1.1c: Physiological Factors

1.1c Physiological Factors
Essential idea: Designers consider physiological factors to ensure products meet ergonomic needs. Designers study physical characteristics to optimize the user's safety, health, comfort, and performance.

Physiological factor data
Physiological factor data is available to designers and collected to optimize the user's safety, health, comfort, and performance. Human factor data related to physical characteristics used to optimize the mentioned user characteristics.

A recap on human factor design - it considers the:

• effectiveness (completeness and accuracy)
• efficiency (speed and effort)
• engagement (pleasantness and satisfaction)
• error tolerance (error prevention and error recovery)
• learnability (predictability and consistency)

it also considers which activities can be caried out and how human values quality of life, improved safety, reduced fatigue and stress, increased comfort levels and job satisfaction and are enhanced. 

As human beings, we get used to the way things are really fast. But for designers, the way thing are is an opportunity to make things better and improve the human condition.

Physiological Factors

How is physiological factor data collected?

Using a wide range of methods, such as performance testing, user trials and observations, collection of anthropometric data, and etc.

Comfort and fatigue

Comfort: How pleasing it feels to use a product, is one of the first things a human will notice. If something is not pleasant to the touch, people will not want to touch it or ultimately use or operate it. Comfort is of primary concern to the designers. It determines how effective a design is and how well a human can interact with a product.

Physical comfort: Designers need to find innovative ways to increase the utility of a product. Making an item intuitive and comfortable to use will ensure its success in the marketplace. Physical comfort while using an item increases its utility.

Psychological comfort: Comfort in the human-machine interface is found in feedback. You have preconceived notions of certain things. A quality product should feel like it is made out of quality materials. If it is lightweight and flimsy you will not feel that comfortable using it.

Fatigue: a person's sense of physical or psychological tiredness that inform decisions, and can affect a person's performance. Fatigue is a consequence of some discomfort experienced by the user and can lead to a loss in productivity, loss in quality of outcome and a perception that the product has been poorly designed.

Biomechanics
Biomechanics relates to the mechanics of living organisms and includes research into the operation of muscles, joints, and tendons. Biomechanics in human factor design deals with four key criteria:

1. Force - Excessive impact jolts the user's joints and causes the muscles to tense in response.
2. Repetition - Many work tasks and cycles are repetitive in nature, and are frequently controlled by hourly or daily production targets and work processes. High task repetition, when combined with other risk factors such as high force and/or awkward postures, can contribute to the formation of musculoskeletal disorder (MSD). A job is considered to be highly repetitive if the cycle time is 30 seconds or less.
3. Duration - Refers to continuous muscular effort. Even small exertions continuously held are as stressful to the human tissues.
4. Posture - Posture refers to "the carriage of the body as a whole, the attitude of the body, or the position of the arms and the legs". It is the position in which you could hold your body upright against gravity while standing.

The importance of biomechanics to the design of different products considering muscle strength, age of user, user interface (surface texture,  handle size, etc) and torque.

- In a kitchen: viewing distances, pulling strength, lifting strength and turning strength.

- In a can opener, valve wheel, corkscrew, door handle, jam jar lid – torque becomes important.

1.1b: Psychological Factors

1.1b
Psychological Factors

Human beings vary psychologically in complex ways. Any attempt by designers to classify people into groups merely results in a statement of broad principles that may or may not be relevant to the individual. Design permeates every aspect of human experience and data pertaining to what cannot be seen such as touch, taste, and smell are often expressions of opinion rather than checkable fact.

The analysis of the human information processing system requires a designer to critically analyse a range of causes and effects to identify where a potential breakdown could occur and the effect it may have.

Methods of Collecting Psychological Data

Nominal Scales

Nominal scales are used for labelling variables without any quantitative value - they are simply named or labelled. All of these scales are mutually exclusive in the sense that there is no overlap and none of them have any numerical significance.

Example of Nominal Scale

Interval Scales

Interval scales are numeric scales in which we know not only the order, but the exact differences between the values. The classic example of an interval scale is Celsius temperature because the difference between each value is the same. 

Interval Scale

Ordinal Scales

Ordinal scales place an importance on the order of the values on a scale. They are typically measures of non-numeric concepts like satisfaction, happiness, discomfort, etc.

Example of Ordinal Scale

Ratio Scales

Ratio scales tell us the order, the exact value between units, and they also have an absolute zero - which allows for a wide range of both descriptive and inferential statistics to be applied.

