Заключение

В данной статье эксперт Art Hedrick представил обзор промышленной штамповки металла и описывает различные виды карьерного роста, имеющиеся в этом секторе.

Нет никаких сомнений, что штамповка резко изменила нашу жизнь. Предметы общего хозяйства, такие как стиральные и сушительные машины изготавливаются с использованием процессов холодной листовой штамповки. Предметы, которые мы часто воспринимаем как должное, например, столовые приборы, которые мы используем для еды, горшки и кастрюли, когда мы готовим и автомобили, когда мы ездим, производятся частично методами листовой штамповки металлов. Банки для напитков, зажигалки, гильзы от огнестрельного оружия, даже некоторые виды твердых золотых украшений изготавливаются с помощью этого процесса.

Современное развитие листовой штамповки осуществляется по следующим направлениям: - замена литых кованых деталей на штампованные или штампосварные; - улучшение существующих и создание новых технологических процессов; - применение штамповки в мелкосерийном производстве с использованием универсальных штампов и поэлементной штамповки;

- снижение расхода металла за счет внедрения безотходного и малоотходного раскроя, повышение точности расчета заготовок и т.д.; - повышение точности деталей; - увеличение производительности за счет механизации и автоматизации процессов штамповки;

Дальнейшее совершенствование процессов листовой штамповки идет в основном по пути создания новых ресурсо- и энергоемких технологических процессов, создания новых методик расчета технологических режимов штамповки, обеспечивающих корректность принятия инженерных решений.

Проведя анализ патентной литературы можно сказать, что в данной области Россия имеет больше технологий, чем какая либо иная страна. Используя эти патенты, я буду создавать новую установку для изготовления детали Обейчайка.

Список литературы

1. http://www .thefabricator.com April 2009

2. http://www.fips.ru

3. http://www.unilib.neva.ru/rus/lib

Приложение 1

Metalworking professionals who possess diverse proficient skills have an edge in a tight job market. In this first installment in a series, tool-and-die expert Art Hedrick presents an overview of the metal stamping industry and describes the various careers available in the sector.

Editor's Note: This series presents an overview of metal stamping. Part I focuses on the various careers in the metal stamping industry. Part II discusses stamping materials and equipment; Part III focuses on dies and cutting and Part IV offers more detail about cutting processes. The final installment, Part V, investigates forming methods.

To remain employed in today's economy, you must be diversified with respect to your skills. With cutbacks, companies now have fewer resources to get the work done

How Stamping Affects Our Lives

There is no doubt that stamping has dramatically changed our lives. Common household items such as washers and dryers are made using a sheet metal stamping process. Items that we often take for granted, such as the flatware we use for eating, the pots and pans we cook with, and the car we drive, are manufactured partially by sheet metal stamping. Beverage cans, cigarette lighters, gun shells, even certain types of solid gold jewelry are manufactured using this process. The computer on which you are reading this article contains stamped parts.

How Stamping Is Viewed

It's very interesting to me how the perception of sheet metal stamping and die makers varies from person to person. Some people think of stamping as a typically dirty "factory-type job," while others think die makers are highly skilled individuals who are good with their hands. The truth is, die designing and -making, troubleshooting, and maintenance are professional career paths. Many of the hands-on skills needed in the past have been replaced with new processes, such as wire burning and CNC.

In any case, as stampers, we must be masters of the trade and accept nothing less than perfection. Keep in mind that perfection in the tool and die industry means that everything important must fit and function properly. Fit and function is the key. Some die components must be manufactured with extreme dimensional accuracy, while others do not require as much accuracy. The key is to take the time to make precision components dimensionally correct, and don't waste time on less critical items.

Beauty Goes Only So Far

As a consultant, I find it somewhat frustrating to see a die that looks as good as jewelry when only parts of it need to be so. Although the toolmaker may be proud of the appearance of the tool, spending time polishing things in the die that don't need to be polished is wasteful. Companies typically don't purchase dies based on their physical appearance but rather their performance. Take pride in the performance of the tool, not its appearance.

Science—Not Art

Pursuing a career as a tool- and diemaker or designer can prove to be a great choice for many individuals. First let's dismiss some of the vicious rumors about the die building and stamping trade. Despite what some toolmakers may tell you, the occupation is not an art form. It is a science and a professional career path. Good diemakers and designers don't make decisions based on an inspiration they had earlier that day. Their intent is not to build something that is intended to "inspire" emotion.

