CN104318050B - Energy control method for constantly removing numerical control laser processing materials - Google Patents

Abstract

The invention provides an energy control method for constantly removing numerical control laser processing materials, belongs to the technical field of numerical control laser processing, and relates to a laser energy self-adaptive control method capable of ensuring constant material removal quantity. The method comprises the following steps that: firstly, the relationship among the existing laser diode work current, the processing speed and the ablation depth is obtained through process experiments, and the function relationship between the laser output current I(v) and the feeding speed v under the condition of the given removing thickness is worked out; a virtual main shaft is set, so that the laser output power can be remotely controlled through processing codes; the real-time speed of a path is obtained through counting the executed processing codes during the G codes are executed for processing workpieces; the real-time speed is substituted into a fitted equation to obtain the laser output current; and synchronization action codes are executed, and the laser output power is updated. The energy control method has the advantages that the self-adaptive regulation of the laser energy according to the actual feeding speed of a machine tool is realized, so that the constant material removing quantity is ensured, and the laser processing quality and the laser processing precision are improved.

Description

The energy control method of the constant removal of digital control laser rapidoprint

Technical field

The invention belongs to digital control laser processing technique field, is related to a kind of constant laser energy of guarantee material removal amount certainly Adaptive control method.

Background technology

Digit Control Machine Tool machining accuracy height has been gathered in digital control laser processing, flexible, can carry out 3 d part manufacture and swash Light processing without advantages such as tool wear, clearance height, the application in manufacture field is further extensive.Laser Processing realizes that material goes The principle removed is to irradiate surface of the work using high energy laser beam, and rapidly fusing is even gasified to make material.Laser beam is in surface of the work There is strong influence the time of staying of a certain position to the size of material removal amount, and the length of the time is fed by Digit Control Machine Tool Speed is determining.In the great part of processing Curvature varying, due to being limited by machine dynamic performance, machine tool feed speed is often Preset value is unable to reach, and actual speed is affected by many-side and cannot accurately be estimated, and causes workpiece to be sent out by excessive ablation phenomen Life simultaneously finally affects its accuracy of manufacture.Therefore, realize that laser beam energy follows lathe actual feed in digital control laser processing And self-adaptative adjustment is the key for ensureing that digital control laser processing removal amount is constant.

In order to realize the real-time monitoring to laser processing procedure and control, it is in metallographic noon et al. patent announcement number In the patent of " laser process equipment of controllable controlling laser beam length and intensity " of CN101928932A, made using photodetector Receive the laser beam that reflected by light beam isolating means for feedback means, and to measure and feed back to laser aid after its intensity, so as to control The laser beam intensity of laser aid output processed.But the method is detected only for beam intensity information, still cannot solve Certainly due to the uncontrollable caused energy excessive accumulation of feed speed.

In " the control that the laser in laser-processing system is servo-actuated that high cloud peak et al. patent announcement number is CN101693324A In the patent of method and system ", using encoder to detect the position of the servomotor, and the detection output of the encoder is believed It can be pulse signal that the counter in the PLC receives number to be processed, be transformed into, and then the PLC is according to the counter Value, it is timely within the current scan period that corresponding energy variation is exported to the laser instrument, laser is opened or closes laser controlling letter Number, real-time, the closed-loop control servo-actuated so as to realize laser.The method has not been set up using removal amount during different laser energy and work Make the coupled relation between platform feed speed, thus still need to by substantial amounts of repetition test to determine the removal amount of needs and feed Relation between speed.The content of the invention

The purpose of the present invention be for digital control laser processing in, due to by machine dynamic performance constraint actual feed without Method reaches preset value, and actual speed is difficult to Accurate Prediction, and in this case laser energy can make in surface of the work excessive accumulation Removal amount exceedes predetermined value and producing workpiece quality cannot meet this problem that requires, has invented a kind of in digital control laser processing Ensure the constant energy self-adaptation control method of material removal amount, with solve crudy that constant energy Laser Processing causes and Machining accuracy is unsatisfactory for desired problem.The method considers the restriction of machine dynamic performance, establishes laser ablation amount and enters To the relation between speed；Simultaneously based on commercialization digital control system, using laser energy as virtual main shaft, Real-time Collection lathe Actual feed simultaneously adjusts the virtual speed of mainshaft according to the speed, to realize laser energy according to lathe actual feed Self-adaptative adjustment, so as to ensure that material removal amount is constant, improves the crudy and machining accuracy of Laser Processing.

