Drive Production with Heijunka

Heijunka, which was initially adapted from the Toyota Production System, is now a crucial component of lean production in several different sectors.

The primary objective of Heijunka is to precisely sequence things to spread production volume and product mix evenly over a certain amount of time.

This produces a balanced, consistent, and predictable workflow that significantly improves flow and reduces waste.

The fundamental “production leveling” technique developed by Heijunka improves a manufacturing process’ adaptability and responsiveness to changing customer needs.

Key Highlights

• Heijunka is a lean production method for leveling workload and smoothing production flow over
  time
• It aims to eliminate waste by reducing variability, overburden and inventory
• Heijunka sequences diverse product types and volumes through a process
• It calculates takt time to set optimal production pace
• Using Heijunka boxes for scheduling creates a predictable workflow
• Implementing Heijunka leads to improved operational stability and flexibility
• It enables companies to adapt better to fluctuations in demand

Heijunka: What is it?

Heijunka is a lean manufacturing approach that aims to satisfy customer demand by gradually leveling up production quantities.

Producing steadily rather than in large quantities or bursts is the aim. It assists in mitigating production discrepancies.

The term “Heijunka” translates to “leveling” in Japanese and was a way for Toyota to adapt to fluctuating customer demand and stabilize production.

The key goals were to reduce inventory levels by matching supply with actual demand, as well as to level out the production workflow.

This helped reduce waste, improve flow efficiency, minimize inventory holding costs, and enable flexibility on the manufacturing floor.

The Heijunka method allowed Toyota to produce a variety of product types and volumes without delays or excess inventory build-up.

Over the years, the Heijunka concept has been widely adopted in lean environments to smoothen workflow, eliminate waste, and better align production capacity with market demand.

It remains a vital component of pull-based, flexible production systems.

Breaking Down Heijunka

Heijunka is a key concept in lean manufacturing that aims to smooth production and match it to customer demand. It involves leveling the production volume and mixing product types over some time.

The goal of Heijunka is to achieve stability and predictability in operations by reducing variability and overburden.

This is done by leveling out the production volume to spread out the workload evenly. It eliminates demand spikes and valleys which cause capacity issues.

By sequencing different product types together, production can flexibly adapt to the actual market demand.

This way a variety of products can be produced every day without significant changeovers between product types. Switching between product variants is streamlined.

The main objectives and benefits of implementing Heijunka include:

• Leveling production volume to smooth workflow and eliminate overburden
• Sequencing mixed model production to respond to market demand
• Reducing inventory and waste through continuous flow
• Shortening lead times and improving on-time delivery
• Adapting production schedule quickly based on demand
• Balancing workload across processes to avoid bottlenecks

By leveling production, smoothing scheduling irregularities, and sequencing products, Heijunka enables a predictable yet flexible flow. This leads to improved operational stability, waste reduction, and a better workflow.

Implementing Heijunka

Heijunka is implemented on the shop floor to level production and match it to customer demand. Proper implementation requires several key steps:

Grouping products

Products are grouped based on similarities to reduce changeovers. This allows the production of different product types while minimizing losses.

Calculating takt time

Takt time is calculated to set the pace of production. It determines the rate at which products must be made to meet demand.

Creating production schedule

A leveled schedule is created that sequences the production of different product groups based on takt time. The schedule aims to smooth production flow.

Using Heijunka box

A Heijunka box visually represents the sequencing pattern. Production cards or kanban signals are loaded in the box according to the schedule. This gives the master production a quick visual cue for scheduling.

Adhering to the Heijunka schedule allows staggered production of diverse products in line with customer demand.

Changeovers are streamlined through product grouping while inventory and lead times are reduced via leveled production.

The production sequence can be adjusted quickly based on demand changes.

Benefits of Heijunka

Implementing Heijunka can provide several important benefits for a manufacturing facility:

Inventory and Waste Reduction

By leveling production and aligning it closer to actual demand, Heijunka enables facilities to significantly reduce finished goods inventory and work-in-process (WIP).

Lower inventory levels free up cash flow and storage space. It also reduces the risk of obsolescence, damage, and other inventory-related waste.

Smoother production with smaller batch sizes also minimizes overproduction waste.

Improved Flow and Stability 

Heijunka balances workload across production which minimizes bottlenecks. This improves workflow and continuity of operations.

There is less stop-start of production lines with better sequencing of diverse products. Takt time provides a steady, consistent production pace leading to greater stability and predictability.

There is less strain on processes, resulting in fewer defects and disruptions.

