EP3957404A1 - Application system for coating components and coating device - Google Patents

Abstract

The invention describes a coating device for coating components with a coating agent, with an application system which includes the following assemblies:
- an application device which applies the coating agent, the application device being a print head (1) which ejects the coating agent from a plurality of coating agent nozzles (2, 19), a nozzle valve (20) being fitted to each individual coating agent nozzle (2) and opens for a valve opening time when a drop of coating agent is to leave the respective nozzle (2),
- a coating medium supply line (22) to which the coating medium nozzles (19) of the print head (1) are jointly connected,
- a valve controller (25) for controlling the valve opening times and valve closing times of each individual valve (20),
wherein the coating device comprises a robot on which at least the application device is accommodated
characterized in that the application system further comprises a pump (21) by means of which the coating agent to be applied is fed to the coating agent nozzles (19) via the coating agent feed line (22), and in that the application system is set up such that the pump (21) during the coating operates with a constant flow rate of the coating agent, and that the pressure at each nozzle (19) when the valve (20) opens is the same as when this valve (20) was previously opened.

Description

The invention relates to an application system for coating components according to the preamble of claim 1 and a coating device according to the preamble of claim 2.

• ein Applikationsgerät, das das Beschichtungsmittel appliziert, wobei das Applikationsgerät ein Druckkopf ist, der das Beschichtungsmittel aus mehreren Beschichtungsmitteldüsen ausstößt, wobei an jeder einzelnen Beschichtungsmitteldüse ein Düsenventil angebracht ist, das sich eine Ventilöffnungszeit lang öffnet, wenn ein Beschichtungsmitteltropfen die jeweilige Düse verlassen soll,
• eine Beschichtungsmittelzuleitung, mit der die Beschichtungsmitteldüsen des Druckkopfes gemeinsam verbunden sind,
• eine Ventilsteuerung zur Steuerung der Ventilöffnungszeiten und Ventilschließzeiten jedes einzelnen Ventil.

Such an application system includes the following assemblies:

• an application device that applies the coating agent, wherein the application device is a print head that ejects the coating agent from a plurality of coating agent nozzles, with each individual coating agent nozzle having a nozzle valve attached which opens for a valve opening time when a drop of coating agent is to leave the respective nozzle,
• a coating agent supply line to which the coating agent nozzles of the print head are jointly connected,
• a valve controller for controlling the valve opening times and valve closing times of each individual valve.

A coating device includes a robot on which at least the application device is accommodated. The application device is usually attached to the robot at the so-called tool center point, or TCP for short.

the DE 10 2008 053 178 A1 shows a coating device for coating, in particular painting, of motor vehicle body components. In such a painting installation for painting motor vehicle body components, the motor vehicle body components to be painted are transported on one through a painting booth, in which the motor vehicle body components are then painted by painting robots. The painting robots have one or more swiveling robot arms and each have an application device on their TCP via a multi-axis robot hand axis. The application device is designed here as a print head that ejects the coating agent from several coating agent nozzles, and the coating agent nozzles of the print head are jointly connected to a coating agent supply line, via which the coating agent to be applied is supplied. Painting by means of such a print head is advantageous if, for example, a vehicle body is to be painted in multiple colors, if different colors are to be applied at different points on the body. Painting with a print head applicator enables sharp-edged painting of different zones on the workpiece, e.g. the body, without further additional precautions, in particular without masking off areas of a different color.

When painting with a print head applicator, the coating material is usually metered by means of a pressure regulator for the coating material. This dosing by means of a pressure regulator has a number of disadvantages, in particular when painting automobile bodies or body parts in an automobile painting line. Namely, the flow rate of a paint used as a coating material in automotive painting depends on viscosity and pressure. The viscosity of the coating material can differ greatly with different paint materials. Some paint materials used are thixotropic, which means they have a pressure-dependent viscosity. This significant dependency of the viscosity of the coating agent on the type of material and the pressure often leads to non-uniform droplet sizes during coating and thus to great difficulties in ensuring a homogeneous coating.

It is therefore the object on which the present invention is based to improve an application system of the type mentioned at the outset in such a way that a constant droplet size over time is ensured during the coating process.

