Journal of Applied Engineering and Technological Science Vol 3(2) 2022 : 139-148 139 IMPLEMENTATION OF QUALITY IMPROVEMENTS TO MINIMIZE CRITICAL TO QUALITY VARIATIONS IN POLYURETHANE LIQUID INJECTION PROCESSES Nazaruddin Industrial Engineering Department, Faculty Science and Technology, Universitas Islam Negeri Sultan Syarif Kasim Riau nazar.sutan@uin-suska.ac.id Received : 20 May 2022, Revised: 25 June 2022, Accepted : 28 June 2022 *Corresponding Author ABSTRACT PT Topjaya Antariksa Electronics is a manufacturing company that produces various refrigerators, home freezers, and showcase refrigerators. Refrigerators are produced in the form of single doors and twin doors. This company was founded in 1988 and distributed by Toshiba Sarana Utama throughout Indonesia. This research is intended to reduce the process failure rate so that the potential for defects produced in the polyurethane shop is reduced by finding repair solutions. This study aims to plan improvement efforts to reduce process failures in the polyurethane shop and then evaluate the results of implementing the proposal. The FMEA (Failure Mode and Effect Analysis) method is used. This method performs several stages, such as determining the potential failure mode in each process, identifying the cause of failure, and then making a priority order. Process failure in this polyurethane shop is the most significant process failure compared to other shops. This failure causes the defects in the process at the polyurethane shop to be higher than in other shops. In 2019, 2020, and 2021, the number of refrigerator cabinets in the flawed polyurethane injection process amounted to 7,666 units, 8,256 units, and 8,014 units. The percentage of defects compared to the amount of production found in the polyurethane injection process each year was 18.46%, 17.82%, and 18.11%. Keywords: Failure Mode and Effect Analysis, Polyurethane Shop, Process Failure, Risk Priority Number. 1. Introduction The diversity of these products forces manufacturers to continue to improve the quality of the products produced by the wishes of consumers. Defective products are the primary source of waste (Puspitasari, et al., 2017; Ramadhani, et al., 2014). According to (Hidayat and Rochmoeljati, 2020), Quality improvement in large-scale industry or SME scale has been researched and developed to analyze product quality improvements using the FTA (Fault Tree Analysis) and FMEA (Failure Mode and Effect Analysis) methods. The level of product or service quality as expected, carried out using planning, appropriate methods, routine supervision, and corrective action if an unsuitable condition is found so that quality control can be carried out correctly and according to existing standards(Awal & Hasegawa, 2015; Djunaidi & Ryantaffy, 2018). Polyurethane shop has failure problems during the polyurethane injection process with the highest failure rate compared to other processes. The specifications of the polyurethane liquid weight at the time of polyurethane injection set by the company are 2,320 ± 70 grams. If the injection exceeds or is less than the specified specifications, it can cause failure(Fathoni & Hakim, 2019). This failure is in the form of advantages and disadvantages of polyurethane injection in the refrigerator cabinet, resulting in leakage of the inner Liner, dents on the inner Liner, and space between the inner Liner and the surrounding plate. This problematic refrigerator cabinet required disassembly by removing the inner Liner and injecting polyurethane foam. Then after disassembly, this refrigerator cabinet was injected again with polyurethane to get better results. Rework is what causes the company's costs for repairs to be high. For this reason, the failure of the process at this polyurethane shop needs to pay more attention to identifying the cause of the failure and find a solution to repair it so that the number of defects can be reduced(Balaraju, et al., 2019; Faturachman, et al., 2014; Mostafa & Fahmy, 2020). Nazaruddin Vol 3(2) 2022 : 139-148 140 2. Literature Review According to Ahmad and Yusanto (2020), defects are products that do not meet the quality standards set and cannot be continued to the following process stage. This product with reconditioning costs for the repair process. Economically the product can be improved by becoming a better-finished product. The results of previous research showed that five types of defects were found: hollow defects with a probability value of 6.5%, charred defects with a probability of 5.9%, and solid defects with a probability of 6.9%(Gunawan & Tannady, 2016). This study (Joko, 2018) analyzed the causes of defective t-shoes using the FTA and FMEA methods at PT. Industry Panarub. The results of the discussion of this study show the sewing process with a value of 576 and assembling a score of 512. Those who get the highest RPN value have a significant defect rate. Failure Mode and Effect Analysis (FMEA) is one method of evaluating system risks. FMEA can evaluate and analyze components in the system so that it can minimize the risk or effect of a failure rate as a supporting method for evaluating the performance of a system (Imanuell & Lutfi, 2019). The role of the FMEA method itself can be used to determine the risk of accidents in the system (Sukwadi et al., 2017), the risk of component production failure (Hasbullah et al., 2017), supply chain system risks (Liu et al., 2018; Latif, et al., 2018). Research on maintenance analysis by detecting the risk of failure in