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Total productive maintenance

Sep 1, 2008 12:00 AM


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Making equipment as efficient and profitable as possible. That's the premise behind total productive maintenance (TPM), a lean manufacturing strategy that optimizes preventive, corrective and predictive maintenance. Seichi Nakajima, a mechanical engineer, is credited with integrating preventive maintenance (PM) and total quality management (TQM) to create TPM. TPM uses small teams to achieve zero breakdowns as well as zero defects.

A TPM strategy calls for participants to concentrate on eliminating equipment losses. All equipment losses are categorized into three areas: availability, performance and output quality.

Equipment availability

This is the time equipment is scheduled for production, less downtime. Key issues here include failure and downtime (breakdowns and unscheduled stoppages) as well as equipment set up (makeready and changeover).

Equipment performance

These are losses incurred when equipment is in production and running mode, or the difference between the equipment's factory optimum output per hour vs. its actual production per hour. Look for production losses resulting from equipment idling and minor stops or reduced running speeds.

Equipment quality

This category covers defective product, including the cost of raw materials and processing time for products that customers reject and refuse to pay for. Keep an eye on defective products (and attendant production waste and spoilage) as well as equipment startup yield — start-up waste and spoilage that occurs after makeready or changeover is complete.

TPM provides an effective and realistic program to address these equipment losses. Preventive maintenance (PM) is the most familiar maintenance activity for most printers. As the name implies, it prevents losses, resulting in better equipment availability and performance. PM requires knowledgeable operators and technicians who understand equipment's operating components, structured scheduling and the discipline to adhere to standards and procedures.

Team-based autonomous maintenance

PM is essential, but to achieve zero equipment failures and breakdowns, you have to take things a step further. Autonomous maintenance relies on a small team approach. Equipment operators and maintenance staff work together — equipment operators basic cleaning and lubrication duties, for example, are expanded to include an inspection step. The operators essentially are acting as the eyes and ears of the maintenance department. Autonomous maintenance must be implemented in all departments, from prepress to postpress.

Autonomous maintenance teams determine training needs and the necessary equipment “critical cares.”

Critical cares are the maintenance tasks and activities required to maintain proper equipment conditions. Examples include cleaning, lubrication, inspecting for abnormalities, making proper component adjustments and settings and maintaining manufacturer specifications.

Cleaning

Implementing proper cleaning procedures and techniques during planned maintenance ensures equipment components and parts work effectively and, in some cases, reveals abnormalities that will result in imminent failure. It doesn't require much more time than is typically allotted for preventive maintenance. Cleaning all sections and surfaces of equipment removes dirt, dust, water and other contaminations that can cause increased friction, abrasion, reduced cooling, feed-line clogging, constrained mechanism movements and electrical components failures.

Lubrication

Properly lubricating equipment reduces chronic and sporadic failures. Neglecting lubrication causes mechanical seizures, accelerated parts deterioration and abnormal overheating of components. Apply the correct type and amount of lubricant — newer equipment may require a different lubricant than older equipment, even if the manufacturer is the same. Cheaper lubricants may not meet OEM requirements for maintaining basic conditions.

Use the correct tools. Ensure the correct type of grease guns is used and that it works properly.

Apply the proper amount of grease — various grease fittings on the same equipment may require different amounts of grease.

Check with the manufacturer for equipment lubrication, lubrication tools and auto-lubrication systems operation. Confirm that automatic lubrication systems are operating properly.

Inspection

Inspecting operating mechanisms and components helps eliminate equipment failures and breakdowns. If specific equipment component inspections are included as part of the cleaning process, hidden problems — loose bolts, worn out adjustment brackets, play in grippers and gripper bars, poor roller conditions and settings, abnormal anilox chamber leaks, uneven and excessive pressure settings, tapes and belts deterioration — can be revealed.

Prepress inspection items include CTP laser accuracy, damaged or deteriorated vacuum lines and seals, processor equipment operation and plate punch square.

Loose connecting parts can cause abnormal vibrations and premature deterioration. Operators should record any abnormalities in maintenance/operation logs and maintenance request forms.

