JP2021185037A - Hot plate - Google Patents

Abstract

To provide a hot plate having excellent durability and a method for molding a three-dimensional molding using the same.SOLUTION: A hot plate 15 comprises a rectangular insulation substrate 151 and a heating resistor layer 152 that is folded back plural times in a short direction to be formed on the insulation substrate 151 in a zigzag shape, and a polar alternation voltage is applied to the heating resistor layer 152.SELECTED DRAWING: Figure 3

Description

The present invention relates to a heating plate suitable for on-demand heating, and more particularly to a heating plate suitable for on-demand heating by an AC voltage.

In recent years, a three-dimensional model has been actively manufactured by a three-dimensional printer using a computer. The Fused Deposition Modeling Method (FDM) is well known as a main modeling method using such a three-dimensional printer. As a hot end (discharge head) used in this type of 3D printer, the applicant has previously formed a heating plate in which a heat generating resistor (layer) is formed on an insulating substrate as a heating means for melting a modeling material. (Patent Document 1).

This hot end can significantly reduce the size and energy of a hot end using a conventional heat block as a heating means, and also enables on-demand modeling.

Japanese Unexamined Patent Publication No. 2018-66056

However, when the hot end for a three-dimensional printer is heated using a heating plate, a direct current voltage (DC) generally applied to the heating resistor is applied, but the heating plate continues to be heated at a high temperature of 400 ° C. or higher. Then, a phenomenon may occur in which the resistance value of the heat-generating resistor changes significantly.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a heating plate excellent in on-demand heating and durability even when heated to a high temperature and used.

As a result of diligent research to achieve the above object, the present inventor shows that the change in the resistance value of the above-mentioned heat-generating resistor is such that the insulation resistor becomes closer to the conductor at high temperature, and when DC is applied, it becomes the insulation resistor. It is thought that the cause is that the leakage current increases, the movement of the charged body increases, and the charged body moves unevenly and concentrates in one direction. It has been found that the change in the resistance value of the heat-generating resistor can be suppressed by applying an AC voltage to the heat-generating resistor so that the charged body of the body moves in one direction and does not concentrate.

That is, the present invention relates to a heating plate characterized by having a rectangular insulating substrate and a heat generating resistor layer formed on the insulating substrate by being folded back in a plurality of directions in a zigzag shape. .. The heating plate may be for a polar alternating voltage (alternating current voltage).

In the present invention, the polar alternating voltage means a voltage in which the positive and negative polarities change periodically or aperiodically. The polar alternating voltage is not limited to a sine wave, but may include a pulse wave, a square wave, a triangular wave, a sawtooth wave, and the like. Such a polar alternating voltage can be applied, for example, by converting a DC voltage into an AC with a DC / AC inverter. The AC voltage is modulated by PFM (pulse frequency modulation), PWM (pulse width modulation), or the like, and the power supplied to the heat generation resistor layer can be adjusted. According to the above-mentioned three-dimensional printer of the present invention, since the AC voltage is applied to the heat generation resistor layer, the resistance value of the heat generation resistor layer changes significantly even if heat generation to 400 ° C. or higher is repeated. It is possible to reduce the amount of heat generated and significantly improve the durability of the hot end. This is because impurities in the heat-generating resistor layer when a voltage is applied and charged elements (ions, electrons) can move in a well-balanced manner, and impurities due to movable charges that are thought to occur when heating is applied by applying a DC voltage. This is thought to be because it is possible to prevent the occurrence of electrolytic corrosion due to concentration of movement.

Further, the heating plate may have an insulating protective plate that covers the heat generation resistor layer.

As the insulating protective plate, it is preferable to use one having the same thickness as the insulating substrate, and it is preferable to have the same thermal expansion coefficient as the insulating substrate. By using the insulating protective plate, the heat generation resistor layer can be further stabilized, and the durability of the hot end can be further improved.

Further, by applying the polar alternating voltage, the heating plate can generate heat of 400 ° C. or higher.

