All signs point to Kanban maintenance

Following these material-handling tips can support your plant’s move to lean manufacturing

By Douglas R. Malcolm

PlantServices.com

Kanban is a system for moving parts from one lean operation to the next using cards and containers. A translation of the Japanese word Kanban is “signal cards.” Materials and parts are delivered to the point of operation only when a signal is received to release the part to production or to signal upstream operations to build more parts for a downstream operation. The Kanban system is organized into a chain of processes in which orders flow from one process to the next downstream process.

This method allows components to be pulled through the system. In contrast, the old method of production was to push the product through the process to make enough products in case the customer was interested in purchasing something. Equipment failures caused excessive amounts of downtime and the push system produced large amounts of inventory that needed to be stored in warehouses and on production lines, which increased non-value-added costs.

The Kanban system may be simple, but it places undue stress on any plant maintenance and engineering department that isn’t prepared to address scheduled and unscheduled downtime. Minimizing this stress requires one to increase machinery and equipment operational availability, the measure of system readiness to produce when scheduled. Effective Kanban requires addressing scheduled and unscheduled downtime issues either by using design-for-reliability principles in the purchase of more reliable equipment or using design-for-maintainability strategies to make existing machinery and equipment more maintainable. Attacking downtime from either direction enables the production hardware to operate in a Kanban environment more effectively.

 

A five-point plan The plant maintenance and engineering department that lacks an effective plan for addressing downtime can use these five points to achieve greater maintenance excellence. It’s a process we developed and implemented successfully at many manufacturing locations. The program addresses critical points in deploying a comprehensive maintenance strategy for new and existing hardware in a Kanban environment. It concerns itself with: Data collection and analysis. Design for reliability and maintainability. PM/PdM/spare parts analysis. Life-cycle costs. Stability.

Dealing with data
The objective of the data collection and analysis step is an analysis of the hardware constraints. Pinpointing constraints helps base a reliability and maintainability plan on objective information that leads to informed decision-making. Establish the objectives and identify the type of data that needs to be collected from the plant floor. Obtain data by interviewing workers, querying the computerized maintenance management system and by standing around waiting for downtime to happen. The best floor-level data-gathering efforts use all three activities. It’s essential to glean data about failures and their causes during this step.

Interviewing maintenance personnel and operators can show what measures will reduce the effects of downtime. Unfortunately, you often get the individual’s opinions, not facts about downtime. The interviews are subjective and additional data collection might be needed.

The information obtained from the CMMS is only as good as the raw data residing therein. Most systems only collect data related to maintenance actions, not downtime events. The time shown on a maintenance ticket may not reflect the actual time needed to repair a failure or to conduct scheduled maintenance. The data collected from the CMMS must be filtered to obtain a focused picture of system downtime. Data also can be obtained from your maintenance shops. Having a technician record the time required to make a repair can provide information about necessary, but unscheduled, downtime events, spare parts requirements and scheduled PMs.

The best approach uses a data collector on the floor to monitor equipment operation and gather downtime information. Although costly, it provides the best results when data collection rules are established before Kanban implementation.

The data analysis can be as simple as histograms or Pareto charts listing the downtime events and the labor hours associated with each. Organize downtime into a Top 10 list to guide the activities of the next step.

Improve designs
Low operational availability numbers are a sure sign of impending Kanban system death. Use the data you collected and analyzed to develop a reliability and maintainability plan (R&M) that reduces unscheduled downtime, the number of preventive maintenance interventions and your spare parts inventory. Don’t forget to develop R&M plans for new equipment, as well as existing equipment, to be integrated into the Kanban system.

Before ordering new equipment or machinery, put an aggressive R&M engineering strategy in place to design out potential downtime. Remember, any hardware operating in a Kanban environment must be available when scheduled. It’ll be difficult to obtain desired throughput levels if operational availability is less than 95%.

Machinery designs ought to improve overall reliability. An improvement concept called design for reliability replaces weak design elements with more reliable components. Another way to improve the overall operational availability is to design for maintainability. Addressing these issues early reduces the cost of ownership and makes the Kanban system a cost-effective solution to reducing overall operating costs.