Methods for sensing gelation time and determining torque threshold

Abstract

A gelation time sensing device includes a stage, a stirring device, and an image capturing device. The device liquefies a powder to be tested using the stage, stirs the liquefied powder using the stirring device and senses the torque of stirring the liquefied powder, and captures an image of the liquefied powder using the image capturing device. The device then determines the gelation time of the powder based on a judgment criterion related to the torque and the image. A gelation time sensing method includes: liquefying a powder to be tested, stirring the liquefied powder, sensing the torque of stirring the liquefied powder, capturing an image of the liquefied powder, and determining the gelation time of the powder based on a judgment criterion related to the torque and the image. The judgment criterion may include a predetermined torque threshold and a predetermined area shrinkage rate threshold.

Description

Technical Field

[0001] This invention relates to a gelation time sensing device and method, particularly a sensing device and method for determining gelation time based on stirring torque and the area of ​​liquefied powder. This invention also relates to a sensing device and method for sensing the gelation time of an adhesive sheet, particularly a sensing device and method for sensing the gelation time of an adhesive sheet used on a copper foil substrate. Background Technology

[0002] In some copper clad laminate (CCL) manufacturing processes, an impregnation process is used to soak fiberglass cloth in adhesives of different formulations to form a prepreg (or adhesive sheet). The prepreg is then pressed onto copper foil to form the copper clad laminate. To provide a basis for setting process parameters when using the adhesive sheet later, its gelation time is tested after completion. Currently, gelation time is mostly determined manually. Generally, this method involves taking a scrap piece of the adhesive sheet, rubbing it together to produce powder, sieving it, and then placing 0.2 grams on a constant-temperature plate for heating. After standing for 20 seconds, the operator continuously stirs the powder on the constant-temperature plate with a stirring rod. The operator can visually observe the powder liquefying, then transforming into a viscous state, and finally agglomerating, thus manually determining its gelation time. However, in the aforementioned operations, only the heating of the constant temperature plate itself and the powder settling time can be objectively fixed. The remaining stages involve the operator's subjective judgment, affecting the determination of the gelation time. Even if standard operating procedures are used to regulate each stage, it is still difficult to eliminate or effectively reduce the operator's subjective influence, resulting in significant variations in the determined gelation time. For example, a sample size of 0.2 grams is too small; even a slight error in measurement can cause a considerable sample ratio error. It is difficult to manually distribute the powder evenly on the constant temperature plate, and it is also difficult to use the same stirring method (e.g., the stirring trajectory of the stirring rod, the size and range of the circles, etc.) to stir the powder (and the liquefied powder). The determination of gelation time is easily affected by environmental conditions, such as ambient light and the appearance of the constant temperature plate (e.g., residual impurities, color changes due to oxidation of the plate surface, etc.). Furthermore, the subjective influence of different operators on the determination of gelation time also varies. Summary of the Invention

[0003] In view of the problems in the prior art, one object of the present invention is to provide a gelation time sensing device that can automatically determine the gelation time in order to eliminate or effectively reduce the influence of operator subjectivity.

[0004] A gelation time sensing device according to the present invention includes a stage, a stirring device, an image capturing device, and a controller. The stage is used to hold the powder to be tested and heat it to liquefy it into a liquefied powder. The stirring device includes a stirring rod and a torque meter coupled to the stirring rod. The stirring rod stirs the liquefied powder, and the torque meter senses the torque exerted by the stirring rod on the liquefied powder. The image capturing device is positioned towards the stage to capture an image of the liquefied powder. The controller is electrically connected to the stirring device and the image capturing device, and the controller determines a gelation time of the powder based on a judgment criterion related to the torque and the image. Thus, the controlled operation of the gelation time sensing device itself eliminates or effectively reduces the influence of inconsistent operator operation on the gelation time judgment. Furthermore, the gelation time sensing device can determine the gelation time through objective torque sensing and the image of the liquefied powder, and can also eliminate or effectively reduce the influence of subjective operator judgment on the gelation time judgment.

[0005] Another objective of this invention is to provide a gelation time sensing method that can automatically determine the gelation time, thereby eliminating or effectively reducing the influence of operator subjectivity.

