Unbalanced production lines waste both time and resources, directly reducing overall manufacturing productivity. In manufacturing, line balancing evenly distributes tasks among operators and machines to match production with customer demand.
Line balancing is a key component of the lean manufacturing approach, which focuses on continuous improvement over static performance to help companies make the most of their facilities, technologies and staff expertise.
A perfectly balanced production line improves efficiency, reduces bottlenecks and minimizes idle resources across the manufacturing process.
This guide explains what line balancing is, why it’s essential in modern manufacturing and how to implement it effectively in your own facility.
What is line balancing?
Line balancing ensures that work is evenly distributed across operators and machines.
Quantifying this distribution starts by identifying the rate at which goods or products must be produced to meet customer demand. Known as Takt time, this value is calculated by dividing the available working time per shift by the rate of customer demand over the same period.
For example, if the available working time per shift is 8 hours, or 480 minutes, and the average customer demand is 200 units per day, the Takt calculation is:
480 / 200 = 2.4
As a result, the optimal time to complete a task—also called cycle time—is 2.4 minutes.
With this data in hand, companies can compare current performance to Takt values. If production lines can only produce units once every 3 minutes, this means 160 units are produced per shift, 40 units lower than the Takt target.
Line balancing helps solve this issue by analyzing three key components: cycle time, idle time and workload balance.
- Cycle time
- Multiple workstations for the same part or product may have different cycle times. Consider the example above. If the company has three machines producing the same product with cycle times of 2.0, 2.7 and 4.3, respectively, this yields an average cycle time of 3 minutes.
- While reducing the cycle time of the second machine would improve production, the third machine is the outlier and suggests the ideal starting point.
- Idle time
- Idle time is a measure of how long a machine isn’t actively producing items during its active time. The higher the idle time, the more resources are wasted on power, cooling and staffing costs.
- Analysis of idle time helps identify potential bottlenecks in lean manufacturing environments.
- Workload balance
- Workload balance assesses the total amount of work required and how it is distributed across stations and machines. For example, companies may rely on newer or advanced machines more heavily for resource-intensive processes, in turn leaving other machines idle.
Why line balancing matters in manufacturing
Effective line balancing offers multiple benefits for companies, including:
- Improved productivity
- Reduced cycle times
- Minimized bottlenecks
- Lowered labor costs
- Enhanced product quality
- Increased adaptability
Common methods for line balancing
Line balancing has a singular goal: improving productivity.
There are, however, multiple methods to achieve this goal. Some of the most common methods include heuristic, mathematical and software based. Here’s a look at each in more detail.
Heuristic
Heuristic methods use logic and common sense to evaluate line balance.
For example, the largest candidate rule considers the “Te” value of tasks, which represents the time required to complete all work elements. Tasks with the largest Te values are assigned first, and this process continues in descending order until a workstation is at capacity. The rule is then repeated for the next workstation until all tasks have been assigned. Any excess capacity can be assigned additional tasks that help streamline future processes, such as the production of parts that are not immediately needed but may be required to manage demand spikes.
The ranked positional weights method, meanwhile, ranks each workstation based on its importance—or “weight”—to the manufacturing process. Higher-ranked workstations should be assigned skilled workers and be placed at the front of maintenance queues, while lower-ranked workstations should be evaluated for potential performance improvements.
Mathematical
Manufacturers can also balance lines using mathematical models such as linear programming or simulation tools. Here, the goal is to map key processes into mathematical equations or simple programs and then record the results. By changing input values and work distribution, companies can determine the optimal balance.
Software based
Software solutions allow real-time monitoring and provide visual dashboards to help manufacturers see how lines are performing moment to moment. This enables the granular adjustment of tasks to optimize production.
Manufacturers should also consider when it makes sense to use an automated approach versus manual operations. For example, if the goal is improving production efficiency across a single line composed of six simple machines, manual observation may be the simplest approach.
If companies are dealing with multi-part processes that include duplicate machines operating in tandem, meanwhile, automated processes are more efficient.
Challenges in line balancing
In a perfect world, line balancing depends solely on machine performance and throughput. By making observations and doing the math as needed, companies can find solutions to balancing issues.
In reality, however, things are not quite so simple. Common challenges in line balancing efforts include:
- Changes in demand and product mix
- Machine downtime or maintenance issues
- Variability in operator skill levels
- Unexpected supply chain disruptions
- High-mix environments with complex product families
Line balancing vs. other efficiency practices
As noted above, Takt time is a key metric for line balancing. Takt time identifies the necessary production pace, and line balancing aligns resources to meet this goal.
Lean manufacturing principles also rely on line balancing to reduce waste. Consider machine idle time—every minute that equipment is powered but not producing costs money. Line balancing helps reduce idle time and, in turn, limit waste.
Automation and line balancing work together to streamline processes and reduce waste. Effective task allocation is key. While automation improves speed, that speed is only effective when applied in the right place at the right time. Automating line processes that are already balanced won’t improve efficiency.
Put simply, line balancing plays a key role in overall operational efficiency. It’s not enough on its own, however—Takt time informs line balancing decisions, and when line balancing is applied as part of lean manufacturing, companies are better equipped to identify and eliminate waste.
Real-world examples of line balancing
So what does line balancing look like in practice? While the concept is straightforward—balanced lines improve efficiency—implementation isn’t always so clear-cut.
Here are two examples:
First up is Wheels Auto Parts, which recently expanded its manufacturing plant to accommodate automotive industry growth. Now, the company runs four assembly lines that create multiple part types. Measurement of Takt time versus actual output reveals that the company isn’t keeping pace with customer demand.
This leaves two options: Buy more machines and deploy a fifth line or look for ways to improve existing lines. Using heuristic and mathematical analysis, the company discovers that Line 1 and Line 2 are tasked with producing more complex parts on average than Line 3 and Line 4, leading to decreased throughput. By balancing these tasks across all four lines, the company can meet Takt goals without spending additional money.
Next is Ed’s Electronics, which produces components for desktops, laptops, tablets and mobile phones. Given the short release cycle of these devices, Ed’s is constantly changing its manufacturing process to meet evolving demand. To help ensure lines stay balanced, the company uses digital tools for real-time analysis and process improvements.
How to implement line balancing in your facility
Five best practices help companies effectively implement line balancing:
1. Assess current flows and identify bottlenecks.
2. Calculate Takt time and compare it to cycle times.
3. Reallocate tasks to streamline workloads.
4. Use software and simulations to validate improvements.
5. Partner with industry experts.
Key takeaways
Line balancing is a critical process for improving efficiency and reducing costs. Applied correctly, this technique helps create smooth workflows and prevent production bottlenecks.
But it’s not a standalone process. Instead, line balancing works best in combination with practices such as lean manufacturing and modern technologies such as CMMS tools and digital modeling solutions.
Ready to optimize your production lines? Contact ATS to discover how our experts help manufacturers improve efficiency through advanced line balancing solutions.
