Rath Gibson is a manufacturer of precision engineered tubing made from stainless steel, nickel alloy and titanium. Its products range in diameter from 0.0625 inch to 8 inches with wall thicknesses ranging from 0.010 inch to 0.225 inch. The corporation has three manufacturing facilities in the United States: Janesville, Wisconsin; North Branch, New Jersey; and Clarksville, Arkansas. All of these facilities feature high precision forming/welding mills that transform flat coiled material into tubing that can be either coiled or delivered in straight lengths. Each division is committed to the philosophy of lean manufacturing as a means of achieving “world-class manufacturer” status.
Rath Gibson’s most recent challenge was to reduce what has traditionally been lengthy mill change-over times. Each mill can be configured with a wide variety of tooling and equipment to form, weld, size, anneal, polish, finish, test and cut the tubing. All change-overs require modifying something on the mill, while some change-overs require modifying everything.
Recently, the North Branch facility conducted a Single Minute Exchange of Die (SMED) event to identify opportunities for improving the change-over time on one of its critical mills. SMED is a technique used for highlighting any wasteful activities occurring during the change-over and either eliminating, reducing, streamlining or combining those activities to reduce the amount of time any machine must be stopped.
Machine operators and assistants; engineers; mechanics; and managers who were most familiar with the change-over process formed a SMED team. Ensuring that the team included representatives from different shifts provided a broader scope of experience.
The team started by listing all of the tools, supplies, equipment and documentation needed for a change-over that could be prepared in advance. The first objective was to take whatever steps were necessary to ensure that these items were prepared before a change-over ever began. The team agreed that it needed some type of SMED cart to hold all of these items and eliminate the “go and get” activities common to prior change-overs.
Next, the team listed all the activities that could potentially be involved in a change-over. With the idea of “envision the perfect outcome,” each team member was asked to offer an opinion about the change-over time they thought the mill was capable of accomplishing. The answers varied greatly, but were all considerably shorter than prior change-over times.
With all change-over activities listed, the team set out to place them in the most logical order, based on dependency on other steps and time required to complete the steps. It appeared that many of the activities could be performed in parallel (given the proper resources), as they were not dependent on other activities. The bottleneck activities were addressed first and staffing levels determined.
After determining the sequence of activities and staffing levels for each, the team planned to complete an extensive change-over the following day. Change-over tasks were assigned to all team members, and the SMED cart was loaded.
When the change-over began, actual times for all activities were recorded and “surprises” were noted. Engineers and others who would not normally have been involved in a change-over witnessed first hand some of the problems and were able to develop some creative solutions “on the spot.” This “extensive” change-over, which had previously taken almost 30 hours, was finished in 3.5 hours. Although more people were involved in the change-over, they were not required for the entire change-over. For example, four people were assigned to one task that had taken as many as 20 hours in the past. Two of the four were finished in approximately 1 hour; the other two were finished 30 minutes later. This alone reduced machine downtime by 18.5 hours.
By using SMED techniques, Rath Gibson’s North Branch facility has demonstrated what is possible on a mill change-over and is now prepared to make that possibility a reality. As Plant Manager Vic Bove says, “Now that we have established a standard work procedure for all mill change-overs, our biggest challenge is to propagate this practice to all of our mills as well as other areas of our manufacturing operation. We will continue to learn with each change-over and always strive for continuous improvement.”