Specifications

The equipment manufacturer and accepted best industry practices establish the specifications for proper equipment operation of. Proper equipment component settings will decrease adjustments, boosting makeready efficiencies. The ultimate goal for equipment make-ready and changeover is “first item good.” Proper plate making, true plate cylinder zero set and plate mounting accuracy on press will accelerate makeready and minimize equipment deterioration from excessive movement of machine components. Excessive equipment component pressure settings can place stress on bearings and bushings. Temperatures and humidity should be kept within manufacturer's recommendations, vibration must be within the limits of the equipment's design, and dust and powder contamination must be totally prevented. Again, major contributors to accelerated equipment deterioration and failures include high temperatures or frequent temperature variations, dust and spray powder contamination.

Factors that contribute to ineffective autonomous maintenance and poor equipment conditions include:

  • Inadequate training or education for staff, equipment management and operators.
  • Poor adherence to established maintenance standards.
  • “Fix-it-when-it-breaks” mentality.
  • Ineffective process control standards.
  • Improper maintenance tools and materials.

Stage One: What's the status quo?

Achieving an effective maintenance program involves a series of stages. Start by analyzing what you're currently doing and then create a desired state program. Here are some assessment questions to consider.

Are current equipment maintenance tasks and activities clearly documented? Do they meet factory specifications? Preventive, corrective and predictive maintenance tasks, activities, and frequencies must meet manufacturer specifications should strive to maintain the equipment at near designed capabilities. (Always consult the equipment manufacturer for its endorsement of PM tasks.) PM task and activities (AKA “critical cares”) should be written in language easily understood by those responsible for doing the work. Using a checklist form, will ensure the procedures are done sequentially and verified when complete.

Stage Two: Operators level of understanding

Do operators understand the preventive maintenance tasks and activities? Assess operators' competency in the established preventive maintenance tasks and activities. Can they explain each preventive maintenance task described in checklists? Have the operators demonstrate the relevant PM task on the equipment.

Typical operators' PM activities include periodic cleaning, accurate inspection, proper lubrication, re-setting and adjustment of components, and replacement of equipment filters and components that are subject to high degrees of friction and repetitive operations.

Stage Three: Tools and materials

Are maintenance equipment, tools, and materials ready for every scheduled maintenance initiative? Ensure that the correct tools and materials are on hand, are easily accessible and work properly.

PM tools and materials include documented PM task checklists, carts, cleaning brushes, solvents and applicators, grease, grease guns, oil and applicators, rags and extra bearings, filters, fasteners, and supplies.

Stage Four: Are current PM tasks done well?

Accelerated deterioration results from improper or inadequate cleaning, lubrication and inspection. Conduct periodic checks.

Stage Five: Is the maintenance staff proactive?

If the staff perceives its role to fix things when they break, implement process improvement training and team initiatives. Once you've improved your PM approach, you can add the operational aspects of the program via autonomous maintenance.

Stage Six: True equipment capabilities

Is your equipment currently at or near the manufacturers' designed capabilities? This may include printing test targets, heat and vibration analysis and increasing equipment speeds until minor stoppages occur or quality becomes unsatisfactory.

Stage Seven: Actual vs. scheduled PM time

Preventive maintenance activities are scheduled for specific lengths of time. But the amount of time needed to perform each PM task should be timed individually. Ask maintenance and production operators to observe, time and analyze PM activities. Determine value-added time (required for PM tasks) and non-value-added (wasted) time. Non-value-added PM time includes time spent searching for maintenance tools and supplies, determining who should do what, waiting on maintenance staff, machine operators watching (but not assisting), and breaks. Non-value-added time generally results from a poor planning, coordination and inconsistent PM procedures. Kaizen Blitz events can help reduce non-value added time.

Although evaluating maintenance processes might seem tedious and time consuming, it does not take as long as one would think and it will pay big dividends in decreasing downtime and quality problems.

Optimize TPM through Kaizen Blitz

Kaizen means “to change and make good” in Japanese. Kaizen Blitz fosters an atmosphere of continuous improvement and a sense of urgency. Focusing on one or two pieces of equipment, Kaizen Blitz events typically are four to five days in length. Kaizen events can target administration tasks, equipment makeready and weekly and monthly PM activities.

A weekly autonomous maintenance Kaizen Team Event requires a cross-functional team of managers, maintenance staff and process operators. Although all Kaizen team members have equal status during the event, management personnel are responsible for making costs decisions and providing any necessary resources.

