CN114273678A - Online monitoring device for laser selective melting forming process splashing based on acoustic signals - Google Patents
Online monitoring device for laser selective melting forming process splashing based on acoustic signals Download PDFInfo
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- CN114273678A CN114273678A CN202111654071.XA CN202111654071A CN114273678A CN 114273678 A CN114273678 A CN 114273678A CN 202111654071 A CN202111654071 A CN 202111654071A CN 114273678 A CN114273678 A CN 114273678A
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Abstract
The invention discloses an online monitoring device for splashing in a selective laser melting forming process based on acoustic signals, which comprises a processing chamber, wherein a static focusing mirror is arranged in the middle of the upper chamber wall of the processing chamber, a vibrating mirror is arranged above the static focusing mirror, a laser is arranged on the right side of the vibrating mirror, a forming cylinder is arranged in the middle of the lower chamber wall of the processing chamber, a lifting table is arranged in the forming cylinder, a base plate is arranged in the middle of the upper surface of the lifting table, and formed parts are placed on the base plate; a powder cylinder and a powder spreading device are arranged in the processing chamber; and an acoustic sensor is arranged at the left position of the forming cylinder in the processing chamber and is connected with an acoustic signal acquisition system positioned outside the processing chamber. The invention collects the data of the splash phenomenon in the selective laser melting and forming process in real time through the acoustic sensor, transmits the collected data to the acoustic signal collector, transmits the signals to the computer through the acoustic signal collector, processes the data on the computer, and accurately extracts the characteristic frequency of the splash phenomenon.
Description
Technical Field
The invention relates to the field of additive manufacturing, in particular to an online monitoring device for spattering in a selective laser melting forming process based on acoustic signals.
Background
Additive manufacturing is a process of manufacturing parts by way of material build-up based on three-dimensional model data. The Selective Laser Melting (SLM) technology has the advantages of high cooling efficiency, high energy density, high forming precision and the like, can accurately form metal functional parts with high density and good mechanical properties and in any shapes, is a metal additive manufacturing process with the widest application range and the greatest practical significance at present, is considered to be one of additive manufacturing technologies with the greatest application prospect, and is applied to the fields of aerospace, medical instruments and the like. Although the SLM technology is more and more widely applied and can directly realize metal parts with complex shapes and light weight, various process defects such as pores, slag inclusion, spheroidization, cracks and the like still occur in the SLM forming process.
Spattering is an important phenomenon during laser and powder action. The metal powder is liquefied and gasified under the radiation action of laser to form a micro molten pool, the melt in the micro molten pool system has escape behavior under the recoil pressure and the Marangoni effect, and the powder around the molten pool forms a solid-liquid molten state under the entrainment action of metal vapor in the micro molten pool system. On one hand, when the splash falls into a processing area, the high-energy laser beam cannot completely melt the splash, so that defects such as holes, slag inclusion and the like are easily caused, and the forming quality and the mechanical property of a formed part are influenced; on the other hand, when the spatter falls into the unprocessed metal powder, not only the metal powder is contaminated to cause waste of the material, but also the next powder spreading effect is affected. Spatter is also a direct manifestation of the processing conditions. The splash contains more abundant information and can represent the process state. The sputtering can be quantitatively analyzed from the angles of sputtering direction, angle, area and the like. The characteristic of the spatter has a certain relation with the forming quality of the final part, and the characteristic can be used for dynamic monitoring of the machining quality as long as the rule is found. The spatter is an important clue for analyzing various process defects in the SLM forming process and an important signal to be monitored in the forming process, so that research on spatter behavior is necessary. The research on the splashing mechanism is helpful for deeply understanding the SLM forming process, provides a feasible method for monitoring the machining process, can solve the reliability problem of the SLM machining process, and finally improves the product quality and reduces the manufacturing cost.
