take a longer time and much more money On the other hand, it has also been shownthat plans to roll form simple shapes can create disastrous results if the basic rules of roll forming are notfollowed

1.1.4 Basic Requirements

1.1.4.1 Satisfying Customers

Roll formed products are sold to customers in an extremely competitive market Customers are alwayslooking for manufacturers who can repeatedly meet with their basic requirements They are expecting toreceive:

* The right quality

* The right quantity of products

* At the right time

* For the right price

Companies not able to supply the right quality or the right quantity, at the right time for the right pricewill lose their customers However, not consistently meeting customers’ expectations or havingmanufacturing problems is not always the plant’s fault The plant cannot manufacture good-qualityproducts at the right time for the right price if they are not provided with the basic mechanisms to fulfilltheir obligations

1.1.4.2 Basic Requirements of the Manufacturing Plant

To successfully meet the demands and outperform the competitors, manufacturing plants must have:

* Sufficient run quantities

* The right material to be formed

* Knowledgeable, motivated workforce

Good design (products that can be manufactured without extreme hardship) Most plants have experiencewith products that cannot be efficiently roll formed, or sometimes not roll formed at all The product can

be too complicated for the available equipment, or the dimensions or tolerances are beyond thecapabilities of the equipment or tooling

Sufficient run quantities If the run quantities are below an economical minimum level, then high setupcost can reduce efficiency unless the plant has a special-purpose line set up for that specific product Veryhigh run quantities may reduce product costs but can increase inventory, product-handling cost, andstorage space requirement

Acceptable quality material Running across “bad material” is not a rare occurrence Perhaps thesupplied material was either unsuitable for the product, or it could have been incorrectly specified

Roll Forming Handbook1-4

However, when troubleshooting of the equipment and tooling does not yield quick results, the material isfar too frequently, and often incorrectly, blamed for the bad products.

Proper equipment suitable for forming the product There is no plant without complaints about the rollforming lines Frequently, the complaints are justified; sometimes, it is the results of procuring a line ofinsufficient capacity or bad quality, or of neglected maintenance or abusive usage by the operator The life

of a good-quality, reasonably well-maintained roll former can be over 50 years Most malfunctioningequipment problems are corrected in the first year, and the mill will operate with reasonable reliability.However, incorrectly specified, slow, weak, or low-quality lines cannot be made competitive against fasterand better lines

Good tooling Roll forming lines are equipped with several sets of tooling during their lifetime quality, operator-friendly, properly set up tooling is essential to produce good-quality products atreasonable price

Good-Knowledgeable, motivated work force It has been stated repeatedly that the greatest asset of a company

is its people A company can have an excellent product, good material, the best equipment and tooling,but is still unable to produce competitively without knowledgeable people Continuous education of theoperators and other employees, combined with motivation, is crucial to good productivity and profit

Cantilevered Mills † Duplex Mills † Through-Shaft Duplex Mills † Standard (Conventional) Mills † Double-High Mills † Rafted (Plated, Cassetted) Mills † Side-by-Side Mills † Pull-Through Mills † Spiral-Tube Mills †

Truck-Mounted Mills † Special Mills

The heart of the roll forming line is the mill The mill provides the power and support to the toolingthat forms the metal The complete roll forming line is aligned with the shaft shoulders of the rollforming mill

The variations in mill design are unlimited, but mills can be classified as cantilevered, duplex, shaft duplex, standard (conventional), or rafted (plated) Those not fitting into any of these categoriesmay be considered as “special mills.”

through-2.2 Mill Types

2.2.1 Cantilevered Mills

The shafts of the cantilevered mills are supported at one end only; hence, they are sometimes called

“overhanging” or stub-type mills (Figure 2.1)

Cantilevered mills, producing lock-forms at the edge of sheets, have been popular with sheet metalworkers for a long time They are low-cost, nonsophisticated machines, and require little adjustment Thecantilevered mills become more popular and have been used to form many simple, narrow sections(Figure 2.2)

To utilize the mill for two sections, the opposite side of the “cantilevered” shaft ends can be tooled toform another section (Figure 2.3)

The advantages of the cantilevered mills are:

* Relatively low cost

* Capability to form the edge of sheets of any width

2-1

FIGURE 2.1 Cross-section of cantilever mill.

TABLE 2.1 Shaft Diameter Selection Examples

6

r

FIGURE 2.2 Cantilever mill (Courtesy of Metform International Ltd.)

