DE102020004514A1 - Method for monitoring a surface profile in a 3D printer - Google Patents

Abstract

The invention, which relates to a method for monitoring a surface profile in a 3D printer, is based on the object of specifying a solution with which the surface profile of a layer of particulate building material on a building site or of 3D partial structures within can be recorded easily, quickly and reliably a layer of a particulate building material on the building site to monitor the quality of the creation of a 3D structure, with the technical effort and costs being reduced. This object is achieved in that an optical analysis of the generated image of the surface profile (1) is carried out and that in this analysis a correct or incorrect generation of 3D partial structures and/or a correct or incorrectly generated structure of the particulate building material applied in layers (2) is determined.

Description

The invention relates to a method for monitoring a surface profile in a 3D printer, in which an image of the surface profile is generated and evaluated on a construction area of a 3D printer.

In particular, a surface profile is to be monitored on a construction site, with each individual applied layer of a particulate construction material being monitored, as well as parts of a layer. With such a monitoring, irregularities in the application of the particulate building material or the generation of a 3D partial structure are monitored in particular. Errors in the construction of a layer of a particulate building material and errors in the construction of a 3D partial structure are detected here.

It is known to use so-called 3D printing or a so-called 3D printing process to produce individual or serial components, workpieces or molds. In such printing processes, three-dimensional components or workpieces are produced in layers.

The structure is computer-controlled from one or more liquid or solid materials according to specified dimensions and shapes. Specifications for the components or workpieces to be printed can be provided, for example, by so-called computer-aided design systems (CAD).

When printing the 3D structures or 3D components, physical or chemical hardening processes or a melting process take place in a particulate building material, which is also referred to as molding material. Building materials or molding materials such as plastics, synthetic resins, ceramics and metals are used as materials for such 3D printing processes.

Various manufacturing process sequences are known for the implementation of 3D printing processes.

• • Teil- oder vollflächiges Auftragen von partikelförmigem Baumaterial, auch als Partikelmaterial oder pulverförmiges Aufbaumaterial bezeichnet, auf ein sogenanntes Baufeld, um eine Schicht aus nichtverfestigtem Partikelmaterial zu bilden;
• • Selektives Verfestigen der aufgebrachten Schicht aus nichtverfestigtem partikelförmigem Baumaterial in vorbestimmten Teilbereichen, beispielsweise durch ein selektives Verdichten, Aufdrucken oder Aufbringen von Behandlungsmittel, wie beispielsweise einem Bindemittel oder Einsatz von Laser;
• • Wiederholung der vorhergehenden Verfahrensschritte in einer weiteren Schichtebene zum schichtweisen Aufbau des Bauteils oder Werkstücks. Hierfür ist es vorgesehen, das Bauteil oder Werkstück, welches auf dem Baufeld schichtweise aufgebaut bzw. aufgedruckt wird, mit dem Baufeld jeweils um eine Schichtebene oder Schichtdicke abzusenken oder die 3D-Druckvorrichtung jeweils um eine Schichtebene oder Schichtdicke gegenüber dem Baufeld anzuheben, bevor eine neue Schicht teil- oder vollflächig aufgetragen wird;
• • Nachfolgendes Entfernen von losem, nichtverfestigtem partikelförmigem Baumaterial, welches das gefertigte Bauteil oder Werkstück umgibt.

However, several of these procedural sequences include the procedural steps shown below by way of example:

• • Partial or full-surface application of particulate building material, also referred to as particulate material or powdered building material, on a so-called building field in order to form a layer of non-solidified particulate material;
• • Selective solidification of the applied layer of non-solidified particulate building material in predetermined partial areas, for example by selective compacting, printing or application of treatment agent, such as a binder or use of a laser;
• • Repetition of the previous process steps in a further layer level to build up the component or workpiece layer by layer. For this purpose, the component or workpiece, which is built up or printed on in layers on the construction area, is lowered with the construction area by one layer level or layer thickness or the 3D printing device is raised by one layer level or layer thickness compared to the construction area before a new one layer is applied over part or all of the surface;
• • Subsequent removal of loose, unconsolidated particulate build material surrounding the manufactured component or workpiece.

Various methods for generating a 3D structure or for applying particulate construction material to a construction site to generate a 3D structure are known from the prior art.

Various methods for optically monitoring a surface profile in a 3D printer are also known.

From the DE 10 2017 202 088 A1 a method for powder bed-based additive manufacturing of a workpiece is known. In addition, a computer program product that is suitable for the automatic implementation of the method and a computer-readable data carrier with such a computer program product and a machine are disclosed.

The problem to be solved is to specify a method for the powder bed-based additive manufacturing of components, in which a metrological detection of the surface of the manufactured work piece position can be used to correct the manufacturing result. In addition, a computer program product is to be specified which can control such a method.

The solution is that a computer generates a surface profile of the topography recorded by measurement. In addition, the computer for permissible height differences between the surface profile of the workpiece position in question and the target surface or a tolerance range is taken into account for the permissible height difference between the highest area and the lowest area of the measured surface profile of the relevant workpiece position. In the event that a height difference determined for the surface profile is outside the tolerance range, the computer causes the control device to apply an additional layer of powder to the powder bed and to solidify a local intermediate layer in the deeper areas of the workpiece layer in question, with which the existing height differences be reduced.

