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Home > Lessons > Lesson 10: Synthesis, Fabrication, and Processing of Materials

Lesson 10: Synthesis, Fabrication, and Processing of Materials

Overview

As materials are formed or processed into useful products the materials undergo changes in their materials properties. These changes can be beneficial or deleterious. Understanding these changes can enhance the performance of the material or, in some cases, prevent unanticipated materials failure. In this lesson, we discuss the common formation and processing methods for metals, ceramics, and polymers, and how these processes can effect the materials properties of the processed materials.

Learning Objectives

By the end of this lesson, you should be able to:

  • Name and describe four forming operations that are used to shape metal alloys.
  • Name and describe five casting techniques.
  • Name and briefly describe five forming methods that are used to fabricate glass pieces.
  • Briefly describe and explain the procedure by which glass pieces are thermally tempered.
  • Briefly describe processes that occur during the drying and firing of clay-based ceramic ware.
  • Briefly describe/diagram the sintering process of powder particle aggregates.
  • Briefly describe addition and condensation polymerization mechanisms.
  • Name the five types of polymer additives and, for each, indicate how it modifies polymer properties.
  • Name and briefly describe five fabrication techniques used for plastic polymers.

Lesson Roadmap

Lesson 10 will take us one week to complete. Please refer to the Syllabus or course calendar for specific due dates.

Lesson Roadmap
To Read Read pp 283-322 (Ch. 14) in Introduction to Materials ebook
To Watch Raw to Ready: Bombardier
To Do Lesson 10 Quiz

Questions?

If you have general questions about the course content or structure, please post them to the General Questions and Discussion forum in Canvas. If your question is of a more personal nature, feel free to send a message to all faculty and TAs through Canvas email. We will check daily to respond.

Reading Assignment 1

Things to consider...

As you do the following reading consider the following questions. Remember to keep the learning objectives listed on the overview page in mind as you learn from this reading.

  • What are the four forming operations that are used to shape metal alloys?
  • What are the five casting techniques?

Reading Assignment

Read pp 283-293 (Ch. 14) in Introduction to Materials ebook

Metal Forming Operations

Now that you have completed the reading assignment regarding the fabrication of metals, let us summarize some of the important points.

To Watch

One way to classify the fabrication of metals is into the categories of (mechanical) forming, casting, and miscellaneous methods. There are four types of forming processes: forging, rolling, extruding, and drawing. I like to refer to these as pounding, rolling, pushing, and pulling. Hopefully, by the end of this section, you will understand why I use those terms.

Blacksmiths have been hammering (pounding) metals into shape for some time. Today, we have large machines which pound and stamp metals into shape. Please watch this very brief (00:33) video on metal forging which shows exactly that: Forging [1]. (If that video is currently unavailable, check out this Forging video [2] instead.)

Putting metal between rollers is an effective way to create thin sheets, here is a very brief (1:23) video which shows how rolling is done: Roll Forming [3]. (If that video is currently unavailable, check out this Roll Forming video [4] instead.)

In extruding, metal is PUSHED through dies which controls the final profile of the metal piece. Please watch this brief (1:56) video on metal extruding: Extrusion [5]. (If that video is currently unavailable, check out this Extrusion video [6] instead.)

For the last process, drawing, please proceed to the next section.

How are Aluminum Cans Made?

The last of the four mechanical forming processes, drawing, is one of the processes discussed in the following video (4:45) on How are Aluminum Cans Made? While you are watching this video, please think back, way back, to Lesson 1 of this course and the reading in the textbook about different materials used for carbonated beverage containers. And remember to look for the drawing operation (hint: it is the operation that gives the can its height).

To Watch

How are Aluminum Cans Made?
Click for the transcript of How it's made - Aluminum cans.

The next time you buy a can of soft drink consider this: the aluminum tin can will always be recyclable. Unlike plastic, aluminum never deteriorates no matter how often it's melted down and used again. Aluminum cans are so lightweight, that it's hard to believe that they're made from a huge roll of our minyan sheeting that weighs nine tons. The sheet is about a meter and a half wide and a roll like this is long enough to make three-quarters of a million drink counts. The sheet feeds into a press that punches out round pieces that will be formed into counts. The punch press actually performs two operations it punches out a disc 14 centimeters in diameter then bends it into a cup. What's left of the sheet gets compacted and sent back to the aluminum factory where it's recycled into new rolls. The cup goes into a machine of the draw and iron body maker. A tool draws out the aluminum forming the body of the camp. The tool is lubricated, so it won't tear the aluminum while stretching it. The lubricant also acts as a coolant because the aluminum heats up as it's being worked. Once the body is formed a trimmer cleans and straightens the edges. Now the cans move along upside down on the conveyor belt over to the washer. The washer performs a six-stage cleaning. The first two washes are in hydrofluoric acid at 60 degrees Celsius. The last four washes are in deionized water neutral water with no pH also at 60 degrees. The cans come out of the washer and go under the hot air dryer. They're now shiny because the hydrofluoric acid wash removed a thin surface layer of aluminum.

