Fundamentals of Technology
VoCATS – Section 4
Communicate the design processes
Competency Four
Communicate the design processes
Objective 4.01
Explain terms and procedures involving measurement tools.
The following outline characterizes Objective 4.01
Explain measurement terms
Explain measurement tools
List measurement prefixes (see appendix)
Explain the customary and metric systems of measurement (see appendix)
Explain measurement conversions and calculations (see appendix)
“Technological knowledge and processes are communicated using symbols, measurement, conventions, icons,graphic images, and languages that incorporate a variety of visual, auditory and tactile stimuli.”
Measurement is the process of determining the size, amount or extent of something. It objectivelydescribes the physical qualities of an object. It is also the practice of comparing qualities of an objectto a standard.
There are two measurement systems used in the world today, the U.S.Customary System and theMetric System (System International, SI).
The United States is the only industrialized country thathas not adopted the metric system for everyday use.
The U.S. Customary system uses unique units for each quality being measured. The lack of uniformmultiples can make the system confusing. It is based on units of measurement established during theMiddle Ages in Europe. The basic units of measure for length is the inch; for weight, the pound; forvolume, the quart; and for temperature, degrees Fahrenheit.
The Metric system was established in France. The basic unit of measure for length is the meter; forweight, gram; for volume, the liter; and for temperature, degrees Celsius.
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Metric Prefixes – The metric system is based on ten. “There is a logical progression from smallerunits to larger ones, since all sizes of units are based on ten.”(p. 119, R3) The metric system starts witha base unit. Smaller units are decimal fractions of the base unit. Larger units are multiples of ten. Themetric system uses a prefix to show us how the base unit has been changed. For example, the unit fordistance is the meter. For large distances, the kilometer is used. The prefix kilo means 1000, so sevenkilometers is equal to 7000 meters. For small distances, the millimeter is used. The prefix milli means1/1000th. Twelve millimeters are 12/1000 of a meter. The metric system lends itself to easy use inmathematical formulas. The metric system uses the same prefixes for all base units.
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Measurement Tools
Before a technician can measure anything using the customary or metric systems, they must first be able toexplain how to use the appropriate measuring tools. Some measuring tools commonly used by technicians intheir work include: rules, calipers, micrometers, squares, protractors, various gauges, weight scales, andcalibrated containers.
Rules are used to measure length, width and thickness. Some rules used include:standard 12 inch rule, mechanical rule, drafter’s rule, machinist’s rule, metric rule, yardstick, meter stick, and tape measure. Rules are calibrated in many different ways.
Technicians must be able to interpret calibrations when usingrules.
Calipers are used to measure diameters on either the inside oroutside of an object. The two types of calipers are the outsidecaliper and the inside caliper. Calipers may need to be used inconjunction with a rule to determine the value of a measurement. Many calipers areadjusted by turning it’s thumb screw until the legs fit snugly against the surface beingmeasured. The distance between the legs is then measured with a rule.
Micrometers are very precise tools for measuring the length, thickness or diameter of small objects. Amicrometer that uses customary units can measure to one thousandths (0.001) of an inch. A metric micrometercan measure to one hundredth (0.01) of a millimeter.
Squares are used to measure or lay out perpendicular lines (lines at 90 degreeangles). Four commonly used squares are the try square, framing square,combination square, and center square. A combination square can also measure45 degree angles.
Protractors are used to measure angles from 0 to 180 degrees for protractors that are half-moon shaped and 0to 360 degrees for circular shaped protractors. Many protractors can also be used to measure length along theirstraight edge.
Weight scales measure weight or mass. Scales can range from the common bathroomscale to the most sensitive scientific scale. Scales can be analog or digital, manual orelectronic. As you see, there are many factors to consider when selecting a scale.
Calibrated containers are used to measure volume. Cooks use calibrated containers tomeasure ingredients for recipes. Scientists use calibrated containers in the science lab.
Measuring spoons, measuring cups, and lab beakers are three types of calibrated containers
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Objective 4.02
Students will apply measuring techniques.
The measurement of part and product size is important in technological design and production activities.
Generally this type of measurement can be divided into two levels of accuracy, Standard Measurement andPrecision measurement
Standard Measurement
Many production settings do not require close measurements. The length of a house, the width of a playingfield need not be very accurate. If the product is within a fraction of an inch it will work fine. Thesemeasurements are often given to the foot, inch or fraction of an inch in the customary system, or the nearestwhole millimeter in the metric system.
The material being measured is also important. For example, wood changes (expands or shrinks) in size withchanges in moisture content and the atmospheric humidity. Measurements closer than 1/32 in. or 1mm are notuseful. Wood can change more than that in one day.
Standard measurements are common in cabinet and furniture manufacturing plants, construction industries, andprinting companies. The printing industry uses its own system based on the pica (1/6in.) and the point(1/72in.)
