现代数控机床原理与结构

现代数控机床原理与结构（双语） ppt 课件
Thinking…
Identify primary motions and feeding motions.
Milling
Planing
Broaching
现代数控机床原理与结构（双语） ppt 课件
2.1.3 Assistant motions
All motions other than surface forming motions, including plunge motion, indexing motion, alignment motion, fast moving, and other actions. 1) Plunge motion
Descartes (1596-1690) French philosopher, mathematician
Cartesian coordinate (Right hand rules)
2. Directions of axes (1) All axes assume that tools move while worktables rest;
Gear ratio2 (internal relation)
Lead screw
2.2.4 Transmission system diagramபைடு நூலகம் XKA5750 milling machine
2.3 Coordinate system for NC machine tools
2.3.1 Standard coordinate system and direction 1. ISO coordinate system
Plunge cutting tool into workpiece to obtain a certain dimension 2) Indexing motion Periodical moving, rotating of worktable or tool post to machining each surfaces of workpiece, e.g. multi-thread screws turning, polygon machining, etc.
Screw turning requires stringent transmission ratio between spindle rotation and tool post moving to ensure precise thread pitch.
2.2.3 Transmission diagram
2.2 Machine tool drive
To realize those necessary motions for machining, each NC machine tool should have three basic units:
(1) Actuators, e.g. spindle, tool post, worktable, etc.
Constant ratio
Transmission diagram of screw turning
Motor
From NC machine tools, spindle and tool post may be driven by their own motors.
Gear ratio1 (external relation) Spindle Thread Cutting tool
Transmission diagram briefly represents relative motion paths of surface forming.
Motor
Spindle
Cutting tool
Hob（滚刀）
Combined unit
Variable ratio Symbols for transmission diagram
2.1 Motions of machine tool 2.2 Machine tool drive 2.3 Coordinate systems
现代数控机床原理与结构（双语） ppt 课件
2.1 Motions of machine tool
2.1.1 Purpose of motions The purpose of machine tool motions is to remove materials from workpieces to obtain required shapes, dimensions and surface quality. Motion essentials are tool motions, workpiece motions, and cutting motions. 2.1.2 Surface forming motion Surface forming motion is the relative cutting motion between tool and workpiece. Types and quantity of surface forming motion determine shape of workpiece, machining method and tool constructions
2.2.2 Transmission chain
A series of transmission components that consist a transmission connection is known as transmission chain.
Two forms of transmission
(1) Constant ratio and direction.
Gears, worm gears-shaft, ball screw-nut
(2) Variable and direction.
Adjusting gears, clash gears, clutch gear shift
Transmission chains include external and internal relations: 1) External relation Connecting power unit and actuators Driving actuators running at designed speed Determining machining efficiency and surface roughness rather than shape of workpiece.
现代数控机床原理与结构（双语） ppt 课件
Surface forming motion consists of :
Primary motion Feeding motion
Outer circular surface turning
现代数控机床原理与结构（双语） ppt 课件
1) Primary motion Primary motion causes relative motion between cutting tool and workpiece, and remove material from workpiece. Examples of primary motions:
现代数控机床原理与结构（双语） ppt 课件
书名：现代数控机床原理与结构（双语） ISBN： 978-7-111-42403-1 作者：郁元正 出版社：机械工业出版社 本书配有电子课件
现代数控机床原理与结构（双语） ppt 课件
Chapter 2 Motions & coordinate system of Machine tools
现代数控机床原理与结构（双语） ppt 课件
2) Feeding motion Feeding motion causes an secondary relative motion between cutting tool and workpiece, and enables tool can continuously remove material from workpiece to form a desired shape. Examples of feeding motion Axial and radial motions of cutting tool (turning) Step motions of cutting tool or workpiece (planing) Note: Feeding motion can be performed by both cutting tools or workpieces; Two or more feeding motions can co-exist (gear hobbing); Zero feeding motion is possible (broaching).
现代数控机床原理与结构（双语） ppt 课件
3) Alignment motion
It is used to obtain correct relative positions between cutting tool and workpiece, e.g. aligning drill to hole center by moving rocker arm of the driller.
4) Fast moving and other actions
Fast moving improves machining efficiency.
Other actions include direction change, clamping,
releasing, etc.
现代数控机床原理与结构（双语） ppt 课件
Rotary motion of workpiece (turning)
Rotary motion of cutting tools (drilling, milling, boring) Reciprocating motion of cutting tools (broaching, planing) Every machining process must have, and only has a primary motion.
They direct perform machining (2) Drive system, e.g. AC/DC motors, step motors, etc. They produce mechanical motion for actuators. (3) Transmissions. They transfer motion and power from drive system to actuators. Transmissions can be in mechanical, electric, hydraulic and pneumatic
2) Internal relation Connecting and regulating motions between actuators; Precise transmission ratio is important. Frictional transmission (e.g. clutch) or instantaneous variable ratio (chain drive) is unacceptable;
2.2.1 Transmission connection
Connection between actuator and power or between actuators by transmission components.
Transmission diagram of CA6140 horizontal lathe