//2.7-Accuracy in design and manufacture

Question 1

What is measurement

Answer 1

This is the process of using tools such as rules, tapes and gauges to check existing dimensions. The mertic (SI) system millimetre unit is almost universally employed in design and manufacture

Question 2

What are dimensions

Answer 2

This is the distance between features of a part or product, such as height or length

Question 3

What is marking out

Answer 3

This is the transfer of designs on to materials or parts being manufactured to indicate the position of features such as holes or edges

Question 4

What is accuracy

Answer 4

• this is how close measurement is to the required value
• accurately fitting parts ensure the correct functions of products
• the acceptabe range of accuracy is know as the tolerance

Question 5

What is the tolerance

Answer 5

The acceptable upper and lower limits of accuracy of a measurment

Question 6

What method can be used to improve accuracy

Answer 6

datum edges and surfaces, as well as vertical and horizonal lines generated by laser evels, provide reference points to facilitate imporved accuracy

Question 7

What is datum

Answer 7

The reference surface or edge from which measurements are taken to improve accuracy

Question 8

Testing methods to eliminate errors

Answer 8

• 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 0.015 mm
• CNC machines use computer codes to control their movement and ensure accuracy
• laser micrometers, material thickness sensors and alignment systems are examples of non-contact devices increasingly being used

Question 9

Measuring aids used for accuracy-jigs

Answer 9

• jigs and devices that guide tools such as drills accurately for repetitive machining operations without the need for marking out
• they make it possible for fast, high quality machining operations to be carried out by semi skilled workers

Question 10

Measuring aids used for accuracy-fixtures

Answer 10

• fixtures maintain the accurate alignment of parts for processes by providing a framework into which they are securely clamped during manufacture
• they ensure every manufactured assembly is of high quality with minimal rejects

Question 11

Measuring aids used for accuracy-templates

Answer 11

• templates havd a rigid shape or pattern to transfer a design on to a work piece to ensure consistency
• they are commonly used in batch production situations