TIME ANALYSIS OF THE MIXING PROCESS OF FIRE BRICK MATERIALS IN PT. BENTENG API TECHNIC GRESIK

PT. Benteng Api Technic is a leading refractory company in Indonesia with refractory bricks as one of its superior products. The process of making refractory bricks that will be observed in this study is the process of mixing materials and the molding process. In the mixing process, there are no tools in the form of time indicators to help operators make decisions about the mixing time of ingredients. This research aims to obtain the time for the mixing of materials with maximum mixing quality and to support the press process optimally. The research was conducted using a perfectly randomized experimental design in order to obtain different mixing results based on the nine selected mixing time treatments. Measurement of working time is carried out using the stopwatch time study method on press operators who are experienced in their fields. Calculations to align the two processes using a Gantt chart with idle time as an indicator. The experimental results revealed that the most optimal mixing with a mixing time of 12 minutes resulted in 7.2 kilograms of mass that did not pass through an 18 mesh sieve. Based on the results of the gantt chart, the use of 11 mixing time for material B resulted in the lowest idle time of 178 minutes. The processing time obtained is expected to be used as a guide in determining the time input on the time indicator tool in the process of mixing refractory bricks.


INTRODUCTION
Brick is a common building material, however there is a specialized variety known as firebrick that has a strong resistance to flames (Khattab et al., 2021). As a barrier against high temperatures in the combustion chamber or between high temperature manufacturing machinery and the surrounding environment, refractory brick is utilized. Because refractory bricks play a crucial role in the high-temperature production process, the production process of refractory bricks must adhere to the proper procedure. Mixing is the random distribution of materials or particles under specific circumstances and time constraints (Febrianto, 2021). In this study, the author is primarily concerned in the dispersion of the material mixture. Because it is the beginning step in the production of refractory bricks, the even distribution of the mixture during the material mixing process is deemed essential. Two workers employ a mixer machine to combine the materials.
Standard operating procedures, or SOPs, for a firm's production will ensure that every production process runs smoothly if the company has regulated its execution (Rifka, 2017). Standard operating procedures must be explicit in order to give personnel with guidance for carrying out tasks or operating machines during the manufacturing process (Leonardi, 2011). The company has established a standard time of 15 minutes, while the graph below depicts the observation time. The impact of the time instability on the mixing process of ingredient A does not appear to have a certain effect, while in the process of mixing material B, lumps of material arise (Nguyen, 2009). After checking the humidity in the normal mass with the clotted mass, it was found that the clotted mass had higher humidity than the ordinary mass. The clumping mass has a humidity value of 70.4 RH while the ordinary mass has a humidity value of 61.3 RH.
At this time the target set by the company is 1000 bricks per machine, if one stone requires 3.9kg mase and there are 2 press machines, the mass required to meet the target is 7800kg mase. This need is fulfilled by mixing 26 times with a total time of 276.59 minutes or only using 65.8% of the available working time. Therefore, optimization can be done to get results according to production targets with minimal idle time (Asadi & Vahidi, 2010;Ghafoorpoor Yazdi et al., 2019;Montazeri-Gh et al., 2006;Shrouf & Miragliotta, 2015).
Based on the existing problems in the form of using working time that is not optimal and the emergence of lumps in material B, the research objective was set to get the process time for mixing material B with lumps that did not pass the minimum 18 mesh sieve and obtain a process that is in harmony between the mixing process and the press process. So that the research results can be used as a guide in planning and controlling the production of refractory bricks, especially in the process of mixing materials and the press process.

RESEARCH METHOD
A stopwatch is an instrument used to collect data on the cycle time of brick printing operators. The sieve is a piece of experimental equipment in the form of a wooden box with an 18-mesh hollow wire that is used to determine the number of lumps created during the treatment of mixing time. Observational data will be recorded and documented using stationary and mobile phones so that Excel can be used for data processing. The flow utilized in this study is as follows:

