007-0613
Designing for Remanufacturing/Continuous Upgrade: understanding and overcoming the technical design challenges

A. King & S Barker, Mechanical Engineering, University of Bristol, UK

+44 (0) 117 928 8213

POMS 18th Annual Conference

Dallas, Texas, U.S.A.
May 4 to May 7, 2007

Abstract

Remanufacturing is a process that returns “used” products back to an "as new" condition for resale into useful service. The reason for this strategy is based on the fact that it preserves both the embodied energy of virgin production (thus reducing the environmental impact) and the intrinsic “value adding” process of the producer (thus increasing the manufacturer’s profitability).

However, whilst in certain conditions it may be socially, economically and environmentally advantageous, can it be practically achieved? In the remainder of the paper a more in-depth consideration of the main technical barriers is given. A number of examples are used to illustrate the way products can be designed to better suit remanufacture. However, the main focus of the paper explains how a design platform approach can more strategically address many of these technical issues.

Key Words

Remanufacturing, Platform Design, Waste Minimisation, Design for the Environment, Ecodesign.

  1. Introduction: the waste problem

In the year 2000 a United Nations report boldly stated “the major cause of continued deterioration of global environment is the unsustainable pattern of consumption and production, particularly in industrialized countries” [1]. And yet the broadly accepted definition of Sustainable Development is “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” [2]. The difference between sustainable and industrial agenda was defined by Stahel [3], who described the former as “a long-term societal vision, concerned with the stewardship of natural resources (stock equals wealth) in order to safeguard the opportunities and choices of future generations”; the latter, meanwhile, is described as a “short-term optimisation of throughput in monetary terms”. The need to move manufacturing closer to a sustainable vision is evident given that virgin development uses high levels of both energy and raw materials, and the current primacy of purchase cost means that it is often cheapest simply to discard an old product and develop again from new – thus producing waste.

1.2 Product Recovery Options

Thus, in order to prevent waste going to landfill sites, “closed loop design” is needed where disposal streams are diverted to become new raw material/manufacturing streams. This is illustrated in figure 1 which shows a simplified product production process. Raw materials from the ground are processed and converted into engineering materials to be shaped and formed into components. These components are in turn sub assembled and final assembled into a saleable product. This product then enters useful service but at some point will be discarded. Some products will be returned very quickly either due to a change of customer need or a fault; others will be used for a period until a lease or rental agreement expires. Some will be used until they are exhausted and fail at the end of their designed-for use life. However, an unpredictable number will be discarded at any point through their potential life due to fashion obsolescence (they loose their appeal due to new products appearing in the market with different/additional features).

Figure 1: Closed loop design through repair, reconditioning, remanufacturing or recycling

There are various factors for and against the options to repair, recondition, remanufacture or recycle [4]. However, the following characteristics differentiate remanufacturing from the other options:

  1. It preserves the embodied energy invested in the product’s 1st life by maintaining much of the component geometry and material composition. Whilst this is the root of the cost saving, it is also claimed to be the main environmental benefit. Lund estimates that an average remanufactured product only requires 20-25% of the energy used in its initial formation [5]. This requires a lower production cost, thus reducing the price of the remanufactured product. However, both repair and reconditioning preserve embodied energy too.
  2. It brings used products to “like-new” functional state with warranty to match. A remanufactured product is quality assured to the same standard that the product had when it was originally sold. This is the most evident distinguishing characteristic of this recovery route.

In connection with the recovery to an “as new” condition, remanufacturing normally also leads to a resale of the product to a different customer either in the same primary market as the original product of a separate “remanufactured product” secondary market. The distinction between these two options is shown in figure 2.

Figure 2: The Two Resale Options for Remanufactured Products

1.3 Remanufacture Processes

Ijomah et al [6] describe current remanufacturing activity by the following activities:

  1. Receive the “core”, that is the parts of the product to be remanufactured. The term “core” is used, as typical remanufactured parts are larger parts of the product.
  2. Strip and clean the core into individual elements. As the used parts may be dirty, they are dismantled and appropriately cleaned. A visual inspection would discard badly damaged elements.
  3. Estimate and quote remanufacturing costs. As many remanufacturing companies are sub-contractors to the OEMs, the cost of remanufacturing is often estimated on each product to determine the appropriate rectification strategy.
  4. Remanufacture. If the component were suitable, the appropriate machining/fabrication processes would be used to remanufacture the component to an “as new” specification.
  5. Build, test and dispatch. Finally, the remanufactured components are reassembled (together with necessary replacement components) to build the new product. After appropriate quality testing, the product would be dispatched for sale.

Arguably the most well known (and certainly the most referred to) example of remanufacturing is that of photocopiers made by Xerox [7]; their process is shown in figure 3.


