Assessment of the Disassemblability of Electric Bicycle Motors for Remanufacturing

doi:10.21203/rs.3.rs-2062163/v1

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Research Article

Assessment of the Disassemblability of Electric Bicycle Motors for Remanufacturing

https://doi.org/10.21203/rs.3.rs-2062163/v1

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Journal Publication

published 13 Mar, 2023

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In 2021, sales of electric bicycles in Germany increased compared to the previous year, leading to a 43% share of electric bicycles in the total bicycle market. The German Bicycle Industry Association (ZIV) expects this growth to continue and that by 2025 every second bicycle sold in Germany will have an electric motor. Therefore, due to the increasing popularity, both the built-in resources and the possible treatments after the use phase need to be considered regarding sustainable market development. In this context, remanufacturing is one promising end-of-life strategy that enables a new life cycle of products and components, thus reducing the consumption of natural resources and minimizing waste production. The used products are restored to their original conditions by disassembling, cleaning, sorting, reconditioning, and reassembling. Thereby, disassembly is a decisive process step as it creates the prerequisites for all further steps in the process chain and significantly determines the economic feasibility of a remanufacturing process. Therefore, this paper aims to evaluate the ease of disassembly of electric bicycle motors and thus determine their suitability for remanufacturing. To evaluate the disassemblability, the ease of Disassembly Metric (eDiM), a quantitative assessment method for evaluating disassembly effort, was adapted to the needs of the electric bicycle motors. The method was finally applied to five electric bicycle motors from established manufacturers and assessed their ease of disassembly. The results showed that the electric bicycle motors can be disassembled without significant damage and classified as suitable for remanufacturing based on their disassembling ability.

Remanufacturing

Disassemblability

Electric Bicycle Motors

Ease of Disassembly Metric

E-Mobility, the transport of people and goods by vehicles powered by electric energy, will increase significantly in the coming years [3, 7, 33]. This includes electric cars and other forms of mobility, such as electric bicycles [29]. The popularity of electric bicycles has grown very strongly in recent years. The market growth can be seen, for example, in the number of electric bicycles sold per year in Germany, which has increased by more than 800% in the last ten years [62]. In 2021, almost two million electric bicycles were sold in Germany, leading to a share of 43% of electric bicycles in total bicycle industry sales [63]. Until 2025, the electric bicycle market is expected to grow to over 50% of all bicycles sold [21]. Therefore, due to the increasing popularity and number of electric bicycles, the built-in resources and the possible treatments after the use phase need to be considered [32]. However, Amrhein shows that no well-elaborated circular concepts exist for electric bicycle components and raw materials [2, 32]. Especially, the electric bicycle motor and accumulator are becoming the focus of attention for remanufacturing as high-value components [21].

In this context, as a key element of a circular economy, remanufacturing is a promising End-of-Life (EoL) strategy that enables a new life cycle of products and components, thus reducing the consumption of natural resources and minimizing waste [21, 52]. Remanufacturing closes product cycles and enables the reuse of products at the end of their usage phase while maintaining or restoring the product’s shape and associated properties [56, 58]. This clearly distinguishes remanufacturing from material recycling [58]. In contrast to the repair of defective products, remanufacturing represents an industrial process in which the remanufactured product is brought to at least the quality level of a new product with the same warranty, and a new product life cycle is made possible [5, 50]. Studies show that remanufacturing can lead to a resource demand of only 10% compared to new production [30, 40, 59]. According to Steinhilper and Butzer, the remanufacturing process consists of disassembling, cleaning, inspection, sorting, reconditioning or replenishment of used parts, and product reassembly before a final product test [50, 51]. These five steps of the remanufacturing process are embedded in quality checks [50, 51]. The number and sequence of process steps can vary depending on product-specific requirements.

Thereby, disassembly is a crucial step in remanufacturing as it creates the prerequisites for all further process steps and is considered the primary source of information, where valuable data is gained [44, 45]. Disassembly for remanufacturing differs from disassembly procedures for other EoL processes, as retrieved components, must be in an appropriate shape to be reconditioned. Therefore, the priority in remanufacturing is to minimize the damage to reusable parts, whereas recycling focuses on separating different materials with the least effort [47].

