AIP Conference Proceedings [AIP Publishing THE 5TH INTERNATIONAL CONFERENCE ON INDUSTRIAL, MECHANICAL, ELECTRICAL, AND CHEMICAL ENGINEERING 2019 (ICIMECE 2019) - Surakarta, Indonesia (17–18 September 2019)] THE 5TH INTERNATIONAL CONFERENCE ON INDUSTRIAL, MECHANICAL, ELECTRICAL, AND CHEMICAL ENGINEERING 2019 (ICIMECE 2019) - Strategic planning in procurement of raw materials based on Kraljic’s purchasing portofolio model