Accuracy in Design and Manufacture

Question 1

Marking out

Answer 1

Transfer of designs on to materials or parts to indicate the position of features such as holes and edges

Question 2

Accuracy

Answer 2

The level of conformity of a measurement to the required value

Question 3

Tolerance

Answer 3

Acceptable upper and lower limits of accuracy of a measurement

Question 4

Datum

Answer 4

Reference surface or edge from which measurements are taken to improve accuracy

Question 5

Ensuring accuracy in manufacture examples

Answer 5

Dials on manual machine controls allow precision movement of tools and work pieces

Digital test gauges are very accurate, often computer linked, measuring devices

Profile projectors measure fine details such as threads to an accuracy of 0.015mm

CNC machines use computer codes to control movement and ensure accuracy

Laser micrometers, material thickness sensors and alignment systems are examples of accurate non-contact measuring devices

Question 6

Jigs

Answer 6

Devices that both hold the workpiece and guide tools accurately for repetitive machining operations without the need for marking out

Make high quality, fast machining operations able to be carried out by semi skilled workers as there is a reduced risk of human error

Question 7

Fixtures

Answer 7

Maintain the accurate alignment of parts for processes such as welding by providing a framework into which they are securely clamped during manufacture

Often designed so that parts can only be fitted the right way round - ensuring high quality assembly

Question 8

Templates

Answer 8

Rigid shape or pattern to transfer a design on to a work piece to ensure consistency

Ensures consistent repetition of the same outline by providing a consistent profile for marking out the shape of identical pieces

Question 9

Standardisation: geometric dimensioning and tolerancing (GD&T)

Answer 9

A standard system of engineering drawing symbols and figures used for specifying the product component dimensions and tolerances