APPLICATION AND ANALYSIS OF GEOMETRIC DIMENSIONING AND TOLERANCING OF ASTRA MANUFACTURING POLYTECHNIC MINI CNC MILLING MACHINES CONSTRUCTION

• Main Author: Syaifullah, Herry
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43771
• Institution: Institut Teknologi Bandung

Astra Manufacturing Polytechnic or better known as Polman Astra since 2009 provides scholarships for outstanding students to cover 35% of the total number of students recruited from all over Indonesia. In addition to providing scholarships, as a form of implementation of tri-dharma perguruan tinggi (the threeresponsibilities of higher education), Polman Astra also has a vocational development program. Polman Astra is currently developing a mini CNC milling machine that can be used as a learning medium for the Vocational School. The machine has a compact size so that it is expected to be in accordance with practical learning in vocational schools that have limited space and fund. The mini CNC milling machine developed has a construction made of welded base mild steel plate. The construction of the mini CNC milling machine has been made and assembled by Polman Astra students as a group project, however during the design process, it has not implemented the exact geometric dimensions and tolerances specifications. Therefore it is necessary to conduct an evaluation the mini CNC milling machine construction by analyzing its the geometric dimensions and tolerances. The final goal of this research is to ensure the construction of the mini CNC milling machine in good condition before the next process is carried out namely the installation of control system devices. The first stage of the analysis was reviewing the machine construction. The review included data collection and redrawing the machine, demanded machine specifications, checking and measuring the results of the construction of the machine. Then it proceeded with the identification of key characteristics. Key characteristics identified included performance and geometry demands of the entire machine construction. Next step is analyzing the geometric dimensions and tolerances through stack up tolerance analysis. The analysis was carried out through six steps, namely: determining key characteristics, generating loop diagrams, changing the mean tolerance and selecting tolerance and variation analysis method. The analytical methods used were the worst case method and the RSS method. The tolerance values must be verified for adjustment with the workshop manufacturing capability and the final stage of research was generating technical drawings. iii Twenty variable tolerances were adjusted to obtain a deviation of 0.1 mm. The results of the analysis show that all the final tolerances of the variable tolerance for the worst case method resulted in tight tolerance values with a 100% probability in the desired gap. Therefore, the analysis method was changed to RSS method and resulted in tolerance values that were more wider, which were likely to be 99.73% within the desired gap.