In general, three disassembly methods exist: non-destructive, semi-destructive, and destructive disassembly [57]. Destructive disassembly (e.g., metal cutters, crowbar), known as dismantling, allows higher flexibility but prevents the reuse of components [54, 57]. Therefore, destructive disassembly is particularly suitable for material recycling [47]. As remanufacturing favors non-destructive disassembly, disassembly in this context can be defined as a »process whereby an item is taken apart in such a way that it could subsequently be reassembled and made operational« [9, 10]. However, destructive methods in remanufacturing are acceptable, e.g., for low-value parts to reach valuable ones or to remove fasteners [44]. Therefore, semi-destructive operations are tolerable if the damage does not prevent reprocessing or reassembly [4]. Thus, process requirements are more rigorous in remanufacturing than other EoL processes [45].

The technical feasibility of remanufacturing and the economic efficiency of the implementation are strongly dependent on the disassemblability of the product and the associated effort [48]. Therefore, this work aims to systematically determine insights into the complexity of the product structure of electric bicycle motors during disassembly and finally to determine the ability to remanufacture electric bicycle motors based on the ease of disassembly of the components.

Numerous researchers propose methods to measure the ease of disassembly of products. Hence, in-depth literature research was carried out to identify a method that offers enough flexibility to be applied to a new product group and an objective evaluation scheme. The parameters analyzed by different authors are summarised in an overview table, illustrated in the Appendix.

For this study, the ease of Disassembly Metric (eDiM) is the preferred method for evaluating the ease of disassembly of the electric bicycle motors. The eDiM is a quantitative assessment method to evaluate the effort to disassemble a product completely or partially without destruction [55]. The metric was developed by Vanegas et al. [55] and extended by Peeters et al. [43]. The method consists of a catalog of registered disassembly tasks evaluated by time and based on the Maynard Operation Sequence Technique (MOST) method [43, 55]. The MOST is characterized by a proper balance between accuracy and required effort to evaluate complex and basic tasks, irrespective of the considered product type [55]. MOST is a system based on the Methods-Time Measurement (MTM) with preset times; however, the technique is more straightforward than MTM and still provides sufficient accuracy for disassembly evaluation [35].

Vanegas et al. [55] approach the disassemblability evaluation by defining six disassembly tasks based on literature research and observation of manual disassembly procedures, visualized in Table 1.

Table 1

Disassembly tasks [55]
	Disassembly task	Explanation
1	Tool change	Describes actions to pick up/put back a tool.
2	Identification	Refers to the time needed to locate fasteners, including identifying the fastener type and the appropriate tool for unfastening. As manipulation might be required to identify a fastener, identification and manipulation are related tasks.
3	Manipulation	Describes the time needed to manipulate the product to reach or identify a fastener for unfastening, for instance, turning the product over.
4	Positioning	Refers to placing a tool relative to a fastener before initiating actual disconnection.
5	Disconnection	Refers to a fastener’s actual unfastening time.
6	Removal	Describes the removal of loosened components and placing them into corresponding bins.

Pre- and post-actions, such as used product collections, product positioning on the workbench, etc., are not included in the eDiM as these actions are not affected by redesign, nor are inefficiencies, e.g., unsuccessful disconnection trials [55].

The six tasks explained in Table 1 are all modeled using MOST to enable the computation of the required disassembly times while respecting product and connector attributes. For five of the six disassembly tasks, standard sequences are identified and presented by Vanegas et al. [54]. In contrast, the sequence of tasks for loosening the connection changes depending on the type of fastener.

To determine the disassembly time for a fastener type, actual motions needed for unfastening must be analyzed. A unanimous fastener taxonomy is still necessary to avoid subjectivity. Such a taxonomy should highlight fastener properties and provide a clear predefinition of the tool required to release a fastener. It should be noted that a fastener may have multiple potential tools for unfastening [55]. The MOST sequences proposed by Vanegas et al. [55] and Peeters et al. [43] can be taken as a starting point.

The six disassembly tasks can be combined with a spreadsheet, illustrated in Table 2, to calculate the total eDiM measured in seconds (s) [55]. Vanegas et al. provide in-depth guidance on the spreadsheet application [55].