Adaptability and Predictability

The production scheduling and sequencing process in Heijunka lends well to adapting to changes in product mix or demand dynamically.

The system can quickly adjust to demand spikes or dips without overburdening capacities. There is greater synchronization of operations with the pace of actual orders.

This leads to enhanced predictability in meeting changing customer needs.

By reducing unevenness and overburden, Heijunka builds in flexibility and agility to swiftly address demand fluctuations.

At the same time, level loading of orders enables disciplined, standardized work with minimal variability in process lead times.

This combination of responsiveness and consistency is a key advantage of Heijunka.

Challenges and best practices

Implementing heijunka can be challenging as it requires changes in production planning, scheduling, and control. However, with continuous monitoring and optimization, its benefits can be fully realized.

Change management

Shifting from batch production to level scheduling requires change management across the organization.

Employees accustomed to working in batches may resist moving to smaller lot sizes initially. Clear communication about objectives and benefits is vital. Providing training and incentives further aids adoption.

Continuous monitoring 

After implementation, heijunka boxes and production flows need regular monitoring to quickly identify deviations.

Control charts and visual performance indicators help to rapidly flag issues for corrective actions. Daily Gemba walks by managers also foster real-time problem solving.

Shopfloor optimization

As takt time and product mix variety changes, the shopfloor layout should be continually optimized.

Bottleneck identification through value stream mapping coupled with 5S for organization and standardization enables efficient material and information flows.

Reducing changeover times through SMED further builds flexibility to seamlessly switch production between product families.

Implementing heijunka requires concerted efforts across planning, engineering, production, quality control, and maintenance functions.

With cross-functional involvement and continuous monitoring, it can transform operations to be more flexible and efficient.

The long-term benefits of stability, lower inventories, and improved flow justify the initial challenges involved.

Comparison with other methods

Heijunka differs from some other popular production scheduling methods like just-in-time (JIT) manufacturing and batch production.

Understanding these differences allows manufacturers to choose the right approach for their needs.

JIT manufacturing

The just-in-time (JIT) production system focuses on pulling inventory based on actual demand rather than pushing unneeded inventory to the production floor. This helps eliminate waste.

Heijunka and JIT share some similarities in their goals to smooth production flow and reduce waste through inventory reduction. However, JIT systems often struggle with demand variability and spikes. Heijunka production leveling is more effective for these scenarios.

While JIT aims to meet demand just as it comes in, heijunka works to level demand first. This makes production volume and mix more predictable despite changes or fluctuations in customer orders. Smoothing these peaks and valleys makes it easier to sequence diverse products and standardize workflows.

Overall, heijunka offers better stability and consistency for product variety and volatile demand environments compared to strict JIT methods.

Batch production

Batch production involves manufacturing products in separate batches that move through various processes as a unit. This can improve consistency within batches but lead to longer changeover times and work-in-process (WIP) inventory buildups between processes.

Heijunka scheduling breaks production into much smaller, standardized batches called pitch. This balances workflow and allows mixed model sequencing so various product types can flow through shared processes flexibly without piling up.

While single-piece flow is ideal, small pitch batches keep inventory and lead times low while offering more flexibility than large batch production runs. Applying heijunka ensures smooth sequencing despite volatility from mixed models or demand shifts.

Parting Notes

Heijunka is a vital component of lean manufacturing that aims to level production and smooth workflow. By sequencing diverse product types and producing in small batches, heijunka eliminates overburden and waste.

Implementing heijunka requires grouping products into families, calculating takt time to set the production pace, and designing a repeatable production sequence. Using tools like the heijunka box visualizes scheduling to balance flow.

The benefits of practicing heijunka are immense. It lowers lead times, reduces inventories, minimizes waste, and allows an organization to reliably meet customer demand. Production levels out so that there is no overburdening or starvation of work.

However, realizing these benefits requires change management across the organizational culture. Workers have to adopt the heijunka way of thinking and leaders must promote level loading. Shopfloor processes need optimization to support small batches and sequenced production.

While related to JIT manufacturing, heijunka takes a longer-term view by sequencing diverse products instead of producing the same product repetitively. This builds flexibility and predictability to match the variety of customer demands.

Heijunka is a proven, effective approach for production leveling that smoothes scheduling bumps and unplanned variability. The outcome is an efficient, waste-free flow that allows an organization to excel at flexible responses to shifting customer needs.

Original Article: https://www.6sigma.us/manufacturing/heijunka-lean-manufacturing-lean-six-sigma/