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Manufacturing Processes - Introduction

Manufacturing: Introduction

Overview

The word manufacturing is derived from the Latin manu factus, meaning made by hand.

Manufacturing involves making products from raw materials by various processes or operations. Manufacturing is generally a complex activity, involving people who have a broad range of disciplines and skills and a wide variety of machinery, equipment, and tooling with various levels of automation, including computers, robots, and material-handling equipment. Manufacturing activities must be responsive to several demands and trends:

• A product must fully meet design requirements and specifications. • A product must be manufactured by the most economical methods in order to minimize costs.

• Quality must be built into the product at each stage, from design to assembly, rather than relying on quality testing after the product is made.

• In a highly competitive environment, production methods must be sufficiently flexible so as to respond to changing market demands, types of products, production rates, production quantities, and on-time delivery to the customer.

• New developments in materials, production methods, and computer integration of both technological and managerial activities in a manufacturing organization must constantly be evaluated with a view to their timely and economic implementation. • Manufacturing activities must be viewed as a large system, each part of which is interrelated to others. Such systems can be modelled in order to study the effect of factors such as changes in market demands, product design, material and various other costs, and production methods on product quality and cost.

• The manufacturing organization must constantly strive for higher productivity, defined as the optimum use of all its resources: materials, machines, energy, capital, labour and technology. Output per employee per hour in all phases must be maximized.

Many processes are used to produce parts and shapes. There is usually more than one method of manufacturing a part from a given material. The broad categories of processing methods for materials are:

Metal Casting Expendable mold and permanent mold . Metal

Forming & shaping

Rolling, forging, extrusion, drawing, sheet forming, powder metallurgy, and molding .

Plastics Molding & Forming

Blow Molding, CNC Machining, Centrifugal Casting, Continuous Strip Molding, Compression Molding, Profile Extrusion, Continuous Lamination, Injection Molding, Filament Winding, Thermoforming,Vacuum Forming, Pressure Bag Molding, Pressure Forming, Pulshaping, Twin Sheet Forming, Pultrusion, Liquid Resin Molding, Reaction Injection Molding (RIM),

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Rotational Molding, Resin transfer molding (RTM)

Rapid Prototyping

Stereolithography - SLA or SL, 3D Printing - 3DP, Selective Laser Sintering - SLS, Fused-Deposition Modeling - FDM, Solid-Ground Curing - SGC, Laminated Object Manufacturing - LOM, Multi-Jet Modeling - MJM, Direct Shell Production Casting - DSPC, Polyjet Technology, Laser Engineered Net Shaping - LENS

Joining Welding, brazing, soldering, diffusion bonding, adhesive bonding, and _{mechanical joining .}

Machining Turning, boring, drilling, milling, planing, shaping, broaching, grinding, ultrasonic machining, chemical, electrical, and electrochemical machining and high-energy beam machining .

Finishing Operations

Honing, lapping, polishing, burnishing, deburring, surface treating, coating and plating processes.

Introduction

When people hear the word "machining" they generally think of machines that utilize mechanical energy to remove material from the work piece. Milling machines, saws and lathes are some of the most common machines using mechanical energy to remove material. The tool makes contact with the work piece and the resulting shear causes the material to flow over the tool. All traditional forms of metal cutting use shear as the primary method of material removal. However, there are other sources of energy at work.

Chemical energy has a significant effect on every turning operation. Think of the effect that different kinds of coolants have on the cutting action of a tool. Some amount of chemical energy is being used in most metal cutting operations. All forms of manufacturing use more than one type of energy.

The category of nontraditional machining covers a broad range of technologies, including some that are used on a large scale, and others that are only used in unique or proprietary applications. These

machining methods generally have higher energy requirements and slower throughputs than traditional machining, but have been developed for applications where traditional machining methods were impractical, incapable, or uneconomical.

Nontraditional machining can be thought of as operations that do not use shear as their primary

source of energy. For example, abrasive water jet operations use mechanical energy, but material is removed by erosion.

Non traditional machining methods are typically divided into the following categories:

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1.

Mechanical - Ultrasonic Machining, Rotary Ultrasonic Machining, Ultrasonically

Assisted Machining

2.