Table 2

Generic eDiM Calculation Sheet for n Components, adapted from [55]
1	2	3	4	5	6	7	8	9	10	11	12	13
Disassembly sequence of components	Disassembly sequence of connectors of components	Number of fasteners	Number of product manipulations	Identifiability (0,1)	Tool Type	Tool Changes (s)	Identification (s)	Manipulation (s)	Positioning (s)	Disconnection (s)	Removal (s)	eDiM (s)
1
…
n

Assessment set-up

The assessment set-up was inspired by the procedure described by de Fazio et al. [13]. A research protocol consisting of eleven steps is shown in Table 3 to ensure transparency and comparability of the disassembly procedure.

Table 3

Assessment set-up
	Preparation	Description
1	Tutorial/ documentation analysis	During this analysis, a sequence that could be applied in actual disassembly is identified, and component names are studied. Thus, the applied sequence is established in advance but with certain flexibility.
2	Preparation of documentation material	Templates for recording and documenting the disassembly processes, like the disassembly diary and theeDiM calculation sheet are being prepared.
3	Set-up of recording material	This is done to film the disassembly procedure of every single part.
	Repeatable steps
4	Component disassembly	According to the identified sequence in step 1.
5	Reassembly	This is done to avoid filming unnecessary handling and improve the eDiM’s input data.
6	Component disassembly (repetition)	The part is disassembled more efficiently, and information concerning the force type or the number of product manipulations is revised and eventually adapted.
7	Recording of the action	The repeated disassembly is recorded for analyzing purposes as the eDiM database is expanded for this research, and thus accurate motion analysis is required. In case of difficult disassembly, the first and this case, single disassembly action is filmed.
8	eDiM calculation sheet	After the repetition, the first columns (input data) of the eDiM sheet are filled in. For instance, information on product manipulations is more reliable after a repetition.
9	Disassembly diary	For each part, a diary template is filled out, which includes: fastener type and quantity, used tool and needed actions, applied force type, precedence relations (which parts are disassembled before or after), and general comments on observed difficulties or obstructions.
10	Photo documentation	Every disassembled part has its picture taken for documenting reasons. Moreover, every part is assigned a component code to ensure consistent terminology.
11	Weighing of part	Every component is weighed to gain a general overview of the product’s composition and eventually estimate the amount of the used product that can be reused for remanufacturing purposes
This procedure (steps 4–11) is applied until subassemblies are reached, which cannot be further disassembled non-destructively.

Adaptation eDiM

The existing database needed to be extended to use the eDiM for the disassembly evaluation of electric bicycle motors. The MOST sequences for standard tasks, shown in Table 4, and for disconnection, shown in Table 5, are based on the following assumptions, adapted from Vanegas et al. [55]:

Starting position is an employee standing in front of a workbench.
Bins, tools, shop press, and vise are positioned within reach on the workbench.
The disassembler is standing; no time for rising or sitting down is considered.
The operator is familiar with the disassembly sequence; no time to assess which part is disassembled next is taken into account.

The reference values established by Vanegas et al. [55] are suitable for this research. They describe the handling of relatively small electronic products whose weight does not exceed 4 kg, and the examined electric bicycle motors are within these limitations.

Table 4

Reference values used for standard tasks, adapted from [43, 55]
task	Description	sequence	time (s/task)
Tool change	Fetch and put back	\|A₁B₀G₁\|+\|A₁B₀P₁\|	1.4	[55]
identifying	Localizing fasteners
	Visible are > 0.05 mm²		0	[55]
	Hidden: visible are < 0.05 mm²	\|T₁₀\|	3.6	[55]
Manipulation
Type 1	Turning the product with one hand (product mass < 2kg - workbench)	\|A₁B₀G₁\|+\|L₃\|	1.8	[43, 55]
Type 2	Turning the product with two hands (2kg < product mass < 4kg - workbench)	\|A₁B₀G₃\|+\|L₆\|	3.6	[43]
Positioning
Type 1	Positioning tool onto a fastener	\| A₁B₀P₃A₀\|	1.4	[55]
Type 2	Positioning tool onto fastener for higher force	\| A₁B₀P₆A₀\|	2.5	[43]
removing	Removing separated components	\|A₁B₀G₁\|+\|A₁B₀P₁\|	1.4	[55]

The MOST sequences used for disassembly in this research are presented in Table 5. The sequence is listed with the corresponding description, whether new or adopted from previous literature.

