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Conceptual Understanding: As a business grows in size and produces more units of output, then it will aim to experience falling average costs of production—economies of scale. The business is becoming more efficient in its use of inputs to produce a given level of output. Designers should incorporate internal and external economies of scale when considering different production methods and systems for manufacture.
Production system selection criteria include time, labour, skills and training, health and safety, cost, type of product, maintenance,impact on the environment and quality management.
Craft production: A small-scale production process centred on manual skills.
This type of production makes a single, unique, product from start to finish. Labor intensive, highly skilled, eg. one-off jewellery or tailored clothing, handmade crafts (furniture), etc.
Mechanised production: A volume production process involving machines controlled by humans.
This type of production usually involves more hazardous environmental aspects, toxic, heavy loads, high heat. The machines are controlled by the humans.
Automated production: A volume production process involving machines controlled by computers.
Usually incorporated in a field of high and constant volume, their is little to no requirement for the human to be involved in the process, but have more of an over-watching responsibility.
Locally based, allowing clients to converse directly with manufacturer
Value of product will be high due to people willing to pay the higher cost for one-off products
people are willing to pay the higher cost for one-off individualised products as quality tends to be seen as considerably higher than something that was mass-produced;
The product can also be customised to fit personal needs, and there is a good deal of flexibility for the designer, customer and craftsman.
Very flexible manufacturing system, enables a large variety of products to be manufactured, geared to customer specification production.
higher status is linked with craft products; craft production may result in higher quality goods (does depend on the product).
Variable production costs are high, particularly labour costs due to paying for highly skilled labour.
Economies of scale refers to the decreased per unit cost as output increases – as one off products are produced through craft production, it means the unit cost will be expensive.
Although the manufacturing process does not require machines for the producer, it takes a great amount of time and effort; therefore it becomes much more expensive for the buyer.
With craft production it is not possible to produce on a larger scale.
Slower production than mechanisation.
The creation of economies of scale ... the product is cheaper
The quality of the product is improved as fewer human errors will occur, the finish of the product will also be improved.
Often repetitive dirty tasks can be carried out by machines.
Increased wages due to training and becoming skilled efficiency of production: less time is taken to produce good.
Redundancy - machinery for labour substitution
Health and safety. Work conditions are usually poor in the factories, lack of safety standards can be an issue in some cases.
Repetitive strain injury.
Cost of energy, training and capital machinery. Increased wages due to highly skilled operators needed.
Consumer choice is minimal, the products are identical.
Environmental pollution.
boredom for the workers
low job satisfaction for workers
eliminates human error;
built in quality control;
minimises waste;
consistency of output;
reduction of labour costs;
machines can work 24/7;
adaptable systems can include robots as well as CNC machines;
Job satisfaction; Increased through workers increased responsibility
has greatly increased production and lowered costs for for consumer,
thereby making cars, refrigerators, televisions, telephones, and other goods available to more people.
Consumer choice; Automation means a wider variety of products can be produced cost-effectively
higher costs of capital equipment
Training costs
possible social implications of maintaining productivity with a reduced workforce.
Machines do roles of humans, therefore more unemployment;
Improved working conditions/ Health and safety issues, Humans not operating machines (mechanised or craft production) so fewer accidents; reduced hazardous activities,Cleaner jobs, employees further away from noise;
social interaction; due to Flexible working hours/ fewer people so less social interaction
Mass production: The production of large amounts of standardized products on production lines, permitting very high rates of production per worker.
Mass customization: A sophisticated CIM system that manufactures products to individual customer orders. The benefits of economy of scale are gained whether the order is for a single item or for thousands.
Computer numerical control (CNC): Refers specifically to the computer control of machines for the purpose of manufacturing complex parts in metals and other materials. Machines are controlled by a program commonly called a “G code”. Each code is assigned to a particular operation or process. The codes control X, Y, Z movements and feed speeds.
