JP5728974B2 - Release agent coating apparatus and coating method - Google Patents

Description

  The present invention relates to a technique for efficiently applying a release agent to a mold.

  A mold release agent is applied to the casting mold to facilitate removal of the molded product from the mold. For example, Patent Document 1 and Patent Document 2 propose a device for applying a release agent without waste. Both Patent Document 1 and Patent Document 2 propose intermittent spraying of a release agent. In Patent Document 1, when a release agent is sprayed continuously from a plurality of nozzles, release agents sprayed from different nozzles interfere with each other, and a lot of the release agent scatters and does not reach the mold. In order to suppress this, it has been proposed to spray the release agent intermittently. In Patent Document 2, when a release agent is sprayed on a high-temperature mold, the release agent that has reached the mold first evaporates to form a vapor film near the mold surface, and the subsequent release agent mold It has been proposed to spray intermittently for the purpose of preventing the arrival at the water.

JP 59-189031 A JP 2005-7420 A

  In Patent Document 1 and Patent Document 2, although it is good to spray the mold release agent intermittently, a guideline on how much intermittent spraying should be based on what index is specific. Not shown. The present specification considers the reason why intermittent spraying is effective, and based on the results, provides a technique for efficiently applying a release agent by introducing a new index that has not existed in the past. .

According to the inventors' thought, when the release agent is sprayed continuously, a part of the release agent that has reached the mold surface rebounds, so that the subsequent release agent reaches the mold surface. Presumed to be inhibited. Therefore, it is considered that suppressing the rebound contributes to the efficient application of the release agent. As one way of thinking, if the size (particle diameter) of the sprayed release agent is reduced, the rebound can be suppressed. As another way of thinking, even if the spraying speed is slowed down, the rebound can be suppressed. For these reasons, the inventors focused on the total kinetic energy of the release agent sprayed per unit time on the unit area of the mold surface as a parameter depending on the size of the grains and the spraying speed. Hereinafter, “total kinetic energy” may be simply referred to as “kinetic energy”. The kinetic energy of each release agent is the product of the mass and the square of the velocity, and the particle size depends on the mass, so the kinetic energy depends on the spray velocity and the particle size. Therefore, the spray state for efficiently applying the release agent to the mold surface can be specified based on one index of the total kinetic energy of the release agent. In other words, efficient application is achieved by limiting the total kinetic energy of the release agent sprayed per unit time to a unit area of the mold surface to be equal to or lower than a predetermined upper limit value.

  One aspect of the coating apparatus disclosed in this specification is a nozzle capable of intermittently spraying a release agent, a period of intermittent spraying is T, and a ratio t / T of a spraying time t in the period T is set as T / T. A controller for controlling is provided. The controller has a rate t / T such that the kinetic energy of the release agent sprayed from the nozzle and sprayed per unit time on a unit area of the mold surface is less than or equal to a predetermined upper limit value. It is characterized by controlling. Hereinafter, for the sake of simplicity, “kinetic energy possessed by the release agent sprayed from the nozzle and sprayed per unit time on a unit area of the mold surface” will be referred to as “unit spray energy”. . The release agent may be either aqueous or oily. Alternatively, the release agent may be an emulsion (a dispersion solution in which both the dispersoid and the dispersion medium are liquid).

  Qualitatively, the smaller the distance between the nozzle and the mold surface (coating distance), the smaller the coating area. Therefore, when the distance between the nozzle and the mold surface is less than a predetermined distance, the controller It is preferable to reduce the ratio t / T as the distance decreases.

According to the study by the inventors, it was found that the upper limit value of the unit spray energy is specifically preferably 3000 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. In addition, since the ratio of the mold release agent which does not reach a metal mold | die will increase when unit spray energy is too low, it is also preferable to set the minimum value of unit spray energy. According to the study by the inventors, it has been found that the lower limit is preferably 70 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. That is, it is preferable that the coating apparatus controls the ratio t / T so that the unit spray energy is in a range between the upper limit value and the lower limit value.

