WO2023020659A1

WO2023020659A1 - Powder feed device for a coating apparatus

Info

Publication number: WO2023020659A1
Application number: PCT/DE2022/100605
Authority: WO
Inventors: Tobias Phillip Utsch
Original assignee: HPL Technologies GmbH
Priority date: 2021-08-16
Filing date: 2022-08-16
Publication date: 2023-02-23
Also published as: DE102021208971A1

Abstract

The invention relates to a powder feed device (1) for a coating apparatus (2), comprising at least the following components: - at least one supply source (3, 4) for a powder (5, 6); - at least one feed line (7, 8, 9) for each one of the supply sources (3, 4) to a coating nozzle (10); and - at least one flow measuring device (11) for determining a current total flow rate (12) of the powder (5, 6) in the at least one feed line (9). The powder feed device (1) is characterised in particular in that at least one of the feed lines (9) comprises a bypass line (13) and the flow measuring device (11) is designed to detect a current partial flow rate (14) of the powder (5, 6) flowing through the bypass line (13). The flow measuring device disclosed here on a bypass line of the powder feed device enables highly precise monitoring of the flow of the powder.

Description

Powder supply device for a coating device

The invention relates to a powder feed device for a coating device, a measuring method with such a powder feed device for determining a current total flow rate of the powder, and a coating device with such a powder feed device for a workpiece.

It is known from the prior art that workpieces have a carrier body which is coated with a powder. Processes for this are, for example, powder spraying, laser powder welding, high-velocity flame spraying [HVOF; English: High Velocity Oxygen Fuel] or extremely high-speed laser cladding [EHLA], these processes have in common that a material to be applied must be provided in the form of a powder. To reliably maintain process parameters, it is important to know the flow rate of the powder as precisely as possible. There are various methods for this, the previously known ones either not being sufficiently accurate or not suitable for large flow rates.

Proceeding from this, the object of the present invention is to at least partially overcome the disadvantages known from the prior art. The features according to the invention result from the independent claims, for which advantageous configurations are shown in the dependent claims. The features of the claims can be combined in any technically meaningful way, whereby the explanations from the following description and features from the figures can also be used for this purpose, which include additional configurations of the invention.

The invention relates to a powder feed device for a coating device, having at least the following components:

- at least one supply source for a powder;

- at least one supply line for each one of the supply sources to a coating nozzle; and - at least one flow measuring device for determining a current total flow rate of the powder in the at least one feed line.

The powder feed device is primarily characterized in that at least one of the feed lines includes a bypass line and the flow measuring device is set up to detect a current partial flow rate of the powder flowing through the bypass line.

Unless explicitly stated otherwise, ordinal numbers used in the description above and below only serve to clearly distinguish them and do not reflect any order or ranking of the components referred to. An ordinal number greater than one does not mean that another such component must necessarily be present.

The powder supply device proposed here comprises at least one storage source, for example a receiving container for a powder or a mixture of a powder or a line which is connected to an external storage container. The powder is, for example, partly metallic and partly an additive, for example carbides or other hard materials, which are used in a friction coating of a brake disc. The supply line is connected to a respective supply source or a common line for several supply sources. In the case of a plurality of storage sources, the types of powder are already mixed before they reach the coating (and fed through a common feed line) or mixed with one another only during coating (and fed through separate powder nozzles).

It is now proposed here that the flow measuring device is arranged in a bypass line and thus only a partial flow rate of the relevant supply line on which the bypass line is formed can be detected by the flow measuring device by means of the flow measuring device. The current partial flow rate together with a current main flow rate in the main line of the supply line in question forms the current total flow rate of the supply line. For example, equals the sum of the hydraulic diameters of the bypass line and the main line the hydraulic diameter of the supply line in question.

The supply line to which the bypass line is connected is set up in such a way that a relationship between the portion that flows through the bypass line and the portion that flows through the main line is known (for example empirically). In a preferred embodiment, there is a proportional relationship between the partial flow rate through the bypass line and the (main) flow rate, which together form the total flow rate.

Due to the reduction in the cross section of such a bypass line compared to the feed line in question (or to an upstream or downstream feed line), which is set up for a total flow rate of the powder, a very precisely measuring flow measuring device can be used. The accuracy of this flow measurement on the bypass line is so precise that any inaccuracies in the ratio between the partial flow rate and the (main) flow rate (of the remainder or main portion outside the bypass line) can be more than compensated.

