The Power of Production Batches: Understanding and Optimizing Flow
In any operational or manufacturing setting, the efficient movement and processing of materials are crucial for reducing cycle time, managing costs, and improving throughput.
What is a Batch?
A batch, in its simplest sense, is a group of items or parts treated as a single unit for movement or processing.
Transfer Batch: This is the number of parts that are accumulated before being transferred from one workstation to the next.
It’s about the logistics of material movement. Process Batch: This is the number of parts or transfer batches that are processed together at a single workstation before that workstation is changed over (or before the processing cycle is complete).
The two types of process batches illustrate the concept further:
Sequential Process Batch: This is a group of parts of the same family processed sequentially on a machine before it's changed over to produce a different part family.
Simultaneous Process Batch: This is a group of parts processed simultaneously in a single run, such as units in a furnace or a burn-in operation where the time is fixed regardless of the quantity (up to the capacity limit).
Recognizing and defining batch types and sizes is critical because they directly impact the core performance metrics of an operation:
Cycle Time (Flow Time): Smaller transfer batches reduce the time a part has to wait for its batch to form, thereby shortening the overall cycle time.
A part can start being processed at the next station sooner. Resource Utilization and Cost: Batch size creates a trade-off between cycle time and material handling effort.
Smaller transfer batches mean more frequent material handling (e.g., 30 cart trips instead of one forklift trip), increasing labor or equipment use.
Larger sequential process batches mean less frequent changeovers (setups), which is good for utilization, but this increases the waiting time for parts arriving later in the batch.
Process Efficiency: In simultaneous batching (like the medical unit burn-in), recognizing the batch size helps maximize the use of the fixed 24-hour cycle time. You want to fill the room to capacity to get the most output per fixed-time operation.
In essence, recognizing the batch allows managers to balance the competing goals of short cycle time (which favors small batches) and high resource efficiency/low material handling costs (which often favor large batches).
How Do We Recognize the Batch?
We recognize the batch by observing how materials are grouped for either movement or processing.
For Transfer Batches: Observe the logistical break point. How many parts accumulate on the floor, in a container, or on a pallet before a material handler moves them to the next step? This is the point where the cost of moving the material is balanced against the cost of parts waiting for the move.
For Process Batches: Observe the processing break point at a machine:
Sequential: How many parts of the same family are run before the machine is changed over (or set up) for a different part family? This is often driven by the cost and time of the changeover.
Simultaneous: What is the physical capacity of the processing unit (furnace, oven, burn-in room) and how many parts are loaded at one time for a single processing cycle? This is a physical constraint that defines the batch size.
When Should We Assign a Batch Number?
The term "assigning a batch number" is typically a systemic or procedural action related to tracking, quality control, or inventory management.
Based on the operational definitions:
Upon Transfer: A batch number is often assigned when a transfer batch is created, especially if a transfer log or move ticket is used.
This allows for tracking the location and flow of a specific group of material. Upon Processing: A batch number is also critical when a process batch begins, particularly in simultaneous batching (like the burn-in operation). In this case, if one unit in the batch is defective after processing, a quality check might require investigating all units that shared the same batch number and environmental cycle.
For Quality and Traceability: A batch number should be assigned whenever it is necessary to trace the history of a group of parts that shared a common set of processing conditions (e.g., same setup, same temperature cycle, same time in process).
In short, a unique batch number should be assigned when a group of items is consolidated for processing or movement to ensure accountability, track throughput, and maintain quality traceability.