Three-dimensional molding device and method for controlling discharge timing of curing liquid in three-dimensional molding device

Abstract

An encoder 90 transmits a pulse each time a discharge head 60 moves by a distance a. A discharge control unit 110 controls the discharge of a curing liquid from the discharge head 60 at a resolution of a distance b that is P times the distance a with respect to the position of the discharge head 60. The three-dimensional molding device 10 controls the discharge timing of the curing liquid while repeating sets, one set being composed of n instances of a first count process in which it is deemed that the discharge head 60 has moved by the distance b each time Q counts of pulses are received and (m − n) instances of a second count process in which it is deemed that the discharge head 60 has moved by the distance b each time (Q + 1) counts of pulses are received, where m is the smallest natural number that allows P × m to be a natural number, natural number Q is the integer part of P, and n is a natural number for which the equation Q × n + (Q + 1) × (m − n) = P × m holds true.

Description

Three-dimensional modeling apparatus and method for controlling discharge timing of curable liquid in three-dimensional modeling apparatus

[0001] The present invention relates to a three-dimensional modeling apparatus and a method for controlling discharge timing of a curable liquid in a three-dimensional modeling apparatus.

[0002] Conventionally, there has been known an apparatus that produces a three-dimensional modeled article by discharging a curable liquid onto a powder material to form a thin cured layer having a desired cross-sectional shape and stacking the cured layers. For example, Patent Document 1 discloses a three-dimensional modeling apparatus including: a modeling tank in which a three-dimensional modeled article is formed; a supply tank that holds powder to be supplied to the modeling tank; a flattening roller that transfers the powder from the supply tank to the modeling tank to form a powder layer; and a liquid discharge head that discharges a curable liquid for curing the powder onto the powder layer on the modeling tank.

[0003] For example, Patent Document 2 discloses a discharge control apparatus that includes a linear encoder and controls ink discharge timing by a discharge head based on encoder pulses generated by the linear encoder. In the discharge control apparatus described in Patent Document 2, in consideration of the fact that the timing at which the linear encoder outputs pulses is not always ideal, the timing of discharge triggers is corrected based on pre-measured outputs of the linear encoder so that intervals between the discharge triggers are uniform.

[0004] Japanese Patent Application Laid-Open No. 2017-164989 Japanese Patent Application Laid-Open No. 2015-074149

[0005] In 3D printing systems, the control resolution of the curing fluid discharge timing related to the position of the discharge head (hereinafter simply referred to as "discharge resolution of the discharge head") is relatively coarse. Therefore, the pulse resolution of the encoder is generally finer than the discharge resolution of the discharge head. In this case, unless the pulse resolution of the encoder is an integer multiple of the discharge resolution of the discharge head, errors in the curing fluid discharge timing due to the mismatch between the pulse resolution of the encoder and the discharge resolution of the discharge head will accumulate. To resolve the mismatch between the pulse resolution of the encoder and the discharge resolution of the discharge head, it would be possible to specially manufacture an encoder whose pulse resolution is an integer multiple of the discharge resolution of the discharge head, but such encoders are expensive and not readily available. If the position of the discharge head is determined in real time based on the pulse resolution of the encoder and the calculation to determine the curing fluid discharge timing based on that result is performed, the computational load will be excessive.

[0006] The present invention has been made in view of the above, and its object is to provide a three-dimensional molding apparatus in which the pulse resolution of the encoder is finer than the ejection resolution of the ejection head, and in which the ejection timing of the curing liquid from the ejection head can be easily controlled. Furthermore, the present invention aims to provide a control method that can easily control the ejection timing of the curing liquid from the ejection head in a three-dimensional molding apparatus in which the pulse resolution of the encoder is finer than the ejection resolution of the ejection head.

[0007] The three-dimensional molding apparatus disclosed herein comprises a molding tank containing powder material, an ejection head for ejecting a curing liquid for curing the powder material, a moving device for moving the ejection head or the molding tank and changing the position of the ejection head relative to the molding tank, an encoder that emits a pulse each time the ejection head or the molding tank moves by a distance a by the moving device, and a control device. The control device comprises a pulse receiving unit for receiving pulses from the encoder, and an ejection control unit for controlling the ejection head to eject the curing liquid with a resolution of distance b which is P times the distance a (where P is a number greater than 1) with respect to the movement of the position of the ejection head relative to the molding tank. Let m be the smallest natural number such that P × m is a natural number, and let Q be the integer part of P, so that Q × n + (Q + 1) × (m - n) = P × m is a natural number. The discharge control unit controls the discharge timing of the curing liquid by repeating a set of the following: a first counting process n times, in which each time a Q count pulse is received, the discharge head or the molding tank is deemed to have moved a distance b; and a second counting process (m - n times), in which each time a (Q + 1) count pulse is received, the discharge control unit considers the discharge head or the molding tank to have moved a distance b.

[0008] Furthermore, the method for controlling the discharge timing of a curing liquid in a three-dimensional molding apparatus disclosed herein is a method for controlling the discharge timing of the curing liquid from the discharge head in a three-dimensional molding apparatus comprising: a molding tank containing powder material; a discharge head for discharging a curing liquid for curing the powder material; a moving device for moving the discharge head or the molding tank and changing the position of the discharge head relative to the molding tank; and an encoder that emits a pulse each time the discharge head or the molding tank is moved by the moving device by a distance a. The discharge timing of the curing liquid is controlled with respect to the movement of the position of the discharge head relative to the molding tank with a resolution of distance b which is P times the distance a (where P is a number greater than 1). The ejection timing control method disclosed herein includes the steps of: finding the smallest natural number m such that P × m is a natural number; finding an integer n such that Q × n + (Q + 1) × (m - n) = P × m, where Q is the integer part of P; and repeating a set of a first counting process n times, in which each time a Q count pulse is received from the encoder, the ejection head or the molding tank is deemed to have moved by a distance b; and a second counting process (m - n times), in which each time a (Q + 1) count pulse is received from the encoder, the ejection head or the molding tank is deemed to have moved by a distance b.

[0009] According to the above-described three-dimensional molding apparatus or control method, the equation Q × n + (Q + 1) × (m - n) = P × m holds true, and since the n first counting processes and (m - n) second counting processes are performed within one set, the mismatch between the encoder's pulse resolution a and the ejection head's ejection resolution b is resolved each time a set is completed. Therefore, the error in the timing of the curing liquid ejection from the ejection head does not accumulate. As a result, even without calculating the position of the ejection head based on the encoder's pulse resolution a, the accuracy of the ejection timing of the ejection head is ensured to a certain extent by repeating the set. By repeating such sets, the ejection control of the curing liquid from the ejection head can be made simpler.

[0010] This is a perspective view of a three-dimensional molding apparatus according to one embodiment. This is a plan view of the three-dimensional molding apparatus. This is a longitudinal cross-sectional view of the three-dimensional molding apparatus. This is a block diagram of the three-dimensional molding apparatus. This is a schematic diagram of a memory map. This is a flowchart related to memory map creation. This is a schematic diagram showing an example of a set configuration. This is a flowchart related to the emission of an ejection signal.