In order to achieve this, a metrological detection of the surface profile is provided with a measuring device using an optical triangulation sensor system.

Such a metrological detection is technically complex and requires a cost-intensive technique for triangulation. In addition, there can be measurement inaccuracies, since distortions or blurring can occur when evaluating the sensor signals.

Thus, there is a need for an improvement in the known art and thus for an improved method for monitoring a surface profile in a 3D printer.

The object of the invention is to provide a method for monitoring a surface profile in a 3D printer, with which a simple, fast and reliable detection of the surface profile of a layer of particulate building material on a construction site or 3D substructures within a layer of particulate building material takes place on the construction site to monitor the quality of the generation of a 3D structure, with the technical effort and costs being reduced.

The object is achieved by a method with the features according to patent claim 1 of the independent patent claims. Further developments are specified in the dependent patent claims.

It is provided that an arrangement, which is referred to below as a scanning arrangement, with a number of optics or optical sensors is arranged over the construction area of a 3D printer or a 3D printing machine.

In this case, the optical sensors in the scanning arrangement are arranged next to one another in a row or line, with the longitudinal extent of the scanning arrangement extending over the entire width of the build area of the 3D printer.

It is intended that this scanning arrangement moves over the construction area of a 3D printer, the distance between the optical sensors and the surface of the construction area being, for example, at a distance of between 0.5 mm and 2 mm, in particular at a distance of 1 mm , is kept constant and remains constant during this movement over the construction area.

During this movement, too, the scanning arrangement is aligned at an angle of 90 degrees to the direction of movement over the construction area. This direction of movement of the scanning arrangement corresponds to the direction of movement of the working equipment of the 3D printer over the construction site. Such working means can be, for example, a stripping element such as a squeegee, a blade or an oscillating blade.

It is also provided that during this movement of the scanning arrangement over the construction area, images or recordings of the surface of the construction area are generated or recorded by means of the optical sensors arranged in a line. In this way, an image of the surface profile is generated on the construction site. The frequency of this scan of the surface of the construction site using the optical sensors is up to 30 kHz. With an appropriately selected speed of movement of the scanning arrangement in the range between 1 mm/s and 3000 mm/s, images of the surface profile are possible with an accuracy or resolution of up to 10000 dpi.

When scanning using this scanning arrangement, a line consisting of several pixels is generated as an optical partial image of the surface of the construction field. By moving the scanning arrangement over the surface of the building site and continuously repeating this scan, partial images of the surface profile of the building site are generated line by line in a sequential manner. These partial images are assembled line by line using appropriate processing software, which is processed in a processing unit associated with the 3D scanner, to form an overall image of the surface or the surface profile of the construction site, referred to here as an image. This creates a complete picture of the surface profile with a high resolution, the mapping of the surface profile. Such a resolution is, for example, in the range from 150 dpi to 1200 dpi, which corresponds to a number of 1200 optical sensors in one line of a scanning arrangement with a length of 25.4 mm.

By a coordinated frequency for scanning by means of the scanning arrangement and a corresponding speed for the movement of the scanning arrangement over the surface of the construction field, images of the surface or the surface profile are generated with a very high resolution and accuracy. A higher resolution of the image to be generated in the direction of movement of the scanning arrangement is thus achieved by means of a higher frequency during scanning or a higher recording frequency. Since the number of optical sensors arranged in a line in the scanning arrangement does not change from, for example, 1200 sensors to a length of 25.4 mm, the resolution in the direction of the line of the scanning arrangement is independent of the speed of the scanning arrangement in the direction of movement. This resolution is only determined by the permanently installed number of optical sensors in line.

The optical sensors have, for example, what is known as a focus range, which can be around 1 mm. This means that the resulting images of the surface of the construction area or the resulting scans have a high level of accuracy if the distance between the optical sensors and the surface of the construction area is exactly 1 mm. Since this distance of 1 mm to the surface is kept constant during the movement of the scanning arrangement over the surface of the construction area, high-quality images are produced without the need for adjustment or processing of the data from the optical sensors.

During the scans carried out with the scanning arrangement, the optical sensors are aligned perpendicularly to the construction area and also to the surface of the construction area, which can be formed by an applied particulate construction material. The images or scans are orthographic. Thus, no measures such as optical equalization are necessary to generate an image of the surface of the construction area.

Provision is made for the alignment or position of the scanning arrangement to be calibrated over the surface of the construction field. For this purpose, it is provided to use a template, for example with an image of a chessboard and a resolution of 3600 dpi by 3600 dpi, over which the scanning arrangement is moved at a distance of 1 mm, for example.

When the scanning arrangement moves over the template forming the surface of the construction field for calibration purposes, the exemplary checkerboard pattern makes it possible to recognize whether the scanning arrangement is aligned at an angle of exactly 90 degrees to the direction of movement over the construction field. If deviations occur during this calibration that exceed a certain tolerance limit, then there is the possibility of mechanically readjusting the scanning arrangement in order to eliminate the deviation. Alternatively, the determined deviation can be saved.

