6.1 - Composition of Production Cycle
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Introduction to Back-track Loading
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Today, we'll start our discussion on loading methods, focusing first on the back-track loading method. Can anyone tell me what happens during this process?
Is it when the pusher goes back after loading a scraper?
Exactly! After loading scraper 1, the pusher detaches and back-tracks to spot scraper 2. This method is slow due to additional travel time. Can anyone guess why it's still favored?
Maybe because it allows cutting in the same direction?
Yes! Remember, back-track is commonly followed, despite being the slowest due to the preference for consistent cutting direction. A mnemonic to remember this is 'B-SLOW', standing for Back-track is Slow Loading on Way.
What makes it so slow specifically?
The slow cycle time results from the return travel time. This leads us into our next loading method, the chain loading method!
Exploring Chain Loading
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Now, let's dive into the chain loading method. What do you think is different about this compared to back-track loading?
Doesn't it not require the pusher to go back?
Spot on! Instead of returning, the scraper 2 waits near the pusher. This reduces return time. Can someone give me an example of where this loading method is suitable?
Long roads, right?
Correct! Chain loading is ideal for long, narrow cuts like roads because it maximizes efficiency. Let's summarize this: In chain loading, scraping happens continuously, decreasing cycle time.
Understanding Shuttle Loading
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Moving on, we have the shuttle loading method. Does anyone know when we might apply this method?
I think it's when there are fill areas in both directions?
Exactly! The pusher pushes the loaded scraper one way then detaches to push a scraper in the opposite direction. This helps reduce travel time as well. Can anyone highlight its advantage?
Is it quicker since it doesn't require backtracking?
Right again! By reducing return time, the shuttle method improves overall efficiency. Remember that it is applicable only where there's a need for dual-direction loading.
Balancing Scrapers and Pushers
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Lastly, we need to talk about balancing scrapers and pushers. Who remembers the formula to find how many scrapers one pusher can handle?
It's N equals T_s over T_p!
Excellent! By balancing the number of scrapers and pushers, we can minimize waiting times. What impact does this have on productivity?
It keeps both machines working efficiently, reducing costs, right?
Absolutely! The synchronization ensures maximum production capacity from both scrapers and pushers. Always aim for balance in production!
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section describes three loading methods used in the production cycle: back-track loading, which is the slowest due to its return time, chain loading, which is more efficient for long cuts, and shuttle loading, applicable when fill areas are available in both directions. It also emphasizes the balance necessary between scrapers and pushers to optimize productivity.
Detailed
Detailed Summary
In this section, we analyze the composition of the production cycle focusing on three primary loading methods of scrapers used in construction and earth-moving activities:
1. Back-track Loading Method
The back-track loading method involves the pusher detaching after loading the first scraper (scraper 1) and then returning to load the next one (scraper 2). This process introduces additional travel time, rendering it the slowest method due to backtracking requirements. Despite being slower, it is commonly adopted as operators prefer cutting in a consistent direction.
2. Chain Loading Method
The chain loading method suits long and narrow cuts, such as roads. In this case, the second scraper (scraper 2) awaits near the pusher instead of the pusher returning to retrieve it. This reduces the return time and thus the total cycle time significantly compared to back-track loading.
3. Shuttle Loading Method
Lastly, the shuttle loading method is less common and is applicable when there are fill areas in both directions. After completing loading of scraper 1, the pusher detaches and pushes a new scraper in the opposite direction. This method also reduces the return time and increases cycle efficiency.
Balancing Scrapers and Pushers
An important aspect discussed is maintaining a balance between scrapers and pushers. The formula to calculate the number of scrapers serviced by one pusher is provided:
$$N = \frac{T_s}{T_p}$$
Where:
- N = Number of scrapers served by one pusher
- T_s = Cycle time of the scraper
- T_p = Pusher cycle time
Optimizing this balance minimizes waiting times between scrapers and pushers, maximizing productivity and reducing costs.
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Back-Track Loading Method
Chapter 1 of 5
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Chapter Content
So, once the loading of scraper 1 is completed, the pusher will back-track return back and spot the next scraper, scraper 2, and start pushing it in the same direction. Once the scraper 1 is loaded, your pusher will get detached and return, which is called backtracking.
Detailed Explanation
The back-track loading method involves the pusher moving back to retrieve and push the next scraper after the current one is fully loaded. This method causes delays because the pusher has to travel back, which increases the cycle time. It's considered the slowest method primarily because it requires more time for the backtracking process.
Examples & Analogies
Think of this method like a train that must return to the station after dropping off passengers each time before picking up the next batch. It takes more time for the train to go back to the station than for it to travel forward, hence making the overall journey slower.