[0011] The following description of a three-dimensional molding apparatus according to an embodiment of the present invention will be given with reference to the drawings. It should be noted that the embodiments described herein are not intended to particularly limit the present invention. Each figure is schematic and does not necessarily reflect the actual proportions, etc. Furthermore, the same reference numerals are used for members and parts that perform the same function, and redundant explanations are omitted or simplified as appropriate.

[0012] [Configuration of the Three-Dimensional Manufacturing Apparatus] Figure 1 is a perspective view of a three-dimensional manufacturing apparatus 10 according to one embodiment. Figure 2 is a plan view of the three-dimensional manufacturing apparatus 10. Figure 3 is a longitudinal cross-sectional view of the three-dimensional manufacturing apparatus 10. In the drawings, the symbol F indicates the front, and the symbol Rr indicates the rear. Here, the left, right, top, and bottom of the three-dimensional manufacturing apparatus 10 are the left, right, top, and bottom of the three-dimensional manufacturing apparatus 10 when viewed from the direction of symbol F. In the drawings, the symbols L, R, U, and D mean left, right, top, and bottom, respectively.

[0013] As shown in Figures 1 to 3, the three-dimensional molding apparatus 10 comprises a main body 11, a supply tank 20, a molding tank 30, a recovery tank 40, a roller unit 50, a discharge head 60, a carriage 70 that holds the roller unit 50 and the discharge head 60, a carriage 70 moving device 80, an encoder 90 for calculating the position of the carriage 70, and a control device 100. The three-dimensional molding apparatus 10 forms a powder layer 210 by leveling the powder material 200 supplied from the supply tank 20 on the molding tank 30, and forms a hardened layer 220 by discharging a hardening liquid to a desired location on the powder layer 210 and hardening it. Then, the object to be molded 230 is formed by stacking the hardened layer 220 on top.

[0014] As shown in Figure 1, the main body 11 is the exterior of the three-dimensional molding apparatus 10, which has a long shape in the front-to-back direction. The main body 11 houses the supply tank 20, the molding tank 30, the recovery tank 40, and the control device 100. Also, as shown in Figure 1, the main body 11 supports the carriage 70 and the moving device 80.

[0015] The supply tank 20 is located in the front part of the main body 11. The supply tank 20 stores the powder material 200 before it is supplied to the molding tank 30. The supply tank 20 is an example of a powder supply device that supplies the powder material 200, which is the material for the object to be molded 230. As shown in Figure 3, the supply tank 20 comprises a cylindrical part 21, a supply table 22, and a supply table lifting device 23.

[0016] The cylindrical portion 21 has a cylindrical shape that extends in the vertical direction. The top surface of the cylindrical portion 21 is open. As shown in Figure 2, the shape of the cylindrical portion 21 is rectangular in plan view. However, the planar shape of the cylindrical portion 21 is not limited to a rectangle. As shown in Figure 3, a supply table 22, which has the same shape as the cylindrical portion 21 in plan view, is housed inside the cylindrical portion 21. The supply table 22 is inserted into the cylindrical portion 21 approximately horizontally. As shown in Figure 3, the supply table 22 has a flat plate shape. Powder material 200 is placed on the supply table 22. The supply table 22 is configured to move vertically along the inner circumferential surface of the cylindrical portion 21.

[0017] The supply table lifting device 23 is located below the supply table 22. The supply table lifting device 23 supports and raises the supply table 22. The supply table lifting device 23 comprises a support part 23a, a lifting motor 23b, and a ball screw (not shown). The support part 23a is connected to the lower surface of the supply table 22. The support part 23a is connected to the lifting motor 23b via the ball screw. By driving the lifting motor 23b, the support part 23a is moved in the vertical direction. The supply table 22 is supported by the support part 23a and moves vertically together with the support part 23a. The lifting motor 23b is electrically connected to the control device 100 and controlled by the control device 100. The lifting motor 23b is, for example, a servo motor and is configured to control the height of the supply table 22.

[0018] The composition and form of the powder material 200 are not particularly limited, and powders composed of various materials such as resin materials, metal materials, and inorganic materials can be used. Examples of powder material 200 include ceramic materials such as alumina, silica, titania, and zirconia, as well as iron, aluminum, titanium and their alloys (typically stainless steel, titanium alloys, and aluminum alloys), hemihydrate gypsum (α-type calcined gypsum, β-type calcined gypsum), apatite, sodium chloride, and plastics. These may consist of any one of these materials, or two or more may be combined.

[0019] The molding tank 30 contains powder material 200, and the object to be molded 230 is formed within it. As shown in Figure 2, the molding tank 30 is located behind the supply tank 20. The supply tank 20 and the molding tank 30 are arranged side by side in the front-to-back direction. The molding tank 30 is positioned in the same position as the supply tank 20 in the left-to-right direction. The molding tank 30 comprises a cylindrical section 31, a molding table 32, and a molding table lifting device 33.

[0020] The cylindrical portion 31 has a cylindrical shape that extends in the vertical direction. As shown in Figure 2, the top surface of the cylindrical portion 31 is open. In plan view, the cylindrical portion 31 is rectangular. However, the planar shape of the cylindrical portion 31 is not limited to a rectangle. As shown in Figure 3, a build table 32, which has the same shape as the cylindrical portion 31 in plan view, is housed inside the cylindrical portion 31. The build table 32 is inserted into the cylindrical portion 31 in a substantially horizontal manner. As shown in Figure 3, the build table 32 has a flat plate shape. The build table 32 is a component on which the object to be molded 230 is formed from the powder material 200. The build table 32 is configured to move vertically along the inner circumferential surface of the cylindrical portion 31.

[0021] The build table lifting device 33 is located below the build table 32. The build table lifting device 33 supports and raises the build table 32. The build table lifting device 33 comprises a support part 33a, a lifting motor 33b, and a ball screw (not shown). The support part 33a is connected to the underside of the build table 32. The support part 33a is connected to the lifting motor 33b via the ball screw. By driving the lifting motor 33b, the support part 33a is moved in the vertical direction. The build table 32 is supported by the support part 33a and moves vertically together with the support part 33a. The lifting motor 33b is electrically connected to the control device 100 and is controlled by the control device 100. The lifting motor 33b is, for example, a servo motor and is configured to control the height of the build table 32.

[0022] As shown in Figure 2, the recovery tank 40 is located further rearward from the molding tank 30. The supply tank 20, the molding tank 30, and the recovery tank 40 are arranged in this order in the front-to-back direction. The recovery tank 40 is positioned in the left-to-right direction, aligned with the supply tank 20 and the molding tank 30. The recovery tank 40 also comprises a cylindrical section 41, a recovery table 42, and a recovery table lifting device 43.

