WO2017098968A1

WO2017098968A1 - Shaping apparatus

Info

Publication number: WO2017098968A1
Application number: PCT/JP2016/085437
Authority: WO
Inventors: Kenji Karashima; Tatsuya Tada; Hirokazu Usami; Takashi Kase; Satoru Yamanaka; Yuji Wakabayashi
Original assignee: Canon Kabushiki Kaisha
Priority date: 2015-12-10
Filing date: 2016-11-29
Publication date: 2017-06-15
Also published as: JP2017105088A

Abstract

A shaping apparatus forms a three-dimensional solid object by stacking material layers on a stage. The shaping apparatus includes an image forming section that forms the material layers on the basis of given image data; a first conveying body that conveys the material layers formed by the image forming section; a second conveying body that conveys the material layers, which are transferred from the first conveying body, to the stage in a nip section formed between the second conveying body and the first conveying body; and a voltage applying unit that applies, to the nip section, a voltage for transferring the material layers from the first conveying body to the second conveying body, wherein the second conveying body includes a base layer having electric conductivity and a surface layer having an insulating property.

Description

SHAPING APPARATUS

The present invention relates to a shaping apparatus.

In recent years, three-dimensional shaping technique called additive manufacturing (AM), a three-dimensional printer, and rapid prototyping (RP) have been attracting attention (these techniques are referred to an AM technology with the instant specification collectively).
The AM technology is a technology for to shaping a solid object by generating a plurality of shape data obtained by slicing three-dimensional shape data of the solid object, forming layers with a shaping material on the basis of the slice data, and sequentially stacking and firmly attaching the layers of the shaping material. As a main shaping system, there are the following systems according to the definition of the American Society for Testing and Materials (ASTM): vat photopolymerization (VP), material extrusion (ME), fused deposition modeling (FDM), sheet lamination (SL), and the like.
As the AM technology of the sheet lamination type, there is known a powdery three-dimensional shaping method employing an electrophotographic image forming method.
In general, in an electrophotographic system, images are respectively formed on photosensitive bodies for each shaping material and the images are sequentially transferred onto a belt made of a material such as resin to finish the images made of the shaping materials into one (one layer) image.

PTL 2 describes a method of transferring an image on a photosensitive body onto a dielectric belt made of a material having high heat resistance and stacking the image on the dielectric belt. PTL 2 describes a configuration in which a belt, on the surface of a conductive base layer of which a dielectric layer is provided, also functions as a photosensitive body and a stacking belt.
PTL 1 describes a configuration in which an image is transferred from a photosensitive body onto a stacking belt, a base layer of which is made of metal or polymer and a surface layer is coated with Teflon (registered trademark) in order to impart flexibility.

US Patent No. 5088047 (Specification) Japanese Translation of PCT Application No. H8-511217

During laminate shaping, when an image is heated to bring a shaping material forming the image into a melted state and perform stacking, a belt used in a stacking section is requested to have sufficient heat resistance.
In general, a belt is manufactured using a resin material as a main material. Depending on a material, there is a concern that the belt cannot endure temperature at the time when a shaping material is melted or, even if there is no problem in instantaneous or short-term use, the belt stretches in long-time continuous use.
Therefore, it is conceivable to provide a belt used in the stacking section (hereinafter, stacking belt) separately from a belt used in an image forming section that forms an image for one layer (hereinafter, intermediate transfer belt).

However, in the case of a configuration including the intermediate transfer belt and the stacking belt in that way, a process for directly transferring an image from the intermediate transfer belt to the stacking belt is necessary. However, it is difficult to directly transfer the image from the intermediate transfer belt made of a medium resistance material. For example, when the stacking belt is formed of only a base layer of metal, a sufficient voltage cannot be applied because it is likely that electric discharge occurs in a secondary transfer section to the intermediate transfer belt. There is a concern that image disorder and deterioration in transferability are caused. When the stacking belt is formed of only insulative resin such as polymer, since an insulating layer increases in thickness, there is a concern that deterioration in transferability is caused.