  The phrase “spraying the release agent intermittently” can be said to spray the release agent in pulses. Therefore, in other words, the coating apparatus includes a nozzle that can spray the release agent in a pulsed manner, and a controller that controls t / T when the spraying cycle is T and the pulse width is t. Prepare. Further, from this, “the ratio t / T of the spraying time t to the intermittent spraying period T” corresponds to a so-called duty ratio. The fact that a suitable coating can be obtained within the above range will be specifically described in Examples.

  In order to apply the release agent to the surface of the mold, it is preferable to spray while moving the nozzle. Therefore, it is preferable that the coating apparatus includes a driving unit that moves the nozzle. At this time, it is preferable that the controller controls the ratio t / T so that the unit spray energy is between the upper limit value and the lower limit value while moving the nozzle relative to the mold.

  The driving means is, for example, a robot arm. Here, parameters such as the spraying speed (injection speed) of the release agent from the nozzle, the spray angle, the moving speed of the nozzle (may be the moving speed of the mold), and the distance from the nozzle to the mold are as follows: It can be set in advance. The unit spray energy is determined from these parameters. Therefore, the spray speed, spray angle, and arm tip trajectory (that is, the moving speed of the nozzle and the distance between the nozzle and the mold) are set in advance so that the unit spray energy is within the above range. The arm and nozzle may be operated according to the setting.

  The technology disclosed in this specification is also embodied in a method for applying a release agent. The method is such that the cycle is T and the spray time in the cycle T is t so that the unit spray energy of the release agent sprayed from the nozzle is equal to or lower than a predetermined upper limit value. T is determined and the release agent is sprayed intermittently. Further, it is preferable to spray intermittently so that the unit spray energy is between the above upper limit value and lower limit value.

  According to the present invention, the release agent can be efficiently sprayed on the surface of the mold.

It is a schematic diagram of a coating device. It is a figure explaining the relationship between an application range and a nozzle moving speed (1). It is a figure explaining the relationship between an application range and a nozzle moving speed (2). It is a figure explaining unit spray energy. It is a figure which shows the calculation result of unit spray energy. It is a table | surface which shows the influence on the coating amount waste by the coating distance and the kind of nozzle. It is a figure which shows the relationship between application distance and application amount waste. It is a graph which shows the relationship between responsiveness and application amount waste. It is a graph which shows the relationship between application distance and unit spray energy. It is a graph which shows the result of a mold release resistance test (1). It is a graph which shows the result of a mold release resistance test (2). It is a table | surface which shows the other advantage of the coating device (coating method) of an Example.

  In FIG. 1, the schematic diagram of the coating device 10 is shown. The coating apparatus 10 includes a robot arm 14 having a nozzle 12 attached to the tip, a supply device 16 for supplying a release agent to the nozzle 12, and a controller 18. In addition, the code | symbol 55 shown in FIG. 1 has shown the metal mold | die of the object sprayed with a mold release agent, and the code | symbol 55a has shown the metal mold | die surface which should spray a mold release agent. The mold surface 55a is typically a cavity surface.

  Usually, a release agent is applied to a high-temperature mold used for casting. That is, the mold release agent also serves as a mold cooling. The temperature of the mold when applying the release agent is 100 degrees or more.

  The supply device 16 can control the hydraulic pressure of the release agent sent to the nozzle 12. The nozzle 12 can spray the liquid mold release agent sent from the supply device 16, that is, inject in a mist form. Moreover, the nozzle 12 can spray a mold release agent intermittently. The nozzle 12 is moved with respect to the mold 55 by the robot arm 14. The controller 18 controls the liquid pressure of the release agent, the duty ratio of intermittent spraying (described later), the moving path and moving speed of the tip of the robot arm.

  The nozzle 12 can be exchanged between a type that sprays one fluid and a type that sprays two fluids. Here, “a type in which two fluids are sprayed” means a type in which two different types of fluids (for example, oil and air) are mixed and ejected.

  “Intermittently spraying” means spraying periodically and discretely in pulses. That is, after spraying the release agent continuously for t [sec (seconds)], repeating not spraying for Tt [sec]. In other words, it can be expressed that the release agent is sprayed in a pulse shape at a cycle T [sec] and a duty ratio t / T. Hereinafter, “t” may be referred to as a spraying time, and “T−t” may be referred to as a non-spraying time.

