Production Tool Design: Introduction
TAUFIK Faculty of Manufacturing Engineering UTeM Week 1
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Learning Objectives
1.
2.
3. 4.
The objectives of this chapter are to : List the objectives of tool design. Explain the types of tools. Apply the design process of tool design. Describe the functions of a tool designers.
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Tool Design in Manufacturing
To be competitive in manufacturing requires the success of concurrent engineering. As one of the concurrent team member, tool design member involved in product design and production where their knowledge of fixtures and manufacturing will result in fewer design error.
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Tool Design
A process of designing and developing the tools, methods and techniques necessary to improve manufacturing efficiency and productivity.
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Tool Designer and Responsibility
Provide simple, easy-to-operate tools for maximum efficiency. Reduce manufacturing expenses by producing parts at the lowest possible cost. Design tools that consistently produce parts of high quality. Increase the rate of production with existing machine tools. Design the tool to make it foolproof and to prevent improper use. Select materials that will give adequate tool life. Provide protection in the design of the tools for maximum safety of the operator.
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Objective of Tool Design
Production Tool is an important component of manufacturing which contributes to - maintain production quality (Q) - lower production cost (C) - reduce production lead time (D) significantly.
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But how.?
Production Tool could help to: -Provide simple, easy-to-operate tools for maximum efficiency. -Reduce manufacturing expenses by producing parts at the lowest possible cost. -Design tools that consistently produce parts of high quality. -Increase the rate of production with existing machine tools. -Design the tool to make it foolproof and to prevent improper use. -Select materials that will give adequate tool life. -Provide protection in the design of the tools for maximum safety.
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Production Tool in Mass Production
Mass production aims at high productivity : -to reduce unit cost and interchangeability -to facilities easy assembly.
This necessitates: -production tool to increase the rate of manufacture -inspection device to speed up inspection procedure.
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Production Tool
Are generally work holders with/without tool guiding/setting arrangement. These are called Jigs and Fixtures
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Types of Tools
a. Material Cutting Tools
The selection of cutting tools material for particular application is among the most important factors in production tooling, as is the selection of production tooling materials for holding, supporting, and clamping the workpiece must be maintained.
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Types of Material Cutting Tools
Tool steels (principal materials), Tool and Die Steel (typical hardness RC40~60)
W, Water-Hardening Tool-Steels O, Oil-Hardening Tool-Steels A, Air-Hardening Medium Alloy Die-Steels D, High-Carbon High-Chromium Die Steels S, Shock-Resisting Tool-Steels H, Hot-Work Die Steels P, Low-Carbon Mold Steels T and M, Tungsten and Molydenum High-Speed Steels L, Low-Alloy Tool-Steels F, Carbon-Tungsten Finishing Steels
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Material Used
High Speed Steels (HSS)
Contains 18% tungsten (toughness & cutting strength), 4.3% chromium (hardenability & resistance), 1% vandadium (retention)
Air or oil hardened to RC 64-65 (cutting tools), i.e. drills, reamers and cutters
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Material used (2)
Die Steels
For high temperature work like forging, casting and extrusion For bushing and locator
Carbon Steels
Collet Steels (Spring Steels)
Tempered to RC 47 hardness
For press rams
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High Tensile Steel
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Material Used (3)
Oil Hardening Non-Shrinking Tool Steel (OHNS)
For fine parts i.e. taps, hand reamers, milling cutters. For part only local hardness on small wearing surface For parts not subjected to much wear
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Case Hardening Steels
Mild Steel
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Material Used (4)
Cast Iron
For used widely in milling fixtures Combine steel strength & casting shape For soft lining for clamps (prevent damage) For replaceable nuts in screw (time consume & costly)
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Steel Casting
Nylon and Fiber
Phosphor Bronze
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Type of Tools
b. Workholding Devices
Workholding Devices means all devices that hold, grip, or chuck a workpiece in a prescribed manner of firmness and location, to perform on it a manufacturing operation.).
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Type of Tools
c. Pressworking Tools
The purpose production tooling in term of pressworking tools are to hold and clamp of the workpiece during pressworking processes. The purpose production tooling in bending, forming and drawing dies are to support, hold, and clamp of the workpiece during bending, forming and drawing dies processes in order to develop a high level of the precise tolerances.
d. Bending, Forming and Drawing Dies
e. Tool Design for Inspection and Gaging
Every dimensions of every work piece must be specified as being between two limits.
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Work Holding Devices Definition
Work holding devices include all devices that hold, grip or chuck a workpiece to perform a manufacturing operation. The holding force may be applied mechanically, electrically, hydraulically or pneumatically.
