Deformation

l Deformation is a change in the shape or size of an object due to an applied force (the deformation energy in this case is transferred through work) or a change in temperature (the deformation energy in this case is transferred through heat).Can be a result of tensile (pulling) forces, compressive (pushing) forces, shear, bending or torsion (twisting).

Deformation Process

l Permanent (plastic) deformation of a material under tension, compression, shear or a combination of loads.

l Deformation processes transform solid materials from one shape into another. The initial shape is usually simple and is plastically deformed between tools, or dies, to obtain the desired final geometry and tolerances with required properties.

Types of Deformation Process

l Types of Deformation

– Bulk flow in (3) dimensions

– Simple shearing of material

– Compound to simple bending

– Combination of above

Deformation Process

l Stresses used to produce change

– Tension

– Compression

– Shear

– Combination in multiple axis

l (2) Classifications

– Bulk = Significant change in surface area, thickness and cross section reduced, and overall geometry changed.

– Sheet = Some deforming of material, but initial material thickness remains the same

Forming Processes

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Process Variables

l (3) Classification

– Independent

» Controlled by the engineer

– Dependent

» Process determines outcome

– Independent / Dependent

l Figure 15-1 Schematic representation of a metalforming system showing independent variables, dependent variables, and the various means of linking the two.

Work Ranges

l (2) Types of mechanical work where material undergoes plastic deformation

l Hot Working (HW)

l Cold Working (CW)

Definition of HW vs. CW

l HW is performed above the recrystallization temp of the material and CW is done below the recryllization temp of the material.

l Recystallization Temp- “The approximate minimum temp at which complete recyrallization of a cold worked metal occurs within a specified time.”

» -Heat Treaters’s Guide, American Society for Metals

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Definition of HW vs. CW

l Approximate temperature ranges

– HW - .6 melt temp. of the material

– WW - .3 to .6 melt temp of the material

– CW - less than .3 of the material

» Example - 1020 CRS 950 - 1300F

Hot Working

l When HW a metal is in a plastic state and is easily formed. The forces required to deform the metal are less than CW. Some mechanical properties of the metal are improved due to process characteristics.

l At elevated temperatures, metal microstructures are rebuilding continually through the recrystallization process which allows for much higher deformation.

Advantages to HW

l Porosity in metal is largely eliminated

l Impurities (inclusions) are broken up and distributed through the metal

l Course grains are refined

l Due to grain refinement, the physical properties are generally improved

» Ductility and resistance to impact are improved

» Strength is increased

Advantages to HW

Figure 15-3 Cross section of a 4-in.-diameter case copper bar polished and etched to show the as-cast grain structure.

Figure 15-4 Flow structure of a hot-forged gear blank. Note how flow is parallel to all critical surfaces. (Courtesy of Bethlehem Steel Corporation, Bethlehem, PA.)

Advantages to HW

l Amount of energy necessary to change the shape of the raw material in a plastic state is far less than if the material was “cold.”

l Economical compared to CW

Disadvantages to HW

l High working temp. can result in rapid oxidation/scaling of surface = poor surface finish

l Generally, close tolerances are hard to control

l Equipment and tool maintenance costs are high

Primary HW Processes

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l Rolling

l Forging

l Extrusion

l Pipe & tube manufacturing

l Drawing

Rolling

l Heated metal is passed between rotating rolls to reduce the cross-section.

Rolling

l One of the primary first process to convert raw material into finished product.

l Starting material (Ingots) are rolled into blooms, billets, or slabs by feeding material through successive pairs of rolls.

» Bloom - square or rectangular cross section with a thickness greater than 6” and a width no greater than 2x’s the thickness

» Billets - square or circular cross section - - smaller than a bloom

» Slabs - rectangular in shape(width is greater than 2x’s the thickness), slabs are rolled into plate, sheet, and strips.

Forging

l The plastic deformation of metals, typically at elevated temperatures, using compressive forces exerted through a die to conform the metal to a desired shape.

l Process advantages:

– Closing of voids in the metal

– Reduced machining time

– Improve the physical properties of the starting metal

l Process disadvantages:

– Possible scale inclusions in forging

– Tooling cost can be high

– Usually not used for short production runs

Forging Methods

l Open-Die Drop Hammer - heated metal is placed between dies—a force is delivered with a steam hammer.

– Accuracy is not good

– Complicated shapes are difficult to produce

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Forging Methods

l Upset forging

– Grip a bar—heat the end—forge into desired shape

» Product examples

l Bolts

l Engine valves

l Impression Die Drop Hammer Forging - Hot pliable metal is forces into the shape of closed impression dies. This process is typically performed in a progressive method through a series of dies to control the flow.