Electrical - Electrochemical Discharge Grinding, Electrochemical Grinding,

Electrochemical Honing,Hone-Forming, Electrochemical Machining, Electrochemical Turning, Shaped Tube Electrolytic Machining, Electro-Stream

3.

Thermal - Electron Beam Machining, Electrical Discharge Machining, Electrical

Discharge Wire Cutting, Electrical Discharge Grinding, Laser Beam Machining.

4.

Chemical - Chemical Milling, Photochemical Machining

These machine tools were developed primarily to shape the ultrahard alloys used in heavy industry and in aerospace applications and to shape and etch the ultrathin materials used in such electronic devices as microprocessors.

Non-traditional Machining Processes

Abrasive Flow Machinging - (AFM)

Chemical Machining Chemical Milling

Electrical Discharge Grinding (EDG) Electrical Discharge Machining (EDM) Electrochemical Discharge Grinding (ECDG) Electrochemical Grinding (ECG)

Electrochemical Honing (ECH) Electrochemical Machining (ECM) Electrochemical Turning (ECT)

Electron Beam Machining (EBM) Ion Beam Milling - (IBM) Laser Beam Machining - (LBM) Laser Cutting

Laser Drilling

Photochemical Machining - (PCM) Plasma Arc Machining- (PAM) Ultrasonic Machining

WaterJet Machining AbrasiveJet Machining

Abrasive Flow Machining (AFM)

Abrasive Flow Machine (AFM) is a nontraditional machining process that is used to

deburr, polish, radius, and remove recast layers of critical components in aerospace,

automotive, electronic and die-making industries. Extrude Hone patented the

Abrasive Flow Machining (AFM) process in the 1960's as a method to deburr, polish

and radius difficult-to-reach surfaces. AFM operates by flowing an abrasive laden

viscoelastic compound through a restrictive passage formed by a workpart/tooling

combination. Inaccessible areas and complex contours both internal and external can

be finished economically and productively.

The workpiece is hydraulically clamped between two vertically

opposing media cylinders. The AFM process starts with the lower

cylinder filled with the proper volume of the abrasive laden media. The

media is then extruded through the work-piece and into the upper

media cylinder. The procedure is reversed as the media is fed back

through the part and into the lower cylinder. This combination of one

upstroke and one downstroke constitutes a complete AFM cycle.

AFM can work within areas that are inaccessible to conventional

manual finishing methods. Unlike conventional processes, AFM can be

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fully automated to provide a much more cost-effective method of finishing extrusion

dies and aircraft and aerospace components.

AFM is used in a wide range of finishing operations. It can simultaneously process

multiple parts or many areas of a single workpiece. Inaccessible areas and complex

internal passages can be finished economically and effectively. Automatic AFM

systems are capable of handling thousands of parts per day, greatly reducing labor

costs by eliminating tedious handwork. By understanding and controlling the process

parameters, AFM can be applied to an impressive range of finishing operations that

provide uniform, repeatable, predictable results. Anywhere that the media can be

forced to flow represents a practical application.

Chemical Machining

Chemical Machining aides in the manufacture of light gauge metal parts. The photo etching process (also called chemical etching and chemical milling) allows people to produce intricate metal components with close tolerances that are impossible to duplicate by other production methods. It is also known as chemical milling.

Applications -

Chemical Machining is utilized in the manufacturing of encoders, masks, filters, lead frames, flat springs, strain gauges, laminations, chip carriers, step covers, fuel cell plates, heat sinks, shutter blades, electron grids, fluidic circuit plates, reticles, drive bands, haptics, and shims.

Chemical Milling

Chemical Milling aides in the manufacture of light gauge metal parts. The photo etching process (also called chemical etching and chemical milling) allows people to produce intricate metal components with close tolerances that are impossible to duplicate by other production methods. It is also known as chemical machining.

Applications -

Chemical Milling is utilized in the manufacturing of encoders, masks, filters, lead frames, flat springs, strain gauges, laminations, chip carriers, step covers, fuel cell plates, heat sinks, shutter blades, electron grids, fluidic circuit plates, reticles, drive bands, haptics, and shims.