In this case, the image of the surface of the construction site or a surface profile generated by the scanning arrangement is corrected by computer using the stored deviation.

It is also planned that the scanning arrangement will be used in different phases of the creation of a 3D structure on the construction site.

The scanning arrangement thus generates an image of the surface of the construction area or the surface profile without particulate construction material applied to the construction area.

In particular, the scanning arrangement generates an image of the surface of the construction area or the surface profile after particulate construction material has been applied to the construction area. In this case, the application of the particulate building material to the building site can be carried out partially or completely.

Alternatively, the scanning arrangement generates an image of the surface of the construction area or the surface profile after the particulate construction material applied to the construction area has been selectively solidified, which can be done, for example, by imprinting a binding agent. Such binders can be organic or inorganic liquid adhesives, for example, which can be applied, for example, by means of a print head.

Images of the respective surface profile of the construction site as two-dimensional images (2D images) can be generated, for example, in the states before or after the application of the particulate building material or before or after selective solidification of the particulate building material.

The images described are preferably generated by means of the scanning arrangement described here, but is not restricted to this. For example, a wide-angle camera can also be used for high-resolution recording of the entire construction area, with these recordings subsequently having to be corrected. Disadvantages are that a longer traversing path is required to record the entire construction area. In addition, the work equipment must Generation of the images are each driven to the side.

Alternatively, several cameras, possibly with special lenses, can be arranged across the recording width and offset in the direction of travel if this is necessary due to the limited installation space for each camera. This variant can be used to generate recordings in the form of individual images or videos and, for example, rectify them and put them together.

As a further alternative, one or more 3D line lasers with greyscale recording can be used. If several of these 3D line lasers are used, the accuracy of the image to be generated is improved.

In addition, multiple scanning arrangements with optical sensors arranged in a line can also be arranged in order to cover the entire width of the construction field.

These scanning arrangements can also be offset from one another in the direction of travel.

It is intended to evaluate or analyze the images or 2D images generated, for example, with a scanning arrangement, in order to detect errors in the respective phases of the generation of a 3D structure on the construction site. Such an evaluation can be carried out, for example, by an experienced operator viewing the 2D images.

An analysis or an image comparison, controlled by appropriate software, is much faster and more effective. With such an analysis, for example, irregularities in the surface profile can also be detected in addition to errors in the generation of the 3D structure on the construction site. Such irregularities indicate, for example, places where too much or too little particulate building material has been applied. Such irregularities also indicate, for example, places where there are foreign bodies on the surface. Alternatively, such irregularities indicate, for example, a change in the composition of the particulate building material.

Irregularities can also occur if, for example, a defective squeegee, a defective blade or a defective oscillating blade causes indentations such as a trench or elevations when the surface of the particulate building material is scraped off or smoothed.

Furthermore, for example, irregularities in a surface profile recorded after selective solidification by means of printing of a binder indicate defects in nozzles of a print head, a defective print head or an incorrect alignment of such a print head. It is known here that 3D printers of the type according to the invention usually have a plurality of print heads arranged in a group, which are arranged precisely aligned with one another.

In addition, further errors in the generation of a 3D structure can be derived by analyzing the recorded surface profile.

If errors and/or inaccuracies are found in such an analysis of the generated image, measures or countermeasures are initiated in order to reduce or eliminate the errors and/or inaccuracies.

If no errors and/or inaccuracies are found in such an analysis of the generated image, the generation of the 3D structure is continued according to plan.

For example, an image comparison can be used to check that a 3D structure has been correctly generated. From data for the 3D structure to be produced, which is available in the 3D printer for each layer to be produced, it is possible to generate or produce an expected image, ie a target image. Such a target image can be generated for each layer. Such a target image can also be generated for different method steps within a layer. Such method steps are, for example, applying a particulate material, compacting the particulate material, selectively solidifying the particulate material, for example by means of a binder, and others. In this way, this target image can be compared with the recorded surface profile, ie the generated image, and errors and/or inaccuracies can be detected.

It is also provided that the target image generated for each layer to be generated or the target images generated for different method steps within a layer are stored. In the event that the same 3D structure is to be generated several times in the 3D printer, it is possible to access the saved target images.

In the event that such errors and/or inaccuracies exceed a predetermined tolerance step, the creation of the 3D structure is faulty. Thus, for example, errors in print heads, lasers, extruders, applicators, blades, squeegees and other elements of a 3D printer can be detected.

In a 3D printer using the inkjet process, for example, errors in the alignment of one or more print heads in the X direction and/or in the Y direction can be detected. Errors caused by clogged nozzles, contamination, nozzle plate defects and others can also be detected.

If errors and/or irregularities of this type are detected by the method, a corresponding error message can generally be output and such a defect can be shown specifically, for example by means of a corresponding label.

In addition, provision is made for taking direct countermeasures, for example software-controlled, when an error and/or an irregularity is detected.

For example, if one or more clogged nozzles is detected or if a deterioration in the quantity of a binder discharged from one or more nozzles is detected, a targeted cleaning process can be initiated before the next layer of the 3D structure to be produced is produced.