Table 5

Disassembly MOST Sequences
Fastener Type	Fastener Name & Characteristics	Tool	Tool Change (s)	Tool Positioning (s)	Disassembly MOST Sequence	Disassembly Time (s)	Source
SCREW	Phillips/ Torx Screw, D ≤ 6 mm, L < 2*D	Power Drill	1.4	1.4	\|L₃\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	2.5	[43, 55]
	Phillips/ Torx Screw, D ≤ 6 mm, L < 2*D	Screw-driver	1.4	1.4	\|L₁₀\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	5.0	[43, 55]
	Phillips/ Torx Screw, D ≤ 6 mm, L ≈ 2–3*D	Power Drill	1.4	1.4	3/2*\|L₃\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	3.0	new
	Phillips/ Torx Screw, D ≤ 6 mm, L ≈ 2–3*D	Screw-driver	1.4	1.4	12*\|L₁\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	5.8	new
	Phillips/ Torx Screw, D ≤ 6 mm, L ≈ 3–5*D	Power Drill	1.4	1.4	5/2*\|L₃\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	4.1	new
	Phillips/ Torx Screw, D ≤ 6 mm, L ≈ 3–5*D	Screw-driver	1.4	1.4	\|L₁₆\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	7.2	new
	Grub Screw, D ≤ 6 mm, L ≈ 2–3*D	Allen Key	1.4	1.4	\|L₁₆\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	7.2	new
	Grub Screw, D ≤ 6 mm, L ≈ 2–3*D	Power Drill	1.4	1.4	3/2*\|L₃\|+\|A₁B₀G₁\|+\|A₁B₀P₁\|	3.1	new
cable plug	Cable Plug Force < 5 N Plier	Plier	1.4	2.5	\|L₁\|	0.4	Adapted from [43]
cable plug	Cable Plug Force < 5 N Hand	Hand	0	1.4	\|L₁\|	0.4	[43]
snap fit	Snap Fit Type 1 Hand	Hand	0	1.4	\|L₁\|	0.4	[55]
	Snap Fit Type 1 Spudger	Spudger	1.4	1.4	\|L₃\|	0.4	[13]
	Snap Fit Type 2 Hand	Hand	0	1.4	\|L₃\|	1.1	[55]
	Snap Fit Type 2 Spudger	Spudger	1.4	1.4	\|L₁\|	1.1	[13]
friction fit	Friction Fit Type 1 Hand	Hand	0	1.4	\|L₁\|	0.4	[13]
	Friction Fit Type 1 Spudger	Spudger	1.4	1.4	\|L₃\|	0.4	[13]
	Friction Fit Type 2 Hand	Hand	0	1.4	\|L₃\|	1.1	[13]
	Friction Fit Type 2 Spudger/ Plier	Spudger / Plier	1.4	1.4	\|L₆\|	1.1	[13]
	Friction Fit Type 3 Hand	Hand	0	2.5	\|L₆\|	2.2	[13]
	Friction Fit Type 3 Spudger/ Plier	Spudger/ Plier	1.4	2.5	\|L₃\|	2.2	[13]
	Friction Fit Type 2 SFM, ≈ 3 Taps	SFM	1.4	2.5	\|L₆\|	1.1	new
	Friction Fit Type 3 SFM, ≈ 3 Strikes	SFM	1.4	2.5	\|L₄₂\|	2.2	new
	Friction Fit Type 3 Internal bearing pullers	Internal bearing pullers	1,4	20.0	\|L₁₀\|	3.6	new
	Friction Fit Type 3 Two jaw bearing puller	Two jaw bearing puller	1,4	25.3	\|L₁₆\|	5.8	new

Most disconnection sequences were extracted from previous studies [43, 55], except for the screws and particular friction fits. For these connectors, classes were added within the course of the analysis. The cable plug category is adapted from Peeters et al. [43]. The sequence itself remains unchanged. However, compared to Peeters et al. [43], a plier is used rather than the human hand because grabbing the cable with the hand would be difficult.

