Deep Drawing Process Quiz

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Questions and Answers

What effect does pressing a blankholder downward during deep drawing have?

It induces tensile stress in the blank.

It increases the thickness of the cup wall.

It increases the diameter of the blank.

It can reduce or eliminate wrinkling of the flange. (correct)

What primarily causes tearing of the cup wall in deep drawing?

Excessive vertical tensile stress due to punch force. (correct)

Insufficient blankholder force applied.

Inadequate lubrication between contacting interfaces.

High blank diameter relative to die cavity diameter.

In the context of producing aluminum beverage cans, what is the final diameter after redrawing the initial blank?

65 mm (correct)

90 mm

140 mm

75 mm

What does the punch force primarily contribute to during the deep drawing process?

Creating longitudinal tensile stress in the cup wall. (D) Signup and view all the answers

What is the role of friction and lubrication between contacting interfaces in the deep drawing process?

To facilitate smoother movement and reduce wear. (C) Signup and view all the answers

What is the primary purpose of punching in shearing operations?

To produce scrap material (D) Signup and view all the answers

When performing shearing operations, which factor does NOT influence clearance control?

Tensile strength of the material (D) Signup and view all the answers

What characteristic distinguishes fine blanking from conventional blanking?

Production of very smooth sheared surfaces (A) Signup and view all the answers

Which shearing process uses a pair of circular blades?

Slitting (D) Signup and view all the answers

What is the typical range for clearance in shearing operations?

2% to 8% of the thickness (B) Signup and view all the answers

What effect does increasing the thickness of the sheet have on the clearance requirement?

Increases the clearance requirement (C) Signup and view all the answers

Which of the following statements about punching and blanking is TRUE?

Blanking produces the component part while punching creates scrap (C) Signup and view all the answers

What is a key advantage of using a compound die in shearing operations?

Enables multiple operations in a single stroke (C) Signup and view all the answers

What does the bending force in sheet metal depend on?

The yield stress and length of the bend (A) Signup and view all the answers

What is the range of the factor k for different types of dies in bending operations?

0.3 to 1.3 (B) Signup and view all the answers

Which bending die type has the highest factor k value?

V-die (B) Signup and view all the answers

During flanging operations, what is notable about the edges of the flange formed without pre-punching?

They are rough (A) Signup and view all the answers

What is a characteristic of bead forming with two dies?

It typically requires a press brake (A) Signup and view all the answers

In the context of bending, what does P represent?

The maximum bending force (C) Signup and view all the answers

What happens to the edges of a tube during the flanging process?

They thin out (A) Signup and view all the answers

Which operation does not require pre-punching before the punch descends?

Flanging (A) Signup and view all the answers

What is the purpose of using internal mandrels or filling tubes with particulate materials during bending?

To prevent collapse of the tubes during bending. (B) Signup and view all the answers

Which technique is utilized to ensure that a tube cannot kink during bending?

Using a stiff, helical tension spring around the tube. (C) Signup and view all the answers

What is a benefit of applying compressive stresses during the tube forming operation?

It delays the occurrence of fracture. (C) Signup and view all the answers

In deep drawing, which component is responsible for holding the metal blank in place?

The blankholder. (B) Signup and view all the answers

Which of the following is NOT a variable in the deep drawing process?

Temperature of the environment. (B) Signup and view all the answers

What is the main function of the stripper ring during the deep drawing process?

To facilitate the removal of the formed part. (B) Signup and view all the answers

What is the primary equipment used in deep drawing to shape the metal blank?

A punch. (C) Signup and view all the answers

Which of the following describes an outcome of increasing the punch diameter in deep drawing?

It increases the likelihood of fracture. (A) Signup and view all the answers

What is the primary advantage of using sheet metal in manufacturing?

Lightweight and versatile shapes (C) Signup and view all the answers

Which type of steel is most commonly used for sheet metal due to its cost and properties?

Low carbon steel (D) Signup and view all the answers

In which situation is hot stamping primarily used?

To increase formability and decrease forming loads (D) Signup and view all the answers

What initiates the shearing operation in sheet metal forming?

Shear stresses using a punch and die (C) Signup and view all the answers

What characteristic surfaces result from the shearing process on the workpiece?

Burnished on the hole and slug with rough fracture surfaces (B) Signup and view all the answers

Which metals are highlighted for their corrosion resistance applications?

Aluminum and titanium (A) Signup and view all the answers

What is typically the first step in sheet metal forming operations?

Shearing from a larger sheet (C) Signup and view all the answers

What happens to the cracks during the shearing process?

They eventually meet and lead to complete separation (D) Signup and view all the answers

What is the primary function of lubrication in tool and die operations?

To reduce tool and die wear (A) Signup and view all the answers

Which of the following represents the two basic modes of deformation in sheet metal formability?

Stretching and drawing (D) Signup and view all the answers

In a cupping test, what is the indicator of formability for sheet metals?

