Flexible Product Structure of Draw Bending Toolsets in SolidWorks

Kashif, Muhammad

Patil, Abhijeet

THESIS WORK 2008Knowledge based Engineering

Postal Address: Visiting Address: Telephone:

Box 1026 Gjuterigatan 5 036-10 10 00 551 11 Jönköping

Flexible Product Structure of Draw Bending Toolsets in SolidWorks

Kashif, Muhammad

Patil, Abhijeet

This thesis work is performed at Jönköping Institute of Technology within the subject area Knowledge based Engineering. The authors are responsible for the given opinions, conclusions and results.

Supervisor: Joel Johansson

Credit points: 15 or 20 points (D-level)

Date:

Archive number:

Postal Address: Visiting Address: Telephone:

Box 1026 Gjuterigatan 5 036-10 10 00 551 11 Jönköping

Abstract

Abstract

1

Abstract

Preparation of Toolsets for rotary draw bending of Aluminum tubes requires evaluation of orders from the customers that whether the tube bending is possible on available machines or not. A quick response to customers will definitely increase the chances of getting contract, which can be possible; thanks to advances in technology, by implementing design automation in the preparation of fixtures and tooling necessary for tube bending. A Knowledge based system containing production floor, analytical knowledge and rules based on empirical data from trial manufacturing of fixture’s production can definitely be pivotal in automation of metal forming.

When a customer puts his order, Knowledge Base system (KBS) is given input data to run knowledge objects. In case of more detailed input data, other objects are run when a more precise calculation for detailing is required. The main theme behind the system is to make use of knowledge objects containing information on inputs, outputs and constraints to implement the knowledge.

Main approach of this work is to integrate CAD & KBS in design and manufacturing of tube products.

Keywords: Knowledge Design system, Design automation, Rotary Draw bending

2

1 INTRODUCTION..................................................................................................................................3

2 PRINCIPLES OF TUBE BENDING PROCESS.....................................................................5

2.1 COLD BENDING OF TUBES............................................................................................................52.1.1 Rotary draw bending...................................................................................................62.1.2 Compression bending..................................................................................................7

2.2 DESIGN PARAMETERS FOR TUBE BENDING PROCESS.................................................................82.2.1 Minimum bending radius............................................................................................82.2.2 Wall factor........................................................................................................................82.2.3 Springback.......................................................................................................................92.2.4 Bending factor................................................................................................................92.2.5 Difficulty Factor............................................................................................................10

2.3 DIFFICULTY IN TUBING PROCESS DESIGN..................................................................................10

3 IMPLEMENTATION OF A KNOWLEDGE-BASED SYSTEM........................................11

3.1 WHY A KNOWLEDGE-BASED SYSTEM HELPS?...........................................................................13

4 A COMPUTERIZED SYSTEM FOR DESIGN OF ROTARY DRAW BENDING TOOLS.........................................................................................................................................................14

4.1 SYSTEM OVERVIEW.....................................................................................................................144.2 FORMULAS AND RELATIONS FOR TUBE BENDING MACHINE SELECTION.................................15

5 TOP DOWN MODELING............................................................................................................15

6 CASE STUDY.....................................................................................................................................17

6.1 SOLID MODELING APPROACH......................................................................................................176.2 CONFIGURATION..........................................................................................................................186.3 KNOWLEDGE DESIGN STUDIO....................................................................................................19

7 RESULTS...........................................................................................................................................26

8 CONCLUSION & FUTURE PERSPECTIVE.........................................................................31

8.1 IRREGULAR PROFILE SECTIONS..................................................................................................31

9 ACKNOWLEDGEMENT...............................................................................................................31

10 REFERENCES.............................................................................................................................32

11 Search words.........................................................................................................................................33