[0006] A gelation time sensing method according to the present invention includes the following steps: placing the powder to be tested on a stage; heating the stage to liquefy the powder into a liquefied powder; continuously stirring the liquefied powder with a stirring rod; periodically sensing the torque of the stirring rod stirring the liquefied powder with a torque meter; periodically capturing images of the liquefied powder with an image capturing device; and determining a gelation time of the powder based on a judgment criterion related to the torque and the images. Thus, the gelation time sensing method utilizes controlled device operation to eliminate or effectively reduce the influence of inconsistent operator operation on the gelation time judgment. Furthermore, the gelation time sensing method can determine the gelation time through objective torque sensing and images of the liquefied powder, and can also eliminate or effectively reduce the influence of operator subjective judgment on the gelation time judgment.

[0007] Another objective of this invention is to provide a torque threshold determination method for gelation time sensing, so as to eliminate or effectively reduce the influence of operator subjective judgment on gelation time determination.

[0008] A torque threshold determination method for gelation time sensing according to the present invention includes the following steps: placing a test powder on a stage; heating the stage to liquefy the test powder into a liquefied powder; continuously stirring the liquefied test powder with a stirring rod; sensing the torque of the stirring rod on the liquefied test powder with a torque meter and recording the torque versus time curve; recording a manually input provisional gelation time; and repeating the above steps multiple times to obtain multiple curves and multiple provisional gelation times, and calculating a predetermined threshold based on the multiple curves and the multiple provisional gelation times as the torque threshold. Therefore, this method provides an objective criterion for determining gelation time in gelation time sensing.

[0009] Another objective of this invention is to provide a method for determining the area shrinkage rate threshold for gelation time sensing, so as to eliminate or effectively reduce the influence of operator subjective judgment on gelation time judgment.

[0010] A method for determining an area shrinkage rate threshold for gelation time sensing according to the present invention includes the following steps: placing a test powder on a stage; heating the stage to liquefy the test powder into a liquefied test powder; continuously stirring the liquefied test powder with a stirring rod; periodically capturing images of the liquefied test powder with an image capturing device and recording the area versus time curve of the liquefied test powder in the images; recording a manually input provisional gelation time; and repeating the above steps multiple times to obtain multiple curves and multiple provisional gelation times, and calculating a predetermined threshold based on the multiple curves and the multiple provisional gelation times as the area shrinkage rate threshold. Therefore, this method provides an objective criterion for determining gelation time in gelation time sensing.

[0011] The advantages and spirit of the present invention can be further understood through the following detailed description of the invention and the accompanying drawings. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a gelation time sensing device according to an embodiment of the present invention.

[0013] Figure 2 for Figure 1 Functional block diagram of the gelation time sensing device.

[0014] Figure 3 This is a flowchart of a gelation time sensing method according to the present invention.

[0015] Figure 4 This is a flowchart of a gelation time sensing method according to an embodiment of the present invention.

[0016] Figure 5This is a flowchart of a torque threshold determination method for gelation time sensing according to the present invention.

[0017] Figure 6 According to Figure 5 A schematic diagram of the torque versus time curve obtained by the torque threshold determination method.

[0018] Figure 7 This is a flowchart of a method for determining an area shrinkage rate threshold for gelation time sensing according to the present invention.

[0019] Figure 8 According to Figure 7 A schematic diagram of the area versus time curve obtained by the method of determining the area shrinkage rate threshold.

[0020] Figure 9 for Figure 8 The curve of area versus time is calculated to obtain a schematic diagram of the curve of area shrinkage rate versus time.

[0021] The reference numerals in the attached figures are explained as follows:

[0022] 1: Gelatinization time sensing device

[0023] 12: Controller

[0024] 14: Platform

[0025] 16: Stirring device

[0026] 162: Stirring rod

[0027] 164: Torque meter

[0028] 18: Image capturing device

[0029] 182: Image Sensor

[0030] 184: Lighting device

[0031] 20: Laying device

[0032] 202: Rotary Arm

[0033] 204: Funnel

[0034] 3: Powder

[0035] t1, t2: time

[0036] S102, S104, S106a~c, S108, S202, S204, S206, S208, S210, S212a~b, S214, S216, S218, S302, S304, S306, S308, S310, S312, S402, S404, S406, S408, S410, S412: Implementation steps Detailed Implementation

