Holley Performance Products Builds a Leaner Carburetor
Air Academy Associates’ SPC XL software
For the first wave of lean Six Sigma projects at Holley Performance Products of Bowling Green, Kentucky, it made sense to direct attention to the cornerstone product in the company’s portfolio: the carburetor. This is the product that launched the company back in 1903 and remains its highest-volume and most recognized product today.
Main-body machining was chosen as an area of focus for this project for a number of reasons: It is the largest component within the carburetor assembly, requires the most machining operations, is the most complex to cast, and serves as the mounting point for many other components. In addition, the manufacturing area was plagued by a number of problems. The process utilized many old, worn-out, manual machines and was labor-intensive. The long changeover time for all of the machines was a huge problem due to the high product mix (approximately 90 part numbers) and small lot sizes (as few as five pieces). The process also generated significant scrap/rework due to variation.
As a first step, the team created an input-process-output diagram. The process outputs that required improvement were documented. Next, the team determined the process inputs that directly affect those outputs, which ensured that everyone understood what was required to achieve the desired outcomes.
The team then set the following improvement goals:
• Reduce labor requirement by 50 percent.
• Improve departmental first-pass yield from 96 percent to 99 percent.
• Improve the process capability index (Cpk) for all critical-to-customer measurements to 1.5.
• Reduce changeover time from 90 minutes to 15 minutes.
• Make the process robust to frequent and significant product design changes.
The team used quality function deployment to help decide which solution had the most effect on internal/external customer satisfaction. This activity clearly documents what the customer wants. It creates a score for each possible solution with regard to how effectively that solution will increase customer satisfaction.
Baseline capability data were gathered for two features on the part. The team chose these features because they were thought to be problem areas. Statistical analysis on the data sets was performed using SPC XL software from Air Academy Associates of Colorado Springs, Colorado. The Cpk for each of these features was a negative number. Fortunately, the effect of this process variation did not reach the external customer. It did, however, affect internal customers. It was necessary for the assembly and flow- calibration departments to make adjustments to compensate for the variation. This resulted in waste because the assemblies required additional labor further down the value stream.
The team gathered baseline first-pass yield data for the previous ten months. The previous departmental target was 98 percent with the process running at a 96-percent average. The new goal was 99 percent.
The team then documented baseline data for departmental direct labor, overtime spending, and changeover time for the previous 12 months, and then created process maps and value-stream maps to show the flow of material through the process, along with the total distance traveled and total wait time. A fishbone diagram was used to more closely examine the causes of excess labor within the existing process. This allowed the team to ensure that all potential causes of wasted labor were eliminated from the new process.
Based on the data and analysis, the team completely reengineered the process utilizing three horizontal machining centers plus one ultrasonic aqueous parts washer.
The team took additional steps to design fixtures that allow for a completed part with every cycle and rapid changeover from family to family, and that require no changeover within product family. The program also specified robust tooling solutions to yield long life, low cycle times, and high part quality. Advanced Macro B computer numeric controlled programming was used to standardize across part families, error-proof the changeover process, and allow streamlined response to part-design changes.
Standard operating procedures were created throughout the new cell, and performance metrics were created to track performance and gains.
Many think of lean Six Sigma as only applicable to projects requiring intensive use of statistical analysis and the use of advanced tools, including design of experiments. However, the define, measure, analyze, improve, and control methodology is applicable in a variety of scenarios. It instills an overall mindset of attacking waste and variation throughout a value stream, provides a semistructured approach to project selection and management, helps the team identify key drivers of waste and variation, and ensures that gains are documented and maintained.
Air Academy Associates’ SPC XL software
- Captures capability data on processes
- Specifies solutions to increase efficiency
- Helps create standard operating procedures and performance tracking
www.airacad.com |