The depth at which a crack appears (C) Signup and view all the answers

What happens to the outer and inner fibers of the material during the bending process?

Outer fibers are in tension and inner fibers in compression (A) Signup and view all the answers

What is a primary role of progressive dies in sheet metal forming?

To allow for high production rates with multiple operations (A) Signup and view all the answers

Which material is commonly used for manufacturing tools and dies in shearing operations?

Tool steel and carbides (A) Signup and view all the answers

What is the purpose of formability tests for sheet metals?

To assess the ability to change shape without failure (D) Signup and view all the answers

What does bending a sheet or plate impart to the part?

Stiffness by increasing its moment of inertia (A) Signup and view all the answers

Study Notes

Sheet Metal Forming

Sheet metal forming is a manufacturing process used to create complex shapes from sheet metal
A sheet metal part is produced using presses, called stamping.
Low carbon steel is frequently used due to cost-effectiveness and good strength/formability
Other materials, like aluminum and titanium, are sometimes used for specific applications (e.g., corrosion resistance, aerospace components)
Sheet metal forming can be performed at room temperature, or hot stamping can be used to increase formability.

Introduction to Shearing

Sheet metal forming begins with shearing to remove a blank from a larger sheet
Shearing uses a punch and a die to create shear stresses
Shearing creates cracks along the edges of the sheet and the slug, leading to separation.
Burnished surfaces on the hole and the slug result from contact, while rough fracture surfaces develop due to cracks.
A burr is a thin, raised edge at the sheared edge
Burr formation is influenced by clearance and material ductility.
Dull tool edges contribute to large burr formation
Excessive clearance results in rougher sheared edges, affecting subsequent processing.
Secondary operations may be required to smooth finished edges.

Punch Force

Punch force is calculated by multiplying shear strength by sheared area.
Factors include sheet thickness (T), total length sheared (L), and the Ultimate Tensile Strength (UTS) of the material.
Punch force decreases as clearance increases.
Friction between the punch and workpiece increases the punch force.

Other Shearing Operations

Shearing operations include punching and blanking.
Die cutting involves fine blanking (smooth sheared surfaces), slitting (using circular blades), and lancing (slitting to create tabs)
Processes are frequently done using a pair of circular blades, similar to a can opener.

Characteristics of Shearing Dies

Proper clearance is crucial for product formability and finish.
Clearance (c) ranges between 2% - 8% of sheet thickness. But can be smaller (1%) for fine blanking or higher (30%) in some cases.
Soft materials require tighter clearances, while hard materials require larger ones.
Larger clearances increase sheared area deformation, resulting in a rougher sheared edge, which might need further processing.

Punch and Die Shape

Shapes are often beveled to control shearing location.
Compound dies allow multiple operations on the same part at a single station.
Progressive dies are used for high-volume, multi-stage operations

Formability Tests

Sheet metal formability measures its ability to change shape without failing

Cupping Test

The Erichsen test is a cupping test to assess formability by stretching the metal until a crack appears.
Punch depth at crack point is a key indicator of formability.

Bending Sheets, Plates, and Tubes

Bending is a common metal forming operation, used in numerous applications
Outer fibers experience tension, while inner fibers experience compression.
Bend allowance considers the neutral axis length, bend angle, bend radius, and material thickness.

Minimum Bend Radius

Minimum bend radius is where cracks first start in outer fibers.
Bending strain and crack formation depend on bend radius, material thickness, and angle.

Springback

Springback refers to the tendency of a bent material to return to its original shape slightly after the force is removed.
Factors influencing springback is the material’s elastic modulus, yield strength, and the ratio of bend radius to material thickness.
Springback calculations can be approximated using bend radii, before and after.
Negative springback is also possible when the bend goes back toward a direction opposite of the expected bend angle because of the absence of constraint.

Various techniques like forming, channels, joggles, hemming (flattening), two stage lock seam, offset forming, and different types of bead forming are used to shape metals.
Tools and dies materials used in shearing operations often include tool steel and carbides. Lubrication is important to minimize wear.

Deep Drawing

Cylindrical and box-shaped parts are formed using deep drawing.
The process forces a flat blank into a die cavity, thus forming a cup
Determining the maximum punch force is complex, but formulas can be used based on blank diameter, sheet thickness, material strength and the punch/die radii.
Wrinkling can often occur in the drawn flange.
Wrinkling can be reduced by applying a blank holder.

Metal Forming Processes in Can Manufacturing

The process for manufacturing two-part aluminum cans is detailed
Sequence of manufacturing operations needed to shape from a raw blank to a finished can. Methods used in forming operations including blanking, deep drawing, redrawing, ironing, doming, necking, and seaming.

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Description

Test your knowledge on deep drawing techniques, including the effects of blankholder pressure, causes of material tearing, and the role of punch force. This quiz also explores the final dimensions in aluminum can production and the significance of friction and lubrication during the process.