DD148599A1 - METHOD AND DEVICES FOR CONTROLLING AND REGULATING TECHNOLOGICAL LOADING BEAM PROCESSES - Google Patents

Abstract

The invention relates to the control, adjustment and control of beam focusing, beam centering and technological processes in charge jet blasting processes. The aim is to increase the work productiveness and to improve the product quality. The task of determining a measurable process quantity which directly reproduces the correlation between the degree of focusing, centering state and process parameters and the process results resulting in control, adjustment and regulation of the beam focus maintenance, beam centering and process stabilization with a short time constant is thereby achieved in that the steam flow emanating from the action of the charge jet jet on the workpiece from the process site is converted into an equivalent electrical quantity by means of suitable meters and the DC component (mean value) and / or AC component (RMS, positive and negative amplitude and pulse injection) of the measurement signal for control, Adjustment and regulation of beam focusing, beam centering and charge jet blasting processes are used.

Description

218559

Methods and devices for controlling and regulating technological charged particle beam processes

Field of application of the invention

The invention relates to a method and devices for process control and regulation in technological processes with charged particle beams, in particular for welding, evaporation, spraying, cutting, melting and material processing.

Characteristic of the known technical solutions

It is already known to measure the backscatter associated with the process in electron beam welding, workpiece and penetrating electron current, and their DC component (average) and AC component (amplitude, frequency and pulse length) to stabilize the weld geometry Furthermore, certain components of some parameters are used to set and control the beam focusing and beam centering Using the backscattered electron current as the measured variable, the process is guaranteed up to a beam output of approximately 5 kW · At higher beam powers, however, changes occur the behavior of the backscattered electron stream

218559

For example, the characteristic inflection points of the measurement signals and the maximum seam depth occur at different focusing currents. '-

The utilization of the workpiece electron flow for process control and regulation has the decisive Nadateilj that the workpiece for Meßsignalgewinnung to ground must be completely isolated, making high demands on the welding devices. As a result, research results are available only for low beam power and simple welding tasks. The control and stabilization of the seam depth using the Durchdringungselektronenstromes Prozeßmeßsignal is in principle for each beam power possible conditions, however, the penetration of the workpieces and sufficient accessibility below the weld to the arrangement of the Meßsignalauffängers. However, if the degree of focus changes during welding or after several hours of operation (with time-dependent change in distance between the cathode control electrode and the cathode anode), the condenser, for example, increases the beam power or reduces the welding speed until the setpoint value of the permeation electron current is reached. Although the seam depth is thus stabilized, the weld seam widens, the heat input increases, and in the seam, pores and solidification may occur due to the focussing wheel change.

It is also known to measure the resulting during electron beam welding, the process associated with the Prozöß above or in the case of Werkstückdurchschweißung also below the weld and their DC component (average) and AC component (amplitude, frequency and pulse length)

218559

Stabilization of the weld geometry by process control and single or multi-loop process control exploit. These components are also used to adjust and control the beam focusing and beam centering.

If the ion current above the weld is measured and the mean value or the alternating current amplitude is used as the measurement signal, the performance of the method is ensured up to a beam output of approximately 60 kW. At higher Stecahlleistungen however, extremely low-frequency interferences, which are caused by the molten-bath dynamics, increasingly occur in the measuring signal. The measurement signal change is much stronger in these cases than the change in the seam geometry, whereby the process control and regulation is difficult. The use of the frequency or pulse length requires from about 10 kW beam power special electronic measures for signal conditioning (filter).

If the ion current flowing out of the welding capillary is measured, then the advantage over the penetrating electron current is that information about the degree of focusing is simultaneously contained in the measuring signal, however, the workpiece penetration and access below the welding point are necessary conditions for process control and regulation.

It is also known to exploit the light radiation (direct and infrared spectrum) emerging from the molten bath during electron beam welding to stabilize the weld geometry by process control and regulation and to adjust and control the beam focusing, optoelectronic components being used for measuring signal extraction. Since the metal vapor produced during welding also condenses on the surface of the sensor, the performance of the

_ ₄ _ 218559

short-term operation possible with low beam power * For higher beam power the method is not suitable and consequently no test results are available.