Since the heating plate can be shaped at a high temperature of 400 ° C. or higher, for example, high melting point thermoplastic resins such as PEEK and filler-containing PEEK, Pb, Al, Sn, Ag, Cu, In, aluminum alloys, etc. Metals such as zinc alloys, low melting point glass and the like can be used as modeling materials. Further, for example, it is possible to perform three-dimensional modeling using a plurality of types of modeling materials having different melting temperatures, such as enabling simultaneous use of high-temperature and low-temperature materials.

Further, it is possible to provide a modeling method for modeling a three-dimensional model using the heating plate and a material that is heated and melted at 400 ° C. or higher as the modeling material.

According to the above-mentioned modeling method, three-dimensional modeling using a high-temperature material can be advantageously performed.

According to the present invention, it is possible to provide a heating plate having excellent on-demand heating and durability. Further, it is possible to provide a three-dimensional printer and a modeling method capable of improving the durability of the hot end and repeatedly performing modeling work at a high temperature.

It is (A) front view and (B) side view of the hot end in the 3D printer of one Embodiment of this invention. It is (A) front view and (B) bottom view of the head body of the hot end in the 3D printer of one Embodiment of this invention. A partial front view of the hot end in the three-dimensional printer according to the embodiment of the present invention, which is a heating plate as a heating means, and a cross-sectional view taken along the line BB of (A). Is. It is a circuit block diagram explaining the control of voltage application by a voltage application means. It is a figure which shows the specific structure of the conversion apparatus included in the adjustment part in the circuit block diagram of FIG.

Hereinafter, a hot end for a three-dimensional modeling apparatus (three-dimensional printer) according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 (A) shows a front view of the hot end 10, which is an example of the hot end used in the three-dimensional printer of the present invention, and FIG. 1 (B) shows a side view of the hot end 10. FIG. A) shows a front view of the head main body 1, and FIG. 2B shows a bottom view of the head main body 1. The hot end 10 has a supply unit 11 having a filament-shaped modeling material supply port 111, a melting unit 13 for melting the supplied filament-shaped modeling material, and a discharge unit having a discharge port 141 for discharging the melted modeling material. 14, a heat insulating section 12 between the supply section 11 and the melting section 13 that suppresses the heat of the melting section 13 from being conducted to the supply section 11, and a passage 2 that communicates the supply port 111 and the discharge port 141. The head body 1 is provided with a heating plate 15 which is a heating means for heating the melting portion 13 and a temperature adjusting portion 16 at or near the boundary portion between the melting portion 13 and the heat insulating portion 12. In the illustrated example, a pair of heating plates 15 are provided so as to be in contact with both facing surfaces of the melting portion 13 of the head body 1 so as to sandwich the head body 1, but the heating plates 15 are provided on only one of them. May be done. In FIGS. 1A and 1B, the heating plate 15 is a component thereof, and the heat generation resistor 152, the electrode 153, the intermediate terminal 153c, the sealing material 154, and the insulating protective plate 155 (see FIG. 3) are It is omitted, and in FIG. 1 (B), the lead 150 (see FIG. 1 (A)) is omitted.

The hot end 10 may be attached to a 3D printer or a module device for a 3D printer via an adapter (not shown). For example, the supply unit 11 of the hot end 10 is inserted into the opening provided in the adapter and can be fixed by a set screw or the like. The adapter is provided with a passage communicating with the supply port 111, and the filament-shaped modeling material is inserted into the flow path (passage) 2 of the hot end 10 through this passage. It is also possible to cut a thread groove on the outer circumference of the supply unit 11 and attach it to the adapter by screwing.