Don't confuse creativity with art. Toolmakers and designers must be very creative in their thought process. Unlike an artist, who intends to inspire emotion, a die designer must create something that functions correctly.

To be a good diemaker or designer, every decision that you make with respect to the die must be based on a good understanding of physics. It's very simple: If you throw an apple in the air, it will fall. It doesn't matter how artistic you are.

A career as a tool- and diemaker is not only very challenging, but also requires a great deal of education. Some of that education is in an academic form, while the bulk of your learning will come with actual shop floor experience. Although you may not end up with a degree from the University of X, rest assured, this is a professional career path. I work with many academic professionals, some with Ph.D.s, who consult with me on projects. It is only through the combined efforts of academic and real-world experience that we can realize success.

As a diemaker or designer, you could be responsible for making decisions that end up costing thousands and sometimes millions of dollars. Judgments should not be taken lightly; a poor decision can devastate an organization. A baker can eat his mistakes, but a bad die can't even be used as a boat anchor. More the reason to strive for perfection.

Why Sheet Metal Stamping?

The System. You've heard the phrase "necessity is the mother of invention," which can be summarized in one word: need. Large companies, such as automotive, aircraft, or appliance manufacturers, often drive the need for sheet metal tooling. These companies are called original equipment manufacturers (OEMs).

If an OEM sees a need for a part or a new product line, it will go about determining the best way to produce it. This is where a great deal of knowledge about the many different processes is important. For example, if a large-volume part can be stamped as opposed to casting, the part can be produced at a significantly lower cost.

Some OEMs have the capacity to build the tooling and run the dies themselves; however, they often outsource their part production needs. This means they may hire a company to provide the parts to fill their need. These outside companies that work directly with the OEMs are called Tier 1 suppliers.

In the sheet metal stamping business, a Tier 1 supplier generally owns several stamping presses and hopes to get a contract to supply parts to an OEM. But the OEM doesn't just give supplier contracts away. The Tier 1 supplier has to bid on the contract. Once the company has landed a contract to supply parts, it must build the stamping die that runs in its presses to create the parts. The company may have a division that builds dies, but many must find a tooling source to supply the die, which in turn must bid on the contract to build it.

What Is a Sheet Metal Stamping Operation? A sheet metal stamping operation is one in which sheet metal is cut and formed into a desired shape or profile. Although a sheet metal stamping process may utilize numerous types of special machines, three basic items are essential: the sheet metal from which the part is to be made; the stamping press; and the stamping die.

With the exception of a specialized sheet metal stamping process commonly referred to as hot stamping, most sheet metal stamping operations involve cold forming. This essentially means that no heat is intentionally introduced into the die or the sheet material. However, keep in mind that although stamping is a cold-forming process, heat is generated. Cutting or forming sheet metal creates friction between the die and the metal—much like the friction and heat that occur when you rub your hands together.

Because heat is generated from friction during the cutting and forming process, stamped parts often are very hot when they exit the dies.

What Are Some of the Different Professions Associated With Sheet Metal Stamping? You can pursue many stamping-related careers, such as process engineer, die designer, machinist, diemaker, or die maintenance technician.

A process engineer is responsible for determining the steps needed to turn a flat sheet of metal into a finished part—a critical task and an important position. A single process error can quickly spell failure.

Die designers are responsible for designing the tools to effectively execute the process that has been established. Many individuals serve as both process engineers and die designers. Effective die designers have a good understanding of mechanical motion, as well as material strengths and tool steel types. They are skilled at operating CAD or computer-aided software.

Machinists are responsible for cutting die components from specified materials to their proper dimensions.

Diemakers assemble and construct the tool. They also must test the die to make sure it functions properly and consistently produces an acceptable piece part.

Production die maintenance technicians maintain, repair, and troubleshoot stamping dies.

Figure 1: A stamped bright finish stainless steel sink

Editor's Note: In this series, tool-and-die expert Art Hedrick presents an overview of metal stamping. Part I focused on the various careers in the metal stamping industry. Part II discusses stamping materials and equipment; Part III focuses on dies and cutting and Part IV offers more detail about cutting processes. The final installment, Part V, investigates forming methods.Now that you know who does what, it's time to discuss the materials and equipment used in stamping.

Why Sheet Metal?

First let's begin with the basics. Sheet metal is one of the strongest materials that can be readily shaped and cut. Because of its strength, it is an ideal candidate for making parts that require good load-bearing ability. Also, many metals have good corrosion resistance, as well as good electrical conductivity. This makes metal a good candidate for electrical components.

