In today’s competitive manufacturing landscape, the ability to produce multiple product variations on a single production line has become a critical capability for businesses seeking to meet diverse customer demands while maintaining operational efficiency. Mixed model production represents a sophisticated manufacturing approach that enables companies to optimize resources, reduce inventory costs, and respond rapidly to market changes. This comprehensive guide will walk you through the essential steps of implementing mixed model production in your facility.
Understanding Mixed Model Production
Mixed model production is a manufacturing strategy where different product variants are assembled on the same production line in an intermixed sequence. Unlike traditional batch production, where one model is produced in large quantities before switching to another, mixed model production allows for the simultaneous manufacturing of various products based on actual customer demand. You might also enjoy reading about How to Use Plackett-Burman Design for Efficient Process Optimization: A Complete Guide.
This approach emerged from the Toyota Production System and has since become a cornerstone of lean manufacturing principles. The fundamental objective is to create a flexible production environment that can accommodate variety without sacrificing efficiency or quality. You might also enjoy reading about How to Use Shewhart Control Charts for Quality Improvement: A Complete Guide.
Benefits of Mixed Model Production
Before diving into implementation, understanding the advantages of this system will help justify the investment required for transition:
- Reduced Inventory Costs: By producing to actual demand rather than forecasts, companies minimize finished goods inventory and associated carrying costs.
- Improved Cash Flow: Lower inventory levels free up working capital for other business investments.
- Enhanced Flexibility: The ability to quickly adjust production mix enables rapid response to market fluctuations.
- Shorter Lead Times: Customers receive products faster since manufacturing aligns with real-time orders.
- Waste Reduction: Overproduction, one of the seven deadly wastes in lean manufacturing, is significantly minimized.
Step 1: Assess Your Current Production System
The first step toward implementing mixed model production involves conducting a thorough assessment of your existing manufacturing processes. Document your current batch sizes, changeover times, production sequences, and inventory levels. This baseline data will serve as a reference point for measuring improvement.
For example, consider a furniture manufacturer currently producing three chair models (Model A, Model B, and Model C) in batch production. Their current weekly production might look like this:
- Monday to Tuesday: 500 units of Model A
- Wednesday to Thursday: 300 units of Model B
- Friday: 200 units of Model C
This approach requires significant finished goods inventory since customer orders arrive daily for all three models, but production only runs each model once per week.
Step 2: Standardize Work Processes
Standardization is the foundation of successful mixed model production. Every workstation must have clearly defined standard work procedures that operators can follow regardless of which product variant is being produced. This consistency ensures quality remains constant across all models.
Create detailed work instructions that include:
- Precise task sequences for each product variant
- Standard cycle times for each operation
- Quality checkpoints and criteria
- Tool and equipment requirements
- Visual aids and error-proofing devices
Using our furniture manufacturer example, standardized work would ensure that whether an operator is assembling Model A, B, or C, they follow consistent quality standards, safety protocols, and efficiency practices.
Step 3: Calculate Takt Time and Production Sequence
Takt time represents the rate at which products must be completed to meet customer demand. This calculation is fundamental to mixed model production planning.
Takt Time Formula: Available Production Time / Customer Demand
Let us assume our furniture manufacturer operates 8 hours per day (480 minutes) with two 15-minute breaks (450 minutes available production time). Weekly customer demand data shows:
- Model A: 250 units per week (50 per day)
- Model B: 150 units per week (30 per day)
- Model C: 100 units per week (20 per day)
- Total daily demand: 100 units
Daily Takt Time: 450 minutes / 100 units = 4.5 minutes per unit
This means the production line must complete one chair (regardless of model) every 4.5 minutes to meet customer demand.
Step 4: Design the Production Sequence
With takt time established, the next step is creating an optimal production sequence that evenly distributes product variants throughout the day. This sequencing prevents the buildup of work-in-process inventory and maintains steady workflow.