If, for example, no improvement in the printed image is achieved when one or more clogged nozzles are detected by means of cleaning, a failure of the controlling electronics can be concluded in this way. In this case, for example, a test routine can be initiated and an error in the electronics can be analyzed.

If, for example, a misalignment of a print head is determined, there is the possibility of readjusting the print head in the X direction and/or in the Y direction and thus reducing or eliminating the misalignment if there are corresponding remote-controlled adjustment means on the print head.

In the event that such adjustment means are not available on a print head, there is the possibility of correcting the alignment using software, for example by controlling the nozzles of a print head, which should be aligned at an angle of 90 degrees to the direction of movement over the construction field, and at the same time in normal operation are driven at different times so as to reduce or eliminate misalignment.

In addition, it is also provided that when a defect and/or an irregularity is detected, depending on the defect pattern, assemblies such as an applicator of the particulate building material (recoater), a laser, an extruder, a blade, a squeegee and other elements of a 3D printer in their Functionality or to influence their position or alignment by means of appropriate software and appropriate adjustment means such that the errors and / or irregularities caused are reduced or eliminated.

It is provided according to the invention that by scanning the surface profile of the construction site in different phases of the creation of a 3D model, conclusions can be drawn about the respective status of different assemblies of the 3D printer without monitoring these assemblies with suitable sensors.

It is also provided according to the invention that when errors and/or irregularities are detected in these assemblies, a manual or software-controlled correction takes place with the aim of reducing or eliminating the error and/or irregularity.

For the purpose of detecting errors and/or irregularities in assemblies, provision is also made for corresponding error images to be stored. In this way, the scanned surface profile or the image generated from the surface profile can also be compared with stored error images and the type of error or defect in an assembly can be determined in this way.

Such defect images can also depict only partial areas of the entire surface profile and represent comparable patterns for defects such as stripes, indentations, holes and other defects on a surface of the particulate material. If, during an image comparison of the generated image of the surface profile, a match with these error images of partial areas with a specific percentage match is established, then a corresponding error is inferred. The fault determined in this way can then be used to infer one or possibly several defective assemblies.

A major advantage of the method according to the invention for monitoring a surface profile in a 3D printer lies in the accuracy of the scan of the surface profile, ie the generated image, with such a scan taking place, for example, with a resolution of 1200 dpi by 1200 dpi. Such errors and / or irregularities can be detected, which others otherwise can only be detected with a microscope.

A further advantage of the method according to the invention can be seen in the fact that the image of the surface profile can be generated without additional expenditure of time being necessary. Thus, the time for generating a 3D structure is not increased when using the method according to the invention. This is possible because the scanning arrangement is arranged and movable parallel to the working means of the 3D printer.

Thus, the scanning arrangement can be moved, for example, parallel to an applicator for the particulate building material, at a small distance from this and, for example, at the same speed over the building site.

Provision is also made for information about the arrangement of the particles and the density of the particulate building material on the construction site to be obtained by evaluating the image of the surface profile.

Image processing of the scan of the image of the surface profile, for example by means of a false-color display, can be used to intensify depressions or elevations on the surface of the particulate building material on the construction site and thus better identify them.

It is also planned to carry out a white balance. For this purpose, for example, a white template placed on the construction field can be used. A white balance can then be carried out by means of a scanning process of this template and corresponding data for this can be stored.

A further advantage of the method according to the invention can be seen in the fact that the optical sensors of the scanning arrangement enable an orthographic recording of the surface profile and that no measures are therefore necessary to rectify the recording of the surface profile.

It is also not necessary to scale the recording or the scan of the surface profile, as may be necessary with other optical recording methods, for example with a camera.

Provision is made for so-called reference marks to be arranged at the edge of the construction area in order to detect the current position of the scanning arrangement over the construction area. These reference marks are also scanned or recorded by the correspondingly wide scanning arrangement, can thus be evaluated and in this way enable conclusions to be drawn about the current position of the scanning arrangement over the construction site.

Various image processing methods known from the prior art can be used in connection with the image comparison of the generated image with the target image to be expected.

For example, it is possible to work with a pixel-based false color representation. In this case, for example, a number of pixels in colored areas of the generated image can be determined and set in relation to the target number of pixels.

Alternatively, a check for the presence of colored components can be carried out. In one example, it is checked whether red pixels, which are not expected, are absent, green pixels, which are expected, are present and blue pixels, which are expected, are also present. If it is determined that only red pixels can be found, the blue pixels are missing, and an incorrect image of the surface profile has been found and appropriate measures are initiated. Such tests can be carried out for pixels or also for surface areas. With a grid evaluation, color areas can be positively or negatively strengthened or neutralized. As a result, areas can emerge, especially with high resolutions, which in turn can be analyzed for the number of pixels.

For example, an edge detection of outer contours, for example a 3D partial structure, can also take place. In this case, such outer contours can be converted into so-called standard geometries, for example. Such standard geometries can include lines, arcs or splines. In this case, splines represent functions which are piecewise composed of polynomials of at most the nth degree.

These standard geometries found or detected in the generated images can then be compared with the target images, which also contain standard geometries. Among other things, positions, straightness, angles and others can also be evaluated.

