A quality monitoring device, method, and additive manufacturing equipment for laser sintering process

Abstract

A quality monitoring device, method, and additive manufacturing equipment for laser sintering process are disclosed. The device includes: a host computer that generates scanning data from the STL file of the part to be printed and sends it to a scanning control unit; a scanning control unit that generates laser switch command signals and laser power command signals based on the scanning data and sends them to the laser, and generates motion control commands and sends them to the scanning unit; and a timing acquisition, analysis, and logic judgment unit that acquires the actual output power signal from the laser in real time, as well as the laser switch command signals and laser power command signals sent to the laser by the scanning control unit, and determines whether the laser is working normally by comparing the actual output power signal, the laser switch command signal, and the laser power command signal, and alarms when the laser is malfunctioning. This invention provides more precise monitoring, recording laser power data down to each scanning line, providing detailed data for additive manufacturing equipment.

Description

Technical Field

[0001] This application relates to the field of additive manufacturing technology, and in particular to a quality monitoring device, method and additive manufacturing equipment for laser sintering process. Background Technology

[0002] Additive manufacturing is a rapid manufacturing technology that uses a laser to scan and stack layers to form a three-dimensional object. The process flow is as follows: First, the three-dimensional model of the part is sliced ​​to obtain the contour information of each layer. Powdered material is evenly spread on the surface of the work platform, and the laser selectively melts the powder according to system instructions. After one section is completed, a new layer of material is laid on top, and scanning continues selectively based on the cross-sectional information corresponding to the three-dimensional object. This process is repeated for the next section, ultimately resulting in the three-dimensional object.

[0003] In the aforementioned additive manufacturing technologies, the stability of the laser output power plays a decisive role in the sintering quality and the final success or failure of sintering. Current additive manufacturing equipment mostly monitors the laser's operational status, primarily checking for internal malfunctions. A few devices use optical power meters to collect partial laser power information through laser beam splitting, or directly sample the laser power from the optical power meter, reflecting the overall output power. However, this is limited by the optical power meter's response speed (generally requiring several seconds for data to stabilize) and the extremely fast scanning speed of the galvanometer (scanning short lines takes only milliseconds). Furthermore, the laser switches on and off at very high frequencies during 3D printing, making it difficult to truly match the real-time detection of the galvanometer scanning trajectory with the laser's output power using an optical power meter.

[0004] Furthermore, the current sintering construction records for additive manufacturing equipment do not contain records of laser output power accurate to each scan line during the sintering process.

[0005] These factors make it difficult to monitor and identify short-term anomalies in laser power during the sintering process in additive manufacturing equipment. Furthermore, the resulting sintering defects, due to the lack of recorded data, cannot be pinpointed after part processing, posing a risk to the successful fabrication of the part. Summary of the Invention

[0006] To address the aforementioned technical problems in the existing technology, this invention provides a laser sintering process quality monitoring device, method, and additive manufacturing equipment. This laser sintering process quality monitoring device provides more precise monitoring, and the monitoring can be accurate down to the laser power recording data of each scan line, providing detailed equipment construction process data for additive manufacturing equipment. This data can be used as a basis for evaluating the quality of manufactured parts.

[0007] To achieve the above objectives, the present invention provides a quality monitoring device for a laser sintering process, comprising:

[0008] The host computer is used to generate scanning data based on the STL file of the workpiece to be printed and send it to the scanning control unit;

[0009] The scanning control unit is used to generate laser switch command signals and laser power command signals based on the scanning data sent by the host computer and send them to the laser, as well as to generate motion control commands and send them to the scanning unit to control the laser and the scanning unit to work together; the laser has real-time laser power acquisition and data output functions.

[0010] The timing acquisition, analysis, and logic judgment unit is used to acquire the actual output power signal from the laser in real time, as well as the laser switch command signal and laser power command signal sent to the laser by the scanning control unit. It compares the actual output power signal, the laser switch command signal, and the laser power command signal to determine whether the laser is operating normally, and issues an alarm when the laser is malfunctioning.

[0011] The timing acquisition, analysis, and logic judgment unit is also used to generate laser power recording data corresponding to each scan line based on all the acquired and analyzed data, and to feed back all the acquired, analyzed, and generated data to the host computer for data processing and storage.

[0012] As a further preferred embodiment of the present invention, the acquisition frequency of the timing acquisition analysis and logic judgment unit is above 100KHz.

