If it ain't broke, don't fix it. Design and plant engineers are teaming up to rework that dubious adage. Stung by escalating life-cycle costs, they are discovering that a little attention paid to component design up front can smooth the fix when the break comes, as it inevitably will.
Design for service (DFS) has generally been perceived as a consumer-product-related strategy. However, DFS can also be used to improve design of machinery, manufacturing equipment, and production tools.
Have you looked under the hood of a car lately? Everything is packed in so tightly and efficiently, it is almost impossible to remove any particular part without removing all the adjacent parts. It is the same with the components in manufacturing plants and factories: The need--indeed, demand--for economic design has sometimes sacrificed serviceability by making it hard to get at individual parts for maintenance and repair.
"Build it so you can take it apart," is the golden rule for Richard Eaton, manager, facilities engineering, Hitachi Electronic Devices USA, Greenville, SC. "Designers should make something so that when it is installed, you can pull it out again."
According to engineering consulting firm Monroe & Associates, Troy, MI, conceptual design accounts for 4% of the cost of manufacturing a product and results in 70% of the total life-cycle cost. Studies at General Motors have shown that if you extend the definition of design to include product development (excluding materials and labor), this phase is 15% of the initial cost and influences 95% of the total life-cycle cost for machinery, manufacturing equipment, and production tools.
"Even though we don't make machine tools, GM spends billions of dollars on manufacturing equipment and related support and supplies every year," notes Tony Wojcik, senior project engineer, Delphi Interior & Lighting Systems, a division of GM. "If our engineers understand how their machines work, they will be in a position to influence designers to incorporate serviceability."
Wojcik's philosophy is to study a prospective machine during the design and development phase, before the machine is actually built. The purpose is to find ways to improve serviceability without compromising functional requirements, by doing such things as reducing the number of parts and fasteners; assuring ease of access; improving reliability; and simplifying designs.
The primary concern is not what's broke, but how long it will take to fix. Therefore, Wojcik says, it is important to identify and list those items that are repaired the most: "Rank the severity of each failure, how often it occurs, and how easily detected it is. Try to design parts so that anybody can fix or replace them." One of the key problems is that with all the myriad alternatives facing plant managers, they sometimes forget to look at the long-term cost. This is the conclusion reached by Joseph Greil, a plant engineering consultant in Greenlawn, NY. The amount of costs incurred for training and maintenance by following a policy of low-cost bids can be astronomical. Greil cites a study conducted by TRW that he was involved in some years back that indicates a 2% to 5% increase in parts-design expenditures up front can reduce lifetime maintenance costs by 25%.
"There is nothing particularly exotic about component design for serviceability," Greil says. "Design for the future, not the past. Design to minimize life-cycle cost."
Ultimately, the method plant managers use to acquire equipment is the most important factor OEMs consider when designing their wares, says Jim Iubelt, product marketing manager at Allen-Bradley Company, Inc., Mayfield Heights, OH. "The same people responsible for life-cycle cost are often not the same people responsible for acquisitions," Iubelt says.
Accessing the part is half the battle
You can't service or repair a piece of machinery if you can't easily get inside it. Beyond that, the longer it takes to get at the parts, the longer the machine is down, and downtime costs money.
Designing for assembly should solve that dilemma, right? Maybe not, say Nick Abbatiello, researcher at the University of Rhode Island, Kingston, RI, andPeter Dewhurst, co-founder of Booth-royd-Dewhurst, Wakefield, RI, makers of design-for-assembly software. For initial assembly, the goal in design is to minimize assembly time and cost. But when designing a product for service, inevitable conflicts arise between the different service tasks that must be performed on the product.
The perfect design for service, Abbatiello and Dewhurst say, would have all of the items to be serviced or replaced immediately accessible on the outside of the product. Since this is generally not possible, design engineers have to make tradeoffs so some items--those most likely to need servicing--will be easily accessible. After all, machinery in manufacturing is subject to long hours of operation and tough environments. Every product will need maintenance or service at some point.
|How to make servicing easy
- Ready interchangeability: Similar parts from different manufacturers should have common interfaces, fittings, and base mountings.
- Ease of installation: Parts should go in correctly aligned, with a minimum of fiddling. Furthermore, the number of tools required to do the job should be as few as possible.
- Error proof: Components should only have one correct way of going in. If it requires force, it's going in wrong.
- Proven track record: Vendors should take advantage of analysis tools on the market to provide reports on their components capabilities.
Some basics of accessibility
- Locate most frequently replaced parts on the outside.
- Place components so they don't block one another.
- Use fasteners and covers you can easily remove.
Design engineers should provide sufficient working space around components, says Tony Wojcik, senior project engineer at Delphi Interior and Lighting Systems, Troy, MI. That means ensuring that components don't block one another, and designing fasteners and covers for rapid removal and replacement, he asserts.