[0023] The cylindrical portion 41 has a cylindrical shape that extends in the vertical direction. As shown in Figure 2, the top surface of the cylindrical portion 41 is open. In plan view, the cylindrical portion 41 is rectangular. However, the planar shape of the cylindrical portion 41 is not limited to a rectangle. As shown in Figure 3, a recovery table 42, which has the same shape as the cylindrical portion 41 in plan view, is housed inside the cylindrical portion 41. The recovery table 42 is inserted into the cylindrical portion 41 approximately horizontally. As shown in Figure 3, the recovery table 42 has a flat plate shape. The remaining powder material 200, which has been transported by the stacked rollers 51 (described later) of the roller unit 50 and not leveled on the molding table 32, is dropped onto the recovery table 42. In this embodiment, the recovery table 42 is also configured to move vertically along the inner circumferential surface of the cylindrical portion 41.

[0024] The retrieval table lifting device 43 is located below the retrieval table 42. The retrieval table lifting device 43 comprises a support portion 43a, a lifting motor 43b, and a ball screw (not shown). The support portion 43a is connected to the lower surface of the retrieval table 42. The support portion 43a is connected to the lifting motor 43b via the ball screw. By driving the lifting motor 43b, the support portion 43a is moved in the vertical direction. The retrieval table 42 is supported by the support portion 43a and moves vertically together with the support portion 43a. The lifting motor 43b is electrically connected to the control device 100 and is controlled by the control device 100. The lifting motor 43b is, for example, a servo motor and is configured to control the height of the retrieval table 42.

[0025] The moving device 80 moves the discharge head 60 or the molding tank 30 to change the position of the discharge head 60 relative to the molding tank 30. In this embodiment, the moving device 80 moves the carriage 70 in the direction of alignment of the supply tank 20, the molding tank 30, and the recovery tank 40, in this case, in the front-to-back direction. By moving the carriage 70 in the front-to-back direction, the discharge head 60 moves in the front-to-back direction. However, the moving device 80 may also move the supply tank 20, the molding tank 30, and the recovery tank 40 in the direction of alignment of the supply tank 20, the molding tank 30, and the recovery tank 40. As shown in Figure 2, the moving device 80 includes a pair of guide rails 81L and 81R and a feed motor 82. The pair of guide rails 81L and 81R each extend in the front-to-back direction and are aligned in the left-to-right direction. The carriage 70 is slidably engaged with the pair of guide rails 81L and 81R. The carriage 70 moves in the forward and backward direction along a pair of guide rails 81L and 81R.

[0026] The moving device 80 includes pulleys 83L1 and 83L2 positioned at the front and rear ends of the left guide rail 81L, respectively, pulleys 83R1 and 83R2 positioned at the front and rear ends of the right guide rail 81R, respectively, a front connecting rod 84F connecting pulley 83L1 and pulley 83R1, a rear connecting rod 84Rr connecting pulley 83L2 and pulley 83R2, a left belt 85L wrapped around pulleys 83L1 and 83L2, and a right belt 85R wrapped around pulleys 83R1 and 83R2. The feed motor 82 rotates the rear connecting rod 84Rr. Belts 85L and 85R are fixed to the carriage 70. When the feed motor 82 is driven, the connecting rod 84Rr rotates, and the left and right belts 85L and 85R travel. As a result, the carriage 70 moves in the forward and backward direction along the guide rails 81L and 81R. The feed motor 82 is equipped with a built-in encoder 82a (see Figure 4) for measuring the amount of movement of the carriage 70. The built-in encoder 82a emits a pulse each time the feed motor 82 rotates by a predetermined angle.

[0027] The roller unit 50 is mounted on the carriage 70. As shown in Figure 2, the roller unit 50 includes a stacking roller 51, a pair of roller support members 52 that support the stacking roller 51, and a drive device 53 (see Figure 4) that rotates the stacking roller 51. As shown in Figure 3, the stacking roller 51 is positioned above the main body 11. The stacking roller 51 is a roller that pushes and spreads the powder material 200 from the supply table 22 into the molding tank 30. The stacking roller 51 is positioned behind the discharge head 60. The stacking roller 51 has a long cylindrical shape that extends in the left-right direction. The left-right length of the stacking roller 51 is longer than the left-right length of the molding tank 30. The stacking roller 51 is provided at a predetermined height above the supply tank 20 and the molding tank 30. The lower end of the stacking roller 51 is positioned slightly above the supply tank 20 and the build tank 30 so that a predetermined clearance (gap) is formed between the supply table 22 and the build table 32.

[0028] The drive unit 53 rotates the lamination roller 51 around its axis. When the drive unit 53 spreads the powder material 200 into the molding tank 30, it rotates the lamination roller 51 in the opposite direction (see arrow in Figure 3) to the direction of movement of the roller unit 50 relative to the molding tank 30 (in this case, backward).

[0029] The moving device 80 moves the stacking roller 51 in the forward and backward directions together with the carriage 70. The moving device 80 and the roller unit 50 constitute a layer forming apparatus that levels the powder material 200 placed on the supply table 22 on the molding tank 30.

[0030] The discharge head 60 is mounted on the carriage 70. The discharge head 60 discharges a curing liquid for curing the powder material 200 toward the powder material 200 on the build table 32. The discharge head 60 discharges the curing liquid downwards. The discharge head 60 is arranged side by side in the left-right direction and is equipped with a plurality of nozzles (not shown) that discharge the curing liquid. The discharge head 60 is moved in the front-rear direction together with the carriage 70 by a moving device 80. The combination of the front-rear movement by the moving device 80 and the nozzles that discharge the liquid causes the discharged liquid to land at a desired position on the build table 32. The discharge mechanism for the curing liquid in the discharge head 60 is not particularly limited, and for example, an inkjet method can be suitably used. The discharge head 60 is electrically connected to a control device 100 and controlled by the control device 100.

[0031] The curing liquid is not particularly limited as long as it is a material capable of bonding the powder materials 200 together. Depending on the type of powder material 200, the curing liquid used is a liquid (including viscous substances) capable of binding the particles constituting the powder material 200 together. Examples of curing liquids include water, wax, binders, etc. Furthermore, if the powder material 200 contains a water-soluble resin as a secondary material, a liquid capable of dissolving the water-soluble resin, such as water, can also be used as the curing liquid. Such water-soluble resins are not particularly limited, but examples include starch, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), water-soluble acrylic resin, water-soluble urethane resin, water-soluble polyamide, etc.

[0032] The encoder 90 transmits pulses to the control device 100 to determine the timing for discharging the curing liquid from the discharge head 60. The encoder 90 transmits pulses each time the discharge head 60 moves a predetermined distance a by the moving device 80. Hereinafter, this distance a will also be referred to as the resolution a of the encoder 90. The resolution a of the encoder 90 is the minimum length that the encoder 90 can measure. The resolution a of the encoder 90 is not particularly limited, however, it is smaller than the discharge resolution of the discharge head 60 with respect to its position in the front-rear direction (the control resolution when discharging the curing liquid from the discharge head 60). The discharge resolution b of the discharge head 60 is the unit length of the interval at which the discharge head 60 discharges the curing liquid. The three-dimensional molding apparatus 10 discharges the curing liquid from the discharge head 60 each time the discharge head 60 moves a distance b.