In addition, during the analysis, a region can be recognized or region selected, in which partial regions of the generated image are selected for analysis. In this way, partial areas can be selected for detecting errors and/or irregularities. Methods known from the prior art could also be used within such sub-areas Image processing is used, such as those described above.

• 1: eine beispielhafte erste Aufnahme eines Oberflächenprofils eines Baufelds in einem 3D-Drucker,
• 2: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem ersten Fehler,
• 3: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem zweiten Fehler,
• 4: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem dritten Fehler,
• 5: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem vierten Fehler,
• 6: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem fünften Fehler,
• 7: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem sechsten Fehler,
• 8: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem siebenten Fehler,
• 9: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem achten Fehler,
• 10: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem neunten Fehler,
• 11: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem zehnten Fehler,
• 12: eine Aufnahme eines Oberflächenprofils eines Baufelds mit einem elften Fehler und
• 13: einen prinzipiellen Verlauf des Verfahrens zur Überwachung eines Oberflächenprofils in einem 3D-Drucker.

The foregoing features and advantages of this invention will be better understood and appreciated after a careful study of the following detailed description of preferred non-limiting example embodiments of the invention herein, with the accompanying drawings, which show:

• 1 : an exemplary first recording of a surface profile of a construction site in a 3D printer,
• 2 : a recording of a surface profile of a construction site with a first error,
• 3 : a recording of a surface profile of a construction site with a second error,
• 4 : a photograph of a surface profile of a construction site with a third error,
• 5 : a photograph of a surface profile of a construction site with a fourth error,
• 6 : a photograph of a surface profile of a construction site with a fifth error,
• 7 : a photograph of a surface profile of a construction site with a sixth defect,
• 8th : a photograph of a surface profile of a construction site with a seventh error,
• 9 : a recording of a surface profile of a construction site with an eighth error,
• 10 : a photograph of a surface profile of a construction site with a ninth error,
• 11 : a photograph of a surface profile of a construction site with a tenth error,
• 12 : a photograph of a surface profile of a building site with an eleventh error and
• 13 : a principle flow of the method for monitoring a surface profile in a 3D printer.

In the 1 an exemplary first recording of a surface profile 1 of a construction field in a 3D printer is shown. This recording of the surface profile 1, which was generated by means of a scanning arrangement not shown, was generated in a state in which the particulate building material 2 applied to the construction site forms selectively solidified areas, for example by imprinting a binding agent with corresponding print heads, not shown, which are arranged in the current layer Represent 3D partial structure of a 3D structure to be produced in the 3D printer.

This first recording of a surface profile 1 in the 1 depicts a flawless application of the particulate building material 2 and the binder for the configuration of the 3D partial structures 3.

If the method according to the invention for monitoring a surface profile 1 in a 3D printer produces such a recording of the surface profile 1 by means of the scanning arrangement, a properly applied layer of the particulate building material 2 is recognized according to the method by means of an image comparison and also a proper application of the binding agent for the configuration of the 3D substructures 3 detected. In such a case, the generation of the 3D structure in the 3D printer is continued without being affected by the method.

In the 2 a recording of a surface profile 1 of a construction site with a first error is shown. This recording of the surface profile 1, generated by means of a scanning arrangement not shown, was also generated in a state in which the particulate building material 2 applied to the construction site forms selectively solidified areas, for example by imprinting a binding agent with corresponding print heads, not shown, which areas in the current layer arranged 3D partial structure of a 3D structure to be generated in the 3D printer. This statement regarding the recording of the surface profile 1 also applies to the following figures and is therefore not repeated.

In the 2 a blurred error area 4 is shown in each of the areas of the 3D partial structures 3 . This blurry error area 4 can be partially or, as in the 2 shown, extend completely around the 3D partial structures 3.

If such a blurred error area 4 is detected using the present method when evaluating the recording of the surface profile 1, then, for example, an error in the focusing of the scanning arrangement, i.e. an incorrect distance between the optical sensors of the scanning arrangement (not shown) and the surface of the construction field, getting closed. Such an error can be eliminated by a corresponding change in the position of the construction field, for example using software.

Alternatively, an error in the controlling mechanics of the 3D printer or blade wear can lead to such an error pattern.

Further alternatively, these blurry error areas 4 can be caused by an incorrect consistency of the binding agent or an incorrect binding agent medium or an incorrect dosage of the binder in the blurred defect areas 4.

In such a case, the generation of the 3D structure in the 3D printer is either influenced according to the method by automatically switching to an alternative binding agent or the generation of the 3D structure is stopped and a corresponding error message is output.

In the 3 a recording of a surface profile 1 of a construction field with a print area error 5 is shown. In the representation of 3 a 3D partial structure 3 is missing completely. Such a print area error 5 is caused by a temporary or permanent failure of a segment of a printhead or by a temporary or permanent failure of an entire printhead. Such print heads usually consist of several areas or segments. Thus, the area for the required 3D partial structure 3 is not properly selectively solidified in this layer. This area is in 3 marked with a frame represented by a dash-dash line.