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Electrical Discharge Grinding - EDG

A process which is basically the same as EDM

Applications -

see - Electrical Discharge Machining (EDM)

Electrical Discharge Machining (EDM)

Electrical Discharge Machining (EDM), also known as spark erosion, employs electrical energy to remove metal from the workpiece without touching it. A pulsating high- frequency electric current is applied between the tool point and the workpiece, causing sparks to jump the gap and vaporize small areas of the workpiece. Because no cutting forces are involved, light, delicate operations can be

performed on thin workpieces. EDM can produce shapes unobtainable by any conventional machining process.

Ram EDM

A process using a shaped electrode made from graphite or copper. The electrode is separated by a nonconductive liquid and maintained at a close distance (about 0.001"). A high DC voltage is pulsed to the electrode and jumps to the conductive workpiece. The resulting sparks erode the workpiece and generate a cavity in the reverse shape of the electrode, or a through hole in the case of a plain electrode. Permits machining shapes to tight accuracies without the internal stresses conventional machining often generates. Also known as “die-sinker” or “sinker” electrical-discharge machining.

Wire EDM

A process similar to sinker electrical-discharge machining except a small-diameter copper or brass wire is used as a traveling electrode. The process is usually used in conjunction with a CNC and will only work when a part is to be cut completely through. A common analogy is to describe wire electrical-discharge machining as an ultraprecise, electrical, contour-sawing operation.

Applications -

EDM permits machining shapes to tight accuracies without the internal stresses conventional machining often generates. Useful in diemaking.

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Electrochemical-discharge grinding is a combination of electrochemical grinding and

electrical-discharge machining. The process is very similar to conventional EDM

except a grinding-wheel type of electrode is used. Material is removed by both

processes. Like any EDM process, the workpiece and the grinding wheel never come

into contact.

Applications -

Electrochemical Grinding (ECG)

Electrochemical grinding combines electrical and chemical energy for metal removal

with an EDM finish. It is a non-abrasive process and, therefore, produces precise cuts

that are free of heat, stress, burrs and mechanical distortions. It is avariation on

electrochemical machining that uses a conductive, rotating abrasive wheel. The

chemical solution is forced between the wheel and the workpiece. The shape of the

wheel determines the final shape.

Applications -

Electrochemical Honing - ECH

A process similar to electrochemical grinding involving the use of honing stones

rather than a grinding wheel.

Applications -

Electrochemical machining (ECM)

Electrochemical machining (ECM) also uses electrical energy to remove material. An electrolytic cell is created in an electrolyte medium, with the tool as the cathode and the workpiece as the anode. A high-amperage, low-voltage current is used to dissolve the metal and to remove it from the workpiece, which must be electrically conductive. ECM is essentially a deplating process that utilizes the

principles of electrolysis. The ECM tool is positioned very close to the workpiece and a low voltage, high amperage DC current is passed between the two via an electrolyte. Material is removed from the workpiece and the flowing electrolyte solution washes the ions away. These ions form metal

hydroxides which are removed from the electrolyte solution by centrifugal separation. Both the electrolyte and the metal sludge are then recycled.

Unlike traditional cutting methods, workpiece hardness is not a factor, making ECM suitable for difficult-to-machine materials. Takes such forms as electrochemical grinding, electrochemical honing and electrochemical turning.

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Electrochemical deburring is another variation on electrochemical machining designed to remove burrs and impart small radii to corners. The process normally uses a specially shaped electrode to carefully control the process to a specific area. The process will work on material regardless of hardness.

Advantages of Electrochemical Machining (ECM)

1. The components are not subject to either thermal or mechanical stress. 2. There is no tool wear during Electrochemical machining.

3. Non-rigid and open work pieces can be machined easily as there is no contact between the tool and workpiece.

4. Complex geometrical shapes can be machined repeatedly and accurately 5. Electrochemical machining is a time saving process when compared with conventional machining

6. During drilling, deep holes can be made or several holes at once. 7. ECM deburring can debur difficult to access areas of parts.