Creating a current state process map

The Kaizen team creates current state weekly autonomous maintenance process map. Descriptions of each step in the current state weekly maintenance process and estimated times are recorded on different colored sticky notes and stuck on a flip chart or white board.

Candid camera confirmation

Analyzing a video of weekly preventive maintenance activities enables the Kaizen team to confirm the current state of the PM process. Operator and maintenance staff works together to determine non-value-added activities. The team validates current state process, agrees on current problems and identifies obstacles to overcome for improvement.

PM nirvana

The Kaizen team develops a desired state or optimized process. The team brainstorms to determine where non-value-added activities can be removed, solve problems and overcome obstacles. The team determines how much time will be needed for value-added procedures to improve preventive maintenance tasks and activities, creating a desired state process map with new estimated activities and times.

Validating the desired state process

The Kaizen team validates the optimized processes by actually performing the desired state weekly PM on the equipment. Each operator's preventive maintenance activities times are measured and recorded.

Keep it going

Communication, training and adherence to standards will help sustain optimized weekly PM. Develop verification mechanisms via periodic checks and assessments. Record and track weekly PM time efficiency and take corrective action if the time exceeds 15 percent above the standard. Kaizen Blitz events can achieve up to 60% time savings on the actual activities, let alone less unscheduled downtime.

Just do it

Performing effective equipment maintenance and truly optimizing autonomous maintenance tasks and activities reduces unscheduled downtime while saving hundreds of hours of scheduled maintenance annually. Lean manufacturing and TPM provides the guiding principles, structure, and methodology to decrease makeready and changeover time, reduce equipment downtime, improve quality, enhance performance and increase capacity.

Ken Rizzo is PIA/GATF's director of consulting, custom training and the Center for Lean Practices. Contact him at krizzo@piagatf.org.

Nix the big 6

TPM addresses six typical operational and mechanical losses:

  1. Sporadic and chronic equipment failure/ breakdowns. Sudden and unexpected sporadic breakdowns usually are infrequent and result from the deterioration of the mechanical and electrical operating components. Chronic breakdowns, which are the result of defects in equipment, tools, materials and operating methods, occur frequently, resulting in small amounts of lost time.

  2. Makeready and equipment adjustments. With shorter run lengths and more makereadies, reduction in makeready time and new job adjustments, emphasis is being placed on time-to-good counts.

  3. Equipment idling and minor stops. Material abnormalities and slight machine malfunctions that can be overcome by replacing materials or resetting press components.

  4. Reduced running speeds. While numerous reasons are advanced for running presses and bindery equipment at slower than rated speeds, less than label-speed operations represent a productivity loss.

  5. Defective product. Defective end products, for whatever reason, must be treated as a loss and, therefore, eliminated.

  6. Reduced equipment yield — start-up losses. Start-up loss is lost time after the makeready is complete and production sheets/signatures are being counted, but at a reduced speed. These losses generally are accepted as a process variable, but account for considerable productivity loss.

Are maintenance tasks and Activities performed effectively? It must be determined if each preventive maintenance task is performed effectively including proper cleaning, lubrication, and inspection of the press.

For further reading

AMERICAN Printer's “Quick Fixes” (July 2006) explains how programs from remote diagnostic programs from Air Motion Systems, Heidelberg, KBA, Komori, Mitsubishi and manroland are dramatically reducing press downtown.

“Good Housekeeping” (May 2007) profiled four plants than excel at preventive maintenance: Dickinson Press (Grand Rapids, MI), Edwards Brothers Inc. (Ann Arbor, MI), The Hennegan Co. (Florence, KY) and Williamson Printing Corp. (Dallas).

See it at the show

At PRINT 05, Heidelberg unveiled an extended service package: Systemservice 36plus, which extends service coverage for a period of 36 months with the purchase of a new press. Unlike a warranty extension, Systemservice 36plus has a preventive maintenance element — it is designed to help reduce unplanned press downtime while improving overall efficiency.

Customers must maintain the press according to weekly and monthly checklists furnished by Heidelberg. Maintenance training in is included, and after 10, 20, and 30 months, a visiting Heidelberg technician thoroughly inspects the equipment and makes adjustments as necessary.

Heidelberg's Graph Expo 2008 Systemservice highlights include eCall, an intelligent notification system which enables presses to automatically communicate impending service issues directly to Heidelberg, as well as partner program, which allows customers to build a custom service plan.