Figure 3: Xerox’s equipment recovery & parts reuse/recycle process [7]

In 1987, Xerox started a new programmed called “asset recovery” and created a new, wholly owned subsidiary next to its manufacturing plant in The Netherlands. Its aim was two-fold: firstly, to remove old copying machines from the waste stream and, secondly, to process these machines for resale. It was called the Asset Recovery Operation (ARO). In 1989 5% of scrapped machines were remanufactured; by 1997 this had risen to 75% of the 80,000 copiers returned and the company claims to have saved $65million by 1996 [8]. The company now has remanufacturing facilities in the USA, the UK, The Netherlands, Australia, Mexico, Brazil and Japan[9].

2. Major Technical Barriers to Remanufacturing

Although there is now a strong driver for increased remanufacturing, it is still presently a rather small and low level manufacturing activity. Thus, in this section of this paper, the authors will describe the four main barriers to remanufacturing. These are shown in figure 4 in the order they appear in the overall remanufacturing process.


Figure 4: The four main barriers to remanufacturing

2.1 Reverse Logistics

In order for remanufacturing to happen, end-of-life products usually need to be returned to a small number of locations. Reverse Logistics is the process of collecting back from individual customers end-of-life products to a remanufacturing factory. This can be a big cost barrier to remanufacturing for the following reasons:

  1. The cost involved in the transportation of individual items can often be the most expensive part of the whole activity. This is a particular difficulty as the cost can vary significantly between customer locations and the available transport solution; it is thus difficult to predict and therefore afford.
  2. In addition to cost, the space requirements needed to store returned products (whether on route or at the destination factory) is also a barrier. Whilst it can be interpreted as another cost, it can simply be the unavailability of space that makes the reverse logistics difficult.
  3. Thirdly, the variability of return flow is also an issue as this has a direct effect on the output and thus availability of remanufactured products to customers entering the new market sector. This exposure to unmet demand (which loses revenue and damages customer satisfaction) stems from the low incentive for customers to return products. Whilst the choice is between the household bin and hassle of return (often with very little financial reward), return rates are likely to be difficult to guarantee.
  4. Lastly, identification and handling returned products can be difficult. With a huge variety of products potentially returned, often damaged, quickly identifying each product in terms of make and model is not a trivial matter. Most customers no longer have the original packaging and thus handling the products for optimal storage without further damage is difficult.
  5. Disassembly

When end-of-life products arrive at a potential remanufacturing factory, a manufacturer needs to disassemble the product. This can be difficult and expensive and was found to be a fundamental barrier in a recent review of remanufacturing activity in the UK[10]. This can be a big technical barrier to remanufacturing for the following reasons:

  1. Firstly, products are often not designed for disassembly. Whilst certain components are designed to be removed for maintenance, the majority are not. It is thus not always physically possible to remove components (such as those glued, riveted or welded together).
  2. Secondly, the poor condition of some end-of-life products can make it physically difficult to disassemble components that have been damaged or corroded.
  3. Thirdly, the fact that many products are manufactured overseas (such as in the Far East) often means that the assembly logic and sequence information is not available to the remanufacturer. Thus, having to disassembly a high number of products in order to “learn” the best sequence can be a significant barrier.

As this barrier is affected by decisions made early on in the design phase, it requires a fundamental change to the design philosophy employed.

2.3Component Inspection

Once the products/parts have been disassembled, the manufacturer needs to find out what condition the products/parts are in. If the parts are suitable for remanufacture they may go to one location; otherwise they would be sent for recycling or landfill. In addition, remanufactured parts need to be Quality Assured before they can be introduced to the market. This can be a big cost barrier to remanufacturing for the following reasons:

  1. Firstly, as many components will not be remanufactured these can prevent access to inspect those potentially being remanufactured. It is thus not always possible to quickly (and thus economically) assess the condition of certain components.
  2. Secondly, it is not evident that a component is distorted or worn unless an original component is available. Therefore, it can be difficult to judge the level of remanufacturing needed.
  3. Thirdly, in respect of complex assemblies, the effort needed to physically inspect the assembly may be far more than the benefit of remanufacture. Therefore, it is necessary to develop inspection proxies by which a simple observation can be taken as indicative of more fundamental issues.
  4. Customer Demand

Whilst the previous barriers are real and significant, by far the greatest policy barrier to initiate new remanufacturing schemes is having a credible and stable demand for the remanufactured products. This is the biggest policy barrier for the following reasons:

  1. Firstly, a remanufactured product that represents the last generation of technology, styling and functionality cannot compete with new products. As cheaper new products are likely to be available (albeit of different brands), the lower price of remanufactured products may not persuade customers to buy cheaper older products against cheaper new ones.
  2. Secondly, customer association of remanufactured products with “second-hand” and thus lower quality is very difficult to change. Whilst quality guarantees can be made, manufacturers are reluctant to provide too much in case of large recall charges.
  3. Thirdly, the introduction of remanufactured products can damage an existing brand both in terms of image and sales. Thus, some manufacturers are unwilling to introduce new schemes that may damage the reputation and success of their established brand.