Next, a roller passes over the cans coating the bottom rims with varnish. This coating allows the cans to slide easily on conveyor belts and in vending machines and shows up as a blue ring under an ultraviolet light. The cans are now ready to be printed this rotation printing system can apply up to five colors one at a time. Then a layer of varnish is applied to protect the ink. Even in slow motion, it's a high-speed operation, and here's the actual speed: 1800 cans per minute. Next, the cans fly through an oven that instantly hardens the ink and dries the protective varnish. Next, the Machine sprays a water-based varnish on the inside of the cans. This creates a barrier between the drink and the aluminum so the drink won't end up tasting like metal. It also prevents the aluminum from being eaten away from the inside by the acid in carbonated drinks. Next, the cans go through a machine called the Nekor which forms a 5-centimeter neck on the can. This is done gradually in 11 steps so as not to puncture the paper thin aluminum.

The next machine called the flanger forms a curved over the edge at the top of the camp which will later attach to the pull tab cover. The cans pass through a sophisticated vision system that photographs the inside of each can any can that doesn't meet standards, that has a bump or some ink inside is sent back for recycling. From here, they're shipped to the drinks company which fills them and then attaches the pull tab cover. So, now you know. You can start the whole process off by recycling your cans.

Credit: How It's Made

Now that we have reviewed the four mechanical forming processes for metals: forging, rolling, extruding, and drawing, hopefully, you also understand why I refer to them as pounding, rolling, pushing, and pulling. In the next section, we will look at how metals that cannot be mechanically formed are typically formed.

Casting

Not all metals are amenable to the mechanical deformation which occurs with mechanical forming processes discussed in the previous sections. Those metals that can undergo mechanical forming are referred to as wrought metals. For those metals that are not amenable to mechanical deformation, they are typically cast.

Casting is the process in which molten metal is poured (or cast) into molds. In the reading, you were introduced to five different casting techniques: sand, die, investment, lost foam, and continuous. Typically, it is more economical to use mechanical forming processes, since it requires more energy to heat metals until molten in the casting process. However, there are times when casting makes more sense, in addition to the obvious case of a metal not being amenable to mechanical deformation. Some of those cases include when making complicated shapes or when prototyping a part. When prototyping, the cost of making a forging die might be much more expensive than the cost of molds.

To Watch

Please watch the following video (02:54) on Metal Casting [7]. (If this video is unavailable please watch this Metal Casting [8] video.)

Now, please go to the second reading (2 of 3) of this lesson and read about how ceramics are fabricated.

Reading Assignment 2

Things to consider...

While doing the next reading, use the following questions to guide your reading. Remember to keep the learning objectives listed on the overview page of this lesson in mind as you learn from this text.

  • What are five forming methods that are used to fabricate glass pieces?
  • How are glass pieces thermally tempered?
  • What are the processes that occur during the drying and firing of clay-based ceramic ware?
  • What is the sintering process of powder particle aggregates?

Reading Assignment

Read pp 294-308 (Ch. 14) in Introduction to Materials ebook

Ceramic Fabrication Methods

The fabrication methods of ceramics are classified in three categories: glass-forming, particulate forming, and cementation. In glass-forming processes, the raw materials are heated until they melt. There are five glass-forming processes: blowing, pressing, drawing, fiber-forming, and sheet-forming. The following five-minute video highlights automated glass blowing for the production of glass bottles. Again, while you are watching this video, please think back to Lesson 1 of this course and the reading in the textbook that covered different materials used for carbonated beverage containers.

To Watch

How Glass Bottles are Made
Click for transcript of How It's Made - Glass Bottles.

Whether they're colored or clear, glass bottles and jars are green. No trees die to make this eco-friendly packaging. Glass is made of natural ingredients that are abundant. You can recycle glass endlessly, and making it uses less energy than producing metal or plastic.

The recipe for glass combines about a half a dozen natural raw materials, but the main ones are silica sand, soda ash, and limestone. Silica sand usually makes up about forty-five percent of the batch. The soda ash helps melt the silica evenly. It comprises about fifteen percent. A limestone content of about ten percent makes the finished glass more durable. They combine these ingredients with recycled glass called cullet. The factory's equipment feeds precise amounts of the materials into a furnace. Over a full day, the fiery heat two thousand seven hundred and thirty degrees Fahrenheit melts everything together producing a gooey liquid that's the consistency of honey. The molten glass pours out of the furnace. Shears cut the flow at precise intervals to produce cylindrical gobs. Each gob is the exact amount required to make one bottle or jar they dropped to a device called the scoop the scoop moves them two troughs that feed them to jar forming and bottle forming machines.