[0033] As shown in Figure 1, the encoder 90 comprises a magnetic scale 91 provided on the main body 11 and a reading unit 92 provided on the carriage 70. The encoder 90 is a magnetic encoder that measures position using magnetism. The magnetic scale 91 is a strip-shaped member on which magnetic scales are engraved at a predetermined pitch (generally longer than the resolution a of the encoder 90). As shown in Figure 1, the magnetic scale 91 is fixed to the main body 11 such that its longitudinal direction coincides with the front-to-back direction of the three-dimensional molding apparatus 10 (the direction of movement of the carriage 70). The numerous magnetic scales each extend in the left-to-right direction and are arranged in the front-to-back direction. The reading unit 92 is configured to calculate the position obtained by further dividing one pitch of the magnetic scale from the magnetic state read from the magnetic scale 91. The reading unit 92, for example, comprises two magnetic detection heads arranged in the front-to-back direction and calculates the position obtained by further dividing one pitch of the magnetic scale from magnetic force waveforms with different phases detected by the two heads. The reading unit 92 emits a pulse each time it moves a distance a. Here, the reading unit 92 emits two pulses that are out of phase (for example, out of phase by one-quarter of the resolution a). The direction of the phase difference between the two pulses changes according to the direction of movement of the reading unit 92. Therefore, the direction of movement of the carriage 70 and the ejection head 60 can be detected from the direction of the phase difference between the two pulses. Various known magnetic encoders can be used as the encoder 90 without any particular limitations.

[0034] Figure 4 is a block diagram of the three-dimensional molding apparatus 10. As shown in Figure 4, the control device 100 is electrically connected to the lifting motor 23b of the supply tank 20, the lifting motor 33b of the molding tank 30, the lifting motor 43b of the recovery tank 40, the drive unit 53 of the roller unit 50, the discharge head 60, and the feed motor 82 of the moving device 80, and controls their operation. The control device 100 is also connected to the built-in encoder 82a and encoder 90 of the feed motor 82, and receives the pulses they emit.

[0035] The configuration of the control device 100 is not particularly limited. The control device 100 is, for example, a microcomputer. The hardware configuration of the microcomputer is not particularly limited, but for example, it includes an interface (I / F) for receiving molding data etc. from an external device such as a host computer, a central processing unit (CPU) that executes instructions for the control program, a ROM (read-only memory) that stores the program executed by the CPU, a RAM (random access memory) used as a working area for expanding the program, and a storage device such as memory that stores the above program and various data. Note that the control device 100 does not necessarily have to be located inside the main unit 11, and may include, for example, a computer installed outside the main unit 11 and connected to the control unit inside the main unit 11 so as to be able to communicate via wired or wireless connection. In this embodiment, some functions of the control device 100 are handled by an FPGA (field programmable gate array).

[0036] As shown in Figure 4, the control device 100 includes a supply tank control unit 101 that controls the operation of the lifting motor 23b of the supply tank 20, a build tank control unit 102 that controls the operation of the lifting motor 33b of the build tank 30, a recovery tank control unit 103 that controls the operation of the lifting motor 43b of the recovery tank 40, a roller unit control unit 104 that controls the operation of the drive unit 53 of the roller unit 50, a feed control unit 105 that controls the operation of the feed motor 82 of the moving device 80, a discharge control unit 110 that controls the operation of the discharge head 60, and a pulse receiving unit 120 that receives pulses from the encoder 90. The control device 100 may include other processing units, but these are not shown or described here. Also, with the exception of the discharge control unit 110 and the pulse receiving unit 120, detailed descriptions of each processing unit of the control device 100 are omitted.

[0037] The discharge control unit 110 controls the discharge head 60 so that it discharges the hardening liquid with a resolution of distance b which is longer than distance a (resolution of the encoder 90) with respect to the movement of the discharge head 60 relative to the build tank 30. The discharge resolution b of the discharge head 60 is coarser than the resolution a of the encoder 90. Hereinafter, we assume that distance b is P times distance a. The discharge control unit 110 controls the discharge head 60 so that it discharges the hardening liquid with a resolution of distance b which is P times distance a (resolution of the encoder 90) with respect to the movement of the discharge head 60 relative to the build tank 30. P is a number greater than 1. P can be a natural number, but is generally not a natural number. In many cases, P includes an integer part (hereafter, the symbol Q will be used as appropriate) and a decimal part less than 1 (hereafter, the symbol Qq will be used as appropriate).

[0038] The resolution b of the discharge head 60 only needs to be about the same as the particle size of the powder material 200 (for example, 0.1 to 1 times the particle size of the powder material 200), and it does not need to be excessively finer than the particle size of the powder material 200. As will be illustrated later, in this embodiment, the resolution b of the discharge head 60 is preferably about the same as the particle size of the powder material 200. The resolution a of the encoder 90 is fixed if the encoder 90 is a commercially available product, and is generally much finer than the resolution b of the discharge head 60. P is, for example, 100 or more. However, the fractional part Qq of P, when accumulated, becomes a factor in the error of the discharge position of the curing liquid.

[0039] The discharge control unit 110 controls the discharge timing of the curing liquid based on encoder pulses that are not set to an integer multiple of the resolution b of the discharge head 60, in order to reduce the cumulative error caused by the fractional part Qq of P. As shown in Figure 4, the discharge control unit 110 includes a counter 111, a signal transmission unit 112, a memory map registration unit 113, and a reset unit 114.

[0040] The counter 111 counts the pulses of the encoder 90 received by the pulse receiving unit 120. When the discharge head 60 is moving in a predetermined direction (for example, forward) and the phase difference direction of a pair of pulses from the encoder 90 is in the predetermined direction, the cumulative pulse count of the counter 111 increases by 1 each time the pulse receiving unit 120 receives an encoder pulse. When the discharge head 60 is moving in the opposite direction to the predetermined direction (for example, backward) and the phase difference direction of a pair of pulses from the encoder 90 is in the opposite direction, the cumulative pulse count of the counter 111 decreases by 1 each time the pulse receiving unit 120 receives an encoder pulse. However, the direction of movement of the discharge head 60 corresponding to the addition and subtraction of the pulse count of the counter 111 may be the opposite of the above.

[0041] The signal transmitting unit 112 transmits a signal (hereinafter also referred to as the discharge signal) to the discharge head 60 to discharge the hardening liquid. Within the control device 100, based on the molding data, nozzles to discharge the hardening liquid are specified for each position in the front-rear direction of the carriage 70. When the discharge signal is transmitted, the hardening liquid is discharged from the nozzles designated to discharge the hardening liquid. The discharge signal is a signal transmitted in response to the pulse count of the counter 111 and is a signal that instructs the timing for discharging the hardening liquid.