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Principles of work holding
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Typical Workholding Devices
Vise: it is an elementary workholder (Figure a). The clamping force is applied using a screw mechanism. The holding force is applied using a lever to exert a torque (T). T = F x a in.lb Where F = human force in lb. a = Lever length in inches. (a) Elementary Workholder (vise)
Vise with hydraulic clamping (Figure b). The holding force is applied using hydraulic pressure that is applied to the vise jaws
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Special Workholding Devices Fixtures
Fixtures Fixtures are usually designed for a particular work pieces. The function of a fixture is to hold, and clamp the workpiece in a precise position (Figure a) Jigs A jig is a fixture that guides the tool in addition to holding the workpiece in a precise position (Figure b)
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Principles of Workholding
The objective of work holding is to position or locate a workpiece in definite relation to the cutting tool, and
must clamp it with a proper force in order to withstand the cutting forces while maintaining that precise position.
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Elements
Locating Elements
Position work piece accurately Hold work piece securely. Aid guiding of setting of the tools in correct position with respect the work piece
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Clamping Elements
Tool Guiding and Setting Elements
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Design Consideration of Workholders Positive Location
The twelve degree of freedom
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Afixture must be strong to support and hold the workpiece precisely in space to restrict each of the 12 degrees of freedom. Repeatability workpiece should be located in the same position in order to produce parts with precise dimensions. Adequate Clamping Forces Fixtures should provide adequate clamping forces to hold and support the workpiece against all forces subjected to such as weight, centrifugal force, inertial forces, and cutting forces.
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Design Consideration of Workholders
1. Reliability Must maintain the clamping force during operation. Must be easy to maintain and lubricate. 2. Ruggedness Must be able to withstand impact force during operation Must resist abrasion. Easy to maintain and replace worn parts. 3. Design and Construction Ease Use standard parts whenever possible. If possible use modular fixture 4. Low profile Must clear tool path and allow for tool clearance
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Design Consideration of Workholders
5. Workpiece Accommodation Tolerates part variations without sacrificing positive location or other design objectives; e.g. casting or forging workpieces 6. Rapid Easy Operation Easy to load and unload parts to reduce cycle time 7. Freedom of Part Distortion Adequate clamping to avoid part distortion after releasing it. 8. Flexibility Can be used for more than one part such as family of parts Examples: Modular fixtures, programmable fixtures, etc.
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Advantages
Productivity
Eliminate individual marking, positioning, etc Facilitate uniform quality. No need for selective assembly
Interchangeability
Skill Reduction
Simplify locating and clamping of the WP
Scrap <<, easy assembly, saving labor cost
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Cost Reduction
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Inspection Devices
Facilitate Interchangeability, uniformity must be limited, taking into machines capability Certain variations allowed
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Limits and Fits
Largest and Smallest dimension of the shaft (or hole) high and low limit Difference between these limit Tolerance, i.e., permission variation If tolerance allowed only one side of the nominal dimension unilateral 0.02 Example: 250.00 unilateral If tolerance both side bilateral
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Classification of Fits
Running Fit: Push Fit Press Fit Force Fit
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Limits and Fits
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Limits and Fits (2)
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Sample of Fits
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Design Process
Overall Size and Shape of the Part Type and Condition of Material Type of Machining Operation Degree of Accuracy Required Number of Pieces to be Made
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Tooling Drawing
Draw and dimension without crowding views or dimensions Draw only required views Specify surface roughness Tolerances and firs peculiar to tools need special consideration. Stock size for finishing machining operation should be indicated. Notes must be used for heat treatment and other finishing operations should be used Secondary operation should be avoided is possible Avoid use of tight tolerance.
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Tooling Layout (1)
as a tool to explode the part as partial part in order to easy assemble. The actual work of creating on paper the assembly design of equipment or tools for manufacturing processes should be done within the general framework of the following rules:
Lay out the part in an identifying color (red is suggested) Lay out any cutting tools. Indicate all locating requirements for the part.
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Tooling Layout (2)
Indicate all clamping requirements for the part Lay out the details with due consideration to stock sizes, so as to minimize machining requirements. Use full scale in the layout, if at all possible. Indicate the use of standard (purchasable as shelf items) fixture parts whenever possible. Identify each different item/detail.
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Tooling Layout Figure
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Tooling Safety
Safety should be designed into the tooling. More minor injuries resulted from these. Never cut against a clamp because of vibration and tool chatter. Instead parts should be nested against pins in order to take the cutter load. Rigidity and fool proofing should be should always be built into the tooling. Drill jigs should be made large enough to hold without the danger of spinning. All punch presses and air or hydraulically operated tooling to be installed with a double button interlocking protection system.
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Tooling Handle in the Work Place
Tooling handling is to minimize the risk of accidents of tooling-operator contact. The contact can be:
An individual making the contact with the tooling-usually the moving part, because of inattention caused by fatigue, distraction, curiosity, or deliberate chance taking; From the tooling via flying chips, chemical, and hot metal splashes, and circular saw kickbacks, to name a few; Caused by the direct result of a tooling malfunction, including mechanical and electrical failure
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Work piece
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