8. Fragile parts which cannot take more loads and also brittle material which tend to develop cracks during machining can be machined easily through Electrochemical machining 9. Surface finishes of 25 µ in. can be achieved during Electrochemical machining

Electrochemical Turning (ECT)

A variation of Electrochemical Machining

.

Applications -

Electron-beam Machining - EBM

In electron-beam machining (EBM), electrons are accelerated to a velocity nearly three-fourths that of light (~200,000 km/sec). The process is performed in a vacuum chamber to reduce the scattering of electrons by gas molecules in the atmosphere. The electron beam is aimed using magnets to deflect the stream of electrons and is focused using an electromagnetic lens. The stream of electrons is directed against a precisely limited area of the workpiece; on impact, the kinetic energy of the electrons is converted into thermal energy that melts and vaporizes the material to be removed, forming holes or cuts.

Typical applications are annealing, welding, and metal removal. A hole in a sheet 1.25 mm thick up to 125 micro m diameter can be cut almost instantly with a taper of 2 to 4 degrees. EBM equipment is commonly used by the electronics industry to aid in the etching of circuits in microprocessors.

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Ion Beam Milling - (IBM)

In simple terms ion beam milling can be viewed as an atomic sand blaster. The grains of sand are actually submicron ion particles accelerated to bombard the surface of the work mounted on a rotating table inside a vacuum chamber. The work is typically a wafer, substrate or element that requires material removal by atomic sandblasting or dry etching.

A selectively applied protectant, photo sensitive resist, is applied to the work element prior to introduction into the ion miller. The resist protects the underlying material during the etching process which may be up to eight hours or longer, depending upon the amount to be removed and the etch rate of the materials. Everything that is exposed to the collimated ion beam (may be 15" in diameter in some equipment) etches during the process cycle, even the resist.

In most micromachining applications the desired material to be removed etches at a rate 3 to 10 times faster than the resist protectant thus preserving the material and features underneath the resist.

Applications -

Ion Beam Milling is used in fabricating electronic and mechanical elements for a wide variety of commercial, industrial, military and satellite applications including custom film circuits for RF and Microwave circuits.

Laser-beam machining -- LBM

Laser-beam machining (LBM) is accomplished by precisely manipulating a beam of coherent light to vaporize unwanted material. LBM is particularly suited to making accurately placed holes. It can be used to perform precision micromachining on all microelectronic substrates such as ceramic, silicon, diamond, and graphite. Examples of microelectronic micromachining include cutting, scribing & drilling all substrates, trimming any hybrid resistors, patterning displays of glass or plastic and trace cutting on semiconductor wafers and chips.

Applications -

The LBM process can make holes in refractory metals and ceramics and in very thin materials without warping the workpiece. The laser can scribe, drill, mark, and cut thin metals and ceramics, trim resistors, and process plastics, silicon, diamond, and graphite with tolerances to one micron.

Laser Cutting

Laser cutting is the process of vaporizing material in a very small, well-defined area. The laser itself is a single point cutting source with a very small point, (0.001" to 0.020" / 0.025mm to 0.5mm) allowing for very small cut widths.

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The advantages of cutting with a laser make it a preferred choice over conventional cutting methods.

Laser Cutting Advantages

1. There is almost no limit to the cutting path; the point can move in any direction unlike other processes that use knives or saws.

2. The process is forceless allowing very fragile or flimsy parts to be laser cut with no support.

3. Since the laser beam exerts no force on the part and is a very small spot, the

technology is well suited to fabricating high accuracy parts, especially flexible materials. The part keeps its original shape from start to finish.

4. The laser beam is always sharp and can cut very hard or abrasive materials.

5. Sticky materials that would otherwise gum up a blade are not an obstacle for a laser. 6. Lasers cut at high speeds. The speed at which the material can be processed is limited only by the power available from the laser.

7. Cutting with lasers is a very cost effective process with low operating and maintenance costs and maximum flexibility.

Laser Drilling

Laser drilling is the process of repeatedly pulsing focused laser energy at a specific material.