The splashing behavior in the SLM additive manufacturing process is accompanied by the generation and variation of signals such as sound, light (heat) radiation, acoustic emission, etc. Because the particles that splash have the characteristics of visibility, therefore to the on-line monitoring of phenomenon of splashing, carry out real-time supervision for CCD camera mostly, but in the SLM course of working, can produce a large amount of smog in the processing chamber, under raise dust and smog environment, the phenomenon of splashing in the SLM shaping process will be difficult to the complete true show of CCD camera, and the algorithm of processing image data in real time still can not satisfy the requirement of on-line monitoring simultaneously. Therefore, the CCD camera is difficult to meet the requirement of monitoring the splashing phenomenon on line in the SLM material increase manufacturing process. The sound signal on-line monitoring splashing phenomenon is successfully applied to the field of welding, so that the sound signal monitoring has a better application prospect in the selective laser melting technology. Meanwhile, the acoustic signal sensor is small in size, low in position requirement and easy to build a monitoring system, and can meet the requirement of real-time monitoring of the splashing phenomenon in the SLM forming process.
Disclosure of Invention
In order to solve the technical problem, the invention provides the on-line monitoring device for the spattering in the selective laser melting forming process based on the acoustic signal, which has a simple structure and works reliably.
The technical scheme for solving the technical problems is as follows: an online monitoring device for splashing in a selective laser melting forming process based on acoustic signals comprises a processing chamber, an acoustic sensor, an acoustic signal acquisition system, a protective gas circulation system and a forming cylinder, wherein a static focusing lens is arranged in the middle of the upper chamber wall of the processing chamber, a vibrating lens is arranged above the static focusing lens, a laser is arranged on the right side of the vibrating lens, a forming cylinder is arranged in the middle of the lower chamber wall of the processing chamber, a lifting table is arranged in the forming cylinder, a substrate is arranged in the middle of the upper surface of the lifting table, a laser beam emitted by the laser irradiates onto the substrate through the vibrating lens and the static focusing lens, and a forming part is placed on the substrate; a protective gas circulating system is arranged on the rear chamber wall of the processing chamber; a powder cylinder and a powder paving device for paving metal powder in the powder cylinder on a formed part are arranged at the right side of the forming cylinder in the processing chamber; and an acoustic sensor is arranged at the left position of the forming cylinder in the processing chamber and is connected with an acoustic signal acquisition system positioned outside the processing chamber.
According to the device for monitoring splashing in the selective laser melting forming process based on the acoustic signal, the protective gas circulating system comprises a protective gas inlet and a protective gas outlet which are arranged on the rear wall of the processing chamber, protective gas enters the processing chamber through the protective gas inlet and then is discharged from the protective gas outlet, and the processing chamber is kept in a low-oxygen state.
Above-mentioned online monitoring device that selective laser melting forming process splashes based on acoustic signal, the machining room left side room wall is provided with the through-hole, and acoustic sensor passes the through-hole through signal transmission line and connects acoustic signal acquisition system, and two semicircle rubbers of signal transmission line outside parcel block up the through-hole, and semicircle rubber is sealed with the plasticine at both ends, guarantees to be in the low oxygen environment in the machining room.
Above-mentioned online monitoring device that selective laser melting forming process splashes based on acoustic signal, acoustic sensor passes through the mount to be fixed on the locular wall under the processing chamber, and the mount includes base and fixing device, and the base is fixed on the locular wall under the processing chamber, and fixing device is including the semicircle buckle of installing two concatenations on the base, and acoustic sensor places in two semicircle buckles, and semicircle buckle both sides are equipped with the screw that is used for the fastening.
According to the online monitoring device for the laser selective melting forming process splashing based on the acoustic signal, the residual powder cylinder is arranged between the forming cylinder and the fixing frame.
The powder spreading device comprises a powder spreading brush, a powder spreading brush sliding rail and a driving mechanism, the powder spreading brush sliding rail is arranged on the rear chamber wall of the processing chamber, the powder spreading brush is slidably arranged on the powder spreading brush sliding rail, the driving mechanism used for driving the powder spreading brush to reciprocate on the powder spreading brush sliding rail is arranged on the rear chamber wall of the processing chamber, and metal powder exceeding the powder cylinder is uniformly spread on the forming cylinder.
According to the online monitoring device for the laser selective melting forming process splashing based on the acoustic signal, the acoustic signal acquisition system comprises an acoustic signal collector and a computer, the computer is connected with the acoustic sensor through the acoustic signal collector, and the acoustic signal collector is used for reducing noise of data monitored by the acoustic sensor in real time and then sending the data into the computer.
