CHAPTER 1 INTRODUCTION 1.1 Project Title The component shown in Figure 1.1 need to be drilled all holes and machined on the surface marked. A suitable jig or jigs and a fixture or fixtures are required to be designed. Use modular fixturing technique.
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CHAPTER 1
INTRODUCTION
1.1 Project Title
The component shown in Figure 1.1 need to be drilled all holes and machined on the
surface marked. A suitable jig or jigs and a fixture or fixtures are required to be designed.
Use modular fixturing technique.
Figure 1.1: Component
1.2 Introduction to Tool Design
Tool design is the process of designing and developing the tools, methods, and
techniques necessary to improve manufacturing efficiency and productivity. Tool design
is also an integral part of the product-planning process, interacting with product design,
manufacturing, and marketing.
1.3 Tool Design Objectives
The main objective of tool design is to lower manufacturing costs while maintaining
quality and increased production. To accomplish this, the tool designer must satisfy the
following objectives:
i. Provide simple, easy-to-operate tools for maximum efficiency.
ii. Reduce manufacturing expenses by producing parts at the lowest possible cost.
iii. Design tools that consistently produce parts of high quality.
iv. Increase the rate of production with existing machine tools.
v. Design the tool to make it foolproof and to prevent improper use.
vi. Select the materials that will give adequate tool life.
vii. Provide protection in the design of the tools for maximum safety for operators.
CHAPTER 2
TOOL DESIGN
2.0 Tool Design
Tool design is the process of designing and developing the tools, methods, and
techniques necessary to improve manufacturing efficiency and productivity. It gives
industry the machines and special tooling needed for today’s high-volume production. It
is a specialized area of manufacturing engineering which comprises the analysis,
planning, design, construction and application of tools, methods and procedures
necessary to increase manufacturing productivity.
2.1 Creative Tool Design
Tool design is basically an exercise in problem solving. Creative problem solving ca be
described as a five-step process:
1. Defining Requirements
The new tooling might be required either for the first-time production of a new
product, or to improve production of an existing part. When improving and
existing job, the goal might be greater accuracy, faster cycle times, or both.
Tooling might be designed for one part, or an entire family.
2. Gathering and Analyzing Information
In the second design phase, all data is collected and assembled for evaluation. The
main sources of information are the part print, process sheets, and machine
specifications. When collecting this information, make sure that part documents
and records are current. Note taking is an important part of the evaluation process.
Complete and accurate notes allow designer to record an important information.
All ideas, thoughts, observations, and any other data about the part or tool are
then available for later reference. Good notes also minimize the chance that good
ideas will be lost.
Checklist for Design Considerations
Workpiece:
Size
Shape
Required accuracy
Material type
Material condition
Locating points
Locating stability
Clamping surfaces
Production quantity
Pending part-design revisions
Operations:
Types of operations
Number of separate operations
Sequence
Inspection requirements
Equipment:
Machine tools
Cutting tools
Special machinery
Assembly equipment and tools
Inspection equipment and tools
Equipment availability and scheduling
Plant space required
Personnel:
Safety equipment
Safety regulations and work rules
Economy of motion
Operator fatigue
Power equipment available
Possible automation
3. Developing Several Options
This requires the most creativity. A typical workpiece can be located and clamped
many different ways. An important strategy for successful tool design is
brainstorming for several good tooling alternatives, not just choosing one path
right away.
4. Choosing the Best Option
Choosing the best option is a cost or benefit analysis of different tooling option.
Some benefits, such as greater operator comfort and safety, are also important.
Other factors, such as tooling durability, are difficult to estimate. Cost analysis is
sometimes more of an art than a science.
5. Implementing the Design
The final phase of the tool-design process consists of turning the chosen approach
into reality. Final details are decided, final drawings are made, and the tooling is
built and tested.
Guidelines for Economical Design:
Use standard tooling components
The economics of standardized parts apply to tooling components as well
as manufactured products. Never build any component that you can buy.
Use prefinished materials.
Prefinished and performed materials should be used where possible to
lower costs and simplify construction.
Keep tolerances as liberal as possible
Tighter tolerances normally add extra cost to the tool with little benefit to
the process.
Simplify tooling operation.
Elaborate designs often add little or nothing to the function of the jig or
fixture. Reducing design complexity also reduces misunderstandings
between the designer and the machine operator.
The guidelines should be considered during the final-design process. Application
of these rules makes the work holder less costly, and improves its efficiency and
operation.
CHAPTER 3
JIGS AND FIXTURES
3.1 Introduction
The successful running of any mass production depends upon the interchangeability to
facilitate easy assembly and reduction of unit cost. Mass production methods demand a
fast and easy method of positioning work for accurate operations on it. Jigs and fixtures
are production tools used to accurately manufacture duplicate and interchangeable parts.
Jigs and fixtures are specially designed so that large numbers of components can be
machined or assembled identically, and to ensure interchangeability of components. In
order to do so, a jig or fixture is designed and built to support, hold, and locate every part
to ensure that each is drilled according to its specifications. Both terms are frequently
used incorrectly in shops. A jig is a guiding device and a fixture a holding device.
Jigs and fixtures are used to locate and hold the work that is to be machined.
