Designing Lean Maintenance Using Total Productive Maintenance Method – A Case Study at Wiring Harness Production

. Consumer demand for 4-wheeled and 2-wheeled motorized vehicles in Indonesia is increasing yearly. In 2022, car sales increased by 18.1%. At the same time, motorcycle sales increased by 3.24%. Automotive companies will compete with each other to meet the needs of consumers in the future. This is also true for automotive parts suppliers. PT XYZ is a company that supplies wiring harnesses for the needs of motorized vehicle components. Currently, the company is facing a problem with overtime of up to 4 hours in several production lines. The company missed the production target because the production plan had not considered any waste that happened on the production floor. Downtime of machines can stop production on the line. Downtime can occur due to machine failure. The company must choose the proper steps for resolution. If waste continues to be ignored, the company will struggle to compete with its competitors. This research aims to solve the waste problem through the Total Productive Maintenance (TPM) Method. Several steps are used to solve the problem: root cause analysis, determining the TPM pillars applied, RCM, and realization of TPM pillars. The research results are lean maintenance design from completing TPM pillars, such as autonomous maintenance, planned maintenance, and development management.


Introduction
Consumer demand for 4-wheeled and 2-wheeled motorized vehicles in Indonesia is increasing yearly.Indonesian Motor Vehicle Industries Association (GAIKINDO) record national car sales reached 1.05 million units in 2022, an increase of 18.1% compared to last year.Regarding brands sold, Toyota still leads the national auto market, followed by Daihatsu, then Honda [1].Meanwhile, Indonesian Motorcycle Industry Association (AISI) record national motorcycle sales will reach 5.22 million units in 2022, an increase of 3.24%.Honda brand still leads sales in Indonesia, followed by Yamaha, then Suzuki [2].Based on this phenomenon, automotive companies will compete with each other to maintain their position in meeting the needs of consumers in the future.This is also true for automotive parts suppliers, who must also be prepared to meet the needs of automotive companies to maintain their position as corporate partners.
Companies capable of competing domestically or globally market continuously improve their production factors, including man, machine, materials, and methods [3].The improvement results can help companies achieve lean manufacturing with the motto "right quantity, right time, and right quality".Lean manufacturing aims to eliminate waste, increase efficiency and productivity, and produce the best quality products at low production costs [4].PT XYZ is a company that supplies wiring harnesses for the needs of automotive companies in Indonesia.A wiring harness is a component that functions to flow electric current and signals in motorized vehicles [5].PT XYZ has many production lines to produce wiring harnesses according to the needs of its customers.Based on the amount of production, the A1 cluster line is the busiest in the company because this line has a high daily target, and production output is relatively more complex than other lines, so there are signs of waste that can be detrimental to the company.Currently, the company is facing a problem, which is the existence of overtime up to 4 hours in several production lines, A1 cluster line is where overtime occurs most often.Overtime is done to meet daily targets to meet production planning.
The company missed the production target because the production plan had not considered any waste that happened on the production floor.Downtime of machines can stop production on the line.Downtime can occur due to machine failure [6].The cause of machine failure is damaged parts or machine abnormality.So, a maintenance process is required to bring the machine back to its prime condition [7].The level of machine damage will affect the duration of downtime.Machine failures can be identified through direct machine inspection by technicians or manpower, as well as through output products with defects [8].
Defects are wastes that result in company losses, and losses can include increased raw material requirements and additional production costs for product rework or reconditioning [9].Factors that cause defects are machines or production tools are not in the best condition.In addition, defects can be caused by human negligence factors [10].More frequently, defective products are produced by a machine, and more frequently, machine downtime is required for maintenance to prevent defects.As a result, overtime continues to occur in the company.
From the waste mentioned earlier, the company must choose the right steps to solve it.If waste continues to be ignored, the company will find it difficult to compete with its competitors.Waste can lead to six major losses for the company, including unplanned stops, planned stops, small stops, slow cycles, production rejects, and startup rejects [11].Waste can also lead to an increase in production costs, which affects the profit received, thus weakening the company's competitiveness [12].
Total Productive Maintenance (TPM) is one of the methods for achieving lean maintenance.TPM aims to achieve "zero defects, zero downtime, and zero accidents" supported by maintenance activities from all elements of the organization [13].Based on previous research by G . Pinto, et al. (2020) conducted on CNC lathes using the TPM method, the results of the study with maintenance activities that focus on planned maintenance and autonomous maintenance.There was a decrease in damage due to failure by 23% for CNC lathes and so on 38% for CNC machining centers, which resulted in improved performance in machine availability, and OEE increased by 5% [14].The implementation of the TPM method aims to solve waste problems in the company.

Research Method 2.1 Value Stream Mapping (VSM)
Value Stream Mapping (VSM) along with the waste generated at each station in the production line.VSM aims to describe the flow of information and materials related to the wire harness production process and show the waste at each station.Waste data that occurred in the company was collected in August-October 2022 before improvement was made.VSM is shown in Fig. 1.