According to the online monitoring device for the laser selective melting forming process splashing based on the acoustic signal, the vibrating mirror, the static focusing mirror and the forming part are located on the same vertical plane.
The invention has the beneficial effects that: when the device prints layer by a laser, the acoustic sensor is used for collecting the data of the splash phenomenon in the selective laser melting and forming process in real time, the collected data are transmitted to the acoustic signal collector, the acoustic signal collector transmits signals to the computer, the data are processed on the computer, the characteristic frequency of the splash phenomenon is accurately extracted, the adjustment of the processing parameters in the selective laser melting process is guided according to the amplitude of the extracted characteristic frequency of the splash phenomenon, the quality of the formed part in the selective laser melting process is improved, and the dynamic monitoring of the splash phenomenon in the selective laser melting process is realized. The advantage of the invention of real-time monitoring by means of the acoustic sensor is that firstly, in a completely closed and sound-proof processing chamber, the influence of external environmental noise on the acoustic signal is reduced; secondly, the volume of the acoustic signal sensor is small, the position requirement is not high, and the monitoring system is easy to build; finally, the cost of the acoustic sensor is low.
Drawings
Fig. 1 is a schematic view of the overall structure of the present invention.
Fig. 2 is a schematic view of the installation position of the acoustic sensor of the present invention.
FIG. 3 is a schematic view of a through hole in the left chamber wall of a processing chamber according to the present invention.
Detailed Description
The invention is further described below with reference to the figures and examples.
As shown in fig. 1-3, an online monitoring device for splash during selective laser melting forming process based on acoustic signals comprises a processing chamber 21, an acoustic sensor 17, an acoustic signal acquisition system, a protective gas circulation system and a forming cylinder 11, wherein a static focusing lens 4 is arranged in the middle of the upper chamber wall of the processing chamber 21, a vibrating lens 2 is arranged above the static focusing lens 4, a laser 1 is arranged on the right side of the vibrating lens 2, the forming cylinder 11 is arranged in the middle of the lower chamber wall of the processing chamber 21, a lifting table 14 is arranged in the forming cylinder 11, a substrate 12 is arranged in the middle of the upper surface of the lifting table 14, a laser beam 3 emitted by the laser 1 irradiates the substrate 12 through the vibrating lens 2 and the static focusing lens 4, forming parts are placed on the substrate 12, and the vibrating lens 2, the static focusing lens 4 and the forming parts 13 are located on the same vertical plane; a protective gas circulating system is arranged on the rear chamber wall of the processing chamber 21; a powder cylinder 15 and a powder laying device for laying the metal powder 8 in the powder cylinder 15 on the formed part 13 are arranged at the right position of the forming cylinder 11 in the processing chamber 21; an acoustic sensor 17 is arranged in the processing chamber 21 at the left side of the forming cylinder 11, and the acoustic sensor 17 is connected with an acoustic signal acquisition system positioned outside the processing chamber 21.
The protective gas circulation system comprises a protective gas inlet 6 and a protective gas outlet 5 which are arranged on the rear chamber wall of the processing chamber 21, protective gas enters the processing chamber 21 through the protective gas inlet 6 and then is discharged from the protective gas outlet 5, and the interior of the processing chamber 21 is kept in a low-oxygen state, so that the generation of splashing 7 is reduced.
The processing chamber 21 left side locellus wall is provided with through-hole 22, and acoustic sensor 17 passes through-hole 22 through signal transmission line 23 and connects the acoustic signal collection system, and signal transmission line 23 outside parcel two semicircle rubber 24 block up through-hole 22, and semicircle rubber 24 both ends are sealed with the plasticine, guarantee to be in sealed environment in the processing chamber 21.
The acoustic sensor 17 is fixed on the lower chamber wall of the processing chamber 21 through the fixing frame 18, the fixing frame 18 comprises a base 25 and a fixing device, the base 25 is fixed on the lower chamber wall of the processing chamber 21, the fixing device comprises two spliced semicircular buckles 26 installed on the base 25, the acoustic sensor 17 is placed in the two semicircular buckles, and screws used for fastening are arranged on two sides of the semicircular buckles 26.