  When intermittently spraying the release agent while moving the nozzle 12, if the moving speed of the nozzle is too fast, or if the non-spray time (Tt) is too long, unevenness occurs in coating. The unevenness also depends on the application range. Therefore, the relationship between the spray range, the nozzle moving speed, and the intermittent application cycle T will be described next.

  FIG. 2 shows the relationship between the application range and the nozzle moving speed. Here, the range in which the release agent is sprayed onto the mold surface by spraying while the nozzle is stationary is referred to as a coating range. The application range is assumed to be circular. C1 and C2 in FIG. 2 indicate the application range. The diameters of the application ranges C1 and C2 are denoted by reference sign DL. The application range C1 indicates a range in which the release agent is applied in a certain moment. When the release agent is intermittently sprayed at the cycle T and the application time t, the application range C2 by the next spraying is formed at a position shifted by the distance dV after being sprayed to the application range C1 for a certain moment. Assuming that the nozzle moves at a speed Vs parallel to the mold surface, the distance dV between the centers of the two coating ranges C1 and C2 is dV = Vs × (T−t). Here, (Tt) is the non-application time as described above. Empirically, coating unevenness can be eliminated if the overlapping portion (distance indicated by LAP in FIG. 2) of two adjacent coating ranges C1 and C2 is more than half the diameter DL of the coating range. Then, it can be seen from FIG. 2 that when dV = LAP = DL / 2, the coating unevenness can be eliminated. On the other hand, since it can be considered that the upper limit value of the non-application time is the period T, it can be seen that the relationship shown in FIG. 3 is associated with the period T, the nozzle moving speed Vs, and the application range diameter DL. FIG. 3 is a graph showing the relationship between the coating range diameter DL satisfying LAP = DL / 2 and the nozzle moving speed Vs when the period T = 0.05 [sec] is assumed to be the maximum non-application time. For example, when the nozzle movement speed Vs is 1000 [mm / sec], the nozzle movement amount dV at the maximum non-application time (period T) = 0.05 [sec] is 50 [mm]. Since DL = LAP = 2dV, if the diameter DL of the application range is 100 [mm] or more, the overlapping portion LAP of the application ranges C1 and C2 becomes more than half of the diameter DL of the application range. In other words, coating unevenness can be eliminated by setting the nozzle movement speed Vs and the coating range diameter DL so as to be in the region above the graph of FIG. For example, when a nozzle having an intermittent spray period T = 0.05 [sec] is used and a release agent is sprayed onto the mold surface so that the coating range diameter DL is 100 [mm], the nozzle moving speed (metal mold) If the moving speed in the direction parallel to the mold surface (Vs) is set to 1000 [m / sec] or less, uneven coating can be prevented.

Next, the unit spray energy will be described with reference to FIG. As described above, the “unit spray energy” is the kinetic energy of the release agent sprayed from the nozzle 12 and is sprayed per unit time on the unit area of the mold surface 55a. . As shown in FIG. 4, the distance (application distance) between the nozzle 12 and the mold surface 55a is represented by a symbol Ls. Further, the spray angle of the nozzle 12 is represented by 2θs. At this time, the radius DL / 2 of the coating range can be expressed by Ls · tan (θs). That is, the coating area S = {Ls · tan (θs)} ² · π [cm ² ]. When the spray amount per second of the release agent is represented by M [g / sec] and the spray particle velocity is represented by v [cm / sec], the unit spray energy Es can be represented by the following (Equation 1). .

  FIG. 5 shows the relationship between the application distance (Ls in FIG. 4) and the unit spray energy Es when the cycle T = 50, 100, and 200 [msec]. FIG. 5 shows the result calculated by Equation 1 based on the result of actually spraying the release agent from the nozzle and measuring the ejection speed of the release agent droplet at that time with a laser velocimeter. Note that the vertical axis of the figure is a logarithmic scale. It can be seen that the unit spray energy gradually increases as the application distance becomes shorter. FIG. 5 shows the results for one fluid and two fluids.

