Smart Design of five axis Computer Numerical Control machine for Industrial applications

Project Title

Smart Design of five axis Computer Numerical Control machine for Industrial applications

Project Area of Specialization Mechatronics EngineeringProject Summary

To manufacture parts of mechanical assemblies, manual machining is a common practice in Pakistan while the world has moved towards Computer Numerically Controlled (CNC) machining. The project aims the indigenous and smart design and development of a 5-axis CNC machine for the manufacturing of parts of different industrial assemblies as import substitute. CNC machines are mechatronic devices that, with advanced control systems and programming, can manipulate tools around a number of axes to generate a physical part from a computer-aided design (CAD) using subtractive manufacturing process i.e. removing the material from stock using cutting tools. Number of axes is basically the degrees of freedom of the machine. A 5-axis machine refers to the movement of the tool along three conventional (x, y and z) axes with two additional rotational axes (A and C) which allows it to manufacture more complex designs for variety of industrial applications. The positions and movements of the tools are based on geometric code (G-code) which is obtained by computer-aided manufacturing (CAM) using any CAD and CAM software. The computer interfacing with the hardware and inverse kinematics makes it possible for the motors of the CNC to do the actuation according to the G-code.

Project Objectives

Aims and objectives

• To manufacture parts/ models of any sort of mechanical assembly from computer-aided designs (CAD) using simultaneous five axes motion.

• To make the machine capable of delivering high machining accuracy so that the manufactured parts have perfectly desired dimensions.

• To manufacture complex designs efficiently in less machining time as the simultaneous five axes movement will allow to machine complex shapes in a single set-up without the hassle changing the orientation of the stock again and again for a series of set-ups.

• To use the CNC for engraving words or logos on metal or wood and for engraving circuitry tracks of copper sheets for manufacturing of printed circuit boards (PCBs).

• To make the CNC machine smart by wireless interfacing of the computer system with the machine.

• To make the CNC machine secure by using biometric verification or voice recognition system in order to avoid its misuse so that only authorized persons will be able to use the CNC machine.

Project Implementation Method

The methodology of our projects is to start with the designing and performing simulations of mechanical assembly of CNC machine which is necessary before going on the hardware phase. Using the results of simulations and design with accurate dimensions, the project is to be implemented on the hardware and assembled. CNC would then be interfaced with a computer system in order to perform fully automated tasks and move the tool with respect to the G-code, which has been obtained via CAM for cutting and drilling. G-code is a series of lines which contains the coordinates of locations providing a path for machine tools to follow. Using Inverse Kinematics Analysis and solving kinematic equations, software will perform actuation of motors of the respective axes in order to reach those locations and follow the provided path for subtractive manufacturing.

Benefits of the Project

• The fundamental scope of the project is to save the cost of import and customs duty as there is no production of even 3-axis CNC machines in Pakistan, let alone 5-axis. Our project is initially an import substitute but it can be a gateway towards the production of CNC machines completely in Pakistan.

• Manual machining consumes more time, accuracy of dimensions is compromised and the machinist has to operate the milling machine by moving the axes manually during the whole process of manufacturing. CNC milling machine will provide high machining accuracy and will model complex designs is less manufacturing time. 

• 5-axis CNC machines are important in a number of ways for manufacturing of a wide range of model whose geometries are typically defined by complex surfaces.

• Simultaneous five axes motion will allow the end effector (machine tool) to reach maximum locations of the stock/ work piece in order to avoid the hassle of changing the orientation of the stock again and again, which will eventually increase the productivity of manufacturing and decrease the workload of the machinist.

• Security verification before the use of CNC machine will avoid the misuse of the machine as the milling machine can be used to manufacture illicit weapons and ammunition, which might prove detrimental to national security. Only the authorized person will be able to access the CNC milling machine.

Technical Details of Final Deliverable

The parts of mechanical assembly of CNC are fabricated by Aluminum alloy sheet metal which were designed and simulated on SolidWorks software with acurate dimensions. Electric actuation for subtractive manufacturing is performed by driving motors with rotational-linear movement mechanism. The end effector performs translational motion along X, Y and Z by changing the rotational movement of the driving motor into linear movement. The motor shafts are connected to the ball screws with couplers. Ball screws of C5 accuracy grade rotate and the ball screw nut moves linearly with a linear movement guide, which increases smoothness.

C-axis table’s shaft is coupled with a pulley of larger diameter and the driving motor shaft is coupled with another pulley of smaller diameter. A Timing belt is used to transmit power from the motor shaft to the C-axis table's shaft with amplified torque. A-axis is directly connected with the A-axis driving motor shaft which tilts the rotary table clockwise and counter-clockwise direction. Table below shows the specifications of the mechanical assembly of our design.

The rotary table is going to carry the workpiece (stock) in our design for rotation about C and A axes, parallel to the Z and X axes respectively. Stepper motors are being used for the axes movements as they are comparatively economical and provide high holding torque. In order to achieve the correct selection of motor size, simulations have been performed with a maximum stock size of (200 × 165 × 120) mm of 6061-T6 Aluminum alloy, which weighs 10.7 kg. With the help of obtained results, stepper motors are selected for the linear movements along the X, Y and Z axes and rotational movements about the A and C axes.

Axes	Stepper Motors	Motor Drivers
X	Nema 23 (2 Nm, 2.8 Amp)	TB6600
Y	Nema 23 (2 Nm, 2.8 Amp) x2	TB6600
Z	Nema 23 (3 Nm, 4.2 Amp)	DM556
Rotary axis A	Nema 34 (4.5 Nm, 6 Amp)	DM860
Rotary axis C	Nema 34 (7.2 Nm, 6 Amp)	DM860

The hardware is interfaced with computer system using Raspberry Pi with Mesa 7c81 FPGA card, which is connected with the motor drivers to parse signals in to rotate motors in such a way that the end effector follows the toolpaths. LinuxCNC software implements numerical control capability by inverse kinematics and controls CNC systems.

AxesX                    500 mmY                    600 mmZ                    300 mmRotary axis A        90° CW and 20° CCWRotary axis C     360° CW and 360° CCWAxesXNema 23 (2 Nm, 2.8 Amp)YNema 23 (2 Nm, 2.8 Amp) x2ZNema 23 (3 Nm, 4.2 Amp)Rotary axis ANema 34 (4.5 Nm, 6 Amp)Rotary axis CNema 34 (7.2 Nm, 6 Amp)Final Deliverable of the Project Hardware SystemCore Industry ManufacturingOther IndustriesCore Technology RoboticsOther TechnologiesSustainable Development Goals Industry, Innovation and InfrastructureRequired Resources

Axes	Stepper Motors	Motor Drivers
X	Nema 23 (2 Nm, 2.8 Amp)	TB6600
Y	Nema 23 (2 Nm, 2.8 Amp) x2	TB6600
Z	Nema 23 (3 Nm, 4.2 Amp)	DM556
Rotary axis A	Nema 34 (4.5 Nm, 6 Amp)	DM860
Rotary axis C	Nema 34 (7.2 Nm, 6 Amp)	DM860