Furthermore, it is an object of the present invention to further improve a coating device.

With regard to the application system, this object is achieved with an application system having the features of claim 1. With regard to the coating device, the object is achieved with a coating device having the features of claim 4.

According to the invention, the application system further comprises a pump, by means of which the coating agent to be applied is fed to the coating agent nozzles via the coating agent supply line, and the application system is set up in such a way that the pump operates with a constant flow rate of coating agent during coating, and that the pressure at each nozzle when the valve is opened is the same as when that valve was previously opened.

According to the invention, the application system has a coating medium return line in which a return valve is installed, which opens at least when the nozzle valves of the print head are closed at the same time.

Alternatively, the valve control is set up so that a constant number of nozzle valves of a print head are always open during coating.

The invention and further embodiments and further advantages of the invention will now be explained and described in connection with the following description of the figures.

Figur 1

schematisch und exemplarisch einen Druckkopf zur Verwendung in einem erfindungsgemäßen Applikationsgerät, mit hier exemplarisch dargestellten zehn Beschichtungsmitteldüsen, angeordnet in einer Linie hintereinander, wobei die Linie sich in etwa senkrecht zur Bewegungsrichtung des Applikationsgerätes beim Beschichten erstreckt,

Figur 2

schematisch und exemplarisch einen Druckkopf mit zweiunddreißig Beschichtungsmitteldüsen, wobei an jeder Beschichtungsmitteldüse ein Ventil angebracht ist, und die Beschichtungsmitteldüsen gemeinsam mit einer Beschichtungsmittelzuleitung verbunden sind, in zwei Ausführungsformen: links mit Beschichtungsmittelzuführung von einer Seite, rechts mit Beschichtungsmittelzuführung von zwei Seiten,

Figur 3

schematisch und exemplarisch eine Ausführungsform eines Applikationssystems, bei dem drei Druckköpfe mit jeweils zweiunddreißig Beschichtungsmitteldüsen aneinandergereiht sind, um die Beschichtungsleistung zu erhöhen, und bei dem die Beschichtungsmitteldüsen in benachbarten Druckköpfen gegeneinander versetzt sind,

Figur 4

schematische Veranschaulichung eines Betriebsmodus der Beschichtungsmitteldüsen eines Druckkopfes, gemäß dem Stand der Technik,

Figur 5a

schematisch und exemplarisch ein Applikationssystem mit einem Drucckopf, der zweiunddreißig Beschichtungsmitteldüsen hat, wobei an jeder Beschichtungsmitteldüse ein Ventil angebracht und dieser zugeordnet ist;

Figur 5b

den zeitlichen Verlauf der Ventilstellung während zweier vollständiger Schaltperioden T1 und T2 sowie einer halben Schaltperiode T3,

Figur 5c

den zeitlichen Verlauf des Beschichtungsmittelflusses an der Düsenaustrittsöffnung einer Beschichtungsmitteldüse (durchgezogene Linie), und der von der Pumpe eingeprägten Durchflussrate des Beschichtungsmittels (gestrichelte Linie)

Figur 5d

den zeitlichen Verlauf des Druckes an der Beschichtungsmitteldüse des Druckkopfes,

Figur 6a

eine Ausführungsform entsprechend der in Figur 5a dargestellten, bei der zusätzlich eine Beschichtungsmittel-Rückleitung vorhanden ist, in der ein Rückführventil eingebaut ist.

Figur 6b

die Schaltzustände der Düsenventile gemäß Figur 6a während zweier vollständiger Schaltperioden T1 und T2 sowie einer halben Schaltperiode T3,

Figur 6c

den zu den Schaltzuständen der Düsenventile nach Figur 6b korrespondierenden Schaltzustand des Rückführventils, während zweier vollständiger Schaltperioden T1 und T2 sowie einer halben Schaltperiode T3.

Figur 7

wie durch die erfindungsgemäßen Maßnahmen der nachteilige Aufbau eines immer weiter ansteigenden Überdrucks im System mit den negativen Auswirkungen hinsichtlich einer nicht-uniformen Tropfengröße vermieden ist,

Figur 8a

schematisch und exemplarisch ein Applikationssystem mit einem Drucckopf, der zweiunddreißig Beschichtungsmitteldüsen hat, wobei an jeder Beschichtungsmitteldüse ein Ventil angebracht und dieser zugeordnet ist.