Furthermore, it is known to use the sound emission caused by the electron beam welding process for process control and adjustment of the beam focusing, the sensors are always coupled to the workpiece · However, the öchallemission resulting from the welding device with its drive and by the vacuum pump system acts as a disturbance, with Nutz - And interference signal depending on the process conditions in the same frequency spectrum can be. In addition, since Meßsigna recovery requires a coupling between the workpiece and the probe, the practice of the method is difficult especially when welding axial and radial circumferential seams.

Object of the invention

The invention provides a method and devices for process control and regulation in carrier beam technological processes which is capable of improving labor productivity and product quality even under such process conditions where already known processes fail or provide unsatisfactory results.

The essence of the invention

-5- 21S559

The invention has for its object to determine a measurable process variable for technological processes with charged beams, which directly reproduces the correlation between the individual process parameters and the resulting process result and for each beam power to stabilize the process result by process control and control with low time constant and Adjustment and control of beam focusing and beam centering is suitable.

According to the invention, the object is achieved by converting the vapor stream emanating from the processing location by the action of the charged particle beam from suitable measuring sensors into an equivalent electrical quantity and determining the direct current component (mean value) and / or alternating current component (rms value, mean value, average and maximum positive and negative amplitude, frequency, pulse length and pulse peaks) of the measurement signal to stabilize the process result by process control and single or multi-loop process control and to set and control the beam focusing and beam centering by hand or automatically used.

Under certain conditions of the technological process, it is expedient to select only a certain fre quency spectrum from the measured signal, and / or to subject the measuring signal in the course of its processing to a single or multiple frequency division and / or multiplication, in order to achieve a process control To achieve forced process dynamics (resonance) and to increase the sensitivity during the process.

218559

Furthermore, it is expedient under certain technological conditions in a multi-loop control to include in addition to the vapor stream already known Prozeßmeßsignale (in particular the ion current) in the control process.

For measuring the vapor flow, it is advantageous to arrange one or more sensors in the space between the gun and workpiece and workpiece penetration, if necessary, also under the workpiece such that the outgoing steam from the process location can get to the sensors and the process-dependent angular distribution of the Bampfstromes does not affect the measurement signal or is used in the Meßsignalgewinnung with.

The MeßSignalgewinnung is advantageously carried out by the technological process constructively adapted electronic probe, in particular on Elektronenstrom-, Ionisation-, discharge and / or Wärmeleitbasis, against foreign, associated with the charge carrier beam process in connection electrons and ions usually by suitable arrangement of gratings shielded corresponding potential, optionally designed as a pressure stage and can be in communication with a special vacuum pumping system.

In certain technological charge carrier beam methods, it may also be expedient to use sensors adapted to the process, preferably on an electromechanical, capacitive, inductive and / or picoelectric basis, which are optionally shielded against foreign charge carriers, preferably by potential-carrying gratings.

2185 5 9

For process control, the actual value of one or more components of the measurement signal is displayed or stored by suitable devices, although the corresponding nominal values are indeed to be determined for the respective technological process.

In process control, the actual value of one or more components of the measurement signal is supplied to an analog or digital electronic controller, which may optionally be a process computer, in particular a microcomputer, and compared with one or more setpoints, after which the controller corresponding to the control deviations and the associated process equations For this purpose, suitable for the respective component of the measuring signal (direct current, average and effective alternating current, average and maximum, positive and negative Viechseistromamplitude, frequency, pulse length and pulse peaks) suitable one Command value (acceleration voltage, beam current, modulated beam current, dynamic beam deflection in the x and / or y direction, possibly with symmetrical and / or asymmetrical half-wave, focusing current, welding speed) ausw "The control parameters to be used must first be determined for the respective technological process.

If, under given process conditions, the degree of focusing of the charged particle beam varies in the range from sub-to overfocusing, there is a focusing current intensity at which the impact of the charged-particle beam on the material is most intense

-β- 218559

is and the individual components of the measuring signal have a characteristic turning point. The specification of the required focusing current (operating point) for the respective process takes place according to a test program in accordance with the technological requirements.