A gob of molten glass goes into a preliminary mold. In a matter of seconds, it comes out as what's called a parison a miniature version of the final bottle. Each parison and then moves into a blow mold the cavity of which is the shape of the final bottle. The equipment blows the compressed air into the parison stretching the glass outward toward the wall of the mold cavity. This process creates the final bottle shape and hollows out the inside. These are amber colored beer bottles. The color is produced by adding small amounts of iron-sulfur and carbon to the glass mix.

The factory uses a similar manufacturing process to produce other types of bottles and jars and this run the company is making 375-milliliter wine bottles out of clear glass. This run is producing 375-milliliter liquor bottles also out of clear glass, but this mold has a special feature a recessed insignia on one of the walls which produces a raised insignia on the front of the bottle.

After the bottles leave the forming machine they travel through flames. Otherwise, they would cool down too quickly and crack from thermal shock. A loader now gently pushes the bottles into what's called an annealing lehr. The bottles cool a controlled rate as they move through the lehr. This releases stress from the glass gradually. As the bottles exit the annealing lehr, a sprayer coats their exteriors with lubricant. This enables them to move smoothly through the rest of the inspection and packaging line. The bottles now line up in single file to head into the automatic inspection station. As the machine spins each bottle, cameras and probes check for imperfections such as cracks or bubbles. The inspection equipment that examines the top to check dimensions and ensure the threads for the screw cap are molded correctly. Before shipping, a worker does a final visual inspection. The proportion of cullet in glass can be as high as 90 percent. Cullet melts at a lower temperature, so for every ten percent of cullet in the mix the factory uses up to two and a half percent less energy to produce this glass. Now that's an incentive to recycle.

Credit: How It's Made

In the next section, we will discuss the important subject of heat treating glass to control stress.

Heat Treating Glass

When fabricating glass, it is usually vitally important to control the cooling of the fabricated pieces. Due to the brittle nature of ceramics, failure to remove internal stress in the glass either introduced during fabrication or due to uneven cooling will likely result in catastrophic structural failure of the piece. There are two basic types of heat treatments applied to glasses. In annealing, cooling is controlled in an effort to remove (or minimize) the internal stress in the glass. This is in contrast with tempering. In tempering, compressive stress is intentionally introduced into the surface of the piece as shown in the figure below. This compressive stress can prevent surface scratches and cracks from growing, which would likely fracture the glass.

see long description below.
Tempering: Compressive stress is intentionally introduced into the surface of the piece.
Click for a text description of image.
Compressive stress process: Before cooling the surface is very hot but once initial cooling begins the outside of the surface is cooler than the inner core. Once the material reaches room temperature there is compression on the outside surfaces and tension on the inner core. As a result surface crack growth is suppressed.
Credit: Callister

In the next section, we will discuss sintering, which is very important for particulate forming of ceramics.

Sintering

During powder press processes for the formation of ceramics, heat and pressure are used to densify and bind ceramics together as illustrated in the figure below in a process called sintering. Unlike melting, during sintering, materials are not liquefied, but instead, rely on reducing surface area effects between particles to drive the process. Ceramic materials usually have a very high melting temperature, so sintering (which is done at temperatures well below bulk melting temperatures) offers significant savings in terms of energy.

4 circles form a square. Then circles smoosh together. Pore in middle. Grain boundary where they touch, Neck at divets between circles
During powder press processes, heat and pressure are used to densify and bind ceramics together.
Credit: Callister & Rethwisch 5e

Now, please go to the third reading (3 of 3) of this lesson and read about how plastics are fabricated.

Reading Assignment 3

Things to consider...

While you do the following reading let the following questions guide your reading. Remember to keep the learning objectives listed on the overview page for this lesson in mind as you learn from this text.

  • What are the addition and condensation polymerization mechanisms?
  • What are the five types of polymer additives and, how do they modify polymer properties?
  • What are the five fabrication techniques used for plastic polymers?

Reading Assignment

Read pp 308-322 (Ch. 14) in Introduction to Materials ebook

Polymer Formation

As we discussed in the polymer lesson, there are two types of polymerization: addition (or chain) polymerization and condensation (or step) polymerization. In addition polymerization, a free radical attaches to a monomer. This results in an unsatisfied bond on the monomer, which is free to attach to another monomer. This process repeats over and over again building a polymer chain. In condensation, two chemical groups react together. Typically, one of the groups has an exposed hydrogen, while the other has an exposed oxygen-hydrogen. When the two compounds join, a monomer is formed with an exposed oxygen-hydrogen or hydrogen and releases a water molecule, H2O.