It is further proposed in an advantageous embodiment of the powder supply device that the bypass line is set up for conducting a fixed proportion of the current total flow rate of the powder, the fixed proportion being set up in a range from 5% by volume to 30% by volume.

Here it is suggested that the proportion of the partial flow rate in the actual total flow rate is fixed, in a range of 1 vol%

[one percent by volume] to 30% by volume, preferably 5% by volume. Thus, only the detected partial flow rate has to be divided by this fixed ratio in order to obtain a very exact value for the current total flow rate. For a reliable flow ratio between the main flow rate and the partial flow rate, a flow-optimal diversion (e.g. by means of a sharp-edged division and a gentle Inclination angle) provided for a (quasi) laminar flow of powder particles. For example, the hydraulic diameter of the bypass line in relation to the main line corresponds to the fixed proportion that is aimed for, i.e. the hydraulic diameter of the bypass line is 5% [five percent] of the hydraulic diameter of the entire line and in the main line it becomes 95 % [ninety-five percent] passed through. Alternatively, the flow velocities in the bypass line and the main line are different from one another.

In an advantageous embodiment of the powder supply device, it is also proposed that the flow measuring device includes a light sensor for detecting shadows of the powder flowing through the bypass line.

In this embodiment, a particularly precise sensor for a flow measurement is proposed, namely a light sensor, particularly preferably a laser light sensor, with so-called shadow detection of the powder flowing through being carried out in order to determine the number of powder particles flowing through the bypass line.

The bypass line makes it possible for almost any quantity (i.e. total flow rate) of a powder to be provided and at the same time such an exact light sensor or laser light sensor for which the hydraulic diameter is not too large for shadow detection or the number in the flow pattern is not too large of the powder particles arranged one behind the other in the measuring direction must not be too large. In addition, it is hereby possible to dispense with the use of a large number of individual sensors which detect shadows from different angles in order to carry out a correction from this measurement data. In the case of a particularly large flow rate and/or an even greater required accuracy of the detection of the current total flow rate, it is proposed to use a plurality of sensors for the flow measurement. In addition, it is proposed that the light beams of the light sensors are arranged as closely as possible one behind the other in the direction of flow. In a further embodiment it is proposed that (for example for plausibility check) in the Main line another sensor is arranged, which is part of the flow meter or another flow meter.

According to a further aspect, a measuring method for determining a current total flow rate of the powder in a powder feed device according to an embodiment according to the above description is proposed, comprising the following steps in the order mentioned: a. introducing a powder into the at least one feed line; b. diverting a fixed portion of the powder flowing through the feed line through the bypass line; c. detecting a current partial flow rate of the powder flowing through the bypass line; and d. Divide the in step c. detected current partial flow rate by the known proportion of the current total flow rate of the powder.

A measurement method for determining a current total flow rate of a powder in a powder feed device, as described above, is proposed here, with initially in a step a. the powder is introduced into the at least one feed line. In this case, the powder is usually carried by a transport gas, for example by air or by a (for example inert) process gas for a later thermal processing of the powder.

In step b. now the solid part of the powder fed in the feed line is fed into the bypass line. It should be noted that steps a. and b. are passive steps which result from the construction or the flow profile of the supply line and the bypass line.

In step c. the partial flow rate, i.e. the flow rate that is present in the bypass line, is now recorded by one of the measuring devices. Subsequently, in a step d. this detected (partial) flow rate in the bypass line by the known proportion of the partial flow rate from the total flow rate (e.g. the ratio of the hydraulic diameter of the bypass line to the hydraulic diameter of the supply line before the bypass line and/or after the bypass line) divided and thus the current total flow rate is determined. This calculation step takes place in the measuring device or in an external computing unit, with the result of this calculation preferably being used to control or regulate the supply of powder and/or the speed of a carrier gas. This is carried out, for example, via at least one closing valve and/or throttle valve (preferably directly controllable by a control unit).

According to a further aspect, a coating device for a workpiece is proposed, having at least the following components:

- a powder feeder according to an embodiment as described above;

- a coating nozzle supplied by the feed line of the powder feed device for feeding powder into a focus;

- An infeed device for moving the focus of the coating nozzle in a defined manner; and

- a high-temperature source for melting the powder fed into the focus by means of the coating nozzle and/or from a region near the focus of a treatment surface of a workpiece to be coated, with the coating device preferably being set up for extremely high-speed laser deposition welding.

