CNC Machine Control Unit

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Servo Drive

Control

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Hydraulic Servo Drive

Hydraulic power supply unit Hydraulic power supply unit Servo valve

Servo amplifiers

Se o a p e s

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Hydraulic Servo Valve

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Hydraulic Servo Drive



Hydraulic cylinders: linear motion



Hydraulic cylinders: linear motion

A drastic increase of fluid volume in the

cylinder causes the system dynamic

response to become sluggish due to bulk

modulus effect



Hydraulic motors: rotary motion



Hydraulic motors: rotary motion

The motor is operated at higher speed and is

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d

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Permanent Magnet Stepping Motor

Low velocity : 500 rpm with 500 pulses/sec Low velocity : 500 rpm with 500 pulses/sec

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Mode of Operation

Single Step Mode 5 steps/sec

Slue Mode

Continuous Motion 5 steps/sec

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Three Phase Variable Reluctance Stepping

M t

Motor

It uses a toothed iron wheel such that it can be made in any shape However it gives less torque than the PM any shape. However, it gives less torque than the PM motor

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Brushed DC Servo Motor

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Brushed DC Servo Motor

The motor has four main components: permanent The motor has four main components: permanent magnets in the stator, armature windings in the rotor, brushes, and a commutator.

 sin      K I T_m K_e  I_a sin T

where Tm is the motor torque, Ke is the motor constant,  is

the magnetic flux density, Ia is the armature current,  is the

angle between magnetic field vector and current vector A angle between magnetic field vector and current vector. A typical DC servo motor circuit can be described by the following equation.   dI          dt dI L I R K V_a _b _a _a _a a

The torque equation is

  ( ) ) ( _m _l _m _l m J J f f T     

Advantages: inexpensive easy to be controlled Advantages: inexpensive, easy to be controlled.

Disadvantage: brush replacement, electrical noise, poor thermal dissipation, high rotor inertia.

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Brushless DC Servo Motor

The windings of a brushless motor are located in the stator and the permanent magnets are mounted on the stator, and the permanent magnets are mounted on the armature. Two commonly used electronic commutation schemes are the optical disk and Hall effect method

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FanucTaiwan com

FanucTaiwan.com

http://www.fanuctaiwan.com.tw/index00.asp

htt // f j /j /d l t/l b t ht l

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FANUC 控制器 18i-MB

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Control Loop

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Contouring Accuracy

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Parameter setting

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Controller Auto-tuning

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Machine Axes and Coordinate Systems

The positioning of a workpiece on a CNC machine

axis identification

coordinate systems

positioning systems

machine coordinates

work coordinates

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Machine Axis Identification

Axis: a line segment used to orient a space or a geometric

Machine Axis Identification

g p g

object.It can be regarded as a reference line from which distances or angles are measured in a coordinate system. g y The Cartesian coordinate system is normally used to define the movements on CNC machines.e o e e s o C C ac es

Two types of axis Two types of axis movement: linear and rotary motion. and rotary motion.

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Z axis Z axis

The z-axis is always coincident with or parallel to the axial centre line of the main machine rotating spindle. +Z: the direction in which the tool moves away from the workpiece.

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X axis

The axis parallel to the longest dimension of the primary machine table.

X X t i t th i ht h i d f th

+X: +X movement is to the right when viewed from the spindle axis with the observer facing the supporting column (for vertical Z-axis)

column (for vertical Z axis).

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+X movement is to the right when viewed from the

when viewed from the

spindle axis in the direction of workpiece (for horizontal

View dir. of workpiece (for horizontal

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Relationship between table

Moving the cutter to the right (+X) in relation to

motion and cutter motion

Moving the cutter to the right (+X) in relation to the table requires moving the table to the left (-X) To avoid confusion a part programmer can X). To avoid confusion, a part programmer can always consider the motion in terms of the cutter moving along the part, regardless of whether it is the cutter or moves.

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Primary Rotary Axes: A, B and C

A, B and C are used to indicate rotary motions about the X, Y and Z axes, respectively. The thumb rule is used to determine the direction of rotation. Many y CNC machining centers are characterized by three linear axes and one rotary axisy

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Coordinate Systems

In CNC applications two coordinate systems can be

Coordinate Systems

In CNC applications, two coordinate systems can be used to identify the critical points that define a

workpiece: the Cartesian coordinate system and the workpiece: the Cartesian coordinate system and the polar coordinate system.

Cartesian coordinate system: In single quadrant

positioning, preferred by many part programmers, all position are located in the 1st quadrant.

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Polar coordinate system: The angle is positive when measured in the

counterclockwise direction from the positive X axis.

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The use of polar rotation to drill a series of holes along a circle

Coordinate system rotation and machining of Coordinate system rotation and machining of symmetrical part feature using polar rotation

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Positioning System

Absolute positioning system

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Reference coordinate

Machine reference point:

Initial setup of the machine

As the reference point for other coordinate system As the tool change position

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Reference return point: accurately predetermined in each moving axis by limit switch to allow the machine table or spindle to be returned to.

Work reference points: (G92) The origins of the workpiece coordinate systemsp y

Program reference points: (G92) These positions are chosen by the programmer to locate all other points in the part program