Subsequently, the head body 1 will be described in detail. FIG. 2A shows a front view of the head main body 1, and FIG. 2B shows a bottom view of the head main body 1. The head body 1 may have a supply unit 11, a heat insulating unit 12, a melting unit 13, and a discharging unit 14 integrally formed of a heat-resistant material such as metal or ceramics, or a part or all of the head body 1. It may be formed independently, or it may be discontinuous, such as interposing another member between any or all of the parts. In the illustrated example, the head body 1 is a columnar metal rod having a total length of, for example, 32 mm and a diameter of, for example, 4 mmφ, made of, for example, 64 titanium (an alloy of titanium mixed with 6% by mass of aluminum and 4% by mass of vanadium). For example, it is made by cutting.

The head body 1 is formed with a passage (through hole) 2 having a diameter of, for example, 2 mmφ extending in a straight line from the filament supply port 111 on one end side to the discharge port 141 for discharging the melted modeling material on the other end side. There is. The sizes of the head body 1 and the passage 2 can be appropriately changed according to the size of the filament.

The supply portion 11 of the head body 1 has, for example, a cylindrical shape (cylindrical shape) having a length of 5 mm and a diameter of 4 mmφ. The supply port 11 has a supply port 111 formed at the tip thereof, and for example, a passage 2 having a diameter of 2 mmφ is formed in a tapered shape so as to expand toward the supply port 111 side in the vicinity of the supply port 111, for example, to 3 mmφ. The supply unit 11 also serves as a mounting unit for an adapter (not shown) for mounting on a three-dimensional printer.

The heat insulating portion 12 is formed so as to have a higher thermal resistance than the melting portion 13, and in the illustrated example, the heat insulating portion 12 is located between the supply portion 11 and the melting portion 13, and has, for example, a length. It has a cylindrical shape (cylindrical shape) with a diameter of 11 mm and a diameter of 3 mmφ. As described above, the heat insulating portion 12 has a diameter of 3 mmφ, and since a passage 2 having a diameter of 2 mmφ penetrating the central portion thereof is formed, the heat insulating portion 12 is a thin portion having a wall thickness of 0.5 mm. Further, in the central portion of the heat insulating portion 12, for example, an opening 121 having a length of 8 mm and a width of 1.8 mm, which can reduce the cross-sectional area of the heat insulating portion 12 to increase its thermal resistance, faces the passage 2. It can be formed in pairs. One or a plurality of openings 121 may be provided in the length direction and / or the width direction of the head body 1, and the size may be appropriately determined. The cross-sectional area can be appropriately determined in relation to the thermal resistance within the range where the strength is guaranteed.

The melting portion 13 has, for example, a length of 13 mm and a diameter of 4 mmφ. The flat surface side (front surface side of the paper surface in FIG. 2A) and the back surface side (back surface side of the paper surface in FIG. 2A) are cut into the melting portion 13, and the two flat surface portions face each other with a distance of, for example, 3 mm. It is formed to do. In the central portion of the flat surface portion, for example, an opening 131 having a length of 8 mm and a width of 1 mm is formed so as to expose the passage 2. A plurality of openings 131 may be arranged side by side in the length direction. In addition, the surface of the flat surface portion may be roughened, or the surface of the flat surface portion may be only roughened without forming the opening 131. Further, in the vicinity of the discharge portion 14 of the melting portion 13, the passage 2 is narrowed in a taper shape toward the discharge portion 14, and has a diameter of, for example, about 0.6 mmφ in the discharge portion 14.

The discharge portion 14 has a length of, for example, 3 mm, is cut from the front side and the back side, has a width of, for example, 3 mm, and is tapered toward the discharge port 141 halfway in the length direction of the discharge portion 14. The tip portion on which the discharge port 141 is formed has a diameter of, for example, 1.5 mmφ, and the discharge port 141 has a diameter of, for example, 0.6 mmφ.

