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Manufacturing Processes 003. Demonstrate basic concepts of manufacturing processes 003.01 Explain the concepts of manufacturing processes 003.02 Explain the ANSI standards of applying annotations to a drawing that best describes the manufacturing process 003.03 Demonstrate the skills needed in applying annotations to a drawing that best describes the manufacturing process

Manufacturing Processes - cabarrus.k12.nc.us · Web viewModern meaning of the word manufacturing is the process of converting raw materials into products. ... There is a wide variety

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Manufacturing Processes

003.

Demonstrate basic concepts of manufacturing processes

003.01

Explain the concepts of manufacturing processes

003.02

Explain the ANSI standards of applying annotations to a drawing that best describes the manufacturing process

003.03

Demonstrate the skills needed in applying annotations to a drawing that best describes the manufacturing process

UNIT C: Manufacturing Processes

Competency: D403.00

Demonstrate basic concepts of manufacturing processes.

Objective: D403.01

Explain the concepts of manufacturing processes.

Introduction: Before preparing a drawing for the production of a part, the drafter/designer must consider what manufacturing processes are to be used. These processes will determine the representation of the detailed features, choice of dimensions, and machining accuracy.

The purpose of this unit is to provide the student with information about terms and processes used in manufacturing that will assist them with the skills needed to development mechanical drawings for industry.

Manufacturing: R1 (271)

A. The word manufacturing is derived from the Latin “manu factus”, meaning “made by hand”. Modern meaning of the word manufacturing is the process of converting raw materials into products.

B. The manufacturing process involves three important phases: 1) product design, 2) selection of materials, and 3) the selection of various manufacturing production methods and techniques.

C. Any number of process methods may be used by industry. For this reason, the designer and the drafter must have a working knowledge of the various processes that could produce a part in order to lower cost and reduce production time.

D. The information needed to produce a part in a manufacturing department, most often comes in the form of a working drawing.

Manufacturing Processes: R1 (281), R3 (226), R4 (293)

A. In the actual processing of a part consists of three main stages: 1) Rough forming, 2) Finishing, and 3) Assembly.

B. Rough Forming – consist of shaping the part by casting, forging, and welding.

1. Casting

a. Sand Casting is made by pouring molten metal into a cavity in damp sand. Once it cools and is removed from the mold the part is then machined.

b. Die Castings are formed by forcing molten metal into cavities between metal dies.

i. This process is much faster than sand casting and is used where rapid production is used.

ii. It also requires little or no machining.

2. Forging

a. Drop forging is produced by hammering heated bars of metal between dies.

b. Press forging is produced by applied by a slowly squeezing action.

c. Advantage of forgings over castings is that forgings are much stronger.

3. Welding

a. The process of fusion or joining of two pieces of metal by means of heat.

b. Usually a part is built up from cut stock forms, assembled, and welded together.

C. Finishing – is largely done in the machine shop to finish sizing holes and surfaces.

1. Machining

a. Machining might require the use of a grinding machine, lathe, milling machine, and or drill press

b. The above machines will allow the machinist to: turn, bore, ream, mill, and grind a part to a specific size and shape.

2. Finishing might include: polishing, burnishing, deburring, surface treating, coating, and plating.

D. Assembly – various parts are put together to complete the product. This may require additional machining however this retooling costs money and downtime. Manufacturers look to their company designers and engineers to keep manufacturing cost in check. One way of accomplishing this is to produce 3D solid models using CAD software that allows designers and engineers to update and modify their assembly drawings to fit changing criteria.

Manufacturing Materials: R1 (279), R4 (287)

A. There is a wide variety of materials available for production manufacturing that fall into three general categories: metal, plastic, and inorganic materials.

B. Metals are classified as ferrous, nonferrous, and alloys.

1. Ferrous metals contain iron, and steel.

2. Nonferrous metals do not have iron content, such as copper and aluminum for examples.

3. Alloys are a mixture of two or more metals.

C. Inorganic materials include carbon, ceramics, and composites.

1. Carbon and graphite or classified together and have low tensile strength (ability to be stretched).

2. Ceramics are clay and glass materials. These materials are resistant to heat, chemicals, and corrosion.

D. Plastics - See “Plastics Processing” below for more information.

Heat-Treating: R3 (240)

The process of changing the properties of metals by heating and cooling is referred to as heat-treating.

