Solving the NDT Bottleneck at SIFCO Forge
SIFCO Forge’s NDT operation had turned into a real bottleneck, disrupting other parts of the operation. Through the application of JobshopLean techniques, changes in facility layout, cellular manufacturing, material handling and shop-floor logistics have helped eliminate the problem and saved some money in the process.
SIFCO Industries was founded in Cleveland, Ohio, in 1913. During the past 100 years, the company has become a leading global supplier of forged products for the aerospace, power-generation, marine and high-technology commercial markets. Their clients include Rolls-Royce, Pratt & Whitney, Sikorsky, Hamilton Sundstrand, Bell Helicopter and Goodrich Landing Gear.
SIFCO Forge formally engaged in continuous improvement activities in May of 2007 by launching SMART: Streamlined Manufacturing Activities to Reduce Time and cost. SMART utilizes all industry-proven continuous-improvement (CI) methodologies. The success of this program is supported by dedicated CI staff at the division and corporate level that provides leadership and ongoing opportunities for associates to participate. SIFCO regularly involves customers, suppliers and university students in improvement activities.
In 2009, the company implemented the theory of constraints (TOC) as a way to manage throughput and inventory in the facility. The Grind/NDT department was defined as the bottleneck operation at the beginning of fiscal year 2012. At this time, the department averaged about 5 days worth of inventory sitting at NDT and an additional 2-3 days of inventory waiting to go to the forge. NDT needed to reduce inventory and increase throughput in order to meet the organization’s plan for the year.
SIFCO Forges’s Nadcap-accredited, non-destructive testing (NDT) cell provides the non-destructive testing of forged products. It uses two methods to detect defects based on the material type: magnetic-particle inspection (mag/demag) and penetrant-dye inspection. The magnetic-particle inspection process consists of creating an energized field around a part to visualize surface indications. This process consists of different shots to ensure the magnetic field is present. At a minimum, all parts receive a head and coil shot. Penetrant-dye inspection is a controlled process that applies a dye activator to the surface of non-magnetic parts. This process consists of applying a penetrant die, emulsifier and finally a developer before going under a black light for inspection. Each method enables NDT to detect small surface defects inherent to the forging process that must be removed prior to additional forging steps or shipment to customers.
Removal of surface defects requires grinding and re-inspection of the part. Because the cracks are difficult to see and operators remove the least amount of material possible, the NDT process must sometimes be repeated multiple times. Inefficiencies in the physical layout of the NDT and grind operations required unnecessary product transportation, extra operator movement and waiting to complete the necessary tasks. Additionally, arrangement of the equipment within the NDT cell did not support Lean flow principles. This is because the department lacked proper material-handling equipment to support the creation of a U-shaped layout or the implementation of single-piece flow.
This arrangement resulted in a WIP (work-in-process) queue building up between the mag/demag and grinding workstations. Also, due to the high-mix, low-volume (HMLV) type of work, the imbalance between different workstations made it difficult for operators to work on the same part. Finally, the combination of insufficient floor space and high WIP inside the cell contributed to congested working conditions.
Background on JobshopLean and Smart Chart
From 2001 to 2008, the Defense Logistics Agency (DLA) funded The Ohio State University (OSU) to implement Lean in custom forge shops at a macro level. For that PRO-FAST project, the research and its application – JobshopLean – focused on facility layout, cellular manufacturing, material handling and shop-floor logistics.
Subsequently, between 2009 and 2013, the DLA funded OSU to implement Lean in custom forge shops at a micro level. For that FAST project, the research and its application – Smart Chart – focused on computer-aided methods to analyze workflow processes that occur “at and around” an individual workstation or a single manufacturing cell.
The first project to validate Smart Chart methodology was undertaken at the Columbus, Ohio, facility of Hirschvogel Inc., a global Tier-1 supplier to the automotive industry. Setup reduction on two cold-forging presses (one was manually loaded/unloaded whereas the other had a robotic arm) was the focus of the study.