As a heating means for heating the melting portion 13 in the hot end 10, for example, a heating plate (heating head) having a thick film resistor layer formed on an insulating substrate, a heat block, or the like can be widely used. It is preferable to use a heating plate in terms of responsiveness and size. FIG. 3 shows an example of the structure of the heating plate 15 used for the hot end 10 of the present embodiment. As shown in the plan view of FIG. 3A, the heating plate 15 attached to the melting portion 13 of the head body 1 is, for example, a rectangular plate-shaped alumina or zirconia having a thickness of 0.3 mm, a length of 12 mm, and a width of 5 mm. , Or a ceramic substrate (insulated substrate 151) such as a composite material thereof, a band-shaped heat-generating resistor (layer) 152 formed on the surface of the insulating substrate 151, for example, a heat-generating resistor (layer) 152 having a thickness of 20 μm, and heat-generating resistance on the surface of the insulating substrate 151. It has electrodes 153 formed to connect to each of both ends of the body 152. An intermediate terminal 153c may be provided at an intermediate portion between the two electrodes 153 in the heat generation resistor 152. The intermediate terminal 153c is provided to enable partial voltage application in the heat generation resistor 152, which makes it possible to make the temperature different (form a temperature gradient) depending on the portion of the heating plate 15. For example, it is possible to control the temperature so that the temperature on the side close to the discharge portion 14 of the heating plate 15 is higher than the temperature on the side close to the heat insulating portion 12.

Although omitted in the plan view of FIG. 3A, as shown in the cross-sectional view of FIG. 3B, the heat generation resistor 152 is covered with the heat generation resistor 152 so as to cover the heat generation resistor 152. A ceramic substrate (insulation protective plate 155) such as a rectangular plate-shaped alumina having a thickness of 0.3 mm is attached via the glass-like sealing material 154. Instead of the sealing material (protective layer) 154 and the insulating protective plate 155, the surface of the heat generation resistor 152 may be coated with a protective layer (dielectric layer) such as glass containing a filler, for example.

In the present embodiment, 96% of Nikko Corporation's commercially available alumina zirconia substrate Alza (registered trademark), which is a commercially available Nikko Co., Ltd. alumina zirconia substrate as the insulating substrate 151, is attached to the upper part of the insulating protective plate 155, which is a commercially available Nikko Corporation alumina zirconia substrate. Alumina substrates are used, but it is preferable that these thicknesses are about the same. The mechanical strength of the alumina zirconia substrate is about twice as strong as that of the 96% alumina substrate. The volume resistivity of these substrates is ^{about 10 14 Ω · cm at room temperature and about 10 10} Ω · cm at 500 ° C. Glassy sealing material 154 is a commercially available quartz glass system, the volume resistivity is about 10 ⁹ Ω · cm at 300 ° C.. Further, the coefficient of thermal expansion of the alumina zirconia substrate is ^{about 7.0 × 10 -6} / ° C. at 25 to 400 ° C. and about 8.1 × 10 ^-6 / ° C. at 25 to 800 ° C. The coefficient of thermal expansion of the 96% alumina substrate is ^{about 6.8 × 10 -6} / ° C at 25-400 ° C and about 7.8 × 10 ^-6 / ° C at 25-800 ° C, which is almost the same as that of the alumina zirconia substrate. It is considered to be equivalent.

The heating plate 15 is a heat-generating resistor made by printing, for example, an alloy powder such as Ag, Pd, Pt, or a thick film paste containing ruthenium oxide on an insulating substrate 151 on a predetermined pattern, drying, and firing at a predetermined temperature. 152, the electrode 153 can be formed. The sealing material 154 is formed into a paste between glass and ceramic, coated on the heat generation resistor 152, covered with an insulating protective plate 155, and then heat-treated to be integrated.

Further, a notch may be formed in the forming portion of the electrode 153 of the insulating substrate 151 in order to improve the connection strength between the electrode 153 and the lead 150 (see FIG. 1A). One or a plurality of through holes may be provided in place of the notch, or the notch and the through hole may be used in combination. That is, the notch and the through hole are provided at a high temperature by increasing the connection area and taking measures such as an anchor effect to obtain mechanical engagement in order to improve the connection strength between the electrode 153 and the lead 150. Even when the hot end 10 is moved in two dimensions or three dimensions, it is possible to prevent connection failure from occurring.