[0042] The discharge signal transmitted by the signal transmitting unit 112 has a length (duty cycle) corresponding to the characteristics of the discharge head 60. The duty cycle is set, for example, between 25% and 75% of the discharge resolution b of the discharge head 60. The discharge signal is transmitted based on the duty cycle and the pulse count of the counter 111. In this embodiment, the duty cycle is set to approximately 50% of the discharge resolution b of the discharge head 60. The pulse count corresponding to the discharge resolution b of the discharge head 60 may be odd, in which case there is no boundary between a duty cycle of less than 50% and 50% or more, so the duty cycle is set to the value closest to 50%. Hereinafter, this value closest to a duty cycle of 50% will also be simply referred to as a duty cycle of 50%.

[0043] A memory map M1 in which the count number of the counter 111 is associated with whether a discharge signal is transmitted or not transmitted is registered in the memory map registration unit 113. FIG. 5 is a schematic diagram of the memory map M1. As shown in FIG. 5, in the memory map M1, addresses 0 to D corresponding to counts 0 to D of the counter 111 (D is a count corresponding to 50% duty, which is approximately half of Q) are set, and discharge signal OFF is set at addresses 0 to D. At addresses (D+1) to Q corresponding to counts (D+1) to Q of the counter 111, the discharge signal is ON. As described above, the memory map M1 is provided with addresses 0, 1, ... corresponding to the accumulated pulse counts 0, 1, ... of the counter 111, and transmission or non-transmission of a discharge signal is set for each address. The signal transmission unit 112 refers to the memory map M1 according to the accumulated pulse count of the counter 111, and transmits or does not transmit a discharge signal. By means of this memory map M1, a discharge signal is transmitted in approximately half of the time during which the discharge head 60 moves a distance b. The content of the subsequent addresses will be described later.

[0044] In the present embodiment, the minimum natural number m that makes P×m a natural number is obtained in advance. For example, if P is "100.25", m is "4". P×m is "401". Note that "P×m becomes a natural number" may mean that P×m is substantially a natural number in a practical number of digits corresponding to the positional accuracy required for the moving device 80. Further, in the present embodiment, an integer n that satisfies Q×n + (Q+1)×(m-n) = P×m is obtained in advance. For example, if P is "100.25", Q which is the integer part of P is "100", and n is "3". Q and (Q+1) are two adjacent natural numbers that sandwich P. Note that if P happens to be a natural number, m is "1" and n is "1".

[0045] The discharge control unit 110 controls the discharge timing of the curing liquid by repeating the above set S1 (see Figure 7), which consists of a first counting process C1 (see Figure 7) n times, where each time a Q count pulse is received, the discharge head 60 is considered to have moved a distance b, and a second counting process C2 (see Figure 7) (m-n times), where each time a (Q+1) count pulse is received, the discharge head 60 is considered to have moved a distance b. The memory map registration unit 113 stores the order of the n times the first counting process C1 and the (m-n) times the second counting process C2 in set S1. Here, the memory map registration unit 113 stores a memory map M1, which sets the order of the n times the first counting process C1 and the (m-n) times the second counting process C2 in set S1 based on the setting of whether the discharge signal is transmitted or not. The relationship between the memory map M1 and the order of the counting processes will be described later with examples.

[0046] In terms of the order of operations, for example, the first counting process C1 is performed first, followed by the second counting process C2, then the first counting process C1 again, and so on. In this embodiment, the above order is determined so as to minimize the number of consecutive occurrences of the first counting process C1 and the second counting process C2. Details of the order will be described later with examples.

[0047] The reset unit 114 resets the counter 111 each time one set S1 is completed. Here, "resetting the counter 111" is a term that encompasses both resetting the counter 111 (returning the count to "0") and presetting (returning the count to a predetermined preset value, in this case (P × m - 1)), meaning returning to the state before the start of counting the encoder pulse. With a configuration in which the counter 111 is reset each time one set S1 is completed, it is only necessary to prepare the memory map M1 for one set of set S1. Therefore, the memory capacity used by the discharge control unit 110 can be reduced. The memory map M1 is prepared from address 0 to (P × m - 1).

[0048] As shown in Fig. 4, in the present embodiment, the discharge control unit 110 and the pulse receiving unit 120 are configured on a single FPGA (field programmable gate array; the reference symbol in the drawings is also FPGA). This FPGA can convert a pulse with resolution a from the encoder 90 into a discharge signal with resolution b suitable for the discharge head 60. By configuring these processing units in the FPGA, other three-dimensional modeling apparatuses in which at least one of the resolution a and the resolution b is different can be handled only by changing the program of the FPGA.

[0049] [Outline of Modeling Process] Hereinafter, a process of modeling an object 230 to be modeled by the three-dimensional modeling apparatus 10 will be described. The three-dimensional modeling apparatus 10 models the object 230 to be modeled by, for example, the following process. According to one preferred process, after completing the formation of one cured layer 220, the three-dimensional modeling apparatus 10 raises the supply table 22 and lowers the modeling table 32. When the formation of one cured layer 220 is completed, the upper surface of the powder material 200 on the supply table 22 is located at the same height as the lower end of the laminating roller 51. At this time, the upper surface of the cured layer 220 formed uppermost in the modeling tank 30 is also located at the same height as the lower end of the laminating roller 51.

[0050] When the supply table 22 is raised from this state, a part of the powder material 200 on the upper side overflows from the supply tank 20. The powder material 200 overflowing from the supply tank 20 becomes the powder material 200 supplied from the supply tank 20. The modeling table 32 is lowered by a predetermined distance from the above-described state. This predetermined distance is equal to the thickness of the cured layer 220 to be formed next. When the powder material 200 is supplied, the modeling table 32 is lowered by a thickness corresponding to one layer of the cured layer 220.

[0051] Next, the 3D printing apparatus 10 controls the moving device 80 to move the layering roller 51 backward. This movement causes the layering roller 51 to move from the front of the supply tank 20, over the supply tank 20 and the printing tank 30, to over the recovery tank 40. At this time, the layering roller 51 also rotates in the opposite direction to the direction of movement. This movement and rotation of the layering roller 51 spreads new powder material 200 onto the printing table 32. As a result, a new powder layer 210 is formed on the printing table 32. The remaining powder material 200 that was not spread onto the printing table 32 is dropped into the recovery tank 40.

[0052] The three-dimensional molding apparatus 10 sequentially discharges the curing liquid to predetermined locations on the powder layer 210 while forming a new powder layer 210 on the cured layer 220 as described above. In this embodiment, each time the discharge head 60 is moved by a distance b, the three-dimensional molding apparatus 10 discharges the curing liquid from the nozzle of the discharge head 60 specified in the molding data. This forms a new cured layer 220 on the powder layer 210. By repeating this process, the molded object 230 is completed. Note that this process is merely a preferred example, and the process for forming the molded object 230 is not limited to this.

