Patent ID: 12247863

In some embodiments, components may be combined, split into multiple components, and/or additional components may be added without affecting the functionality of the invention. In some embodiments, method steps can be switched in their order, carried out in parallel, combined or divided and/or further steps can be added without affecting the function of the method according to the invention.

FIG.1schematically shows a device10for measuring a powder mass flow for powder cladding according to an embodiment of the invention. InFIG.1, the powder mass flow is shown schematically with solid arrows. Dashed lines show connections for signal and/or data exchange between different components. The connections for signal and/or data transmission may be wired and/or wireless.

In this embodiment, the powder mass is fed by means of two powder metering devices, the powder metering devices11aand11b. The powder metering devices are configured to generate a powder mass flow. The powder mass flows are combined in a Y connection13to form a common powder mass flow. In an embodiment with a powder metering device, the Y-connection may optionally be omitted. In some embodiments, particularly when the device comprises multiple powder metering devices, the device may comprise multiple Y-connections and/or alternatives such as mixers or n-fold Y-connections.

The common powder mass flow generated in this way is routed to a powder switch15via a powder mass flow sensor14. Depending on the driving of the powder switch15, the powder switch directs the powder mass flow to a process head16and/or scales18. The powder switch is controlled by the control unit20in this embodiment.

In this embodiment, a powder separator17is mounted between powder switch15and scale18. It may be configured to separate the powder from a gas or gas mixture, in particular a shielding gas.

In some embodiments, the control device20may consist of a plurality of partially independent control devices. In this embodiment, the control device is configured to control and/or regulate the powder metering devices11a,11bas a function of sensor data from the powder mass flow sensor14and/or as a function of data/signals from the scales18and a specified powder mass flow.

In this embodiment, the control unit20is further configured to calibrate the powder mass flow sensor14as a function of data/signals from the scales18and/or a specified powder mass flow. The scales18may be configured, for example, to measure a powder mass flow by measuring a powder mass deposited on the scales18in a time interval. The powder mass flow is then obtained by dividing the measured powder mass by the length of the time interval.

In this embodiment, the control unit is configured to control the process head. The process head may be configured to be moved in one, two or three directions. In some embodiments, the process head may comprise a laser unit configured to introduce a predetermined energy into a laser processing area during powder cladding.

In some embodiments, the control unit is configured to direct the powder mass flow from the at least one powder metering device11a,11bvia the powder mass flow sensors14to the scales by means of the powder switch in a work preparation mode. The powder mass is separated from gases and gas mixtures in the optional powder mass separator mounted upstream of the scale. In this embodiment, the control unit is configured to regulate and control the at least one powder metering device11a,11bin such a way that a specified powder mass flow is measured by means of the scale18. If the at least one powder metering device is adjusted accordingly, the powder mass flow sensor14can be calibrated. The powder mass flow sensor can, for example, be configured optically, by means of radiation or by contact to detect a powder mass flow. In some embodiments, the sensor data of the powder mass flow sensor are simply adjusted according to a calibration.

After the calibration of the powder mass flow sensor, powder cladding may be carried out in this embodiment. In this embodiment, in order to switch to the work mode, i.e. powder cladding, the powder switch15is actuated via a control signal so that the powder mass flow is fed to the process head16instead of to the scales. This makes it possible to switch from a work preparation mode to the work mode without interrupting the powder mass feed.

During powder cladding, the powder mass flow is monitored using the powder mass flow sensor. This ensures a constant powder mass flow.

In some embodiments, the control unit may be configured to interrupt or abort the powder cladding when a deviation of the powder mass flow detected by the powder mass flow sensor from a specified powder mass flow exceeds a specified limit value. For this purpose, the powder switch15may be actuated by the control unit20so that the powder mass flow is fed from the powder switch15to the scales18. Then the powder mass flow may be adjusted again using the scales and the powder mass flow sensor may be calibrated if necessary.

In some embodiments, the control unit may be configured to interrupt or abort the powder cladding based on an external signal, for example a sensor signal from a sensor for checking the powder mass deposition. In some versions, this may mean that there is a change from the work mode to the work preparation mode or that the powder cladding is aborted.

FIG.2schematically shows a process flow chart of a method according to an embodiment of the invention. In a first step S11, a powder mass is fed. The powder mass is preferably suitable as a powder for powder cladding. In a second step S12, a powder mass flow of the fed powder mass is determined. In a next step S13, depending on the determined powder mass flow, it is checked whether the powder mass flow deviates from a specified powder mass flow by more than a specified tolerance. If the deviation is greater than the tolerance, the feed of the powder mass is adjusted via step S14and the powder mass flow is determined again in step S12. If the deviation is less than the tolerance, a powder mass flow sensor is calibrated in step S15using the determined powder mass flow.

On the basis of the preparations for the powder cladding in steps S11to S15, the powder cladding can be carried out in a step S16. In order to switch from the steps of preparation to carrying out the powder cladding S16, for example, a powder switch may be actuated to change the feeding direction to a process head of a powder cladding unit instead of to a determination unit for determining the powder mass flow, see step S12.

During powder cladding S16, the powder mass flow is monitored using the powder mass flow sensor in steps S16a, S17-S19. In step S16athe powder mass flow is detected by means of the powder mass flow sensor. In step S17, it is checked whether a deviation of the powder mass flow detected by means of the powder mass flow sensor from a specified powder mass flow is greater than a specified tolerance value. If the deviation is greater, the powder cladding is interrupted and the process continues with step S12of determining the powder mass flow. Depending on the embodiment, when steps S12to S16are carried out again, step S15of calibrating the powder mass flow sensor may be skipped.