machines or tools can be used with the FMEA method. As a result, three critical components must be prioritized in maintenance: the stick cylinder, fuel filter, and oil pan (Darmawan et al., 2017). Another study discusses the analysis of machine maintenance in an agro-industry using the FMEA method. The result is three classification categories for performing treatment (Soewardi & Wulandari, 2019). Risk assessment with the FMEA method can use a qualitative value scale by identifying several predetermined criteria. This assessment can optimize the maintenance plan (Arabian- Hoseynabadi et al., 2010) on the ship's main engine. This study used this method to identify the parameters that exist in FMEA, among others (Priharanto et al., 2017; Surya et al., 2017). Failure Mode and Effect Analysis (FMEA) is one method of evaluating system risks. FMEA can evaluate and analyze components in the system so that it can minimize the risk or effect of a failure rate as a supporting method for evaluating the performance of a system (Imanuell & Lutfi, 2019; Islam, et al., 2019; Kusdiantoro, et al., 2019). 3. Research Methods The methodology is a stage in research to determine the steps and framework of thinking in formulating, analyzing, and solving problems. With the research methodology, it is hoped that the flow of problem-solving thinking becomes more focused and systematic so that it will be easier to analyze and draw conclusions. The systematic flow of the research methodology used can be seen in Figure 1. Fig. 1. Framework of Thinking Methodology Nazaruddin Vol 3(2) 2022 : 139-148 141 In this research method, there are two types of data, namely: Primary data is data obtained from a source directly observed in this case, the process of injection of polyurethane liquid at a polyurethane shop. The data obtained include the following. a. Defect data on polyurethane, press, CRF, and vacuum forming shops in August- September 2021. b. Sampling data on polyurethane weight for August-September 2021 at a polyurethane shop for a refrigerator type N-188-JZ. The problem analysis uses FMEA (Failure Mode and Effect Analysis), which consists of several stages. a. Determine the potential failure mode for each process. Identify processes that have the potential to fail to meet process or design requirements. b. Identification of failure effects Identify the effects of failure on both internal and external customers. Identify the effects of each process and their impact on the following process. c. Determine the severity value Determine the severity value based on the consequences/effects arising from the failure. Identify the causes of failure d. Identify potential causes for each process failure using a cause-and-effect diagram. e. Determine the occurrence value Determine the value of how often the cause of failure occurs. f. Identify process controls Identify control methods that can prevent potential failure/cause or detect failure/cause. g. Determining the detection value Determines the value of the system's ability to detect a failure. h. Calculate the value of the Risk Priority Number (RPN). RPN is a number that states the priority scale for quality risk, which is used as a guide in carrying out improvement plans. i. Making a Repair Plan Improvements can be made by prioritizing the process with the highest RPN value. 4. Results and Discussions Identify Critical to Quality The polyurethane shop is a workstation with the most significant number of defects compared to other stations. Other workstations include Press shop, CRF shop, and Vacuum Forming. Defect data obtained from the four processes are as follows: Table 1 - Number of Defects Produced by Each Process Process Type Production Period 2020 August-September (Unit) Press Shop 120 CRF Shop 130 Vacuum Forming Shop 650 Polyurethanen Shop 1.491 Total Product Defect 2.391 Total Production 36.673 A. Identify Potential Failure Modes with FMEA A potential failure mode is a state in which a process could fail to meet process or design requirements(Nazaruddin & Septiani, 2021). The potential failure mode can cause the failure mode in the following process' or the 'effect of the potential failure in the previous process. The following are the potential failure modes of the polyurethane injection process in Table 2. Nazaruddin Vol 3(2) 2022 : 139-148 142 Table 2 - Potential Failure Mode of Polyurethane Filling Product Characteristics Potential Failure Polyurethane Liquid Filling Volume Suitability Advantages of Polyurethane Liquid Filling Disadvantages of Polyurethane Liquid Filling B. Determining Consequences of Process Failure Table 3. effects of each process for each component. The consequences of potential failures that arise in the polyurethane injection process. Table 3 - Consequences of Potential Failure No Types of Potential Failure Consequences of Potential Failure 1 Advantages of Polyurethane Liquid Filling Polyurethane Leakage ▪ Torn inner Liner ▪ The cabinet must be dismantled ▪ Inner Liner cannot be reused Dented Inner Liner ▪ Inner Liner is dented ▪ The cabinet must be disassembled ▪ Inner Liner cannot be reused 2 Disadvantages of Polyurethane Liquid Filling Polyurethane Empty ▪ Cabinet must be dismantled ▪ Innerliner cannot be reused ▪ Between the cabinet and the innerliner there is quite a lot of confined air ▪ Resulting in a fairly large void area in the cabinet ▪ Feels soft in a fairly large area Innerliner Not Sticking ▪ Cabinet must be dismantled ▪ Innerliner cannot be reused ▪ Between the cabinet and the