[0053] [Creating a Memory Map] The following describes in detail how to control the timing of the curing liquid discharge from the discharge head 60 based on the pulses of the encoder 90. First, the process of creating the memory map M1 will be described. Figure 6 is a flowchart related to the creation of the memory map M1. As shown in Figure 6, in step S01, the creation of the memory map M1 involves finding the smallest natural number m for which P × m is a natural number. In this example, the resolution a of the encoder 90 is 1 μm, and the discharge resolution b of the discharge head 60 is 300 dpi, i.e., 84.67 μm. In this example, the discharge resolution b = 84.67 μm of the discharge head 60 is close to the particle size of the powder material 200 (approximately 100 μm). In the above case, P is 84.67 (resolution b: 84.67 μm is 84.67 times the resolution a: 1 μm). The smallest natural number m for which P × m is a natural number is 100. P × m is 8467. The fact that P × m = 8467 means that every 8467 movements of distance a (8467 encoder pulses), the mismatch between the encoder resolution a of the encoder 90 and the ejection resolution b of the ejection head 60 (corresponding to the fractional part Qq of P) is resolved.

[0054] In step S02, we find an integer n such that Q × n + (Q + 1) × (m - n) = P × m, where Q is a natural number in the integer part of P. In the example above, the integer part Q of P is 84. The decimal part Qq of P is 0.67. In this case, n is 33, and (m - n) is 67.

[0055] A natural number of Q encoder pulses smaller than P and adjacent to P correspond to a distance slightly shorter than the ejection resolution b of the ejection head 60 (here, 84.67 μm) (here, 84 μm). A natural number of (Q+1) encoder pulses larger than P and adjacent to P correspond to a distance slightly longer than the ejection resolution b of the ejection head 60 (here, 84.67 μm) (here, 85 μm). The fact that n = 33 and (m - n) = 67 means that by moving the distance corresponding to Q pulses (here, 84 pulses) 33 times and moving the distance corresponding to (Q+1) pulses (here, 85 pulses) 67 times, it is possible to move a distance corresponding to (P × m) encoder pulses (here, 8467 times, the number of pulses at which the mismatch between the resolution a of the encoder 90 and the ejection resolution b of the ejection head 60 is resolved). When the distance corresponding to Q pulses is moved n times, and the distance corresponding to (Q+1) pulses is moved (m-n) times, the error in the timing of the curing liquid discharge due to the mismatch between the resolution a of the encoder 90 and the discharge resolution b of the discharge head 60 is eliminated. Therefore, if n movements corresponding to Q pulses and (m-n) movements corresponding to (Q+1) pulses are considered as one set (set S1), and set S1 is repeated, the mismatch between the resolution a of the encoder 90 and the discharge resolution b of the discharge head 60 is eliminated each time set S1 is completed, and the error does not accumulate.

[0056] As shown in Figure 6, step S03 determines the order of the n first counting processes C1 and the (m-n) second counting processes C2 in set S1. Step S04 creates a memory map M1 that sets the order of the n first counting processes C1 and the (m-n) second counting processes C2 in set S1. More specifically, ON / OFF signals are set for addresses 0 to 8466 of the memory map M1.

[0057] Figure 7 is a schematic diagram showing an example of the configuration of set S1. Figure 7 also illustrates the relationship between the configuration of set S1 and the ON / OFF state of the output signal. As shown in Figure 7, in this example, the pattern of performing the second counting process C2 twice followed by the first counting process C1 once is repeated. As mentioned above, in this embodiment, the order is determined so as to minimize the number of consecutive times the first counting process C1 and the number of consecutive times the second counting process C2 are performed. With this pattern, the number of consecutive times the first counting process C1 is performed is limited to one, and the number of consecutive times the second counting process C2 is limited to two. In the example shown in Figure 7, only in the last pattern within set S1 is the second counting process C2 performed once (the 67th second counting process C2), and the first counting process C1 is not performed. As a result, the number of times the first counting process C1 is performed is 33 (n times), and the number of times the second counting process C2 is performed is 67 ((m-n) times).

[0058] By determining the order of the first counting process C1 and the second counting process C2 so as to minimize the number of consecutive occurrences, the maximum cumulative error in the middle of set S1 can be reduced. Note that an exceptional pattern different from the basic pattern (in the example in Figure 7, the pattern consisting only of the second counting process C2, placed at the end of set S1) may be inserted anywhere in set S1.

[0059] Once the order of the above counting processes is determined, this is reflected in the memory map M1. As shown in Figure 5, addresses 0 to Q (addresses 0 to 84 in this example) in the memory map M1 correspond to the first second counting process C2. At addresses 0 to D (addresses 0 to 42 in this example) in the memory map M1, the ejection signal of the ejection head 60 is set to OFF. Address D corresponds to the 50% duty cycle point. At addresses (D+1) to Q (addresses 43 to 84 in this example) in the memory map M1, the ejection signal of the ejection head 60 is set to ON (see also Figure 7).

[0060] Addresses (Q+1) to (2Q+1) in memory map M1 (addresses 85 to 169 in this example) correspond to the second counting process C2. In addresses (Q+1) to (Q+1+D) in memory map M1 (addresses 85 to 127 in this example), the ejection signal of the ejection head 60 is set to OFF. By setting the ejection signal to OFF in addresses (Q+1) to (Q+1+D), the boundary between the first counting process (addresses 0 to 84) and the second counting process (addresses 85 to 169) is established. This also sets the first counting process (addresses 0 to 84) to the second counting process C2. In addresses (Q+D+2) to (2Q+1) in memory map M1 (addresses 128 to 169 in this example), the ejection signal of the ejection head 60 is set to ON (see also Figure 7).

[0061] Addresses (2Q+2) to (3Q+1) in memory map M1 (addresses 170 to 253 in this example) correspond to the first counting process C1. At addresses (2Q+2) to (2Q+1+D) in memory map M1 (addresses 170 to 211 in this example), the ejection signal of the ejection head 60 is set to OFF. By setting the ejection signal to OFF at addresses (2Q+2) to (2Q+1+D), the boundary between the second counting process (addresses 85 to 169) and the third counting process (addresses 170 to 253) is established, and the second counting process (addresses 85 to 169) is set to the second counting process C2. At addresses (2Q+D+2) to (3Q+1) in memory map M1 (addresses 212 to 253 in this example), the ejection signal of the ejection head 60 is set to ON (see also Figure 7). Similarly, the memory map M1 sets the order of the n first counting processes C1 and the (m-n) second counting processes C2 in set S1 based on whether the output signal is transmitted or not.

