Basics of Continuous Flow Manufacturing (CFM) with example
In the lean thinking , continuous flow manufacturing (CFM) is one of the basic principles. It is important to understand the underlying concept of Just in Time flow, it is not restricted to manufacturing only. The main principle is that material should always be moving one-piece at a time, at a rate determined by the needs of the customer. The flow of product must be smooth and uninterrupted by:
1. Quality issues
3. Machine reliability
6. Handling methods
7. Staging areas
8. WIP inventory problems
In large lot production, goods are manufactured in large batches. The sequence of operations used in producing parts in large batch sizes results in waiting time between operations. Large lot production has these faults:
1. Longer lead times for customer orders and delivery
2. Additional resources in terms of labor, energy and space
3. Additional product transportation expenses
4. Increased product damage or deterioration costs
Continuous flow or one-piece flow will:
1. Deliver a flow of products to the customer with less delay
2. Require less storage and transport
3. Lower the risk of losses through damage, deterioration or obsolescence
4. Provide a mechanism to solve other production problems
In a continuous flow manufacturing layout, the production steps are arranged in a tight sequence, such as a straight line or U-shaped cell, without WIP, using single piece flow. Inside this flow concept, each station and operator(in fact the whole system) must operate with complete reliability to achieve continuous flow and the desired takt time.
A system of production is attained with high quality levels using a variety of defect elimination and detection techniques. These are discussed under Lean Tools. Some of them are :
Poka-yoke : This means mistake proofing to prevent defects from proceeding to the next step.
Self check : Checks by the operator to catch defects and to correct the process.
Total Productive Maintenance(TPM) : TPM is used to help achieve high machine capability
Let us understand Batch Vs One-piece flow (CFM) in more detail
As we have seen in Lean thinking One –piece flow is the basic principle and it means that product moves through the process one unit at a time. On the other hand in batch processing, batches of products/parts are manufactured/processed at a time. This means moving the product through the process batch by batch.
The following three cases assume a series of three operations and each operation can process one unit per minute.
Case 1 : Orders are manufactured in batches of 100 units.
Only batches of 100 units are transferred from operation to operation. The total processing time is 201 minutes before the first unit is manufactured. Total order time for the entire process is 300 minute for 100 units.
Case 2 : Orders are manufactured in batches of 10 units.
Only batch of 10 units are transferred from operation to operation. The total processing time is 21 minute before the first unit is manufactured. Total order time for the entire process is 30 minute for 10 units.
Case 3 : Orders are manufactured in batches of 1 units.
1 unit at a time is transferred from operation to operation. The total processing time is 3 minute before the first unit is manufactured. Total order time for the entire process is 3 minute for 1 units.
The above three cases illustrates the power of one-piece flow concept. If the customer changes the requirement due to any reason, the factory will not have 300 units in queue in different stages of production. The factory will be able to shift production as per the new requirement.
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