"Designers should take the repair-time challenge," prods Wojcik. "A typical tool changeover for extruder equipment may take between two and eight hours. Design the equipment today so changeover will only take one minute to repair tomorrow," he says.Many OEM suppliers are doing just that. For example, Penn Engineering & Manufacturing Corp., Danboro, PA, offers a self-clinching panel fastener assembly with a Phillips head to meet UL 1950 service-area access requirements. The Type PFC2PTM fastener promotes ease of assembly and quick panel removal without loose hardware because it is installed and used as a complete, spring-loaded assembly. Installation is accomplished by squeezing the fasteners into properly sized punched or drilled holes using any standard press.
A Phillips head enables the Penn Engineering PFC2P panel fastener to meet UL 1950 service-area access requirements. The fastener also promotes easy assembly because it is installed and used as a complete, spring-loaded assembly.
Southco Inc., Concordville, PA, offers a ratchet-action captive screw that is "hand on, tool off." Users need only a simple tool, such as a slotted, Phillips, or multi-lobe driver to remove the Sentinel screw. Installing it again, say to replace doors after servicing, is a hand operation. This eliminates the time and inconvenience of first finding the proper tool, and then using it to fasten each of the screws. The result: increased uptime and minimized service costs.
"Access is very important because we need the ability to check parts and do preventive maintenance," says Ron Kinsey, plant maintenance manager at Buckeye Florida, Perry, FL. "Obviously, design engineers should be thinking about reliability. Will this component run for a long time without requiring maintenance? But they should also focus on where components are placed. They should ask themselves: 'Can you get to the appropriate parts to monitor the component in preventive maintenance programs and to do the corrective maintenance when necessary?'"
Southco's Sentinel screw can be tightened by hand for quick installation and removed with a simple slotted, Phillips, or multi-lobe driver.
Adds Jerry McGuire, director of plant engineering, at Denso Michigan, Battle Creek, MI: "No matter how you look at it, accessibility has the most direct affect on repair time and quick identification of the problem."
Keep design simple
How many operations does it take to screw in a light bulb? In one case, more than two dozen. Yet a design-for-service study shows this could have been knocked down to four.
The example begins in the owner's manuals of some Chevrolet vehicles, which include instructions on how to change a bulb in a GM-10 Headlamp and Panel assembly. A person must perform no less than 28 operations, including the removal of 21 screws, plus the entire grille,to unscrew a light bulb. Peter Dewhurst, co-founder of Boothroyd Dewhurst, conducted a design-for-service evaluation on the assembly using Boothroyd Dewhurst's Design For Analysis (DFA) software, and reduced the number of operations in a hypothetical redesign to four.
As goes Detroit, so goes the nation. The automobile industry is a useful metric in gauging the state-of-the-art in U.S. manufacturing technology and techniques. So notes Dewhurst. "A major improvement in product serviceability would be beneficial to both manufacturers and their customers, however, it appears this is one aspect of product design that has not been improving," he says.
Analysis showed the headlight design illustrated here could have been simplified to enable quicker assembly and disassembly.
Dewhurst finds an extreme example in the use of spot welding during construction, coupled with the move to seamless body designs. "This makes the repair of even minor body damage prohibitively expensive, even though the event is an anticipated part of normal product use," he says.
Dewhurst faults the approach of most companies--wherein service reviews are conducted when the design has been fully executed--for this state of affairs: "An analysis of important service tasks should take place with the earliest design-for-assembly studies, and these should take place at the early concept layout stage of product design."
Dewhurst likens the current impact of service engineers at many manufacturers to pouring water on a campfire while the rest of the design team tries to keep the flames going. "The goals of ease of assembly on the factory floor and ease of subsequent service tasks can be closely aligned, provided they are considered together by the design team," he concludes.
Sprocket and belt design eliminates maintenance
Minneapolis, MN--Unlike most other disc-plate clutches, the ADAMTM clutch has special servicing features designed to save time and effort, says its maker, Tol-O-Matic Inc.
The ADAM clutch incorporates a two-piece, non-asbestos friction material that can be easily replaced without dismounting or disassembling the clutch. The material is in two semi-circular pads held to the friction plate by flathead screws. The screws are accessible through two access holes in the finned plate. To change the friction pads, the technician rotates the pilot plate to align the screws with the access holes in the finned plate. Once the screws holding the friction pads are withdrawn, the pads can be easily removed. Placing new friction pads on the pilot plate and replacing the screws finishes the job.
"The design virtually eliminates the downtime normally associated with the pad replacement process," says Todd Zarbok, sales support manager at Tol-O-Matic. "It turns a two hour repair job into a fifteen-minute preventive-maintenance procedure."