Roll Forming Handbook2-2

The disadvantages of the cantilevered mills are:

* Singular adjusting screw makes it difficult

to set the required roll gap

difficult to adjust the shafts up or down,

while keeping the top shaft parallel to the

bottom shaft

under the same load is approximately four

times the deflection of the same shaft

supported at both ends (Figure 2.4)

Owing to the larger deflection of the

cantilevered shaft, the shaft length (and

the maximum formed width) is limited

The first two shortcomings can be eliminated by

using double-adjusting screws connected with

gears (one shaft-height adjusting screw rotates

the other one) The deflection can be reduced by

FIGURE 2.3 Cantilever mill with rolls at both ends of the shafts.

(a) supported at one ends

(b) supported at both ends defla= 4 deflb

FIGURE 2.5 Connecting the operator side of the cantilevered shafts reduces deflection.

FIGURE 2.6 Rafted cantilever mill stand (Courtesy of CompuRoll Inc.)

Roll Forming Handbook2-4

using larger shaft diameter shafts or by applying a connector (yoke) between the top and bottom shafts

at the operator side (Figure 2.5) This connecting unit can be applied to form narrow sections only.Using cantilevered mills, the maximum width of the formed part of the product seldom exceeds 4 in.(100 mm)

To facilitate fast profile changes, rafted (plated) cantilevered mills have been developed (Figure 2.6).The plate, supporting the stands, shafts, and tools, can be lifted off and exchanged with another onewithin a few minutes

2.2.2 Duplex Mills

Two cantilevered mills facing each other are called

a duplex mill Duplex mills have one common

base and drive (Figure 5.47) They can form both

edges of narrow or wide products leaving the

center flat The minimum strip widths depend on

how close the opposing rolls can be pushed

together, and the maximum widths usually

depend on how far the two mills can be moved

from each other The width of the formed

products can be changed quickly by adjusting

one or both sides of the duplex mill in or out

(Figure 2.7)

Duplex mills have the same advantages and disadvantages as the cantilevered mills, except that theshaft end connecting pieces cannot be used Some duplex mills have shafts extended at the other side ofthe mill, which can be used to form narrow sections

Duplex mills either have one side fixed and the other one adjustable, or both sides adjustable.Adjustment of a side is usually accomplished by placing all stands on one plate, which, with properguides, can be moved in and out, thus changing the gap between the two cantilevered mills

For duplex mills with one adjustable row of stands, the centerline of the product changes with widthchange

In the case of duplex mills with two adjustable rows of stands, the centerline of the products remains inthe same position This arrangement is used when holes are prepunched at or around the centerline,either when the cutoff die has to be kept symmetrical or for other reasons when it is advantageous to keepthe centerline in the same position (Figure 2.8)

The width adjustment can be manual or motorized The most sophisticated lines have programmablecontroller or computer-controlled width adjustment Forming rolls installed in a cantilevered or duplexmill are seldom exchanged to produce different profiles

It is highly recommended that rolls are installed with the same length through the mill This makes itvery easy to check shoulder alignment (by placing a “straight edge” to the end of the rolls) and to checkwhether the two rows of stands are parallel

(by checking the gap between the tooling)

Both the single cantilevered and duplex mills

must have long entry and reasonably long exit

guides (Figure 2.9) The uneven roll pressure,

uneven or asymmetric forming, and bent shafts

can generate uneven driving forces, resulting in a

skewed entry or exit of the product (Figure 2.10)

Firmly attaching the entry and exit guides to

the entry and exit stands eliminate the individual

adjustment of the guides when the width is

changed Both the entry and exit guides should

FIGURE 2.7 Duplex mill with one or two adjustable row

of stands.

2 1,2,3 1 2 3 4 4 3 1 1 3 4 2

(a)one side adjusted (b)both sides adjusted

L C L

have curved (“fish-mouth”) entry sides For manual loading from the side, it is recommended that theentry guide opposite to the loading side is longer than that at the loading side The operator can load andpush the precut blank against the longer side and then push it into the mill The length of the guides is not

as critical if the mills are fed with coils and the parts are postcut

Bending short legs at the edges can create other problems The horizontal vector of the bendingforces pushes the strip inward towards the center The shorter the bent leg, and the larger the widthand thickness ratio of the flat, unsupported center part, the greater the buckling tendency will be(Figure 2.11)

Center support is used to avoid buckling of the wide flat center part Because of the self-weight of thematerial, the support is usually placed underneath the center part However, if the horizontal vector ofthe forces is large and the support prevents the sheet to buckle downwards, then it can buckle upwards

To avoid upward buckling, additional support is placed on the top of the center part When the width

is changed, the location (and possibly the number of the center supports) has to be changed too Theseadjustments have to be taken into consideration at the design stage It is also important that the supportshould not scratch or mark the product Embossing, lancing, louvering, or other similar operations

(b)loaded from the side

(a)longitudinally loaded

FIGURE 2.9 Precut sheets fed into roll forming mill requires long entry and exit guides.

too short entry guides

bend lines

bend lines small force

big force

no exit guides front end

FIGURE 2.11 The horizontal vector of the bending forces can buckle the center of unsupported products.