– 2 Types of drop forge hammers

» Steam

» Gravity

l Press Forging

– Large….thick work

– Slow Squeezing action penetrates entire work piece producing uniform deformation

– Dies are typically heated to:

» Assist surface flow

» Reduce surface heat loss

» Assist in obtaining close tolerances and surface finish

– Two types of presses -- mechanical and hydraulic

» Hydraulic - up to 50,000 tons

Hot Extrusion

l A plastic deformation process in which metal is forces under pressure to flow through a single, or series of dies until the desired shape is produced.

l Advantages

– Wide variety of shapes

– High production rates

– Improved microstructure and physical properties

– Close tolerances are possible

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– Economical

– Design flexibility

Pipe, Tube, and Wire Manufacturing

• Tube - Butt or electric welding and Piercing

Drawing

l Flat sheet or a plate of metal is forced into a recess with a depth more than several times the starting materials thickness.

Cold Working

l CW is done below the recrystallization point of the material. In CW, greater forces are required to transform the raw metal into the desired shape.

l One major advantage…..as the grain deformation proceeds greater resistance to the action is building resulting in improved strength and hardness (strain hardness).

l CW is a high volume production process.

l Similar processes as HW—major differences include

l Forces required

l Temperature range

l Equipment specifications

l Advantages

l No heat required

l Better surface finish

l Superior dimensional control---little or no secondary operations

l Strength, fatigue, and wear properties are improved

l Improved machinability

l Disadvantages

Increased stress in material—strain hard Roll Alignment Roll Alignment , specifically, is the alignment and measurement of roll parallelism in

plant machinery that is typically used to feed sheet materials. Typical industrial applications include:

Paper and Pulp manufacture Printing Works Textile Mills All types of Sheet Manufacturing

Problems associated with the misalignment of Rolls include: Drift and tracking of sheet materials during feed Wrinkling and Breakages in paper / material Uneven gloss rate in paper manufacture High scrap rates of material

Roll Alignment ProcessIndustrial Applications for Roll Alignment

The Headbox: The Foil Section: The Press Section: The Dryer Section: The Winder:

The Coating Section:Roll Alignment - Head Box

It is important that the breast roll is parallel to the apron board. If the air gap differs, it will cause problems with the consistency of the paper. It is also important that the apron board is straight and the slice gap is correct in order to get a uniform output of paper pulp on to the forming table.

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Benefits: Uniform paper structure and thickness Reduced rate of scrap paper Increased efficiency in the dewatering process and possibility to increase

production speed Reduced risk of breaking the slice tip

Roll Alignment - Dryer Section In this section, the problems are similar to the press sections, although we would

like to point out the problem with wrinkles and breakages in the paper sheets. The amount of rolls in the web path is large in the dryer section and increases the importance of roll parallelism.

Benefits: Increased uptime Increased time between felt changes Reduced scrap production Increased product quality Possibility to increase production speed

Roll Alignment - Forming Table In this section, parallelism between the breast roll and the drive rolls is important,

or the drift and wear of the wire will be affected. The surface of the paper sheet is affected if the dandy roll is not parallel to the forming table. The pick up roll and the couch roll may cause breakages and wrinkles if they are not kept parallel, and the suction process may be affected. The levelling of the forming table is another important factor in this section, that will especially affect the de-watering pro-cess and the deterioration of the foils.

Benefits: Efficient de-watering process and uniform fibre structure will improve the paper

quality Increased de-watering capability gives possibility to Increase production speed Increased lifetime of the wire Reduced energy consumption for the vacuum pumps

Roll Alignment – Winders Poor parallelism between the calendar rolls, the reel drum and spool may create

problems with a high rate of scrap paper as a result. Also the paper may drift sideways during the reeling, creating problems with wrinkles and difficulties when cutting the paper.

Benefits: Less scrap paper

Increased production capacity

Roll Alignment - Finishing Calendars The parallelism is important in the calendar, both vertically and horizontally, or the

roll nip will differ over the roll length. In some calendars, there is a nip offset that has to be considered.

Benefits: Uniform gloss Reduced scrap production Increased time between roll replacement Possibility to increase production speed

Turret Punching

is a process, where work piece are punched to make a desired hole of a metal sheet. it is a CNC machine used for performing punching (a turret puncher) to a material such

us sheet of metal or plastic . Turret punching is a cold work process. This entails that material properties remain

unchanged as they are not exposed to thermal impact during machining.Process process produces shapes by selectively removing material from sheet metals. These sheets

are clamped into the machine on a table that is programmed to move to a specific X/Y location within the matrix of the machine. The correct punch shape and size is selected at the turret and the machine actuates the punch to produce the desired hole.