1 Introduction

3

Cold bending of metal tubes plays very important role in production method since metal tubes are widely used in a various engineering products like automobile, aircraft, air conditioner, air compressor, exhaust systems and fluid lines. Even though cold bending of tubes is an old metal forming process, it is becoming a precision metalworking process and requires assurance of high quality. (Cassidy, 1988). There are several methods for cold bending like rotary drawing bending, compression bending, empty bending, ram bending, rolling bending, etc ( Kervick and Springborn, 1966). Bending machine includes of various range from hydraulic bending, hand benders, to fully computerized CNC benders. Knowledge-based system (KBS) development plays very innovative role in tubing production industry. Since customer’s demand on complex tubing parts and tight tolerances leads to increase in chances of defects and failures of tubing parts. Various failures are undesired deformation, inaccuracy of bend angles and geometry, wall thinning, flattening, wrinkling and cracks. These errors are closely associated with the selection of bending methods, tool/die design, die set conditions, machine setup, material effects, a number of bending process parameters such as minimum bending radius, springback, wall factor, etc. Thus optimization of process for cold bending of metal tubes plays crucial role and raising the demand to develop knowledge-based system (KBS). The KBS techniques have proven effective in solving a complex manufacturing problem where the optimal decision-making is based on the integration of facts, rules, equations, expertise, production data, and process knowledge.

Knowledge-based system assists in variant design of products. During product development process same data, formulas and rules are applied repeatedly to adapt well established concepts to new specifications. Design automation is “Engineering IT-support by implementation of information and knowledge in solutions, tools, or systems that are pre-planned for reuse and support the progress of the design progress. The scope of the definition encompasses computerized automation of tasks that directly or indirectly are related to the design progress in the range of individual components to complete products” (Cederfeldt, 2007). Automation plays important role in cutting lead time during manufacturing. Taking into consideration of automation engineers have implemented automation like use of spreadsheets, Matlab files, Mathcad or databases. In all those files a lot of knowledge is stored and since this knowledge is applied on the products developed by the company, it will be a part of the trademark. The system built containing the corporate knowledge should be transparent and easy to understand fro users and for future

Introduction

developers. The knowledge should be user friendly. Thus there are high requirements for documentation both on the system architecture and the knowledge it contains. In addition to this Elgh and Cederfeldt points out the following requirements that such a system should meet (Elgh F., Cederfeldt M., 2005):

Low effort of developing Low level of investment User readable and understandable knowledge Transparency Scalability Flexibility Longevity Ease of use

The objective of the work presented is to develop a connection between already developed KBS and Solid works (a CAD/ CAM application) for design of the tube bending process that integrates metal tubing theories, tube bending process knowledge, and human expert’s experience. The KBS developed can be used to aid tubing engineers design tubing tools and dies, determine the optimal bending process parameters.

2 Principles of Tube bending process

Two principles apply to both cold bending methods – rotary draw bending and compression bending. First, the material on the inside of the bend must compress. Second, the material on the outside of the neutral axis must stretch.

2.1 Cold bending of tubes

The most common processes for cold bending of pipes and tubes are draw bending, compression bending, roll bending, etc. Ram bending was probably the first pipe bending method used to cold-form while rotary draw bending and compression bending are more popular nowadays. Both of them can be embodied in either manual benders or powered bending machines. In addition, empty bending is also widely used in combination with the above two bending methods, because of less setup time, less tooling cost, and no lubricant needed. Generally, cold bending requires a center forming die, either fixed or rotated (for rotary draw bending), a pressure die and a clamping or following die. In the rotary draw bending, a mandrel and a wiper die are often used. The components of a die set are shown in Fig. 1.

Introduction

Fig. 1 Components of a bending die set 1

2.1.1 Rotary draw bending

Rotary draw bending is a widely used method for bending tubes, particularly for tight bending radii and thin wall tubes. The characteristic of this bending method is that the center bending die, which is used to form the angle of tube parts, rotates with the work piece together, and the die set sometimes is equipped with a wiper and a mandrel, depending on the size and shape of workplace. A die set up for a rotary draw bending is shown in Fig. 2.