It is assumed here that the direction of movement of the working equipment and the scanning arrangement according to 3 can be aligned both horizontally and vertically, which is to be represented by the two double arrows.

In such a case, the production of the 3D structure in the 3D printer is influenced according to the method in such a way that the printing process is interrupted and a corresponding print head is cleaned or by a corresponding error message being output.

In the 4 a recording of a surface profile 1 of a building site with a third defect is shown.

Such an error pattern of a print area error 5 is caused by a failure of an area or segment of a print head or a failure of an entire print head of several print heads arranged in a group or by a defective or dirty blade. It is assumed here that the direction of movement of the working equipment and the scanning arrangement according to 4 is aligned horizontally, which is intended to be represented by the double arrow.

In such a case, the production of the 3D structure in the 3D printer is influenced according to the method in such a way that the printing process is interrupted and a corresponding print head is cleaned or by a corresponding error message being output. If the print area error 5 is caused by a defective or dirty blade, this error will be displayed. In the event that the technology of the 3D printer supports this, a blade could also be changed automatically or switched to another assembly, for example a replacement assembly of a redundant system with an intact blade.

In the 5 a recording of a surface profile 1 of a construction site with a fourth defect is shown.

The scaling error 6 shown occurs at least within the areas shown by a dash-dash line and leads to a compression of the 3D partial structure 3 in the direction of movement of the working means of the 3D printer, which is indicated by the double arrow.

This can be caused by an incorrectly set resolution in the direction of movement of the work equipment. Alternatively, there may be a fault in the displacement measurement system, which determines the position of the work equipment, such as a print head, over the construction area of the 3D printer.

In such a case, the production of the 3D structure in the 3D printer is influenced according to the method in such a way that the printing process is interrupted, for example, and a corresponding error message is output. Alternatively, for example, the resolution can be set to the correct value under software control or the position measuring system can be recalibrated.

In the 6 a recording of a surface profile 1 of a building site with a fifth defect is shown.

Such an alignment error 7 is caused by an incorrect alignment of one or more print heads of the 3D printer. The alignment error 7 is shown within the areas shown by a dash-dash line. The alignment error 7 leads to an angle deviating from 90 degrees between the imaginary longitudinal axis of the 3D partial structures 3 represented by a dash-dot line and the direction of movement of the working means of the 3D printer represented by a double arrow.

In such a case, the production of the 3D structure in the 3D printer is influenced according to the method in such a way that the affected print heads are automatically adjusted in order to reduce or eliminate the error.

Alternatively, the printing process is stopped and a corresponding error message is output.

In the 7 a recording of a surface profile 1 of a building site with a sixth defect is shown. An error in the form of a defect 8 is shown, which has been caused by the failure of one or more nozzles, for example in a print head or in a region of a print head.

If a nozzle of a print head fails, no binder is applied to the particulate building material 2 at the location of the failed nozzle, so that no selective solidification occurs in this in the 7 strip-shaped area takes place. Such a strip-shaped area extends parallel to the direction of movement of the working means of the 3D printer, which is represented by a double arrow. In the 7 the defect 8 can be seen within the area shown by means of a dash-dash line.

In such a case, the generation of the 3D structure in the 3D printer is influenced according to the method in such a way that the affected print head is automatically cleaned in order to reduce or eliminate the error.

In the 8th a recording of a surface profile 1 of a building site with a seventh error is shown. Impurity 9 can be seen, such as a foreign body, which has accidentally landed on the surface of particulate building material 2 on the construction site. This foreign body is moved over the surface of the particulate building material 2 by a working medium of the 3D printer, for example, and causes a ditch within the area represented by a dash-dash line. This trench is thus created in the direction of movement of the working equipment of the 3D printer, which is shown by means of a double arrow.

In such a case, the production of the 3D structure in the 3D printer is influenced according to the method in such a way that the production of the 3D structure is stopped in order to prevent errors from occurring when the 3D structure is produced by the impurity 9 . An associated error message is issued.

In the 9 a recording of a surface profile 1 of a building site with an eighth error is shown. Within the area shown by a dash-dash line in the 9 a furrow 10 can be seen, which is caused by a local blockage in a working medium of the 3D printer, such as an applicator or recoater. Due to this local blockage, no particulate building material 2 is applied to the building site at this point. Due to the movement of the working means in the direction of movement represented by a double arrow, the furrow 10 also extends in this direction. The furrow 10 is in the 9 shown within the area shown by a dash-dash line.

In such a case, the production of the 3D structure in the 3D printer is influenced according to the method in such a way that the production of the 3D structure is stopped in order to prevent errors from occurring when the 3D structure is produced by the furrow 10 . An associated error message is issued.

In the 10 a recording of a surface profile 1 of a building site with a ninth defect is shown. The one in the 10 The first flaws 11 to be recognized have arisen, for example, as a result of contamination or flaws in the mixture of the particulate building material 2 . Such an accumulation such as an agglomerate, for example solidified, forms a defect 11, impairs the creation of a 3D structure and leads to defects within the 3D structure to be created. The first error points 11 are in the 9 shown within the areas shown by means of a dash-dash line.