[0013] The present invention also provides a control method for a quality monitoring device in a laser sintering process, the control method comprising the following steps:

[0014] The host computer sends the scanning data of the current scan line to the scan control unit;

[0015] The scanning control unit generates laser switch command signal and laser power command signal based on the scanning data of the current scanning line sent by the host computer and sends them to the laser. It also generates motion control command and sends it to the scanning unit to control the laser and the scanning unit to work together.

[0016] The timing acquisition, analysis, and logic judgment unit acquires the actual output power signal from the laser, as well as the laser switch command signal and laser power command signal generated by the scanning control unit; and determines whether the laser operation of the current scan line is normal by comparing the actual output power signal, the laser switch command signal, and the laser power command signal.

[0017] An alarm will be triggered if the laser in the current scan line malfunctions.

[0018] As a further preferred embodiment of the present invention, when the actual output power signal matches the laser switch command signal and the laser power command signal, the laser is judged to be working normally; otherwise, the laser is judged to be working abnormally. The abnormal laser operation includes abnormal laser output, abnormal high laser output power, abnormal low laser output power, abnormal laser output time exceeding the time limit, abnormal laser output time being too short, and abnormal power signal of the scanning control unit.

[0019] As a further preferred embodiment of the present invention, when the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, the laser power command signal is power1, power1 is greater than 0, and the actual output power signal power2 is always 0, then it is determined that the laser is not emitting light abnormally.

[0020] As a further preferred embodiment of the present invention, when the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, the laser power command signal is power1, power1 is greater than 0, the actual output power signal power2 is greater than power1 and exceeds the allowable error, then it is judged that the laser output power is abnormally high.

[0021] As a further preferred embodiment of the present invention, when the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, the laser power command signal is power1, the actual output power signal power2 is less than power1 and exceeds the allowable error, and power2 is greater than 0, then it is determined that the laser output power is abnormally low.

[0022] As a further preferred embodiment of the present invention, when the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, and the duration of on is T1, T1 is greater than 0, and the duration of the actual output power signal power2 is T2, when T2 is greater than T1 and the difference exceeds the allowable error, it is determined that the laser output time has exceeded the alarm abnormality; when T2 is less than T1 and the difference exceeds the allowable error, it is determined that the laser output time is too short and the alarm abnormality is triggered.

[0023] As a further preferred embodiment of the present invention, when the scanning task of the current scan line is completed, if the laser switching command acquired by the timing acquisition analysis and logic judgment unit is on, then it is determined that the power signal of the scanning control unit is abnormal.

[0024] The present invention also provides an additive manufacturing equipment, including the laser sintering process quality monitoring device described above.

[0025] The laser sintering process quality monitoring device, method, and additive manufacturing equipment of the present invention, by adopting the above technical solutions, have the following beneficial technical effects:

[0026] 1. The laser of this invention has a real-time laser power acquisition and data output function (this function can be implemented by its internal components), and its acquisition speed is much faster than that of existing optical power meters. By acquiring the actual output power of the laser at high speed in real time and comparing it with the laser switch command signal and laser power command signal issued to the laser by the scanning control unit, it is possible to determine whether the laser's output timing and power meet the design requirements. When the laser's output power does not match the design value, or the output timing does not match the set value, an alarm can be triggered. Therefore, this device can effectively monitor sintering abnormalities caused by abnormal laser operation and promptly trigger alarms, thereby improving the success rate of part sintering and providing an effective monitoring method for the sintering process of additive manufacturing equipment. Moreover, the built-in high-speed device for acquiring the actual output power within the laser makes the comparison between the actual output power and the laser switch command signal and laser power command signal more accurate, thus improving the accuracy of monitoring.

[0027] 2. This application can mark each scan line of the part to be printed during the forming process and record its actual output power, laser switch command signal, and laser power command signal. This recorded data can be used for process quality backtracking to determine whether there are quality defects in the part. Furthermore, the laser power recording data generated by this application, accurate to each scan line, provides detailed equipment construction process data for additive manufacturing equipment. This data can assist in the evaluation of part quality monitoring and can also be used for data analysis and fault diagnosis by comparing with part quality defects, solving the problem of additive manufacturing equipment lacking high-precision, high-real-time laser power monitoring and data recording. Attached Figure Description

[0028] Figure 1 A schematic diagram of a structure of an embodiment of the laser sintering process quality monitoring device of the present invention;

[0029] Figure 2 A flowchart illustrating a method of the laser sintering process quality monitoring device of the present invention;

[0030] Figure 3 This is the processing principle of the timing acquisition analysis and logic judgment unit of the present invention. Figure 1 ;

[0031] Figure 4 This is the processing principle of the timing acquisition analysis and logic judgment unit of the present invention. Figure 2 .