In the state where the heating plate 15 is attached to the head body 1, the back surface (the surface of the insulating substrate 151 on which the heat generating resistor 152 is not formed) side of the heating plate 15 is the flat surface portion of the melting portion 13 of the head body 1. , For example, a silver-based thick film paste (Ag containing, for example, glass or Cu) is applied and fired as a bonding material so as to cover the opening 131, and the paste is bonded. At this time, the joining material enters the opening 131 and an anchor effect is obtained, so that the heating plate 15 can be firmly joined and attached to the melting portion 13 of the head body 1. Further, by providing the opening 131, heat can be directly conducted by the filament (modeling material) on the back surface (insulating substrate 151) of the heating plate 15. In the present invention, the opening 131 may not be provided. Here, the pair of heating plates 15 are arranged to face each other on the flat surface portion provided by grinding so as to face the outer wall surface of the melting portion 13, but even if there is only one heating plate 15. It may be 3 or more. For example, four grinding planes may be provided on the outer periphery of the melting portion 13, and three or four heating plates 15 may be provided. Further, the size and installation position of the heating plates 15 may be partially or completely changed. A plurality of heating plates may be arranged side by side in the length direction of the head body 1 or the installation position in the length direction may be changed so that an appropriate temperature gradient is formed by the flat surface portion of the melting portion 13. ..

In the present embodiment, the width of the heating plate (5 mm) is slightly wider than the width of the flat surface portion (4 mm) of the melting portion 13 of the head main body 1, and the connection portion between the heating plate 15 and the lead 150 is connected to the head main body. The heating plate 15 is joined to the head body 1 by protruding outward from one side edge of the flat surface portion of the melting portion 13 of 1.

FIG. 4 shows a case where the heating is adjusted and the temperature is controlled by controlling the electric power supplied from the voltage applying means to the heat generating resistor 152 according to the measured temperature of the heating plate 15 at the hot end 10. It is a block diagram which shows an example of a drive circuit. That is, this drive circuit is an example of driving the heating plate 15 with the power supply 21 which is a voltage applying means and the power supplied from the adjusting unit. As the power supply 21, for example, a commercial AC voltage of 60 Hz or 50 Hz, or a commercial AC voltage of 60 Hz or 50 Hz, or An AC voltage obtained by transforming a commercial AC voltage with a transformer is used. In this case, an AC / DC converter that converts the AC voltage input from the power supply 21 into a DC voltage, a smoothing capacitor that smoothes the converted DC voltage, and a smoothing capacitor. The applied voltage and applied time are adjusted by an adjusting unit including a converter C including a DC / AC inverter that pulses and modulates a smoothed DC voltage (for example, frequency modulation or pulse width modulation) to convert alternating current. The generated power (alternating current voltage) is supplied to the heat generation resistor 152. Further, the power supply 21 may be a DC voltage, and in this case, the power (alternating voltage) converted into an alternating current (alternating current) voltage in the adjusting unit including the conversion device C which is a DC / AC inverter capable of pulsing and modulating the direct current voltage is used. It is supplied to the heat generation resistor 152.

FIG. 5 shows a specific configuration of the conversion device C when the power supply 21 is an AC voltage. The AC / DC converter C1 _{full-wave rectifies the input AC voltage V IN} to make the polarity unidirectional and provides the smoothing capacitor C2. The smoothing capacitor C2 smoothes the rectified input voltage and supplies a DC voltage to the DC / AC inverter. The DC / AC inverter C3 pulses the DC voltage, modulates the pulse width or the pulse frequency, and outputs the _{modulated alternating voltage V OUT.} That is, the adjusting unit can control the effective applied power supplied to the heat generation resistor 152 by PFM (pulse frequency modulation), PWM (pulse width modulation), or the like.