In such a case, the production of the 3D structure in the 3D printer is influenced according to the method in such a way that the production of the 3D structure is stopped in order to prevent errors in the production of the 3D structure from first defect locations 11 occurring. An associated error message is issued.

In the 11 a recording of a surface profile 1 of a building site with a tenth error is shown. Within the area shown by a dash-dash line in the 11 a second defect 12 is shown.

This second defect 11 extends along an outer area of the large 3D partial structure 3. The second defect 12 is caused, for example, by an excessively high movement speed of a working medium of the 3D printer, such as a print head, which moves in the direction shown by the arrow. Alternatively, the second fault location 12 can be caused by nozzles not closing properly or in good time in one area of a print head, in one print head or in a plurality of print heads.

No proper or sharp-edged transition between the 3D partial structure 3 and the particulate building material 2 is formed in the area of the second fault location 12 .

These second flaws 12 are also problematic in the case when the working means are moved across the construction field not just in one direction, but in two, when generating a 3D structure. For example, in a first direction of movement of the work equipment over the construction site, as indicated by the arrow in the 11 is shown, the second defect 12 is generated on the right-hand side of the 3D partial structure 3 . In a second direction of movement of the work equipment over the construction site, which is opposite to the first direction, the second error point 12 in the 11 on the left side of the 3D substructure 3 creates what is in the 11 is not shown. The second defect locations 12 are thus generated alternately, for example, which leads to a deterioration in the quality of the 3D structure to be generated.

In the case of very small 3D substructures to be produced, these second defects 12 can be so strongly offset from one another that the 3D structure to be produced is no longer stable in this area.

If such errors occur, the generation of the 3D structure in the 3D printer is influenced according to the method in such a way that the generation of the 3D structure is continued at a lower speed in order to prevent errors in the generation of the 3D structure by the second Error point 12 occur. Alternatively, the creation of the 3D structure can be interrupted and an associated error message can be output.

In the 12 a recording of a surface profile 1 of a building site with an eleventh error is shown. In this case, the recording or the scanning of the surface profile 1 has taken place after a particulate building material 2 has been applied in a new layer. 3D partial structures are only formed in this layer at a later point in time.

the 12 shows a large image of a surface profile 1 and in the right part of the 12 an enlargement of an area of the surface of the surface profile 1 encompassed by the dash-dash line.

Structural defects 12 within the particulate building material 2 can be seen in this enlargement. Structural defects 12 of this type can occur as a result of the particulate building material 2 segregating.

A wrong color tone of the surface structure 1 can also be recognized as a defect. The color of the particulate building material 2 to be applied is usually known. This depends on the substances contained in the particulate building material 2 . For example, based on the color or the hue of the surface structure 1, a mixing ratio can be inferred.

Thus, in the event that the color of the surface structure 1 deviates from an expected color, an incorrect mixing ratio or an incorrect material for the particulate building material 2 can be inferred.

In such a case, the creation of the 3D structure in the 3D printer is influenced according to the method in such a way that the creation of the 3D structure is stopped in order to prevent errors in the creation of the 3D structure from an incorrect or faulty particulate building material 2 appear. An associated error message is issued.

In order to avoid or eliminate errors when applying the particulate building material 2, it is also provided that the parameters for applying the particulate building material 2 are adjusted or changed. Parameters when applying the particulate building material 2 are, for example, a gap dimension at the outlet of an applicator of the particulate building material 2 or at the recoater, the quantity of the particulate building material 2 to be applied in a unit of time, an adjustment angle of a working tool such as a blade, for example to the perpendicular or to the surface of the construction site , an initial position at which the application of the particulate building material 2 begins, or a density of the particulate building material 2 to be applied and solidified.

In the 13 a basic course of the method for monitoring a surface profile 1 in a 3D printer is shown.

The method starts in step 14. In the subsequent step 15, the image of the surface profile 1 is generated in the 3D printer, with this image showing the current surface of the top layer on the construction field. This layer can be newly created, for example, by applying the particulate building material 2 . Alternatively, in this uppermost layer, after the application of the particulate building material 2, a selective hardening can already have taken place in predetermined partial areas by imprinting a binding agent.

The corresponding image of the surface profile 1 is analyzed in step 16. This analysis can be carried out, for example, by means of an image comparison, with a target image being stored or generated and stored as a reference image of the images of the layers to be expected in each case. From data for the 3D structure to be produced, which is available in the 3D printer for each layer to be produced, an image to be expected, ie a target image, is generated or produced. Such a target image can be generated for each layer or for different process steps within a layer. During the analysis in step 16, for example, an image comparison is made between the target image and the generated image of the surface profile 1.

Such an image comparison can also be made using values for a tolerance between the expected image and the generated image. This means that the smallest and tolerable errors and/or irregularities do not result in an error being displayed.

In step 17 there is a check for the presence of detected errors and/or irregularities. If it is determined in step 17 that no error and/or no irregularity was determined, the method is continued in step 15 with a further generation of a subsequent image of the surface profile 1 .

Alternatively, the method is continued in step 18, for example with automated measures to eliminate or reduce errors and/or irregularities. Alternatively, the error can also be output, for example optically or by means of an error label, and the generation of the 3D structure can be stopped.