[0037] Please see Figure 1 and Figure 2 A gelation time sensing device 1 according to an embodiment of the present invention includes a controller 12, a stage 14, a stirring device 16, and an image capturing device 18. The controller 12 is electrically connected to the stage 14, the stirring device 16, and the image capturing device 18 to control their operation. The stage 14 is used to hold the powder 3 to be tested and heat it to liquefy it into a liquefied powder (shown in the shaded area). Figure 1 (In the middle). The stirring device 16 includes a stirring rod 162 and a torque meter 164 coupled to the stirring rod 162. The stirring rod 162 stirs the liquefied powder 3, and the torque meter 164 senses the torque of the stirring rod 162 stirring the liquefied powder 3. The image capturing device 18 is positioned toward the stage 14 to capture an image of the liquefied powder 3. The controller 12 determines a gelation time of the powder 3 based on a judgment criterion related to the torque and the image. Since the stirring of the powder 3 (or the liquefied powder 3), the reading of the torque, and the judgment of the state of the liquefied powder 3 in the image are all performed by the gelation time sensing device 1, in principle, the aforementioned actions are objective relative to manual operation. Therefore, the subjective influence of the operator can be eliminated or effectively reduced, thereby solving the problem in the prior art where the subjective influence of manual operation and judgment of powder state on the gelation time can be effectively reduced. Furthermore, this judgment criterion is set based on the stirring torque and the image of the liquefied powder. Therefore, the gelation time sensing device 1 also objectively judges the gelation time of the liquefied powder 3 based on the sensed torque, the captured image, and the judgment criterion. In principle, as the liquefied powder 3 gradually gels, its stirring torque generally increases, and the area of ​​the liquefied powder 3 (in the image) generally decreases. Therefore, in practice, the judgment criterion may include the torque being greater than a predetermined threshold and the area shrinkage rate of the liquefied powder 3 in the image reaching a predetermined threshold.

[0038] In this embodiment, the stage 14 can be implemented as a plate with a heater (e.g., heating wire, heating rod, thermoelectric cooler, or a combination thereof) to provide a temperature-controlled stirring environment. In practice, the temperature of the stage 14 can be set according to the adhesive composition of the powder 3 or its testing specifications. The stirring device 16 generally achieves stirring of the powder 3 (or liquefied powder 3) by means of an eccentrically rotating stirring rod 162; in practice, the required stirring trajectory of the stirring rod 162 can be designed by a suitable mechanism (e.g., gear set, servo motor, etc.), which will not be elaborated further. In practice, the torque meter 164 can be incorporated into the mechanism of the rotating stirring rod 162, for example, by using a torque-controlled rotating mechanism.

[0039] The image capturing device 18 includes two image sensors 182 (e.g., CCD, CMOS, or other image-capturing elements) and two illumination devices 184 (e.g., LED, halogen lamps, etc.). The image sensors 182 are arranged opposite each other, which helps to capture a complete image of the liquefied powder 3. For example, one image sensor 182 may be blocked by the stirring rod 162 or other components and unable to capture a complete image of the liquefied powder 3, while the other image sensor 182 can capture a complete image of the liquefied powder 3; or, for example, each image sensor 182 captures an image of a portion of the liquefied powder 3 to combine into a complete image. In practice, fewer or more image sensors can also be provided; providing more image sensors helps to enhance the aforementioned effect. The lighting devices 184 are arranged opposite each other, which helps to provide sufficient illumination to the liquefied powder 3 to obtain a qualified image (for example, one lighting device 184 may be blocked by the stirring rod 162 or other components and cannot illuminate the entire liquefied powder 3, while the other image sensor 182 can illuminate the entire liquefied powder 3). In practice, fewer or more lighting devices can also be provided; providing more image sensors helps to enhance the aforementioned effect. Furthermore, the number of image sensors 182 and lighting devices 184 is not limited to the same. In addition, the image capturing device 18 is not located above the liquefied powder 3, which avoids the influence of gases that may escape from the liquefied powder 3.

[0040] In addition, in this embodiment, the gelation time sensing device 1 further includes a laying device 20, which is electrically connected to the controller 12. The laying device 20 includes a rotating arm 202 and a funnel 204 disposed on the rotating arm 202 (its hidden outline is shown in dashed lines). Figure 1(In the middle). By controlling the rotation of the rotating arm 202 via the controller 12, the funnel 204 can be moved to a position (e.g., below the stirring device 16) so that the powder 3 can be spread on the platform 14 in a similar distribution via the funnel 204, or the funnel 204 can be moved away from the position to avoid interfering with the operation of the stirring rod 162 or affecting the operation of other components (e.g., image capture, lighting, etc.). In practice, the rotating arm 202 can also be implemented as a telescopic arm, which can also achieve the aforementioned positioning and displacement functions of the funnel 204. In addition, in practice, the spreading device 20 can be equipped with a weight meter and a feeder (or a combination thereof) to automatically measure the required weight of powder 3 into the funnel 204. This can improve the accuracy of material extraction, eliminate the variation in material taking by the operator, and also help the gelation time sensing device 1 to objectively determine the gelation time of the powder 3.

