Quality and Variation in Manufacturing

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Questions and Answers

What is the term used to describe the 'noise' of the system?

Accuracy

Random variation (correct)

Resolution

Repeatability

In the context of Injection Molding, what is the relationship between molecular weight of polymer and?

Injection pressure

Viscosity (correct)

Tool life

Surface roughness

What is the term used to describe the difference between the measured and true value?

Sensitivity

Resolution

Repeatability

Accuracy (correct)

In the context of Machining, what is the relationship between depth of cut and?

Surface roughness Signup and view all the answers

What is the term used to describe the minimum increment that can be measured?

Resolution Signup and view all the answers

What is the term used to describe the ability to tell the same story many times?

Repeatability Signup and view all the answers

In the context of Injection Molding, what is the relationship between injection pressure and?

Accuracy Signup and view all the answers

What is the term used to describe the ability to tell the truth?

Accuracy Signup and view all the answers

In the context of Machining, what is the relationship between tool life and?

Workpiece deformation Signup and view all the answers

What is the term used to describe the difference between consecutive measurements intended to be identical?

Repeatability Signup and view all the answers

What is the primary application of the normal distribution in manufacturing?

Quality control Signup and view all the answers

What is the mean lifetime of car tires in the example given?

80,000 km Signup and view all the answers

What is the definition of the lognormal distribution?

The logarithm of x is distributed normally Signup and view all the answers

What is a source of variation in the manufacturing process?

All of the above Signup and view all the answers

What is an example of a systematic variation in the manufacturing process?

Tool wear and tear Signup and view all the answers

What is the purpose of the normal probability density function?

To model variation in manufacturing processes Signup and view all the answers

What is the standard deviation of the car tire lifetime distribution?

4,000 km Signup and view all the answers

What is the primary application of the lognormal distribution?

Modeling metal powder distributions for 3D printing Signup and view all the answers

What is the purpose of the cumulative distribution function (CDF)?

To find the probability of a specific value Signup and view all the answers

What is an example of a factor that affects process variations?

All of the above Signup and view all the answers

What is the primary objective of measuring variation in a process?

To quantify the variation statistically and maintain process control Signup and view all the answers

What is the characteristic of a normal distribution?

It is a probability distribution of the occurrence of a data Signup and view all the answers

What is the term for the allowable or permissible limit of variation of a process?

Tolerance Signup and view all the answers

What is the defect rate per million in the car body build variation?

3.4 defects per million Signup and view all the answers

What is the purpose of understanding the principle of measurement?

To understand the measurement of variation from a process Signup and view all the answers

What is the primary role of customers in variation and quality?

To perceive the quality of the product Signup and view all the answers

What is the normal distribution also known as?

Bell curve Signup and view all the answers

What is the purpose of minimizing variations in processes?

To improve the quality of the product Signup and view all the answers

What is the term for the change in outcome of a process?

Variation Signup and view all the answers

What is the primary objective of quantifying the variation statistically?

To maintain process control Signup and view all the answers

What is the primary source of variation that affects the accuracy of a manufacturing process?

Random variation Signup and view all the answers

What is the primary reason for measuring variation in a process?

To quantify the variation statistically Signup and view all the answers

Which of the following is a principle of measurement that determines the ability to distinguish between different values?

Resolution Signup and view all the answers

What is the term used to describe the ability of a product or service to consistently meet customer needs?

Quality Signup and view all the answers

What is the relationship between the molecular weight of a polymer and its accuracy in injection molding?

Higher molecular weight results in higher accuracy Signup and view all the answers

What is the purpose of understanding the normal distribution in manufacturing?

To understand the measurement of variation from a process Signup and view all the answers

What is the primary purpose of understanding the principles of measurement in manufacturing?

To improve the accuracy of measurements Signup and view all the answers

What is the primary objective of customers in variation and quality?

To ensure their perceived 'good quality' is related to the specifications of the product Signup and view all the answers

What is the term used to describe the difference between the measured and true values of a process?

Error Signup and view all the answers

What is the term used to describe the change in outcome of a process?

Variation Signup and view all the answers

What is the primary objective of quantifying the variation in a process statistically?

To understand the behavior of the process Signup and view all the answers

What is the purpose of minimizing variations in processes?

To ensure the product meets customer needs Signup and view all the answers

What is the relationship between the depth of cut and surface roughness in machining?

Higher depth of cut results in higher surface roughness Signup and view all the answers

What is the term used to describe the ability of a process to produce consistent results?

Repeatability Signup and view all the answers

What is the primary role of the normal distribution in manufacturing?

To understand the measurement of variation from a process Signup and view all the answers

In manufacturing, the primary application of the normal distribution is to:

Control the quality of production processes Signup and view all the answers

What is the term used to describe the allowable or permissible limit of variation of a process?

