working drawings and assemblies
TRANSCRIPT
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Working Drawing and
Assemblies
Chapter 10
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Objectives
1.Define working drawings.
2. Describe how working drawings are used inindustry.
3. List the major components of a complete setof working drawings.
4. Describe the differences between detail andassembly drawings.
5. Describe how part numbers, zoning, andtables are used on working drawings.
6. Draw standard representation of threads.
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Objectives
7. Specify a metric or English thread in a note.
8. Use the graphic language of mechanisms
such as gears, cams, bearings, and linkages.
9. Interpret the specialized graphic language
used in piping and welding drawings.
10. Describe how CAD is used to create, store,
and retrieve working drawings.
11. List techniques used to create copies of
engineering drawings.
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Working Drawings
Working drawings are the
complete set of standardized
drawings specifying the
manufacture and assembly of a
product based on its design.
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Working Drawings
The complexity of the design
determines the number and types
of drawings.Working drawings may be on more
than one sheet and may contain
written instructions calledspecifications.
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Working Drawings
Working drawings are the blueprints
used for manufacturing products.
Therefore, the set of drawings must: completely describe the parts, both visually
and dimensionally
show the parts in assembly
identify all the parts
specify standard parts.
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Working Drawings
A complete set of working drawings for
an assembly include:
detail drawings of each nonstandard part. an assembly or subassembly drawing
showing all the standard and nonstandard
parts in a single drawing.
a bill of materials (BOM). a title block.
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Detail Drawings
A detail drawing is a dimensioned,
multiview drawing of a single part,
describing the parts shape, size,material, and finish, in sufficient
detail for the part to be
manufactured based on the drawingalone.
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Assembly Drawings
An assembly drawing shows how
each part of a design is put
together. If the design depicted isonly part of the total assembly, it is
referred to as a subassembly.
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Assembly Drawings
An assembly drawing normally consists of:
All the parts, drawn in their operating position.
A parts list orbill of materials (BOM) shows the
detail number for each part, the quantity needed fora single assembly the description or name of thepart, the catalog number if it is a standard part, andthe company part number.
Leader lines with balloons, assigning each part a
detail number, in sequential order and keyed tothe list of parts in the parts list.
Machining and assembly operations and criticaldimensions related to these functions.
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Assembly Drawings
Types
outline assembly gives a general
graphic description of the exteriorshape. Outline assemblies are used
for parts catalogs and installation
manuals or for production when the
assembly is simple enough to bevisualized without the use of other
drawings.
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Assembly Drawings
Types
sectioned assembly gives a general
graphic description of the interiorshape by passing a cutting plane
through all or part of the assembly.
Sectioned assembly drawings are
used for the manufacture andassembly of complicated devices.
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Assembly Drawings
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Assembly Drawings
Types
pictorial assembly gives a general
graphic description of each part, anduses center lines to show how the
parts are assembled.
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Part and Drawing Numbers
A part number is usually a string of numbers
coded in such a way that a company can keep
accurate records of its products.
Drawing number: Each company develops its
own standard numbering system, based on
various criteria such as sequential numbers,
combinations of numbers and letters, sheet
sizes, number of parts in the assembly, modelnumbers, function, etc.
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Title Blocks
Title blocks are used to record all theimportant information necessary for the workingdrawings. The title block is normally located in
the lower right corner of the drawing sheet. Title blocks should contain the following:
Name and address of the company ordesign activity.
Title of the drawing. Drawing number.
Names and dates of the drafters, checker,issue date, contract number, etc.
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Title Blocks
Design approval, when subcontractors areused.
Additional approval block.
Predominant drawing scale.
Federal supply code for manufacturers(FSCM) number.
Drawing sheet size letter designation.
Actual or estimated weight of the item.
Sheet number, if there are multiple sheetsin the set.
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Parts Lists
A complete set of working drawings
must include a detailed parts list or
bill of material. Based on ANSIstandards, a parts list should be
located in the lower right corner
above the title block.
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Parts Lists
The information normally included in a parts list
is as follows:
Name of the part.
A detail number for the part in the assembly.
The part material, such as cast iron or bronze.
The number of times that part is used in the
assembly.
The company-assigned part number.
Other in formation, such as weight, stock size,
etc.
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Revision Blocks
When a drawing is revised because of design
changes, errors, etc., an accurate record of the
change should be created.
This information includes:
the person making the change
description of the change
the change number approval for the change
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Engineering Changes Order
Used to make changes in a design.
Most industries require the use of
engineering change notice (ECN).Common features includes;
Identification of what has to be
changed in the form of part numbers,part names, and drawing numbers.
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Engineering Changes Order
An explanation of the need for the
requested changed.
A list of all documents anddepartments affected by the change.
Approval by the projects managers
Instruction describing when thechanges are to be implemented.
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Scale and Tolerance Specs.
The designations METRIC or SI appear in or
near the title block to show that metric
dimensions and scale are used on the drawing.
A graphics scale can also be used, especiallyon mapping drawings.
Tolerances are specified in a drawing using
toleranced dimensions. For those dimensions
that are not specifically toleranced, a generaltolerance note is used.