An object of the present invention is to improve, in a shaping apparatus including a first conveying body that conveys a material layer formed by an image forming section and a second conveying body that conveys the material layer, which is transferred from the first conveying body, toward a stage, transferability of the material layer from the first conveying body to the second conveying body.

In order to achieve the above object, the present invention is a shaping apparatus that forms a three-dimensional solid object by stacking material layers each made of a shaping material on a stage, the shaping apparatus comprising: an image forming section that forms the material layers on the basis of given image data; a first conveying body that conveys the material layers formed by the image forming section; a second conveying body that conveys the material layers, which are transferred from the first conveying body, to the stage in a nip section formed between the second conveying body and the first conveying body; and a voltage applying unit that applies, to the nip section, a voltage for transferring the material layers from the first conveying body to the second conveying body, wherein the second conveying body includes a base layer having electric conductivity and a surface layer having an insulating property.

According to the present invention, it is possible to improve, in a shaping apparatus including a first conveying body that conveys a material layer formed by an image forming section and a second conveying body that conveys the material layer, which is transferred from the first conveying body, toward a stage, transferability of the material layer from the first conveying body to the second conveying body.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Fig 1 is a diagram schematically showing an overall configuration of a shaping apparatus according to a first embodiment. Fig. 2 is a schematic sectional view showing a stacking belt in the first embodiment. Fig. 3 is a diagram schematically showing an overall configuration of a shaping apparatus according to a second embodiment.

A mode for implementing the present invention will now be exemplarily described with reference to the drawings. It is to be understood that procedures, control parameters, target values, and the like of various types of control including dimensions, materials, shapes, relative arrangements, and the like of respective members described in the following embodiment are not intended to limit the scope of the present invention to the embodiment described below unless specifically stated otherwise.
The present invention relates to a shaping apparatus employing an AM technology, that is, a technology for manufacturing a three-dimensional solid object (shaping object) by stacking thin layers on which shaping materials are two-dimensionally arranged or thin films obtained by melting the shaping materials.
As the shaping material, it is possible to select various materials in accordance with the use, function, and purpose of a solid object to be fabricated. In the present specification, a material constituting a three-dimensional object as a shaping target is referred to as “a build material”. A portion formed of the build material may be referred to as a build body hereinafter. A material constituting a support body for supporting the build body in the process of fabrication (e.g., build supporting an overhang portion from below) is referred to as “a support material”. In addition, in the case where it is not necessary to distinguish between them, a term “shaping material” is simply used. As the build material, it is possible to use thermoplastic resins such as, e.g., polyethylene (PE), polypropylene (PP), ABS, and polystyrene (PS). Further, as the support material, in order to facilitate removal from the build body, it is possible to use a material having thermoplasticity and water solubility preferably. Examples of the support material include carbohydrate, polylactic acid (PLA), polyvinyl alcohol (PVA), and polyethylene glycol (PEG).

In this specification, digital data used for formation of an image for one layer is referred to as “slice data”. An image for one layer made of a shaping material on the basis of the slice data is referred to as “material layer”. The image for one layer is configured by images formed by a plurality of image forming sections. The images formed by the image forming sections are sometimes referred to as “material images”. A structure (i.e., an object represented by image data (there-dimensional shape data) given to the shaping apparatus) to be manufactured using the shaping apparatus is referred to as “shaping target object”. An object (a solid object) manufactured (output) by the shaping apparatus is referred to as “shaping object”. When the shaping object includes a support body, a structure, which is a portion excluding the support body, is a solid object of the shaping target object.

<First Embodiment>
<Overall configuration of a shaping apparatus>
An overall configuration of a shaping apparatus according to a first embodiment of the present invention is explained with reference to Fig. 1. Fig. 1 is a diagram schematically showing the overall configuration of the shaping apparatus according to this embodiment.
As shown in Fig. 1, a shaping apparatus 1 schematically includes a control unit U1, an image forming unit U2, and a stacking unit U3. The control unit U1 is a unit that performs processing for generating slice data of a plurality of layers from three-dimensional shape data of a shaping target object, control of sections of the shaping apparatus 1, and the like. The image forming unit U2 is a unit that forms a material layer made of a shaping material using an electrophotographic process. The stacking unit U3 is a unit that forms a shaping object by stacking and firmly attaching, in order, material layers of a plurality of layers formed by the image forming unit U2. Note that the unit configuration shown in Fig. 1 is only an example. The present invention can also be suitably applied in a shaping apparatus employing another configuration.