Polymers are synthesis by polymerization and the polymer properties are modified by the usage of additives. These additives are used to improve mechanical properties, processability, durability, etc. The five additive types discussed in the e-book are fillers, plasticizers, stabilizers, colorants, and flame retardants. Fillers are added to improve tensile strength, abrasive resistance, and toughness, as well as to reduce cost. Plasticizers are added to transform brittle polymers to ductile ones. Stabilizers are added to protect from degradation due to exposure to ultraviolet light. Colorants are added to provide color to the polymer. Flame retardants are added to eliminate or reduce the flammability of polymers.

Fabrication of plastic polymers can utilize one of several molding techniques: blowing, compression, injection, and transfer, or by extrusion or casting. Fibers can be spun or drawn. Films can be formed by extruding, blowing, or calendaring. The following video [9] (4:50) highlights blow molding for the production of plastic bottles. Again, while you are watching this video, please think back to Lesson 1 of this course and the reading in the textbook about different materials used for carbonated beverage containers.

To Watch

How Plastic Bottles are Made
Click for the transcript

Whether you're buying apple juice or peanut butter, you've probably noticed that fewer products come in glass containers these days. Plastic packaging is becoming more common. Plastic bottles and jars are lighter to carry and leave no shards of glass to clean up if you drop your grocery bag. Many transparent bottles and jars are made from a type of plastic called polyethylene terephthalate or PET. An automated mixer combines PET pellets with flakes of recycled PET. Reprocessed plastic loses some of its physical properties, so the recycled content cannot exceed ten percent. The PET drops from the mixture into a plastic injection machine that heats it to a piping 600 degrees Fahrenheit. The dry raw material melts into thick and gooey liquid plastic. The machine then shoots it at high pressure into a mold. This plastic injection molding process casts pieces of plastic called preforms. Starter shapes and subsequent machines will transform into bottles or jars. The molded preforms harden almost instantly thanks to a built-in cooling system. These preforms are now on their way to becoming single serving juice bottles.

This is another plastic injection molding machine. It uses the same method to make preforms for a different model: one-and-a-half to two-liter bottles. The preforms next stop is a machine called a reheat stretch blow molder. In a matter of seconds, it heats each preform just enough to make the plastic malleable, then inserts a rod to stretch the preform lengthwise while at the same time blowing in air at extremely high pressure. This forces the preform into a bottle shaped bowl. Cold water circulates within the mold to cool and set the plastic almost instantly. This lightning fast machine turns out ten thousand six hundred bottles per hour. No wonder we've had to show it to you in slow motion. A conveyor belt transports the finished bottles to the packaging area. Before blow molding, the preforms for certain models first pass through an oven.

Credit: How's it Made

You have now finished the reading for Lesson 10. Please proceed to the next page and watch the video for Lesson 10.

Video Assignment: Raw to Ready: Bombardier

Now that you have read the text and thought about the questions I posed, go to Canvas and watch this 53-minute video about how glass, titanium, fiberglass, lacquer, and aluminum alloy become a jet. In "Raw to Ready: Bombardier," we see how various components are painstakingly fabricated beginning with the raw materials to the final assembly into the regional jet aircraft.

Video Assignment

Go to Lesson 10 in Canvas and watch the Raw to Ready: Bombardier video. You will be quizzed on the content of this video.

Summary and Final Tasks

Summary

Materials are formed or manufactured into components that are incorporated into useful products. During these processes, the properties of the materials can be enhanced or adversely affected. Knowledge of these effects and the economic costs are many times needed to successfully bring a product to market. In this lesson, we looked at the most widely used fabrication and synthesis techniques for metals, ceramics, and polymers, as well as, discussed how these processes impact materials properties.

Reminder - Complete all of the Lesson 10 tasks!

You have reached the end of Lesson 10! Double-check the to-do list on the Overview page to make sure you have completed all of the activities listed there before you begin Lesson 11.


Source URL:https://www.e-education.psu.edu/matse81/node/2180

Links
[1] http://pennstate.kanopystreaming.com/playlist/455671 [2] https://www.ellwoodcityforge.com/forging-education [3] http://pennstate.kanopystreaming.com.ezaccess.libraries.psu.edu/playlist/455743 [4] https://www.youtube.com/watch?v=k6iODHla6qY [5] http://pennstate.kanopystreaming.com/playlist/458304 [6] https://www.youtube.com/watch?v=Y75IQksBb0M [7] http://pennstate.kanopystreaming.com/playlist/458316 [8] https://www.youtube.com/watch?v=R1dntfivkgg&t=25s [9] http://www.youtube.com/embed/8QkxpQT967w