A coating device for a workpiece is now proposed here, which includes the powder supply device described above and is preferably set up to carry out the measuring method described above for detecting a total flow rate of the powder. In one embodiment, the coating device is formed separately with such a powder feed device. At least the coating device is connected to the powder supply device during operation in such a way that its coating nozzle can be supplied with the desired powder. The coating nozzle is, for example, a correspondingly designed opening at the end of a feed line, which is aligned in such a way that the powder can be fed into a focus. In a preferred embodiment, the coating nozzle is an annular nozzle in which the powder is fed to the focus in a conical shape. The coating device also comprises a high-temperature source, for example a torch (in the case of high-velocity oxygen fuel [HVOF]) or a laser (in the case of laser cladding, preferably extremely high-velocity laser cladding [EHLA]).

The high-temperature source is set up in such a way that the powder in the focus and/or in an area around the focus can be melted or melted, so that the powder is partially melted (i.e. with a melted surface) or completely melted and hits the desired treatment surface of the workpiece. In one embodiment, the high-temperature source is set up in such a way that in a region near the focus, i.e. usually along the axis of the high-temperature source behind the focus of the supplied powder, the treatment surface of the workpiece is melted (i.e. a melt pool is formed) so that the powder is absorbed into the treatment surface. In a particularly preferred embodiment, the powder is melted or melted and a molten pool is generated in the region near the focus in the treatment surface of the workpiece to be coated.

It should be noted that in some powder compositions, certain particles (for example hard materials) have such a high melting point that they do not melt or even do not melt and only in the melt of the other powder particles (for example made of stainless steel) or alone in the melt are embedded in the treatment surface and are thus permanently connected to the workpiece.

For example, in EHLA, the region is round, ranging in diameter from 2 mm [two millimeters] to 3 mm. In this embodiment, the focus is also round, for example, with a diameter of 1.5 mm [one and a half millimeters] to 2 mm.

The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention will not limited in any way by the purely schematic drawings, it being noted that the drawings are not to scale and are not suitable for defining proportions. It is presented in

1: a powder supply device with a coating device;

2: a mass flow-time diagram; and

3: a flowchart of a measurement method.

1 shows a schematic view of a powder supply device 1 with a coating device 2 . The powder supply device 1 shown here includes (here two) supply sources 3.4, for example two receptacles for two powders 5.6. The powder 5.6 is, for example, partly metallic and partly an additive, for example carbides or other hard materials, which are used in a friction coating of a brake disc. A first supply line 7 is connected to a first supply source 3 and a second supply line 8 to a second supply source 4 and open into a common supply line 9. The powders 5, 6 are preferably already mixed before they reach the coating.

It is now shown here that the flow measuring device 11 is arranged on a bypass line 13 and thus, by means of the flow measuring device 11, only a partial flow rate 14 of the relevant supply line 9 or the main line 22, on which the bypass line 13 is formed, from the flow measuring device 11 can be detected by a light sensor 15 .

The feed line 9 ends at a coating nozzle 10 (here an annular nozzle), which is encompassed by a coating device 2 . The coating nozzle 10 is aligned in such a way that the powder 5, 6 can be fed into a focus 17 and the focus 17 can be moved in a defined manner by means of an infeed device 18 (only indicated here schematically for a single feed direction in the image plane from right to left). The coating device 2 also includes a high-temperature source 19, here for example a laser for laser deposition welding, preferably for extremely high-speed laser deposition welding [EHLA],

The high-temperature source 19 is set up in such a way that the powder 5.6 (here from the laser) can be melted or melted in the focus 17, so that the powder 5.6 (preferably in a melt bath) in the region 20 (as shown) below the Focus 17 impinges in the treatment surface 21 and thus (after curing) a finishing layer 23 is formed on the workpiece 16.

A mass flow-time diagram is shown in FIG. The ordinate is the mass flow axis 24 and the time axis 25 is plotted on the abscissa. A measurement curve of a previously known measurement method (dashed line, conventionally recorded flow rate 26) and a measurement curve based on the recorded partial flow rate 14 calculated according to the measurement method proposed here (solid line) are shown in comparison here. Below the two overlapping curves, the (detected) partial flow rate 14 is shown in broken lines.