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Zones and Tabular Drawing
Zones are used on large sheets for
reference purposes. Zones in
engineering drawing are similar to thezones used on highway maps.
Tabular drawings are used when
several similar parts have common
features. Such parts can be groupedtogether into a family of parts.
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Working Assembly Drawing
A working assembly drawing, also
known as a detailed assembly,
combines on a single sheet the detaildrawing and the assembly drawing,
usually a section view. Such drawings
are used for relatively simple assemblies
that use some standard parts.
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Threaded Fastener
Fastening is a method of connecting or
joining two or more parts together, using
processes or devices.One of the most common methods used
for fastening is mechanical fastening, a
process that uses manufactured devices
such as screws, pins, or rivets to holdparts of an assembly together.
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Thread Terminology
Axis
Chamfer
Crest
Depth
Die
External thread
Internal thread
Lead
Major Diameter
Minor Diameter
Pitch
Pitch diameter
Root
Screw thread
Side
Tap
Thread: angle, form,series
Thread per inch
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Thread Specification
English system
Thread form - the profile or shape of a thread cutinto a cylinder.
Sharp-VAmerican National
Unified
Unified National Round
Metric
Acme Square
Knuckle
Buttress
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Thread Specification
English system
Series - the number of threads per inch for a given
diameter.
Coarse quick assembly or disassembly of castiron, soft metals, and plastic. NC or UNC.
Fine - fasteners are used when a great deal of
force is necessary for assembly, and are
designated NF or UNF.
Extra fine - fasteners are used when the length ofengagement is short and the application calls for
high degrees of stress.
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Thread Specification
English system
Class
Class 1-a loose fit where quick assembly is
required and looseness or play between partsis acceptable.
Class 2-a high-quality, general purpose,commercial class of fit for bolts, nuts, andscrews widely used in mass production.
Class 3-a very high-quality threaded fastenerwith a close fit, used for precision tools andfor high stress and vibration applications.
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Threaded Specification
English system
Note
Major diameterNumber of threads
Form
Series
Class Internal or external
Qualifying information
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Thread Specification
Metric system
A complete metric thread note should
contain the following information, in theorder given:
Thread form symbol- The letter M is used to
designate the metric profile. The J profile
class is a modified M profile.
Nominal size (basic major diameter)
Pitch
General purpose tolerance
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Thread Drawings
Three conventional methods:
Detailed
Schematics Simplified
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Standard Bolts, Stud and
ScrewGeneral types of standard threaded
fastener:
Bolt - a mechanical threaded device with a
head on one end and threads on the otherend. Bolts are paired with nuts. A nut is amechanical threaded device used on theend of a bolt, a stud, or a machine screw.
Stud - a rod that is threaded on both endsand joins two mating parts. A nut may beused on one end.
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Standard Bolts, Stud and
Screw
Cap screw - a mechanical threadeddevice with a head on one end and threads
on the other end. Cap screws join twomating parts and have longer threads thanbolts.
Machine screw - a mechanical threaded
device with a head on one end and threadson the other end. The threaded end mayscrew into a mating part, or may be usedwith a nut.
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Standard Bolts, Stud and
Screw
Set screw - a mechanical threaded device
with or without a head, used to prevent
rotation or movement between parts, such
as a shaft and a collar.
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Nonthreaded Fastener
Nonthreaded fasteners are mechanical
devices generally used to prevent motion
between mating parts. Dowels
Pins dowel, straight, tapered, groove
Key plain, gib head, Woodruff, P&W
Rivet
Retaining rings
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Springs
Mechanical devices that expand or
contract due to pressure or force.
Compression Tension
Extension
Flat
Constant force
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Mechanism
A machine is a combination of interrelated
parts for using or applying energy to do work.
Gears - transmit rotational power and motion
between portions of a mechanism. Cams - used to translate rotational motion into
linear motion.
Linkages - the most common type of mechanism in
use to transmit force. A linkage consists of a
(usually) linear element, called the bar, and one or
twojoints.
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Mechanism
Bearings - used in conjunction with other
mechanisms such as gears and
linkages to minimize friction and wear
between the parts.
Plain
Rolling contact
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Welding
Welding drawings are a specialized
type of technical drawing which differs
from many other types of drawings in
that its main focus is to specify how parts
are joined together. Since welds are both
permanent and structural, proper
location and orientation of the weldedmembers and the type of weld used are
important to properly specify.
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Welding
Eight basic parts;
Reference line
Leader line and arrow
Basic weld symbol (location and depth of weld)
Finish symbol
Weld symbol (type of weld)
Dimensions
Supplementary symbols Tail and specifications
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Reprographics
Refers to the technology and techniques of
reproducing documents. After the engineering
drawings have been created they are copied for
others to use, carefully stored, and set up foreasy future accessibility.
After the original drawing is created, it must be
carefully stored or archived. The process used
to store and retrieve engineering drawings iscalled archiving.
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Reprographics
Techniques
Blueprinting
Diazo Xerography
Microfilming
Digital
Scanning
Storage CAD