Fig. 1. Value Stream Mapping
Based on the VSM, it is known that the crimping station contributes the most waste defects and downtime than other stations, which will affect the duration of overtime that occurs in the production line.So, it is necessary to investigate the root cause of the waste problem at the crimping station with root cause analysis.

Root Cause Analysis (RCA)
Root Cause Analysis (RCA) at the crimping station detailing the cause of the waste problem.Based on the results of the analysis, it can be seen that 7 root causes cause the main problem.RCA at the crimping station is shown in Fig. 2.

Fig. 2. Root Cause Analysis
From RCA, it can be seen that downtime and product defects have a relationship because when there are product defects, spare parts in the crimping machine are damaged, so machine downtime is needed for maintenance.From this case, it can be seen that handling damaged spare parts can solve 2 waste problems, so handling can be done by a good maintenance system.Product defects caused by manpower default at the crimping station are very rare, mostly caused by the condition of the machine, which is not by its function.Therefore, the manpower factor cannot be considered.Maintenance support activities can affect the duration of downtime, so improvements are needed to reduce maintenance time.

Pillars Diagnose Before TPM
The diagnostic filling was obtained from previous RCA at the crimping station and a direct survey of the production line.If a situation is found that provides the potential for waste, the findings are recorded according to the 8 pillars in TPM.These findings are used as the basis for determining the pillars to solve the problem.Pillar diagnosis before TPM is shown in TABLE I. • Manpower only performs 5S, but not maximized • There are no instructions on how to perform good and correct autonomous maintenance activities Planned Maintenance • Maintenance is still waiting for the damage to the machine part first

• Machine overhaul is only done on a few machines each weekend
• There is no predictive system for machine parts failure

TPM Pilars Problem Problem Findings
Focused Improvement --

Management
Too much time spent on maintenance handling, this increases downtime • The maintenance room does not have good maintenance facilities • The distance between machine failure and the spare parts warehouse is so far

Product defects due to parts damage are still common
• There is no predictive system for the failure of machine parts • Some machines do not have spare parts installed according to machine standards • There is no detection system for machine parts before they are damaged Training and

Office TPM
Maintenance reports and spare parts transactions are not properly recorded in the company's data • Manual recording is carried out by technicians and spare parts warehouse admin, so there is a risk of not being recorded.
• There is no integrated system between production and maintenance regarding machine maintenance From the above findings, it is determined that the pillars that need to be applied to solve waste defects and downtime are autonomous maintenance and planned maintenance.The development management pillar also needs to be realized to reduce downtime.Improvement at another pillar is needed to support maintenance activities.Improvement is expected to fulfill all pillars of TPM and create TPM goals.

Determine the Pillar to be Applied
The TPM method is used to solve this problem.There are several ways to organize and implement TPM.The selection of the pillars is based on the diagnosis of pillars before TPM, which has found problems in the company.TPM pillars used are.
• Autonomous Maintenance (AM) -Consists of the implementation by placing routine maintenance responsibilities in the hands of manpower to extend the mean time between failure (MTBF) of the crimping machine.Manpower maintenance is an activity that is relatively easy to perform.Selecting this activity requires RCM calculations to match the maintenance needs of the crimping machine.Based on the machine maintenance manual book, it is necessary to create maintenance activities based on the priority of machine needs.The maintenance plan is carried out based on the type of machine and divided according to priorities.

Reliability Centered Maintenance (RCM)
A crimping machine is used to assemble wire and terminal as wiring harness raw material with the stamping-bending function to form a piece of the circuit.The crimping machine is shown in Fig. 3.

Fig. 3. Crimping Machine in The Company
The first step in determining the RCM method is to know the breakdown structure of the machine to be analyzed.Breakdown aims to find out the constituent parts or components in the crimping machine so that part ranking can be determined based on its critical level.The breakdown structure of the crimping machine is shown in Fig. 4.    The third step is to determine the most critical component based on the RPN value after ranking.Components with the most critical scores require more handling by technicians.The fourth step is the completion of the RCM decision task, which aims to determine the impact of the failure mode caused and the type of maintenance activity to be performed by technicians or manpower.The fifth step is to calculate the mean time between failure for the most critical crimping machine components, to determine the maintenance schedule according to the lifetime of a part so that failure modes can be avoided.

Decision Task
A good maintenance system is a maintenance that involves all human resources in the company, from the lowest level to the top, so there are autonomous maintenance activities that can be done by manpower and planned maintenance that can be done by technicians.The decision task for autonomous and planned maintenance is shown in TABLE V. Priority planned maintenance is performed on the applicator component by knowing the failure interval caused by the part.In this activity, it is necessary to replace spare parts according to the period of part failure to avoid defects and downtime.The Applicator is shown in Fig. 5.