Sheet metal is recyclable, so it can be reused indefinitely. Items made from sheet metal can be aesthetically pleasing (Figure 1), which makes the material a great candidate for products that require both good visual appearance and strength.

Sheet Metal Basics

Sheet and coil material is produced by progressively squeezing a red-hot, large, rectangular block of metal between rollers. This metal-squeezing process commonly is referred to as the rolling process. Each time the metal is rolled, it gets thinner and thinner. The space between the final set of rollers determines the final metal thickness.

After the desired thickness is obtained, the sheet metal then is rolled into a large coil. Typical sheet metal thicknesses used in stamping are 0.001 in. to 0.625 in. Although most stamping operations use sheet steel, special dies can cut and form steel bars up to 3 in. thick.

Many different types of metal can be cut and formed in a die. Everything from gold to special superalloys used in the aerospace industry can be stamped. However, of all the materials stamped today, steel is the most common. Hundreds of steel types—from mild to special grades of advanced high-strength steel—are available for stamping.

Stainless steel is used in many stamping applications. Certain grades of stainless steel, such as the types that are used to make kitchen sinks, offer great formability, while others offer great corrosion and heat resistance. Some stainless steels can be hardened after they are stamped. These types often are used to make surgical tools and high-quality knives.

The metal selected for a stamping application must be the type and thickness that can be cut and formed into a part that fits and functions properly. Before a process can be established or a die to perform it can be made, you must have a good understanding of the material's mechanical properties. Specific critical properties will be discussed in greater detail in a later article. Knowing them helps you determine if the metal can be formed or cut in a die; how many operations are required; which tool steel type is needed; the press capacity; and other die design parameters. Attempting to develop a process without understanding the material you are cutting and forming is very risky and can result in catastrophic failure.

What Is a Press?

It takes a great deal of force and energy to cut and form sheet metal. For example, to cut a 10-in.-diameter circle out of a sheet of 0.125-in.-thick mild steel, it takes approximately 157,000 lbs. of pressure. To help put this in perspective, you would have to stack approximately 13 elephants on top of a cutting punch for it to penetrate through the sheet metal.

A press is a special machine that supplies the necessary force to form and cut the sheet metal. Consider this: One ton equals 2,000 lbs. Achieving a force equal to 157,000 lbs. requires a press with a minimum force of 78.5 tons. By today's standards, this is a very small, low-tonnage press. Presses range in tonnage from 10 to 50,000; 50,000 tons equal 100 million lbs. Press safety procedures are critical. Even the smallest press will not stop for an arm or a finger.

The numerous presses in use today can be grouped into three basic types: crank-drive, hydraulic-drive, and servo-drive. Many variations exist

.

Figure 4: Stamping presses

Some presses can run at speeds in excess of 1,500 strokes per minute. These commonly are referred to as high-speed presses. Other presses may cycle very slowly and produce fewer parts in a given amount of time. The speed at which a press cycles is based on many factors, including the sheet metal type, the shape and size of the part, the type of die that is used, as well as the type of automated equipment used in the stamping process.

All presses utilize a moving component or portion of the press called the ram. One half of the die is attached to the ram, while the other half is attached to a stationary part of the press called the bolster plate (Figure 4). The distance that the ram travels in one direction is referred to as the stroke of the press. Presses have stroke lengths from 0.250 in. to 40 in. depending on the intended application.

To accommodate a large variety of die thicknesses, the press's shut height must be adjustable. The shut height can be defined as the distance from the bottom surface of the ram to the top surface of the bolster plate when the press ram is at its lowest point. We call this ram position bottom dead center.

Don't confuse the stroke length of the press with its shut height. With the exceptions of hydraulic and servo presses, the stroke length is a constant distance, while the shut height can be altered.

High-speed presses typically have short stroke lengths and, therefore, very little shut height adjustability. Using a press with an excessive stroke length can result in lower part output. This is because the ram travels an excessive distance before the die is actually performing work.

As mentioned earlier, hydraulic- and servo-drive presses are the exceptions to these basic rules. These presses have both adjustable shut heights and stroke lengths and are good candidates for a variety of stamping operations.

Great care must be taken when selecting a press. Variables such as tonnage, stroke length, bed size, deflection rates, ram speeds, drive types, and shut height adjustability are very important. However, one of the key things to remember is that the press is a very crucial part of the metal stamping process. The wrong type or a poorly maintained press may result in failure regardless of the die quality. When I am conducting a public seminar, I tell my attendees, "You can have a jewel of a die, but if you put it in a glorified 200-ton trash compactor, you will make trash." Don't dismiss the importance of the press.