Panel designs enable easy access
Toledo, OH--When Owens Brockway needed to cool a new computer, the company knew that choosing the right air-conditioning unit was critical. Owens, which makes glass and plastic containers for consumer products, chose a 1S Pro-Ozone air conditioner from Rittal Corp., Springfield, OH.
"Being able to easily change parts without much downtime was important," says Steve Cisco, electrical engineer at the company. "And easy monitoring of the temperature was also key."
Interchangeable cover grills integrated into the unit provide the quick and easy access during maintenance that Owens desired. And an integrated microcontroller with touch-pad programming and a C or F temperature display option permits instant system analysis. Plus, the microcontroller can be integrated into a central computer system, enabling users to monitor the functions of many climate-control components at once, even from remote sites, to ensure reliable operation.
"The microcontroller technology enables us to set and view the temperature within the enclosure without having to open up the enclosure," explains Cisco. "And being able to connect the microcontroller to other systems to monitor the temperature is a big help. Smaller mid-size 1S air conditioners also aim to make servicing easier. The units feature front-vented panels that snap off for easy maintenance and replacement of filters. They offer simple temperature control through a standard built-in thermostat, as well.
Plant manager asks 'Can we talk?'
A. Wayne Weaver, Manager of Corporate Plant and Facilities Engineering, Dietrich Industries Inc., Hammond, MI
Design News: What are the primary serviceability concerns in your plant?
Weaver: We try to standardize on components such as hydraulic pumps and valves, dc drive packages, pneumatic controls, and in some cases even brands of gear boxes. We'll ask machine manufacturers to use parts that we consider standards for our manufacturing operation. Sometimes we are very successful with that, other times we get resistance because a manufacturer has a particular brand that he likes to use.
On occasion there are technical reasons for using a specific brand. Under those conditions we back off on the request for total standardization. When purchasing new equipment, we try to work with the manufacturer to make sure long-term maintenance needs are discussed. In some cases modifications are made to improve the maintainability of the equipment at the time we are discussing the equipment purchase.
The ideal situation is to have everything be very easy to maintain, but sometimes you end up with something difficult to maintain because of performance requirements. We aim for total ease of maintenance, but if we are 90 or 95% successful we're doing really well.
Q: What can design engineers do to help eliminate serviceability issues?
A: Design engineers should discuss and rub shoulders with maintenance engineers, technicians, and management that have to maintain the equipment. Even on a CAD system, the design engineer may not see everything that a maintenance engineer will bring to light if there is communication between the two groups. Too many times we have tunnel vision and we don't go far enough in talking with the user.
Q: How can plant managers help foster the move toward designing with serviceability in mind?
A: The buzzword between manufacturing facilities and their suppliers is partnering. I believe that as we acquire and upgrade equipment, we need to get people from the manufacturing group, maintenance engineers and technicians, purchasing people from the manufacturing firm, and the plant manager involved in talking with the sales people and the application and design engineers of the supplying firm. This type of discussion will give the acquiring plant equipment that performs better, that satisfies the needs of the production department, and that has a better level of maintainability for the maintenance department.
"Tell us your needs," design engineer says
Paris C. Altidis, Staff Engineer, Borg Warner Automotive Inc., Bellwood, IL
Design News: How important is design-for-serviceability?
Altidis: Different users demand different things from different products. For defense or military users, 70% of their focus is on reliability, 25% on performance, and 5% on price. For consumer companies, 10% of their focus is on reliability, 15% on performance, and 75% on price. These statistics are from The Handbook of Reliability Engineering and Management by W. Grant Ireson and Clyde Coombs Jr.
Q: Do you consider serviceability in design?
A: Yes. First we design for assembly. That then extends to serviceability because serviceability implies disassembly.
Q: What aspects of a design do you consider for serviceability?
A: Reliability in three areas: maintenance, mission, and safety. Mission reliability is how well the product performs its specified task. Maintenance reliability involves three things: availability (uptime or downtime), general maintenance schedules, and cost. From an end-user's standpoint, you have to consider the average cost factor, low maintenance, and easy access to failed parts (which cuts downtime).
Q: What are the elements of serviceability?
A: Several things. Among them:
- Standardization--the type of spare parts, and the type of diagnostics equipment and their capabilities.
- Assembly, packaging, and system modularity.
- Component selection--which affects maintenance time and frequency, as well as training requirements for special assembly systems.
- Accessibility, including operator interfaces.
- Mounting and fastening methods, as well as size and weight.
- Availability--how soon you can have the part in service.
- Human factors--ergonomics for service technicians.
- Warning systems--proactive built-in systems for periodic service reminders, and built-in testing equipment.
- Whether the assembly is repairable or disposable.
- Level of reliability required by customer--which dictates standard or very customized design.
Q: What can plant engineers and OEMs do to help design engineers eliminate serviceability issues?
A: Better communication from our customers is important. The customer needs to provide us with as much information as possible on the ten points I previously mentioned.