innerliner there is a little trapped air ▪ The void area is small while the surrounding area is filled with polyurethane well ▪ Feels soft when pressed C. Determining the Severity Value Severity is a serious statement about the potential effect of this type of failure on the next component, sub system, system or customer if this failure occurs. The severity values obtained include, among others, in Table 4. Nazaruddin Vol 3(2) 2022 : 139-148 143 Tabel 4 - Severity Value No Types of Potential Failure Effect of Potential Failure Severity 1 Advantages of Polyurethane Liquid Filling Polyurethane Leakage ▪ Torn inner Liner ▪ The cabinet must be dismantled ▪ Inner Liner cannot be reused 7 Dented Inner liner ▪ The inner liner inside the cabinet is dented so that it looks like a lump ▪ The cabinet must be disassembled ▪ The inner liner cannot be reused 7 2 Disadvantages of Polyurethane Liquid Filling Polyurethane Empty ▪ Innerliner cannot be reused ▪ Between the cabinet and the innerliner there is quite a lot of confined air ▪ Resulting in a fairly large void area in the cabinet ▪ Feels soft in a fairly large area 7 Innerliner Not Sticking ▪ Cabinet must be dismantled ▪ Innerliner cannot be reused ▪ Between the cabinet and the innerliner there is a little trapped air ▪ The void area is small while the surrounding area is filled with polyurethane well ▪ Feels soft when pressed 7 D. Determining the Occurance Value Occurance is how often the cause of failure occurs. Occurrence value can be determined based on management's experience so far in dealing with process failure problems in the polyurethane injection process. The occurrence values obtained include, among others, in Table 5. Table 5 - Determination of the Occurance Rating Scale No Potential Failure Causes of Process Failure Occurance 1 Polyurethane Leakage Inner Liner quality is lacking 4 Operator is tired 7 Lack of operator skills 5 Manual injection 7 Injection nozzle stuck 5 2 Innerliner Dented Hot room temperature 9 Operator is tired 7 Injeksi manual 7 Less supervision 7 Innercore doesn't match inner liner 2 Nazaruddin Vol 3(2) 2022 : 139-148 144 3 Polyurethane Empty Operator is tired 7 Lack of operator skills 5 Less supervision 7 Engine cylinder head stuck 5 Polyurethane liquid is not homogeneous 4 4 Innerliner not Sticking Air trapped in cabinet 3 Polyurethane liquid is not homogeneous 4 Lack of operator skills 5 Injection nozzle stuck 5 The material filter is not working properly 5 E. Determining the Detection Value Detection is a number from 1 to 10, where 1 indicates a detection system with high capability or almost certain that a failure mode can be detected. While 10 indicates a detection system with low capability, where the detection system is not effective or cannot detect it at all. The detection values obtained include the following in Table 6. Table 6 - Determination of Detection Value No Potential Failure Current control Detection 1 Polyurethane Leakage Sampling with two samples 4 There isn't any yet 9 Training once a year 3 Work instruction 3 Maintenance once a month 8 Innerliner Dented There isn't any yet 2 There isn't any yet 9 2 Work instruction 3 Supervision 2 Work instruction 6 3 Polyurethane Empty Work instruction 9 Training once a year 3 Supervision 2 Maintenance once a month 7 Work instruction 3 4 Innerliner not Sticking Manual Check 5 Work instruction 3 Training 3 Maintenance once a month 8 Maintenance once a month 8 F. Calculating the value of the Risk Priority Number (RPN) After knowing the severity, occurrence, and detection values for each potential failure mode, then calculating the RPN value. RPN is a number that states the priority scale for quality risk which is used to guide the improvement plan. The RPN value is seen in Table 7. Table 7 - Determination of RPN Value Process Potential Failure S O D RPN P o ly u re th a n e L iq u id In je c ti o n P ro c e ss Polyurethane Leakage 7 4 4 112 7 9 441 5 3 105 Nazaruddin Vol 3(2) 2022 : 139-148 145 7 3 147 5 8 280 Innerliner Dented 7 9 2 126 7 9 441 7 3 147 7 2 98 2 6 84 Polyurethane Empty 7 9 441 5 3 105 7 2 98 5 7 245 4 3 84 Innerliner not Sticking 7 3 5 105 4 4 112 5 3 105 5 8 280 5 8 280 G. Improvement To reduce the number of process failures in the polyurethane filling process at the polyurethane shop, an improvement plan is needed. In making the improvement plan the method used is 5W+1H as a way to find out the solution to the problem. These improvements are listed in Table 8. as follows. Nazaruddin Vol 3(2) 2022 : 139-148 146 Table 8 - Repair Control Table Process Potential Failure Factor Why Where Current control How When Who P o ly u re th a n e L iq u id F il li n g P ro c e ss Polyurethane Leakage Material Inner Liner quality is lacking IQC (Incoming Quality Control) Inspection of two samples at random Inspection of ten samples at random When materials come IQC Staff Man Operator is tired Polyurethane Shop There isn't any yet Two times the change of operator who performs injection every one work shift Replacement is made after half shift time Polyurethane Shop Supervisor Man Lack of operator skills Polyurethane Shop Training once a year - once a year Production Department Nazaruddin Vol 3(2) 2022 : 139-148 147 5. Conclusion Based on the calculation of the capability value of the polyurethane liquid filling process before the repair, the Cp value is 0.41 and Cpk is 0.39. After the implementation of the improvements obtained a Cp value of 0.65 and a Cpk of 0.62. 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