[0041] Please see Figure 3 This is a flowchart of a gelation time sensing method according to the present invention. For ease of explanation, this gelation time sensing method uses the aforementioned gelation time sensing device 1; therefore, for a related description of the gelation time sensing device 1, please refer to the preceding text and related figures, and it will not be repeated here. Logically, in this gelation time sensing method, the powder 3 to be measured is placed on the stage 14, as shown in step S102; the stage 14 is heated to liquefy the powder 3 into a liquefied powder 3 (and refer to...). Figure 1 As shown in step S104. Next, the gelation time sensing method continuously stirs the liquefied powder 3 with a stirring rod 162 (as shown in step S106a), periodically senses the torque of the stirring rod 162 stirring the liquefied powder 3 with a torque meter 164 (as shown in step S106b), and periodically captures images of the liquefied powder 3 with an image capturing device 18 (as shown in step S106c). The gelation time sensing method determines a gelation time of the powder 3 based on a judgment criterion related to the torque and the image, as shown in step S108.

[0042] Please also refer to Figure 4In one embodiment, the gelation time sensing method moves the funnel 204 to a position (by controlling the rotation of the rotating arm 202), as shown in step S202; and then applies an appropriate amount of powder 3 onto the stage 14 through the funnel 204, as shown in step S204. The amount of powder 3 applied is, for example, but not limited to, 0.2 grams, and can be set according to the test specifications. Furthermore, the powder 3 can be obtained by rubbing a scrap piece from an adhesive sheet together; however, this is not a limitation in practice. Next, the gelation time sensing method moves the funnel 204 away from the position (or retracts the funnel 204), as shown in step S206; and waits 20 seconds to allow the powder 3 to liquefy into a liquefied powder 3, as shown in step S208. The aforementioned waiting time is set according to the test specifications and is not limited to 20 seconds. Furthermore, during the aforementioned waiting period, the stage 14 heats the powder 3 (the heating temperature is set according to its test specifications and can be controlled by the controller 12, for example, before step S204). Next, the gelation time sensing method controls the stirring rod 162 to start stirring the liquefied powder 3 (for example, lowering the stirring rod 162 and moving the stirring rod 162 along a predetermined stirring trajectory, for example, moving at a constant speed) and turns on the image capturing device 18, as shown in step S210.

[0043] Next, the gelation time sensing method controls the torque meter 164 to sense the torque of the stirring rod 162 stirring the liquefied powder 3 (e.g., receiving torque sensing signals from the torque meter 164 at a preset frequency), as shown in step S212a; and controls the image capturing device 18 to capture images of the liquefied powder 3 (e.g., simultaneously or at the same frequency receiving image signals from the image sensor 182), as shown in step S212b. The frequency of torque sensing and image capturing can be determined according to the required accuracy of the gelation time, for example, but not limited to 10 times per second (or a period of 0.1 seconds). The torque sensing signal is acquired from the shaft card via an RS485 interface (in practice, this depends on the control mechanism of the stirring device 16). Next, the gelation time sensing method determines whether the sensed torque and the state of the liquefied powder 3 in the captured image meet the determination criteria, as shown in step S214. Furthermore, in practice, the judgment criteria may include the torque being greater than a predetermined threshold and the area shrinkage rate of the liquefied powder 3 in the image reaching a predetermined threshold; this predetermined threshold can be determined by training the gelation time sensing device 1, which will be explained later. The area of ​​the liquefied powder 3 can be achieved through image recognition technology (e.g., including edge detection), which will not be elaborated further; the area shrinkage rate of the liquefied powder 3 can be determined by the difference between the area in the current image and the area in the previous image (e.g., defined as the ratio of the difference to the area in the current image).

[0044] When step S214 is determined to be True, the time at this point is set as the gelation time of powder 3, as shown in step S216. Then, step S218 is performed, raising the stirring rod 162 and cleaning the stage 14 (the surface supporting the powder 3, including removing residues from the gelation of the liquefied powder 3, oxides on the surface of the stage 14, etc.). After this, the gelation time sensing ends. In practice, step S218 can also be performed before or before step S202. Furthermore, in this embodiment, when step S214 is determined to be False, the process returns to steps S212a and S212b to again sense the torque of the stirring rod 162 stirring the liquefied powder 3 and capture an image of the liquefied powder 3, and then perform the determination in step S214 again; details are omitted here.