The already existing screw sequences cannot be used as the parameters of the screws predominant in the case study products do not match those of existing defined MOST sequences. Existing sequences account for a thread length smaller than twice the diameter. However, screws observed in electric bicycle motors present a thread length of more than twice the diameter. Thus, by making use of the documentation of Zandin and Vanegas et al. [55, 61], new screw sequences were added. The relationship ‘length < 2 x diameter (D)’ presented in the development of the eDiM method has already been introduced in the development of the MOST fasten (F) and loosen (L) data card by Zandin [61]. In addition, Zandin [61] defined |L₃| for loosening screws with a diameter of 6 mm or less and |L₆| for loosening screws with a diameter of up to 25 mm by using a power tool. For longer threads, a frequency can be applied to F or L, which is the case in this study [32].

The removal of screws after loosening is indicated by the sequence |A₁B₀G₁|+|A₁B₀P₁| introduced by Peeters et al. [29]. For the different types of fasteners, the sequences are given in Table 5. In the case of a grub screw loosened with an allen key, |L₁₆| describes eight crank movements, and for the torx screw, |L₁₆| corresponds to sixteen screwdriver turns. This finding is based on the practical tests and the data card for screwing and loosening by Zandin [61].

Next, friction fits are the dominating fastening method in electric bicycle motors. The applied force to disassemble a component has the most significant influence on disassembly time [13]. Three force intensities based on MOST have already been defined in the original method by Vanegas et al. [55]. De Fazio et al. expanded the snap-fit class and added the friction fit class [13]. The three force intensities are described as follows by De Fazio et al. [13]: Type 1 – Force < 5 N: MOST sequence |L₁|, this sequence applies when only the fingers or partial parts of a hand are needed, and low intensity is sufficient. Type 2–5 N < Force 20 < N: MOST sequence |L₃|, which describes manipulating the entire hand with medium intensity. Type 3–20 N < Force: MOST sequence |L₆|, this sequence applies when the entire arm or both hands are needed to disconnect a component. The spudger, similar to a flat screwdriver, is chosen to represent any hand tool different from the human hand to loosen friction fits or snap fits. For these intensities, tool positioning times are differentiated, namely 1,4 s for type 1 and 2 and 2,5 s for type 3 [13]. Positioning times differentiation was introduced by Peeters et al. [43].

This paper introduces a new soft-faced-mallet (SFM) tool as a new friction fit category. Even though the tool meets the definition of de Fazio et al., it is observed in the practical attempt that mallet use requires caution while positioning to focus on the right part before tapping [13]. As a result, a tool positioning time of 2.5 s is assigned to a friction fit type 2 SFM. Type 1 is not defined as a mallet action always requires the whole hand. De Fazio et al. also state that MOST sequences for friction fits do not need a removal task, as the part is already removed within the disconnection sequence [13].

Furthermore, the tools, internal bearing pullers and two jaw bearing puller, extend the friction fit category. The internal bearing pullers can be modeled with the MOST sequence |L₁₀|. For the removal of the bearings with the internal bearing puller, about five turns with a wrench are needed. Thereby, the internal bearing pullers resemble a T-wrench [61]. Analogously, the two jaw bearing puller can be described with the MOST sequence |L₁₆|. In this case, five to six turns with a wrench can be assumed to remove the bearings with a two jaw bearing puller. Thereby, the movement of the wrench and the two jaw bearing puller is similar to the movement of a ratchet described in the MOST sequence [61].

The presented methodology is validated in the following section using the example of electric bicycle motors. Electric bicycle motors are usually brushless DC electric motors (BLDC), whose product characteristics result from the combination of mechanical components, sophisticated electronics, and high-energy permanent magnets [19, 28]. Furthermore, BLDC motors are characterized by few fashionable product features, in contrast to different frame structures or digital control elements, which favor remanufacturing [19].

