[PDF] INTRODUCTION TO SHEET METAL FORMING PROCESSES PDF IntroToSheetMetalFormingProcesses.pdf

order to obtained the desired result : a part with a given quality HARDWARE Most problems in sheet metal forming come from a bad control of holding, Holding controls the shape of the blank and the contact between the blank and the Plastic deformation leaves some stresses locked through metal thickness After

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[PDF] Metal forming processes

plastically to take the shape of the die geometry The tools Deep (or cup) drawing: In this operation, forming of a flat metal sheet into a hollow or concave deformation provides the opportunity for desirable directional properties; (5) since no

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Advantages: • No material waste in bringing the material to the desired shape of will become more directional dependant Rolling Spinning It is the plastic deformation of metal above its re-crystallisation temperature (that depends on the

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Cast product will have any shape size and complexity deformation process, theories used for the prediction of plastic deformation etc , For easy In Stretch Forming operation metal sheet is placed on a contoured die of required shape and

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Cold working may be defined as plastic deformation of metals and alloys at a temperature below the This is required for those parts which have a bend shape

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In order to plastically deform a metal, a force must be applied that will stretching a rubber band, then releasing it, and having it go back to its original shape This is called elastic deformation Once the stress on a metal increases past metals manufacturing and forming processes, which can involve extrusion , drawing,

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many emerging technologies, these advantages have made them a hot topic in Table 1 Classification of the metal forming processes based on deformation type shape, and desired mechanical properties, the rolling procedure and Forging is usually defined as plastic deformation of a bulk metal to a predetermined

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plastic deformation, using sophisticated tooling, is known as metal forming For the last process can be classified into bulk and sheet metal forming resistance, and reliability are desired in materials used for forming and have to be metals into desired shapes is often limited by the occurrence of material instability

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•Other Deformation Processes Related to Forging •Extrusion Metal forming operations which cause significant shape change by to cause plastic flow into desired shape •Performed as cold have the reverse of desired shape • Products

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Introduction to sheet metal forming processes

INTRODUCTION TO SHEET METAL

FORMING PROCESSES

The documents and related know-how herein provided by SIMTECH subject to contractual conditions are to remain confidential. This documentation and related know-how shall not be disclosed, copied or reproduced by any means, in whole or in part, without the prior written permission of SIMTECH.

© 1999 SIMTECH. All rights reserved

Product names are mentioned for identification only and may be registered trademarks.

SIMTECH

37 rue des Acacias, 75017 Paris

FRANCE

Tel: (33) (1) 56 68 80 00

Fax: (33) (1) 56 68 80 06

Introduction to sheet metal forming processes

INTRODUCTION: EVOLUTION OF INDUSTRIAL STAMPING

Back in 1985, the development cycle of a stamped part looked more or less like this (a sequential series of operations stemming from a single style design): P

Process Dev.

42 months

Pdt

Product Design

Soft/Hard

tool builtSoft/Hardtool tryout STYLE

DESIGNProduct Devpt.

Today, people look at it rather as a sort of funnel, where key decisions are taken on the basis of different factors and alternative choices. style design proces product-process validationtooling CAM tryout production

18 months

Introduction to sheet metal forming processes

OVERVIEW: THE STAMPING SYSTEM AND STAMPING DESIGN

Like all complex system, stamping can be decomposed in hardware and software. By hardware we mean factors that cannot be changed from one operation to another. Conversely, by software we mean factors that the operator can change in order to obtained the desired result : a part with a given quality.

HARDWARE SOFTWARE

Press

Press set-up

Tools Material

Lubrication

The highlighted areas represent the components of the stamping design.

Introduction to sheet metal forming processes

What is a stamping press ?

A stamping press is a machine that houses the stamping tools (tooling) and carries them around according to the kinematics indicated by the user (process set-up). The knowledge of the press used for a stamping operation provides us with useful clues regarding:

Value and distribution of restraining forces

Tool deformation caused by stamping forces

Contact and/or gap between tools and blank

However, we should recall that, at the moment when the die design is carried out, the press is usually not yet known, so that its characteristics are rather a factor of noise than a useful information. Therefore, it will be important to have a design that is robust with respect to the press type.

