# CNC Programming “Milling”

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CNC Programming “Milling”
12 April 2017 CNC Programming “Milling” Module Objectives: 1) To use Topmill 2) To create NC programs for different milling operations IAT - DXB 2008

Milling Machine

G-Codes G00, G01, G02, G03, G04, G54, G90, G91, G94 and G95 Are the same as explained in module 4. New important G codes: Function Description G17,G18, and G19 Working plane selection G40 Cutter radius compensation OFF. G41 Cutter radius compensation ON Left. G42 Cutter radius compensation ON Right. G70 Input system inch G71 Input system metric

G-Codes The following G-Codes and their relative slides will be used as a reference when solving some practical tasks in this module. Function Description G111 Polar coordinate interpolation G147 Approach with a straight line. G148 Leave in a straight line. G247 Approach with a quarter a circle. G248 Leave with a quarter a circle.

G17, G18, and G19 Used to select the working plane G17 XY Plane
G18 ZX Plane G19 YZ Plane The tool axis is vertical to the working plane

What Is The Correct G-code To Select The Top Surface Of The Workpiece As a Working Plane ?

G41, G42 and G40 With G41 / G42 the tool traverse at equal distances to the programmed contour along its path. This distance is the dimension of the radius of the cutter. If the cutter is left to the contour this is programmed by G41 (This called cutter radius compensation left).

G41, G42 and G40 If the cutter is right to the contour this is programmed by G42. (This called cutter radius compensation right) To cancel the radius compensation use G40

G70 / G71 G70: The controller of the CNC milling machine reads the input values in imperial system (Inch) G71: The controller of the CNC milling machine reads the input values in metric system (mm)

G111 If we want to use polar coordinate system to move the tool, we need first to locate the pole (zero point of the polar coordinate system) measured from original workpiece zero point, this is done by G111. Then write the required movement in polar system by specifying the Angle (AP) and the radius (RP). Example: G111 X30 Y40 Z0 G01 RP=40 AP=60 F300

G147, G148, G247 and G248 Soft approach and leaving commands.
The function of soft approach and leaving serves to approach the starting point of a contour tangentially irrespective of the position of the initial point. The function is mainly used in connection with the tool radius correction; however, it is not obligatory.

G147, G148, G247 and G248 G147 Approach with straight line
G148 Leave in straight line. G247 Approach with a quarter a circle G248 Leave in a quarter a circle

Cycles Cycle Description Cycle 81
Drilling; to make a hole in one phase. Cycle 83 Deep Drilling; to make a deep hole, which requires introducing the tool with several phases. (Chip-breaking and chip removal). Pocket To engrave a circular or a rectangular area on a surface. Holes To repeat a drilling operation following circular or linear contours.

Cycle 81 – Drilling Cycle To make a hole in one phase

Cycle 81

Cycle 81 To make a hole in one phase Example: Make a hole at
point X20 Y20 to a depth = 10mm

Cycle 81 Solution: Cycle Parameters: G54 S1500 M3 F120
G00 X20 Y20 Z2 Cycle 81 (2,0,1,-10,0) G0 Z40 M30 Cycle Parameters: Return plane absolute 2 Reference plane absolute 0 Safety distance 1 Final drilling depth -10 Depth incremental 0

Cycle 83 Deep Drilling Cycle

Cycle 83

Cycle 83 Cycle 83 (2,2,,-86,,,35,4,1,1,1,1)

Holes 1 To make a row of holes

Holes 1

Holes 1 - Example

Holes 2 To make a circle of holes

Holes 2

Holes 2 - Example

Pocket – (Pocket1/Pocket2)

Pocket 1

Pocket 1 - Example

Pocket 2

Pocket 2 - Example

Example of CNC Programming
12 April 2017 Example of CNC Programming What Must Be Done To Drill A Hole On A CNC Vertical Milling Machine? Given That: Absolute Positioning Mode, Cutting Tool No. 1, Spindle Speed 1000 RPM, Clockwise Direction Of Rotation At Feed Rate 200 mm/min . Hole Position X10, Y12, And Depth Of Hole 10 mm. An example of creating a CNC program using a simple hole drilled on a computer numerical controlled (CNC) vertical milling machine. IAT - DXB 2008

Solution NC-Program %Mill_1 N005 G54 N010 G90 N015 G97 S1000 M03
N020 T1 D1 M6 N025 ………………… N030 …………………

N025 G00 X10 Y12 Z10 Rapid To Hole Position (Above The Hole) Tool Home
12 April 2017 N025 G00 X10 Y12 Z10 Rapid To Hole Position (Above The Hole) Tool Home Top View Front View In this case, we are using a simple analogy to stress how a programmer must be able to visualize a CNC program’s execution. We first look at how a machinist would machine a hole in a work piece held in a vise on a milling machine. Then we’ll show how the same operation will be performed with a CNC program. The machinist standing in front of the milling machine has everything they need right in front of them. They wouldn’t forget something as simple as turning the spindle on before trying to drill the hole. On the other hand, a CNC programmer must typically work with nothing more than a blueprint, a pencil, a calculator, and a blank piece of paper. They must be able to visualize every motion and function of the program’s execution in their minds. IAT - DXB 2008

Z Axis Feed To Drill The Hole
12 April 2017 N030 G01 Z-10 F200 Z Axis Feed To Drill The Hole Top View Front View IAT - DXB 2008

Rapid Movement In Z Axis Out Of Hole
12 April 2017 N035 G00 Z6 Rapid Movement In Z Axis Out Of Hole Top View Front View IAT - DXB 2008

The NC-Program %Mill_1 N005 G54 N010 G90 N015 G97 S1000 M03
N020 T1 D1 M6 N025 G00 X10 Y12 Z10 N030 G01 Z-10 F200 N035 G00 Z6 N040 M05 N045 G00 X100 Y100 Z100 N050 M30