Figur 8b

schematisch und exemplarisch den Betriebsmodus der Beschichtungsmitteldüsen des Druckkopfes aus Figur 8a mit den zweiunddreißig Beschichtungsmitteldüsen 1 - 32,

Figur 9

einen beispielhaften Betriebsmodus für ein Applikationssystem mit drei Druckköpfen, von denen jeder zweiunddreißig Ventile hat.

Show it:

figure 1

schematically and by way of example, a print head for use in an application device according to the invention, with ten coating agent nozzles shown here as an example, arranged in a line one behind the other, the line extending approximately perpendicular to the direction of movement of the application device during coating,

figure 2

schematically and by way of example a print head with thirty-two coating agent nozzles, a valve being attached to each coating agent nozzle and the coating agent nozzles being jointly connected to a coating agent feed line, in two embodiments: on the left with coating agent feed from one side, on the right with coating agent feed from two sides,

figure 3

a schematic and exemplary embodiment of an application system in which three print heads, each with thirty-two coating agent nozzles, are lined up in order to increase the coating output, and in which the coating agent nozzles in adjacent print heads are offset from one another,

figure 4

schematic illustration of an operating mode of the coating agent nozzles of a print head, according to the prior art,

Figure 5a

schematic and exemplary an application system with a print head, having thirty-two coating agent nozzles, each coating agent nozzle having a valve attached to and associated with it;

Figure 5b

the time profile of the valve position during two complete switching periods T1 and T2 and half a switching period T3,

Figure 5c

the course over time of the coating agent flow at the nozzle outlet opening of a coating agent nozzle (solid line), and the flow rate of the coating agent impressed by the pump (dashed line)

Figure 5d

the time course of the pressure at the coating agent nozzle of the print head,

Figure 6a

an embodiment according to in Figure 5a shown, in which there is also a coating agent return line in which a return valve is installed.

Figure 6b

the switching states of the nozzle valves according to Figure 6a during two complete switching periods T1 and T2 and half a switching period T3,

Figure 6c

to the switching states of the nozzle valves Figure 6b corresponding switching state of the recirculation valve, during two complete switching periods T1 and T2 and half a switching period T3.

figure 7

how the disadvantageous build-up of an ever-increasing overpressure in the system with the negative effects in terms of a non-uniform droplet size is avoided by the measures according to the invention,

Figure 8a

schematically and by way of example, an application system with a print head that has thirty-two coating agent nozzles, with a valve being attached to and associated with each coating agent nozzle.

Figure 8b

shows the operating mode of the coating agent nozzles of the print head schematically and as an example Figure 8a with the thirty-two coating agent nozzles 1 - 32,

figure 9

shows an example mode of operation for an application system with three printheads, each having thirty-two valves.

figure 1 shows schematically and by way of example a print head 1 for use in an application device according to the invention. The print head 1 is shown here schematically and by way of example as a cuboid structure. In this example, it has ten coating agent nozzles 2, which are arranged in a line one behind the other on a narrow side of the print head, the line extending approximately perpendicular to the direction of movement of the application device during coating, see here figure 3 . The arrow D indicates the direction of ejection of the coating agent droplets.

figure 2 shows a schematic and exemplary print head 3 with thirty-two coating agent nozzles 4, which are essentially identical in construction to the coating agent nozzles 2 according to FIG figure 1 embodiment shown. A valve 5 is attached to each coating agent nozzle 4 and the coating agent nozzles 4 are connected in common to a coating agent supply line 6 . The valves can be switched with a switching frequency in the range of a few kHz, typically in the range of 3 kHz. left in figure 2 an embodiment is shown in which the coating agent is only supplied from one side, here from above. Right in the figure 2 an embodiment is shown in which the coating agent is supplied from two sides, here from above and below, with the coating agent supply line 6 dividing into an upper and a lower partial arm 7, 8 for this purpose.