Chain Loading Method
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The next method which we are going to discuss is your chain loading method. Here, your pusher is pushing the scraper 1, once scraper 1 is completely loaded, the pusher will get detached and start pushing the next scraper without returning.
Detailed Explanation
In the chain loading method, the pusher doesn't return to load each subsequent scraper. Instead, as soon as scraper 1 is loaded, the next scraper (scraper 2) is already waiting nearby for the pusher to load it. This approach is efficient for long and narrow cuts like roads, as it minimizes the time spent returning to retrieve another scraper. By reducing return time, the overall cycle time is decreased.
Examples & Analogies
Imagine stacking boxes in a warehouse where, instead of going back to the start after delivering each box, you have the next box waiting in line for you to push it straight off the conveyor belt. This method allows you to work continuously without unnecessary backtracking.
Shuttle Loading Method
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The next one is shuttle loading, which can be applied when there are two fill areas in opposite directions. In this case, the pusher pushes scraper 1, and after it's loaded, it pushes another scraper in the opposite direction.
Detailed Explanation
Shuttle loading is used when two different filling areas exist, allowing the pusher to alternate directions without needing to backtrack. This setup enables scrapers to be loaded in both directions, significantly reducing the return time and cycle time altogether. However, it is less commonly used compared to the other methods.
Examples & Analogies
Think of shuttle loading like a bus service that has two routes. Instead of going all the way back to the main terminal after completing a drop-off, the bus immediately heads to the next available stop that is directly across the street. This reduces travel time by taking advantage of both directions instead of needing to return.
Comparison of Loading Methods
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When comparing these methods, back-track loading is the slowest due to the extra time needed for the pusher to return. In contrast, chain and shuttle loading methods generally offer shorter cycle times.
Detailed Explanation
Back-track loading is slow because the pusher loses time going back before it can push the next scraper. Conversely, both the chain and shuttle loading methods save time by minimizing the return trips the pusher must make. Consequently, even though they might not be the most common methods, they can greatly enhance efficiency in the right circumstances.
Examples & Analogies
Think about walking to the store. If every time you buy an item you have to walk back home to store it before going back for more, it takes longer. But if you have a bag and just keep adding items until it's full, or if you can drop items off at different locations along the way, you can keep moving and save time.
Balancing Machine Usage
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Another important aspect is balancing the number of scrapers and pushers to ensure that one does not wait for the other, thereby reducing waiting time and improving productivity.
Detailed Explanation
Properly balancing the number of scrapers per pusher is crucial to prevent downtimes. If too many scrapers wait for a pusher, it reduces overall productivity and increases cycle time. The ideal ratio allows machines to operate at their maximum efficiency, moving materials without unnecessary delays.
Examples & Analogies
Imagine a restaurant kitchen where a chef tries to prepare multiple dishes without enough kitchen staff. If the chef has too many orders and not enough cooks, food preparation slows down. However, if the workload is balanced with enough helpers for each task, the meals get prepared and served more quickly, keeping customers satisfied.
Key Concepts
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Back-track Loading: Requires return trips making it the slowest method.
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Chain Loading: Reduces return time by having scrapers wait near the pusher.
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Shuttle Loading: Utilizes fill areas in both directions to enhance efficiency.
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Cycle Time: Importance of calculating the time required for the scraping operation.
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Balance of Machines: Ensuring optimal productivity by minimizing waiting times.
Examples & Applications
In a construction site for a new highway, the chain loading method is used as large scrapers are lined up along the length of the road, allowing for quicker loading times.
In a mining operation with two fill areas, the shuttle loading method is adopted to effectively manage material movement without wasting time on backtracking.
Memory Aids
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Rhymes
Back-track is slow, return it must go; Chain loading is keen, quick and lean.
Stories
Imagine a busy road construction site. The pusher insists on back-track loading, making it slow. Along comes chain loading, allowing scrapers to line up and work together seamlessly, enhancing speed!
Memory Tools
Remember 'BCS' for Back-track, Chain, and Shuttle loading.
Acronyms
B-SLOW for Back-track SLOW Loading On Way.
Flash Cards
Glossary
- Backtrack Loading
A loading method where the pusher must return to load the next scraper, resulting in increased cycle time.
- Chain Loading
A method of loading where the next scraper waits near the pusher, reducing return time and increasing efficiency.
- Shuttle Loading
A loading method where the pusher alternates between scrapers moving in opposite directions due to fill areas in two directions.
- Cycle Time
The time taken to complete a full cycle of loading, traveling, dumping, and turning.
- Scraper
A heavy equipment used for loading, hauling, and spreading materials, especially in earth-moving operations.
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