These devices are provided with attachments for guiding, setting, and supporting the tools
in such a way that all the workpiece produced in a given jig or fixture will be exactly
identical in every way. The employment of unskilled labor is possible when jigs and
fixtures can be used in production work. A jig or fixture can be designed for a particular
job. The form to be used depends on the requirement and shape of the workpiece to be
machined.
3.2 Elements of Jigs and Fixtures
Generally, all the jigs and fixtures consist of the following elements:
i. Locating elements
Locating elements are used to establish and maintain the position of a workpiece
by constraining the movement of the workpiece. These position the workpiece
accurately with respect to the supporting elements tool in the jigs and fixtures. A
locating element is usually a fixed component and is used to establish, maintain
the position of a part by constraining the movement of the part. For workpiece of
greater variability in shapes and surface conditions, a locator can also be
adjustable.
ii. Clamping elements
Clamping elements hold the workpiece securely in the located position during
operation. A clamp is a force-actuating mechanism. The forces exerted by the
clamps hold a part securely against all other external forces.
iii. Tool guiding and setting elements
To aid the setting or guiding of the tools in the correct position with respect to the
workpieces.
3.2 Jigs
A jig is any of a large class of tools in woodworking, metalworking, and some other
crafts that help to control the location or motion (or both) of a tool. The primary purpose
for a jig is for repeatability and exact duplication of a part for reproduction. An example
of a jig is when a key is duplicated, the original is used as a jig so the new key can have
the same path as the old one. Since the advent of automation and CNC machines, jigs are
often not required because the tool path is digitally programmed and stored in memory.
The most-common jigs are drill and boring jigs. These tools are fundamentally the same.
The difference lies in the size, type, and placement of the drill bushings. Boring jigs
usually have larger bushings. These bushings may also have internal oil grooves to keep
the boring bar lubricated. Often, boring jigs use more than one bushing to support the
boring bar throughout the machining cycle.
Jig that expedites repetitive holes center location on multiple interchangeable
parts by acting as a template to guide the twist drill or other boring device into the precise
location of each intended holes center. In metalworking practice, typically a hardened
bushing lines each hole on the jig to keep the twist drill from cutting the jig as shown in
Figure 3.1. Jigs or templates have been known long before the industrial age. There are
many types of jigs, and each one is custom-tailored to do a specific job. Many jigs are
created because there is a necessity to do so by the trades men. Some are to increase
productivity, to do repetitious activities and to do a job more precisely.
Figure 3.1: Jig
Jigs may be divided into two general classes: boring jigs and drill jigs. Boring jigs
as shown in Figure 3.2 are used to bore holes that either is too large to drill or must be
made an odd size. Drill jigs are used to drill, ream, tap, chamfer, counterbore, countersink
and reverse. Basic jig is almost the same for either machining operation. The only
difference is in the size of the bushings used.
Figure 3.2: Boring Jig
3.3 Fixtures
Fixtures have a much-wider scope of application than jigs. These work holders are
designed for applications where the cutting tools cannot be guided as easily as a drill with
fixtures, an edge finder, center finder, or gage blocks position the cutter. Examples of the
more-common fixtures include milling fixtures, lathe fixtures, sawing fixtures, and
grinding fixtures. Moreover, a fixture can be used in almost any operation that requires a
precise relationship in the position of a tool to a workpiece.
Fixtures are essential elements of production processes as they are required in
most of the automated manufacturing, inspection, and assembly operations. Fixtures must
correctly locate a workpiece in a given orientation with respect to a cutting tool or
measuring device, or with respect to another component, as for instance in assembly or
welding. Such location must be invariant in the sense that the devices must clamp and
secure the workpiece in that location for the particular processing operation. There are
many standard work holding devices such as jaw chucks, machine vises, drill chucks,
collets, etc. which are widely used in workshops and are usually kept in stock for general
applications.
Fixtures are normally designed for a definite operation to process a specific
workpiece and are designed and manufactured individually. Jigs are similar to fixtures,
but they not only locate and hold the part but also guide the cutting tools in drilling and
boring operations. These work holding devices are collectively known as jigs and fixture.
Set blocks and feeler or thickness gauges are used with fixtures to reference the cutter to
the work piece. A fixture should be securely fastened to the table of the machine upon
which the work is done. Though largely used on milling machines, fixtures are also
designed to hold work for various operations on most of the standard machine tools.
Fixtures vary in design from relatively simple tools to expensive, complicated devices.
Fixtures also help to simplify metalworking operations performed on special equipment.
Fixtures are most often identified by the machine tool where they are used.
Examples include mill fixtures or lathe fixtures. But the function of the fixture can also
identify a fixture type. So can the basic construction of the tool. Thus, although a tool can
be called simply a mill fixture, it could also be further defined as a straddle-milling,
plate-type mill fixture. Moreover, a lathe fixture could also be defined as a radius-turning,
angle-plate lathe fixture. The tool designer usually decides the specific identification of
these tools. It use set blocks and thickness, or feeler, gages to locate the tool relative to
the workpiece as shown in Figure 3.3.
Figure 3.3: Set Block
Fixtures are normally classified by the type of machine on which they are used.
Fixtures can also be identified by a sub classification. For example, if a fixture is
designed to be used on a milling machine, it is called a milling fixture. If the task it is
intended to perform is straddle milling, it is called a straddle milling fixture. The same
principle applies to a lathe fixture that is designed to machine radii. It is called a lathe-
radius fixture.
The following is a partial list of production operations that use fixtures: