Development of a Low-Cost Computer Numerical Control (CNC) Retrofit Kit for Conventional Lathes in Nigerian Small and Medium-Scale Manufacturing Enterprises

The widespread prevalence of aging conventional lathes in Nigerian small and medium-scale manufacturing enterprises (SMEs) represents a critical bottleneck to productivity growth and product quality improvement across the manufacturing sector. Full replacement of these machines with purpose-built computer numerical control (CNC) systems is prohibitively expensive for most operators in the low-income manufacturing segment. This study presents the design, development, and experimental validation of a low-cost CNC retrofit kit specifically engineered for conventional lathes operating within the Nigerian manufacturing context. The retrofit system integrates a three-axis stepper motor drive assembly, an Arduino Mega 2560-based open-source controller, a custom-designed spindle encoder feedback module, and a Linux CNC-compatible software interface, achieving axis positioning repeatability of ±0.025 mm under cutting conditions representative of Nigerian workshop environments. A cost analysis reveals that the prototype retrofit system was realized at approximately NGN 485,000 (approximately USD 320 at the 2024 exchange rate), representing a reduction of more than 85% relative to commercially imported entry-level CNC turning centers. Experimental cutting trials on medium-carbon steel (AISI 1045) workpieces demonstrated surface roughness values averaging Ra = 1.62 µm and dimensional tolerances within IT8 grade, performance that is directly comparable to entry-level imported CNC lathes. The study identifies the dominant cost drivers, evaluates the system against established CNC performance benchmarks, and discusses scalable implementation pathways for Nigerian SMEs. The findings affirm the technical and economic viability of open-source CNC retrofitting as a democratizing strategy for precision manufacturing capability in Sub-Saharan African industrial contexts.