The conventionally recorded flow rate 26 shown in dashed lines represents the result from the (conventional) recording of the total flow rate 12 itself. The measurement curve shown as a solid line represents the result from the recording of the partial flow rate 14 over time of the powder feed device 1 (compare Fig. 1). , where the total flow rate 12 shown has been calculated. The partial flow rate 14 corresponds, for example, to a fixed proportion of 5% by volume [five percent by volume] of the total flow rate 12 and the total flow rate 12 is calculated by taking the measured value of

Partial flow rate 14 is divided by this fixed proportion of 5% by volume.

Due to the reduction in the hydraulic diameter of such a bypass line 13 compared to the main line 22 or the entire line, a very precisely measuring flow rate measuring device 11 can be used. The measurement accuracy of this flow measurement on the bypass line 13 is included so precisely that any inaccuracies in the ratio between the partial flow rate 14 and the (main) flow rate (of the remainder outside the bypass line 13) can be more than compensated for. This can be clearly seen in the comparison of the conventionally recorded flow rate 26 shown as a dashed line and the total flow rate 12 shown as a solid line over time, with flow rate peaks only being visible in the solid line and not being recorded in the dashed measurement curve.

FIG. 3 shows a flow chart of a measurement method, the measurement method for determining a current total flow rate 12 of a powder 5 , 6 in a powder feed device 1 (compare FIG. 1 ) being proposed. First, in a step a. the powder 5.6 introduced into the at least one supply line 7.8. In step b. the solid part of the powder 5.6 guided in the supply line 7.8 is now introduced into the bypass line 13. In the step c. the partial flow rate 14, ie that flow rate which is present in the bypass line 13, is now detected by one of the measuring devices. Subsequently, in a step d. this recorded (partial) flow rate in the bypass line 13 is divided by the known proportion of the partial flow rate 14 to form the total flow rate 12 (see above) and the current total flow rate 12 is thus determined.

With the flow measuring device proposed here on a bypass line of the powder supply device, a high-precision monitoring of the flow of the powder is made possible.

Reference character list

powder feed device

Coating device first supply source second supply source first powder second powder first supply line second supply line third supply line

coating die

flow meter

total flow rate

bypass line

partial flow rate

light sensor

workpiece

focus

delivery device

high temperature source

region

treatment surface

main line

finishing layer

mass flow axis

Timeline conventionally-detected flow rate

Claims

Powder supply device (1) for a coating device (2), having at least the following components:

- At least one storage source (3.4) for a powder (5.6);

- At least one supply line (7,8,9) for one of the supply sources (3,4) to a coating nozzle (10); and

- at least one flow measuring device (11) for determining a current total flow rate (12) of the powder (5,6) in the at least one supply line (9), characterized in that at least one of the supply lines (9) has a bypass line (13) and the flow measuring device (11) is set up to detect a current partial flow rate (14) of the powder (5, 6) flowing through the bypass line (13). Powder supply device (1) according to claim 1, wherein the bypass line (13) is set up for conducting a fixed proportion of the current total flow rate (12) of the powder (5,6), the fixed proportion being in a range of 5% by volume to 30% by volume is established. Powder supply device (1) according to Claim 1 or Claim 2, in which the flow measuring device (11) comprises a light sensor (15) for detecting the shadow of the powder (5, 6) flowing through the bypass line (13). Measuring method for determining a current total flow rate (12) of the powder (5,6) in a powder feed device (1) according to one of the preceding claims, having the following steps in the order mentioned: a. Introducing a powder (5.6) into the at least one feed line (9); b. branching off a fixed portion of the powder flowing through the feed line (9) through the bypass line (13); c. Capture a current partial flow rate (14) from which the ByPass Powder (5,6) flowing through line (13); and d. Divide the in step c. detected current partial flow rate (14) by the known proportion of the current total flow rate (12) of the powder (5.6). 5. Coating device (2) for a workpiece (16), having at least the following components:

- A powder supply device (1) according to any one of claim 1 to claim 3;

- A coating nozzle (10) supplied by the supply line (7,8,9) of the powder supply device (1) for supplying powder (5,6) into a focus (17); - An infeed device (18) for defined movement of the focus (17).

coating nozzle (10); and

- a high-temperature source (19) for melting the powder (5, 6) fed into the focus (17) by means of the coating nozzle (10) and/or from a region (20) in the vicinity of the focus (17) of a treatment surface (21 ) a workpiece (16) to be coated, the coating device (2) preferably being set up for extremely high-speed laser deposition welding.