CN109334009B - Powder paving control method and device and readable storage medium - Google Patents
Powder paving control method and device and readable storage medium Download PDFInfo
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- CN109334009B CN109334009B CN201811119995.8A CN201811119995A CN109334009B CN 109334009 B CN109334009 B CN 109334009B CN 201811119995 A CN201811119995 A CN 201811119995A CN 109334009 B CN109334009 B CN 109334009B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
- B29C64/386—Data acquisition or data processing for additive manufacturing
- B29C64/393—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/10—Processes of additive manufacturing
- B29C64/141—Processes of additive manufacturing using only solid materials
- B29C64/153—Processes of additive manufacturing using only solid materials using layers of powder being selectively joined, e.g. by selective laser sintering or melting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
- B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
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Abstract
The application relates to a powder laying control method, equipment and a readable storage medium, wherein at least one intermediate image is obtained by calculating the difference between a current layer image and at least one image stored in a database, and a result image is obtained by corroding each intermediate image to remove noise and the normal sintering edge of a workpiece to be printed; on one hand, the invention solves the problem that the judgment is inaccurate due to the change of the optical environment caused by the dust falling on the lens, the scraper, the periphery of the cavity and the light source in the sintering process; on the other hand, the problem of inaccurate judgment caused by inconsistent optical reflectivities of different materials is effectively solved. Therefore, the powder laying control method, the powder laying control equipment and the readable storage medium are not only suitable for sintering of a single material, but also suitable for mixed sintering of multiple materials, and the powder laying control method, the powder laying control equipment and the readable storage medium are more accurate in detection and simpler in detection method.
Description
Technical Field
The application relates to the technical field of additive manufacturing, in particular to a powder paving control method and device and a readable storage medium.
Background
The additive manufacturing technology is an advanced manufacturing technology with the distinct characteristics of digital manufacturing, high flexibility and adaptability, direct CAD model driving, high speed, rich and various material types and the like, and has a very wide application range because the additive manufacturing technology is not limited by the complexity of the shape of a part and does not need any tool die. Selective Laser Sintering (SLS) and Selective Laser Melting (SLM) are the most rapidly developing additive manufacturing techniques in recent years.
In the additive manufacturing technology, after a workpiece is printed, powder laying actions are generally required to be repeated thousands of times, and some accidents occasionally occur in the middle of a printing device, so that problems such as powder laying loss, powder collapse, sintered workpiece warping, support collapse and the like are caused. It may also be a problem with the product design itself, such as warping of the workpiece due to defective support design. These problems can cause sintering failure of the entire workpiece if not treated once in a sintering process of thousands of times and tens of thousands of times.
In order to solve the above drawbacks caused by the powder spreading quality, the prior art also proposes some powder quality detection methods, which generally detect whether the overall gray level of the powder surface is consistent or whether the overall gray level is different from an ideal powder surface, and although the method can solve the above technical problems, the method is based on the premise that the hardware of the device generally has no problem, but during the process of specifically printing the workpiece, the hardware may have some changes, for example, the lens on the camera during the sintering process accumulates more and more powder to affect the change of the shot image, and the powder accumulated on the light source more and more to cause the gradual change, the reflection of the light source, and so on. The above hardware problem may cause misjudgment of flour quality detection, thereby affecting detection accuracy.
Disclosure of Invention
In view of the above technical problems in the prior art, the present invention provides a powder spreading control method, device and readable storage medium with more accurate detection and simpler detection method.
In order to achieve the above object, the present application provides a powder spreading control method, including the steps of:
when a powder paving detection instruction is received, acquiring a current layer image of a working area through an optical camera;
performing difference calculation on the current layer image and at least one image stored in a database to obtain at least one intermediate image, wherein each intermediate image displays all normal pixels and abnormal pixels obtained by performing difference calculation on the current layer image and each stored image;
corroding each intermediate image to remove noise and a normal sintering edge of a workpiece to be printed to obtain a result image;
counting the number of all abnormal pixels in each result image, and selecting the maximum number value as a result value;
and judging the powder paving quality according to the result value, and judging whether powder needs to be paved again according to the powder paving quality.
As a further preferable aspect of the present invention, the powder placement detection instruction is sent when the powder placement device places powder from one side of the work area to the other side, and places powder to the other side of the work area.