The laser beam consistently drills holes down to 0.004" with little or no debris. Holes with length-to-diameter ratios of up to 50 can be drilled with reliable, high quality results. With lasers it is possible to drill in very difficult locations using mirrors to bend the beam. Laser drilling at very high rates, 1000 pulses per second or greater, is also possible.

Laser Drilling Advantages --

1. Using laser system software, the operator instantly can control hole shape and size to produce round, oval or rectangular holes, or any shape imaginable. This eliminates downtime due to tool changes.

2. Very small holes can be laser drilled in production. A focused spot can be as small as 0.1mm (0.004") in diameter.

3. Since the tool is a beam of light, the tool never needs to be replaced eliminating downtime because of punch breakage.

Photo Chemical Machining - (PCM)

Photochemical Machining - (PCM) components are produced by the photo-etching technique using a wide array of metal and alloys. This technique avoids burrs, no mechanical stresses are built into the parts and the properties of the metal worked are not affected. Hardened and

tempered metals are machined as easily as regular metals. The technique is ideal for machining thin metals and foils. Parts with very precise and

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intricate designs can be produced without difficulty. The photo chemical machining/milling processes can precisely etch lines and spaces on all types of metals (alloys: kovar, nickel, brass, beryllium, copper, stainless steel, aluminum, and others) with detailed accuracies. This is used for creating specialty flex circuits, plus in engineering of other rigid technologies. This results in a burr free part with very close tolerances.

Applications -

The technique is ideal for machining thin metals and foils. Parts with very precise and intricate designs can be produced without difficulty.

Plasma Arc Machining

Plasma-arc machining (PAM) employs a high-velocity jet of high-temperature gas to melt and displace material in its path. Called PAM, this is a method of cutting metal with a plasma-arc, or tungsten inert-gas-arc, torch. The torch produces a high velocity jet of high-temperature ionized gas called plasma that cuts by melting and removing material from the workpiece. Temperatures in the plasma zone range from 20,000° to 50,000° F (11,000° to 28,000° C).

It is used as an alternative to oxyfuel-gas cutting, employing an electric arc at very high temperatures to melt and vaporize the metal.

Applications -

The materials cut by PAM are generally those that are difficult to cut by any other means, such as stainless steels and aluminum alloys. It has an accuracy of about 0.008".

Ultrasonic Machining

Ultrasonic machining (USM) is a mechanical material removal process used to erode holes and cavities in hard or brittle workpieces by using shaped tools, high frequency mechanical motion, and an abrasive slurry. . A relatively soft tool is shaped as desired and vibrated against the workpiece while a mixture of fine abrasive and water flows between them. The friction of the abrasive particles gradually cuts the workpiece.

Materials such as hardened steel, carbides, rubies, quartz, diamonds, and glass can easily be machined by USM. Ultrasonic machining is able to effectively machine all materials harder than HRc 40, whether or not the material is an electrical conductor or an insulator

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Waterjet Machining

A water jet cutter is a tool capable of slicing into metal or other materials using a jet

of water at high velocity and pressure. It is often used during fabrication or

manufacture of parts for machinery and other devices. It has found applications in a

diverse number of industries from mining to aerospace where it is used for operations

such as cutting, shaping, carving, reaming.

The cutter is commonly connected to a high-pressure water pump (a local water main

does not supply sufficient pressure) where the water is then ejected out of the nozzle,

cutting through the material by bombarding it with the stream of high-speed water.

Additives in the form of suspended grit or other abrasives, such as sand and silicon

carbide, can assist in this process. Because the nature of the cutting stream can be

easily modified, water jets can be used to cut materials as diverse as fish sticks and

titanium.

Beyond cost cutting, the waterjet process is recognized as the most versatile and

fastest growing process in the world (per Frost & Sullivan and the Market Intelligence

Research Corporation) . Waterjets are used in high production applications across the

globe. They compliment other technologies such as milling, laser, EDM, plasma and

routers. No noxious gases or liquids are used in waterjet cutting, and waterjets do not

create hazardous materials or vapors. No heat effected zones or mechanical stresses

are left on a waterjet cut surface. It is truly a versatile, productive, cold cutting

process.