Tolerance Signup and view all the answers

What is the primary application of understanding the principles of variation in manufacturing?

To improve the quality of products Signup and view all the answers

What is the purpose of understanding the principle of measurement in manufacturing?

To understand the measurement of variation from a process Signup and view all the answers

What is the fraction of tires that can be expected to wear out within ±4,000 km of the average?

About 68% Signup and view all the answers

What is the term used to describe the ability of a process to differentiate between different values?

Resolution Signup and view all the answers

Which of the following is an example of an environmental factor that affects process variations?

Temperature Signup and view all the answers

What is the defect rate per million in the car body build variation?

3.4 defects per million Signup and view all the answers

What is the term used to describe the ability of a process to produce consistent results?

Capability Signup and view all the answers

Which of the following is a characteristic of a normal distribution?

It is symmetrical about the mean Signup and view all the answers

What is the primary objective of understanding the principle of measurement?

To determine the accuracy of a measurement Signup and view all the answers

Which of the following is an example of a systematic variation?

Tool wear Signup and view all the answers

What is the purpose of the cumulative distribution function (CDF)?

To determine the probability of a value exceeding a certain threshold Signup and view all the answers

Which of the following is a consequence of minimizing variations in processes?

Improved product quality Signup and view all the answers

What is the relationship between the logarithm of x and the normal distribution in a lognormal distribution?

The logarithm of x is distributed normally Signup and view all the answers

Study Notes

Variation and Quality

Variation refers to the change in outcome of a process, while quality is the ability of a product or service to consistently meet customer needs.
Tolerance is the allowable or permissible limit of variation of a process.

Measure of Quality

Quality is measured by how well a product or service meets customer needs, which should be related to the specifications of the product.
Quantifying variation statistically is important to understand the measurement of variation from a process.

Normal Distribution

A normal distribution helps quantify the outcome of a process and understand the measurement of variation from a process.
It is a probability distribution of the occurrence of data, and naturally occurring phenomena tend to approximate the normal distribution.
In manufacturing, normal distribution is a means of quality control.

Normal Distribution Examples

Car tires can be modeled using a normal distribution, with a mean lifetime and standard deviation.
The normal distribution can be used to calculate the fraction of tires that can be expected to wear out within a certain range.

Other Types of Distributions

Lognormal distribution: the logarithm of x is distributed normally, used in applications such as metal powder for 3D printing.
Lognormal distribution is used when the data is not symmetric around the mean.

Process Sensitivity

Process sensitivity refers to the factors that affect process variations, including process, material, equipment, operator, environment, and measurement.

Factors Affecting Process Variations

Process: inherent capability, change of settings
Material: raw material variation, defects
Equipment: tool wear, equipment maintenance or calibration
Operator: procedure, distraction, fatigue
Environment: temperature, humidity, vibration
Measurement: capability of the tool (resolution), need for calibration

Types of Variation

Systematic ("special cause") variation: influences of process parameters or external disturbances that can be isolated and possibly predicted or removed.
Random ("common cause") variation: caused by uncontrollable factors that result in a steady but random distribution of output around the average of the data.

Variation and Quality

Variation refers to the change in outcome of a process
Quality is the ability of a product or service to consistently meet customer needs
Tolerance is the allowable or permissible limit of variation of a process

Measure of Quality

LEGO bricks: Special Bricks and Classic Bricks demonstrate variation in manufacturing
Gillette Razors: variation in manufacturing process affects quality
Car Body Build Variation: 6 standard deviations from the mean result in 3.4 defects per million

What Do We Need to Know?

Customers' needs and perceived "good quality" should be related to product specifications
Quantify variation statistically
Identify factors that cause variations in processes and minimize them as needed
Monitor variation and maintain process control

Normal Distribution

Helps quantify the outcome of a process
Helps understand measurement of variation from process
Bell curve: probability distribution of the occurrence of data
Naturally occurring phenomena tend to approximate the normal distribution
In manufacturing, normal distribution is a means of quality control

Lognormal Distribution

Logarithm of x is distributed normally
Example: metal powder for 3D printing (Ti6Al4V) with specification of 15-45 um

Process Sensitivity

Factors that affect process variations:
- Process: inherent capability, change of settings
- Material: raw material variation, defects
- Equipment: tool wear, equipment maintenance or calibration
- Operator: procedure, distraction, fatigue
- Environment: temperature, humidity, vibration
- Measurement: capability of the tool (resolution), need for calibration

Machine, Tool, and Workpiece

Factors that affect variation in machining and injection molding processes

Principles of Measurement

Accuracy: difference between measured and true value
Repeatability: difference between consecutive measurements intended to be identical
Resolution: minimum increment that can be measured

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Description

Discover the principles of quality and variation in manufacturing processes, including tolerance and statistical measurement. Learn how to quantify variation and understand the importance of meeting customer needs.