Roll Forming Handbook2-6

ahead of the mill can make proper support

against buckling more complicated

In spite of these drawbacks, the duplex mills

are frequently used to form shelving, doors,

edge-formed sidings, and many other products

where unlimited adjustability between the

mini-mum and maximini-mum widths is required

In some cases where forming of the wide, flat

center section is required (such as mobile home

sidings), one (or more) pairs of grooving rolls are

placed ahead of the first pass The shallow flutes

are stretched in the material before the edges are

formed in the mill (Figure 2.12)

Because roll change is relatively complicated, it is seldom made in the cantilevered and duplex mills Toprovide more versatility, special duplex mills have been developed with quick exchange of the inside andoutside rolls (Figure 2.13)

With duplex roll forming mills, it is very easy to change one dimension of a product; for example, theweb height (“h”) or the leg length (“l”) of “C” channels If both dimensions have to be changed (webheight and leg length, marked h and l, respectively (Figure 2.14), then two independently adjustableduplex mills can be combined, using a common drive Changing the width in the first mill will changethe leg length (l), and changing the second mill will change the web height (h) The two mills have onecommon centerline This method is used to form drawers for metal filing cabinets, “C” sections, andother products A third dimension, the lip width (marked “c” in Figure 2.14), can also be changed byadjusting the strip width that enters into the first mill, or by having a third duplex mill incorporated intothe unit (Figure 2.15) A mill tooled for “C” channels can also produce “U” channels without tool change.Because the entry guides and the straighteners are attached to the mill stands, changing the productdimensions is very simple and quick Some of these mills are equipped with servo motors andprogrammable controllers or computers A line containing prepunching and cutting presses can produce

FIGURE 2.12 Forming the center of a panel with

“grooving rolls” in a duplex mill.

FIGURE 2.13 Quick exchange of roll sets in a duplex mill (Courtesy of The Lockformer Co.)

infinite varieties of “C” channels (studs) and “U” channels (tracks) within the parameter of the machine,without tool change Frequently, the only requirement is to enter the part number (or dimensions)and the required quantities into the control unit The product dimension changeover time can be as low

2.2.3 Through-Shaft Duplex Mills

The through-shaft duplex mill (Figure 5.51) is a combination of the duplex and conventional (standard)mills The main characteristics of the through-shaft duplex mills are:

* The through-shafts deflect less than the cantilevered shafts

* Rolls are mounted on sleeves

* Sleeves are attached to the stand at each side

* All the operator-side stands are mounted on a common plate, which can slide in or out, thuschanging the distance (roll lengths) between stands Other types of mills allow both sides to movemore in and out

* Sleeves with the mounted rolls are keyed to and sliding in and out on the shafts

l

h

c

(b)first duplex mill

FIGURE 2.14 Adjusting web width and leg length by using a “double” duplex mill.

FIGURE 2.15 Triple duplex mill for U and C channels or other product (Courtesy of CompuRoll Inc.)

Roll Forming Handbook2-8

* Through-shaft can carry center rolls between the two edge-forming rolls These center rolls cansupport or form beads into the products.

The advantages of the through-shaft duplex mill are:

* The reduced shaft deflection permits the forming of thicker/higher strength material than that ofthe duplex mills with the same shaft diameters

* The carrying rolls can support both the top and bottom of the center part of the product

* It is relatively simple to incorporate forming at the center part of the product

* Through-shaft duplex mills do not have restriction on the formed width at the strip edges whileduplex mills are restricted to form the relatively narrow edges (4 in or 100 mm) of the strip.The disadvantages of the through-shaft duplex mill are:

* More expensive than the duplex mill

* Slightly larger diameter rolls are required because they are mounted on sleeves

* Relocating the center rolls can be cumbersome

Many of the variations described in the duplex mills, such as installing two mills in one line, can also beapplied to through-shaft duplex mill

2.2.4 Standard (Conventional) Mills

The shafts of the standard (conventional) mills are supported at both ends (Figure 2.17, Figure 5.54, andFigure 5.77) This design enables building and use of the mills for materials with any width and thickness.Therefore, standard mills are the most popular machines used to roll form metals

In most cases, the drive-side (inboard) stand holds the shafts in position and accommodates the drive.The operator-side (outboard) stand supports the other end of the shafts This stand is removable tofacilitate roll changes Both the operator- and drive-side stands are fastened to a common base

FIGURE 2.16 Producing “C” and “Z” sections in a quick-changeover special duplex mill (Courtesy of The Bradbury Company, Inc.)

The drive-side stands are fixed at one location The operator-side stands are in most mills also fixed atone position (Figure 2.17) In other types of mills, the operator-side stands can be placed into differentlocations along the shafts to accommodate wider and thinner material, or narrower but thicker material(Figure 2.18a,b).

The construction of the mill stands and other components is described in more detail in Section 2.3

2.2.5 Double-High Mills

To satisfy the demand for roll forming two profiles in a limited plant area with quick profile changeover,the “double-high” mills have been developed (Figure 2.19) The double-high mills have alternating shortand tall stands Rolls for one profile are installed in the short stands, and rolls for another profile aremounted on the tall stands The lines have one uncoiler and one cutoff press If the material is fed into the

FIGURE 2.17 In the conventional (standard) mill, both ends of the shafts are supported.

FIGURE 2.18 Conventional mill with adjustable roll space.

(a)

Roll Forming Handbook2-10

lower-level rolls, then one profile (e.g., farm sidings) is formed If the coil is fed into the upper level rolls,then another profile (e.g., farm roofing) is formed.

To accommodate the profiles exiting at two different levels, the cutoff die also has two levels Thehandling equipment for finished products beyond the cutoff die must be adjustable up and down to suitthe two product exit heights

Double-high mills save space, and the changeover time between two products is relatively short.However, because of the crowded condition, it is difficult to install side-roll stands, to make adjustment,

or to check the forming conditions

2.2.6 Rafted (Plated, Cassetted) Mills

The development of rafted mills was a major breakthrough in reducing roll change time from 8 hr ormore on a large panel mill (or 4 hr on a smaller mill) to between 30 and 45 min and as low as 5 min Themill has a bed on which the drive is located and the interchangeable plates are placed The plates areholding four to eight or more stands (Figure 2.20) The number of stands on a plate is usually restricted

by the lifting capacity (crane) at the user’s plant

Both the operator-side and the drive-side stands are typical operator-side-type stands, complete withshafts and tooling The drive-side stands usually have larger bearing blocks to accommodate pairs of conebearings which rigidly hold the shafts in position during the operation and when the operator-side stand

is removed for occasional roll change

To allow quick plate (profile) change, the drive must have quick disconnect/connect feature To furtherreduce the changeover time, only the bottom shafts are usually driven by the drive train firmly attached tothe bed All or some of the upper shafts can be driven by gears located at the drive-side end of the millshafts

The plates (rafts) must be accurately located on the mill bed The early “pin-type” locators arenot considered a good solution because it is difficult to repair the wear and tear on the pin and the hole

FIGURE 2.19 Double-high mill (Courtesy of Metform International Ltd.)

FIGURE 2.20 Rafted mill (Courtesy of Dreistern, Inc.).

quick disconnect clutch

mill bed plate (raft)

FIGURE 2.21 Construction of locating locks and mechanism for rafts.

Roll Forming Handbook2-12

(or sleeve) It is also troublesome to make

additional sets of rafts that fit exactly onto

the pins and, at the same time, provide accurate

shoulder alignment Two stops at the drive side of

the bed for the longer side of the plate and one stop

at each short side are sufficient for accurate

location (Figure 2.21)

To provide the shortest possible tool change

time, hydraulic pushers and clamps can be used

The upper surface of the mill bed does not have to

be fully machined It is sufficient to machine only

the protruding surfaces where the plates (rafts)

rest

The four lifting lugs attached to the plates

should provide a reasonable good balance, and the

lifting attachments (bars or chains) should not rub

against the tooling, shafts, or stands

To reduce changeover time, all the additional

components such as the entry guides, side-roll

stands, and straighteners should be permanently

attached to each set of plates

Saving of floor space can be achieved by storing

the plates of a profile on top of each other

(Figure 2.22) Tubes or other components (Figure

5.158) supporting the upper plate(s) should be

incorporated in the plate design

2.2.7 Side-by-Side Mills

Tool changeover time can further be reduced by mounting more than one set of tooling on the millshafts The simplest arrangement for the narrow sections is to install two sets of rolls on common shafts(Figure 2.23) The uncoiler, the prepunched press (if required), and the cutoff press are in line with one set

of rolls When profile change is required, the mill bed is moved sideways to align the second set of rollswith the other equipment The complete changeover takes less than 2 min Depending on the length of themill bed, two, three, or more pairs of supporting rolls (casters) are attached to the bottom of the mill bed.The rolls are moving on rails embedded into the floor Brass slides or linear bearings are also used to movethe mill sideways The movement is accomplished by electrical motor driven screws or by other means(e.g., hydraulic cylinders) Moving the mill bed against positive stops assures proper alignment.Occasionally, the mill remains in position while the uncoiler and the press (hydraulic) are movedsideways

