Assessing Cleaning in Remanufacturing: A Case Study of Shot Blasting Efficiency to Alternator Design

Cleaning is a crucial step in the remanufacturing of end-of-life components. The main purpose of cleaning is to remove all contaminant items such as dirt, oils, dust in order to facilitate the process of core inspection before moving on to the subsequent step to complete the remanufacturing activity. However, there are issues/challenges related to the cleaning methods that affect the process efficiency. It has also been reported that the cleaning process is time consuming and has adverse impact to the environment. Cleaning is directly influenced by the various cleaning methods and the design features of each core/incoming parts. Therefore, the aim of this paper is to evaluate the effectiveness of shot blasting cleaning method from core design perspectives in the case of an alternator. The results will be assessed based cleanliness level after the cleaning process on the core surface, complex shape, geometry, and joining method. The outcome demonstrates that the complexity of the core design also affects the cleaning process efficiency. According to the study shot blasting cleaning method without any pre-treatment process was insufficient to fully clean the core. Hence, it is suggested that considering certain parameters of the shot blasting medium, such as size, type, and shape variations, can enhance the effectiveness of shot blasting as a cleaning method for used alternators in remanufacturing.


INTRODUCTION
Cleaning is a crucial step in the remanufacturing process due to its impact on environmental sustainability.Cleaning is part of the manufacturability indicator and plays an important function in guaranteeing the quality of a remanufactured part or component.Cleaning stands out as one of the most critical and integral stages in the process of remanufacturing.Remanufacturing is widely recognized as a significant process of the overall manufacturing sector, playing a pivotal role in advancing the principles of the circular economy (Zhou et al. 2016).It is the only recovery activity that provides the same quality, performance, and warranty as to the brand-new products and involves a process of remanufacturing a used product to the performance criteria outlined by the original equipment manufacturer (OEM) (Ijomah 2009).Remanufacturing process comprises a detailed procedure of disassembly, cleaning, inspection, restoration, reassembly and finally testing before ready for shipment (Matsumoto et al. 2016).As presented in figure 1, several cleaning activities are conducted throughout a remanufacturing process.The main purpose of cleaning in remanufacturing activity is to remove contaminants from the core to facilitate failure detection, prepare surfaces for the next process and eventually to meet the quality requirement for the remanufactured product.These contaminants can be in the form of dust, oil, rust, carbonized sediment, paint residues, and many other forms.The typical cleaning methods are thermal washing, dry blasting, wet-blasting, and ultrasonic vibration.As pointed out by Liu et al. (2013), cleaning can be conducted at multi stages of remanufacturing process to remove all contaminated item.Cleaning in the remanufacturing process serves as the foundation for detect parts surface dimension accuracy, geometry accuracy, roughness, surface performance, wear and adhesion and other indicators (Gong et al. 2018).This step significantly influences subsequent activities such as the surface analysis, surface detection and assembly etc. in next remanufacturing process.Moreover, it has a direct impact on the overall quality and cost of remanufactured goods, making it an essential and indispensable procedure within the field of remanufacturing engineering.Therefore, the aim of this paper is to evaluate the effectiveness of shot blasting cleaning method from design perspectives with focusing on the surface, design complexity and joining method in an alternator housing.
FIGURE 1. Common cleaning process in remanufacturing adopted from (Liu et al. 2013)

CASE EXAMPLE: AN ALTERNATOR
In this paper, an alternator was chosen as a case example.The alternator, as the core is to be cleaned using the shot blasting technique with a custom shot blasting machine.
Alternator is an automotive part with the highest remanufacturing rate, Alternators are much produced worldwide to fulfil the demand especially in automobile usage.The main function of an alternator is to deliver electrical energy to charge the battery and to the on-board equipment such as light.A common issue that can arise over an alternator's lifespan is the occurrence of a fractured contact on the diode plate (Kim et al. 2009) .After the used core is sent back, it undergoes a comprehensive electrical and mechanical restoration, including the installation of new bearings or carbon brushes as part of the remanufacturing process.The cost incurred only 50% from the new price.Figure 2 show an exploded view of an alternator with its parts and component name while Figure 3 represent the various remanufactured alternator in market cited from BOSCH website.Gong et al. (2018).Mostly this pollution also contribute from chemical usage as a cleaning medium for example, Long et al. (2019) mentioned used of strong or mid-strong acids to remove oxides from part surfaces in remanufacturing, painting, metallurgical and mineral industries will contribute to the generation of waste which harmful to the environment.A good company will certainly take into account its impact on the environment, but it is often stated that total waste generation is one of the failure factors in this cleaning process (Abu et al. 2014).
Others issues such as factors causing cleaning difficulties was reported by Sitcharangsie et al. (2019).They highlight (a) complex structure: shape and geometric dimensions,(b) material: hardness ,composition ,thermal stability (c) excessive debris: density and thickness of the contaminant, on and inside the core's complexity of cleaning methods (d) environmental regulations and (e) corrosion form of output (whole units or part level) as the factors causing difficulties in cleaning process.In perspective of process efficiency, (Sundin 2001) has mentioned, from the technical analysis showed that the bottleneck in the remanufacturing process was the cleaning step, while Chang et al. (2013) also stated that the cleaning process to remove contaminants is the most timeconsuming and labor-intensive job.Furthermore, cleaning efficiency could affect from the core design.Four major designs aspects, namely material selection, material joining methods, structure design and surface coating methods has been identified in the previous study.Yang et al. (2016).Hence the challenge in cleaning for remanufacturing activity can be classified as per table 1 shown below: In this case, shot blasting was performed to the core (used alternator) with the intention of observing the real impact of shot blasting cleaning method from the perspective of the 'core' design focusing on its housing.There is no chemical consumption in this case as a precleaning in order to avoid hazardous waste generation with the potential as a pollution to the environment.This procedure used the custom shot blasting machine as per shown in Figure 5.This machine was designed based on the capacity usage for smaller parts as compared to the previous one which was huge and requires higher energy consumption.Aluminum was used as an abrasive medium in this shot-blasting process as shown in figure 6.