Ratio Scale

Methods of Collecting Psychological Factor Data

• Interviews

An interview involves asking people questions to find out about their experiences and attitudes. One problem of interviewing people is the concern of participants to tell the interviewer what they think is socially acceptable or desirable.

• Surveys or questionnaires

These require subjects to read questions and mark their answers. Some psychologists observe behavior and mental processes by administering standardized tests.

• Observation
• Standardised tests
• Case Studies

10.4: Quality Management

10.4
Quality Management
Essential Idea: Quality management focuses on producing products of consistent required quality.

Quality control (QC) [process]
Quality control: Tolerances (an acceptable amount of defect) are defined at the design stage of the product. Parts not within tolerance need to be reworked or scrapped. Continuous monitoring ensures that machines perform to the predetermined standard/quality.

Quality control at the source eliminates waste from defects as the workers are responsible for the quality of work they do.

Statistical process control (SPC)
This is a quality control tool that uses statistical methods to ensure that a process operates at its most efficient. This is achieved through measuring aspects of a component to ensure that it meets the required standard throughout its production in order to eliminate waste.



Real time SPC contributes and assists with:

• Reducing costs
• Improving productivity
• Decision making in real time
• Reducing waste
• Reducing variability in outcome
• Discovering abnormalities
• Speeding up process changes

Statistical Process Control Charts:

Quality assurance (QA) [product]

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. 

Quality assurance is a way of preventing mistakes or defects in manufactured products and avoiding problems when delivering solutions or services to customers. Defect prevention in quality assurance differs subtly from defect detection and rejection in quality control, and has been referred to as a shift left as it focuses on quality earlier in the process.

Quality Assurance Framework

The Differences between QA, QC and SPC

QA is process oriented while QC is product oriented. QA deals in developing processes and systems that align with Quality Management. QC on the other hand deals with monitoring products.

For example, a QA engineer would develop a quality plan based on customer requirements and a QC engineer would monitor and ensure that all requirements of the quality plan are met during manufacturing. The QC engineer would only focus on making sure the product meets the requirements of the quality plan as set by the QA.

QA is the part of QM focused on providing confidence that quality requirements will be fulfilled. 

QC is the part of QM focused on fulfilling quality requirements. 

Differences between QC and QA

10.3: Computer Integrated Manufacturing

10.3
Computer Integrated Manufacturing
Essential Idea: Computer-integrated manufacturing uses computers to automatically monitor and control the entire production of a product.

Computer integrated manufacture (CIM) takes the concept of integration of separate manufacturing technologies and combines these with all aspects of a company's operations, not just those that are directly involved in the manufacture/

Under a CIM system, all teams can share the same information and easily communicate with one another. A CIM system uses computer networks to integrate the processing of production and business information with manufacturing operations to create cooperative and smooth-running production lines.

Elements of CIM: design, planning, purchasing, cost accounting, inventory control, distribution

DESIGN

• In a CIM system this is accomplished by a design department through computer aided design while considering the product requirements. 
• When design is completed it is tested or functions simulated on a screen before a prototype is made
• Prototypes are maid using CIM machines
• The design process creates the database required to manufacture the part

PLANNING

• Planning department takes the design on the computer system and database established by the design department and enriches it with production data to produce a plan for the most efficient method of production of the product
• Involves subsystems dealing with materials, facility, process, tools, manpower, capacity, scheduling, outsourcing, assembly, inspection, logistics and others.

PURCHASING

• The purchase department orders the necessary materials to manufacture the product, keeping cost to a minimum
• Just in time (JIT) philosophy is applied
• Computer system is used to purchase orders and follow up, ensure quality in the production process of the vendor, log the received items, and more.

COST ACCOUNTING 

• The finance department uses a computer system to deal with the financial resources of a company 
• Such factors of cost accounting include:
• Inventory valuation
• Cost of goods sold valuation
• Constraint analysis
• Margin analysis
• Variance analysis
• Budgeting

INVENTORY CONTROL

• Computerized inventory control systems make it possible to integrate the various functional subsystems that are a part of the inventory management into a single cohesive system.
• An inventory control system encompasses all aspects of managing a company's inventories including:
• Purchasing 
• Shipping 
• Receiving
• tracking
• Warehousing and storage
• Turnover
• Reordering

DISTRIBUTION

• Distribution (or warehousing uses the computer system to aid in organizing the storage and retrieval of raw materials, components, finished goods as well as the shipment of items
• Storage is automated using computer controlled vehicles that move the finished product from the manufacturing area to storage (and keeps track of the products)
• Logistics and supply chain management assume great importance