Electric bicycle motors can be divided into hub-drives and mid-drives concerning their arrangement on the bicycle [46]. Accordingly, the electric bicycle motor can either be placed on one of the hubs or in the center of the frame. The mid-drive system is the most common concept integrated into the bottom bracket and cranks. Mid-drive motors account for about 30 to 50% of the cost of an electric bicycle [21]. The main reason for this is the price-driving individual components such as rare-earth magnets, weight-reduced motor housings and the power electronics integrated into the compact housing [14, 19, 28].

Initial investigations of electric bicycle motors using the enhanced Remanufacturing Process Step Model for e-mobility components by Schlesinger et al. and the analysis of sustainable business models by Koop et al. show the potential of remanufacturing electric bicycle motors in general [32, 46]. However, a detailed analysis regarding the disassembly capability of different engines is missing so far. This provides the basis for a remanufacturing process to estimate the necessary effort of disassembly on the one hand and to identify the components that can be disassembled without destruction. Therefore, five mid-drive motors from established manufacturers are examined in more detail below; these are listed in alphabetical order in Fig. 1.

In the context of the result analysis, it is necessary to interpret and evaluate the disassembly results of the five electric bicycle motors. General and specific findings of a single electric bicycle motor are discussed. Subsequently, the results from the eDiM of each electric bicycle motor are presented and compared. The simplicity of disassembly was evaluated concerning the five disassembly tasks ‘tool changes’, ‘identification’, ‘manipulation’, ‘positioning’, ‘disconnection’, and ‘removal’.

General and specific findings during the disassembly

In general, the electric bicycle motors were disassembled non-destructively. Hence, the disassembly of the electric bicycle motors was discontinued in case further disassembly was only achievable by destroying or damaging components. Hence, it must be noted that none of the electric bicycle motors were completely disassembled to the part level. Consequently, the total component count deviates from the number of assemblies and comonents which could be disassembled destructively.

Furthermore, the same set of tools could be used to disassemble the five electric bicycle motors. Thereby, the following tools were used for disassembly: power drill (incl. bits), monkey wrench, combination pliers, soft-faced mallet, snap ring pliers, side cutter, allen key, spudger, internal bearing pullers, and two jaw bearing puller.

The structure and design of the electric bicycle motors are highly dependent on the manufacturer. However, considering all parts, similar component groups or subassemblies are identified for the five electric bicycle motors: housing, rotor, stator, PCB, and gearbox.

The AEG Comfort Drive electric bicycle motor was disassembled into 31 components, excluding smaller components, e.g., screws and seals. Like the Bafang BBS01B, the controller is embedded in silicone in this model, so it can only be separated from the housing with great effort.

The Bafang BBS01B electric bicycle motor was disassembled into 33 components, excluding, e.g., screws and seals. The electric bicycle motor shaft nuts must be loosened on both sides for disassembly, whereby a special tool is helpful. The plug-in connections were also glued with silicone regarding this electric bicycle motor, which increases the disassembly time. The controller is embedded in silicone in this model, so it can only be separated from the casing with great effort.

Regarding the Bosch PerformanceLine CX, the electric bicycle motor could be disassembled in 34 components, excluding smaller components, e.g., screws and seals. A particular aspect of the disassembly was separating the adhesive connection between the housing and the PCB.

The Brose Drive C E22243 electric bicycle motor was disassembled into 24 components, excluding smaller components, e.g., screws and seals.

The Shimano STEPS E6110 electric bicycle motor was disassembled into 32 components, excluding smaller components, e.g., screws and seals. The electric bicycle motor was difficult to open due to the glued seals between housing/housing cover and housing/stator housing. In addition, to separate the circuit board from the stator and connector, the power cables had to be disconnected.

eDiM Analysis and Comparison

In the following section, the five electric bicycle motors are analyzed with the help of the eDiM. Figure 2 presents a graphical overview of the results from the eDiM. The figure shows the percentage share of the six disassembly tasks of the respective electric bicycle motor.

It took 32 steps to disassemble the Bosch PerformanceLine CX electric bicycle motor. According to the eDiM, the disassembly process takes 581.3 seconds. The disassembly tasks’ disconnection’ with 294.1 seconds (50.60%) and ‘positioning’ with 185.3 seconds (31.87%) require the most time. The disassembly tasks’ manipulation’ with 41.4 seconds (7.12%), ‘tool changes’ with 28.8 seconds (4.95%), and ‘removal’ with 31.7 seconds (5.45%) have a minor influence on the disassembly time. The disassembly task ‘identification’ does not occur for this electric bicycle motor.

