Manufacturing
CNC & Machining
5 self-contained study topics — notes, diagrams, formulas, and worked examples for exams and GATE.
Topics
- NC/CNC BasicsNC/CNC machines position tools in programmable increments; the basic length unit (BLU) is the smallest commandable movement, and resolution depends on it. Open- vs closed-loop control determines accuracy, per PN Rao.
- Part ProgrammingPart programs use G-codes for motion (G00 rapid, G01 linear, G02/G03 circular) and M-codes for machine functions. Coordinates, feed F, and speed S define each block, per PN Rao.
- Tool Path PlanningTool-path planning chooses the pattern (raster, contour, spiral) and step-over so adjacent passes overlap; step-over = tool_dia × (1 − overlap). Scallop height and machining time follow from it, per PN Rao.
- Adaptive ControlAdaptive control adjusts feed and speed in real time to keep a measured variable (force, power, torque) at its limit, maximising material removal rate within constraints, per PN Rao.
- CNC Machine ElementsCNC precision depends on elements like preloaded ball screws (low backlash), linear guideways, and feedback encoders. Pitch error = actual lead − nominal lead limits positioning accuracy, per PN Rao.