The technical solution adopted in the present invention is：A kind of energy control method of the constant removal of digital control laser rapidoprint, Characterized in that, first, it is triangular by technological experiment known laser diode operating current, process velocity and ablation depth Relation, obtains the given functional relation for removing laser output current I (v) and feed speed v under thickness condition；Then, set empty Intend main shaft so that the power output of laser can carry out remotely control by machining code；By performing G code processing workpiece The executed machining codes of Shi Tongji, including the number of G1/G2/G3 Interpolation Codes, obtain the real-time speed in path, substitute into fitting The equation for going out, obtains laser output current；Synchronization action code is performed, laser output current is updated, realizes that digital control laser is processed The middle energy self-adaptation control for ensureing that material removal amount is constant；The control method is comprised the following steps that：

1) functional relation of laser output current I (v) and feed speed v

Based on Srinivasan-Smrtic-Babu theoretical models, single-pulse laser ablation depth is d,

Wherein, F- laser energy densities, k₀- laser ablation depth scale coefficient, F_thThe ablation threshold of-target material, E^*- Effective activation energy, α-absorption coefficient；

Using Gaussian laser beam, and adjacent laser pulse distance is assumed from for Δ x, processing starting point adds for first laser The forward position of work pulse, then completely removed the material that specified dot thickness is D, and required laser pulse number is n_sum=2n_m+ 1, n-th pulse processing starting point Energy distribution be：

Wherein, w is Beam waist radius；According to single-pulse laser ablation depth formula, n-th laser pulse is in specified point Ablation depth be：

Make F_n≥F_thWhen, then the laser pulse number needed for appointed thickness material is removed completely is

Ignore the duration of nanosecond pulse laser, then the distance between two adjacent laser pulses is Δ x=v/f, wherein, V is feed speed, and f is the repetition rate of laser pulse；

Processing straight trough as sample, adopt the straight trough depth that Constant feeding rate is processed through one group of laser pulse sequence for

By obtaining k in formula (5)₀, E^*And F_thValue, by sample analysis, set up laser working depth D and laser energy Relation between density F and feed speed v：

F=f (D, v)=f (v) (6)

After given laser working depth, required laser energy density F under different feed speeds v is obtained, and then obtained at certain Under one laser frequency, when processing obtains identical groove depth, the respective function relation of laser output current I (v) and feed speed v；Intend Closing functional equation is：

I (v)=a₀+a₁v+a₂v² (7)

2) virtual main shaft is set

To the external control current-mode analog quantity input pin input voltage value of laser instrument external control laser interface, by digital analog interface Module realizes control system output voltage analog quantity；Second analog set point that digital analog interface module is not yet assigned to main shaft is connect Mouth distributes to laser instrument；The second main shaft rated speed value is set to maximum operating currenbt in digital control system, compiles in machining code The range of spindle speeds of journey second correspond to digital analog interface module output voltage range, also correspond to laser current scope；Second The speed of mainshaft and laser current numerically equal, directly change laser output power by writing the speed of mainshaft；

3) laser current output code is write in synchronization action mode

While G code is performed, executed machining code, including the number of G1/G2/G3 Interpolation Codes are counted, this Individual number is stored in synchronization action variable AC_MARKER [0]；Real-time path speed is obtained by system variable $ AC_VACTB Degree, substitutes into the equation for fitting, and obtains laser output current：

S=a₀+a₁*$AC_VACTB+a₂*$AC_VACTB*$AC_VACTB；

If often performing two row machining codes just to update once, to $ AC_MARKER [0] divided by 2 remainders, when remainder is 1 When, synchronization action code is performed, update laser output power；

If often performing n rows machining code just to update once, to the synchronization action variable divided by n remainders, when remainder is 0 When, synchronization action code is performed, update laser output power；

By in the embedded machining code of synchronization action so that the speed of mainshaft (laser current) follows interpolation cycle synchronous circulating brush Newly, keep while feeding, realize the real-time control of power and path velocity.

