Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Systematically diagnose common faults in workshop machinery.
• Apply correct maintenance procedures like lubrication and minor repairs.
• Operate and maintain machinery safely.
• Document fault-finding and maintenance activities accurately.
• Describe the importance of predictive maintenance for saving costs.

Lesson summary

Mechanical Technology in South Africa, particularly focusing on fault finding and maintenance, is crucial for the nation's economy and infrastructure. From maintaining agricultural machinery that feeds our population to keeping our transport systems running efficiently, these skills are in high demand. Understanding these procedures empowers individuals to contribute to the upkeep of essential services and increases employability in a sector vital to South Africa's development. This week, we'll focus on developing a systematic approach to identifying and rectifying faults in mechanical systems, ensuring longevity and optimal performance.

Lesson notes

Fault finding and maintenance are essential aspects of mechanical technology. They involve systematically identifying and rectifying problems in machines and equipment to ensure their optimal performance and longevity. This includes preventative and predictive maintenance. 2.1 Fault Finding Methodology: A systematic approach to fault finding is crucial. This approach typically involves the following steps: Step 1: Problem Definition: Clearly define the problem. What is the machine not doing that it should be doing? What are the symptoms? Interview the operator.

Step 2: Visual Inspection: A thorough visual inspection can often reveal obvious problems such as loose connections, damaged parts, leaks, or excessive wear. Look for physical damage, oil leaks, unusual noises, or smoke.

Step 3: Functional Testing: Operate the machine or system to observe its behavior. Note any unusual sounds, vibrations, or performance issues.

Step 4: Logical Deduction/Troubleshooting Charts: Using a troubleshooting chart or logical reasoning, systematically eliminate potential causes of the fault. This often involves testing individual components or subsystems.

Step 5: Use of Diagnostic Tools: Employ appropriate diagnostic tools such as multimeters, pressure gauges, stethoscopes, or specialized diagnostic software to gather more detailed information about the fault.

Step 6: Component Testing: Once a suspect component has been identified, test it thoroughly to confirm whether it is faulty.

Step 7: Repair or Replacement: Repair or replace the faulty component.

Step 8: Verification: After the repair, verify that the problem has been resolved by testing the machine or system under normal operating conditions.

Step 9: Documentation: Record the fault, the diagnostic process, the repair performed, and any parts replaced. 2.2 Types of Maintenance: Preventive Maintenance: Regularly scheduled maintenance tasks performed to prevent equipment failures. This includes lubrication, cleaning, inspection, and adjustment.

Example:* Replacing oil filters every 500 hours of operation in a diesel engine to prevent engine damage.

Corrective Maintenance: Repairs performed after a failure has occurred. This type of maintenance is often more costly and disruptive than preventative maintenance.

Example:* Replacing a burnt-out motor on a lathe after it fails.

Predictive Maintenance: Uses condition monitoring techniques to predict when equipment failures are likely to occur. This allows maintenance to be performed before a failure, minimizing downtime and reducing costs.

Example:* Using vibration analysis to detect bearing wear in a milling machine. An increase in vibration indicates that bearing replacement is needed.

Routine Maintenance: Daily or weekly tasks to keep the machine running at peak efficiency. Cleaning, checking fluid levels, and lubricating moving parts are considered routine maintenance. 2.3 Lubrication: Proper lubrication is critical for minimizing friction and wear in machinery. The type of lubricant used depends on the application.

Oils: Used in engines, gearboxes, and hydraulic systems.

Greases: Used in bearings, joints, and other components where a thicker lubricant is needed.

Solid Lubricants: Such as graphite or molybdenum disulfide, are used in high-temperature or high-pressure applications. 2.4 Common Faults and Solutions (Workshop Equipment Examples): Lathe: Fault:* Excessive vibration during operation.

Possible Causes:* Loose workpiece, worn bearings, unbalanced chuck.

Solutions:* Tighten workpiece, replace bearings, balance chuck.

Milling Machine: Fault:* Cutting tool chattering.

Possible Causes:* Loose tool holder, excessive cutting speed, insufficient rigidity.

Solutions:* Tighten tool holder, reduce cutting speed, ensure workpiece is properly supported.

Drill Press: Fault:* Drill bit wandering off center.

Possible Causes:* Dull drill bit, improper sharpening, excessive feed rate.

Solutions:* Sharpen or replace drill bit, reduce feed rate.

Welding Machine: Fault:* Erratic arc.

Possible Causes:* Dirty workpiece, poor ground connection, incorrect welding settings.

Solutions:* Clean workpiece, improve ground connection, adjust welding settings. 2.5 Worked

Example: Fault Finding on a Grinding Machine A grinding machine is experiencing a loss of power and the grinding wheel is slowing down unexpectedly.

Step 1: Problem Definition: The grinding wheel is losing power and slowing down during grinding operations.

Step 2: Visual Inspection: Check for obvious signs of damage to the motor, drive belts, or grinding wheel. Ensure the power cord is securely connected.

Step 3: Functional Testing: Turn on the machine and observe its operation. Note any unusual sounds, vibrations, or smells. In this case, the motor is making a straining noise.

Step 4: Logical Deduction: Possible causes include a slipping drive belt, a failing motor, or excessive friction in the spindle bearings.