395121986-300120529-An-introduction-to-CNC-Machines-PPT-pptx.pptx

CNC machines

1. Introduction to Computer Numerically Controlled(CNC) Machines and its Advantages Submitted by: Bulon Ch. Hazarika Scholar no: 15-22-308 Cad cam and automation Submitted to: Mr . Pannalal Choudhury Associate Professor

2. Introduction : Computer Numerical Control (CNC) Machine Computer Numerical Control (CNC) machine is one in which the functions and motions of a machine tool are controlled by means mini or microcomputer. All the cutting processes that are to be carried out and all the final dimensions are fed into the computer via the program. The computer thus knows what exactly is to be done and carries out all the cutting processes. CNC machine works like the Robot, which has to be fed with the program and it follows all your instructions. The computer translated the program into the appropriate electrical signals for input to motors that run the machine. . NIT SILCHAR,ASSAM

3. History: 1955 - John Parsons and US Air Force define a need to develop a machine tool capable of machining complex and close tolerance aircraft parts with the same quality time after time ( repeatability).Which led to the introduction Numerical Control(NC) machines which was controlled and operate using a punched tape. Standardization of G codes in the early 60’s. 1960 - Direct Numerical Control (DNC). This eliminates paper tape punch programs and allows programmers to send files directly to machine tools. 1980’s - Graphics based CAD/CAM systems introduced. Modern NC machine has a computer on board , Computer Numerical Control (CNC) . They can run unattended at over 20,000 r.p.m (spindle speed) with a feed rate of over 600 i.p.m and an accuracy of .0001 NIT SILCHAR,ASSAM

4. Some of common type of CNC machines: CNC Lathe Machine CNC Milling Machine CNC Drilling Machine CNC Grinding Machine CNC Laser Cutter 3D Printer Example of CNC Milling Machine NIT SILCHAR,ASSAM

5. Examples of CNC Machines: CNC Milling Machine HAAS CNC Turning Machine HAAS NIT SILCHAR,ASSAM

6. Salient Features of CNC Machinery M achine Control Unit (MCU) is a microcomputer where we give the program or commands and executes the commands into actions by the machine tool. Display Unit displays all the necessary information such as the spindle speed , tool position, depth of cut etc. Input Device through which can enter programs directly and run them to perform the given operation. Tools can operate in 1-5 axes thus making it easier to machine complex geometrical shapes. Movement is controlled by motors (actuators) which provide precise motion of the tool and the table in the required direction. Feedback is provided by sensors (transducers) which provides the precise data of the position of the tool and the work piece. Tool magazines can hold a large number of tools are used to change tools automatically. A CNC machine can work automatically for hours without any supervision. NIT SILCHAR,ASSAM

7. Basic Elements of CNC machine a. Input Device b. Machine Control Unit c. Machine Tool d. Driving System e. Feedback Devices f. Display Unit Example of a Display Unit NIT SILCHAR,ASSAM

8. Working principles of a CNC Machines Block Diagram NIT SILCHAR,ASSAM

9. Basic CNC Axis of Motion Standard Milling Coordinate system NIT SILCHAR,ASSAM

10. Three Basic Categories of Motion Systems in CNC Point to Point - No contouring capability Straight cut control - one axis motion at a time is controlled for machining Contouring - multiple axis’s controlled simultaneously NIT SILCHAR,ASSAM

11. How CNC machine performs an operation on the work piece? To perform an operation we have to write a Part Program which can be prepared manually(generally for small programs) or automatically prepared(for complex geometrical shapes) with the help of software packages . NIT SILCHAR,ASSAM

12. What is a P art Program ? The numerical data required to produce a part is provided to a machine in the form of a program, called P art program or CNC program . The program need to specify : - Which tool should be loaded on the machine spindle? - What are the cutting conditions (speed, feed, coolant ON/OFF etc.)? - What is the start point and end point of a motion segment? - How to move the tool with respect to a work piece in a machine? NIT SILCHAR,ASSAM

13. How to write a program? To write of program which will perform the required operations we need to provide the relevant numerical data in the form of various codes. (Each line of program == 1 block ) Preparatory Codes (G ) for initial machining setup and operating conditions. Miscellaneous Codes ( M) for on/off of coolant flow, spindle rotation etc . Spindle Speed (S) Feed Rate (F) Tool number (T) Basic codes and terms used a re: NIT SILCHAR,ASSAM

14. N100 G91 X -5.0 Y7.0 Z4.0 F100 S200 T01 M03 (EOB) sequence no preparatory function destination coordinates feed rate spindle speed miscellaneous function Tool number Example of a typical Block or Line for a program: NIT SILCHAR,ASSAM

15. Programming Example ( Cylindrical Part) O0013 N0005 G53 N0010 T0303 N0020 G57 G00 X26.00 Z0.0 S500 M04 N0030 G01 X-0.20 F100 N0040 G00 Z2.0 N0050 X50.0 Z50.0 N0060 T0404 N0070 G57 G00 X22.50 Z2.0 S500 N0080 G01 Z-30.0 F100 N0090 G00 X23.0 Z2.0 S500 N0100 G84 X17.5 Z-20.0 D0=200 D2=200 D3=650 N0110 G00 Z2.0 N0120 X50.0 Z50.0 N0130 M30 Raw Material Finished Part NIT SILCHAR,ASSAM

16. Some application of CNC machines : C utting Drilling Milling W elding B oring B ending S ewing ongoing Laser Cutting in a CNC machine NIT SILCHAR,ASSAM

17. Applications of CNC machines in some industries and institutions: Automotive Industry Aerospace Industry Machinery Industry Electrical Industry Instrumentation Industry Medical Institutions Educational Institutions CNC machines in a Automotive Industry NIT SILCHAR,ASSAM

18. Advantages of CNC:  CNC machines can be used continuously 24 hours a day, 365 days a year and only need to be switched off for occasional maintenance Flexibility in operations is improved, as it has the ability to produce complex shapes with good dimensional accuracy; Repeatability; Reduced scrap loss: Easier to program; - Easy store, edit and change existing programs ; Stabilize manufacturing costs; - Avoids human errors; - Safer to operate; - Usually generates closer tolerances than manual machines high production rates NIT SILCHAR,ASSAM

19. Summary CNC machines allow precise and repeatable control in machining CNC lathes, Milling machines, etc. are all controlled by NC programs NC programs can be generated manually, automatically NIT SILCHAR,ASSAM

20. NIT SILCHAR,ASSAM REFERENCES:     Mickell P. Groover & Emory W. Zimmers , Jr “Computer Aided Design and Manufacturing”   P.N Rao “CAD/CAM Principles and Applications”   INDUSTRIAL CENTRE, THE HONGKONG POLYTECHNIC UNIVERSITY “Computer Numerical Control (CNC)”   P.Radhakrishnan , S Subramanyan & V.Raju “ CAD/CAM/CIM”