The control means in the drive circuit generates heat from the adjusting unit so that the heating plate 15 (melting unit 13) reaches a desired temperature according to the measured temperature of the heating plate 15 (melting unit 13 temperature). A control signal is output so as to control the execution applied power to the resistor 152. The temperature of the heating plate 15 can be measured, for example, by a thermistor or a thermocouple attached to the heating plate 15. The temperature may be measured by detecting the current value in the drive circuit of the heat generation resistor 152 and measuring the resistance value of the heat generation resistor 152 calculated from the current value and the voltage value applied to the heat generation resistor 152. In FIG. 4, a shunt resistor 22 is provided on the side opposite to the adjusting portion of the heat generating resistor 152, and the current value flowing through the shunt resistor 22 is detected with respect to the pulse voltage value for temperature measurement periodically input from the adjusting portion. An example of inputting to the control means is shown.

In the temperature control of the heating plate 15 by the control means, when the filament is used as a modeling material, when the filament is fed, heat is applied so as to reach the target working temperature at that time. When the feeding is stopped, the temperature rises above the target value, so reduce the amount of heating so that the temperature does not rise above the target value. It is controlled so that the target temperature can be maintained even if the filament is fed again. In this way, the heating amount can be adjusted according to the temperature change due to the timing of feeding the filament.

The temperature adjusting portion 16 is a ring-shaped member, and the head main body 1 is fitted into the hollow portion thereof, and is provided so as to cover the outer peripheral portion near the boundary portion between the melting portion 13 and the heat insulating portion 12. The temperature adjusting unit 16 increases the heat capacity near the boundary between the melting unit 13 and the heat insulating unit 12 to suppress the temperature rise. By suppressing the temperature rise near this boundary portion, the boundary between the portion having high fluidity of the modeling material (for example, the molten state) and the portion having low fluidity (for example, the solid state) in the passage 2 is the heat insulating portion. The movement to the 12 side can be suppressed, and the clogging of the modeling material in the passage 2 of the hot end 10 can be suppressed. The degree of suppression of this temperature rise can be adjusted by the size and shape of the temperature adjusting unit 16. The temperature adjusting unit 16 may be provided with a temperature monitoring means for detecting the temperature near the boundary between the melting unit 13 and the heat insulating unit 12. The electric power applied to the heat generation resistor 152 from the adjusting unit in the above-mentioned drive circuit can be controlled so as not to exceed a predetermined temperature based on the temperature detected by the temperature monitoring means input to the control means.

Since the hot-end three-dimensional printer of the above-described embodiment can quickly raise the temperature to a high temperature of 400 to 500 ° C. or higher and has excellent durability, a mixture such as PEEK or carbon fiber can be used as a modeling material. In addition to the contained resins such as PEEK, it can also be used for low melting point metals and low melting point glasses. It can be suitably used for three-dimensional modeling using a modeling material that is heated and melted at 400 ° C. or higher.

1 Head body 2 Passage 10 Hot end 11 Supply part 111 Supply port 12 Insulation part 121 Opening part 13 Melting part 131 Opening part 14 Discharge part 141 Discharge port 15 Heating plate 150 Lead 151 Insulation substrate 152 Heat generation resistor (heat resistance layer)
153 Electrode 153c Intermediate terminal 154 Sealing material (protective layer)
155 Insulation protection plate 16 Temperature control unit 21 Power supply 22 Shunt resistance C converter C1 AC / DC converter C2 Smoothing capacitor C3 DC / AC inverter

That is, the present invention has a rectangular insulating substrate whose width dimension is longer than twice the vertical width dimension, and a thick film heat-generating resistor layer formed in a zigzag shape by being folded back in a plurality of directions in the lateral direction on the insulating substrate. It relates to a heating plate characterized by the above. The multiple folded sites may have corners. The heating plate may be for a polar alternating voltage (alternating current voltage).

Claims (2)

A heating plate characterized by having a rectangular insulating substrate and a heat generating resistor layer formed on the insulating substrate in a zigzag shape by being folded back in a plurality of directions in the lateral direction. The heating plate according to claim 1, wherein the heating plate is for an AC voltage.

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