10.4 Quality Management
Essential idea:
Quality management focuses on producing products of consistent required quality.
Nature and Aims of Design
Nature of Design
Designers should ensure that the quality of products is consistent through development of detailed manufacturing requirements. They also need to focus on the means to achieve it. The importance of quality management through quality control (QC), statistical process control (SPC) and quality assurance (QA) reduces the potential waste of resources.
Aims
Aim 3: The implementation of quality management strategies requires a critical and complete understanding of the needs of a product. To ensure efficiency and efficacy, these measures need to be designed into the product and its production system.
Guidance
As DP Design Technology student you should:
Concepts & Principles
Quality Control
Statistical Process Control
Quality Assurance
Guidance
How QC at source eliminates waste and defects
How continuous monitoring ensures that machines perform to the predetermined standard/quality
How QC, SPC and QA contribute to quality management
The differences between QC, SPC and QA
Concepts and Principles
Quality Control, Statistical Process Control, and Quality Assurance are part of Quality Management.
Key Vocabulary & Terms
Tolerance: The allowable amount of variation within a particular quality. i.e. The weight tolerance for a high performance bicycle frame might be +/- 100 grams from its set weight of 1850 grams.
Destructive Testing: Testing a product or part that destroys or physically alters the part. These are usually mechanical properties such as heat resistance, compression, toughness.
Non-destructive Testing: Testing a product or part that measure physical properties. The product itself is not damage or changed in the process: Weighing, checking color, confirming dimensions.
Inspection: The checking of qualities at difference stances of the production process.
Benefits of Quality Management
Quality Control
Statistical Process Control (SPC)
Quality Assurance (QA)
The goal of quality control is to produce the same part over and over again with a minimum or no waste.
Quality Control begins with the identification of Tolerances. These are the allowable variations in the qualities of a part. Typically tolerance are identified at the design stage. However, it is necessary at this stage to know the degree of tolerance the machine that will produce the part can operate at. Different machines and brands operate at different tolerances. Knowing the capability of the machine and designing tor it can ensure that tolerances are at an attainable and acceptable level.
Quality control at the source eliminates waste from defects as workers are responsible for the quality of the work they do.
QC examples include
Parts that do not fall within the tolerance range are either reworked or discarded. A CIM system continuously monitors machines and production and ensures machines are operating at tolerance, in addition to identifying when a machine needs maintenance or recalibration.
In the chart above shows testing of various parts. The upper (USL) and lower specifications (LSL) are defined by the purple lines. The green dotted line is the Upper (UCL)and Lower Control limits (LCL). Manufacturers will typically set a range within the LSL and USL as the tolerance.
The dots represent the measurement of individual items. Manufacturers will typically calibrate the machine to achieve the mean of these data points, while allowing for tolerances that fit between the UCL and LCL). Depending on the type of product, the range between UCL and LCL will vary.
SPC is a statistical tool that ensures a process operates efficiently. This involves measuring aspects of a product or process in order to identify inefficiencies and opportunities for improvement.
The goal of SPC is to reduce waste, increase productivity, and discover abnormalities in a process in order to facilitate timely decision making.
SPC examples include:
Airlines collecting data on flight delays, lost luggage, customer satisfaction, waiting time at check-in in order to identify inefficiencies
Car manufacturers collecting data on types and frequency of repairs, rate of wear and tear on parts such as brake pads, and data from car accidents and crashes in order to improve quality and safety of the automobile.
The goal of QA is to reduce or avoid errors or defective products being delivered to the customer.
This covers all activities from design to documentation. It also includes the regulation of the quality of raw materials, assemblies, products and components, services related to production, and management and inspection processes. The goal of QA is to set standards of quality for all stages, beginning with the raw materials, throughout the delivery of the product to the customer.
QA focuses on processes and procedures that ensure quality, as opposed to checking to make sure a manufactured product is within tolerance.
QA examples include:
The testing of raw materials when they arrive at the manufacturer to ensure they meet the requirements and quality needed to manufacture a product. By identifying inferior materials earlier in the producing stage, costly errors, waste, and downtime can be avoided later on.