A residual powder cylinder 16 is arranged between the forming cylinder 11 and a fixed frame 18.
After the formed part 13 is processed for a layer thickness, the metal powder 8 in the powder cylinder 15 is uniformly pushed into the forming cylinder 11 for a layer thickness by the powder spreading device, the formed part 13 is covered, and the next processing is continued. The powder spreading device comprises a powder spreading brush 9, a powder spreading brush slide rail 10 and a driving mechanism, the powder spreading brush slide rail 10 is arranged on the rear chamber wall of the processing chamber 21, the powder spreading brush 9 can be slidably arranged on the powder spreading brush slide rail 10, the driving mechanism for driving the powder spreading brush 9 to reciprocate on the powder spreading brush slide rail 10 is arranged on the rear chamber wall of the processing chamber 21, and metal powder 8 which exceeds the powder cylinder 15 is uniformly spread on the forming cylinder 11.
The acoustic signal acquisition system comprises an acoustic signal collector 19 and a computer 20, the computer 20 is connected with the acoustic sensor 17 through the acoustic signal collector 19, the acoustic signal collector 19 carries out noise reduction on data monitored by the acoustic sensor 17 in real time and then sends the data into the computer 20, and the computer 20 is used for carrying out characteristic extraction of a splash 7 phenomenon on the data subjected to noise reduction by the acoustic signal collector 19. Separating background noise signals, sound signals of the splashing phenomenon under different laser powers and sound signals of the splashing phenomenon under different scanning speeds in the selective laser melting process by using a blind source separation algorithm, and taking the background noise sound signals as a reference to separate effective sound signals of the splashing phenomenon from complex background noise; and optimizing the VMD algorithm by utilizing a particle swarm algorithm, carrying out next-step processing on the extracted acoustic signal characteristic frequency band of the splash phenomenon, extracting a main splash phenomenon characteristic frequency band in the selective laser melting and forming process, and guiding the selection of processing parameters in the selective laser melting and forming process through the amplitude of the separated acoustic signal characteristic frequency band of the splash phenomenon, thereby effectively realizing the online monitoring of the splash phenomenon in the selective laser melting and forming process.
The working process of the invention is as follows:
first, the powder spreading brush 9 spreads a layer of metal powder 8 in the powder cylinder 15 and covers the substrate 12 in the forming cylinder 11, the metal powder 8 is uniformly distributed on the substrate 12 in the forming cylinder 11 and on the lifting table 14, and the excess metal powder 8 is stored in the residual powder cylinder 16. When the front processing is ready, the laser 1 starts to work, the galvanometer 2 and the static focusing mirror 4 are controlled according to a part scanning path which is ready to be set, the laser beam 3 irradiates on the metal powder 8 above the substrate 12 to form a metal molten pool through the reflection of the galvanometer 2 and the static focusing mirror 4, and the metal molten pool is combined with the uppermost layer of the formed part 13 on the substrate 12 in a solidification mode. After the laser beam 3 scans the forming cylinder 11 once, the lifting platform 14 correspondingly descends one thickness set by the forming part 13, the powder cylinder 15 correspondingly raises three to four thicknesses set by the forming part 13, and the powder spreading is waited for the next time, so that the reciprocating processing is carried out in a circulating mode until the part processing is completed. Finally, the protective gas enters the processing chamber 21 from the protective gas inlet 6 to insulate oxygen and is discharged from the protective gas outlet 5, so that lower oxygen content is maintained in the forming cavity, and the generation of splashing 7 is reduced.
Claims (8)
1. An online monitoring device for splashing in a selective laser melting forming process based on acoustic signals is characterized by comprising a processing chamber, an acoustic sensor, an acoustic signal acquisition system, a protective gas circulation system and a forming cylinder, wherein a static focusing mirror is arranged in the middle of the upper chamber wall of the processing chamber, a vibrating mirror is arranged above the static focusing mirror, a laser is arranged on the right side of the vibrating mirror, a forming cylinder is arranged in the middle of the lower chamber wall of the processing chamber, a lifting table is arranged in the forming cylinder, a substrate is arranged in the middle of the upper surface of the lifting table, a laser beam emitted by the laser irradiates the substrate through the vibrating mirror and the static focusing mirror, and a forming part is placed on the substrate; a protective gas circulating system is arranged on the rear chamber wall of the processing chamber; a powder cylinder and a powder paving device for paving metal powder in the powder cylinder on a formed part are arranged at the right side of the forming cylinder in the processing chamber; and an acoustic sensor is arranged at the left position of the forming cylinder in the processing chamber and is connected with an acoustic signal acquisition system positioned outside the processing chamber.