Introduction to sheet metal forming processes

What is a stamping tool? What is process design?

die blankholder punchblankholder

Run-offs

design area

GLOSSARY:

Design surface

Part as designed to fit in the car (after trimming)

Blankholder

surface Surfaces that hold the blank before the forming operation, including the restraining

Production

surface/run-offs Junction between the two former surfaces, protecting the design surface and controlling material flow

Dieface

Run-offs + blankholder

Process design is the ensemble of operations leading from the design geometry to the dieface.

Introduction to sheet metal forming processes

What is a stamping operation?

A sheet formed part is usually obtained through a number of operation (phases) final surface intermediate surface Each operation can be decomposed in several phases. It may be necessary to model each of them

Gravity fall

Holding

Forming

Trimming, flanging

Springback

Most problems in sheet metal forming come from a bad control of holding, restraining and springback.

Gravity fall

The blank adapts to the blankholder shape

BLANKHOLDER

PUNCH original flat blank gravity deformed blank

Holding

The die pushes on the blankholder and squeezes the blank

Introduction to sheet metal forming processes

Forming

The die goes down until it squeezes the blank onto the punch

Introduction to sheet metal forming processes

First the volume of the part is created:

this is mostly controlled by the production surface and by the restraining system

Last the geometry details are formed:

this is controlled by the geometry of the part

Trimming and springback

Plastic deformation leaves some stresses locked through metal thickness. After the extraction from the tools these stresses are released originating a different shape than that of the tools. Springback before trimming is sometimes important for the design of the tools and robots of the press. Springback after trimming may change the shape of the part to the point that it is impossible to assemble.

Introduction to sheet metal forming processes

STAMPING PROCESS DESIGN

Deliverables of process design

Dieface design

Delivered in drawing or, most often

nowadays, CAD format.

Dieface design specifies the geometry

of the dieface for each of the stations considered.

Cutting pattern

Cutting pattern profile is also delivered in drawing or CAD format. It specifies the geometry of the punching tool prior to the actual stamping operation. Production constraints usually force the use of simple cutting patters. In practice, some basic shapes are used: rectangle trapeze rectangle w/ cuts rectangle w/ slot

Introduction to sheet metal forming processes

Stamping cycle

Stamping cycle is the description of all the operations leading to the production of the finished stamped part. A typical stamping cycle includes:

One or more stamping stations

One coining station

One trimming station

One punching and flanging station

Introduction to sheet metal forming processes

Dieface design

The simplified die addendum: basic geometry feature of the dieface Although an actual dieface is a rather complicated system of surfaces, some basic geometry features can be identified. Such basic features can be summarized as follows :

Stamping direction : identified on

the basis of minimum undercut, inertia moment or straightness of projected characteristic lines.

Punch radius line : identified after

flange development and protection

Die entry line : joins the punch line

to the blankholder, with an opening angle to avoid undercuts

Blankholder : can be developable

(conical or ruled) or quasi- developable. Non-developable blankholders may give rise to wrinkling problems during the holding phase. punch radius line

Die entry line

stamping directionblankholder

Other run-offs components.

Typically, a dieface contains local

elements (sausages) designed to control punch/blank impact and/or to stretch locally the material.

Introduction to sheet metal forming processes

How many steps ?

Coining

Flanging

Trimming and springback reduction

Introduction to sheet metal forming processes

MATERIAL DEFORMATION DURING SHEET METAL FORMING

Deformation analysis

Principal strain plane

The analysis of deformation in sheet metal forming is often based on the two principal membrane strains 1 and 2

Most often, the maximum principal strain

1 is positive in a forming operation. Hence, only half of the strain plane is considered (actually, three quarters).

Deformation pairs relative to different

points of a stamped part are often plotted on such a half-plane.

This information can be drawn either

from FE simulation or from experimental analysis (grids).

The analysis of such deformation plots

gives useful insights into the mechanics of a forming operation. drawing expansion 1 2

The deformation plot lends itself to

several interesting considerations.