[0062] [Sending the Discharge Signal] Next, the process of sending a discharge signal based on the pulses of the encoder 90 will be described. Figure 8 is a flowchart related to the sending of the discharge signal. As shown in Figure 8, in step S10 of the process of sending a discharge signal, pulses from the encoder 90 are received. In step S20, it is determined whether the direction of movement of the discharge head 60 is in the direction of addition or subtraction of the pulse count. Whether the direction of movement of the discharge head 60 is in the direction of addition or subtraction of the pulse count is determined by the direction of the phase difference between the pair of pulses of the encoder 90.

[0063] If the direction of movement of the discharge head 60 is in the direction of pulse count addition (if the result of step S20 is YES), in step S31, it is determined whether the current cumulative pulse count of the counter 111 is (P × m - 1). If the current cumulative pulse count is (P × m - 1) (if the result of step S31 is YES), in step S41, the pulse count of the counter 111 is reset to 0. If the current cumulative pulse count is not (P × m - 1) (if the result of step S31 is NO), in step S42, the pulse count of the counter 111 is increased by 1. If the direction of movement of the discharge head 60 is in the direction of pulse count subtraction (if the result of step S20 is NO), in step S32, it is determined whether the current cumulative pulse count of the counter 111 is 0. If the current cumulative pulse count is 0 (if the result of step S32 is YES), in step S43, the pulse count of the counter 111 is preset to (P × m - 1). If the current cumulative pulse count is not zero (i.e., the result of step S32 is NO), in step S44, the pulse count of counter 111 is decremented by one.

[0064] In step S50, the contents of the address in memory map M1 corresponding to the cumulative pulse count of counter 111 are referenced. For example, when the first increment pulse is input to counter 111, the contents of address 1 in memory map M1 are referenced. In step S60, it is determined whether ON or OFF is set at the referenced address in memory map M1. If ON is set at the referenced address in memory map M1 (if the result of S60 is YES), a discharge signal is sent in step S71. If OFF is set at the referenced address in memory map M1 (if the result of S60 is NO), no discharge signal is sent in step S72.

[0065] In this embodiment, steps S10 to S71 or S72 are repeated until the formation of one hardened layer 220 is complete. The same process as described above is carried out when forming a new hardened layer 220.

[0066] [Effects of the Embodiment] The following describes the effects that can be achieved by the three-dimensional molding apparatus 10 according to this embodiment.

[0067] The three-dimensional molding apparatus 10 according to this embodiment includes a molding tank 30 in which powder material 200 is contained, a discharge head 60 for discharging a curing liquid for curing the powder material 200, a moving device 80 for moving the discharge head 60 to change the position of the discharge head 60 relative to the molding tank 30, an encoder 90 that emits a pulse each time the discharge head 60 moves a distance a by the moving device 80, and a control device 100. The control device 100 includes a pulse receiving unit 120 for receiving pulses from the encoder 90, and a discharge control unit 110 for controlling the discharge head 60 to discharge the curing liquid with a resolution of distance b which is P times the distance a (where P is a number greater than 1) with respect to the movement of the position of the discharge head 60 relative to the molding tank 30. Let m be the smallest natural number such that P × m is a natural number, and let Q be the integer part of P, so that Q × n + (Q + 1) × (m - n) = P × m is a natural number. The discharge control unit 110 controls the discharge timing of the curing liquid by repeating the above set S1, which consists of a first counting process C1 n times, where each time a Q count pulse is received, the discharge head 60 is considered to have moved a distance b, and a second counting process C2 (m - n times), where each time a (Q + 1) count pulse is received, the discharge head 60 is considered to have moved a distance b, based on the pulses of the encoder 90 received by the pulse receiving unit 120.

[0068] In this three-dimensional molding apparatus 10, the equation Q × n + (Q + 1) × (m - n) = P × m holds true, and the n first counting processes C1 and the (m - n) second counting processes C2 are performed within one set S1. Therefore, each time set S1 is completed, the mismatch between the pulse resolution a of the encoder 90 and the ejection resolution b of the ejection head 60 is resolved. Consequently, errors in the timing of the curing liquid ejection from the ejection head 60 do not accumulate. Therefore, even without calculating the position of the ejection head 60 based on the pulse resolution a of the encoder 90, the accuracy of the ejection timing of the ejection head 60 is guaranteed to a certain extent by repeating set S1.

[0069] In conventional 3D printing systems, to prevent mismatches (non-integer multiple relationships) between the pulse resolution a of the encoder 90 and the ejection resolution b of the ejection head 60, a specially manufactured encoder was used, where the pulse resolution was an integer multiple of the ejection resolution of the ejection head. However, such encoders are expensive and not readily available. Therefore, another method is to determine the position of the ejection head in real time based on the pulse resolution of the encoder, and then perform a calculation to determine the ejection timing of the curing solution based on that result. However, performing such calculations in real time during the printing process may not be fast enough. Even if it is fast enough, such calculations place a very heavy computational load on the 3D printing system.

[0070] In view of these challenges, the three-dimensional molding apparatus 10 according to this embodiment ensures accuracy of the ejection timing of the ejection head 60 by setting a counting process set S1 that resolves the mismatch between the pulse resolution a of the encoder 90 and the ejection resolution b of the ejection head 60 each time the process is completed, and by repeating set S1. With this method, it is not necessary to determine the position of the ejection head 60 in real time based on the pulse resolution a of the encoder 90. With this method, it is sufficient to transmit one ejection signal (here, an ejection signal with a duty cycle of 50%) in response to one counting process C1 or C2. Therefore, the ejection control of the curing liquid from the ejection head 60 can be made simpler.

[0071] In this embodiment, the discharge control unit 110 includes a memory map registration unit 113 in which the order of the n times first count processing C1 and the (m-n) times second count processing C2 in set S1 is registered. The order is determined so as to minimize the number of consecutive times the first count processing C1 and the number of consecutive times the second count processing C2 are performed. With this configuration, the maximum error in the discharge position of the curing liquid during set S1 can be reduced. For example, if the first count processing C1 is performed n times consecutively, and then the second count processing C2 is performed (m-n) times consecutively within set S1, the cumulative error in the discharge position of the curing liquid will continue to increase in the negative direction until the n times the first count processing C1 is completed, and then be eliminated when the (m-n) times the second count processing C2 is completed. In other words, with this order of count processing, the maximum error in the discharge position of the curing liquid during set S1 is larger than in this embodiment.

[0072] However, if the error within set S1 is at a level that does not pose a problem with respect to resolution b, the order does not need to be determined in such a way that the number of consecutive first counting processes C1 and the number of consecutive second counting processes C2 are minimized.

[0073] In this embodiment, the discharge control unit 110 includes a counter 111 that counts pulses from the encoder 90 received by the pulse receiving unit 120, a signal transmitting unit 112 that transmits a discharge signal to discharge the hardening liquid from the discharge head 60, and a memory map registration unit 113 in which a memory map M1 is registered, which associates the count of the counter 111 with the transmission or non-transmission of the discharge signal. The memory map M1 sets the order of the n first counting processes C1 and the (m-n) second counting processes C2 in set S1 based on the setting of whether the discharge signal is transmitted or not. With this configuration, set S1 related to counting processes can be set and executed with a simple configuration of a counter 111 that counts pulses from the encoder 90 and a memory map M1 that sets whether the discharge signal is transmitted or not according to the cumulative pulse count of the counter 111.