  When the release agent is sprayed without moving the nozzle 12, the release agent sprayed first from the nozzle 12 rebounds on the mold surface and affects the subsequent release agent. FIG. 6 shows the results of an experiment examining the influence of the coating distance Ls and the type of nozzle. In FIG. 6, “grain velocity” is the velocity of the sprayed release agent droplets. The grain velocity was measured with a laser velocimeter. “No rebound time” means the time until the release agent sprayed from the nozzle reaches the mold. “Response” corresponds to the period T of intermittent application. The “bounce time” means a time affected by the bounce and corresponds to “response time−droplet arrival time”. The “influenced application amount” means an application amount that is affected by rebound from the mold surface when a 20 [ml (milliliter)] release agent is applied. 6 to 8 show results obtained by simulation. The upper seven rows in the table of FIG. 6 are the calculation results when using a nozzle that sprays two fluids, and the lower seven rows are the calculation results when using a nozzle that sprays one fluid.

  A nozzle selection method obtained from the simulation result will be described. Specifically, the amount of influence applied (the amount of application affected by the rebound from the mold surface when a 20 [ml (milliliter)] release agent is applied) is regarded as a waste application amount, and waste application. The nozzle response necessary to reduce the amount will be described. As a result of the simulation, it is understood that when the responsiveness (intermittent spray cycle T) is 500 [msec], about 50% of the sprayed release agent is wasted regardless of the nozzle and application distance. On the other hand, when the responsiveness (intermittent spray cycle T) is 10 [msec], it can be seen that there is almost no waste. Specifically, when the responsiveness is set to 10 [msec], the release agent that is wasted is 1% or less of the sprayed release agent amount (20 [ml]). For example, when the upper limit of the application amount waste is 2% of the spray amount, if a nozzle that sprays the release agent at 20 [ml / sec] is used, the application amount waste needs to be suppressed within 2 [ml]. From FIG. 6, it can be said that the period T of intermittent spraying is preferably at least 10 [msec] or less.

  FIG. 7 shows the relationship between the application distance and the application amount waste for some responsiveness. FIG. 7 shows the influence application amount (application amount affected by rebound) and distance when a release agent is applied at a flow rate of 50 [mm / sec] using a nozzle having an application amount of 20 [ml / sec]. This is derived from the nozzle response. From FIG. 7, it is possible to derive the responsiveness required to suppress the influence application amount to 10%, for example.

  FIG. 8 shows the relationship between the responsiveness and the influence application amount. From FIG. 8, for example, in order to keep the influence application amount within 2 [ml] (10% of the total application amount 20 [ml]) at an application distance of 50 mm, the responsiveness needs to be set to about 100 [msec] or less. I know that there is. It can be seen that in order to keep the influence coating amount within 2 [ml] at a coating distance of 350 mm, it is necessary to set the responsiveness to about 130 [msec] or less.

Next, the range of unit spray energy for efficiently applying the release agent will be described. FIG. 9 is a graph showing the relationship between unit spray energy and coating distance for each of the 1 fluid and 2 fluid. The upper limit value and the lower limit value in the graph are derived by testing with a Lub tester U (automatic tensile tester for aluminum die casting manufactured by Mec International Co., Ltd.). The upper limit value represents a limit at which the kinetic energy of the release agent to be sprayed is large and the solute (active ingredient) is caused to flow by the solvent, and the release agent after coating becomes thin. Specifically, the upper limit value is 3000 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. The lower limit value represents a limit where the kinetic energy of the released release agent is small and does not reach the mold surface even when sprayed from the nozzle. Specifically, the lower limit is 70 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. The square marker in FIG. 9 shows the result (in the case of two fluids) when the unit spray energy is limited to the upper limit value or less. The upper limit value and the lower limit value are obtained from FIG. The mold release resistance when continuously applied with a certain nozzle is minimized at an energy of 500 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. On the basis of the mold release resistance at this time, if the mold release resistance exceeds 20%, the product quality is remarkably deteriorated as a rule of thumb. From this, the upper limit value: 3000 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec] and the lower limit value: 70 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec] is determined.