3Incremental Design

Each of the barrier just mentioned pose very real design challenges. However, current remanufacturing practise has developed a number of incremental design changes that better allow for a product to be disassembled, remanufactured and then reassembled. In this section of the paper, the authors present a number of these approaches.

3.1 Supply Disassembly information with Design

One relatively simple way of helping disassembly operatives is to devise disassembly information at the time of the original design. In this way, this information can either be incorporated into a design manual. Better still, some components can be manufactured with the disassembly information moulded into the geometrical form (with injection mouldings) or added by way of stick-on labels. One example of such disassembly information is shown in figure 5 where symbolic language is used to show the fasteners, tools and orientation needed for disassembly [11].

Figure 5:Symbolic Disassembly Codes embedded within a product’s components

3.2Reconsider Parts Reduction

By far a more effective incremental change is the reconsideration of parts reduction within engineering design. The move towards fewer piece parts has been a long and well established paradigm within design according to the principles of cost reduction and assembly simplification. However, within the new paradigm of remanufacturing, the decision to use two rather than one component can deliver many disassembly and reuse benefits. Firstly, the use of two components may allow easier disassembly because less access is needed, or simply less disassembly is needed. However, more specifically, the use of additional components can allow more of a product to be reused as only the worn or damaged part of the component is replaced. This may well be expected where a component has one area receiving mechanical stress or greater vibration/movement than the rest (such as near hinge points). If these components are made from two or more parts, the removal of hinge areas alone would allow the larger remaining part simply to be cleaned and reused. This thinking is illustrated in figure 6.

Figure 6:Additional Components can save material & cost in 2nd/3rd lifetimes

Whilst this change in design is logical (and is successfully used by some remanufacturers), it does require a long-term commitment to remanufacturing such that the initial additional costs are justified by later return and re-use.

3.3. Adding Assembly Redundancy

A further design change than can be used to enable better remanufacturing is the addition of assembly redundancy. This is helpful because worn or corroded fixings can be difficult to remove. However, if additional fixing points have been designed in, a second life can be made by using these points and not the original ones. Such an approach may have bolt threads tapped for one life and additional ones also tapped for later use in the second life. An adaptation of this is to tap deeper threads than needed such that a stripped thread from a disassembly routine can be accommodated by the use of a longer bolt in the second life. This is illustrated in figure 7.

Figure 7:Deeper Threaded holes to allow for re-assembly

3.4 Part Assembly Calibration Datums

One other way in which a product can be incrementally re-designed for remanufacture is through the addition of part assembly calibration datums. Traditional manufacturing treats each component separately and thus each component is quality inspected individually. However, after a first life where little wear or damage is expected in some components, it may be more efficient not to fully disassemble every component just to allow for re-calibration. Instead, calibration points, fixing locations and alignment points can be added to allow for pre-assembled calibration during remanufacture. One example is shown in figure 8 where two counterbores have been added to two components such that the assembled 3-part component can be calibrated for cylindricity without further disassembly [12].

Figure 8:Additional Features added to allow pre-assembled calibration.

Each of these incremental design changes can make products easier to remanufacture. However, they cannot fully allow for product upgrades and replacements.

4Strategic Design: Platform Design

Whilst incremental design techniques enable limited improvements to be made to the remanufacturing process, a radical design change is needed to fully overcome the main barriers. One way of overcoming these barriers may be by Platform Design. This section describes Platform Design and the next section describes how it could be applied to remanufacturing.

Platform Design is an approach to design where a base platform is designed such that it can be used as the basis for a family of derivative products [13]. The authors’ definition of platform design as it is currently applied is:“a strategic architecture of common and parametric components that forms the basis for a product family – aimed at meeting either the objective of increased commonality or increased variability. The common components are high value-added parts to reduce cost and the parametric components vary to suit different customer needs and interface with outer derivative product architecture”.

An interface is “spatial region where energy and/or material flow between components” [14] and product architecture is the arrangement of component forms to achieve product functions [15].

The automotive company Volkswagen uses a number of key platforms to develop a variety of automotive “brands” as shown in figure 9[16]. These have been developed where the “savings” of the standardised platform can “pay” for the customisation of the final products. Other platform examples cited in the literature include Black & Decker [17], Rolls-Royce Aero-engines [18], and Nippondenso Meters [19].