Design Optimization Analysis of Grass Chopper Machine Through the Application of Design for Manufacture and Assembly (DFMA) Approach

Abstract

The livestock sector in Indonesia necessitates efficient grass chopper technology to enhance animal feed productivity. However, conventional grass choppers continue to exhibit design complexity, elevated production costs, and assembly inefficiencies that impede technology adoption at the farm level. This study aims to analyze and redesign the grass chopper by applying the Design for Manufacture and Assembly (DFMA) approach to optimize operational efficiency and reduce manufacturing expenses. The research method employs a Design-Based Research (DBR) framework encompassing problem identification, documentation of the existing design via the Bill of Materials (BOM) and Operational Process Chart (OPC), design evaluation using DFMA principles, redesign implementation, and financial feasibility analysis. DFMA implementation is executed through three strategies: reducing component count in the chute output and cover assemblies, optimizing material thickness from 3 mm to 2.5 mm based on CAE simulation results, and incorporating a hopper feature for automatic feeding. The study results indicate a marginal increase in production time of 3.29% (from 730 to 754 minutes), which is considered negligible relative to the added value. From a financial perspective, the Cost of Goods Sold (HPP) decreased substantially from Rp. 171,202,626.53 to Rp. 3,277,373.33 per unit; the profit margin increased from 10.56% to 27.17%; the Net Present Value (NPV) rose from Rp. 55,845,740.49 to Rp. 365,135,757.34; and the Internal Rate of Return (IRR) improved from 26.22% to 81.30%. With a unit selling price of Rp. 4,500,000, the redesigned product remains competitive in the market, offering a payback period of two years, thus presenting a financially viable solution for developers and enhancing the likelihood of adoption by local farmers.