THE EFFECT OF COOLING MEDIA VARIATION AND SPINDLE SPEED VARIATION ON ROUGHNESS OF SPECIMEN SURFACE IN FINISHING PROCESS USING CNC PU LATHE MACHINE

Perkembangan teknologi komputer mengalami kemajuan yang pesat seperti pengaplikasian pada mesin perkakas (mesin frais, bubut, gerinda, las, dan lain-lain). Perpaduan hasil teknologi komputer dengan mekanik ini telah menghasilkan mesin perkakas yang dinamakan Computer Numeric Controlled (CNC). Namun, terdapat kendala dalam proses pendinginan benda kerja yang disebabkan keausan alat potong, kecepatan potong, jalan pemakanan, dan kedalaman pemotongan. Penelitian ini dilakukan untuk menguji pembubutan dengan bahan baja S45C dengan memberi variasi media pendingin coolant dromus, udara bertekanan, dan tanpa pelakuan (tanpa coolant) dan kecepatan putaran spindle 1400 rpm, 1650 rpm, 1950 rpm.

Jenis penelitian ini termasuk dalam penelitian eksperimen. Penelitian ini dilaksanakan bulan Februari—Maret 2020 di PT Tjokro Putra Perkasa Sidoarjo. Penelitian ini menggunakan tiga variabel, yaitu jenis variasi pendingin dan kecepatan putar spindle (variabel bebas), tingkat kekerasan permukaan baja S45C pada proses bubut CNC (variabel terikat), dan seluruh faktor yang mempengaruhi tingkat kekasaran permukaan pembubutan CNC selain variasi pendingin dan kecepatan spindle (variabel kontrol).

Berdasarkan hasil penelitian dapat disimpulkan (1) terdapat pengaruh yang signifikan antara variasi media pendingin dan kecepatan putar spindel terhadap hasil kekasaran permukaan benda kerja S45C pada proses finishing menggunakan mesin bubut CNC PU; (2) variasi media pendingin berpengaruh terhadap nilai kekasaran permukaan; (3) variasi yang paling rendah nilai kekasarannya yaitu media pendingin coolant dengan kecepatan putar spindel 1950 rpm menghasilkan nilai kekasaran 2,771 µm, dan variasi yang paling tinggi nilai kekasarannya adalah variasi media pendingin udara bertekanan dengan kecepatan putar spindel 1400 rpm menghasilkan nilai kekasaran 3,313 µm.

Kata Kunci: Kekasaran, kecepatan putar, pendingin, CNC, baja S45C.

The development of computer technology has experienced rapid progress such as the application of machine tools (lathes, milling machines, grinding machines, welding machines, etc.). The combination of the results of computer technology with mechanics has produced a machine tool called Computer Numeric Controlled (CNC). However, there are obstacles in the workpiece cooling process, workpiece roughness caused by wear and tear that is often used and cutting speed, feed rate, and depth of cutting. This research was conducted to test the turning with S45C steel material by giving variations of the coolant dromus cooling media, compressed air, and without treatment (without coolant) and spindle rotation speed of 1400 rpm, 1650 rpm, 1950 rpm.

This type of research is included in experimental research. This research was conducted in February-March 2020 at PT Tjokro Putra Perkasa Sidoarjo. This study used three variables, namely the type of cooling variation and the spindle rotational speed (independent variable), the level of hardness of the S45C steel surface in the CNC lathe process (the dependent variable), and all the factors that influence the level of roughness of the CNC turning surface in addition to the cooling variations and spindle speed (control variable).

The results of the study it can be concluded (1) there is a significant influence between the variation of the cooling media and the spindle rotational speed on the surface roughness results of the S45C workpiece in the finishing process using a CNC PU lathe; (2) the variation of the cooling media affects the surface roughness value; (3) the variation of the lowest roughness value is coolant cooling media with 1950 rpm spindle rotational speed resulting in roughness value 2,771 µm, and the highest variation of roughness value was variation of pressurized air cooling media with spindle rotational speed of 1400 rpm resulting in roughness value 3,313 µm.

Keywords: Roughness, rotating speed, cooling, CNC, S45C steel.