<Control unit>
The configuration of the control unit U1 is explained below.
As shown in Fig. 1, the control unit U1 includes, as functions thereof, a three-dimensional-shape-data input section U10, a slice-data calculating section U11, an image-forming-unit control section U12, and a stacking-unit control section U13.
The three-dimensional-shape-data input section U10 includes a function of receiving three-dimensional shape data of a shaping target object from an external apparatus (e.g., a computer). As the three-dimensional shape data, data created and output by a three-dimensional CAD, a three-dimensional modeler, a three-dimensional scanner, and the like can be used. A file format of the three-dimensional shape data may be any format. However, for example, a stereolithography (STL) file format is desirably used.

The slice-data calculating section U11 includes a function of slicing, at a predetermined pitch, the shaping target object represented by the three-dimensional shape data to calculate sectional shapes of layers and generating, on the basis of the sectional shapes, data (slice data) used for image formation in the image forming unit U2. Further, the slice-data calculating section U11 analyzes the three-dimensional shape data or slice data of upper and lower layers, determines presence or absence of an overhang section (a portion floating in the air), and includes data used for formation of the support body in the slice data according to necessity.
The image-forming-unit control section U12 includes a function of controlling an image forming process in the image forming unit U2 on the basis of the slice data generated by the slice-data calculating section U11. The stacking-unit control section U13 includes a function of controlling a stacking process in the stacking unit U3.

Although not shown in the figure, the control unit U1 includes an operation section, a display section, and a storing section as well. The operation section includes a function of receiving an instruction from a user. For example, ON/OFF of a power supply, various kinds of setting of the apparatus, an operation instruction, and the like can be input to the operation section. The display section includes a function of performing information presentation to the user. For example, the display section can present various setting screens, error messages, an operation status, and the like. The storing section includes a function of storing three-dimensional shape data, slice data, and various setting values.
The control unit U1 can be configured by, in terms of hardware, a computer including a central processing unit (CPU), a memory, an auxiliary storage device (a hard disk, a flash memory, etc.), an input device, a display device, and various I/Fs. The functions U10 to U13 are realized by the CPU reading and executing a program stored in the auxiliary storage device or the like and controlling necessary devices. However, a part or all of the functions may be configured by circuits such as an ASIC and an FPGA. Alternatively, the control unit U1 may cause other computers to execute the functions using technologies such as cloud computing and grid computing.

<Image forming unit>
The configuration of the image forming unit U2 is explained.
The image forming unit U2 is a unit that forms a material layer made of a shaping material using an electrophotographic process. The electrophotographic process is a method of forming a desired image by a series of process for charging a photosensitive body (an image bearing body), forming a latent image on the photosensitive body with exposure, depositing developer particles in a latent image portion on the photosensitive body, and forming a developer image on the photosensitive body. A principle of the electrophotographic process in the shaping apparatus is common to a principle used in a 2D printer such as a copying machine. However, characteristics of the shaping material used as the developer in the shaping apparatus are different from characteristics of a toner material. Therefore, process control and member structure in the 2D printer often cannot be directly used in the shaping apparatus.

As shown in Fig. 1, the image forming unit U2 includes a first image forming section 10a, a second image forming section 10b, an intermediate transfer belt 11 functioning as a first conveying body, a belt cleaning device 12, a first transfer device 104a, and a second transfer device 104b. The image forming section 10a and the image forming section 10b are image forming means for forming material images using different shaping materials. The image forming section 10a and the image forming section 10b respectively include photosensitive bodies, charging devices, exposing devices, developing devices, and cleaning devices.
The

image forming sections

10a and 10b are disposed side by side along the surface of the intermediate transfer belt 11. The image forming section 10b is located further on a downstream side than the image forming section 10a in a rotating direction of the intermediate transfer belt 11 (a moving direction of the surface of the intermediate transfer belt).