• • eine Reinigung eines Druckkopfes oder eine Reinigung eines Bereichs eines Druckkopfes,
• • eine Justage eines Druckkopfes,
• • eine Auswahl eines alternativen Bindemittels,
• • ein automatisierter Wechsel eines Arbeitsmittels des 3D-Druckers,
• • eine automatisierte Reinigung eines oder mehrerer Arbeitsmittel des 3D-Druckers,
• • eine Justage eines oder mehrerer Arbeitsmittel des 3D Druckers,
• • eine Veränderung einer Auflösung bei einem Aufdrucken eines Bindemittels,
• • eine Veränderung einer Geschwindigkeit eines Arbeitsmittels des 3D-Druckers,
• • eine Veränderung der Parameter der Partikelmaterialaufbringung.

Measures to eliminate or reduce errors and/or irregularities can be, for example:

• • a cleaning of a printhead or a cleaning of an area of a printhead,
• • an adjustment of a print head,
• • a selection of an alternative binding agent,
• • an automated change of a working tool of the 3D printer,
• • an automated cleaning of one or more working materials of the 3D printer,
• • an adjustment of one or more tools of the 3D printer,
• • a change in resolution when printing a binder,
• • a change in the speed of a working medium of the 3D printer,
• • a change in the parameters of particulate matter deposition.

After measures to eliminate or reduce errors and/or irregularities have been carried out in step 18, it is checked in step 19 whether the measures carried out were successful.

If the error and/or the irregularity is eliminated by the measure taken or reduced in such a way that the tolerance range was reached, the method is continued in step 15 with a further generation of a subsequent image of the surface profile 1 .

In the event that the error and/or the irregularity could not be eliminated by the measure taken, the method is continued in step 20 with a status output. Since the error and/or the irregularity could not be eliminated automatically, the creation of the 3D structure is stopped. In addition, for example, the status or error status is displayed optically or by means of an error label or output in the form of data.

The method for monitoring a surface profile 1 in a 3D printer then ends in step 21.

Reference List

1

surface profile

2

particulate building material

3

3D part structure

4

blurred error area

5

Print area error

6

scaling error

7

misalignment

8th

void

9

pollution

10

furrow

11

first point of error

12

second error point

13

structural error

14

start procedure

15

Creation of an image of the surface profile

16

Analysis of the image of the surface profile

17

Errors and/or irregularities present?

18

Measures to eliminate or reduce errors and/or irregularities

19

Check Measure successful?

20

status output

21

end procedure

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102017202088 A1 [0010]

Claims (13)

Method for monitoring a surface profile (1) in a 3D printer, in which an image of the surface profile (1) is generated and evaluated on a construction area of a 3D printer, characterized in that an optical analysis of the generated image of the surface profile (1) is carried out and that in this analysis a proper or an incorrect generation of 3D partial structures and/or a properly or an incorrectly generated structure of the particulate building material (2) applied in layers is determined. procedure after claim 1 , characterized in that the image of the surface profile (1) is generated before or after an at least partial application of particulate building material (2) to the construction site of a 3D printer. procedure after claim 1 or 2 , characterized in that the image of the surface profile (1) is generated before or after a selective solidification of the applied layer of the particulate building material (2) on the building site of a 3D printer. Procedure according to one of Claims 1 until 3 , characterized in that in the optical analysis of the image of the surface profile (1) a blurry error area (4), a print area error (5), a scaling error (6), an alignment error (7), a defect (8) or a second defect (12) is determined as an error in the generation of 3D substructures. Procedure according to one of Claims 1 until 4 , characterized in that in the optical analysis of the image of the surface profile (1) a blurred error area (4), an impurity (9), a furrow (10), a first error point (11) or a structural error (13) as error in a structure of the particulate building material (2) applied in layers is determined. Procedure according to one of Claims 1 until 5 , characterized in that the errors determined during the analysis of the image of the surface profile (1) are output and displayed optically. Method according to one of Claims 1 to 6, characterized in that the errors determined during the analysis of the image of the surface profile (1) are output to a software algorithm. procedure after claim 7 , characterized in that the software algorithm, controlled by the errors determined, controls error-reducing or error-eliminating measures. procedure after claim 8 , characterized in that error-reducing or error-eliminating measures include cleaning a print head or cleaning an area of a print head, adjusting a print head, selecting an alternative binding agent, automatically changing a working medium of the 3D printer, automated cleaning of one or more working medium of the 3D printer, an adjustment of one or more working means of the 3D printer, a change in resolution when printing a binding agent, a change in the speed of a working means of the 3D printer or a change in the parameters of the particle material application. Procedure according to one of Claims 1 until 9 , characterized in that to generate the image of the surface profile (1) a plurality of optical sensors scanning arrangement is provided, which is movable over the construction field. procedure after claim 10 , characterized in that the plurality of optical sensors are provided in a line in the scanning arrangement. Procedure according to one of Claims 10 or 11 , characterized in that the scanning arrangement can be moved over the construction field at a constant distance from it. Procedure according to one of Claims 1 until 10 , characterized in that the optical analysis is carried out by means of an image comparison between a target image and the image generated.

Images