[0045] In this embodiment, depending on the actual configuration of the gelation time sensing device 1, the aforementioned process steps can be completed automatically by the gelation time sensing device 1, either completely or at least mostly. Therefore, the determination of the gelation time can eliminate or effectively reduce the subjective influence of the operator and improve the reliability of the gelation time.

[0046] Please see Figure 5 This is a flowchart of a torque threshold determination method for gelation time sensing according to the present invention. For ease of explanation, this torque threshold determination method is applicable to the aforementioned... Figure 3 , Figure 4 The gelation time sensing process is illustrated below. Therefore, for the relevant description of the gelation time sensing device 1, please refer to the preceding text and related diagrams, and it will not be repeated here. Logically, the torque threshold determination method places a test powder on the stage 14, as shown in step S302; wherein, the test powder has the same adhesive component as the aforementioned powder 3, therefore, for other descriptions regarding the placement, heating, stirring, and sensing of the test powder, please refer to the relevant description of powder 3, and it will not be repeated here. Next, the torque threshold determination method uses the stage 14 to heat and liquefy the test powder into a liquefied test powder, as shown in step S304; the liquefied test powder is continuously stirred with a stirring rod 162, as shown in step S306; the torque of the stirring rod 162 stirring the liquefied test powder is sensed by a torque meter 164 and the torque versus time curve is recorded (its appropriate value is as follows). Figure 6 As shown in step S308, a manually entered provisional gelation time (e.g.) is recorded. Figure 6 The process involves several steps, including step S310, to obtain multiple curves and provisional gelation times (each repetition requires sampling new test powder). A predetermined threshold (as the torque threshold) is then calculated based on these multiple curves and provisional gelation times, as shown in step S312. In practice, recording curve data stops when the liquefied test powder gels into clumps after stirring. The torque-time curve can be smoothed or fitted (e.g., ...). Figure 6 As shown, this is beneficial for data analysis. Furthermore, the predetermined threshold can be based on the peak values ​​of the multiple curves (e.g., Figure 6 The intermediate time t2) and the multiple provisional gelation times (e.g., time t2) Figure 6 The torque threshold is calculated using time t1; however, this invention is not limited thereto. Furthermore, this torque threshold determination method trains the gelation time sensing device 1 on a torque threshold basis; therefore, the aforementioned instructions for using the gelation time sensing device 1, which are applicable here, are also applicable and will not be repeated here. As mentioned above, the determination of this torque threshold is, in principle, objective; therefore, this method can provide an objective criterion for judging gelation time in gelation time sensing.

[0047] Please see Figure 7 This is a flowchart of a method for determining an area shrinkage rate threshold for gelation time sensing according to the present invention. For ease of explanation, this method for determining the area shrinkage rate threshold is applicable to the aforementioned... Figure 3 , Figure 4 The gelation time sensing process is illustrated below. Therefore, for the relevant description of the gelation time sensing device 1, please refer to the preceding text and related diagrams, and it will not be repeated here. Logically, the area shrinkage rate threshold determination method places a test powder on the stage 14, as shown in step S402. The test powder has the same adhesive component as the aforementioned powder 3. Therefore, for other descriptions regarding the placement, heating, stirring, and sensing of the test powder, please refer to the relevant description of powder 3, and it will not be repeated here. Next, the area shrinkage rate threshold determination method uses the stage 14 to heat and liquefy the test powder into a liquefied test powder, as shown in step S404. The liquefied test powder is continuously stirred with a stirring rod 162, as shown in step S406. The image capturing device 18 periodically (or at a frequency) captures images of the liquefied test powder and records the area versus time curve of the liquefied test powder in the image (as shown in the diagram). Figure 8 (The curves in the figure are only for qualitative display to facilitate explanation), as shown in step S408; record a manually input provisional gelation time (e.g. Figure 8 and Figure 9 As shown in step S410, the above steps are repeated multiple times to obtain multiple curves and multiple provisional gelation times (where a new sample of test powder is required for each repetition), and a predetermined threshold (as the area shrinkage rate threshold) is calculated based on the multiple curves and the multiple provisional gelation times, as shown in step S412. In practice, when the liquefied test powder gels into clumps after stirring, the recording of curve data can be stopped. The area-to-time curve can be smoothed or curve-fitted (e.g., ...). Figure 8 As shown, this is beneficial for data analysis. Furthermore, the area versus time curve can be calculated (e.g., by differentiation) to obtain the area shrinkage rate versus time curve, such as... Figure 9As shown; the predetermined threshold can be based on the peak value of the curve of the plurality of area shrinkage rates versus time (e.g., Figure 9 The intermediate time t2) and the multiple provisional gelation times (e.g., time t2) Figure 9 The area shrinkage rate threshold is calculated using time t1; however, this invention is not limited thereto. Furthermore, this method for determining the area shrinkage rate threshold trains the gelation time sensing device 1 on the area shrinkage rate threshold; therefore, the aforementioned instructions for using the gelation time sensing device 1, which are applicable here, are also applicable and will not be repeated here. Similarly, as mentioned above, the determination principle of this area shrinkage rate threshold is also objective; therefore, this method can also provide an objective criterion for judging gelation time in gelation time sensing.