27 disassembly steps are required for the electric bicycle motor from Shimano STEPS E6110. In total, the disassembly of the electric bicycle motor takes 573.2 seconds, according to eDiM. Similar to Bosch PerformanceLine CX, the disassembly tasks are ‘disconnection’ with 288.4 seconds (50.30%) and ‘positioning’ with 189.8 seconds (33.12%), the largest share. This is followed by the tasks ’manipulation’ with 43.2 seconds (7.54%), ‘tool changes’ with 28.8 seconds (5.02%), and ‘removal’ with 23.0 seconds (4.02%). The disassembly task ‘identification’ does not appear in this summary.

For the Bafang BBS01B electric bicycle motor, the 38 disassembly step takes 675.2 seconds. Thereby, the disassembly tasks ’positioning’ with 298.5 seconds and ‘disconnection’ with 250.4 seconds are responsible for almost 80% of the required time. This is followed by the ‘removal’ task with 64.8 seconds (9.60%). The ‘tool changes’ and ‘manipulation’ tasks take another 34.6 seconds (5.12%) and 27.0 seconds (4.00%), respectively. No time is required for the task’ identification’.

For the AEG Comfort Drive electric bicycle motor, 236.9 seconds (40.34%) for the ‘disconnection’ task, 221.2 seconds (37.66%) for the ‘positioning’ task, 55.8 seconds (9.50%) for the ‘manipulation’ task, 36.0 seconds (6.13%) for the ‘tool changes’ task, 23.0 seconds (3.92%) for the ‘removal’ task, and 14.4 seconds (2.45%) for the ‘identification’ task are needed. In total, 587.3 seconds and 36 disassembly steps are required to disassemble the electric bicycle motor.

The disassembly time with a total of 30 disassembly steps for a Brose Drive C E22243 electric bicycle motor is 426.4 seconds. The disassembly tasks ’manipulation’ with 39.6 seconds (9.29%), ‘tool changes’ with 21.6 seconds (5.07%), and ‘removal’ with 20.2 seconds (4.73%) are of lower importance. As with the other electric bicycle motors investigated, the disassembly tasks ’disconnection’ with 189.2 seconds (44.36%) and ‘positioning’ with 155.9 seconds (36.56%) require the most time. The disassembly task ‘identification’ does not apply to this electric bicycle motor.

This section summarizes and interprets the data obtained from eDiM concerning the five disassembly tasks ‘tool changes’, ‘identification’, ‘manipulation’, ‘positioning’, ‘disconnection’, and ‘removal’. Furthermore, dependencies between the disassembly tasks are identified, and their relevance in the disassembly is explained.

The disassembly task ‘tool changes’ takes between four and seven percent of the total disassembly time of the electric bicycle motors. The time required for this task is dependent on the number of tools needed and the number of connector types (e.g., different kinds of screws). The number of tool changes for the five electric bicycle motors is relatively similar and varies between 15 and 23.

The required time for the disassembly task ‘manipulation’ is between four and ten percent of the total disassembly time. Thereby, the electric bicycle motors have to be manipulated between eleven and 21 times during the disassembly process.

Concerning this work, the manufacturers provided no information regarding the eDiM. Hence, the information on the optimal disassembly sequence, which is generally derived from the assembly sequence, and the necessary tools were not known in advance. The missing information was determined through tutorials/documentation analysis and during the disassembly of the electric bicycle motors. The missing information could have increased the disassembly time of the tasks ‘tool changes’ and ‘manipulation’. However, during method development, Vanegas et al. [55] pointed out that manufacturer information unavailability is a common issue.

Regarding the task ‘removal’, the acquired time during the disassembly is relatively low, which is ascribable to the frequently encountered friction fits, for which no removal action is considered. The ‘removal’ task accounts for four to ten percent of the total disassembly time. In addition, the disassembly task ‘identification’ plays a minor role in the disassembly of electric bicycle motors. The connections are typically easily visible.

