MANUFACTURING PROCESSES

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1 MANUFACTURING PROCESSES - AMEM 201 Lecture 7: CNC MACHINE TOOLS 1 CNC MACHINE TOOLS TERMINOLOGY NC Numerical Control CNC Computer Numerical Control CAD Computer Aided Design CAM Computer Aided Manufacturing 2 1

2 Numerical Control - Definition A form of programmable automation in which the mechanical actions of a machine are controlled by a program containing coded alphanumeric data 3 NC OPERATING PRINCIPLE NC operating principle is to control the motion of the tool relative to the workpart - In an ordered sequence of motions - Following a predetermined path - Respecting the required dimensions - At a specific feed and spindle speed rate This is achieved through a group of alphanumeric instructions (coded program) 4 2

PROGRAMMING & OPERATION OF A CNC MACHINE NUMERICAL DATA (CODED PROGRAM)

PART CNC MACHINE 5 CNC Machine Tools - Types NC widely used for machining operations

centers, which change their own cutting tools to perform a variety of machining

3 PROGRAMMING & OPERATION OF A CNC MACHINE NUMERICAL DATA (CODED PROGRAM) MANUFACTURING OPERATOR NUMERICAL CONTROLLER Drive Control PROCESSED PART PROCESSED PART CNC MACHINE 5 CNC Machine Tools - Types NC widely used for machining operations such as turning, drilling, and milling NC has motivated development of machining centers, which change their own cutting tools to perform a variety of machining operations Other NC machine tools: Grinding machines, Sheet metal pressworking machines, Bending machines 6 3

4 CNC Machine Tools CNC Machining center 7 CNC Machine Tools Turning center 8 4

CNC Machine Tools Drilling Tapping center 9 Advantages of CNC Machines Increased machining accuracy Do production jobs that are impossible without CNC

5 CNC Machine Tools Drilling Tapping center 9 Advantages of CNC Machines Increased machining accuracy Do production jobs that are impossible without CNC Greater manufacturing flexibility Reduced human error Reduced actual machining time Less setup time Make production jobs easier Increased production 10 5

6 Limitations of CNC Machines o High initial investment Machine tools cost $30,000 - $1,500,000 o High maintenance requirements Maintenance personnel must have both mechanical and electronics expertise o Not cost-effective for low-level production on simple parts As geometric complexity or volume increases CNC becomes more economical 11 CNC Application fields o Aerospace o Machinery o Fabrication o Automotive o Instrumentation o Mold making 12 6

7 BASIC CNC CONCEPTS 1. AXES AND DIRECTIONS OF MOTIONS 2. REFERENCE POINTS - MACHINE ZERO POINT - WORKPIECE ZERO POINT 3. ABSOLUTE & INCREMENTAL COORDINATES Directions of motion on a 3-axis milling machine 7

8 Positive Directions of axes for a milling machine Axes of motion for a milling machine 8

surfaces for machining 17 NC Positioning System Motor and leadscrew arrangement in a NC positioning system.

9 NC Coordinate System Consists of three linear axes (X, Y, Z) of Cartesian coordinate system, plus three rotational axes (a, b, c) Rotational axes are used to orient workpart or workhead to access different surfaces for machining 17 NC Positioning System Motor and leadscrew arrangement in a NC positioning system. Converts the coordinates specified in the coded program into relative positions and velocities between tool and workpart 18 9

10 2. Reference Points of the milling machine Machine Zero Point Machine Zero Point is a fix position set by Machine Tool Builder. It is the reference of the Machine 2. Reference Points of the milling machine Workpiece Zero Point Workpiece Zero Point can be anywhere and is set by the user before the machining process start. 10

11 Setting Workpiece Zero Point Setting Workpiece Zero Point 11

12 Workpiece Zero Point can be compared to the Origin of Rectangular Coordinate System 3. ABSOLUTE VS. INCREMENTAL POSITIONING Absolute Mode Tool locations are always defined with respect to origin of axis system Incremental Mode Next tool location is defined relative to present location 24 12

13 3. Absolute vs. Incremental Positioning EXAMPLE The tool is presently at point (100,30) and is to be moved to point (40,70). In absolute positioning, the move is specified by X = 40, Y = 70. In incremental positioning, the move is specified by X = - 60, Y = Absolute vs. Incremental Positioning EXERCISE MOTION ABSOLUTE INCREMENTAL 0 1 Χ30 Υ20 Χ30 Υ Χ50 Υ100 Χ20 Υ Χ70 Υ60 Χ20 Υ Χ90 Υ60 Χ20 Υ0 4 5 Χ100 Υ80 Χ10 Υ Χ140 Υ120 Χ40 Υ Χ140 Υ20 Χ0 Υ Χ80 Υ20 Χ-60 Υ

14 CNC Programming Techniques 1. Manual programming 2. CAD/CAM programming Manual Programming Uses basic numerical data and special alphanumeric codes to define the steps in the process Suited to simple machining jobs such as simple profile cuttings and drilling 28 14