A. Annealing – is the process generally used to soften metal by heating followed by slow cooling.

B. Hardening – requires heating and then rapid cooling in oil or water.

Plastics Processing: R3 (242), R4 (290)

A. The plastics industry represents one of the major manufacturing segments. There are two main families of plastics, thermosetting and thermoplastic.

1. Thermosetting Process – These products are formed into a permanent shape by heat and pressure and may not be altered after curing. This process is more expensive and can be more difficult than others because thermoset materials cannot be remelted once they have been melted and formed for the first time. Thermoset products are the choice when the product is used in an application where heat exists such as plastic parts found on or near the engine of a car. The most common production process is casting.

2. Thermoplastic Process – Plastic material may be heated and formed by pressure. Upon reheating, the shape can be changed. Most plastic products are made with this process because they are easier to mold into various shapes. These products cannot be used where heat might exist.

B. Typical plastic processing operations include:

1. Extrusion Process– used to make continuous shapes such as moldings, tubing, bars, water hose, weather stripping, and any part that has a constant shape. This process creates the desired continuous shape by forcing molten plastic through a metal die.

2. Blow Molding Process – used in the production of hollow products such as bottles and containers. The molten plastic enters around a tube that also forces air inside the material, which forces it against the interior surface of the mold to create the shape desired.

3. Injection Molding – is the most commonly used process for creating thermoplastic products. The process involves injecting molten plastic material into a mold that is in the form of the desired shape. Injection molding is used to create products such as housings for electronic implements, automotive interior components, food storage containers, and components for medical applications.

C. Thermoforming of Plastic Process – is used to make all types of thin-walled products, such as containers, guards, fenders, food packages, and cosmetic packaging. The process works by taking a sheet of plastic material and heating it until it softens. Vacuum pressure is then applied to suck the hot material down against the mold to conform to the desired shape.

Computers in Manufacturing: R1 (273), R3 (242), R4 (322)

A. Computer-aided drafting / computer-aided manufacturing (CAD/CAM) is the process of developing a design drawing on a CAD system and producing the part on a computerized machine.

B. Computer Numerical Control (CNC) is the method of controlling the movements of machine components by direct insertion of coded insertion of coded instructions in the form of numerical data.

C. The advantages of the CNC machining are: better production and control, increased productivity, decreased labor, and production costs.

Measuring Devices Used in Manufacturing: R1 (284), R3 (233)

A. Machinist Steel Rule.

1. Used for common fractional measurements.

2. The smallest division of this rule is 1/64”.

B. Caliper

1. Used when more precise measurements are required.

2. Measurements may be given in decimal, fractional, or metric.

3. Often used by drafters to record dimensions from a machined prototype or part.

4. Caliper instrument will give the machinist four types of measurements; Step, Inside, Outside, and Depth. See Figure 1.

METRIC (mm)

DECIMAL (.XX)

FRACTIONAL (1/64”)

Figure 1. 6 Inch Dial Caliper

UNIT C: Manufacturing Processes

Competency: D403.00

Demonstrate the basic concepts of the manufacturing processes.

Objective: D403.02

Explain the ANSI standards of applying annotations to a drawing that best describes the manufacturing process.

Introduction: The purpose of this unit is to generate student awareness of the use of detailed annotations needed to describe the manufacturing process in the development of a part.

Manufacturing Annotations: R1 (292-328), R2 (229-275) R3 (193-223), R4 (332-385)

A. Two Kinds of manufacturing notes:

1. General Note – applies to general information about the part as a whole. Such as: Fillets & Rounds are to be R.125.

FINISH all over.

2. Local Note – is a note that is connected to a leader pointing to the appropriate area applying to a specific machining operation.

B. Drilling Terminology and Callouts

1. Drill - Is the process used to cut a cylindrical hole with a drill press and drill bit.

2. Boring - Enlarges the hole slightly and making it rounder and straighter.

3. Ream - To enlarge a hole to a more accurate size and surface quality.

4. Machined holes by their profiles (see Figure 1):

a. Through – a through hole is one that passes all the way through the object.

b. Blind – a blind hole cuts into but does not pass completely through the object.

c. Counterbore - To enlarge the end of a drill hole to a specific diameter and depth in order to recess a mating part.

d. Countersink - To recess a hole with a conically (cone) shaped tool to provide a seat for flat head screws.

e. Spotface - The cutting of a shallow counterbore, usually about .0625 deep (depth symbol is omitted). The spotface depth does not need to be specified. The spotface provides an accurate bearing surface for the underside of a bolt head.