Punching Characteristics

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Punching Characteristics Punching is the most cost effective process of making holes in strip or sheet metal

for average to high fabrication It is able to create multiple shaped holes Creates a burnished region roll-over, and die break on sidewall of the resulting hole

Materials supportedSheet Metals including:

Aluminum Galvanized Steel Carbon Steel Stainless Steel Brass Bronze Copper Monel Plastic

Advantages Fast and accurate over and over again without variation. Take a less time of work than the manual punching machine. CNC punching machines commonly handle up to 1200 hits per minute and many

have automated loading systems allowing for continuous operation.

All kinds of metal can be turret punched, also hard stainless spring steel and some polymere types can be turret punched.

Disadvantages A turret punching machine is an expensive machine It cannot punch a metal with a thickness of 6mm. Occupies large space in the work area. Warping may occur if many holes are punched or much material is removed from

the sheet

Rotary Swaging Process

Rotary swaging is a very fast metal forming process, eg. 4-6 parts per minute. In addition to the speed of manufacture, the swaging process itself improves the mechanical strength properties of the work piece due to the work hardening phenomenon.

This would not be possible with conventional metal cutting operations. Rotary swaging can be applied up to a work piece length of some 1000 mm.

Usually a cold working process, used to reduce the diameter, produce a taper, or add point to a round work piece. It can also impart internal shapes in hollow work pieces through the use of a mandrel (the shape must have a constant cross-section.

Mechanism of Rotary Swaging Process

A solid rod or tube is subjected to a radial impact by a set of rotating dies wherein a radial movements of the dies are obtained by rotating them between pairs of opposite rollers in a cage. The work piece is stationary and dies rotate striking the work piece in the centre of the die retainer or housing. Constant hammer blows gradually reduce the metal in size. It is then taken to another machine and reduces further in size until the desired size is obtained.

The dies close over the work piece and form the material. When the backers are in-between two roll positions, the centrifugal forces will move them apart, making it possible for the die to open, while the dies are rotating around the work piece. The operation continues several times and the result is a reduced round cross section of tube, bar or wire.

Advantages of Rotary Swaging Process

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Raw material/s

Into the machine

Desired design

Start of the punch process

Finished Products

1. Net-shape production the achievable tolerances are extremely tight so that final machining is in most cases not required. This enables significant material savings and reduces the number of production stages, resulting in lower piece prices.

2. Broad applicability, significant weight savings rotary swaging can produce a multitude of different external and internal forms. Weight savings in the range of 30% - 50% can generally be achieved by rotary swaging versus conventional production methods.

3. High product quality The uninterrupted grain flow of the material together with the work hardening resulting from the process increases the strength of the work piece. The quality of swaged surfaces is at the level of ground surfaces.

4. High forming ratios, material freedom Rotary swaging achieves high forming ratios without requiring hot forming. The favorable distribution of stresses during forming and the homogenous course of processing permit the forming of even brittle materials. Aging

5. Cold and hot forming Rotary swaging forms materials in the cold, semi-hot and hot temperature range.

6. Environmental acceptability Unlike many other forming processes, rotary swaging does not require any surface treatment on the blank. The oil, if required, is in a closed cycle.

7. Versatility Rotary swaging machines have short change-over times. The swaging dies and the machine setting can be changed within a few minutes.

8. Short production times high efficiency The construction of rotary swaging machines permits combination of several processing modules for efficient multi-station transfer lines so that net-shape parts can be produced with high outputs. The robust easy to maintain construction ensures high efficiency rates.

Disadvantage of Rotary Swaging Process

The process variables affect the quality of swaged product such as dimensional precision, surface roughness of the product. Defect could be found to occur at a value of more than 2.0 mm/rev in forming speed. The dimensional precision of swaged product depends on the percentage reduction of outer diameter and forming speed.

Key Benefits of RS

1. Improves mechanical strength property of the work piece due to the work hardening phenomenon.

2. Weight optimization combined with forming of internal geometries. Since the material volume of the workpiece remains constant, a reduction of the outside diameter of a solid bar would lead to an increased length of the same workpiece. In the case of a drive shaft for a passenger car made of a solid bar, 20% material savings can be obtained by rotary swaging compared to traditional metal cutting techniques.

3. A third key benefit of rotary swaging is the excellent surface quality, and is directly comparable with a ground surface. More specifically, a surface roughness of Ra 0.1-0.3 can be obtained for internal geometries, and on outer surfaces for recess swaging Ra 0.6-1.0 can be guaranteed.