2. The apparatus of claim 1, wherein the shielding gas circulation system comprises a shielding gas inlet and a shielding gas outlet disposed on a rear chamber wall of the process chamber, wherein the shielding gas is introduced into the process chamber through the shielding gas inlet and then removed from the shielding gas outlet to maintain the interior of the process chamber in a low oxygen state.
3. The device for on-line monitoring of splashing in the selective laser melting forming process based on the acoustic signal as claimed in claim 1, wherein a through hole is formed in the left chamber wall of the processing chamber, the acoustic sensor passes through the through hole through a signal transmission line to be connected with the acoustic signal acquisition system, two semicircular rubbers wrapped outside the signal transmission line block the through hole, and the two ends of the semicircular rubbers are sealed by rubber clay to ensure that the processing chamber is in a low oxygen environment.
4. The online monitoring device for the spatter generated in the selective laser melting and forming process based on the acoustic signal as claimed in claim 1, wherein the acoustic sensor is fixed on the lower chamber wall of the processing chamber through a fixing frame, the fixing frame comprises a base and a fixing device, the base is fixed on the lower chamber wall of the processing chamber, the fixing device comprises two semicircular buckles which are installed on the base and spliced, the acoustic sensor is placed in the two semicircular buckles, and screws for fastening are arranged on two sides of the semicircular buckle.
5. The device for on-line monitoring of spatter generated during selective laser melting forming process based on acoustic signals as claimed in claim 4, wherein a residual powder cylinder is arranged between the forming cylinder and the fixed frame.
6. The online monitor device for spatter generated in selective laser melting forming process based on acoustic signal as claimed in claim 1, wherein: the powder spreading device comprises a powder spreading brush, a powder spreading sliding rail and a driving mechanism, the powder spreading sliding rail is arranged on the rear chamber wall of the processing chamber, the powder spreading brush can be slidably arranged on the powder spreading sliding rail, the driving mechanism used for driving the powder spreading brush to reciprocate on the powder spreading sliding rail is arranged on the rear chamber wall of the processing chamber, and metal powder exceeding the powder cylinder is uniformly spread on the forming cylinder.
7. The online monitor device for spatter generated in selective laser melting forming process based on acoustic signal as claimed in claim 1, wherein: the sound signal acquisition system comprises a sound signal collector and a computer, the computer is connected with the sound sensor through the sound signal collector, and the sound signal collector is used for reducing noise of data monitored by the sound sensor in real time and then sending the data into the computer.
8. The online monitor device for spatter generated in selective laser melting forming process based on acoustic signal as claimed in claim 1, wherein: the vibrating mirror, the static focusing mirror and the forming part are positioned on the same vertical plane.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111654071.XA CN114273678A (en) | 2021-12-31 | 2021-12-31 | Online monitoring device for laser selective melting forming process splashing based on acoustic signals |
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| CN202111654071.XA CN114273678A (en) | 2021-12-31 | 2021-12-31 | Online monitoring device for laser selective melting forming process splashing based on acoustic signals |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116890122A (en) * | 2023-09-11 | 2023-10-17 | 中国地质大学（武汉） | Full-period in-situ monitoring method for splash formation, emission and fall back in laser additive manufacturing |
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- 2021-12-31 CN CN202111654071.XA patent/CN114273678A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116890122A (en) * | 2023-09-11 | 2023-10-17 | 中国地质大学（武汉） | Full-period in-situ monitoring method for splash formation, emission and fall back in laser additive manufacturing |
| CN116890122B (en) * | 2023-09-11 | 2023-11-14 | 中国地质大学（武汉） | Full-period in-situ monitoring method for splash formation, emission and fall back in laser additive manufacturing |
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