機(jī)械英審數(shù)控技術(shù)

1、Numerical control technology 數(shù)控技術(shù)Numerical control is the type of digital control used on machine toolch as lathes and milling machines. These machine can automatically cut and sh the workpiece without a human operator. The workpiece is fastened to a movable table which can be moved in 3 directions:

2、 X, Y, Z. The table moves the workpiece past the cutting tool at a specified velocity and cutting depth. 4 parameters (X, Y, Z, rpm) is controlled by controller. The controller takes as itsinput a series of numbersThese numbers include the speed and feed rates.t compley describe how the part is to b

3、e made.physical dimens and such details as cutting1.Types of control system(1). Open loop systemOperates without verifying itiont the actualition is equal to the specifiedUsually a stepmotor(2). Closed loop control systemUses feedback measured to verify specified locationt theactualition is equal to

4、 theServo motor wifeedback loopThe feedback sensor used in as optical encoder. The encoder consists of a lightsource, a photodetector, and a disk containing a series of slots. The encoder is connected to the leadscrew. As the screw turns, the slots cause the light to beseen by the photodetector as a

5、 series of flashes which are convertedo anequivalent series of electrical pulses which are then used to characterize theition and the speed. The input to the control lop and the feedback signals area sequence of pulses, each pulse representing a BLU unit Basic Lengtit istheition resolution of the ax

6、is of motion. For example, 1 BLU = 1 mm, meanst the axis will move 1 mm for every one electrical pulse received by the motor.2. Coordinate systems 坐標(biāo)系統(tǒng)(1). Machine Coordinate Systems 機(jī)床坐標(biāo)系統(tǒng)Z 坐標(biāo)：規(guī)定平行于機(jī)床主軸的刀具運(yùn)動(dòng)坐標(biāo)為 Z 坐標(biāo)，取刀具原理工件的方向?yàn)檎较?；沒有主軸，則規(guī)定垂直于工件裝夾表面的坐標(biāo)為 Z 坐標(biāo)；X 坐標(biāo)：規(guī)定 X 坐標(biāo)軸為水平方向，且垂直于 Z 軸并平行于工件的裝夾面；Y 坐

7、標(biāo)：Y 坐標(biāo)垂直于 X、Z 坐標(biāo)；Workpiece Coordinate Systems 工件坐標(biāo)系統(tǒng)These are the coordinate systems used in programs. The location of the origin for a workpiece coordinate system can be set freely.Absolute and IncrementalThere are two types of coordinate specifications: absolute and incremental. These are toggled

8、using G90 and G91.The figure below shows the difference betspecifications on an XY plane. Absoluten absolute and incrementalspecifications indicate theition as the distance (or angle) from the workpiececoordinate origin, whereas incremental specifications indicate thethe distance (or angle) from the

9、 currentition.ition asProgrammingtspecifiesabsolutecoordinatesiscalledabsoluteprogramming, and programmingt specifiesincremental coordinates is called incremental programming.3. Main Word CharacteristicsSequence Number, NIts purnumbe is to identify the specific machining operation through the blocka

10、rticularly when testing a part program.Preparatory Functions, GIt prepares the MCUspecific operation.MicroprogrammedControlUnitcircuitstoperformaDimenWords1.2.3.Distance dimenCircular dimen Angular dimenwords X, Y, Zwords I, J, K for distan, A, B, Cto the arc centerFeedrate, FIt is expressedm/min. F

11、or example, a federate of F100 imps 100 mm/min.But in circular motions,F=(part contour radius tool radius) / part contour radius(feed). F=(工件輪廓半徑 刀具半徑) / 工件輪廓半徑(進(jìn)給).Spindle speed, SProgrammed in rev/min, it is expressed as RPM or by a three digit code numbert is related to thToolword, TM.Each cutting tool has a different code number.Miscellaneous Func