For our example, the ideal sequence ratio would be 5:3:2 (Model A:Model B:Model C). A practical daily production sequence might look like this:
A-A-B-A-C-A-B-A-A-C (repeating pattern)
This pattern ensures all three models are produced multiple times throughout the day rather than in large batches, enabling the manufacturer to ship complete orders daily rather than weekly.
Step 5: Reduce Changeover Times
Quick changeover capability is essential for mixed model production success. Traditional batch production tolerates long changeover times because they occur infrequently. Mixed model production requires rapid transitions between product variants.
Implement Single-Minute Exchange of Die (SMED) methodology to reduce changeover times:
- Separate internal activities (must be done when the line is stopped) from external activities (can be done while running)
- Convert internal activities to external wherever possible
- Streamline remaining internal activities
- Document and standardize the changeover process
If our furniture manufacturer currently requires 45 minutes to change from one chair model to another, SMED techniques might reduce this to under 5 minutes, making frequent model changes economically viable.
Step 6: Implement Level Loading (Heijunka)
Level loading, or heijunka, involves smoothing the production schedule to distribute work evenly across the planning period. This practice prevents peaks and valleys in workload, reducing stress on workers and equipment while improving quality.
Rather than producing all units of Model A on Monday simply because a large order arrived, level loading distributes this order across several days while maintaining the established production sequence. This approach stabilizes resource requirements and prevents overtime or idle time.
Step 7: Establish Pull Systems and Kanban
Mixed model production functions optimally when integrated with pull-based material replenishment systems. Implement kanban cards or electronic signals to trigger material delivery to the production line only when needed.
For each chair model, calculate the appropriate kanban quantity based on usage rate, lead time, and desired safety stock. This system ensures that materials for all product variants are available without excessive inventory accumulation.
Step 8: Train Your Workforce
Successful implementation requires comprehensive operator training on multiple product variants. Cross-training enables flexibility in workforce assignment and ensures production continues smoothly regardless of absence or workload variation.
Develop a skills matrix documenting each operator’s competency across different models and workstations. Establish ongoing training programs to continuously expand capabilities and reinforce standard work adherence.
Step 9: Monitor and Continuously Improve
After implementation, establish key performance indicators (KPIs) to measure system effectiveness:
- Inventory turns
- On-time delivery percentage
- Changeover time
- First-pass quality rate
- Overall equipment effectiveness (OEE)
- Takt time adherence
Conduct regular gemba walks to observe actual conditions on the production floor. Encourage team members to identify problems and participate in continuous improvement activities.
Common Challenges and Solutions
Implementing mixed model production presents several challenges. Quality variations between models may emerge initially, addressed through rigorous standardization and error-proofing. Material shortages can disrupt the sequence, requiring reliable supplier partnerships and appropriate safety stock. Resistance to change among staff is natural, overcome through clear communication about benefits and involving team members in the implementation process.
Measuring Success
Return to your baseline assessment data after 90 days of operation. Our furniture manufacturer might observe inventory reduction from 10 days of finished goods to 2 days, lead time decrease from 5 days to 1 day, and improved on-time delivery from 85% to 98%. These metrics demonstrate the tangible value of mixed model production.
Taking Your Manufacturing Excellence to the Next Level
Mixed model production represents just one component of a comprehensive lean manufacturing system. The principles, tools, and methodologies required for successful implementation align perfectly with Lean Six Sigma training curricula, which provide structured approaches to operational excellence.
Understanding concepts like value stream mapping, waste elimination, statistical process control, and continuous improvement frameworks will dramatically enhance your ability to implement and sustain mixed model production. Professional certification programs offer hands-on experience with real-world applications, case studies, and expert guidance.
Enrol in Lean Six Sigma Training Today to gain the comprehensive knowledge and practical skills necessary to transform your manufacturing operations. Whether you are beginning your continuous improvement journey or seeking to advance existing initiatives, certified training provides the framework, tools, and credibility to drive meaningful change. Invest in your professional development and your organization’s future by taking the next step toward operational excellence through structured Lean Six Sigma education.
