Case Study: 

Perfection Wheel Capacity Management

Background and Purpose

Perfection Wheel is a wheel re-finishing company based in Huntington, Indiana. In 2020, Perfection Wheel came under new ownership who hoped to augment their current product catalog with re-finished wheels as well. For nearly three years, Perfection wheel worked with new ownership to improve their daily output of the Huntington facility, but remained stuck at a mediocre output. Even despite capital investments in new infrared heat treatment ovens, the facility was only producing 232 units per day, about 120 units below their targets.

In September of 2023, Perfection Wheel partnered with MPCS to diagnose the capacity issues in the facility and increase its daily output. MPCS proposed to do this through conducting an extensive current state analysis of the facility's operations, identify key bottlenecks, and recommend corrective actions to increase throughput and improve the facility's operations.

Goals and Objectives

Once at the facility, MPCS developed a list of several goals for the project. These broadly fit into two categories: Assessment and Improvement.

The goals of the Assessment phase of the project included:

1. The categorization of products into product families.
2. Determine the product mix based on the product family categorization.
3. Map product flow through the facility, and work in process (WIP) inventory.
4. Determine capacity at each work cell in the facility.
5. Determine facility bottlenecks.

One of the most important considerations of this project is the enormous complexity of Perfection Wheel's operation. The wheel "cores" have already been manufactured and enter the facility and very different conditions, requiring different levels of care and time to re-fabricate them. Moreover, the facility handles all kinds of Original Equipment Manufacturer (OEM) brands and sizes, so different wheels will have different specifications and workflows through the facility. All of this must be considered to create recommendations that are accurate, realistic, meaningful, and impactful.

The goals of the improvement phase of the project included:

1. Propose an optimal product mix for the facility.
2. Propose measures to de-bottleneck the facility.
3. Propose WIP inventory buffer levels.
4. Propose other operational improvements.

Workflow Analysis

MPCS mapped the workflow through the facility. This resulted in the identification of 51 unique process steps across 21 unique work cells. Based on these workflows, the products were categorized into 12 unique product families.

Buffers

Within the workflow analysis, MPCS also calculated the buffer inventory for each work cell, this is amount of WIP between work cells that ensure a smooth operation and prevent work cells from shutting down because of lack of product. Conducting this analysis, MPCS identified that 2 buffers had under one hour of inventory between work cells! This posed a high risk of slowing and shutting down work cells for lack of material causing productivity losses and sending downstream ripples through the system. 

Capacity and Bottlenecks

Next, MPCS conducted a full capacity analysis. The capacity analysis considered many aspects of each work cells operation including:

1. The work cell cycle time
2. The amount of throughput (number of wheels) for each cycle.
3. The staffing levels of the work cell
4. The number of machines available in each work cell
5. The product mix, and workflow



Of all these considerations, the most interesting is the product mix and workflow. As stated earlier, different product families have different workflows. What this means practically is that some product families must go through a particular process step (like heat treating) several times. Because of these complexities, the facility capacity and output is quite sensitive to changes in product mix.

After conducting the full capacity analysis, 4 bottlenecks were identified. These became the target of debottlenecking corrective actions in the final stage of the project.

Scenario Sensitivity Planning

Before attempting to prescribe changes to the operations itself, MCPS decided it was most prudent to adjust the product mix. Simply by adjusting the product mix to ensure that demand did not exceed some of the rigid machine capacity constraints was set to increase the output of the facility by 21 wheels per day. Likewise, the optimal mix also brought other bottlenecks within the theoretical capacity of the facility (though in practice, this wouldn't be achieved consistently).

Recommendations: Debottlenecking and work balancing

Based on the findings of the capacity analysis the following recommendations were delivered to the facility's senior management team.

Work Balancing:

The hand blast work cell was understaffed. This caused WIP to dry up for all downstream processes. And because this activity is one of the first activities in the workflow, and all wheels must go through this work cell, any delays at this work cell will be felt across the facility. Having employees split shifts between these work cells (or build to buffer levels) will eliminate this bottleneck.

Asset utilization:

The "Oven #1" work station was one of two new infrared heat treatment ovens that were recently purchased by Perfection Wheel. And yet, it had become the system bottleneck. It alone limited the number of wheels that could be processed. Yet, the old oven that was used prior to the purchase of these new infrared ovens was still operational. MPCS made the recommendation to use the old batch oven, with gross excess capacity, as an auxiliary. Even as little as 3 wheels every hour will loosen the facility bottleneck by 72 units per day!

Based on the capacity model, these recommendations, along with the optimal scenario recommendation were expected to deliver an increased output of 91 wheels per day, or an increase of 39%. Moreover, these results could be had without further major investment.

Recommendations: Other Operational Improvements

In addition to the recommendations aimed at increasing capacity through loosening operational constraints, MPCS also made several operational best practice recommendations aimed at improving the facility's operations even further.

5S

During the current state assessment opportunities for 5S were observed in the "straightening" area work cell. Workers were seen spending time looking for the correct tools and chucks to use in straightening and aligning the wheel cores. The expected time savings from this 5S initiative is 5 seconds, and would increase the work cell capacity by 51 wheels per day.

Facility Layout

The layout of the facility was found deficient in several areas work cells. One such example was located in the hand blasting station, WIP storage racks were placed deficiently. The operator was required to walk to the rack in order to retrieve and store each wheel. Simply by moving the location of the storage racks, Perfection wheel was able to speed up the hand blast cycle time by 12 seconds, 17 wheels per day.

Inventory Buffers

Earlier, it was mentioned that in the current state analysis, MPCS found issues with 2 workflow buffers. These buffers were too low and created production slow downs and stoppages. Worse, these stoppages were intermittent, and without warning.

MPCS developed limits to WIP buffers for both the hand blasting and straightening work cells. This allows the front line employees to effectively manage inventory levels and manpower without thinking extensively about rest of the operation.

Results

By November 2023 the facility was consistently achieving over 350 units per day, an increase of over 50% . This was due to the facility capacity analysis and recommendations. The analysis and recommendations also allowed the facility to loosen some of the identified constraints even further. By changing processing temperatures of the two heat treatment ovens, the facility was able to gain added flexibility and achieve greater output.

Conclusion

Perfection Wheel is a great case example of the expertise and effectiveness of MPCS. Through thorough current state assessment and analysis, MPCS was able to deliver insights and recommendations that allowed Perfection Wheel to increase output by over 50% and finally begin to achieve their operational goals.