(Image forming sections)
Concerning details of the

image forming sections

10a and 10b, detailed explanation is omitted assuming that a general electrophotographic system is used.
(Transfer devices)
The

transfer devices

104a and 104b are transfer means for transferring the material images, which are formed by the

image forming sections

10a and 10b, onto the surface of the intermediate transfer belt 11.
The

transfer devices

104a and 104b are disposed on the opposite side of the photosensitive bodies inside the

image forming sections

10a and 10b across the intermediate transfer belt 11. A voltage having polarity opposite to charging polarity of the material images on the photosensitive bodies is applied to the

transfer devices

104a and 104b, whereby the material images on the photosensitive bodies are electrostatically transferred to the intermediate transfer belt 11 side. The transfer from the photosensitive bodies to the intermediate transfer belt 11 is also referred to as primary transfer. Note that, in this embodiment, a roller transfer system is used. However, a transfer system making use of corona discharge and a transfer system other than the electrostatic transfer system may be used.

(Intermediate transfer belt)
The intermediate transfer belt 11 is a transfer body to which the material images, which are formed by the image forming sections 10, are transferred from the image forming sections 10. After a material image made of the structure material is transferred from the image forming section 10a to the intermediate transfer belt 11, a material image made of a support material is transferred to the intermediate transfer belt 11 from the image forming section 10b, which is located further on the downstream side than the image forming section 10a, such that this material image is aligned on the intermediate transfer belt 11 with the material image transferred from the image forming section 10a.
Consequently, a material layer for one image (one layer) is formed on the surface of the intermediate transfer belt 11.

The intermediate transfer belt 11 is an endless belt having volume resistivity of approximately 1 × 10⁸ to 10¹¹ Ω・cm made of a material such as resin or polyimide. As shown in Fig. 1, the intermediate transfer belt 11 is stretched on a plurality of

rollers

110 and 111. Note that a tension roller may be provided besides the

rollers

110 and 111 to make it possible to adjust tension of the intermediate transfer belt 11.
The roller 111 is a driving roller. During image formation, the intermediate transfer belt 11 is rotated counterclockwise in the figure by a driving force of a not-shown motor. The roller 110 is a roller including an intermediate-resistance elastic layer that forms a transfer nip section (hereinafter, two-dimensional transfer section) N between the roller 110 and a secondary transfer counter roller 31 of the stacking unit U3. The roller 110 is hereinafter referred to as secondary transfer roller 110. The secondary transfer roller 110 is equivalent to a first member. The secondary transfer counter roller 31 is equivalent to a second member.
When the material layer is transferred from the intermediate transfer belt 11 to a stacking belt 30, a voltage having polarity same as a charging polarity of the shaping material configuring the material layer is applied to the secondary transfer roller 110 from a power supply 13 functioning as voltage applying means. The material layer is transferred onto the stacking belt 30.

(Belt cleaning device)
The belt cleaning device 12 is means for cleaning the shaping material remaining on the surface of the intermediate transfer belt 11. In this embodiment, a cleaning device of a blade type for scraping off a material with a cleaning blade brought into contact with the intermediate transfer belt 11 is adopted. However, a cleaning device of other types such as a brush type or an electrostatic attraction type may be used.

<Stacking unit>
The configuration of the stacking unit U3 is explained.
The stacking unit U3 is a unit that receives the material layers formed by the image forming unit U2, and stacks and firmly attaches the material layers in order to thereby form a shaping object.
As shown in Fig. 1, the stacking unit U3 includes the stacking belt 30 functioning as a second conveying body, the secondary transfer counter roller 31, a heater 33, and a stage 34. The configurations of the sections of the stacking unit U3 are explained in detail below.

