Jigs and Fixtures

• Jigs and fixtures are devices used to facilitate production work,

• making interchangeable pieces of work possible at a savings in cost of production.

• 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 manner that all the work pieces produced in a given jig or fixture will be exactly alike in every way.

• The employment of unskilled labor is possible when jigs and fixtures can be used in production work.

• The repetitive layout and setup (which are time-consuming activities and require consider- able skill) are eliminated.

• Also, the use of these devices can result in such a degree of accuracy that work pieces can be assembled with a minimum amount of fitting.

• A jig or fixture can be designed for a particular job.

• The form to be used depends on the shape and requirement of the work piece to be machined

Types Of Drilling Jigs:

Drilling jigs may be classified as follows:

1. Template jig

2. plate type jig

3. Open type jig

4. Channel jig

5. Leaf Jig

6. Box type jig

1: Template Jig:

simplest type of jig;

It is a plate made to the shape and size of the work piece; with the require number of holes made it.

It is placed on the work piece .

This type of jig is suitable if only a few part are to be made.

2: Plate Type Jig:

improvement of the template type of jig.

In place of simple holes, drill bushes are provided in the plate to guide the drill.

The work piece can be clamped to the plate and holes can be drilled.

The plate jig are employed to drill holes in large parts, maintaining accurate spacing with each other.

3:Open Type Jig:

In this jig the top of the jig is open; the work piece is placed on the top.

4 Channel jig;

The channel jig is a simple type of jig having channel like cross section. The component is fitted within the channel is located and clamped by locating the knob. The tool is guided through the drill bush.

5: Leaf Jig:

It is also a sort of open type jig , in which the top plate is arrange to swing about a fulcrum point , so that it is completely clears the jig for easy loading and unloading of the work piece. The drill bushes are fitted into the plates

6: Box Type Jig:

When the holes are to drill more than one plane of the work piece

DIAMETER JIG

Channel jig

Fixtures

• A fixture is a device for locating, holding and supporting a work piece during a manufacturing operation.

• 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 work piece in a given orientation with respect to a cutting tool or measuring device.

Elements of Fixtures

Generally, all fixtures consist of the following elements

Locators • A locator is usually a fixed component of a

fixture. • It is used to establish and maintain the position of

a part in the fixture by constraining the movement of the part.

• For work pieces of greater variability in shapes and surface conditions, a locator can also be adjustable.

• Clamps

• A clamp is a force-actuating mechanism of a fixture. The forces exerted by the clamps hold a part securely in the fixture against all other external forces.

• Supports

• A support is a fixed or adjustable element of a fixture.

• When severe part displacement/deflection is expected under the action of imposed clamping and processing forces, supports are added and placed below the work piece so as to prevent or constrain deformation.

• Fixture Body

• Fixture body, or tool body, is the major structural element of a fixture.

• It maintains the spatial relationship between the fixturing elements mentioned above,

• viz., locators, clamps, supports, and the machine tool on which the part is to be processed.

A typical 'tombstone' fixture for a horizontal CNC machine

Types of Fixtures

• Milling fixtures: • Milling operations tend to involve large cuts that

produce lots of chips and involve varying force. Locating and supporting areas must usually be large and very sturdy

• strong clamps required. • Due to the vibration of the machine, positive

stops are preferred for securing the work piece. • For high-volume automated processes, milling

fixtures usually involve hydraulic or pneumatic clamps.

• Drilling fixtures • Drilling fixtures cover a wider range of different

designs and procedures than milling fixtures. • Work holding for drills is more often provided by

jigs, fixtures are also used for drilling operations. • Two common elements of drilling fixtures are the

hole and bushing. • Holes are often designed into drilling fixtures.

Bushings are simple bearing sleeves inserted into these holes to protect them and guide the drill bit.

3-2-1 principle of location.

A rule that defines the minimum number of contact points necessary to properly locate a part within the datum reference frame. The primary datum requires three points, the secondary datum two points, and the tertiary datum one point.

CLAMPING DEVICES

Gen Principle of jig fixture design

• Location and clamping to reduce idle time

• To allow quick loading and unloading

• Avoid improper loading of work

• Provided with sufficient clearance

• Stiff and rigid

• Easy ejection

• Safe and convenient to use

• Simple design

Modern trends

Inventory reduction : by

• Eliminating excess inventory

• Improving inventory turn rate

• Increasing inventory turnover

• Meeting on time delivery

One-Piece Flow

• Batch-and-Queue systems lead to poor space utilization .

• longer cycle times, • a higher probability of defects • lower morale because batch-and-queue leads to

large sizes of work-in-process, • not finished goods — the psychological message

is that you’ve created a bunch of unfinished stuff, • further burdening the team with thoughts of “ we

have so much more to do.”

Kaizen

Kaizen is small improvements and a change for better. It must be accompanied by change of method.

Kaizen

• human resources are the most important company asset

• process must evolve by gradual improvement rather than radical changes

• improvement must be based on evaluation of process performance

Kaizen

• The cycle of kaizen activity can be defined as:

• Standardize an operation

• Measure the standardized operation (find cycle time and amount of in-process inventory)

• Innovate to meet requirements and increase productivity

• Standardize the new, improved operations

• Continue cycle

• The five main elements of kaizen

• Teamwork

• Personal discipline

• Improved morale

• Quality circles

• Suggestions for improvement

• DMIAC cycle :

• DMAIC is used for projects aimed at improving an existing business process.

• DMAIC

• The DMAIC project methodology has five phases:

• Define the problem, the voice of the customer, and the project goals, specifically.

• Measure key aspects of the current process and collect relevant data.

• Analyze the data to investigate and verify cause-and-effect relationships.

• Improve the current process based upon data analysis using techniques such as poka yoke or mistake proofing.

• Control the future state process to ensure that any deviations from target are corrected before they result in defects.

• Brainstorming is a group creativity technique designed to generate a large number of ideas for the solution of a problem.

• Concept of Rapid Prototyping:

• Rapid prototyping is the automatic construction of physical objects using additive manufacturing technology

• The use of additive manufacturing for rapid prototyping takes virtual designs from computer aided design (CAD) or animation modeling software, transforms them into thin, virtual, horizontal cross-sections and then creates successive layers until the model is complete.

Flexible manufacturing system

• manufacturing system in which there is some amount of flexibility that allows the system to react in the case of changes, whether predicted or unpredicted.

• This flexibility is considered to fall into two categories.

• The first category, machine flexibility, covers the system's ability to be changed to produce new product types, and ability to change the order of operations executed on a part.

• The second category is called routing flexibility, which consists of the ability to use multiple machines to perform the same operation on a part, as well as the system's ability to absorb large-scale changes, such as in volume, capacity, or capability.