In Rotary-draw bending, at one end rotating center die forms the tube to the radius of the die. Clamp Die secures the pipe to the die. The pipe bending machine rotates the die to the desired bend angle and pressure die forces the pipe to conform to the die radius. After the pipe bending process, the operator extracts the mandrel from the pipe, releases the clamp, then removes the bent pipe from the machine. With proper tooling, this pipe bending process is capable of producing high quality, tight-radius bends for a wide range of applications.

Introduction

Fig. 2 Rotary draw bending 1

2.1.2 Compression bending Compression bending is one of the most common method, simplest and economic operation for bending metals tube parts. As commonly used today for bending with heart-shaped tooling. An older method of bending in which the tube is clamped against a stationary bend die and the pressure die sweeps the tube around the bend die to form the bend.  This differs importantly from rotary-draw bending in that the point of bend is the point of contact between the pressure die and bend die and the clamping die is replaced by a movable following die. The following die by means of a rotary arm presses the workpiece around the bend die to form the desired shape. Therefore the point of bend moves through space, which makes the use of a mandrel impossible. Die set of compression bending is shown in fig. 3.

Introduction

Fig. 3 Compression Bending 1

Distinguish Parameters

Rotary draw bending Compression bending

Movement of center die

Yes No

Movement of pressure die

No / Yes Yes

Use of mandrel and wiper

Yes No

Line of tangency in space

Fixed Not fixed

2.2 Design parameters for tube bending process

There are many factors to be considered for tube bending process. The basic parameters are minimum bending radius, springback, wall factor, bending factor and empty factor.

Introduction

2.2.1 Minimum bending radiusIn practice, an empirical formula for determining the minimum bending radius, Rmin is in wide use (Cassidy, 1988):

Where D is the outside diameter of the tube, and E’ is the percent elongation of the tube material.

2.2.2 Wall factorWall factor (WF) is the ratio of the tube outside diameter (D) to the wall thickness (t) (Gillanders, 1984):

It is a rule of thumb for assessing the difficulty of a tube bend:  The higher the wall factor, the more difficult the bend.  The rationale behind this rule is that a wall that is thin relative to the tube outside diameter requires more support at the point of bend to prevent wrinkling or collapse.  As a practical matter, the higher the wall factor, the more likely a mandrel and a wiper are needed to achieve good bend quality in rotary-draw bending.  The wall factor needs to be considered in conjunction with other factors, such as the Bend factor, to fully gauge the difficulty of a bend.

2.2.3 SpringbackOn release of the external loads, the tension stresses on the one side of the tube and the compressive stresses on the other side create a net internal bending moment or residual stresses. The residual stresses cause a springback or a change of the bending angle, Δθ, in the reverse direction of bending and a change of bending radius, ΔR, as shown in Fig. 4.

Introduction

Fig. 4 Changes of bending angle and radius before and after springback

2.2.4 Bending factor

Bending factor (BF) is described as the ratio of bending centerline radius (R) over the outside diameter of the tube (D) (Gillanders, 1984):

BF =

It is a unit of radial measurement peculiar to tube bending. It is the sweep of the arc.  The minimum degree of bend is about five degrees; the maximum degree of bend in rotary-draw bending is 180 degrees.

2.2.5 Difficulty Factor

Difficulty factor =

As the Bend factor decreases and the wall factor increases, the tube is less resistant to bending. As a result, it has a greater tendency to collapse rather than follow the form of the bend. Consequently, the material must be contained physically—surrounded at all points, internally and externally—where the bend takes place, to prevent tube collapse and any resulting deformities, such as wrinkles. This is needed

Introduction

in the tangent area, predominantly where the tube changes from a straight to a bent section and also where the material flows ahead and behind of the tangent point.The bend die, clamp die, and pressure die provide this containment to some extent and can be used in applications in which the difficulty factor (wall factor divided by Bend factor) is low and the tube is less prone to collapse. However, more complex applications require more support and containment. A mandrel inside the tube and a wiper die behind the tangent point and opposite the pressure die provide adequate containment, prevent collapse, and accommodate material flow. (Barry Rooney, 2005)

2.3 Difficulty in tubing process design

Tooling and die play an extremely important role in cold bending of metal tube products, and are directly related to most failures in tube production. Common failures and defaults in metal tube bending parts can be classified as: (Z. Jin Et al, 2001)

Deformation (wall thinning, flattening, wrinkling) as shown in Fig. 5.

Inaccuracy (over bending, under bending, twisting, beyond the linear dimension tolerance)

Breakage/crack Dents/marks

Fig.5: Tube Flattening Wrinkling Wall thinning

Introduction

Since tube bending is influenced by many technical factors related to bending structure, bending radius, material, wall thickness, diameter, tooling/die selection and condition, bending methods, lubrication, and operating parameters, etc., it is often difficult to achieve an optimal design of the tube bending process, in particular for bending parts with complex configuration and geometry requirements.

3 Implementation of a knowledge-based system

Global industrial competition requires enterprises to use innovative technologies for manufacturing and provision of goods and services in the shortest possible time frame with minimum cost. To achieve the goal of assuring short development cycles for new products, they are developing a process-based knowledge-driven product development environment by employing information technology. One major emphasis is knowledge-based engineering (KBE), which focuses on acquiring, storing, and utilizing knowledge for design and manufacturing. One of the applications of KBE is the knowledge-based system (KBS), which represents an interactive computer-based decision-making tool that uses both factual and heuristic data acquired from domain experts for problem solving.

The KBS shows the decision maker how to reduce setup time based on expertise embedded in the knowledge base as rules. (Kim and Arinze, 1992).The success of a KBS critically depends on the amount of knowledge embedded in the system. (HAO XING Et al, 2002). KBS are used in many diverse applications such as financial planning, manufacturing, tax planning, and equipment design; in fact, they are more useful than expert systems that attempt to totally replace the decision makers. (Goul Et al, 1992)

Introduction

Fig.6 Components of KBS (A. Hopgood, 2001)

Knowledge-based system (KBS) differs from conventional program on the bases of the structure. Domain knowledge is closely tangled with software for controlling the application in conventional program. While in knowledge-based system, the two roles are performed separately. In general there are two Modules which are as follow:

a) Knowledge Moduleb) Control Module

Knowledge module is called knowledge base and control module is called the inference engine. The separation of knowledge module and control module make KBS easy to add new knowledge. The knowledge-base system approach is more straightforward. So editing of knowledge is easier. The knowledge base may be rich with various forms of knowledge. So, for simplicity we state that knowledge base

Introduction

contains rules and facts. (A. Hopgood, 2001). “Expert systems are a type of knowledge-based system designed to embody expertise in a particular specialized domain. An expert system is intended to act as a human expert who can be consulted on a range of problems that fall within his or her domain of expertise”. (A. Hopgood, 2001). Inference engines can be classified on the base of type and involvedness of knowledge with which they deal.There are two types of inference engines which are as follow:

a) Forward-chainingb) Backward-chaining

Forward-chaining is also called as data-driven while backward-chaining is also called goal-driven. A knowledge based system when works in forward-chaining approach takes the available information and generates many derived facts. Since the output is not predictable this may lead to new solution to a problem. But it can also prove waste of time due to irrelevant information. Data-driven approach might be useful when we wish to have some data for analysis problems while backward-chaining approach is more beneficial when our requirement of solution is strongly focused.The expression of knowledge in a knowledge base can be addressed once the knowledge is known. For particular domain knowledge can be acquire by three approaches which are as follow:

a) The system learns automatically from the problem.b) The builder of the knowledge-based system is a domain

proficient.c) The knowledge is teased out of a domain.