As a further preferable aspect of the present invention, all the normal pixels and the abnormal pixels in the intermediate image are displayed after the binarization processing.
As a further preferable scheme of the present invention, judging the powder paving quality according to the result value, and judging whether to re-pave the powder according to the powder paving quality specifically includes:
when the result value is smaller than or equal to a first preset value, judging that the powder paving is normal;
when the result value is larger than the first preset value and smaller than the second preset value, judging that the powder paving quality is poor;
and when the result value is greater than or equal to the second preset value, judging that the powder spreading is abnormal, and spreading the powder again.
As a further preferable scheme of the invention, when the powder paving is judged to be normal and the number of the images stored in the database does not reach the maximum value, the current layer image is stored in the database and is used as the last image stored in the database; or
And when the powder paving is judged to be normal and the number of the images stored in the database reaches the maximum value, storing the current layer image into the database as the last image stored in the database, and removing the first image stored in the database.
In a further preferred embodiment of the present invention, the current layer image is deleted when the powder spreading quality is poor or abnormal.
As a further preferable scheme of the invention, when the powder paving abnormality is judged and the powder paving abnormality continuously reaches the set times, the sintering of the workpiece is stopped, and the alarm is started.
As a further preferable aspect of the present invention, when the number of images stored in the database is several, the calculating the difference between the current layer image and the number of images stored in the database to obtain the number of intermediate images specifically includes:
respectively carrying out subtraction operation on the current layer image and each pixel point at the same position in each image stored in a database;
and taking the absolute value of the value obtained by the subtraction as a final value;
and when the final value is greater than the difference parameter, marking the pixel as an abnormal pixel, and when the final value is less than or equal to the difference parameter, marking the pixel as a normal pixel.
The invention also provides a powder paving control device which comprises a memory, a processor and a computer program which is stored on the memory and can run on the processor, wherein the processor executes the computer program to realize the steps of the method.
The invention also provides a readable storage medium, which stores a computer program, and the stored computer program is executed by a processor to realize the steps of the powder laying control method.
According to the powder paving control method, the powder paving control equipment and the readable storage medium, at least one intermediate image is obtained by calculating the difference value between the current layer image and at least one image stored in a database, and a result image is obtained after each intermediate image is subjected to corrosion treatment to remove noise and the normal sintering edge of a workpiece to be printed; on one hand, the invention solves the problem that the judgment is inaccurate due to the change of the optical environment caused by the dust falling on the lens, the scraper, the periphery of the cavity and the light source in the sintering process; on the other hand, the problem of inaccurate judgment caused by inconsistent optical reflectivities of different materials is effectively solved. Therefore, the invention is not only suitable for sintering of a single material, but also suitable for mixed sintering of a plurality of materials, and the invention has more accurate detection and simpler detection method.
Drawings
FIG. 1 is a flow chart of a method of controlling powder placement in accordance with an embodiment of the present invention;
FIG. 2 is a diagram of a normal powder state of the powder in one embodiment
FIG. 3 is a powder surface state diagram illustrating abnormal powder spreading in one embodiment;
FIG. 4 is an intermediate image in one embodiment;
FIG. 5 is a resulting image in one embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
As shown in fig. 1, the powder laying control method provided by the present application includes the following steps:
step S1, when a powder paving detection instruction is received, acquiring a current layer image of a working area through an optical camera;
in step S1, in the prior art, a powder paving detection instruction is generally sent when powder paving of the front layer is completed, but the present invention may also adopt the mode of the prior art, but as a preferred scheme of the present invention, powder paving is not completely completed, that is, when the powder paving device paves powder from one side of the working area to the other side and paves powder to the other side of the working area, the powder paving detection instruction is sent, specifically, the powder paving detection instruction can be sent to the upper computer by the PLC, so that the time that the powder paving device continuously moves from the other side of the working area to the powder feeding cylinder and returns to the other side of the working area can be saved, and further, the working efficiency is further improved.
In addition, the embodiment can be executed from a certain layer as required, for example, preferably, since the powder paving is not stable for a few layers, the execution can be started from the tenth layer generally, that is, the PLC sends a powder paving detection instruction to the upper computer, and of course, the execution can also be stopped as required.