Precision Measurement
Standard measurement is not accurate enough for many production applications. Watch parts and enginepistons would be useless if they varied by as much a 1/32in. (0.8mm).
These parts must be manufactured to an accurate size. For this type of production, precision measurement isrequired. Measurements of 1/1000 in. to 1/10,000 in. are precise in the customary system. Metric precisionmeasurement will measure to within 0.01mm (one one-hundredth of a millimeter).
Direct Reading Measurement Tools
Three common uses of measurement are finding linear dimensions, diameters, andangles. Each of these three features can be measured using standard precisiondevices.
Linear Measurement
The most common linear measurement device is the rule. The most commondivisions are sixteenths (1/16 in.) Metric rules are divided in whole millimeters.
The part is measured with a rule by aligning one end of the part with the end of the rule or with an inch mark.
The linear measurement is taken by reading the rule division at the other end of the part.
Flexible rules are often called tape rules. They are used in woodworking and carpentry applications. There isa hook at one end of the rule that is hooked to the end of the board or structure. The tape is pulled out until itreaches the other end of the board or structure. A measurement is then taken.
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Measuring Diameters
A common measurement task involves determining the diameter of round material or parts. Precise diameterscan be measured by placing a part between the anvil and the spindle of a micrometer and reading themeasurement on the barrel.
Measuring Angles
The angle between two adjacent surfaces is important in many situations. The legs of a desk are generallysquare (at a 90angle) with the top. Squares are used to mark angles. The head is placed against one surface of the material. The blade is allowed to rest on an adjacent surface. If the blade touches the surface over its entirelength, the part is square (R3, 124-125).
Indirect Reading Measurement Tools
In many modern measuring systems, humans no longer take measurements. Sensors gather the measurementdata, which is processed by computers or other automatic devices. The final measurement can be displayed onan output device such as a digital read-out, computer screen, or printout. These new systems include lasermeasuring devices, optical comparators, and direct reading thermometers.
You may measure length, weight, temperature, or other qualities. However, there must be a reason for doingthe measuring. All technological processes produce products or services.
These may be goods, buildings, or communication media.
Measurement is necessary in designing most anything. Its size, shape, or otherproperties are communicated through measurements. Processing equipment is set up and operated using thesedesign measurements. Materials needed to construct the item are ordered using measurement systems. Allpersonal or industrial production is based on measurement systems.
Measurement can also be used to compare the present condition with a desired condition. The process ofsetting standards, measuring features, comparing them to standards, and making corrective actions is calledquality control. The foundation of a quality control system is measurement and analysis.
Measurement describes distance, mass, time, temperature, number of particles, electrical current, and lightintensity. It involves comparing a physical characteristic to an established standard. The common standards arethe metric system and the U.S. customary system. These systems allow people to communicate designs, ordermaterials, set up machines, fabricate products, and control quality.
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Objective 4.03
Explain terms and procedures utilized in technical sketching
The following outline characterizes Objective 4.03
Explain orthographic sketches and pictorial sketches
Explain rough, refined, and detail sketches
Explain types of lines used in sketching and drafting
DRAFTING: THE UNIVERSAL LANGUAGE
Drafting is the process of accurately representing three-dimensional objects and structures on a two-dimensionalsurface, usually paper. It is an accurate drawing process used for nearly every product or structuremade today – large or small.
Integrated circuits, shoes, tools, cars, bridges, and skyscrapers are just a few examples of things that aredrafted. Drawings are also used to communicate ideas effectively and accurately.
Sketching
Once the designer has conceived a number of ideas, the ideas must be recorded. The most common recordingmethod is to develop rough sketches of the products, structures, or system components. The term “rough” isnot used to describe the quality of the drawing. They often represent good sketching techniques. The termrough describes the state of the design ideas. It suggests that the designs are incomplete and unrefined.
Refining original designs is the second step in developing a design solution. Refined design ideas may also bedeveloped by merging ideas from two or more rough sketches into a refined sketch. The new idea may notlook anything like the original rough sketches. The rough sketch and refined sketch communicate shape andproportion. They do not communicate size. For this task, a third type of sketch is needed, called a detailedsketch. It communicates the information needed to build a model of the product or structure. Buildingrequires three major types of information: size information explains the overall dimensions of the object, or thesize of the features on an object; location information gives the position of the features within the object; andgeometry information describes the geometric shape or relationship of features on the object.
Developing Pictorial Sketches
Designers often use pictorial sketching techniques to capture and further refine product design ideas. Thesetechniques try to show the artifact much like the human eye would see it. Therefore, a single view is used toshow how the front, sides, and top would appear.
Three basic techniques are used to develop pictorial sketches:
Oblique sketches
Oblique sketches are the easiest pictorial sketches to produce. They show the front view as if a person waslooking directly at it. The sides and top extend back from the front view. They are shown with parallel linesthat are generally drawn at 45to the front view.