The advantage of this “side-by-side” arrangement is the high up-time The disadvantage is that settingand adjusting one section will at the same time change the setting of the other section However, thisshortcoming can be easily overcome by using one or two more extra stands At the more frequentlyadjusted, critical passes, only rolls of one set are installed At the critical passes of the other section, onlyrolls for the other section are installed This arrangement ensures that adjusting one section will notinfluence the other section

It should also be noted that both sets of rolls must have the same pitch diameter and that recutting oneset of rolls will necessitate the recutting of the other During setup, the rolls closer to the shaft shoulders(drive side) should be set and tested first, followed by the roll set at the operator side

To keep the changeover time to a minimum, each set of rolls should have its own entry guide andstraightener If the product is curved (swept) after the operation, then two individual curving units

FIGURE 2.22 Storing plates on top of each other reduces floor space requirement (Courtesy of Ideal Roofing Co Ltd.).

are recommended for the sections If the prepunching has a different pattern, then either quick-changedie should be used or the dies should be capable of moving sideways Either the complete cutoff die or thecutoff die inserts should also be of the quick-change type.

Considering the advantages of the quick changeover, some customers are requesting to install threesets of rolls on the same shaft Obviously, the longer the shaft is, the more critical the shaft deflection will

be The recutting requirements (all sets have to be recut at the same time regardless of unequal wear) andthe number of additional stands to allow individual adjustments should also be considered Threesections with relatively loose tolerances may be tooled on common shafts, but the optimum is to haveonly two sets of rolls on the shafts

Occasionally, it is requested to install four, five, or six sets of rolls on the shafts This arrangement is notrecommended

Special side-by-side rolls are used in the lines that roll form two products at the same time from onecommon strip The common strip is slit into two at one point in the line This system is used to increaseproductivity to make two identical, or one left and one right section with each cut

If three, four, five, or more sections have to be roll formed, or if the sections are too wide to be placedeconomically side-by-side in one stand, then a “side-by-side stand” mill can provide the solution for quick

FIGURE 2.23 Side-by-side rolls on a mill.

Roll Forming Handbook2-14

changeover (Figure 2.24) In the side-by-side

stand mill, the common drive is usually at

the center of the mill bed The drive to each side

can be disconnected to avoid accidental start

Disconnect is usually automatic or mechanical,

not manual

Using side-by-side stands, one set of tooling

can form products, while the other

(discon-nected) stands can stay idle or the rolls can be

changed The changeover of the two sides is quick,

taking only a few minutes

If the sections are wide, then the two mill beds can be attached side-by-side (Figure 2.25) Thisarrangement can be taken a step further and the stands on both sides can be on rafts Rafting will reducethe changeover time of the rolls However, with such a complex arrangement, the cost-effectivenessshould be checked It is possible that two separate mills will provide better flexibility, productivity, andperhaps a lower overall cost

2.2.8 Pull-Through Mills

Roll forming mills can have nondriven forming rolls Most side-roll stands and often the top shafts arenot driven On rare occasions, none of the shafts/rolls is driven In the latter cases, the strip is pulledthrough the mill by other means while the idle (nondriven) rolls are doing the forming

When forming thin material (e.g., 0.003 to 0.020 in or 0.075 to 0.5 mm) in small mills, the strip can bepulled through by a “caterpillar” belt, winder drum, curving head, or by other means

If a thin material is joined to a thicker roll-formed section in their full lengths, then the mill, whichforms the thick material, can pull the thin material through a separate nondriven mill This method issometimes used in ceiling gridlines to join the prepainted “cap” to the galvanized structural part(Figure 2.26)

Pull-through roll forming has limited applications but it has other great potentials It can providestraight sections with better cross-sectional tolerances than other methods (see also Chapter 15)

FIGURE 2.24 Side-by-side stands on a common mill base.

FIGURE 2.25 Side-by-side panel mill (Courtesy of Metform International Ltd.)