Specifically, the specific arrangement position of the optical cameras is not limited in the present invention, and one or more optical cameras may be adopted according to actual needs, for example, when the working area is large and one optical camera cannot capture images of all the working areas, a plurality of optical cameras may be selected.
Preferably, the current layer image obtained in step S1 may be subjected to a graying process for subsequent analysis.
Step S2, calculating the difference between the current layer image and at least one image stored in the database to obtain at least one intermediate image, wherein each intermediate image displays all normal pixels and abnormal pixels obtained by calculating the difference between the current layer image and each stored image;
preferably, all the normal pixels and the abnormal pixels in the intermediate image are displayed after binarization processing, that is, the abnormal element is set to be the gray level 255, and the normal element is set to be the gray level 0.
In step S2, the first image stored in the database is an image with normal powder paving quality stored by the designer according to experiments, and the subsequent stored images are all images that are executed and stored by the present embodiment and satisfy the conditions, for example, when the powder paving is judged to be normal and the number of images stored in the database does not reach the maximum value (can be set to 10), the current layer image is stored in the database and is used as the last image stored in the database; or when the powder paving is judged to be normal and the number of the images stored in the database reaches the maximum value, storing the current layer image into the database as the last image stored in the database, and removing the first image stored in the database.
Specifically, in step S2, when there are a plurality of images stored in the database, the calculating the difference between the current layer image and the plurality of images stored in the database to obtain a plurality of intermediate images specifically includes:
respectively carrying out subtraction operation on the current layer image and each pixel point at the same position in each image stored in a database;
and taking the absolute value of the value obtained by the subtraction as a final value;
and when the final value is greater than the difference parameter, marking the pixel as an abnormal pixel, and when the final value is less than or equal to the difference parameter, marking the pixel as a normal pixel. The difference parameter may be determined by the designer from a number of experiments to determine a particular value.
Step S3, carrying out corrosion treatment on each intermediate image to remove noise and the normal sintering edge of the workpiece to be printed to obtain a result image;
specifically, the parameters used in the etching process in step S3 may be set according to the sintering material, the equipment hardware, and the workpiece shape, for example, odd rectangles such as 3 × 3, 5 × 5, or 7 × 7 may be used for etching. Since the specific manner of the etching process is known in the art, it is not described in detail in the present invention.
An intermediate image of an embodiment is shown in fig. 4, which is taken as an example and the resulting image is obtained by etching it to remove noise and normal sintered edges of the workpiece to be printed, as shown in fig. 5. The noise in step S3 mainly refers to image changes caused by hardware changes, such as changes in the optical environment caused by dust falling on the lens, the scraper, the periphery of the cavity, and the light source during the sintering process; the optical reflection degrees of different materials are not consistent, and the final obtained result image can judge whether the powder paving is abnormal or not by eliminating the normal differences and the differences caused by hardware.
Step S4, counting the number of all abnormal pixels in each result image, and selecting the maximum number value as a result value;
in step S4, the number of abnormal pixels included in each of all result images is counted, and a quantity value with the largest number of abnormal pixels is selected as a result value, and ten result images are taken as an example, and pixel points (i.e., abnormal pixels) with a gray scale value of 255 in the ten result images are counted respectively to obtain ten result values, and the largest result value is taken.
And step S5, judging the powder paving quality according to the result value, and judging whether powder needs to be paved again according to the powder paving quality.
In this step, two cases of abnormal or normal powder paving can be determined according to the powder paving quality, and preferably, in order to more accurately determine the powder paving quality and record the powder paving quality state in detail, this step may specifically include:
when the result value is less than or equal to the first preset value, judging that the powder spreading is normal (as shown in figure 2); when the powder paving is judged to be normal and the number of the images stored in the database does not reach the maximum value, storing the current layer image into the database and taking the current layer image as the last image stored in the database; or
And when the powder paving is judged to be normal and the number of the images stored in the database reaches the maximum value, storing the current layer image into the database as the last image stored in the database, and removing the first image stored in the database.
When the result value is larger than the first preset value and smaller than the second preset value, judging that the powder paving quality is poor; when the powder paving quality is not good enough, deleting the current layer image, namely not storing the layer image as a comparison image, or using the original ten layers of images for comparison, and then continuing sintering;
and when the result value is greater than or equal to the second preset value, judging that the powder spreading is abnormal (as shown in figure 3), and re-spreading the powder. And when the powder paving is abnormal, deleting the current layer image, and in the same way, not storing the layer image as a comparison image or using the original ten layers of images for comparison.