4. A fourth benefit that certainly shall not be neglected is the very long and reliable service life of the swaging tools. As a rule of thumb, the tools do not wear out but crack, which means that only good parts are swaged until tool breakage. Another rule of thumb is that swaging tools made of tungsten carbide have a 4-5 times longer service life than tools made of tool steel. So for large production series, carbide tools should be applied.

Two Types of Rotary Swaging Machine

There are two basic types of rotary swaging machine, the standard (also known as a tagging machine), and the butt swaging machine. A butt swaging machine works by having sets of wedges that close the dies onto the workpiece by inserting them between the annular rollers and the dies, normally by the use of a foot pedal. A butt swaging machine can allow a work piece to be inserted without the dies closing on it, for example a three foot workpiece can be inserted 12 inches and then the dies closed, drawn through until 12 inches remain and the dies are then released, the finished work piece would then, for example, be four feet long but still of its initial diameter for a foot at each end.

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Spring Forming

A spring is a device that changes its shape in response to an external force, returning to its original shape when the force is removed. The energy expended in deforming the spring is stored in it and can be recovered when the spring returns to its original shape.

Types of Spring

Extension spring

a coiled spring whose coils normally touch each other; as a force is applied to stretch the spring, the coils separate.

Compression spring

a coiled spring with space between successive coils; when a force is applied to shorten the spring, the coils are pushed closer together.

Torsion spring

designed so the applied force twists the coil into a tighter spiral. Common examples of torsion springs are found in clipboards and butterfly hair clips.

Raw Materials

Steel alloys are the most commonly used spring materials. The most popular alloys include high-carbon (such as the music wire used for guitar strings), oil-tempered low-carbon, chrome silicon, chrome vanadium, and stainless steel

Spring Forming Processes

Coiling

One consists of winding the wire around a shaft called an arbor or mandrel. This may be done on a dedicated spring-winding machine, a lathe, an electric hand drill with the mandrel secured in the chuck, or a winding machine operated by hand cranking. A guiding mechanism, such as the lead screw on a lathe, must be used to align the wire into the desired pitch (distance between successive coils) as it wraps around the mandrel.

Thicker wire or bar stock can be coiled into springs if the metal is heated to make it flexible.

Hardening

Whether the steel has been coiled hot or cold, the process has created stress within the material. To relieve this stress and allow the steel to maintain its characteristic resilience, the spring must be tempered by heat treating it. The spring is heated in an oven, held at the appropriate temperature for a predetermined time, and then allowed to cool slowly.

Finishing

Grinding. If the design calls for flat ends on the spring, the ends are ground at this stage of the manufacturing process. The spring is mounted in a jig to ensure the correct orientation during grinding, and it is held against a rotating abrasive wheel until the desired degree of flatness is obtained

Shot Peening This process strengthens the steel to resist metal fatigue and cracking during its lifetime of repeated flexings. The entire surface of the spring is exposed to a barrage of tiny steel balls that hammer it smooth and compress the steel that lies just below the surface.

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Coating. To prevent corrosion, the entire surface of the spring is protected by painting it, dipping it in liquid rubber, or plating it with another metal such as zinc or chromium. One process, called mechanical plating, involves tumbling the spring in a container with metallic powder, water, accelerant chemicals, and tiny glass beads that pound the metallic powder onto the spring surface

The Future

Springs that support keys on touchpads and keyboards

A manufacturer of test equipment used in semiconductor production has developed a microspring contact technology.

A manufacturer of test equipment used in semiconductor production has developed a micro spring contact technology.

Three Roll Forming

Roll Forming is a continues bending operation in which a long strip of metal (typically coiled metal) is passed through consecutive set of rolls. Each performing only an incremental part of the bend until the desired cross sectional area profile or obtained. Passes on three consecutive set of rolls . Forming plate ,sheet, bars, beams, angles,. Rollers on a pyramid like positions.

Advantages

1. Increased production and less downtime2. Defects are easier to control3. Lengths are not limited

Dies- material can jam or double-up in production material conveyor between the prenotch press and the roll former equal to or greater than the longest part.

Conclusion

Roll forming method is better than the conventional method terms of labour productivity. It can be used of work hours to install structural components by using roll forming is less compared to the cast in situ-method.

Typical applications

-rooftop

- road barriers

Forging

-manufacturing process involving the shaping of metal using localized compression forces/metal is heated and is shaped.

Resultant of forged metal

1. Drawing- increase length ,decrease cross sectional2. Upsetting- decrease length, increase cross sectional3. Squeezing- change length, change cross sectional area

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