figure 3 shows a schematic and exemplary embodiment of an application system 9 in which three print heads 10, 11, 12, each with thirty-two coating agent nozzles 13, are lined up in order to increase the coating performance. The direction of movement of the application system 9 during coating is indicated by the arrow P; it can be seen that this runs approximately perpendicular to the line in which the coating agent nozzles 13 in each of the three print heads 10, 11, 12 are arranged. The distance between adjacent coating agent nozzles 13 is denoted by a. This distance cannot be made arbitrarily small for structural reasons. In order to achieve a uniform application of the coating agent, the coating agent nozzles 13 of the three print heads 10, 11, 12 lined up are offset from one another by an amount of a/3, as in the right-hand part of FIG figure 3 illustrated detail enlargement of a portion 14 of the coating agent nozzle field is shown.

figure 4 12 shows, schematically and by way of example, the operating mode 16 of the coating agent nozzles of a print head, as is customarily used in accordance with the prior art. A print head 15 with six operating fluid nozzles D1-D6 is assumed here for the exemplary explanation. The horizontal bars, with the alternating black and white fields, indicate the switching status of the respective valves when the print head 15 is moved for coating. A dark field indicates that the corresponding valve is open during this time. During this time, a drop of coating agent emerges from the respective nozzle. A bright field indicates that the corresponding valve is closed during this time, during this time no drop of coating agent exits through the corresponding nozzle. In the usual operating mode 16, as illustrated in FIG. 4, all the valves are opened and closed simultaneously. This is often done to get a sharp start and finish line of the coating. In the figure 4 a total of eight switching periods T1 - T8 are shown lined up in their chronologically consecutive order.

figure 5 shows in partial figure 5a schematically and by way of example an application system 17 with a print head 18 which has thirty-two coating agent nozzles 19, a valve 20 being attached to each coating agent nozzle 19 and assigned to it. In the coating medium supply line 22 there is a pump 21 which pumps the coating medium through the coating medium supply line 22 to the print head 18 at a constant flow rate. The pump 21 can be designed, for example, as a gear pump or as a piston pump, both types of pumps that can generate a constant flow rate even with varying pressure. The sub-figures 5b -5d show the time curves of the valve position ( Figure 5b ), the flow of coating agent at the nozzle outlet opening of a coating agent nozzle ( Figure 5c , solid line), the flow rate of the coating agent impressed by the pump 21 ( Figure 5c , dashed line) and the pressure at the coating agent nozzle 19 of the print head 18 ( Figure 5d ) during two complete switching periods T1 and T2 and half a switching period T3. If the valves are all closed at the same time, for example in the switching period T1 at time A, the pump 21 continues to pump the coating agent into the application system 17 at a constant flow rate. The pressure in the application system and thus the pressure at the coating agent nozzle of the print head increases, it is created an overpressure in the application system, see Figure 5d , since the hoses and other components of the application system have a certain elasticity. If the valve is now opened again at the beginning of the following switching cycle, see for example time B at the beginning of switching cycle T2, the pressure drops again and after a short time the flow of coating agent at the outlet opening of the coating agent nozzle is constant.

In the present invention, it was surprisingly recognized that under certain circumstances, when the time constants of the application system are so great that the overpressure cannot be completely reduced by the start of the next following switching period, the overpressure then changes from a higher one during the next switching period Starting point further increased, and so on, so that the pressure in the application system continues to rise. Since the flow rate of the coating agent at the outlet nozzle of the print head depends not only on the viscosity but also on the pressure, this results in the surprisingly recognized problem that although the pump generates a constant flow rate, the flow rate at the outlet opening of the coating agent nozzle and thus the droplet size are not uniformly large is, but changes over time. This is disadvantageous with regard to an optimal coating result.

