ERGONOMICS AND ANTHROPOMETRICS

ERGONOMICS:

Ergonomics is the study of the interaction between the human body, products and the surrounding environment. It is a key factor in the design of all products from furniture to handheld gadgets. It is an essential part of the design process. The main objective for ergonomists is to improve consumer's lives by increasing their comfort when using products. When ergonomics is incorporated into industry machinery and tooling it can increase efficiency, productivity and reduce errors/accidents. The principles of ergonomics involve designers understanding how humans interact and with products. The methods of focussing on human performance take either a quantitative approach or a qualitative approach. The quantitative approach related to the physical fit of the human body in relation to speed of performance and workload. The qualitative approach related to the overall comfort experienced by the user. Everyday situations can be hazardous to health by persistently subjecting the human body to positions and situations that are not comfortable. In western countries, musculoskeletal system (e.g lower back pain) and psychological illness (e.g stress) lead to the greatest significance of absenteeism from work. These conditions can be caused by poor quality ergonomic design of equipment. Therefore in the workplace, improved ergonomics can increase productivity.

 

ANTHROPOMETRICS:

Anthropometrics is the use of body measurements to determine the optimum size for products for comfortable and efficient use. Examples of anthropometric data include:

- How far people can reach;

- How much space people need;

- How much force they can exert;

- Height of a person;

- Length of arms/legs etc.

Many production companies use anthropometric data when designing. The designer's aim is to achieve as good an anthropometric match for as many potential consumers as possible.

50th Percentile: the average or most common anthropometric measurements from a sample.
95th Percentile: the upper limiting anthropometric measurement. Designers usually produce  designs for body sized between the 5th and 95th percentile as this takes in the majority of users.






 

 

SUSTAINABILITY

ENVIRONMENTAL LEGISLATION AND REGULATION:

ECOLABEL

• The EU Ecolabel is a voluntary scheme which was established in 1993. Manufacturers are encouraged to label products that have a reduced impact on the environment over their life cycle. European consumers can identify such products with a flower symbol.

PACKAGING DIRECTIVE

• The EU Packaging Directive, introduced in 1994 and amended in 2001, sets targets for the reduction of packaging waste by means of designing out waste in the initial package design, recycling, and re-use. It also sets limits for the amount of toxic metals used in packaging. EU member states have to meet the following targets: by 2008, 60% of all packaging waste is to be recovered and a minimum of 55% of this waste is to be recycled.

ENERGY LABELLING DIRECTIVE

• This EU directive was introduced in 1996. All electrical appliances such as refrigerators and washing machines are labelled with a rating from A to G to indicate their energy use for consumers to refer to when making a purchase. The directive also aims to phase out inefficient appliances.

END-OF-LIFE VEHICLE DIRECTIVE (ELVD)

• This directive was introduced in 2003 to encourage the reuse and recycling of waste from vehicles when they reach the end of their life. It restricts the use of toxic metal in new cars and requires manufacturers to label plastic parts to air recycling. Manufacturers also have to publish information on how to dismantle the vehicles.

WASTE ELECTRICAL AND ELECTRONIC EQUIPMENT DIRECTIVE

• This EU directive also known as the WEEE Directive was implemented in 2006. It encourages manufacturers to develop electrical and electronic products that can be dismantled and the parts reused or recycled. Manufacturers have to include instructions to consumers not to discard the old product but take them to WEEE collection points. The directive also requires manufacturers to arrange collection of WEEE.

RESTRICTION OF HAZARDOUS SUBSTANCES DIRECTIVE (RoSH)

• Introduced in 2006, this EU directive bans the use of some hazardous materials and chemicals such as lead. mercury and cadmium in electrical and electronic equipment. This is to safeguard human health when electrical equipment is disposed of and recycled.

CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH REGULATIONS (COSHH):

• COSHH is a set of HSE (Health and Safety Executive) regulations and guidance for the storage and handling or potentially dangerous materials. The regulations include details of how the materials should be labelled, safely used ad stored to protect employees.

WASTING PROCESSES

Machine wasting :

-          Wasting process, the process of taking something away from a material is called wasting

-          Machine wasting, almost any wasting technique can be mechanised

-          Common machines used for shaping by wasting – lathes, pillar drills, milling machines.

-          Computer Numerical Control (CNC) – CNC machine tools are programmable, automated means of machining components They are a development of a numerical control technique that first appeared in the 1950s which controls the actions of machines by the input of instructions in the form of a code. Drilling machines for drilling, lathes for all turning contouring operations, milling machines, most versatile operations for creating a wide range of complex contours as well as internal and external profiles, laser cutters for engraving and cutting sheet materials.

-          Milling machine involves the movement of the work piece against the rotating cutter, meaning it will be able to cut on its flanks as well as its tips. Used for complex shaping of metal, plastic or wood parts. Has rotating cutter which rotates about the spindle axis, a movable bed to which the material is clamped. The cutting tool remains stationary while the material on the bed moves. 2 forms which refer to the orientation of the spindle, vertical and horizontal.

-          CNC router is a machine which creates objects from various materials. It can be designed on the computer with a cad/cam program, and then cut automatically using a CNC router to produce a finished part, it is accurate and fairly quick.