SHOT BLASTING PROCEDURE
Figure 7 represent the shot blasting step in this case study, the first step is to inspect the alternator to identify the areas that need cleaning.Refer picture 1: incoming core (used alternator).Note any areas with rust, paint, or other contaminant.Then, the alternator part and component were disassembled to obtain the alternator housing shown in picture 2. Before perform the shot blasting process, the safety precaution and machine were set up properly according to the technical standard as per shows in Table 3. Figure 5, shows the shot machine blasting machine in FIGURE 7. Shot blasting cleaning step this operation.With this equipment, the operator places the part to be shot blasted and observes through a viewing window.Additionally, the operator can examine and adjust the part's position using the integrated access gloves within the machine.Detail cleaning (refer picture 3 & 4) was conducted by inspecting the alternator's surface, structure, and geometry for any remaining contaminants or areas that require additional cleaning.A brush was used to remove any residual abrasive media and loosen any stubborn contaminants.Post blasting procedure was performed by inspecting the alternators to ensure that it is clean and free from rust, paint, and other contaminants.Blow compressed air over the cleaned surface to remove any loose particles.
Once the blasting process is finished the residual blasted powder material should be washed away manually.At the end of this operation, the shot blasting machine and nozzle have been cleaned properly to prevent clogs and ensure its longevity.

RESULTS AND DISCUSSION
The core (used alternator) was not in good condition upon receipt, as depicted in Figure 8, with noticeable scratches on the housing surface and a broken section of the housing structure.However, despite these issues, the decision was made to proceed with shot blasting cleaning for this core.
During the process, the alternator was manually disassembled, revealing contamination on the housing in the form of dust, dirt, and oil.It took approximately 5 minutes to achieve a clear surface on both the inner and outer parts of each housing.Figure 9 & 10 provide a visual comparison of the alternator's condition before and after the shot blasting process.Table 4 show a detail observation after the shot blasting was conducted to the use alternator housing.The observation focusing the surface core, core design and joining method.The alternator housing is made of aluminum alloy casting.Some scratches and a broken part were already there on its surface before we used the shot blasting method.Importantly, the shot blasting process did not cause more damage.
Even with the scratches and the broken part, the housing stayed strong and undamaged after the shot blasting treatment.
Core design: Complex design, Structure shape Geometry, Dimensions, Orientation The housing features intricate design with complexities involving its structure shape, geometry, dimensions, and orientation on both the left and right sides.While carrying out the cleaning process, challenges arose when trying remove dirt & oil at the small edge and radius at the housing.

Joining method
The alternator housing is fastened using bolts and nuts.The threading on the housing was effectively cleaned, and there were no signs of damage after the shot blasting process.As a result, the housing can be readily assembled using bolts and nuts without any issues."

CONCLUSION
From the observation, found that some dirt, dust and oil still exist at the small edge and radius of the core.These results reveal that the complexity of the core design also affects the cleaning process efficiency.Even though it looks like the dirt has disappeared from the housing surface, it does not look like new.Remanufacturing however requires components to be returned to "as good as new."Therefore, the pre-treatment cleaning using appropriate chemical should be consider as a part of remanufacturing cleaning process.In addition, the aim of cleaning process was not only to remove the contaminants from the core but also to facilitate failure detection, prepare surfaces for the next process; and to make it meet the quality requirement after being remanufactured.The study concludes that the shot blasting cleaning method without any pre-treatment process was insufficient to fully clean the core.In this case, Aluminum Oxide with an F80 grain size of 150~212µm has been used as the cleaning chemical (blasting medium).Hence, it is suggested that considering certain parameters of the shot blasting medium, such as size, type, and shape variations, can enhance the effectiveness of shot blasting as a cleaning method for used alternators in remanufacturing.

FIGURE 2 .
FIGURE 2. An exploded view of alternator cited from (Fang et al. 2015)

TABLE 3 .
Shot blasting technical specification

TABLE 4 .
Evaluation of shot blasting cleaning effect in design perspectives