The invention has the beneficial effects as follows the control method using laser energy as virtual main shaft, the reality of Real-time Collection lathe Feed speed simultaneously adjusts the virtual speed of mainshaft according to the speed, being capable of real-time adjustment laser output power, it is ensured that material removal amount Constant, the self adaptation variable power control method accuracy is good.

Description of the drawings

Figure of Fig. 1-spiral of Archimedes under polar coordinates, wherein, 1 is spiral of Archimedes, 5,10,15, 20th, 25 the length of radius vector r is represented respectively, A, B, C, D, E, F are respectively six that polar angle on spiral of Archimedes is separated by 360 ° Test point.

Fig. 2-spiral of Archimedes central area enlarged drawing, wherein, O is polar limit, and r is radius vector, r₀For pole Corresponding radius vector when angle is 0 °, θ is polar angle, is represented from pole axis to the angle of radius vector r.

The curve that the spiral of Archimedes reality processing speed of Fig. 3-obtained by speed monitoring is changed with process time Figure.Wherein, x-axis is the reality processing time, and unit is the second (s), and y-axis is reality processing speed, and unit is mm/min.

The control voltage monitoring figure of Fig. 4-input laser controlling case.Wherein, x-axis is the reality processing time, and unit is s, y Axle is the input voltage for being input into laser controlling case, and unit is V.

Two kinds of control mode ablation depth comparison diagrams during Fig. 5-processing spiral of Archimedes.Wherein, x-axis is in accompanying drawing 1 The radius vector lengt of six ablation depth test points, unit is mm, is the radius vector lengt of each point in bracket, and y-axis is six ablation depths Degree test point ablation depth, unit for μm, curve 1 be laser constant power output mode under ablation depth with Archimedian screw The change of line radius vector, curve 2 is that under laser self-adoptive Variable power output control mode, ablation depth is sweared with spiral of Archimedes The change in footpath.

Specific embodiment

The specific embodiment of the present invention is described in detail below in conjunction with technical scheme and accompanying drawing.

Machining experiment condition is as follows：Laser process equipment selects Draco series lasers, and digital control system is using German west gate Subsidiary's 840D sl digital control systems, its digital analog interface module is ADI4, and rapidoprint is copper-clad plate, and cutting-in is 3.5 μm, setting Feed speed be F=4000mm/min, processing graphic pattern be radius for 23mm spiral of Archimedes, spiral of Archimedes Equation is r=0.6 θ+0.189, and as shown in Figure 1, its central area enlarged drawing is as shown in Figure 2.Comprise the following steps that：

(1) first, it is triangular by technological experiment known laser diode operating current, process velocity and ablation depth Relation, using formula (1) above to formula (7), obtains laser output current I (v) and feeding under given removal thickness condition The functional relation of speed v.Count when frequency is 40KHz, when processing obtains 3.5 μm of groove depths, laser output current is fast with feeding The respective function relation of degree.Sample fitting result approximately linear, and meet equation：I (v)=- 0.1335v²+4.35v+30.8。

(2) Draco laser instruments provide an ANALOG25 pin external control laser interface, its 5th pin external control current analog Input stitch.The pin is input into the magnitude of voltage of 0～10V, then laser instrument correspondence power is with 0～100% output.Controller inside can To realize the Adaptive matching of external input voltage and laser output power by the parameter setting of rated operational current.

Communicated by PROFIBUS industrial field bus between ADI4 and NCU, for driving using analog signalses Main shaft, the frequency converter that main shaft is carried is capable of achieving the change of 0rpm to maximum speed by the control voltage that digital analog interface module is provided Change, so as to realize that main shaft is rotated by setting value.