-          Ultrasonic machining – high frequency electrical signal that is converted into oscillating mechanical motion through electric motors. The high frequency motion causes the cutting tool to expand and contract in a pulsating manner. Cutting takes place at the highest point of amplitude or expansion of the tool. Very hard materials such as glass, ceramics and precious stone.

-          Spark eroding -  an electrical current is discharged between two electrodes which are in the preence of a dielctric liquid, this produces the spark. It is the repeated action of this discharge which causes the removal of material from the workpiece and shapes the object in the desired accurate fashion. It is used in automotive and engineering industries.

 

PIERCING AND BLANKING PROCESSES:

• Sheet metals can be cut to a required shape using punches. These cut through the material using a shearing action, much in the same way that scissors cut through paper.
• A guillotine is usually used to cut sheet metal off a roll into useable sheet sizes. These sheets are then passed into either manually operated or automatic machines that will cut the material to shape and/or punch holes into it.

POLYMERS - MOULD PROCESSES

COMPRESSION MOULDING:

• The manufacturing process generally used for processing thermosetting polymers.

- Advantages of compression moulding:

1. Moderately complex parts can be produced over long production run times.
2. Although there is some heavy machinery involved, start-up costs are relatively low; moulds are less expensive than those used in injection moulding.
3. There is little waste material.

- Disadvantages of compression moulding:

1. It is necessary to manufacture a preform.
2. The process is restricted to products with low complexity.

--> Process = (STEP 1) A preformed 'slug' (compressed powder) of material is placed between the two halves of the mould. (STEP 2) The mould is heated to a temperature that will allow the cross-links to form within the material. (STEP 3) The mould is closed onto the preform and the pressure used will force out any excess material. The moulds are held closed under pressure at the required temperature for a period of time that is sufficient to allow all of the material o be 'cured', i.e all cross-links formed. (STEP 4) When the mould is opened, the product can be ejected while it is still hot (it does not have to be cooled) and the process can begin again.

INJECTION MOULDING:

• This process is most commonly associated with thermoplastics and is used to produce complex three-dimensional shapes.

--> Process = (STEP 1) Plastic granules (plus any other additives and colours mixed with them0 are placed in the hopper. The granule mixture falls through the hopper onto the Archimedean screw. (STEP 2) The screw is rotated via the motor and the gearbox. This action forces the polymer forwards towards the heaters, where it becomes softened to the point where it is ready to be injected into the mould. (STEP 3) The hydraulic ram forces the softened polymer through the feedhole into the mould. Pressure from the ram ensures the mould cavity has been filled. (STEP 4) When sufficient time has passed to allow the polymer to cool and solidify, the mould halves are opened. As they open, ejector pins are activated to release the product from the mould. (STEP 5) Once emptied, the mould is then closed ready to begin another cycle.

- Advantages of injection moulding:

1. Very complex 3-D shapes can be produced.
2. High volumes can be produced with consistent quality.
3. Metal inserts can be included in the item being produced.

-Disadvantages of injection moulding:

1. Initial set-up costs are high.
2. Moulds are expensive.

BLOW MOULDING:

• This process is used in the manufacture of bottles and other containers. Objects produced are usually hollow and have a narrow neck.

--> Process = (STEP 1) A tube of heated and softened polymer is extruded vertically downwards. This tube is called a Parison. (STEP 2) The mould halves close, trapping the upper end of the parison, effectively sealing it. (STEP 3) Hot air is then blown into the parison forcing it out to follow the shape of the mould. (STEP 4) The mould effectively cools the polymer allowing it to be released from the mould. (STEP 5) The mould halves are opened and the product is extracted.

- Advantages of blow moulding:

1. Once set up, blow moulding is a rapid method of producing hollow objects with narrow necks.
2. Non-circular shapes can be produced.

- Disadvantages of blow moulding:

1. Moulds can be expensive.
2. It's difficult to produce re-entrant shapes, i.e shapes that do not allow easy extraction from the mould, e.g a dovetail joint.
3. Triangular-shaped bottles are difficult to produce.

ROTATIONAL MOULDING:

• It is used in the manufacture of 3-D hollow products, such as footballs, road cones and large storage tanks.

--> Process = The machines have a number of arms that rotate about a fixed central point. Moulds are attached to the end of each arm and are rotated continuously. The only time the moulds do not rotate is when they are at the starting point and the end of the process.
(STEP 1) Once the moulds have been loaded with a precise weight of thermoplastic powder the mould halves are clamped together. (STEP 2) The moulds are then rotated about the arm spindle and the whole arm is rotated towards a heated chamber where the thermoplastic material is heated to its melting point. The continuously rotating mould ensures that the thermoplastic covers all of the mould. (STEP 3) The next stage of the process is the cooling chamber where the material is cooled ready to be extracted from the mould. (STEP 4) The mould is then returned to the starting point where the mould halves are separated and the product removed.

- Advantages of rotational moulding:

1. One-piece mouldings can be produced.
2. It is ideal for both rigid, tough shapes and flexible shapes.
3. A large range of sizes is possible, from small medical components to large storage tanks.
4. Surface textures can be applied to the finished products from textures applied in the mould.
5. Moulds ten to be cheaper than those for injection or blow moulding, since high pressures are not required.
6. Cheaper moulds allow lower production runs.

- Disadvantage of rotational moulding:

1. Only hollow shapes can be produced in this way. More complex 3-D shapes would either be blow moulded or injection moulded.