Fig. 10 shows a flow diagram for a quality control system used in a factory that produces stainless steel water bottles. The lid lifts up and down. It is ma...

(a) The shape used in a flow chart to represent a decision is a diamond (also called a rhombus). [1]

Decision symbols contain a question with a Yes/No outcome, directing the flow along different paths depending on the answer. In the flow chart shown, both the "Visual check OK?" and "Dimensions within tolerance?" steps use diamond shapes because each requires a judgement that determines whether the bottle proceeds to the next stage or is returned for rework.

(b) Tolerance in manufacturing is the acceptable range of variation from a specified (nominal) dimension. [1] It defines the upper limit and lower limit within which a component's actual measurement must fall for it to be considered acceptable. [1]

Tolerances are necessary because no manufacturing process can produce a dimension to absolute perfection every time. By specifying a tolerance, the designer communicates how much variation the product can accept while still functioning correctly and fitting with other components.

(c) For a specified height of 250 mm with a tolerance of +/- 1 mm: [2]

• Maximum acceptable height: 250 + 1 = 251 mm [1]
• Minimum acceptable height: 250 - 1 = 249 mm [1]

Any bottle measuring between 249 mm and 251 mm inclusive passes the dimensional check. A bottle outside this range would be rejected.

(d) The flow chart shows that bottles failing the visual check follow the "No" path, which leads back to the production stage. [1] This means rejected bottles are either reworked (if the defect is correctable, such as a surface blemish that can be polished out) or scrapped and replaced with a newly produced bottle that must pass the visual check before proceeding to the dimensional inspection.