In addition, a mold release resistance test was performed with the Lub tester U. The results are shown in FIGS. The test conditions are as follows. A nozzle for two fluids was used as a nozzle for spraying the release agent. The application conditions were 20 [ml / sec] for continuous spraying for 1 second (not intermittent spraying). The temperature of the object to be applied (metal body simulating a mold) is 100 degrees. As the release agent to be sprayed, an oily stock solution type was used. The graph of FIG. 10 has an inflection point at a coating distance of 200 [mm], and the mold release resistance increases regardless of whether the coating distance is far or near. FIG. 11 shows a comparison between the case of continuous application and the case of intermittent application. The marker marked with x indicates the case where intermittent application is performed. In intermittent application, the duty ratio was controlled so that the unit spray energy did not exceed the above-described upper limit value, that is, 3000 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. As described above, the duty ratio here means the duty ratio when the application time at the time of continuous application = T. As shown in the graph of FIG. 10, in the continuous application, the application area becomes smaller and the unit spray energy increases as the application distance becomes smaller. In intermittent spraying, the duty ratio is reduced as the coating distance decreases to keep the unit spray energy constant. That is, when the application distance is 200 [mm] or less, the controller 18 decreases the duty ratio as the application distance decreases. In other words, the controller 18 applies the application distance when the distance between the nozzle 12 and the mold surface 55a (application distance Ls) is equal to or less than a predetermined distance (in this embodiment, 200 mm or less). The duty ratio is decreased as Ls decreases. In this test, the energy increases as the coating distance becomes shorter and exceeds 500 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. Switching to duty ratio control. If the release resistance can be allowed to deteriorate by 20%, the spraying may be switched to intermittent spraying after the energy exceeds 3000 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec].

  In the case of continuous application, the reason why the release resistance increases when the application distance is 200 mm or less is estimated as follows. When an oil-based release agent is used, (a) the kinetic energy of the release agent is too large and the solute (active ingredient) is washed away by the solvent, resulting in a thin film; and (b) the solute is deposited. It is presumed that the mold release resistance increases due to vigorous gasification by the heat of the molten metal and vacuuming of the casting interface. When a water-soluble mold release agent is used, deposition is not a problem, but it is presumed that the mold release resistance increases in the same manner because the factor (a) and vaporization are inhibited.

  In FIG. 12, the other advantage of the coating device (coating method) of an Example is shown.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: coating device 12: nozzle 14: robot arm 16: supply device 18: controller 55: mold

Claims (10)

It is a coating device for coating the mold release agent on the mold surface,
A nozzle that can spray the release agent intermittently;
A controller for controlling the ratio t / T when the period of intermittent spraying is T and the spraying time of the period T is t;
The controller is equipped with
Application of the release agent, wherein the ratio t / T is controlled so that the total kinetic energy of the release agent sprayed per unit time on a unit area of the mold surface is less than or equal to a predetermined upper limit value. apparatus.   2. The coating apparatus according to claim 1, wherein when the distance between the nozzle and the mold surface is equal to or less than a predetermined distance, the controller decreases the ratio as the distance decreases. The coating apparatus according to claim 1, wherein the upper limit value is 3000 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. The controller controls the ratio t / T so that the total kinetic energy is equal to or higher than a lower limit of 70 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. Item 4. The coating apparatus according to Item 3. Drive means for moving the nozzle is provided, and the controller moves the nozzle relative to the mold while the ratio t / T so that the total kinetic energy is between the upper limit value and the lower limit value. The coating apparatus according to claim 4, wherein the coating apparatus is controlled. It is a method of applying a release agent to the mold surface,
As the total kinetic energy of the release agent which is sprayed per unit time per unit area of the total kinetic energy at a in the mold surface of the mold release agent which is sprayed from the nozzle is equal to or less than a predetermined upper limit value, the period Is defined as T, and the spraying time of the period T is defined as a ratio t / T, and the release agent is sprayed intermittently.   The coating method according to claim 6, wherein when the distance between the nozzle and the mold surface is equal to or less than a predetermined distance, the ratio is decreased as the distance decreases. The coating method according to claim 6, wherein the upper limit value is 3000 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. The mold release agent is sprayed intermittently so that the total kinetic energy is equal to or higher than a lower limit of 70 × 10 ³ [g · (cm / sec) ² / (cm) ² / sec]. 8. The coating method according to 8. The mold release agent is sprayed intermittently so that the total kinetic energy is between the upper limit value and the lower limit value while moving the nozzle relative to the mold. The coating method as described.

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