Calculation of Mean Time Between Failure (MTBF)
The Applicator has 6 types of spare parts (dies) for crimping wire with terminals.These spare parts include a wire crimper, wire anvil, insulation crimper, insulation anvil, slide cutter, and cutter holder.
Wire crimper is the most critical spare part because it has the highest frequency of damage and the highest number of transactions in the warehouse than other spare parts.So, the calculation of MTBF on crimping spare parts focuses on the wire crimper at applicator 8240-0656 at crimping machine 1 based on spare part transaction data in the warehouse.The calculation MTBF wire crimper is shown in TABLE VI.It is known that wire crimper applicator spare parts can reach maximum capacity with 95% effectiveness adjustment, which is 250.000strokes before reaching failure 256.368.The results of the MTBF calculation of the wire crimper at applicator 8240-0656 will be the basis for determining the planned maintenance schedule for the applicator component of the crimping machine in the production line, considering that the shape of spare parts between applicators tends to be the same.

TPM Pillars Realization
• Autonomous Maintenance (AM) -Maintenance performed by manpower.Each manpower is responsible for the condition of the machine he is working on.Activities to be performed by manpower in general for the autonomous maintenance of the components of the crimping machine are as follows.
• Checking the condition and performing 5S on each machine component.• Apply lubricant to dry machine components.
• Actively report the condition of the machine being worked on.Autonomous maintenance is routinely performed before and after each shift.An autonomous maintenance checksheet is designed so manpower performs its activities.The checksheet can provide a marker for the activities that have been performed.The autonomous maintenance checksheet is shown in Fig. 6.Planned applicator maintenance is performed according to a schedule based on the most frequently damaged part.The part is a wire crimper.The planned maintenance schedule for the applicator component of the crimping machine according to production capacity is shown in TABLE   • Development Management -Planned maintenance of applicators is performed in the maintenance room because applicators are small and easy to disassemble in the crimping machine, so the maintenance room needs to be optimized by implementing 5S.The goal is to centralize the maintenance process, have complete tools and equipment, and be close to the spare parts warehouse to reduce material handling time.The implementation of 5S in the maintenance room is shown in Fig. 8 and 9.

TPM Perform Plan
It is expected that the company can apply the previous TPM pillars realization while running its production system.The application of TPM pillars can help companies achieve lean maintenance.According to the checksheet, the application of Autonomous Maintenance (AM) is expected to reduce the incidence of unplanned downtime of crimping machines and extend the MTBF of each component.The implementation of Planned Maintenance (PM) according to the maintenance schedule and check sheet is expected to reduce the incidence of unplanned downtime of crimping machines and reduce the accumulation of defects caused by crimping stations by 50%.and application of development management can help technicians to be more effective and efficient in performing maintenance of crimping machine components if previously there was unplanned downtime in the production line with an average of 60 minutes, it can be planned downtime with a duration of no more than 20 minutes.The application of TPM can increase the cooperation and responsibility of all participants involved in it, from workers to technicians and managers.

Conclusion
Designing lean maintenance is expected to solve a waste problem that exists in wire harness companies.From 7 root problems in the crimping station described, the implementation of 3 pillars of TPM was selected to solve them.The pillars selected were autonomous maintenance, planned maintenance, and development management.Application of TPM in the company can greatly influence smooth production and reliability of production machines, so companies can achieve lean manufacturing.
Implementing lean manufacturing aims to reduce product defects caused by crimping stations, eliminate unplanned downtime due to machine breakdowns and replace it with planned downtime of shorter duration, and reduce the frequency of machine breakdowns so that the main problem of overtime can be avoided.In addition, further improvisation is needed to maximize TPM implementation to support the pillars that have not been achieved, such as developing information systems or adding production aids.To maintain the performance of all parties involved, training and education are also needed, as well as good HSE implementation.

Fig. 4 .
Fig. 4. Breakdown Structure of Crimping MachineThe second step is to determine the failure mode caused by each component from the crimping machine.This determination will be a calculation of the RPN value.The failure mode determines the calculation will determine the value of severity (S), potential cause failure will determine the value of occurrence (O), and current control will determine the value of detection (D).From this, RPN value will later become an aspect of the ranking failure scale of parts and activities.Following are the results of analyzing and calculating the failures and calculating S, O, and D values on each component that makes up the crimping machine.RPN calculation value is shown in TABLE II to TABLE IV.

Fig. 6 .
Fig. 6.Autonomous Maintenance Checksheet provide a marker for activities that have been performed.The planned maintenance checksheet is shown inFig 7.

Table 3 .
Value Occurrence

Table 4 .
Value Detection Machine failure is noticed by man power or technicians during production process inspection Easy 2 Machine failures are known by manpower when they produce defects on the spot.Medium 3 Machine failure is known when it produces defects in the quality control process.Hard 4 Machine failure is only known after machine breakdown by technicians Very Hard 5

Table 5 .
Decision Task Maintenance

Table 7 .
Planned Maintenance Schedule For Applicator