As a result of the study, the setup time from start-to-finish was reduced from 125 minutes to 94 minutes (a 25% reduction). Also, the number of steps in a typical setup was reduced from 456 to 382 (a 16% reduction). Further, the total number of steps in any setup cycle was reduced from 1,167 steps to 797 steps (a 32% reduction). From an economic standpoint, since the forging press is the moneymaker for any forge shop, the freed-up capacity represented a potential increase in forgings output equivalent to an estimated annual sales increase of approximately $300,000.
Daily Workload Variations
It became obvious that the daily workload at the different workstations varied significantly because of the different routings of the forgings. This was due to the varied amounts of inspect-grind work content. Over a period of months, exhaustive work samplings and time studies were conducted by a cross-functional team of individuals, including DLA and OSU members. The team determined the durations of the grinding, mag, demag, inspection and paperwork steps.
The entire mix of forgings was divided into five part families based on forging size and routing. Using all of this data, a Line Balancing Tool (LBT) was developed that allowed managers to determine how many operators were needed for running the magnetic-particle booth and inspection during their shift. The LBT was a simple computer program written specifically for this project that focused on the best combination of operator and machine(s). The goal is to distribute a sequence of activities equally among a pre-specified number of operators so that each operator has about the same workload and the line can meet the desired production output. LBT permitted the team to apply industry-proven Lean manufacturing concepts.
The analysis provided by the cross-functional team helped to reduce inventory to three days and increase throughput in the department to meet the TOC objectives for the year. By implementing Lean methodologies to the flow of work, NDT was no longer the bottleneck in the process. In addition, the Production Flow Analysis and Simplification Toolkit (PFAST) software that had been developed for the JobshopLean project also came in handy for designing an efficient new cell layout. In the new layout, the mag/demag machines are aligned to eliminate staging and waiting when multiple shots were required. The installation of conveyors and a new bridge crane system allow one-piece flow because an operator can easily move parts with the proper material-handling equipment.
Since the beginning of fiscal year 2013, SIFCO Forge has been building on the initial gains realized above by using six-sigma methodologies to drive out variation in NDT. The department was tracking at less than 50% first pass yield (FPY) through magnetic-particle and penetrant inspection. The DMAIC (Define, Measure, Analyze, Improve, Control – part of the Six-Sigma Roadmap for improvement) process was used to identify the root cause for the low FPY. This enabled the SIFCO Forge team to implement additional improvements, including revised training, routing changes to standardize the flow and new standard work procedures. Since making the improvements, the FPY is now greater than 90%, inventory has been reduced to one day and overall productivity has improved by 5%.
The financial benefits achieved from this project are undisclosed for competitive reasons. However, SIFCO Forge has reported other advantages from implementing the recommendations provided by the OSU research team. These include:
• First-pass yield greater than 90%
• Inventory level at the NDT department is turned around in 24 hours
• Grind-department productivity has improved greater than 5%
• Zero accidents or near misses reported since implementation of the material-handling system
• Visual management of material flow
The FAST program is sponsored by the Defense Supply Center Philadelphia, Philadelphia, Pa., and the Defense Logistics Agency, Fort Belvoir, Va. This program is supported by the dedicated team of professionals representing the Forging Industry Association (FIA) and the forging industry. Together, this team will ensure that the nation’s forging industry is positioned for the challenges of the 21st
Dr. Shahrukh A. Irani is the director of industrial engineering research for Hoerbiger Corporation of America, Inc., Houston, Texas. He may be reached at 713-224-9015 ext. 2546 or at firstname.lastname@example.org. Amanda Lecy is manufacturing engineer at SIFCO Forge. She may be reached at 216-881-8600 ext. 1428 or at email@example.com. For more information about the FAST Program, contact Jon Tirpak, Executive Director, FDMC, at 843-760-4346. Learn more by visiting the official JobshopLean website at http://pfast.ise.ohio-state.edu/pfast/.