[0048] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention should be included within the scope of the present invention.

Claims

1. A gelling time sensing device, comprising: A stage is used to hold the powder to be tested and heat it to liquefy it into a liquefied powder. A stirring device includes a stirring rod and a torque meter coupled to the stirring rod. The stirring rod stirs the liquefied powder, and the torque meter senses the torque of the stirring rod stirring the liquefied powder. An image capturing device is positioned facing the stage to capture an image of the liquefied powder; and A controller is electrically connected to the stirring device and the image capturing device. The controller determines the gelation time of the powder based on a judgment criterion related to the torque and the image.

2. The gelation time sensing device as claimed in claim 1, wherein the judgment criterion includes the torque being greater than a predetermined threshold.

3. The gelation time sensing device as claimed in claim 1, wherein the judgment criterion includes the area shrinkage rate of the liquefied powder in the image reaching a predetermined threshold.

4. The gelation time sensing device as claimed in claim 1 further includes a funnel through which the powder to be tested is placed on the stage.

5. The gelation time sensing device as claimed in claim 1, wherein the image capturing device comprises a plurality of image sensors.

6. A method for sensing gelation time, comprising the following steps: Place the powder to be tested on a stage; The powder is liquefied by heating the stage to form a liquefied powder. The liquefied powder was continuously stirred with a stirring rod; A torque meter is used to periodically sense the torque of the stirring rod when stirring the liquefied powder; The image capturing device periodically captures images of the liquefied powder; and The gelation time of the powder is determined based on a criterion related to the torque and the image.

7. The gelation time sensing method as described in claim 6, wherein the judgment criterion includes the torque being greater than a predetermined threshold.

8. The gelation time sensing method as described in claim 7, wherein the predetermined threshold is obtained by the following steps: A test powder is placed on the stage; The test powder was liquefied by heating the stage to form a liquefied test powder. The liquefied test powder was continuously stirred with the stirring rod; The torque meter is used to sense the torque of the stirring rod when stirring the liquefied test powder and the torque versus time curve is recorded. Record a manually entered provisional gelation time; as well as Repeat the above steps multiple times to obtain multiple curves and multiple provisional gelation times, and calculate the predetermined threshold based on the multiple curves and the multiple provisional gelation times.

9. The gelation time sensing method as claimed in claim 8, wherein the predetermined threshold is calculated based on the peak values ​​of the plurality of curves and the plurality of provisional gelation times.

10. The gelation time sensing method as described in claim 6, wherein the judgment criterion includes the area shrinkage rate of the liquefied powder in the image reaching a predetermined threshold.

11. The gelation time sensing method of claim 10, wherein the predetermined threshold is obtained by the following steps: A test powder is placed on the stage; The test powder was liquefied by heating the stage to form a liquefied test powder. The liquefied test powder was continuously stirred with the stirring rod; The image capturing device periodically captures images of the liquefied test powder and records the curve of the area of ​​the liquefied test powder in the image versus time. Record a manually entered provisional gelation time; and Repeat the above steps multiple times to obtain multiple curves and multiple provisional gelation times, and calculate the predetermined threshold based on the multiple curves and the multiple provisional gelation times.

12. The gelation time sensing method of claim 11, wherein the area versus time curve is calculated to obtain an area shrinkage rate versus time curve, and the predetermined threshold is calculated based on the peak values ​​of the plurality of area shrinkage rate versus time curves and the plurality of provisional gelation times.

13. The gelation time sensing method as described in claim 6, wherein the powder to be tested is laid on the stage through a funnel.

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