[0032] Marked in the image:

[0033] 1. Host computer; 2. Scanning control unit; 3. Laser; 4. Scanning unit; 5. Timing acquisition, analysis and logic judgment unit. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] like Figure 1 As shown, the laser sintering process quality monitoring device of this utility model includes:

[0036] The host computer 1 is used to generate scanning data based on the STL file of the part to be printed and send it to the scanning control unit 2; specifically, it can send the scanning graphic trajectory and process data of each layer to the scanning control unit 2.

[0037] The scanning control unit 2 is used to generate laser switch command signals and laser power command signals based on the scanning data sent by the host computer 1 and send them to the laser 3, as well as to generate motion control commands and send them to the scanning unit 4, so as to control the laser 3 and the scanning unit 4 to work together. The laser 3 has a real-time laser power acquisition and data output function. Specifically, a photosensitive device can be set near the output end of the laser 3 to acquire the laser power signal of the laser 3, and the acquired laser power signal (also known as the actual output power signal) can be output to the external port of the laser 3. The delay of the actual output power signal output by the laser 3 relative to the laser output time is only on the order of microseconds, which can meet the requirements of real-time power acquisition. The scanning unit 4 can be a galvanometer system.

[0038] The laser power command is used to set the specific output power value of the laser 3, and the laser switch command is used to control the specific output time of the laser 3.

[0039] The timing acquisition, analysis, and logic judgment unit 5 is used to acquire in real time the actual output power signal from the laser 3, as well as the laser switch command signal and laser power command signal sent to the laser 3 by the scanning control unit 2. It then compares the actual output power signal, the laser switch command signal, and the laser power command signal to determine whether the laser is working normally, and issues an alarm when the laser is malfunctioning.

[0040] The timing acquisition, analysis and logic judgment unit 5 is also used to generate laser power recording data corresponding to each scan line based on all the above-mentioned acquired and analyzed data, and to feed back all the acquired, analyzed and generated data to the host computer 1 for data processing and storage.

[0041] During the 3D printing process, the laser 3 is in a high-speed switching state, and the frequency of the switching light can reach more than 10KHz. In order to further ensure the accuracy of the collected data and not miss the switching light conditions of the laser 3 in a very short time, the acquisition frequency of the timing acquisition analysis and logic judgment unit 5 is more than 100KHz.

[0042] Specifically, when the actual output power of laser 3 matches the laser switch command signal and laser power command signal sent by the scanning control unit 2, the laser is considered to be working normally; otherwise, it is considered abnormal, and an alarm is triggered when the laser is abnormal. Furthermore, when the output time of laser 3 is consistent with the switch command sent by the scanning control unit 2, and the output power value of laser 3 is consistent with the laser power command sent by the scanning control unit 2, the actual output power of laser 3 is considered to match the laser switch command signal and laser power command signal sent by the scanning control unit 2, meaning the laser is working normally. Here, consistency includes the difference between the two being within the allowable error range. The specific value of the allowable error can be determined by the designer based on industry common sense and will not be detailed here.

[0043] like Figure 2 As shown, the present invention also provides a control method for a quality monitoring device in a laser sintering process, the control method comprising the following steps:

[0044] Step 21: The host computer 1 sends the scanning data of the current scan line to the scan control unit 2;

[0045] Step 22: The scanning control unit 2 generates a laser switch command signal and a laser power command signal based on the scanning data of the current scanning line sent by the host computer 1 and sends them to the laser 3. It also generates a motion control command and sends it to the scanning unit 4 to control the laser 3 and the scanning unit 4 to work together.

[0046] Step 23: The timing acquisition analysis and logic judgment unit 5 acquires the actual output power signal of the laser 3, scans the laser switch command signal and laser power command signal generated by the control unit 2; and judges whether the laser of the current scan line is working normally by comparing the actual output power signal (also known as the laser power signal), the laser switch command signal and the laser power command signal; specifically, when the actual output power signal matches the laser switch command signal and the laser power command signal, it is judged that the laser is working normally, otherwise it is judged that the laser is working abnormally.

[0047] Step 24: When the laser of the current scan line malfunctions, an alarm will be triggered.

[0048] To enable those skilled in the art to better understand the specific processing principle of the timing acquisition analysis and logic judgment unit 5 in this application, the following will be combined with... Figure 3 and Figure 4 To elaborate in detail.

