9.1 What is the main purpose of maintenance? 9.2 Briefly explain how basic preventative maintenance should be performed on the following systems: 9.2.1 Chain drive systems 9.2.2 Belt drive systems 9.3 State TWO properties of EACH of the following nylon products: 9.3.1 Polyethylene (PET) 9.3.2 Polypropylene (PP) 9.3.3 Polystyrene (PS) 9.4 State THREE factors that influence the coefficient of friction - NSC Mechanical Technology Fitting and Machining - Question 9 - 2022 - Paper 1

Preventative maintenance on chain drive systems includes:

• Cleaning: Regularly remove dust and debris from uncovered drives to prevent wear.
• Checking wear: Inspect the sprocket teeth and link plate for signs of wear and replace if necessary.
• Lubrication: Apply proper lubricants to ensure smooth operation and reduce friction.
• Tensioning devices: Check the functioning of tensioning devices to maintain the correct tension in the chain.
• Inspection for elongation: Periodically inspect chains for elongation, indicating that they may need replacement.

Preventative maintenance for belt drive systems involves:

• Wear and tear check: Regularly inspect the belts for any signs of wear or damage.
• Belt alignment: Ensure that the belt is properly aligned to prevent slippage and undue stress.
• Tension setting: Check the tension of the belt to ensure it is within the recommended range, adjusting as necessary.

Polyethylene (PET) has the following properties:

• Stiffness: PET exhibits high stiffness, making it suitable for structural applications.
• Chemical resistance: This material has good resistance to various chemicals, enhancing its utility in packaging.

Polypropylene (PP) is characterized by:

• Good fatigue resistance: It withstands repeated stress without failing, which is essential for products that undergo continuous movement.
• Heat resistance: PP can maintain its properties even at elevated temperatures, making it suitable for various applications.

Polystyrene (PS) features:

• Good insulation properties: It serves as an effective thermal insulator, important in packaging and construction.
• Light weight: PS is very light, which makes it favorable for applications that require weight savings.

Three factors that influence the coefficient of friction include:

• Surface roughness/texture: The texture of the surfaces in contact can significantly affect friction levels.
• Temperature: As temperature increases, the materials may behave differently, changing the coefficient of friction.
• Type of lubricant: The choice and application of lubricants can either reduce or increase friction depending on their properties.

Thermo-hardened composites undergo a chemical change during their formation, which renders them rigid. Once hardened, these materials cannot be re-heated to become pliable again due to the irreversible nature of the chemical bonds formed during curing.

Three different types of belts used in belt drive systems are:

• V-belt: Popular for its efficiency and ability to handle loads effectively.
• Flat belt: Often used in simple drive systems and conveyors due to its flexibility.
• Toothed/timing belt: Provides precise movement and is used in applications requiring synchronization.