By second analog set point interface assignment of ADI4 to laser instrument.Because laser instrument 60A is maximum operating currenbt, counting Second main shaft rated speed is set for 60rpm, then second 0～60rpm of the speed of mainshaft is programmed in machining code in control system Then correspond to ADI4 modules and export 0～10V, also correspond to 0～60A of laser current.Directly by writing the speed of mainshaft by change Become laser output power.

(3) machining code is write, is run in synchronization action mode and is write laser current output code, and carry out operation and added Work.

After synchronization action variable $ AC_MARKER [0] is set to 0, to executed machining code, including G1/G2/G3 interpolations The number of code is counted, and statistics adds up and is stored in synchronization action variable $ AC_MARKER [0]；Hold when meeting When the number of capable machining code can be divided exactly by 2, machine velocity is obtained, real-time road is obtained by system variable $ AC_VACTB Footpath speed, substitutes into the equation for fitting, and obtains laser output current (" main shaft " rotating speed)

S=a₀+a₁*$AC_VACTB+a₂*$AC_VACTB*$AC_VACTB

Update laser output power.The synchronization action machining code write is as follows：

N01 $ AC_MARKER [0]=0

N02 ID=1 WHENEVER ($ AC_TIMEC==0) AND ($ AC_BLOCKTYPE==2) DO $ AC_MARKER [0]=$ AC_MARKER [0]+1

N03 ID=2 DO $ AC_PARAM [0]=$ AC_VACTB/1000

N04 ID=3 EVERY $ AC_MARKER [0] MOD 3==0 DO M3S=-0.1335* $ AC_PARAM [0] * $ AC_PARAM[0]+4.35*$AC_PARAM[0]+30.8

By in the embedded machining code of synchronization action so that the speed of mainshaft (laser current) follows interpolation cycle synchronous circulating brush Newly, keep while feeding, realize the real-time control of power and path velocity.

Accompanying drawing 3 is the song that the spiral of Archimedes reality processing speed obtained by speed monitoring is changed with process time Line, as seen from the figure, during processing spiral of Archimedes, machine tool feed speed is continuous with the change of Archimedes spiral diameter vector Change.The control voltage monitoring figure of laser controlling case is input into as shown in Figure 4, it can be seen that control voltage is with really The change of border feed speed and change, and the variation tendency of the two is identical, so as to realize laser energy according to the actual feeding of lathe The self-adaptative adjustment of speed.Accompanying drawing 5 is the helix processing that both control modes are exported using constant power output and Variable power Contrast and experiment.Ablation depth in measurement accompanying drawing 1 at six points of A, B, C, D, E, F, curve 1 is laser perseverance work(in accompanying drawing 5 Ablation depth, because in the graphic center portion point curvature is larger, enters with the change of Archimedes spiral diameter vector under the rate way of output Preset value is unable to reach to speed, thus actual ablation depth is significantly greater than predetermined depth；Curve 2 is laser self-adoptive Variable power Under output control mode, ablation depth with Archimedes spiral diameter vector change, laser output power with reality processing feed Velocity variations and change, ablation depth is basically unchanged.Experiment proof is caused for being limited by machine dynamic performance actually to be entered Preset value this problem can not be reached to speed, the control method being capable of real-time adjustment laser output power, it is ensured that material is removed Amount is constant, and the self adaptation variable power control method has feasibility and accuracy.

Claims (1)

1. the energy control method of the constant removal of a kind of digital control laser rapidoprint, it is characterised in that first, by technological experiment The triangular relation of known laser diode operating current, process velocity and ablation depth, obtains given removal under thickness condition The functional relation of laser output current I (v) and feed speed v；Then, virtual main shaft is set so that the power output energy of laser Enough remotely control is carried out by machining code；By counting executed machining code when G code processing workpiece is performed, including The number of G1/G2/G3 Interpolation Codes, obtains the real-time speed in path, substitutes into the equation for fitting, and obtains laser output current； Synchronization action code is performed, laser output current is updated, realizes ensureing the constant energy of material removal amount in digital control laser processing Self Adaptive Control；The control method is comprised the following steps that：