For setting and controlling the beam focusing, the relative values of one or more components of the measuring signal and of the focusing current between the inflection point and the operating point are used. The permissible deviations must first be determined by tests. i) The procedure may be carried out manually or automatically and at the appropriate speed during the ongoing process. If the beam centering varies under given process conditions, there is a centering current intensity for each of the x and y directions in which the action of the charge beam on the material is most intense (highest power density, best power density distribution, minimum aberrations) and the individual Components of the measuring signal have a characteristic inflection point. To adjust and control the beam centering, the centering currents for the x and y directions are alternately varied under process conditions by the method of stepwise approximation under process conditions such that the operating points lie exactly in the corresponding inflection point of the respectively used Meßsignalkomponente. The implementation of the method can be done manually or automatically and at the appropriate speed during the ongoing process. ,

-9- 218559

embodiment

The invention will be explained in more detail below with reference to several embodiments. In the accompanying drawings:

Fig. 1: a scheme for process control and - regulation in electron beam welding

Fig. 2? the scheme of a DampfstrommeßfUhlers ... on electron current basis

Fig. 3ϊ shows the diagram of a DampfStrommeßfühlers ionization-based

Fig. 4ϊ shows the diagram of a DampfStrommeßfühlers on electromechanical basis.

According to FIG. 1, the electron beam ES generated by the electron beam welding gun 1 strikes the work piece 2 of the thickness s arranged in the working distance a, which moves relative to the electron beam ES at the welding speed v _o . With appropriate coordination of the individual process parameters creates a weld of depth h. During welding, a certain proportion of material evaporates at the same time, so that a steam flow DS emerges from the welding capillary, which is directed into the tree between the workpiece 2 and the electron beam welding gun 1. The steam flow DS is process-dependent (material, process parameters, process dynamics)

-ί- 218559

for a given material, the depth of cut h _{n is} proportional. For converting the vapor stream OS into an equivalent electrical quantity, a probe 3 directed towards the weld capillary is arranged under the electron beam welding gun 1 in the vicinity of the electron beam ES, which sensor is connected to an electronic switching arrangement for measuring signal acquisition MSG. The sensor 3geraäß Fig. 2, consists of a housing 4, in which a triode system of directly heated cathode 5, control grid 6 and anode 7 is arranged. Optionally screen and brake grid between the cathode 5 and anode 7 are also arranged. When welding in pre-vacuum or high performance, the housing 4 is designed with respect to the Sßhweißkammer as a pressure stage and connected to a special vacuum pumping system VPS. The required operating voltages for the triode system (heating voltage U 1, anode voltage U, control voltage UJ are provided by the electronic circuit arrangement for measuring signal recovery MSG.) Under operating conditions, an electron current I flows from the cathode 5 to the anode.

ti

voltage U. can be adapted to the control grid 6 different process conditions. If the steam flow DS emanating from the welding capillary reaches the measuring sensor 3, the current flow I in the triode system is weakened as a function of the intensity of the steam flow DS.

To shield the probe 3 against the electrons and ions occurring during electron beam welding grids 8 are arranged in the beam path, which lead to ground a certain positive and negative potential. The grounded grid 8 is primarily for field separation.

218559

The fulfillment of the condition steam flow DS * zero ^

Measurement signal MS * zero is effected by a corresponding zero correction, NK (FIG. 1). The process-dependent Meßsig-, nal then passes directly or via electronic filters eF with low, band or high pass to electronic switching arrangements, in each of which the average MW, RMS EW, the positive amplitudes pA, negative amplitude nA, frequency F and pulse length IL proportional voltage is generated.