What Is a Die?

A stamping die is a special, one-of-a-kind precision tool that cuts and forms sheet metal into a desired shape or profile. Dies often are referred to simply as tooling.

Usually only one die is made to stamp out a certain part shape or type. The exception to this rule is when the volume of parts is so high that a stamper needs to run a die continually to meet the quantity requirements. In this case, it may be necessary to create two identical dies. When one die is in need of repair or maintenance, the other die can take its place.

Often dies are designed with inserts to produce many variations on a single part, such as adding or removing holes or achieving slight form changes.

A die basically consists of two halves: a punch and a cavity (Figure 1). Both the punch and cavity components typically are attached to precision guided metal plates call die shoes. The shoes assembled with the die is referred to as a die set. The die set is the foundation on which all of the working die components will be mounted. Die sets can be made from steel or high-strength aluminum (Figure 2).

Although many commercially available components are used in manufacturing dies, most of the die's cutting and forming sections usually are made from special types of hardenable steel called tool steel. Areas of the die that are not intended to cut or form the metal most often are made from low-cost mild steel. Dies also can contain cutting and forming sections made from solid carbide or various other hard, wear-resistant materials. These components will be discussed in greater detail later in this series.

Die Size

Dies range in size from those used to make microelectronics, which can fit in the palm of your hand, to those 20 ft. square and 6 ft. thick that are used to make entire automobile body sides.

Not all dies are used to form sheet metal. Some dies can cut and form plastic, paper, rubber, and other materials. You probably have seen embossed letterhead or raised impressions on a brochure or marketing piece. These are made with embossing dies. You may have seen pennies smashed into souvenir coins from attractions, such as Walt Disney World, which often contain raised images. These trinkets are made using coining dies. Even the coins in your pocket are made using dies.

The part a stamping operation produces is called a piece part. Certain high-speed dies can make more than one piece part per cycle and can cycle as fast as 1,500 cycles (strokes) per minute.

All stamping dies perform one of two basic operations: cutting or forming. Many dies can handle both operations.

Figure 2: Image courtesy of: ITW DRAWFORM

Metal Cutting Basics

Cutting is perhaps the most common operation performed in a stamping die. During cutting, the metal is severed by placing it between two bypassing tool steel sections that have a small gap between them. This gap, or distance, is called the cutting clearance. The process of metal cutting not only takes a great deal of force, but it also produces a great deal of shock. For this reason, metal cutting is one of the most severe stamping operations. Excessive shock can cause die sections to break, punches to snap, and presses to fail.

Imagine this scenario.If you had a hammer in your hand and I instructed you to set it on a nail and push it into a piece of wood, you most likely wouldn't have a great deal of success. However, if I told you to lift the hammer and strike the nail, it would go into the wood with very little effort. The energy of the hammer falling combined with the shock performed the necessary work.

If you have ever been in a stamping plant that is cutting thick, high-strength steel, you literally can feel the floor shake every time the press cycles. Presses intended for cutting heavy or high-strength materials usually are designed with extra-heavy-duty frames and components that can withstand this tremendous shock. Certain presses even have special dampening units installed to help dissipate and absorb the shock.

What Happens During Metal Cutting?

First, understand that you sometimes must shift your paradigm or thought pattern with respect to sheet metal. Despite its physical appearance, density, strength, and weight, sheet metal is an elastomer, which essentially means that when it is subjected to a great deal of force, it behaves much like rubbery plastic. Some metals are far more rubbery than others.

To cut metal, the die must first have a cutting punch and a mating section into which the punch enters. The cutting clearance, the distance between the cutting sections, varies with respect to the metal type, thickness, hardness, and desired edge quality.

The cutting clearance often is expressed as a percentage of the metal's thickness. Although clearances can vary from zero to as much as 25 percent of the metal thickness, the most common cutting clearance used is about 10 percent. For example if you were to design a die to cut metal that is 0.050 in. thick, the distance between the upper and lower cutting sections would be 0.005 in.

Excessive or insufficient clearance between cutting sections can produce an excessive burr on the part (Figure 3). To minimize the burr height, the cutting sections not only must have the proper cutting clearance between them, they must be ground periodically to maintain a perfectly square edge. Diemakers and technicians refer to this process of grinding die sections simply as sharpening the section. Grinding are normal tasks in a basic maintenance procedure.