1) functional relation of laser output current I (v) and feed speed v

Based on Srinivasan-Smrtic-Babu theoretical models, single-pulse laser ablation depth is d,

$d=k_0\·\exp \[(-E^{*}\·ln\frac{F}{F_{th}})/(\mathrm{\α}\·(F-F_{th}\left)\right)\]---\left(1\right)$

Wherein, F- laser energy densities, k₀- laser ablation depth scale coefficient, F_thThe ablation threshold of-target material, E^*- effectively Activation energy, α-absorption coefficient；

Using Gaussian laser beam, and adjacent laser pulse distance is assumed from for Δ x, processing starting point is first Laser Processing arteries and veins The forward position of punching, then completely removed the material that specified dot thickness is D, and required laser pulse number is n_sum=2n_m+ 1, n-th Individual pulse processing starting point Energy distribution be：

$\begin{array}{cc}{F}_n=2\·F\exp (-\frac{2{\left(n\mathrm{\Δ}x\right)}^2}{w^2})& n\∈\{-n_m,-n_m+1,...,0,1,...,n_m\}\∩\mathrm{\Δ}x\∈\[-w,+w\]\end{array}---\left(2\right)$

Wherein, w is Beam waist radius；According to single-pulse laser ablation depth formula, burning of n-th laser pulse in specified point Losing depth is：Make F_n≥F_thWhen, then will Appointed thickness material is removed completely required laser pulse number

$n_{sum}=2n_m+1=2\×\sqrt{\frac{w^2}{2{\mathrm{\Δx}}^2}ln\frac{F}{F_{th}}}+1---\left(4\right)$

Ignore the duration of nanosecond pulse laser, then the distance between two adjacent laser pulses is Δ x=v/f, wherein, v is Feed speed, f is the repetition rate of laser pulse；

Processing straight trough as sample, adopt the straight trough depth that Constant feeding rate is processed through one group of laser pulse sequence for

By obtaining k in formula (5)₀, E^*And F_thValue, by sample analysis, set up laser working depth D and laser energy density F Relation and between feed speed v；

After given laser working depth, required laser energy density F under different feed speeds v is obtained, and then obtain swashing a certain Under light frequency, when processing obtains identical groove depth, the respective function relation of laser output current I (v) and feed speed v；Fitting letter Counting equation is：

I (v)=a₀+a₁v+a₂v² (6)

2) virtual main shaft is set

To the external control current-mode analog quantity input pin input voltage value of laser instrument external control laser interface, by digital analog interface module Realize control system output voltage analog quantity；Digital analog interface module is not yet assigned to into second analog set point interface point of main shaft Dispensing laser instrument；The second main shaft rated speed value is set to the numerical value of maximum operating currenbt in digital control system, in machining code Program the second range of spindle speeds and correspond to digital analog interface module output voltage range, also correspond to laser current scope；The Two speeds of mainshaft and laser current numerically equal, directly change laser output power by writing the speed of mainshaft；

3) laser current output code is write in synchronization action mode

While G code is performed, executed machining code, including the number of G1/G2/G3 Interpolation Codes, this number are counted Mesh is stored in synchronization action variable $ AC_MARKER [0]；Real-time path velocity is obtained by system variable $ AC_VACTB, The equation that substitution is fitted, obtains laser output current：

S=a₀+a₁*$AC_VACTB+a₂*$AC_VACTB*$AC_VACTB；

If often performing two row machining codes just to update once, to $ AC_MARKER [0] divided by 2 remainders, when remainder is 1, hold Row synchronization action code, updates laser output power；

If often performing m rows machining code just to update once, to the synchronization action variable divided by m remainders, when remainder is 0, hold Row synchronization action code, updates laser output power；

By in the embedded machining code of synchronization action so that the speed of mainshaft (laser current) follows interpolation cycle synchronous circulating to refresh, Feed simultaneously and keep, realize power and path velocity real-time control.