1. Numerical Control

2. Machines Machines are everywhere  Utility machineries eg. Buses, Planes  Manufacturing machineries eg. Injection moulder  Tool-making machineries eg. Lathes, Drills Tool-making machines are most relevant to Design Engineers

3. Manual machines Control by levers, cams, etc. Can you identify common operations?

4. Dimensions of control On/Off, Speed Linear motion  Position  Direction Circular motion  Angle Process specific  Tool changes  Current

5. Control system Input – Compare – Output Input: Sensors Compare: Computer Output: Servo motor, speed controller, etc.

6. How a NC machine know its state? Open-loop  Initialisation  State updated on every operation Close-loop  State feed-back from sensors

7. How a NC machine know its state?

8. Sensors Limit switches Electronic position sensors

9. Control system Small, reliable computer Data input and storage Execute control code Drive peripherals and motors

10. Output Most common output is servo motor A smart motor that can turn a specific, small angle accurately The control system send a PULSE On receiving the PULSE, the motor turn an angle (an increment)

11. Output

12. Drive Ball-screw connected with the servo motor Most CNC controller can specify up to 0.001mm Good CNC can achieve 0.001mm position accuracy Low-end CNC can achieve around 0.01mm

13. Limit of resolution 0.001 X 0.001 mm theoretically Freeform curves and surfaces are approximated

14. Real-world limitations In real-world it is affected by  Motor start/stop  Backlash  Momentum  Vibration

15. Tool paths The most common control code for NC machines is G-Code Specialised NC tool-path generators (sometime categorised as CAM applications)  WorkNC  HyperCAM  MasterCAM Tool-path generation modules  Pro/E NC-POST  CATIA  Unigraphics

16. Tool-path generation Define machine steps Generate proprietary codes Convert proprietary codes to G-Code Transfer to NC controller

17. Tool-path generation

18. Common CNC milling tool-path types Rough cut UV cut Parallel plane cut Pencil trace

19. Machining issues CAM operator has to know  Tool radius  Flute length  Tool length  Machine’s zero position  Workpiece’s zero position  Machine’s working envelope  Clamp and fixture position

20. CAD issues Surface gaps Boundary edges Minimum radii

21. 5-axis Machining Capable of approaching a tool from an optimum direction.  The metal molds can be machined by cutting, which have been able to be machined only by a spark erosion machine. Capable of machining the workpieces by one-time chucking, where conventional machines require setup change.  Reduce metal mold manufacturing time (lead time).  Labor-saving, unmanned operation. Capable of reducing machining time and improving the quality of machined surfaces.  More roughing allowance can be taken by using a flat end mill in place of a conventional bowl end mill Adapted from: http://www.mitsuiseiki.co.jp/en/machine/vertex/02.html

22. 5-axis Machining Adapted from: http://www.mitsuiseiki.co.jp/en/machine/vertex/02.html