1.2. Adjustment Factors for Height of Cut and Angle of Swing

As the truck moves further away, your angle of swing would increase. As the angle of swing increases, you can see that your cycle time will increase, and the productivity will decrease.

The angle of swing refers to the horizontal angle between the loading position (where the excavator digs) and the dumping position (where the truck is located). If the truck is placed too far from the excavator, the angle of swing increases. This means the excavator has to swing more to reach the truck, leading to longer cycle times, which in turn can reduce productivity. For optimal performance, a 90-degree angle of swing is preferable, as it minimizes time and maximizes efficiency.

Imagine swinging a bat to hit a ball. If the ball (the truck) is directly in front of you, you can swing easily. But if you have to swing much further to the side, it takes longer to make contact and the swing might not be as powerful. Similarly, a closer truck allows for a quicker and more efficient loading process.

If the actual height of cut is the same as optimum height of cut, it means the percentage is 100%. In that case, you need not apply any correction factor.

The optimum height of cut is the best height at which a shovel can work efficiently. If the actual height at which you're cutting material (the height of cut) matches this optimum height, productivity remains high, and no correction factor is needed. The correction factor is used when there's a discrepancy between these heights. For instance, if you're operating at only 60% of the optimum height, this lower efficiency directly impacts the productivity, necessitating the application of a correction factor to adjust calculations.

Think of baking a cake. If you follow the recipe exactly (the optimum height), the cake turns out perfectly. But if you only use half the amount of flour (60% of optimum), the cake won't rise properly (reduced productivity). In this case, you would need to adjust your expectations and cooking times based on this change.

When the angle of swing is more than 90 degrees, the correction factor is reducing, indicating that productivity will also reduce. Conversely, if the angle of swing is less than 90 degrees, the correction factor increases, suggesting that productivity is improving.

Angle of swing significantly affects how efficiently a shovel can operate. If the machine swings more than the ideal 90 degrees, less material is actually moved in a cycle because it takes longer to reach the target (the truck). This results in a lower productivity factor. However, if the angle is under 90 degrees, it means the excavator can load more efficiently, leading to an increase in productivity as the work can be done faster and with less movement.

Consider trying to throw a ball. If you're standing directly in front of your friend (90 degrees), it's an easy throw. But if you stand at an angle, it takes longer to adjust your position for a successful throw. However, if you stand slightly to the side but still face straight towards them (less than 90 degrees), you can throw more quickly and accurately.

As I told you, it is preferable to place a truck closer to the excavator. But at the same time, note that there should be some space left for the tail swing of the shovel. That means now you can have a complete 360-degree swing.

While it is efficient to place the truck close to the excavator to minimize swing distance, it is crucial to leave enough clearance for the excavator's tail. When the excavator swings around, it needs space to move without hitting the truck. This safety margin is called truck spotting clearance, and proper planning ensures smooth operation without accidents or delays.

Imagine trying to grab something from a crowded table. If you're too close to the edge, you might bump into someone or knock something off. But if you stand back just enough to have elbow room, you can reach out safely without causing a mess. In the same way, the excavator needs that elbow room while working.

The time needed for the loaded truck to leave its position and for a new truck (empty truck) to take the position is called as haul unit exchange time.

Haul unit exchange time is a critical factor in productivity. This is the time it takes for a loaded truck to leave and for a new truck to arrive and be ready to load. If trucks frequently wait or if there's a long delay before a new truck arrives, the excavator may have to pause, which increases overall cycle times and reduces productivity. Therefore, effective management of truck logistics is essential to minimize delays.

Think of a grocery store checkout line. If each customer takes a long time to check out, the line slows down, and more customers leave without buying anything (loss of productivity). But if the checkout process flows quickly, more customers can be served in the same amount of time. In excavation, ensuring that trucks arrive and depart quickly keeps the 'checkout line' moving smoothly.

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