(Stacking belt)
Fig. 2 is a schematic sectional view showing the stacking belt 30 in this embodiment.
The stacking belt 30 is a member that receives the material layer formed by the image forming unit U2 from the intermediate transfer belt 11 and bears and conveys the material layer to a stacking position. The stacking position is a position where a stacked surface of a shaping object in the process of stacking is brought into contact with the material layers for stacking the material layers (piling up the material layers onto the shaping object in the process of stacking). In the configuration shown in Fig. 1, a portion sandwiched by the heater 33 and the stage 34 of the stacking belt 30 corresponds to the stacking position.

The stacking belt 30 is an endless belt, a base layer 30a of which is formed at thickness of 40 to 600 μm from metal having electric conductivity and relatively high thermal conductivity and a surface layer 30b of which is formed at thickness of 10 to 100 μm from an insulating resin material or the like. In a secondary transfer section N, the base layer 30a and the secondary transfer roller 110 are configured to be opposed to each other across the surface layer 30b and the intermediate transfer belt 11. The surface layer 30b of the stacking belt 30 and the intermediate transfer belt 11 are in contact with each other. Here, having electric conductivity means a characteristic having a volume resistivity of 1 × 10⁵ Ω・cm or less at the room temperature. “Insulating” means a characteristic having a volume resistivity of 1 × 10¹⁰ Ω・cm or more at the room temperature. As the entire stacking belt including the base layer 30a and the surface layer 30b, the volume resistivity at the room temperature is desirably equal to or higher than 1 × 10⁵ Ω・cm and equal to or lower than 1 × 10¹² Ω・cm and more desirably equal to or higher than 1 × 10⁶ Ω・cm and equal to or lower than 1 × 10⁹ Ω・cm. If the volume resistance of the entire stacking belt is within this range, it is possible to reduce charge-up and leak in the secondary transfer section and suppress image disorder and deterioration in transferability.
The base layer 30a more desirably has thickness of 60 to 400 μm. The surface layer 30b more desirably has thickness of 15 to 80 μm. The base layer 30a is desirably made of stainless steel, nickel, copper, or the like. The surface layer 30b is desirably made of PTFE, PFA, FEP, ETFE, polyimide, or the like. The PTFE is polytetrafluoro-ethylene, the PFA is tetrafluoroethylene-perfluoro alkyl vinyl ether copolymer, and the FEP is tetrafluoroethylene-hexafluoropropylene copolymer. The ETFE is ethylene-tetrafluoroethylne copolymer.

As shown in Fig. 1, the stacking belt 30 is stretched on the secondary transfer counter roller 31 and a plurality of

rollers

301, 302, 303, and 304. The

rollers

303 and 304 are rollers made of metal. The

rollers

303 and 304 are grounded by a not-shown component and disposed to be in contact with the conductive base layer 30a of the stacking belt 30, whereby the base layer 30a of the stacking belt 30 is grounded.
At least one of the

rollers

301 and 302 are driving rollers. The stacking belt 30 is rotated clockwise in the figure by a driving force of a not-shown motor. The

rollers

303 and 304 are a roller pair that plays a role of adjusting the tension of the stacking belt 30 and keeping a portion of the stacking belt 30 passing the stacking position (i.e., the material layers during stacking) flat.

As a characteristic of this embodiment, the base layer 30a of the stacking belt 30 is made of a material excellent in electric conductivity and is electrically grounded. Consequently, it is possible to cause the stacking belt 30 as a counter electrode in the configuration of the secondary transfer section N that applies a voltage to the secondary transfer roller 110. Further, since the insulating layer is provided on the surface layer 30b of the stacking belt 30, it is possible to suppress occurrence of electric discharge and deterioration in transferability in the secondary transfer section N.
Consequently, it is possible to satisfactorily perform transfer of the material layers from the intermediate transfer belt 11 to the stacking belt 30 in the secondary transfer section N.