In general, the case study shows that the five electric bicycle motors can be disassembled with the same kind of tools. However, the number of tools needed depends on fastener types (e.g., different types of screws). In general, fastener types have the most significant influence on the total eDiM and disassemblability. The type of fastener influences the disassemble tasks ‘tool changes’, ‘tool positioning’, and ‘disconnection’. Thereby, the disassemble tasks ‘positioning’ and ‘disconnection’ have the strongest influence on the overall disassembly time. The number of screw connections, adhesive connections, and bearing disassembly are the largest contributors to the amount of time required in these disassembly task categories.

Besides, the eDiM has not been fully developed yet, so a well-structured taxonomy of fasteners that satisfies the analysis product group’s need was not available [55]. Thus, new MOST sequences identified within the scope of this work should be observed with caution as only five products have been disassembled as a base for MOST sequence creation.

Furthermore, despite the awareness that used product condition is one of the significant uncertainties in remanufacturing, this parameter is not considered in the analysis. The eDiM indicates generic procedures that do not consider this factor. However, the considered electric bicycle motors were used, though no significant signs of wear were identified. Nevertheless, the elaborated results must be considered with care, as in case of corrosion or extreme wear, other tools may have to be used, the force required to disassemble the components may increase, or the components may even be damaged. Disconnection time or even the sequence order can vary, impacting the disassembly time and the system’s economic efficiency.

In order to be able to remove critical components such as bearings, it requires a high disassembly depth in the electric bicycle motors examined. Therefore, taking into account the subsequent remanufacturing at the product’s end-of-life already in the design and development phase of the electric bicycle motors holds great potential. To increase the ease of disassembly, the design of the electric bicycle motors could be made less sequential and more modular, for example. This means that most electric bicycle motors do not have to be disassembled completely to access critical components.

Using the eDiM, this work evaluated the disassembly capability of electric bicycle motors in terms of their suitability for remanufacturing. An actual disassembly was carried out to access missing data and gain first-hand disassembly insights to perform product analysis. This work concluded that the electric bicycle motors examined can be disassembled without significant damage if all the necessary tools are available. Only minor or low-value parts, which are anyway replaced in remanufacturing, are damaged during the procedure. Therefore, the electric bicycle motors studied are classified as suitable for remanufacturing based on their disassembling ability.

However, considering the variety of electric bicycle motor models and their variants, this work cannot make a general statement about the suitability of electric bicycle motors for remanufacturing. However, considering the five electric bicycle motors from established manufacturers indicates that this could be the case. In order to be able to make a statement about the feasibility of remanufacturing electric bicycle motors, further research should investigate the disassemblability of a broader range of electric bicycle motors.

In addition to the technical feasibility of the non- resp. semi-destructive disassembly of electric bicycle motors, it is additionally necessary to examine the economic feasibility of a possible remanufacturing of electric bicycle motors. Thereby, the economic feasibility depends on the value, availability, and degree of wear of the individual components as well as the disassembly time. If these data are added to the eDiM, a cost calculation for remanufacturing electric bicycle motors can be carried out.

Since disassembly is only part of the remanufacturing process, a holistic assessment of the suitability of electric bicycle motors requires further consideration. In addition to the process steps to be investigated, a product analysis, market analysis, and suitable business models must be examined to offer a sustainable and market-oriented business model in the field of remanufactured electric bicycle motors.

Funding

This paper evolved from the research project AddRE-Mo and was funded by the Federal Ministry of Education and Research with a Grant No 033R234A.

Conflict of interest

The authors declare no potential conflict of interest with this submission.

Author Contribution Statement

JG and JK wrote the introduction, case study, results, and discussion. JB wrote the state of the art and methodology. JG prepared all the figures. All authors reviewed the manuscript.

Data Availability Statement

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Assessment of the Disassemblability of Electric Bicycle Motors for Remanufacturing

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Abstract

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Introduction

State Of The Art

Methodology

Assessment set-up

Adaptation eDiM

Case Study

Results

General and specific findings during the disassembly

eDiM Analysis and Comparison

Discussion

Conclusion

Declarations

Funding

Conflict of interest

Author Contribution Statement

Data Availability Statement

References

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