3.1 Why a knowledge-based system helps?

A KBS is a computer program that has a knowledge module and a control module. A knowledge module is a knowledge base that stores all experts’ knowledge and experience in the form of facts or rules. A control module is then used to find out the result through all kinds of knowledge; it is thus called inference engine. With the KBS approach, all relevant process knowledge and experts’ experience can be logically integrated together to provide engineers with an effective tool in tubing design and manufacturing.

4 A Computerized system for design of Rotary draw bending tools

Introduction

Because of the complex nature in tube bending, only engineers with many years of design experience would own the knowledge for correct design of tube bending processes. On one hand it is difficult for a young engineer without such a rich experience to determine the effective tubing process with minimum potential failures. On the other hand, even for experienced engineers, negligence would often result in unwanted consequence.

Therefore, there is a need for developing an expert system that can be used to aid the design of tube bending processes.

4.1 System overview

It is proposed that decision support/aiding systems, such as computer-aided software engineering tools that are primarily designed to assist a decision maker, when embedded with knowledge, may induce users to learn more about problems as they interact with the system. (Antony a and Santhanamb, 2006)

In this work a system is used that meets most of the requirements mentioned in the introduction. The built in system is developed by object oriented programming in Visual Basic.Net accessing necessary relations and data from MS Excel files and apply it to bending tools solid modeled in SolidWorks.

4.2 Formulas and Relations for Tube bending machine selection

A lot of research has been done on the elastic and plastic analysis of tube bending and there are various derived equations available for tube bending analysis. In this work, we have taken formulas of section modulus and bending moment of circular tubes from the research work of “Plastic-deformation analysis in tube bending by (N.C. Tang, 2000)”

Circular Tube:

Introduction

D: Outer diameter of circular tubed: Inner diameter of circular tubeW: Section ModulusM: Bending moment

k: a geometry parameter of the tube =

σ: Material yield strength

Section Modulus for circular tube= W =

Bending Moment for circular tube =

Machine Capacity is selected on the basic of how much maximum bending moment that a tube bending machine can cope with.

5 Top Down Modeling

In bottom up design method, designers model the parts separately keeping in mind the assembly. When models are completed they are assembled together as per design criteria. Since the parts, modeled separately, contains no assembly information between them therefore when we brought them together, there are always some discrepancies like poorly aligned surfaces, not possible mates and often incomplete assembly because of not applicable assembly constraints and feature’s failure because of modification. In case of these inconsistencies, if someone wants to correct these, one has to alter the models one by one so that each part becomes compatible for each other. This takes much effort to detect and alter the models and frustrating for the designers. Therefore approach used in solid modeling of the draw bending toolsets is Top down assembly modeling.

Top down design means a series of unique capabilities, that address the problems and challenges that engineers face when designing large assemblies. These capabilities range from the ability to easily control the assembly at the top-level; the ability to make wide scale changes from a single location and know that the changes will propagate to all levels of the design; and the ability to allow large teams to share development tasks and communicate critical design criteria easily and quickly while remaining confident that all of the components will fit seamlessly in to the final product.

Introduction

A critical aspect of top down methodology is the communication of design data from the assembly to its individual components via a centralized-location.

Benefits of Top Down modeling approach include task distribution, concurrent modeling, and managing external references. By declaring models to 2D layouts you can distribute the global parameters and datums; using geometry features you can copy references from one model to another.

In this Work, we first captured the whole design intent and product structure of the draw bending toolsets. In the second step, after determining the critical information of the design, we put it on the higher level of assembly structure and then communicated to the lower levels i.e. components. In case of change in the parameters in the assembly structure, that is the way it is in this work, causes an automatic updating of the components.

Selection of the suitable toolsets for required tube diameter and bend radius is done on the basis of bending moment. In this work, we have two fictitious toolsets named as Silfax and Cooler. Knowledge Design Studio takes the parameters’ values and name of the suitable toolset for tube bending from MS Excel files and sends this information to Top down assembly. As a result of it, in Solidworks, parameters’ values are incorporated in that particular toolset.