Figure 1. Types of Holes

5. Standards for annotations and symbols when identifying hole callouts.

a. Notes should always be lettered horizontally on the drawing paper.

b. Always attach leaders at the front of the first word of a note, or after the last word.

c. When sizing a drill hole the arrowhead of the leader should point towards the center of the circle. When the circular view of the hole has two or more concentric circles, as for a counterbore, the arrowhead should touch the most outer circle.

d. Fractional size drills are available drill sizes of 1/16” diameter to 3-1/2” diameter. It is common practice (as recommended by ANSI) to give the drill size in decimal-inch size for all diameters.

e. For numbered or letter-size drills it is recommended that the decimal size be given in parentheses; thus,

#25 (.1495) DRILL, E (.250) DRILL.

The word DRILL may be omitted from the note.

f. Metric drills are usually listed separately with a decimal-millimeter value.

g. Repetitive drill holes with the same diameter are specified by the use of an X following the number of times the hole is required; thus, 4X n.375 (four holes with a diameter of .375)

h. Holes equally spaced about a common center are located by giving the center of the holes and diameter of the bolt circle (BC). See Figure 2.

Figure 2. Holes Spaced Equally about a Center.

i. The order of the drill callout corresponds to the order of procedure in the shop in producing the hole. For example: The smaller drilled hole is given first, then the counterbore diameter, followed by the depth.

Counterbore Example:

Countersink Example:

Spotface Example:

Note:

· The symbol is placed in front of the decimal size.

· The depth for spotface is commonly know to be .0625 and is not normally required with the hole callout.

C. Surface Texture Symbols:

1. Used to indicate that a surface is to be machined, or finished.

2. It is not necessary to show the finish marks for machining processes such as drilling, reaming, boring, etc.

3. The check mark symbol is the preferred symbol by ANSI. See Figure 3.

3H

1.5H

60°

Figure 3. Surface Texture Symbol.

4. The point of the vertex of the finish mark should be directed inward toward the body of the part. Such as that of a cutting tool.

5. The finish mark symbol should be positioned to read from the bottom of the sheet or from the right side of the sheet, as shown in Figure 4.

6. The finish mark is only shown on the edge view of a finished surface and is repeated in any other view in which the surface appears as a line, even if the line is a hidden line.

7. If a part is to be finished all over, finish marks are omitted and a general note such as, FINISH ALL OVER or FAO should be placed in the lower portion of the sheet, next to the title block.

Figure 4. Orientation of Finish Marks to Machined Surfaces.

D. Knurling – is a roughened surface commonly found on thumbscrews and handles of various kinds to provide a better grip. Also can be created to provide a press fit between two parts (see Figure 5).

1. Types of Knurls

a. Diamond – crossing diagonal groves.

b. Straight – parallel groves

2. Dimensioning of Knurls.

a. For handgrip knurls, only the pitch of the knurl (sometimes listed as fine, medium, or coarse), the type of knurl (diamond or straight), and the length of the knurl area are required.

b. For a press fit type knurl, the tolerance diameter of the class of fit is given before the actual knurling note. The most commonly used diametrical pitches (DP) are 64 DP (coarse), 96 DP (medium), 128 DP (fine), and 160 DP (extra fine).

c. A knurl symbol (hatching pattern) does not have to be shown on the drawing when a local note is applied.

1.89

.82

Ø

1.25

96 DP

STRAIGHT KNURL

Figure 5. Dimensioning a Knurl.

E. Fillets and Rounds - are normally found on cast, forged, and plastic parts.

1. The purpose of fillets and rounds is to add strength and protection from sharp edges.

2. A rounded interior corner is called a fillet.

3. A rounded exterior corner is called a round.

4. The presence of the curved surfaces is indicated only where they appear as arcs.

F. Runouts – is the method of representing fillets in connection with plane surfaces tangent to cylinders. See Figure 6.

Figure 6. Conventional Fillets, Rounds, and Runouts.

G. Conventional Edges – rounded and filleted intersections eliminate sharp edges and sometimes make it difficult to present a clear shape description. True projection may actually be misleading. Projection lines should project from the actual intersection of the surfaces as if the fillets and rounds were not present (see Figure 7).

No Line

Figure 7. Conventional Edges.

H. Chamfer – is a beveled edge and it is dimensioned by giving the length of the offset and the angle (see Figure 8).

.

Figure 8. External and Internal Chamfers