Rubber is one of Nike’s biggest manufacturing waste streams and waste-related carbon driver. The suppliers that produce Nike footwear products collectively generated more than 20M KGs of rubber waste in FY22, 90% of which is petroleum-based synthetic rubber. The biggest driver of this waste stream is flashing – the excess material that gets trimmed off the edges of molded outsole components. As part furthering their sustainability strategies, Nike and China-based supplier Stella International collaborated on a project in 2021 to reduce rubber flashing 10% using proven Lean methodology.
This project focused on a single model, the Air Jordan 5, and used a cross-functional, data-driven approach to systematically identify, prioritize and resolve the most significant root causes of rubber flashing waste. The project team was led by the factory’s Rubber Manufacturing Manager and included rubber manufacturing, tooling, engineering, quality management and sustainability specialists.
The team started by establishing baseline metrics and setting a reduction target. Metrics included the product gross weight, flashing weight and flashing rate for a range of foot sizes. The flashing rate is the flashing weight as a percentage of the total rubber input weight per pair.
Next, the team diagnosed the root causes of the flashing. This entailed carefully observing the molding process, outputs and sources of flashing, then brainstorming potential causes of the largest concentrations of flashing observed. For each observed source of flashing, the team asked what caused it until they got to the root causes. Initial observations were organized into categories as shown in the graphic below and prioritized based on the team’s collective assessment of which were likely the most significant waste drivers.
The team then identified, tested and measured the effect of improvement measures for each root cause. The table below shows examples of problems observed and the associated root causes and improvement measures.
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Problem Observed
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Root Causes
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Improvement Measures
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Too much preform residue in mid-plate pressing
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No standard for residue cleaning
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Standardize mid-plate pressing operation
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Leakage of toe sidewall
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Old mold and worn flashing groove
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Mold maintenance
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Not full-size preform cutting die
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Full-size and half-size share the same cutting die
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Match cutting die to half size
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The next steps planned after this project are:
• Capture real-time flashing data by model and shift to drive continuous improvement
• Improve preform loading weight consistency
• Add flashing rate into mold operators’ performance evaluation
(The above content is provided by the brand, and the authenticity of the data is the responsibility of the brand. This article has both Chinese and English versions. If there is any inconsistency, the English version shall prevail.)