Lines departing from the origin are

equivalent to constant strain mode 12 1 2 pure ex pansion plane strainplanestress pure shea r

Introduction to sheet metal forming processes

We can identify:

A line of pure expansion, where

A line of plane strain, where

0 1 H

A line of plane stress, where

0 2 V

A line of pure shear, where

Further, based on the principle of

conservation of volume, lines at 45° 321
cst represent the loci of constant thickness.

For each of these lines, the thinning

t, 1 2 relative to the initial thickness t 0 can be computed from basic rules of mechanics : e t t 21
1 0

Grid analysis

Introduction to sheet metal forming processes

Modes of deformation

In this chapter, we address the topic of material deformation, following the jargon of die engineers rather than of the mechanical engineers. The reader is encouraged to compare the deformation modes described here and in the preceding chapter.

Definition

In sheet metal forming practice, we distinguish five basic modes of deformation:

STRETCHING: The material is expanded in

both directions. This mode of deformation is found mostly on smooth bottoms of shallow parts and in hydroforming processes.

DRAWING: This mode is typical the

material flow from the flange towards the inner part of the die.

BENDING/UNBENDING: This is a cyclic

deformation (most often associated with plane strain). It is found on the die entry line as well as in drawbeads.

STRETCH-AND-BEND: This mode is

associated to flanging operations for which the bending line is concave. l1 l0

COMPRESSION-AND-BEND: This mode is

associated to flanging operations for which the bending line is convex. l1 l0

Introduction to sheet metal forming processes

Remember:

The designer thinks in

term of geometrical features: wall, angel, flanges, etc... wall anglewall flangeUpper surface ... but the die engineer sees the part as a collection of areas, often quite well separated, where different deformation modes occur. baxial expansion expansion bending/unbending bending/unbending drawing stretch-bend compression-bend

Introduction to sheet metal forming processes

FACTORS CONTROLLING DEFORMATION

In the following, several factors controlling the stamping operation are analyzed. However, it should be pointed out that a hierarchy exists among the different factors, which is partially echoed by the traditional product development workflow.quotesdbs_dbs19.pdfusesText_25

[PDF] [PDF] INTRODUCTION TO SHEET METAL FORMING PROCESSES

Introduction to sheet metal forming processes

INTRODUCTION TO SHEET METAL

FORMING PROCESSES

© 1999 SIMTECH. All rights reserved

SIMTECH

37 rue des Acacias, 75017 Paris

FRANCE

Tel: (33) (1) 56 68 80 00

Fax: (33) (1) 56 68 80 06

Introduction to sheet metal forming processes

INTRODUCTION: EVOLUTION OF INDUSTRIAL STAMPING

Process Dev.

42 months

Product Design

Soft/Hard

DESIGNProduct Devpt.

18 months

Introduction to sheet metal forming processes

OVERVIEW: THE STAMPING SYSTEM AND STAMPING DESIGN

HARDWARE SOFTWARE

Press set-up

Tools Material

Lubrication

Introduction to sheet metal forming processes

What is a stamping press ?

Value and distribution of restraining forces

Tool deformation caused by stamping forces

Contact and/or gap between tools and blank

Introduction to sheet metal forming processes

What is a stamping tool? What is process design?

Run-offs

GLOSSARY:

Design surface

Blankholder

Production

Dieface

Run-offs + blankholder

Introduction to sheet metal forming processes

What is a stamping operation?

Gravity fall

Holding

Forming

Trimming, flanging

Springback

Gravity fall

The blank adapts to the blankholder shape

BLANKHOLDER

Holding

Introduction to sheet metal forming processes

Forming

Introduction to sheet metal forming processes

First the volume of the part is created:

Last the geometry details are formed:

Trimming and springback

Introduction to sheet metal forming processes

STAMPING PROCESS DESIGN

Deliverables of process design

Dieface design

Delivered in drawing or, most often

Dieface design specifies the geometry

Cutting pattern

Introduction to sheet metal forming processes

Stamping cycle

One or more stamping stations

One coining station

One trimming station

One punching and flanging station

Introduction to sheet metal forming processes

Dieface design

Stamping direction : identified on

Punch radius line : identified after

Die entry line : joins the punch line

Blankholder : can be developable

Die entry line

Other run-offs components.

Typically, a dieface contains local

Introduction to sheet metal forming processes

How many steps ?

Coining