It can be understood that the first preset value and the second preset value are set by a designer according to specific situations, and it is required to satisfy that the first preset value is smaller than the second preset value.
Preferably, in order to save time and improve working efficiency, when the powder paving abnormality is judged and reaches the set times continuously, workpiece sintering is stopped, and an alarm is started to remind that the equipment has faults and needs manual maintenance.
The invention also provides a powder paving control device which comprises a memory, a processor and a computer program which is stored on the memory and can run on the processor, wherein the processor executes the computer program to realize the steps of the method of any one of the above embodiments.
The invention further provides a readable storage medium, which stores a computer program, and the stored computer program is executed by a processor to realize the steps of the powder laying control method according to any one of the above embodiments.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. A powder paving control method is characterized by comprising the following steps:
when a powder paving detection instruction is received, acquiring a current layer image of a working area through an optical camera;
performing difference calculation on the current layer image and at least one image stored in a database to obtain at least one intermediate image, wherein each intermediate image displays all normal pixels and abnormal pixels obtained by performing difference calculation on the current layer image and each stored image;
corroding each intermediate image to remove noise and a normal sintering edge of a workpiece to be printed to obtain a result image;
counting the number of all abnormal pixels in each result image, and selecting the maximum number value as a result value;
judging the powder paving quality according to the result value, and judging whether powder needs to be paved again according to the powder paving quality; wherein the content of the first and second substances,
when the powder paving is judged to be normal and the number of the images stored in the database does not reach the maximum value, storing the current layer image into the database and taking the current layer image as the last image stored in the database; or
When the powder paving is judged to be normal and the number of the images stored in the database reaches the maximum value, storing the current layer image into the database, taking the current layer image as the last image stored in the database, and simultaneously removing the first image stored in the database;
the first image stored in the database is an image of normal laydown quality stored by the designer based on experiments.
2. A dusting control method according to claim 1, characterised in that a dusting detection instruction is sent when the dusting device is dusting from one side of the working area to the other and to the other side of the working area.
3. A dusting control method according to claim 2 wherein all normal pixels and abnormal pixels in the intermediate image are displayed after binarization processing.
4. A powder paving control method as claimed in any one of claims 1 to 3, wherein judging the powder paving quality according to the result value, and judging whether powder paving is required again according to the powder paving quality specifically comprises:
when the result value is smaller than or equal to a first preset value, judging that the powder paving is normal;
when the result value is larger than the first preset value and smaller than the second preset value, judging that the powder paving quality is poor;
and when the result value is greater than or equal to the second preset value, judging that the powder spreading is abnormal, and spreading the powder again.
5. The powder paving control method according to claim 4, wherein when the powder paving quality is poor or the powder paving is abnormal, the current layer image is deleted.
6. A powder paving control method as claimed in claim 5, characterized in that when the powder paving is judged to be abnormal and the powder paving abnormality is continuously reached to a set number of times, the sintering of the workpiece is stopped and an alarm is started.
7. The dusting control method of claim 6, wherein, when the number of images stored in the database is several, calculating a difference between the current layer image and the number of images stored in the database to obtain a number of intermediate images specifically comprises:
respectively carrying out subtraction operation on the current layer image and each pixel point at the same position in each image stored in a database;
and taking the absolute value of the value obtained by the subtraction as a final value;
and when the final value is greater than the difference parameter, marking the pixel as an abnormal pixel, and when the final value is less than or equal to the difference parameter, marking the pixel as a normal pixel.
8. A dusting control apparatus comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the steps of the method according to any of claims 1-7 when executing the computer program.
9. A readable storage medium storing a computer program, wherein the stored computer program, when executed by a processor, performs the steps of the dusting control method according to any of claims 1-7.
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Address after: No. 181, Linyu Road, national high tech Industrial Development Zone, Changsha City, Hunan Province, 410205 Patentee after: Hunan Huashu High Tech Co.,Ltd. Address before: No. 181, Linyu Road, national high tech Industrial Development Zone, Changsha City, Hunan Province, 410205 Patentee before: HUNAN FARSOON HIGH-TECH Co.,Ltd. |