[0049] Figure 3 This provides a schematic diagram of the data processing principle of the timing acquisition analysis and logic judgment unit 5 for a single scan line; Figure 4 This provides a schematic diagram of the data processing principle performed by the timing acquisition analysis and logic judgment unit 5 on all scan lines of the current layer. For example... Figure 3 As shown, when the laser switch command from the scanning control unit 2 changes from off to on (generally from a low-level signal to a high-level signal), the laser 3 theoretically begins to emit light, at time t1. The timing acquisition, analysis, and logic judgment unit 5 simultaneously acquires the laser power command from the scanning control unit 2 and records the laser power as power1. It also monitors the actual output power signal from the laser 3; the moment this signal changes from low to high is recorded as t2. At this point, the laser 3 truly begins to emit light, and the acquired signal is converted into the actual output power value of the laser 3, power2. When the laser 3 turns off its laser output, the timing acquisition, analysis, and logic judgment unit 5 first acquires the laser switching command from the scanning control unit 2 changing from on to off (generally from a high-level signal to a low-level signal), recording this moment as t3. Then, the timing acquisition, analysis, and logic judgment unit 5 monitors the actual output power signal from the laser 3 changing from high to low, and the laser 3's output power decreases from power2 to 0, recording this moment as t4.

[0050] The timing acquisition, analysis, and logic judgment unit 5 records the above data and performs real-time data analysis. First, it compares the light emission command duration T1 = t3 - t1 with the actual light emission time T2 = t4 - t2. Due to inherent errors in data acquisition, when the error between T2 and T1 is less than the set allowable error ΔT, the light emission duration is deemed to meet the requirements. This allowable error needs to be combined with the actual sintering process parameters and verified. Throughout the entire light emission time, the timing acquisition, analysis, and logic judgment unit 5 acquires and records the power signal power1 from the scanning control unit 2 and the actual light emission power signal power2 from the laser 3 in real time. It compares the error between the two; if the error is within the allowable error ΔP, the actual light emission power of the laser 3 is deemed to meet the requirements. This allowable error also needs to be combined with the actual sintering process parameters and verified. The timing acquisition analysis and logic judgment unit 5 feeds back the acquired light emission time and actual light emission power data to the host computer 1 for storage, and feeds back the judgment results to the host computer 1. The judgment results may include alarms such as laser not emitting light, high laser emission power, low laser emission power, laser emission time exceeding the time limit, laser emission time being too short, and scanning control unit power signal alarm.

[0051] The above-mentioned abnormal situations are specifically determined in the following ways:

[0052] When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit 5 is on, the laser power command signal is power1, power1 is greater than 0, and the actual output power signal power2 is always 0, then it is determined that the laser is not emitting light, which is abnormal.

[0053] When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit 5 is on, the laser power command signal is power1, power1 is greater than 0, the actual output power signal power2 is greater than power1 and exceeds the allowable error, then it is judged that the laser output power is abnormally high.

[0054] When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit 5 is on, the laser power command signal is power1, the actual output power signal power2 is less than power1 and exceeds the allowable error, and power2 is greater than 0, then it is judged that the laser output power is abnormally low.

[0055] When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit 5 is on, and the duration of on is T1, T1 is greater than 0, and the duration of the actual output power signal power2 is T2, if T2 is greater than T1 and the difference exceeds the allowable error, the laser output time is judged to be out of time and an alarm is triggered; if T2 is less than T1 and the difference exceeds the allowable error, the laser output time is judged to be too short and an alarm is triggered.

[0056] When the scanning task of the current scan line is completed, if the laser switching command acquired by the timing acquisition analysis and logic judgment unit 5 is on, then the power signal of the scanning control unit is judged to be abnormal.

[0057] See Figure 4 As shown, during the sintering process of the additive manufacturing equipment, the host computer 1 first completes the slicing task of the next layer's scanning pattern according to the STL file of the part to be printed, decomposing the sintering task of the next layer into numerous scanning lines, and finally generating each scanning command. After the additive manufacturing equipment completes the powder spreading operation and enters the construction of the next layer, when the timing acquisition analysis and logic judgment unit 5 detects that the laser switch command signal from the scanning control unit 2 changes from off to on, it begins to mark and record the arrival of the first scanning command of this layer, corresponding to the first scanning line line-1. When the laser switch command signal changes from on to off, the scanning of this scanning line is completed, and the scanning of line-1 ends. During the continuous scanning time of line-1, the timing acquisition analysis and logic judgment unit 5 acquires and records the actual light output power from the laser 3, and uploads the duration T-1 of the actual light output power and the specific value PL-1 of the actual light output power of the laser 3 to the host computer 1, and simultaneously sends the laser power command PC-1 from the scanning control unit 2 to the host computer 1. The host computer 1 stores the above data of line-1.