For process control, the actual value χ of one or more characteristic Meßsignalkomponenten whose nominal values are previously to be determined for the respective process conditions, displayed by a measuring instrument MI or stored a light beam writer LSS. In the single-loop process control, the actual value x of a characteristic measuring signal component in an electronic controller eE is compared with the corresponding desired value w. Depending on the control deviation and the associated process equation, the controller computes the control signal SS for controlling the control element SG for the manipulated variable y used (beam current I, beam deflection I, welding speed V, acceleration voltage U _β , focusing current I). If only positive or negative impulse peaks of the measuring signal MS are to be used for the process control, a threshold value switch SWS whose threshold value SW is continuously adjustable is provided in the signal path in front of the electronic controller eR. However, the process control can also be designed in such a way that the measuring signal MS via electronic switching arrangements for frequency division FT or frequency multiplication FV to the electronic controller eR passes. The too

218559

The control parameters used must first be determined for the respective technological process. The measuring sensor according to FIG. 3 consists of a housing 4 in which a triode system of directly heated cathode 5, control grid 6 and anode 7 as well as a collecting electrode 10 for the positive material vapor ions are arranged.

Optionally screen and brake grid between the cathode 5 and anode 7 are also arranged. When welding in the pre-vacuum or with high beam powers, the housing 4 is designed with respect to the welding chamber as a pressure stage and connected to a special vacuum pumping system VPS. The required operating voltages for the triode system (heating voltage U ™, anode voltage U, control voltage U +) are provided by the electronic circuit arrangement for measuring signal acquisition MSG. Under operating conditions, an electron current I ₀ flows from the cathode 5 to the anode 7, the intensity of which is adapted to the different process conditions via the control voltage U _s + at the control grid 6. If the steam flow DS coming from the welding capillary reaches the measuring sensor 3, then at constant, ionized sufficiently large current I in the triode system of the steam flow DS depending on its strength · These vapor ions are from the collecting electrode 10, via a voltage source from the electronic circuit arrangement for Meßsignalgewinnung MSG and a resistor K-. is connected to ground and receives a certain negative potential, sucked, whereas the electrons are repelled. About the resistor A voltage drop (measurement signal MS) is available, which is proportional to the strength of the vapor flow DS · To shield the probe 3 against the electrons and ions occurring during electron beam welding

-13- 21855

arranged in the beam path grid 8, which lead to a certain positive and negative potential with respect to ground · The grid connected to ground 9 is mainly used for field separation «

The fulfillment of the condition steam flow DS · zero - · - ·> measuring signal MS = zero is effected by a corresponding zero correction NK (FIG. 1).

4 consists of a housing 4, in which an optoelectronic system of light emitting diode 11 and photodiode 12 is arranged · The light beam from the light emitting diode 11 to the photodiode 12 is interrupted by a plate 13, which with a fine-mechanical, low-inertia lever system Tack 14, lever arm 15, shaft 16 and ball bearing 17 is in communication and is held by a spring 18 in rest position. The required operating voltages for the optoelectronic system are provided by the electronic circuit arrangement for measuring signal acquisition MSG. If the steam flow DS emanating from the welding capillary strikes the catching plate 14, light comes to the photodiode 12 as a function of the intensity of the steam flow DS, the light emitting diode 11 operating in constant-current operation. In continuous operation or higher welding performance, the housing 4 is surrounded in the direction of welding by a heat shield 20 fastened with insulators 19 in order not to change the temperature conditions for the optoelectronic system.

The fulfillment of the condition steam flow DS * zero ---> measuring signal MS ^s zero is effected by a corresponding zero correction NK (FIG. 1) o

If, under given process conditions, the degree of focusing of the electron beam ES varies in the range from sub-to overfocusing, there exists one

21 855

Focusing current intensity I ₅₁ , in which the depth of the seam is greatest and the individual components of the measuring signal MS, which are displayed by a measuring instrument MI or are recorded by a light-beam recorder LSS, have a characteristic inflection point. The definition of the required for the respective process focusing current (operating point) is carried out according to a test program according to the technological requirements.

In order to set and control the beam focusing, the relative values of one or more components of the measuring signal MS and of the focusing current intensity Xp between the point of inflection and the operating point are used, and the permissible deviations must first be determined by tests.

If the electron beam centering is varied under given process conditions, then for the x- and y-direction respectively, a centering current strength at which the seam depth h "is greatest and the individual components of the measurement signal MS stored by a measuring instrument MI or recorded by a light-beam recorder LSS have a characteristic Point of inflection. To adjust and control electron beam centering, the centering currents for the x and y directions are alternately varied under process conditions, usually on a phantom, in such a way that the operating points lie exactly in the corresponding center point of the respectively used measuring signal component.