The most important benefit of the water jet cutter is its ability to cut material without

interfering with the materials inherent structure as there is no "heat affected zone" or

HAZ. This allows metals to be cut without harming their intrinsic properties.

The waterjet has shown that it can do things that other technologies simply cannot.

From cutting whisper thin details in stone, glass and metals; to rapid hole drilling of

titanium; to cutting of food, to the killing of pathogens in beverages and dips, the

waterjet has proven itself unique

History of Waterjets

WaterJet Cutting is a technology that has mainly evolved in the past two decades and

it has created ripples within the manufacturing industry during this time, due to its

versatility and flexibility in usage. Many types of water jets exist today, including

plain water jets, abrasive water jets, percussive water jets, cavitation jets and hybrid

jets.

Dr. Norman Franz is regarded as the father of the waterjet. He was the first person

who studied the use of ultrahigh-pressure (UHP) water as a cutting tool. The term

UHP is defined as more than 30,000 pounds per square inch (psi). Dr. Franz, a

forestry engineer, wanted to find new ways to slice thick trees into lumber. In the

1950's, Franz first dropped heavy weights onto columns of water, forcing that water

through a tiny orifice. He obtained short bursts of very high pressures (often many

times higher than are currently in use), and was able to cut wood and other materials.

His later studies involved more continuous streams of water, but he found it difficult

to obtain high pressures continually. Also, component life was measured in minutes,

not weeks or months as it is today.

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Dr. Franz never made a production lumber cutter. Ironically, today wood cutting is a

very minor application for UHP technology. But Franz proved that a focused beam of

water at very high velocity had enormous cutting power — a power that could be

utilized in applications beyond Dr. Franz's wildest dreams.

Only in the 1970s did the usage of water for cutting start advancing noticably. Today

the water jet is unparalelled in many aspects of cutting and has changed the way

products are manufactured.

AbrasiveJet Machining

Abrasive waterjet cutting systems (abrasivejet) use a combination of water and garnet

to cut through materials considered "unmachineable" by conventional cutting

methods. Using small amounts of water while eliminating the friction caused by

tool-to-part contact, abrasivejet cutting avoids thermal damage or heat affected zones

(HAZ) which can adversely affect metallurgic properties in materials being cut. The

ability to pierce through material also eliminates the need and cost of drilling starter

holes. Because abrasivejet cuts with a narrow kerf, parts can be tightly nested thus

maximizing material usage.

Abrasive waterjet can cut through materials ranging from 1/16 inch (1.6 mm) to 12

inches (305 mm) thick with an accuracy of ± 0.005 inch (0.13 mm). The typical

orifice diameter for an abrasivejet nozzle is 0.010" to 0.014" (0.25 mm to 0.35 mm).

The orifice jewel may be ruby, sapphire or diamond, with sapphire being the most

common. Diamond is recognized to last longer than the other two, but most operators

find that it is not worth the additional cost. A typical high-quality jewel assembly

consisting of a sapphire orifice and a precision stainless steel mount with integral

abrasive feed chamber costs about $50. A similar assembly using a diamond orifice

would cost several hundred dollars and does not provide a reasonable payback.

Ruby and sapphire are very similar in their life expectancy, neither having a distinct

advantage over the other. In theory, a jewel orifice should operate reliably until

dissolved solids and minerals in the water build up next to the water passage. The

jewel does not really fail, but it no longer produces a straight, smooth stream of water

because of scale build-up.

In reality, however, many jewels fail when struck by dirt or abrasive particles that

have managed to get upstream of the jet during nozzle changes or overhauls. This

causes the jewel to crack or pit, substantially altering water flow through the jewel.

Once water flow through the jewel is disturbed, the cut quality will be poor and the

mixing tube life will be shortened dramatically. A cracked $50 jewel assembly can

quickly ruin a $150 ceramic mixing tube. Many operators change the jewel orifice as

a matter of course whenever they overhaul a nozzle.

Abrasive waterjet is excellent for the cutting of complex shapes, and in fragile

materials such as glass, the high failure rate due to breakage and chipping of corners

during conventional processing is virtually eliminated. Whatever your industrial need,

abrasivejet is an accurate, flexible, and efficient cutting system.

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