[0058] When the timing acquisition analysis and logic judgment unit 5 acquires the laser switch command signal from the scanning control unit 2 again, changing from off to on, the second scanning line begins to scan and is marked as line-2. When the laser switch command signal changes from on to off, the line-2 scan is completed, and so on until the last scanning line of the current layer, line-n.

[0059] After the additive manufacturing equipment completes sintering, the host computer 1 can integrate the actual light output power data and light output duration data of all scan lines with the part to be printed to form a record of sintering data. This record can be used to query the actual light output of each scan line of the part to be printed, and can ultimately be used to determine the sintering quality of the part to be printed and locate faults and defects.

[0060] The present invention also provides an additive manufacturing apparatus, including the laser sintering process quality monitoring device described in any of the above embodiments.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A device for monitoring the quality of a laser sintering process, characterized in that include: The host computer is used to generate scanning data based on the STL file of the workpiece to be printed and send it to the scanning control unit; The scanning control unit is used to generate laser switch command signals and laser power command signals based on the scanning data sent by the host computer and send them to the laser, as well as to generate motion control commands and send them to the scanning unit to control the laser and the scanning unit to work together; the laser has real-time laser power acquisition and data output functions. The timing acquisition, analysis, and logic judgment unit is used to acquire the actual output power signal from the laser in real time, as well as the laser switch command signal and laser power command signal sent to the laser by the scanning control unit. It compares the actual output power signal, the laser switch command signal, and the laser power command signal to determine whether the laser is operating normally, and issues an alarm when the laser is malfunctioning. The timing acquisition, analysis, and logic judgment unit is also used to generate laser power recording data corresponding to each scan line based on all the acquired and analyzed data, and to feed back all the acquired, analyzed, and generated data to the host computer for data processing and storage.

2. The apparatus of claim 1, wherein, The acquisition frequency of the timing acquisition analysis and logic judgment unit is above 100KHz.

3. A control method of the laser sintering process quality monitoring apparatus according to claim 1 or 2, characterized in that, The control method includes the following steps: The host computer sends the scanning data of the current scan line to the scan control unit; The scanning control unit generates laser switch command signal and laser power command signal based on the scanning data of the current scanning line sent by the host computer and sends them to the laser. It also generates motion control command and sends it to the scanning unit to control the laser and the scanning unit to work together. The timing acquisition, analysis, and logic judgment unit acquires the actual output power signal from the laser, as well as the laser switch command signal and laser power command signal generated by the scanning control unit; and determines whether the laser operation of the current scan line is normal by comparing the actual output power signal, the laser switch command signal, and the laser power command signal. An alarm will be triggered if the laser in the current scan line malfunctions.

4. The control method according to claim 3, characterized by If the actual output power signal matches the laser switch command signal and the laser power command signal, the laser is considered to be working normally; otherwise, the laser is considered to be working abnormally. The abnormal laser operation includes laser not emitting light, laser output power being high, laser output power being low, laser output time exceeding the time limit, laser output time being too short, and scanning control unit power signal being abnormal.

5. The control method according to claim 4, characterized by When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, the laser power command signal is power1, power1 is greater than 0, and the actual output power signal power2 is always 0, then it is determined that the laser is not emitting light, which is abnormal.

6. The control method according to claim 4, characterized by When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, the laser power command signal is power1, power1 is greater than 0, and the actual output power signal power2 is greater than power1 and exceeds the allowable error, then it is judged that the laser output power is abnormally high.

7. The control method according to claim 4, characterized by When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, the laser power command signal is power1, the actual output power signal power2 is less than power1 and exceeds the allowable error, and power2 is greater than 0, then it is judged that the laser output power is abnormally low.

8. The control method according to claim 4, characterized in that, When the laser switch command signal acquired by the timing acquisition analysis and logic judgment unit is on, and the duration of on is T1, T1 is greater than 0, and the duration of the actual output power signal power2 is T2, if T2 is greater than T1 and the difference exceeds the allowable error, the laser output time is judged to be out of time and an alarm is triggered; if T2 is less than T1 and the difference exceeds the allowable error, the laser output time is judged to be too short and an alarm is triggered.

9. The control method according to claim 4, characterized in that, Once the scanning task for the current scan line is completed, if the laser switching command acquired by the timing acquisition analysis and logic judgment unit is "on", then the power signal of the scanning control unit is determined to be abnormal.

10. An additive manufacturing apparatus, characterized in that, Includes the laser sintering process quality monitoring device as described in claim 1 or 2.

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