Claims (3)

218559 Brfindungsanspruch 1. Process for process control and regulation in technological processes with charged particle beams, in particular for welding, evaporation, spraying,
Cutting, melting and material processing,
characterized in that by the action of the charge carrier beam
on the material from the process point outgoing vapor stream (DS) by means of suitable sensor (3) is converted into an equivalent electrical size and the
DC component (mean) and / or AC component (RMS, mean, mean)
and maximum positive and negative amplitude, frequency, pulse length and pulse peaks) of the measurement signal to stabilize the process result by process control and single or multi-loop process control and for setting and controlling the beam focusing and
Beam centering can be used by hand or automatically. Method for process control and regulation in technological processes with charged-particle beams
Point 1, characterized by the fact that under certain conditions of
expediently only one technological process
specific frequency spectrum from the measuring signal (MS)
selected and / or the measuring signal (MS) in the course
its processing one or more times 21855 Frequency division (FT) and / or -Vielielung (FV) is subjected, in such a way that, in particular, the process control achieved a forced process dynamics (resonance) and the sensitivity in the process exercise is increased. 3 · Method for process control and regulation in technological processes with charged particle beams according to items 1 and 2, characterized in that under certain technological conditions in a multi-loop control preferably also already known Prozeßmeßsignale, in particular the ion current, are included in the control process · 4 "method for process control and control in technological processes with charged particle beams according to item 1, 2 and 3, characterized in that for measuring the vapor flow (DS) one or more sensors (3) in the space between the gun (1) and workpiece (2 ), at V / erkstückdurchdringung possibly under the workpiece (2) can be used by the outgoing from the processing point steam flow (DS) to the sensors (3) passes, so that the process-dependent Winkeiverteilung the vapor stream (DS) the measuring signal ( MS) is not affected or exploited in the measurement signal acquisition (MSG). -ι? - 21 85 59 5 # Method for process control and regulation in technological processes with charged-particle beams according to items 1 to 4 * characterized in that the Ifleßsignalgewinnung (MSG) preferably by the technological process constructively adapted electronic probe (3)> in particular electron flow, ionization, discharge and / or Wärmeleitbasis, which are shielded against foreign, with the charge carrier jet process related electrons and ions preferably by a suitable arrangement of gratings (8) with the appropriate potential and optionally designed as a pressure stage and with a special vacuum pump system (VPS) in Connection stand. Method for process control and regulation of technological processes using charged-particle beams according to items 1 to 4, characterized in that, in certain technological charged-particle beam methods, sensors (3) which are structurally adapted to the process are used on electromechanical, capacitive, inductive and / or pizoelectric basis, which are optionally applied against foreign charge carriers, in particular by potential-carrying grids (8) are shielded 7. Device for carrying out the method according to item 1, characterized in that between the electron beam welding gun (1) and the workpiece (2) in the vicinity of the electron beam (ES) directed to the welding capillary 218559 Sensor (3) consisting of housing (4), a triode system of directly heated cathode (5), control grid (6) and anode (7) is arranged, optionally between the cathode (5) and anode (7) shield and Brake grille are provided and the beam path grid (8), which lead a certain positive and negative potential. 8. Device for carrying out the method according to item 1, gekenn ze lehnet by a sensor (3) consisting of the housing (4) with triode system of directly heated cathode (5), control grid (6) and anode (7) and one Screening and braking grid between the cathode (5) and anode (7) are optionally provided and the housing (4) opposite the welding chamber formed as a compression stage and with a special Yakuumpumpsystem (VPS) is connected to positive material vapor ions receiving electrode. Device for carrying out the method according to point 1, characterized du rch a sensor (3) consisting of light emitting diode (11) and photodiode (12) and plate (13), with a precision mechanical, low-inertia lever system consisting of tacks (14), Lever arm (15), shaft (16) and ball bearing (17), is in communication 21855 and is held in a rest position by a spring (18), wherein the housing (4) is optionally surrounded in the direction of welding by a heat shield (20) fastened with insulators (19). - For this 4 sheets drawings -