6 Case Study

6.1 Solid Modeling Approach

There are two options for a 3D modeler to do Top down Modeling.

1. Creating Blocks/layers2. Creating Derived sketches

At first, we started Top Down modeling by using block approach. In block approach we captured the design intent of components and then we made assembly from these sketches/blocks. But the problem we faced with this approach was that parameters were not being updated

Introduction

in the Assembly, when we sent parameter’s information to SolidWorks via Knowledge Design Studio.

Fig.7. Block of Silfax 1

Fig.8 Block of Cooler 1

Therefore we shifted to another approach which was by creating sketches in the assembly mode and then we derived those sketches in

Introduction

particular components. When we sent parameter’s information to the assembly, 3D models were updated accordingly. Results obtained from this approach are displayed in the next chapter.

6.2 Configuration

Handling of different toolsets can be done very easily in SolidWorks by creating configurations as much as you would like to. In configurations we can suppress any feature that we don’t want to be in a specific configuration. In this thesis work, according to our requirement, we created two configurations of the tube bending toolsets named as Cooler and Silfax. We made the cooler’s features suppressed for Silfax and vice versa.

Fig.9 Configuration 1

6.3 Knowledge design studio

We first created the domain with (.xml extension). Then we added required parameters to the newly form domain. All the parameters except machineselection have float type. While machineselection parameter has configuration type.

Introduction

Fig.10 Creating Domain 1

Fig.11 Adding parameters to Domain 1

Introduction

Once parameters have been defined we create objects. In creating new object we selected the type in general tab as heuristic. All parameters which are required to calculate objects are added to input tab. The result of object which is to be calculated is placed in output tab. In implementation tab we have given excel file as application. When we have added inputs and output parameters, we have selected their cell location to the parameters value location in excel file.

Fig.12 Creating new object 1

Introduction

Fig.13 Implementation 1

Introduction

Fig.14 Excel datasheet 1

Introduction

Fig.15 Parameters entry 1

Thus we have created four objects. Which are as follows:a) bendratiob) sectionmoduluscircularc) bendingmomentcirculard) machineselection

Introduction

Fig.16 Required objects 1

Once we have created objects then we execute the calculation. After calculation we check the selected configuration/ tube bending tool set.

Fig.17 Execution 1

Introduction

Fig.18 Checking 1

After checking the results, we send the parameters and selected tool set information to SolidWorks.

Introduction

7 Results

Below are the incorporated results. Parameter form is taken from Knowledge Design studio before and after changes of tube parameters’ and the other is taken from SolidWorks which are as follows:

1) Cooler die-set ( Fig. 6 & 7) 2) Silfax die-set ( Fig. 8 & 9)

Introduction

Fig. 19 Cooler die-set before change of parameters

Introduction

Fig.20 Cooler die-set after changes of parameter

Introduction

Fig. 21 Silfax die-set before changes

Introduction

Fig. 22 Silfax die-set after changes in parameters

8 Conclusion & future perspective

Tube bending is a complicated operation that is influenced by many factors, such as tooling, material, tube geometry, bending methods, machine setting up, operators’ skills, etc. Using expert system techniques that incorporate human experts’ knowledge and intelligence is an effective means for design of tube bending processes and guidance to production.

Artificial Intelligence methods or knowledge-based systems (KBS) in manufacturing are beneficial to increase efficiency, reduce production costs, and improve quality. For the tube bending fabrication industry, the knowledge-based system can assist the engineers with tool and die design, and the production foremen and workers with trouble shooting and quality improvement. Furthermore, the KBS will provide a guide to select a correct method of tube bending production and to reduce the percentage of defective parts, so as to increase the production efficiency, to reduce the labor time and material waste, and save the overall costs significantly.

Introduction

8.1 Irregular profile sections

This work is applicable on tubes with circular sections. However it is desirable to develop rules for tubes with rectangular and irregular sections also.

