1.6.1 Scales of production

Intrduction

Designers and manufacturers have to be conscious of the scale of production for any of their intended products, since this will have an important bearing on decisions that are made about its design and manufacture.

The use of ICT in manufacture can be expensive and time consuming so it is important to consider the different scales of production that can be used. After all, it is not always feasible to invest in CAD/CAM

equipment for smaller scale production.

Manufacturing efficiency is often improved by incorporating sub-assemblies, which are pre-made elements of a product, or bought in components in the final assembly process.

One-off

One-off/bespoke production refers to products that have been designed and manufactured for a single situation. These may be a pair of iron gates, a piece of jewelry or furniture but may also include more hi-tech items such as carbon fibre bicycle frame for an Olympic athlete. The item will be ‘bespoke’ and a higher price than a mass produced item. They will also be individual and unique which is often what the customer wants.

batch

Batch production is when a set number of items are to be produced. This could range from a just a few (small batch) to a few thousand (large batch) but there is a limit on the number (batch) produced in one run. The use of jigs and templates will help to ensure items are similar but rapid prototyping such as laser cutting and 3D printing could be used if the machinery was already available.

Mass

Mass/line production is when items are made in large amounts and often in very high volumes. Essentially every consumer who wants that item could purchase one. Light bulbs, nuts and bolts, even cars are mass produced, but if items are mass produced exceeding customer demand, it would result in huge stockpiles of unwanted products taking up valuable warehouse or storage space.

Many expensive consumer items are actually produced to order but if the volume produced is high enough, they would be considered mass produced. Materials might be adapted for this to be economic and more advanced machinery might need to be invested in.

Continuous

Continuous production is when production runs 24 hours a day, 7 days a week because there is always a need for the product and stopping production would cause problems for consumers or industry. Milk, water, electricity, newspapers, bread and oil are all examples of products continuously produced. Again, the materials to be used and the expensive machinery required would need to be considered.

unit production ststems (UPS)

Unit production systems (UPS) are used extensively in the manufacture of textile products and are based on the principle of using an overhead transporter system, incorporating hanging carriers to convey components between workstations. It reduces the number of handling operations and optimises the use of manual labour while improving quality of goods.

vertical in-house production

Vertical in-house production (also known as vertical integration) is an arrangement in which the supply chain of a company is owned by that company.

When a company require external parts this is known as outsourcing.

Advantages include:

reduced risk of unexpected price rises for components
less susceptibility to suppliers going out of business
protection of their brand and IP rights
easier implementation of Quality Assurance strategies

Apple are a company who have moved to this arrangement in terms of casings, CPU and proprietary PCB’s etc. but, given the cost of developing cutting edge technology, they still outsource RAM and screens (Samsung) and Wi-fi/Bluetooth (Qualcomm) as well as other internal components.

Efficient use of materials

When setting out to design and manufacture a product, deciding which material to use can be straightforward since the specification for the part may preclude other options. For example a twist drill must be made from a high speed steel if it is to drill into softer materials and a hinged lid for a freezer food container would be made from PP as it is the only polymer that can withstand freezing temperatures!

However, cheaper versions may be found, but this might affect the product quality and increase the likelihood of failure!

The amount of material used is also a key consideration and advances in FEA and CAD engineering may lead to a product being improved while actually using less material.

Just in time (JIT)

Just in Time (JIT) is a system devised to ensure customers get the products they want at the right time without the need for parts to be stockpiled or stored. This places more responsibility on the manufacturer to ensure all the parts arrive in time and to avoid delays, and this is further complicated when ordering parts from numerous different suppliers.

A company like Land Rover may only have enough parts in stock to make the cars for one day but their production pipeline will ensure that the parts required for each car will arrive in time to meet the customers requirements.

Design and the economic use of materials

Using materials economically can range from designing nested parts to minimise waste (below) when laser cutting, to ordering large sheets of wood that can be economically cut for a one off furniture job.

The materials and processes used will depend on the material properties required, the manufacturing processes available for that material, the scale of production and the intended cost of the item.

Many children’s toys are now made by rotational moulding as components can be both hollow and thick walled resulting in a strong but lightweight product. Making a product by rotational moulding would be very cost effective leading to lower unit costs but the initial cost of the machinery and moulds would need to be taken into account.

Making that same product by injection moulding would require at least two moulds, and for the resulting parts to be glued or fixed together which could be weaker and would introduce additional parts and labour costs.

Manufacturing processes which increase accuracy and reduce waste

Products need to be as accurate and uniform as possible in order to function. For example a car engine requires parts that fit and work perfectly together.

In order to ensure accuracy, automated machinery is often used since human labour would be too expensive and time consuming, and would be less accurate.

comparing bulk and one-off production

One-off production is the bespoke design and manufacture of single products in accordance with individual specifications, often requiring a high proportion of manual labour and skill.

Bulk production, whether at line or mass level, makes it viable to use automated manufacturing techniques.

An artisan making one-off items of jewellery or furniture could not justify the investment in automated machinery as they would never see any return from the investment.

Some mass-produced items, such as footwear and clothing can be customised to your requirements but this is not a truly bespoke item, it is just a variation on a mass produced item.

Bulk production does not always equate to cheaper as a mass produced item can still be more expensive!

As an example, Herman Miller’s Aeron office chair is one of the most expensive available but it has many ergonomic features and quality components that are hand assembled.

This is in stark contrast to Robin Day’s PP Chair which is much cheaper and still one of the best selling chairs of all time.

Herman Miller’s Aeron office chair is one of the most expensive available

Robin Day’s PP Chair which is much cheaper

Go to 1.6.2 Production Systems >