Tolerance Design-容差设计
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Welcome
Have you ever been under pressure to do any of the following? •Obtain design and manufacturing agreement on tolerances •Recommend expenditures to improve a manufacturing process •Balance functionality and cost •Reduce cost while maintaining quality If you have, then you know that such decisions are difficult to make and often there are "gray areas" where the customer benefit is not quantifiable. This course gives you the tools to make such decisions more methodically and within a more rational framework. The result will be better decisions for the Company and the customer. An additional result will be the increasingly strategic role and value of you, the engineer.
Lesson 1. Introduction and Definitions
Lesson Objectives
At the completion of this lesson, you will be able to: •Define Tolerance Design •Define Tolerancing •Define Tolerance Stack-Up •Define Variation Simulation Analysis (VSA) •Define Geometric Dimensioning & Tolerancing (GD&T) •Define the need for Tolerance Design and Tolerancing
Tolerancing Definition
Tolerancing is the process of setting boundary limit values for manufactured dimensions, material properties and other characteristics/responses. In the context of Tolerance Design, the purpose of Tolerancing is to set the level at which to adjust, repair or scrap a manufactured item before shipping it. This level is defined as the Manufacturing Tolerance. It is based on the product variability that will cause the average customer to return the item for repair. You can think of Tolerancing as a tool for answering the question: Based on the dissatisfaction and/or repair cost to the customer, should we ship a manufactured item "as is" or should we adjust, repair or scrap it? On the following screen is an example of Tolerancing.
Welcome, continued
This course has four sections: •Section 1. Tolerance Design and Tolerancing Fundamentals •Section 2. Quality Loss Function (QLF) for One Unit and Tolerancing •Section 3. QLF for More Than One Unit •Section 4. Tolerance Design Throughout this course, you will perform calculations. You can access a calculator by: 1.Clicking the Windows Start button 2.Selecting All Programs 3.Selecting Accessories 4.Selecting Calculator
Tolerance Design Definition
Tolerance Design is a method to balance the cost to upgrade a manufacturing process or product/service performance with the benefit of reduced variability in the output of that process/product/service. In other words, it is a method for balancing cost and quality. The benefit is quantified by the reduction of loss to the consumer. The purpose of Tolerance Design is to reduce variability. Let's look at an example of Tolerance Design.
Need for Definitions
This course will focus on Tolerance Design and Tolerancing. These methods could be confused with three other methods, Tolerance Stack-Up, Variation Simulation Analysis (VSA) and Geometric Dimensioning & Tolerancing (GD&T). So, we will begin this course with high-level definitions of the following methods to differentiate them: •Tolerance Design •Tolerancing •Tolerance Stack-Up •VSA •GD&T
Tolerance Stack-Up and VSA
A simple Tolerance Stack-Up is typically an analysis of system clearance based on geometry and accumulation of component variabilities to ensure parts will fit and assemble. In statistical terms, this is a process of uncertainty propagation from the component level to the system level. Although it can be used for identifying which components have the greatest effect on system variability, it is not a method necessarily focused on reducing system variability like Tolerance Design nor does it use the notion of quadratic Consumer Loss to set Manufacturing Tolerance. Tolerance Stack-Up will not be discussed further in this course. Likewise, Variation Simulation Analysis (VSA) will not be discussed in depth in this course. VSA, also known as Dimensional Variation Analysis (DVA), is a Tolerance StackUp strategy for complex systems. VSA uses Monte Carlo sampling of a large number of individual, randomly-selected component values to determine the composite system variation. As with any Tolerance Stack-Up, VSA can determine which components have the most effect on system variation. In contrast to the use of Monte Carlo (i.e., random) sampling, Tolerance Design uses orthogonal arrays with a small, balanced set of component values. Orthogonal arrays require far fewer experiments, thereby improving computation efficiency. Another related method is Geometric Dimensioning & Tolerancing (GD&T), which is defined on the next screen.
Tolerance Design Example
Suppose that o reduce the vehicle-to-vehicle variability in the windshield wiper pattern travel with the benefit to the consumer. You can use Tolerance Design to identify which wiper linkage component variabilities have the greatest effect on the overall wiper pattern variability. You can then make sensible judgments on whether to upgrade the manufacturing capability of selected wiper linkage components based on the cost and the benefit to the consumer population. Now, let's define the second major topic in this course: Tolerancing.
Tolerancing Example
Suppose your company is manufacturing round shafts for starter motors. With the proper knowledge of how shaft roundness affects motor function, you can use Tolerancing to determine at what out-of-round condition you should adjust, repair or scrap the shafts before assembling them into the starter motor assemblies and shipping them for assembly into vehicles. To confirm your understanding of Tolerance Design and Tolerancing, continue to the next screen.