9 Acknowledgement

We are extremely grateful of Mr. Joel Johansson, our Thesis instructor, whose guidance and support led us to the completion of our thesis work. In fact Knowledge Design studio is his brilliant invention. We are grateful to SAPA Group as well for their support in providing us their tube bending machine specifications.

10 References

1. JOHANSSON J., A Flexible Design Automation System for Toolsets for the Rotary Draw Bending of Aluminum Tubes, ASME 2007 International Design Engineering Technical Conferences & Computers and Information in Engineering ConferenceSeptember 2007, DETC2007-34310

2. Z. Jin, S. Luo, X. Daniel F., KBS-aided design of tube bending processes, Engineering Applications of Artificial Intelligence 14 (2001) 599–606

3. Tang N.C., Plastic deformation analysis in tube bending, International journal of pressure vessels and piping 77 (2000) 751-759

4. Elgh F.,CEDERFELDT M., A design automation system supporting design for cost-Underlying method, system applicability and user experiences, International conference on concurrent engineering, ISPE CE 05, Fort Worth,2005

5. CEDERFELDT M., Planning design automation- A structured method and supporting tools, Doctoral Thesis, Chalmers University of Technology Göteborg, Sweden,2007

Introduction

6. Cassidy, V.M., 1988. No-mandrel system speeds tube bending. Modern Metals 8, 75–78.7. Gillanders, J., 1984. Pipe and Tube Bending Manual Gulf

Publishing Company, Houston.8. Barry Rooney, November 8, 2005.Tight bend radii, thin walls

create need for wiper dies. 9. HAO XING, SAMUEL H. HUANG, and J. SHI, 2002, Rapid

development of knowledge based systems via integrated knowledge acquisition

10.Solomon Antony a and Radhika Santhanam b , 2006, Could the use of a knowledge-based system lead to implicit learning?

11. S. Kim and B. Arinze, A knowledge-based decision support system for set-up reduction, Decision Sciences 23 (1992) (6), pp. 1389–1407.

12. M. Goul, J.C. Henderson and F.M. Tonge, The emergence of artificial intelligence as a reference discipline for decision support research, Decision Sciences 23 (1992) (6), pp. 1263–1274.

13. Adrian A. Hopgood, 2001, Intelligent systems for engineers and scientists, CRC Press.

11 Search words

A

artificial intelligence.........................................31

B

bend angle...........................................................6bend factor..........................................................9bending factor.....................................................9bending moment................................................15bottom up..........................................................15

C

CAD....................................................................1center from die....................................................5centerline radius..................................................9circular..............................................................15clamp...................................................................6cold bending........................................................4collapse...............................................................9Compression bending..........................................7cooler.................................................................16

crack..................................................................10

D

dents..................................................................10design intent......................................................15design parameters................................................8die sets...............................................................16difficulty factor.............................................9, 10

E

empty bending...............................................5, 33excel..................................................................16

F

failure................................................................10fixture..................................................................1flattening.............................................................9following die.......................................................7formulas............................................................10

Introduction

I

inner diameter...................................................15Introduction.........................................................3irregular profile.................................................31

K

KBE...................................................................10KBS...............................................................1, 31knoweldge base system.....................................14knowledge base system.............................1, 3, 31

L

layout.................................................................15

M

mandrel...........................................................5, 6minimal bending radius.......................................7minimum bending radius....................................8

O

outside diameter..................................................8

P

parameters.........................................................16pressure die.....................................................5, 7

R

relation..............................................................15rotary draw bend.................................................1rotary draw bending............................................4

S

section modulus................................................15silfax..................................................................16solidworks.........................................................16spring back......................................................8, 9stationary.............................................................7

T

tangent...............................................................10top down design................................................15twisting..............................................................10

W

wall factor...........................................................8wall thickness......................................................8wall thinning.......................................................9wiper...................................................................5work piece...........................................................5wrinkling.............................................................9

Y

yield strength.....................................................15