If the deviation of the detected powder mass flow from the specified powder mass flow is within the tolerance range, it is checked in step S18whether the detected powder mass flow corresponds to the specified value. If the detected powder mass flow corresponds to the specified powder mass flow, the execution of the powder cladding is continued with step S16. If the values do not match, the feed of the powder mass is adjusted in step S19and the procedure also continues with step S16of carrying out the powder cladding.

In some embodiments, step S16of carrying out the powder cladding can be continued after step S18if a deviation of the detected powder mass flow from the specified powder mass flow is below a further tolerance value. Otherwise, the procedure continues with step S19of adjusting the feed of the powder mass. In some embodiments, the tolerance values of step S17and step S18may have the same value.

In some embodiments, steps S16, S16a, S17-S19, which include monitoring the powder mass flow during powder cladding with the powder mass flow sensor, among others, may be performed in a different order, with additional steps, may at least be partially combined, etc.

FIG.3schematically shows a process flow chart of a method for measuring/determining the powder mass flow according to an embodiment of the invention. Upon the start S21of the method, a powder mass flow list is generated in a step S22by means of a conveyor disk speed n. In this embodiment, the powder metering device is a conveyor disk. In this embodiment, a specified powder mass flow isollis transferred in parallel. After the start of the method, the measurement cycle S24begins.

Depending on whether the cycle has just started, including the powder switch to the scale being actuated, step S26or step S25is performed. If the cycle has started from a standstill, the settling of the powder conveyor/powder metering device, in this exemplary embodiment 60 seconds, is waited for in step S26. When the powder switch to the scales is actuated, the passage of a settling time of the powder switch, 30 seconds in this exemplary embodiment, is waited for in step S25. Steps S25and S26may be skipped when neither the powder switch has been actuated nor the powder feeder has been activated from standstill.

In a next step S27, a first measurement of a powder mass m0is carried out on scales. In a further step S28, the passage of a time interval/measurement duration T, 30 seconds in this exemplary embodiment, is waited for. During the time interval/measuring period T, the powder mass flow is fed onto the scale. A second measurement of the powder mass m1is then carried out in step S29. In the next step S30, the powder mass flow is determined using the equation iist=(m1−m0)/T.

In a further step S31, a deviation of the powder mass flow isollfrom the specified powder mass flow is determined. In this exemplary embodiment, the deviation is determined using the formula |isoll−iist|/isoll. If the deviation is below a specified tolerance, 1% in this exemplary embodiment, the conveyor disk speed nerffor feeding the specified powder mass flow isollis specified with the conveyor disk speed n and the measurement/determination of the powder mass flow i can be completed in step S33.

If the deviation is greater than the specified tolerance, the speed of the conveyor disk n is adjusted in step S34. Depending on the embodiment, the passage of a reaction time of the powder metering device, in this exemplary embodiment 20 seconds, may be waited for in a step S35before the cycle starts again with step S24.

FIG.4schematically shows a device for measuring a powder mass flow for powder cladding according to an embodiment of the invention. In this embodiment, pinch valves11a,11bmeter the powder fed by powder conveyors41a,41b. The resulting powder streams are combined into one stream by means of the Y-connection13. In this exemplary embodiment, the pinch valves are controlled via the directional valve for driving one or more metering devices. The powder mass flow is fed from the Y-connection13to the powder switch15via the powder mass flow sensor14

As shown in this embodiment, the powder switch15may be controlled by means of the directional valve for driving the powder switch43. A possible position is that the powder mass flow is fed to the process head16via the powder transport16a. In a further possible position, the powder mass flow is fed onto a scale18. A powder separator17may be arranged on the feeding path between the scales18and the powder switch15. In some embodiments, the directional valve for driving one or more metering devices42, the directional valve for controlling the powder switch, the scale18, the mass flow sensor14, the powder separator and/or the process head may be connected to one another, for example, via one or more control units.

The control unit may be configured, for example, to control/regulate the powder mass flow using the directional valve for driving one or more metering devices42based on data/signals provided by the powder mass flow sensor14and/or the scales18. In some embodiments, the control unit may be configured to control the powder switch by means of the directional valve for driving the powder switch and thus to switch between a work preparation mode and a work mode of powder cladding.

In the work preparation mode, a predetermined powder mass flow may be adjusted by means of the scales18, the directional valve for driving one or more metering devices42and one or more metering devices11a,11b. The powder mass flow sensor14may preferably be calibrated after the powder mass flow has been adjusted. In order to then switch to the work mode without interruption, the powder mass flow can be fed to the process head16by actuating the directional valve for driving the powder switch43. While the powder is being fed to the process head16, the powder mass flow that is being fed may be monitored by means of the powder mass flow sensor14.

In some embodiments, the control unit may be configured to automatically switch to the work preparation mode and adjust the powder mass flow again when the powder mass flow sensor14detects an excessive deviation from a specified value. This has the advantage that when, for example, powder from a first batch runs out during powder cladding and powder from a second batch is fed, it is ensured that the powder mass flow corresponds to a target value.

LIST OF REFERENCE SYMBOLS

11a,11bpowder metering device13Y-connection14powder mass flow sensor15powder switch16process head16apowder transport to the process head1617powder separator18scales20control unit41a,41bpowder conveyor42directional valve for driving one or more metering devices43directional valve for driving the powder switchiistmeasured/detected powder mass flowisollspecified powder mass flowT time interval/measurement durationm0first weight measurementm1second weight measurementn speed of the conveyor discnerfconveyor disk speed for feeding isoll