June 2007 - Using TPS Methods at Stolle Sidney

Lining Up for Quality

Stolle Machinery uses lean manufacturing methods throughout the organization to increase quality and control costs.  A prime example of this is the manufacturing cell at Stolle Sidney for the assembly of compound guns for Stolle Preferred Liners.  These guns were originally built one at a time by a single assembly person, which was cumbersome and prone to rework.  Some time ago this process was overhauled using manufacturing techniques that are part of the Toyota Production System (TPS).

To implement TPS methods in building liner guns, Stolle Sidney first created an assembly “cell.”  This U-shaped cell allows three builders (maximum of 5 for increased production) to work in an efficient sequence with the individual assembly procedures.  Special tools were developed to expedite assembly, and all tools dedicated to the cell are arranged and hung within easy reach of the builders on boards painted with the each tool’s outline.

Jason Davidson, the cell supervisor, explains, “These tool boards, called shadow boards, allow an assembler to quickly identify if any tool is missing from a station.  Only properly calibrated tools are used for gun assembly, and the tool boards help assure that we are using the right tools each time.”  The most efficient build procedures are recorded on clear, printed work instructions with photos and are posted at each assembly station for reference.  Additionally, all gun components with critical mating tolerances are manufactured by one dedicated source to ensure a proper fit.

The various parts are staged for quick access by the builders, and customized fixtures at each station hold the sub-assemblies to maximize speed, consistency and quality.  Each builder completes his procedures in 6-7 minutes (“takt time”) before passing it on.  The cell is operated as a “pull” system - each builder waits until the assembly he has just completed is picked up by the next person in the cell before beginning a new one.  This avoids any bottlenecks during a production run.

Two other important TPS techniques being used are:  poka yoke devices, and pulling the andon cord.  A “poka yoke” (POH-kah YOH-keh) device is an in-line quality inspection process between work stations that prevents a partially built gun that might be defective from continuing to the next work station.  According to Jason, “these devices can be as simple as a ‘go/no go’ gauge.  Each assembler can quickly inspect their work before any further assembly is started.  In the past, we would complete as many as 25 guns only to find all of them had to be disassembled and corrected for a problem from early in the process.  Now we can identify a problem immediately on just one gun and correct the process with almost no loss of time.  “Pulling the Andon cord” is another TPS concept.  Each assembler has been empowered to stop the line if they see a defective part being used in the assembly build. The net effect is that we’ve eliminated wasted hours redoing assemblies and improved the quality of the guns to our customers.  The process is now in control.”

According to Stolle Preferred Liner Product Manager Neil Zumberger, “Using the TPS methods and our assembly cell, we have reduced the old build time of 95 minutes per gun to less than 21 minutes per gun while increasing the quality by over 30%.  These methods not only help us control costs for our customers, but ensure that each gun meets our most stringent quality standards.”