[0074] In this embodiment, the discharge control unit 110 includes a reset unit 114 that resets the counter 111 each time one set S1 is completed. With this configuration, it is only necessary to prepare a memory map M1 for one set of set S1, so the memory capacity used by the discharge control unit 110 can be reduced.

[0075] In this embodiment, the encoder 90 is a magnetic encoder. Magnetic encoders are more resistant to harsh environments than optical encoders. For example, if an optical encoder is used in a powder-curing type three-dimensional molding apparatus 10, powder material 200 may adhere to the scale or optical surface, potentially leading to inaccurate measurements or complete inability to measure. With a magnetic encoder encoder 90, even if powder material 200 adheres to the magnetic scale 91 or reading unit 92, there is virtually no risk of inaccurate measurements or complete inability to measure. However, the type of encoder 90 is not particularly limited; for example, the encoder 90 may be an optical linear encoder.

[0076] [Other Embodiments] A preferred embodiment of the present invention has been described above. However, the above-described embodiment is merely illustrative, and the present invention can be implemented in various other forms.

[0077] For example, in the embodiment described above, a memory map M1 corresponding to one set of set S1 was prepared. However, the memory map may be configured to correspond to multiple sets S1.

[0078] In the embodiment described above, the three-dimensional molding apparatus 10 was configured in a so-called line head system. However, the three-dimensional molding apparatus may also be configured in a shuttle head system in which the carriage equipped with the discharge head moves in a direction perpendicular to the leveling direction of the powder material. The technology of the present invention may be applied to the discharge control of the curing liquid while the carriage is moving in the perpendicular direction in a shuttle head system. Furthermore, the moving device may move the supply tank, molding tank, and recovery tank instead of the discharge head and roller unit. The powder material supply device is not limited to a configuration like the supply tank 20, and may, for example, be a type that drops the powder material from above. In addition, the configuration of the three-dimensional molding apparatus 10 described above is merely illustrative. The technology of the present invention is not limited by the embodiment.

[0079] The technology of the present invention may be applied to control the timing of ink ejection in an inkjet printer comprising: a support base for supporting a recording medium; an ejection head for ejecting ink toward the recording medium on the support base; a moving device for moving at least one of the ejection head and the support base to change the position of the ejection head relative to the support base; and an encoder that emits a pulse each time the ejection head or the support base moves a predetermined distance by the moving device.

[0080] 10 Three-dimensional molding device 30 Molding tank 60 Discharge head 80 Moving device 90 Encoder 100 Control device 110 Discharge control unit 111 Counter 112 Signal transmission unit 113 Memory map registration unit (registration unit) 114 Reset unit 120 Pulse receiving unit 200 Powder material a Encoder resolution b Discharge resolution of the discharge head P Ratio of encoder resolution to discharge resolution of the discharge head Q Integer part of P m Smallest natural number such that P × m is a natural number n Number of first counting processes in a set C1 First counting process C2 Second counting process M1 Memory map S1 Set

Claims

1. A molding tank containing powder material; a discharge head for discharging a curing liquid for curing the powder material; a moving device for moving the discharge head or the molding tank and changing the position of the discharge head relative to the molding tank; an encoder that emits a pulse each time the discharge head or the molding tank moves a distance a by the moving device; and a control device, wherein the control device comprises a pulse receiving unit for receiving pulses from the encoder, and a discharge control unit for controlling the discharge head to discharge the curing liquid with a resolution of distance b which is P times the distance a (where P is a number greater than 1) with respect to the movement of the position of the discharge head relative to the molding tank, where m is the smallest natural number such that P × m is a natural number, and Q is a natural number for the integer part of P, and n is a natural number such that Q × n + (Q + 1) × (m - n) = P × m, The discharge control unit controls the discharge timing of the curing liquid by repeating a set of the following: a first counting process n times, in which each time a Q count pulse is received, the discharge head or the molding tank is deemed to have moved by a distance b; and a second counting process (m-n) times, in which each time a (Q+1) count pulse is received, the discharge control unit receives pulses from the encoder received by the pulse receiving unit.

2. The ejection control unit includes a registration unit which stores the order in which the first counting process n times and the second counting process (m-n) times in the set are arranged, and the order is determined such that the number of consecutive times the first counting process and the number of consecutive times the second counting process are minimized, the three-dimensional molding apparatus according to claim 1.

3. The discharge control unit comprises: a counter for counting the pulses of the encoder received by the pulse receiving unit; a signal transmitting unit for transmitting a signal to discharge the hardening liquid to the discharge head; and a registration unit which stores a memory map in which the count of the counter is associated with the transmission or non-transmission of the signal, wherein the memory map sets the order of the first counting process n times and the second counting process (m-n) times in the set according to the setting of the transmission or non-transmission of the signal, the three-dimensional molding apparatus according to claim 1 or 2.

4. The discharge control unit is equipped with a reset unit that resets the counter each time one set is completed, as described in claim 3.

5. The three-dimensional molding apparatus according to any one of claims 1 to 4, wherein the encoder is a magnetic encoder.

6. A method for controlling the discharge timing of the curing liquid from the discharge head in a three-dimensional molding apparatus comprising: a molding tank containing powder material; a discharge head for discharging a curing liquid for curing the powder material; a moving device for moving the discharge head or the molding tank and changing the position of the discharge head relative to the molding tank; and an encoder that emits a pulse each time the discharge head or the molding tank moves by the moving device by a distance a, wherein the discharge timing of the curing liquid is controlled with respect to the movement of the position of the discharge head relative to the molding tank with a resolution of distance b which is P times the distance a (where P is a number greater than 1), and the steps of: finding the smallest natural number m such that P × m is a natural number; and finding an integer n such that Q × n + (Q + 1) × (m - n) = P × m, where Q is a natural number in the integer part of P. A method for controlling the discharge timing of a curing liquid in a three-dimensional molding apparatus, comprising the steps of: repeating a set of a first counting process n times, in which each time a Q count pulse is received from the encoder, the discharge head or the molding tank is deemed to have moved by a distance b; and a second counting process (m-n) times, in which each time a (Q+1) count pulse is received from the encoder, the discharge head or the molding tank is deemed to have moved by a distance b.

7. The method for controlling the discharge timing according to claim 6, further comprising the step of determining the order in which the n times the first counting process and the (m-n) times the second counting process are performed in the set, wherein the order is determined such that the number of consecutive times the first counting process and the number of consecutive times the second counting process are performed are minimized.

8. The method for controlling the discharge timing according to claim 6 or 7, wherein the encoder is a magnetic encoder.

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