Figure 3 Research Flow
Research activities begin with field studies and literature review to determine appropriate steps to achieve research objectives. Using the stopwatch-time study method as an activity carried out to determine the standard time to complete the work, in which the measurement results will be used as a standard for completing the work ((Wignjosoebroto, 2000) in (Leonardi, 2011)). Using a perfectly randomized experimental design method to examine the impact of the treatment of 9 variations of mixing time on the number of agglomerates that pass through an 18 mesh sieve. Gantt charts are used to simulate the daily production process to determine the length of mixing time which creates the production process with the least idle time (Geraldi & Lechter, 2012;Kumar, 2005;Ong et al., 2016;Seymour & Hussein, 2014).   15  230  384  57  44  149  418  31  16  126  316  38  45  122  362  29  17  137  572  46  46  127  346  46  18  165  398  41  47  139  392  37  19  170  472  37  48  152  507  36  20  224  435  42  49  196  796  42  21  153  528  32  50  178  463  37  22  126  423  32  51  135  383  45  23  120  392  38  52  138  390  41  24  143  374  35  53  125  410  38  25  169  418  31  54  122  492  57  26  161  429  39  55  128  503  31  27  241  387  41  56  200  386  36  28  205  689  37  57  174  378  30  29  145  451  46  58  152  692  32  59  149  400  42  69  127  439  28  60  132  472  35  70  148  533  41  61  147  469  39  71  154  472  44  62  167  451  31  72  112  526  36  63  124  539  42  73  245  400  40  64  183  389  31  74  123  385  35  65  152  389  35  75  133  359  32  66  149  352  30  76  100  493  45  67  142  421  37  77  210  460  43  68  141  376  32  78  135  365  27 Based on the time of the mixing process for material A, the cycle time of each element is obtained. Cycle time is determined by calculating the average of each work element as follows: Ws =  After statistical tests were carried out in the form of data adequacy tests and data uniformity tests, there was a change in the cycle time of the mixing process for material A as follows: The calculation of the performance rating and the allowance factor is only used for work elements that involve humans in most processes. Where in the process of mixing material b which is subject to performance rating and the allowance factor is work element 1, namely pouring material. The following is the performance rating table along with the allowance factor: The calculation is continued by determining the normal time and standard time for all work elements as follows:

Material A Mixing Process Time
a. Normal Time Wn = Ws x performance rating    Based on the processing time of press material B, the cycle time of each element is obtained. Cycle time is determined by calculating the average of each work element as follows:  After statistical tests were carried out in the form of data adequacy tests and data uniformity tests, there was a change in the cycle time of the press process for material B as follows: Determination of the performance rating and leeway factor for all elements of work as follows:     Observational data will be analyzed for variance and Student Newmans Keuls test to determine the differences caused by each treatment. Based on the ANOVA calculation, it can be seen that F > Fα, it is concluded that there is a significant difference caused by the difference in treatment in the experiment. Furthermore, the range test was carried out with the Newman Keuls test.

Newman Keuls Test
Follow-up testing to determine the significance of the difference between treatments using the average of each treatment. The average of each treatment is arranged sequentially from the largest average as follows: The range value obtained must be multiplied by the average standard error value for each treatment so that the smallest significant range table is obtained as follows: The optimal experimental result in this experiment is the last treatment that gets a difference > RST when compared to the smallest average. In the comparison table what is meant is the comparison of numbers. The last comparison that gets a meaningful difference predicate.

Gantt Chart
The simulation of the working process time between the mixing process and the press process is displayed in the form of a gantt chart to determine which mixing process time should be selected using variations of mixing time (Seymour & Hussein, 2014). The gantt chart is made with the following process requirements: 1) The mixing process time is the time to process 2 times until the mass container box with the mass of material B 600kg 2) Time The mixing process can be separated according to the constituent elements of time if needed. 3) The Processing Time of Press 1 and Press 2 is the same 4) The press processing time is the time to complete 1 box of mase container with a mass of material B 600kg using only 2 work elements. 5) There are 3 preparation times, namely, initial machine preparation for 10 minutes, machine preparation after a break for 5 minutes, preparation for ending production for 15 minutes.

INTERNATIONAL JOURNAL ON ADVANCED TECHNOLOGY, ENGINEERING, AND INFORMATION SYSTEM (IJATEIS) Volume 1 ISSUE 2 (2022)
6) There are no production activities at the time of preparation except for the completion of the process at the time of preparation for ending production. 7) The press process can only be started after the mixing process except at the beginning of the production it will be started by using the existing safety stock on the previous day.
The variation of the mixing process time used for material B is the treatment variation listed in the experimental results table, namely 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, and 13 minutes, 14 minutes and 15 minutes.
The recapitulation of mixing time for material B and press time for material B with 9 variations of mixing time used in making the gantt chart is as follows:  47 47 47 47 47 47 47 47 47