figure 6 shows a first solution to this surprisingly recognized problem. Partial figure 6a shows an embodiment corresponding to that in Figure 5a illustrated shown, in which a coating agent return line 23 is also present, in which a return valve 24 is installed. A valve controller 25 controls the nozzle valves 20 in the print head and the return valve 25. Figure 6b shows the switching states of the nozzle valves 20 and Figure 6c shows the corresponding switching state of the recirculation valve 24, in each case during two complete switching periods T1 and T2 and half a switching period T3. The recirculation valve 24 is open when the nozzle valves 20 are closed and closed when the nozzle valves 20 are open. When the nozzle valves 20 are closed, the pump 21 circulates the coating agent via the open recirculation valve 24 and the coating agent return line 23 . As a result, this measure ensures that the overpressure is now completely reduced by the beginning of the next switching period following the closing of all nozzle valves 20, so that the overpressure then increases again during the next switching period from the pressure level that was at the beginning of the previous one Opening of the nozzle valves 20 has prevailed, so that now the pressure in the application system does not continue to increase. As a result, the flow rate at the outlet opening of the coating agent nozzle and thus the droplet size are uniformly large and do not change over time. This is an advantage with regard to an optimal coating result.

A further possible solution consists in the valve control being set up such that a constant number of nozzle valves of a print head are always open during coating. figure 8 illustrates this solution by example and by way of example. Subfigure 8a shows, schematically and by way of example, an application system 17 with a print head 18 which has thirty-two coating agent nozzles 19, with a valve 20 being attached to each coating agent nozzle 19 and assigned to it. In the coating medium supply line 22 there is a pump 21 which pumps the coating medium through the coating medium supply line 22 to the print head 18 at a constant flow rate. The pump 21 can be designed, for example, as a gear pump or as a piston pump, both types of pumps that can generate a constant flow rate even with varying pressure.

Figure 8b 12 shows, schematically and by way of example, the operating mode 26 of the coating agent nozzles of the print head 18 Figure 8a with the thirty-two coating agent nozzles 1-32 according to the second inventive solution described here. The horizontal bars, with the alternating black and white fields, indicate the switching status of the respective valves when the print head 18 is moved for coating. A dark field indicates that the corresponding valve is open during this time, during which time a drop of coating agent emerges from the respective nozzle. A bright field indicates that the corresponding valve is closed during this time, during this time no drop of coating agent exits through the corresponding nozzle. The valve control ensures that the switching sequence of the valves 20 is set in such a way that a constant number of valves is always open. In Figure 8b ten consecutive switching periods A - J are shown. During the first part of the first switching period A, eight valves are open, Nos. 1, 2, 3, 4, 29, 30, 31, 32. The remaining twenty-four valves are closed when the eight valves Nos. 1, 2, 3 , 4, 29, 30, 31, 32 close, the eight valves No. 5, 6, 7, 8, 25, 26, 27, 28 open. At the end of the first switching period A and at the beginning of the second switching period B, the valves close Nos. 5, 6, 7, 8, 25, 26, 27, 28 again, valves Nos. 1, 2, 3, 4, 29, 30, 31, 32 remain closed, and the eight valves No. 9 open , 10, 11, 12, 21, 22, 23, 24. When these close again in the middle of the second switching period B, the eight valves 13, 14, 15, 16, 17, 18, 19, 20 open. The other valves remain open until the end of the second switching period B and the beginning of the third switching period C closed. After that, this pattern repeats itself. With this scheme, eight valves are always open and 24 valves are closed. The switching scheme ensures that each of the thirty-two valves has opened once within two switching periods. The pump always works with a constant flow rate of the coating agent. No increasing overpressure can build up in the system because eight valves are always open. With a typical valve opening time of 1 ms and an assumed, exemplary speed of 200mm/s of the robot arm during coating, the distance that the print head travels during two switching periods, until we open the same eight valves again at the beginning, is 0.8 mm. Next to the one in the figure 8 many more are conceivable. For example, not just eight, but also sixteen or just four valves could be open at the same time. Also, the distribution of the opened valves can vary along the line on which they are located. It is only important that the same number of valves is always open.

