Introduction

The design and manufacture of a successful product relies heavily on appropriate planning and monitoring throughout the process. Effective planning and preparation reduce the risk of an unsuccessful final outcome that may fail to meet key specification criteria.

Designers must ensure that the products they design:

• meet customer and legal requirements

• can be produced with the equipment/technology available

• can be produced to budget

• can be produced within the required timescale

Often, a feasibility study can be carried out to assess the practicality of a proposal of a proposed project or system. See Unit 1.12 for more information on feasibility studies.

Planning for accuracy and efficiency

When producing a prototype product, it is essential that you plan for accurate production.

A detailed product design specification (PDS) is one essential element in the process, but the development of the design must allow the concept to be tested against key specification criteria prior to final production or prototype.

The proposed manufacturing procedures must be evaluated for suitability and the achievable level of accuracy - For example, a tolerance of + or – 0.0001mm when machining on a lathe will likely require outsourcing to a company with the necessary equipment and skill to achieve that level of accuracy.

The successful manufacture of a product on any scale requires a clear schedule of production, with deadlines and Quality Control inspections factored in.

Ensuring accuracy of prototype designs - Pre-production: 

accuracy in prototype development relies heavily on a UCD approach (see previous units for more on UCD) with client feedback playing a major part in the success of the prototype. This list covers some of the pre-production Quality Assurance (QA) procedures used to ensure accuracy:

• CAD simulations

• working drawings with tolerances

• mock-up models and mechanical systems/test rigs

• client feedback/approval

• peer review

Ensuring accuracy of prototype designs - Production: 

during production of a prototype, product accuracy is ensured using a range of QC checks. These are used in conjunction with client feedback to ensure visual aesthetic checks

• appropriately accurate dimension checks

• machine tooling and alignment checks

• assembly checks of multiple components

• quality checks of the manufactured finish

The definition of small, medium and large scale production is very subjective and testing procedures will also vary based on the cost analysis to ensure profitability.

Ensuring accuracy in various scales of production - Pre-production phase: 

during product development, a wide range of techniques are used to ensure that the product going into production is accurate compared to the PDS. The cost of rectifying errors during pre-production is considerably less than during production.

Techniques used include:

• CAD including simulations and costings

• working drawings with tolerances

• sample prototypes

• templates, jigs and fixtures

• focus groups and surveys

• NDT (Non Destructive Testing) and destructive testing

Ensuring accuracy in various scales of production - Production phase: 

when manufacture of the final product begins, accuracy is assured using a range of QC checks to compare the products against the PDS. Some of the types of checks used include: 

• visual aesthetic checks during regular sampling 

• sample dimensions using flexible measuring equipment

• tolerance dimension checks such as a go/no go gauge

• machine tooling and alignment calibrations

• specific sampling regularity set by legal requirements

• checks of the quality of the manufactured finish

Quality assurance

Quality assurance, or QA, refers to the procedures and policies put in place to reduce waste, and to ensure manufactured products are produced accurately within set tolerances. By using effective QA procedures, a manufacturer is aiming to produce products ‘right first time and every time’.

To check that products being produced conform to the tolerances set, QA and QC checks must be included within the production process. Examples of QA include:

• only sourcing materials from suppliers that hold ISO 9001 Quality Management Standard

• setting specific temperature ranges for moulding to ensure effective filling of cavities and speeds of cooling

• setting rigid maintenance schedules for machinery to ensure cutters are machining within tolerances.

As the effectiveness of QA procedures increases, the number of QC issues and waste products will inevitably decrease.

Using CAD software the following tests can be carried out....

Project management systems

Effective project management is essential in all design and manufacture activities to ensure they are completed within budget and to agreed time scales.

Lean manufacturing

Six Sigma is primarily aimed at reducing the number of defective products through monitoring. Lean manufacture, however, is a systematic approach to production which aims to eliminate all waste from product production.

Waste is identified as anything that does not benefit the client and is given the name ‘muda’. There are seven forms of muda which are given the acronym TIMWOOD:

• Transport: rick of loss and damage when transporting goods

• Inventory: using JIT to reduce the inventory on site at any time

• Movement: employees and their equipment, time wasted in production

• Waiting: hold ups in production while others catch up

• Over production: making more products than there Is demand for means wasted inventory and storage space (see JIT)

• Over processing: investment in machinery to mass produce must be justified by the demand for the product and level of precision

• Defects: faulty products must be removes, This is key to Six Sigma and relies on effective QC and quality QA procedures