1. CNC CONTROL SYSTEM AND PART PROGRAMMING
UNIT-III
CNC CONTROL SYSTEM AND PART PROGRAMMING
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2. C.SOMU Asst prof Sns tech
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3. Overview of presentation
CNC control system- An overview
Open loop and closed loop control system system
Feedback subsystem in CNC
Feedback for CNC
Block diagram for CNC
CNC interpolation
Hardware and software interpolation
Features of CNC
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4. CADCAMCIM SNSCT
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5. CADCAMCIM SNSCT
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6. Pneumatic systems
Pneumatic technology deals with the study of behavior and applications of compressed air in our daily life in general and manufacturing automation in particular.
Pneumatic systems use air as the medium which is abundantly available and can be exhausted into the atmosphere after completion of the assigned task.
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7. Components of a pneumatic system
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8. Case study A soucre:http://nptel.ac.in/courses/112103174/34
 Consider a simple operation where a double-acting cylinder is used to transfer parts from a magazine. The cylinder is to be advanced either by operating a push button or by a foot pedal. Once the cylinder is fully advanced, it is to be retracted to its initial position. A 3/2-way roller lever valve is to be used to detect the full extension of the cylinder. Design a pneumatic circuit for the above-mentioned application.
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9. Fig. 6.6.1 Pneumatic circuit for shuttle valve operation
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10. double acting cylinder 3/2 push button valve 3/2 roller valve
The pneumatic components which can be used to implement the mentioned task are as follows:
double acting cylinder
3/2 push button valve
3/2 roller valve
shuttle valve
3/2 foot pedal actuated valve
5/3 pneumatic actuated direction control valve
compressed air source and connecting piping
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11. Figure 6. 6. 1 shows the proposed circuit diagram
Figure shows the proposed circuit diagram. As the problem stated, upon actuation of either the push button of valve (S1) or the foot pedal valve (S2), a signal is generated at 1 or 1(3) side of the shuttle valve. The OR condition is met and the signal is passed to the control port 14 of the direction control valve (V2). Due to this signal, the left position of V2 is actuated and the flow of air starts. Pressure is applied on the piston side of the cylinder (A) and the cylinder extends. If the push button or pedal valve is released, the signal at the direction control valve (V2) port is reset. Since DCV (V2) is a double pilot valve, it has a memory function which doesn't allow switching of positions. As the piston reaches the rod end position, the roller valve (S3) is actuated and a signal is applied to port 12 of the DCV (V2). This causes actuation of right side of DCV (V2). Due to this actuation, the flow enters at the rod-end side of the cylinder, which pushes the piston towards left and thus the cylinder retracts.
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12. Hydraulic System In CNC Machine
1. Tool clamp/declamp operation : 2. Pallet clamp/declamp operation : 3. Hydro-motor for arm rotation or turret rotation 4. Hydraulic hammer for hot and cold swagging 5. Rotational axis clamp/declamp :
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14. Hydraulic system is nothing but a system operated by hydraulic oil
Hydraulic system is nothing but a system operated by hydraulic oil. When there is a need of much pressure in low volumetric area, Hydraulic system gives us the solution.
CNC machine is such type of machine where several jobs are executed in compact area and in less time. In such scenario, hydraulic systems play a big role to execute several functions.
Hydraulic Pressure in CNC machine is developed by hydraulic power pack which is a combination of several hydraulic components.
Hydraulic circuit is a close circuit. A hydraulic pump is incorporated to raise the pressure up to desired system pressure and that system pressure is distributed to various work places through solenoid valves and regulated through hydraulic pressure regulators.
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15. Open loop and closed loop control system
CNC systems require motor drives to control both the position and the velocity of the machine axes. Each axis must be driven separately and follow the command signal generated by the NC control. There are two ways to activate the servo drives: the open-loop system and the closed-loop system.
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17. Closed loop control system
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18. Open Loop vs. Closed Loop controls
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19. Open loop control of a Point-to-Point NC drilling machine
NOTE: this machine uses stepper motor control
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20. Two types of encoder configurations
Components of Servo-motor controlled CNC
Motor
lead screw rotation
table moves
Motor speed control
feedback
position sensed by encoder
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Two types of encoder configurations
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