Reducing Batch Size: A Field Checklist You Can Use This Week
Batch size is the number of units of work (products, documents, transactions, work items) that move together through a process step as a group. Large batches are convenient for the process step that creates them -- it is more efficient, per unit, to set up once and process many -- but they are costly for the overall system. A batch that is waiting to be processed is inventory: it represents invested cost, consumed space, and delayed customer delivery.
Lean operations target the smallest practical batch size, ideally single-piece flow. In 2022, reducing batch sizes also improves resilience: smaller batches reduce exposure to disruption, because a supply chain disruption or quality problem that affects a large batch affects fewer total units when batches are small. Here is a practical checklist for reducing batch sizes in your organisation.
Understanding and Mapping Your Current Batches
Map where batches form in your current value stream. In a value stream map, inventory triangles indicate where batches accumulate between process steps. Common batch accumulation points include: waiting for a minimum order quantity before releasing to the next step, weekly or monthly processing cycles (payroll, invoicing, reporting), approval queues that are processed on a fixed schedule, and handoffs between departments.
Measure the current batch sizes at each accumulation point. Count the number of units waiting between each process step. This is your current batch size. It is often larger than anyone in the organisation realises.
Calculate the inventory carrying time at each accumulation point. Divide the number of units waiting by the consumption rate of the downstream process. If 100 units are waiting and the downstream process consumes 10 per day, the average wait time is 10 days. This is the lead time contribution of that batch.
Reducing Batch Sizes in Practice
Target your largest batches first. Reducing a batch from 100 to 50 units saves more lead time than reducing a batch from 5 to 2. Identify the three largest batch accumulation points in your value stream and focus improvement efforts there.
Reduce setup time to enable smaller batches. The economic argument for large batches is that setup costs are amortised over more units. Reducing setup time reduces the minimum efficient batch size. A setup that takes four hours makes small batches uneconomical; a setup that takes four minutes removes that constraint.
Change processing schedules from calendar-based to demand-based. A weekly batch process that runs every Friday regardless of how much work has accumulated is a calendar-based schedule. Changing to a trigger-based schedule -- process when N items have accumulated, or when demand signals require it -- allows the natural batch size to shrink.
Pilot single-piece flow on one process first. Single-piece flow -- moving one unit at a time between process steps, with no accumulation -- is the Lean ideal. Rather than trying to achieve it everywhere at once, identify one process step where it is practically achievable and run a pilot. The pilot demonstrates the benefits and builds organisational confidence in the approach.
Track lead time improvement as batches reduce. The primary benefit of batch size reduction is lead time reduction. Measure total process lead time (from request to delivery) before and after each batch reduction. This quantifies the benefit and motivates further reduction.
XNM applies Lean operations and flow improvement methodology to public-sector and capital-project environments. Reach out to XNM's strategic advisory team to discuss batch size reduction and flow improvement for your organisation.