The two types of oblique drawings are cavalier and cabinet.
The cavalier oblique drawing causes the sides and top to look deeper than they are. To compensate for thisappearance cabinet oblique drawings are often used. This type of drawing shortens the lines that project backfrom the front to one-half their original length.
Isometric Sketches
Isometric sketches are the second type of pictorial drawings used to produce refined sketches. The wordisometric means equal measure. Isometric sketches get their name because the angles formed by the lines atthe upper right corner are equal – each is 120. The object is shown as if it were viewed from one corner.
Perspective Sketches
Perspective sketches show the object as the human eye or camera would see it. This realism is obtained byhaving parallel lines meet at a distant vantage point. Developing the perspective view is more difficult to drawthan oblique or isometric views. However, perspectives are the most realistic of the three sketches.
Types of Perspective Views
There are three major types of perspective views: one-point, two-point, and three-point. One-point perspectiveshows an object as if you were directly in front of it. A two-point perspective shows an object wouldappear if you stood at one corner. A three-point perspective shows how the eye sees the length, width, andheight of an object. All lines in this drawing extend toward a vanishing point. Changing the position of thehorizon line can cause the object to be seen as if the observer were looking down on the object(aerial view), directly at it (general view), or up at it (ground view).
Detail Drawings
Most detail drawings are prepared using the multi-view method. This drawing method places one or moreviews of the object in one drawing. The number of views will depend on how complex the part is. Generally,a top, right side, and front view are shown. Multi-view drawings use orthographic projection to projectinformation at right angles to new views. The surface with the most detail is chosen to be shown in the frontview. The front view is drawn in the lower left quadrant of the paper. Projection lines are extended to the topand right of the front view to form the top and side views (orthographic projection).
Drawing Lines
One set of drafting standards deals with lines and line weights. The shape of the object is of primaryimportance. The lines that outline the object and its major details must stand out. These solid lines are calledobject lines and are the darkest on all drawings. Some details are hidden in one or more views. Therefore,they are shown but with lighter, dashed lines called hidden lines. A third type of line locates holes and arcs ona part. These lines pass through the center of the hole and are thus called center lines. The size and the shapeof an object are communicated by detail drawings. These are constructed of a series of light long and shortdashes.
Dimensioning uses two kinds of lines. First, the extension lines indicate the points from which themeasurements are taken. Between the extension lines are dimension lines. These have arrows (or otherterminators) pointing to the extension lines that indicate the range of the dimension. The dimension andextension lines are the same weight as hidden lines4.00
Objective 4.05
Explain computer processes used in computerized 2D/3D modeling
The following outline characterizes what should be taught under Objective 4.05
Describe the advantages of CAD
Describe applications of CAD
Describe CAD terminology
CAD/CADD
CAD (Computer-Aided Design) refers to a process that uses a computer and drawing software to assist thedrafter in preparing mechanical or architectural drawings. CADD (Computer-Aided Design and Drafting) isclosely related to CAD. CADD systems use extra functions that simulate testing products. Professionaldesigners use CADD to increase the quality of their work.
Advantages of CAD - The heart of a CAD system is the computer. A computer is capable of producingdrawings much faster than humans. Computers can be programmed to perform certain complex functions with just the push of a single key. A traditional drafter may have to complete dozens of pencil strokes to perform the same function. Computers are generally more accurate than humans, and they can perform the same functionover and over without errors or deviations. CAD has several advantages over traditional drafting methods.
Four advantages of CAD are: speed, quality, ease of modification, and cost.
Speed – using a CAD system, a drafter can produce more drawings in a given amount of time than by usingtraditional drafting methods. In traditional drafting, every drawing is created by moving a pencil. Thetraditional drafter must use several tools just to produce a line. Every line must be carefully planned to preventmistakes. If a mistake is made, all incorrect lines must be thoroughly erased and redrawn. Sometimes, theentire drawing must be redrawn. Using CAD, many tasks are performed automatically. For instance, to draw aline, the operator simply sets the end points for the line, and the system does the rest. No drawing board, Tsquare,triangle, scale or pencil is required. With CAD, repetitive tasks can be accomplished with just the pushof a single key. Using the COPY command, the drafter can duplicate identical objects. Dimensions can be seton a CAD system more quickly than traditional methods, and many CAD programs have symbol librarieswhich contain commonly used symbols for a particular application. This eliminates the need to draw a symboleach time it is needed.
Quality – in addition to being quicker, CAD systems increase quality. The overall quality of a design isimproved by increasing line quality, neatness, legibility, and accuracy. It is hard to achieve consistent linequality each time using traditional methods. Using CAD, the computer draws the same width line every time.
With traditional methods, drawings become smeared and smudged as tools are moved across the paper. In