This in figure 8 The procedure shown using one printhead can also be transferred to an application system with multiple printheads. figure 9 1 shows this by way of example using an exemplary operating mode 27 for an application system with three print heads, each of which has thirty-two valves. Here, too, the horizontal bars with the alternating black or hatched and white fields show the switching status of the respective valves when the print head is moved for coating. A dark or hatched field indicates that the corresponding valve is open during this time, during which time a drop of coating agent emerges from the respective nozzle. A bright field indicates that the corresponding valve is closed during this time, during this time no drop of coating agent exits through the corresponding nozzle. The bars with the fields filled in black to indicate an open valve are assigned to the first print head. The bars with the obliquely hatched fields to indicate an open valve are associated with the second printhead. The bars with the vertically hatched fields to indicate an open valve are assigned to the third print head. Here, too, it is ensured that eight of the thirty-two valves are always open on each of the three print heads. There three If print heads are operated in parallel, coating medium is ejected from more than eight nozzles in each switching period, namely from sixteen or twenty-four coating medium nozzles, depending on the switching period. Even better layer homogeneity can be achieved in this way.

figure 7 shows how the disadvantageous build-up of an ever-increasing overpressure in the system with the negative effects in terms of a non-uniform droplet size is avoided by the measures according to the invention as described above. Partial figure 7a shows schematically and by way of example an application system 17 with a print head 18 which has thirty-two coating agent nozzles 19, a valve 20 being attached to each coating agent nozzle 19 and assigned to it. In the coating medium supply line 22 there is a pump 21 which pumps the coating medium through the coating medium supply line 22 to the print head 18 at a constant flow rate. The pump 21 can be designed, for example, as a gear pump or as a piston pump, both types of pumps that can generate a constant flow rate even with varying pressure. Not shown in Figure 7a the coating agent return line with the return valve. The partial figures 7b -7d show the time curves of the valve position ( Figure 7b ), the flow of coating agent at the nozzle outlet opening of a coating agent nozzle ( Figure 7c , solid line), the flow rate of the coating agent impressed by the pump 21 ( Figure 7c , dashed line) and the pressure at the coating agent nozzle 19 of the print head 18 ( Figure 7d ) during two complete switching periods T1 and T2 and half a switching period T3. In contrast to the Figure 5b to 5d After the implementation of one of the measures according to the invention, it is now achieved that the overpressure has been completely reduced by the beginning of the next following switching period, and the overpressure during the next switching period is then increased again from the same starting pressure as it was at the beginning of the previous switching period and so on, so that the pressure in the application system does not continue to rise.

Additional explanations:
The individual nozzle exit openings for the coating material usually have a diameter of approx. 10 μm to 200 μm. The individual nozzle outlet openings are due to manufacturing tolerances, wear and tear or deposits of a printhead are not completely identical.

Each of the nozzle outlet openings controlled by a valve therefore has a different flow resistance. The amount of material _V̇ i flowing through the nozzle outlet opening i depends on the pressure in front of the outlet opening p _i . This relationship is described by the function V̇ _i = f _i ( p _i ) or the inverse function p _i = g _i ( V̇ _i ).

When designing a print head, care is taken to ensure that the pressure at all nozzle outlet openings is always the same, i.e. the pressure drop in the coating medium feed line should be negligible.

It should be noted that the functions f _i and g _i depend on the viscosity and thus on the coating material applied.

wobei k_i ein Kennwert der Austrittsöffnung ist und v die Viskosität des Materials.As a first approximation, one can assume that the functions described above are linear in the region of interest. The equation for the nozzle orifice is $${\dot{V}}_i=\frac{k_i}{v}p$$

where k _i is a characteristic value of the outlet opening and v is the viscosity of the material.

The print head is moved at a constant speed over the surface to be coated. The material properties, the layer thickness to be achieved and the distance between the outlet openings then result in an average paint flow rate, if paint is the coating agent, or an average coating agent flow rate. $${\dot{V}}_m=\frac{\mu \cdot {\mathrm{i.e}}_D{\mathrm{v}}_{\mathrm{a}}}{f_V}$$

V̇ m

mittlere Lackflussrate pro Düse

dD

Abstand zwischen den Düsen senkrecht zur Bewegungsrichtung (bei mehreren hintereinander angeordneten Applikatoren resultierender Abstand) µ Schichtdicke (Trockenfilm)

fV

Volumenfeststoffgehalt des applizierten Materials

va

Geschwindigkeit des Applikators (TCP Geschwindigkeit)

with

V̇ m

average paint flow rate per nozzle

dD

Distance between the nozzles perpendicular to the direction of movement (resulting distance when several applicators are arranged one behind the other) µ Layer thickness (dry film)

fV

Volume solids content of the applied material

maybe

Speed of the applicator (TCP speed)

The switching frequency or the time of a period (from opening of the valve to the next opening) T _p and the time T _v that the valve is open are empirical values.