CNC or Part Program Example command for linear motion: N10 G90 G01 X70 Y85 F300 S2000 where, N10 - A sequence number; G90 - Abslolute Mode G01 - Linear motion X and Y -

15 CNC or Part Program Example command for linear motion: N10 G90 G01 X70 Y85 F300 S2000 where, N10 - A sequence number; G90 - Abslolute Mode G01 - Linear motion X and Y - Coordinate positions (mm) F - Feed rate (300 mm/min) S - spindle speed (2000 rev/min) 29 CNC or Part Program Complete part program consists of a sequence of commands 30 15

16 Basic Codes for CNC Programming CODE G M N MEANING Gxx G code Mxx M code Command sequence number F Feedrate (mm/min) S Spindle speed (RPM) T Tool number X, Y, Z Coordinates (mm) R Radius (mm) Commonly used G and M codes G CODE MEANING M CODE MEANING G90 Absolute Mode M03 Spindle ON - CW G91 Incremental Mode M06 T Tool Change G20 Units in inches M08 Coolant ON G21 Units in mm M09 Coolant OFF G00 Linear Motion - Rapid M30 Program End G01 G02 G03 Linear Motion - Feedrate Circular Motion CW Circular Motion CCW 16

17 TOOL T1 S (rpm) F (mm/min) APPLICATION EXAMPLE - 1 Depth End mill Ø mm N10 G21 ABSOLUTE PROGRAM 1 N20 M06 T1 N30 M03 S2000 N40 G90 G00 X25 Y25 Z N50 G01 Z-4 F300 N60 G01 X25 Y75 N70 G01 X65 Y125 N80 G01 X125 Y125 N90 G01 X125 Y65 N100 G03 X85 Y25 R40 N110 G01 X25 Y25 N120 G00 Z30 N130 M30 33 TOOL T1 S (rpm) F (mm/min) APPLICATION EXAMPLE - 1 Depth End mill Ø mm INCREMENTAL PROGRAM 1 N10 G21 N20 M06 T1 N30 M03 S2000 N40 G90 G00 X25 Y25 Z N50 G01 Z-4 F300 N60 G91 G01 X0 Y50 N70 G01 X40 Y50 N80 G01 X60 Y0 N90 G01 X0 Y-60 N100 G03 X-40 Y-40 R40 N110 G01 X-60 Y0 N120 G00 Z30 N130 M

18 TOOL T1 S (rpm) F (mm/min) APPLICATION EXAMPLE - 2 Depth End mill Ø mm ABSOLUTE PROGRAM 2 N10 G21 N20 M06 T1 N30 M03 S2000 N40 G90 G00 X25 Y25 Z2 N50 G01 Z-4 F300 N60 G01 X25 Y55 N70 G03 X25 Y95 R20 N80 G01 X25 Y125 N90 G01 X45 Y125 N100 G03 X105 Y125 R30 N110 G01 X125 Y125 N120 G01 X125 Y95 N130 G03 X125 Y55 R20 35 TOOL T1 S (rpm) F (mm/min) APPLICATION EXAMPLE - 2 Depth End mill Ø mm ABSOLUTE N140 G01 X125 Y25 N150 G01 X105 Y25 N160 G03 X45 Y25 R30 N170 G01 X25 Y25 N180 G00 Z

19 TOOL T1 S (rpm) F (mm/min) APPLICATION EXAMPLE - 2 Depth End mill Ø mm INCREMENTAL PROGRAM 2 N10 G21 N20 M06 T1 N30 M03 S2000 N40 G90 G00 X25 Y25 Z2 N50 G01 Z-4 F300 N60 G91 G01 X0 Y30 N70 G03 X0 Y40 R20 N80 G01 X0 Y30 N90 G01 X20 Y0 N100 G03 X60 Y0 R30 N110 G01 X20 Y0 N120 G01 X0 Y-30 N130 G03 X0 Y-40 R20 37 TOOL T1 S (rpm) F (mm/min) APPLICATION EXAMPLE - 2 Depth End mill Ø mm INCREMENTAL N140 G01 X0 Y-30 N150 G01 X-20 Y0 N160 G03 X-60 Y0 R30 N170 G01 X-20 Y0 N180 G00 Z

20 2. CAD/CAM PROGRAMMING 39 CAD/CAM CAD systems are used to define part geometries CAM systems are used to create cutter paths that can be used by the machine tool

21 The structure of a CAD/CAM System CAD Creates part geometry CAM CAD FILE -Machining method -Shape to machine -Order of operations -Cutting tools -Cutting path & conditions CNC FILE 21

Manufacturing Processes with the Aid of CAD/CAM Systems AMEM 405

AMEM 405 slide 1 Manufacturing Processes with the Aid of CAD/CAM Systems AMEM 405 Dr. Sotiris Omirou AMEM 405 slide 2 CONTENTS 1. CAD/CAM definition 2. Review of Milling Process 3. Know The CNC Machine