Have you ever been under pressure to do any of the following? •Obtain design and manufacturing agreement on tolerances •Recommend expenditures to improve a manufacturing process •Balance functionality and cost •Reduce cost while maintaining quality If you have, then you know that such decisions are difficult to make and often there are "gray areas" where the customer benefit is not quantifiable. This course gives you the tools to make such decisions more methodically and within a more rational framework. The result will be better decisions for the Company and the customer. An additional result will be the increasingly strategic role and value of you, the engineer.
Lesson 1. Introduction and Definitions
Lesson Objectives
At the completion of this lesson, you will be able to: •Define Tolerance Design •Define Tolerancing •Define Tolerance Stack-Up •Define Variation Simulation Analysis (VSA) •Define Geometric Dimensioning & Tolerancing (GD&T) •Define the need for Tolerance Design and Tolerancing
Tolerancing Definition
Tolerancing is the process of setting boundary limit values for manufactured dimensions, material properties and other characteristics/responses. In the context of Tolerance Design, the purpose of Tolerancing is to set the level at which to adjust, repair or scrap a manufactured item before shipping it. This level is defined as the Manufacturing Tolerance. It is based on the product variability that will cause the average customer to return the item for repair. You can think of Tolerancing as a tool for answering the question: Based on the dissatisfaction and/or repair cost to the customer, should we ship a manufactured item "as is" or should we adjust, repair or scrap it? On the following screen is an example of Tolerancing.
Welcome, continued
This course has four sections: •Section 1. Tolerance Design and Tolerancing Fundamentals •Section 2. Quality Loss Function (QLF) for One Unit and Tolerancing •Section 3. QLF for More Than One Unit •Section 4. Tolerance Design Throughout this course, you will perform calculations. You can access a calculator by: 1.Clicking the Windows Start button 2.Selecting All Programs 3.Selecting Accessories 4.Selecting Calculator
Tolerance Design Definition
Tolerance Design is a method to balance the cost to upgrade a manufacturing process or product/service performance with the benefit of reduced variability in the output of that process/product/service. In other words, it is a method for balancing cost and quality. The benefit is quantified by the reduction of loss to the consumer. The purpose of Tolerance Design is to reduce variability. Let's look at an example of Tolerance Design.
Need for Definitions
This course will focus on Tolerance Design and Tolerancing. These methods could be confused with three other methods, Tolerance Stack-Up, Variation Simulation Analysis (VSA) and Geometric Dimensioning & Tolerancing (GD&T). So, we will begin this course with high-level definitions of the following methods to differentiate them: •Tolerance Design •Tolerancing •Tolerance Stack-Up •VSA •GD&T
Tolerance Stack-Up and VSA
A simple Tolerance Stack-Up is typically an analysis of system clearance based on geometry and accumulation of component variabilities to ensure parts will fit and assemble. In statistical terms, this is a process of uncertainty propagation from the component level to the system level. Although it can be used for identifying which components have the greatest effect on system variability, it is not a method necessarily focused on reducing system variability like Tolerance Design nor does it use the notion of quadratic Consumer Loss to set Manufacturing Tolerance. Tolerance Stack-Up will not be discussed further in this course. Likewise, Variation Simulation Analysis (VSA) will not be discussed in depth in this course. VSA, also known as Dimensional Variation Analysis (DVA), is a Tolerance StackUp strategy for complex systems. VSA uses Monte Carlo sampling of a large number of individual, randomly-selected component values to determine the composite system variation. As with any Tolerance Stack-Up, VSA can determine which components have the most effect on system variation. In contrast to the use of Monte Carlo (i.e., random) sampling, Tolerance Design uses orthogonal arrays with a small, balanced set of component values. Orthogonal arrays require far fewer experiments, thereby improving computation efficiency. Another related method is Geometric Dimensioning & Tolerancing (GD&T), which is defined on the next screen.
Tolerance Design Example
Suppose that o reduce the vehicle-to-vehicle variability in the windshield wiper pattern travel with the benefit to the consumer. You can use Tolerance Design to identify which wiper linkage component variabilities have the greatest effect on the overall wiper pattern variability. You can then make sensible judgments on whether to upgrade the manufacturing capability of selected wiper linkage components based on the cost and the benefit to the consumer population. Now, let's define the second major topic in this course: Tolerancing.
Tolerancing Example
Suppose your company is manufacturing round shafts for starter motors. With the proper knowledge of how shaft roundness affects motor function, you can use Tolerancing to determine at what out-of-round condition you should adjust, repair or scrap the shafts before assembling them into the starter motor assemblies and shipping them for assembly into vehicles. To confirm your understanding of Tolerance Design and Tolerancing, continue to the next screen.