The paint flow rate through a nozzle outlet opening is approximately described by the following relationship: $${\dot{V}}_D=\frac{T_D}{T_v}{\dot{V}}_m$$

The volume of the coating medium ejected when a valve is opened (droplet volume) is described by the following relationship: $$V_T={\dot{V}}_m\cdot T_D=\frac{\mu \cdot {\mathrm{i.e}}_D{\mathrm{v}}_{\mathrm{a}}}{f_V}\cdot T_D$$

With regard to a homogeneous coating, the aim is for the same quantity of coating material to flow through all nozzle outlet openings on average over time. This can be achieved by opening the individual valves for different lengths of time.

The procedure to be followed in the event that the pressure drop in the distribution line is negligible is as follows.

In the first step, the characteristic curve V̇ _i = f _i ( p ) or p _i = g ( V̇ _i ) for each outlet opening. determined.

In the case of the linearity described above, the characteristic values k _i . . . k _n are obtained with $$\bar{k}=\frac{1}{n}{\displaystyle \sum _{i=1}^n}{k}_i$$

Vorgabewert:

Lackmenge pro Ventilöffnung mittlere Ventilöffnungszeit

The following applies to the variant of the coating material supply with a material pressure regulator:

default value:

Amount of paint per valve opening average valve opening time

$$\frac{T_i}{T_v}=\frac{\bar{k}}{k_i}$$

The material pressure to be set on the material pressure regulator and the valve opening time result in: $$p=\frac{v}{\bar{k}}{\dot{V}}_D$$

$$\frac{T_i}{T_v}=\frac{\bar{k}}{k_i}$$

The valve opening time is indirectly proportional to the characteristic value

If the coating material is supplied via a dosing pump, for example, the following applies:
The advantage of using a metering pump in a coating device is that the fluidic conditions in the entire application system are independent of the viscosity of the coating agent and therefore parameter values do not have to be set for the coating material used in each case

Since the pump works the entire time with the same coating agent rate, i.e. with a constant paint flow rate if paint is the coating agent, the coating agent pressure or the paint pressure depends on how many valves are open. The fewer valves that are open, the higher the pressure. This means that the time differences between the individual valve switching times are lower than when operating with constant pressure. <u>Reference List</u> 1 printhead 2 Coating agent nozzle 3 printhead 4 Coating agent nozzle 5 Valve 6 Coating agent feed line 7 partial arm 8th partial arm 9 application system 10 printhead 11 printhead 12 printhead 13 Coating agent nozzle 14 subarea 15 printhead 16 Scheme of an operating mode 17 application system 18 printhead 19 Coating agent nozzle 20 Valve 21 pump 22 coating agent supply line 23 Coating agent return line 24 recirculation valve 25 valve control 26 operation mode 27 operation mode

Claims (2)

Application system for coating components with a coating agent, which includes the following assemblies: - an application device which applies the coating agent, the application device being a print head (1, 3) which ejects the coating agent from a plurality of coating agent nozzles (2, 4, 19), a nozzle valve (5, 20 ) is attached, which opens for a valve opening time when a drop of coating agent is to leave the respective nozzle (4), - a coating medium supply line (6, 22) to which the coating medium nozzles (4) of the print head (3) are jointly connected, - a valve controller (25) for controlling the valve opening times and valve closing times of each individual valve (20),
characterized in that the application system further comprises a pump (21) by means of which the coating agent to be applied is fed to the coating agent nozzles (19) via the coating agent feed line (22), and in that the application system is set up such that the pump (21) during the coating operates with a constant flow rate of coating agent and that the pressure at each nozzle (19) when the valve (20) opens is the same as when that valve (20) was previously opened; wherein the application system has a coating medium return line (23) in which a return valve (24) is installed, which opens at least when the nozzle valves (20) of the print head (18) are closed at the same time. Coating device for coating components with a coating agent, with an application system according to claim 1, wherein the coating device comprises a robot on which at least the application device is accommodated.

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