Design for Manufacture
How do you DfM or Design for Manufacture?: These include: using standard parts, reducing the number of parts, employing modular design principles, reducing the number of sub-assemblies, use standard parts/fasteners, ease of fabrication, minimise handling, etc.
Think of this as if you were making box that needed to be made from wood and needed to be made in the workshop at school.
Would you grow a tree, chop it, season it, cut it, plane it, glue it?
Would you use the large pieces of MDF already in the the workshop?
Considering what you have in place for production whilst still in the design stage helps you achieve efficiency, this is Designing for Manufacturing.
The heart of any design for a manufacturing system is a group of design principles that are structured to help the designer reduce the cost and difficulty of manufacturing an item:
1. Reduce the total number of parts.
The reduction of the number of parts in a product is probably the best opportunity for reducing manufacturing costs. Less parts implies less purchases, inventory, handling, processing time, development time, equipment, engineering time, assembly difficulty, service inspection, testing, etc. In general, it reduces the level of intensity of all activities related to the product during its entire life.
2. Develop a modular design.
The use of modules in product design simplifies manufacturing activities such as inspection, testing, assembly, purchasing, redesign, maintenance, service, and so on.
3. Use of standard components.
Standard components are less expensive than custom-made items. The high availability of these components reduces product lead times. Also, their reliability factors are well ascertained. Furthermore, the use of standard components refers to the production pressure to the supplier, relieving in part the manufacturer's concern of meeting production schedules.
4. Design parts to be multi-functional.
Multi-functional parts reduce the total number of parts in a design, thus, obtaining the benefits given in rule 1.
5. Design parts for multi-use.
In a manufacturing firm, different products can share parts that have been designed for multi-use. These parts can have the same or different functions when used in different products. In order to do this, it is necessary to identify the parts that are suitable for multi-use. For example, all the parts used in the firm (purchased or made) can be sorted into two groups: the first containing all the parts that are used commonly in all products. Then, part families are created by defining categories of similar parts in each group. The goal is to minimize the number of categories, the variations within the categories, and the number of design features within each variation.
6. Design for ease of fabrication.
Select the optimum combination between the material and fabrication process to minimise the overall manufacturing cost.
7. Avoid separate fasteners.
The use of fasteners increases the cost of manufacturing a part due to the handling and feeding operations that have to be performed. Besides the high cost of the equipment required for them, these operations are not 100% successful, so they contribute to reducing the overall manufacturing efficiency. In general, fasteners should be avoided and replaced, for example, by using tabs or snap fits.
8. Minimise assembly directions.
All parts should be assembled from one direction. If possible, the best way to add parts is from above, in a vertical direction, parallel to the gravitational direction (downward). In this way, the effects of gravity help the assembly process, contrary to having to compensate for its effect when other directions are chosen.
9. Minimise handling.
Handling consists of positioning, orienting, and fixing a part or component. To facilitate orientation, symmetrical parts should be used whenever possible. If it is not possible, then the asymmetry must be exaggerated to avoid failures. Use external guiding features to help the orientation of a part.
Design for materials: Designing in relation to materials during processing.
Lego uses ABS as it has a high finish, range of colours, is safe to play with.
Design for process: Designing to enable the product to be manufactured using a specific manufacturing process, for example, injection moulding.
Lego uses ABS as it can be easily injection moulded to high accuracy, produce high quantities quickly, etc
Design for assembly: Designing taking account of assembly at various levels, for example, component to component, components into sub-assemblies and subassemblies into complete products.
E.g. Apple have suppliers ship parts already sub-assembled so they can fit inside the case/laptop/phone. They use simple and minimal assembly time and fasteners to enable efficient assembly time
Design for disassembly: Designing a product so that when it becomes obsolete it can easily and economically be taken apart, the components reused or repaired, and the materials recycled.
E.g. BMW cars have all parts labelled to what material it is made from to help recycle/recovery of materials. Parts can all be separated into their material group and BMW has special facilities set up just to do this.
(Interesting that Apple chooses the opposite for this design for disassembly)
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