It is assumed that the stacking belt 30 is formed of only insulative resin such as polymer. In such a case, when the material layer on the stacking belt front surface is heated from the belt rear surface side by a heater, heat is less easily transferred because the heat is transferred via the stacking belt. Therefore, the heater needs to be set to high temperature more than necessary. There is a concern that the heating takes time.
On the other hand, the base layer 30a of the stacking belt 30 in this embodiment is made of a material having high thermal conductivity compared with heat resistant resin or the like. Therefore, the heat from the heater 33 on the rear surface side can be efficiently transferred to the material layer present on the surface layer 30b. Consequently, it is possible to suppress excessive heating and an increase in a heating time in the heater 33.
Note that, whereas the thermal conductivity of metal is approximately 25 W/m・K in stainless steel, approximately 26 W/m・K in nickel, and approximately 370 W/m・K in copper, the thermal conductivity of the insulative resin is approximately 0.3 W/m・K in polyimide and approximately 0.26 W/m・K in PEEK.

(Secondary transfer counter roller)
The secondary transfer counter roller 31 is a roller for forming the secondary transfer section N between the intermediate transfer belt 11 and the stacking belt 30. By configuring the intermediate transfer belt 11 and the stacking belt 30 to be held and closely attached between the secondary transfer counter roller 31 and the secondary transfer roller 110, the secondary transfer section N is formed between the intermediate transfer belt 11 and the stacking belt 30.
(Heater)
The heater 33 is temperature control means for controlling the temperature of the material layer conveyed to the stacking position. As the heater 33, for example, a ceramic heater and a halogen heater can be used.
The temperature control means is not limited to the heater for heating and may further include a component for positively reducing the temperature of the material layer through heat radiation or cooling. Note that the lower surface (a surface on a side opposed to the stacking belt 30) of the heater 33 is a plane. The heater 33 also plays roles of a guide for the stacking belt 30 that passes the stacking position and a pressing member that applies equal pressure to the material layer.

(Stage)
The stage 34 is a plane table on which the shaping object is stacked. The stage 34 is configured to be capable of moving in the up-down direction (a direction perpendicular to the belt surface of the stacking belt 30 (the stage surface (upper surface)) in the stacking position) by a not-shown actuator. The material layers on the stacking belt 30 carried and conveyed to the stacking position are held between the stage 34 and the heater 33 and heating and pressurization are performed (and heat discharge or cooling is performed according to necessity) to transfer the material layers from the stacking belt 30 side to the stage 34. The material layer of a first layer is directly transferred onto the stage 34. The material layers of second and subsequent layers are piled up on the shaping object on the stage. In this way, in this embodiment, stacking means for stacking the material layers is configured by the heater 33 and the stage 34.

(Temperature adjusting means)

Heating heaters

37a and 37b, which are heating means, are mechanisms for adjusting the temperature of the shaping material remaining on the stacking belt 30 in order to remove the shaping material remaining on the stacking belt 30 after the stacking.
The

heating heaters

37a and 37b are disposed to hold a belt portion stretched between the roller 302 and the secondary transfer counter roller 31 in the stacking belt 30. As a process later than the stacking process, the

heating heaters

37a and 37b heat (in the case of ABS, heat to 140℃ or more) and melt the shaping material remaining on the stacking belt 30 after the stacking.

(Cleaning means)
Web cleaning means 51 includes a web made of nonwoven fabric and removes the shaping material remaining on the stacking belt 30 by scraping the surface of the stacking belt 30 with the web further on the rotating direction downstream side of the intermediate transfer belt 11 than the stacking position.
The web cleaning means 51 includes a pair of rollers. The web is wound on one roller of the pair of rollers. One end of the web is fixed to the other roller. The web is disposed to be in contact with the surface of the stacking belt 30.
By winding the web while rotating the other roller to fix the speed of the web in a contact section with the surface of the stacking belt 30, the shaping material remaining on the stacking belt 30 is scraped off and removed from the surface of the stacking belt 30.

<Operation of the shaping apparatus>
The operation of the shaping apparatus in this embodiment is explained.
Assuming that generation processing for slice data by the control unit U1 has been completed, a process for forming material layers of respective layers and a process for stacking the material layers are explained in order.
(Image forming process)
First, the control unit U1 causes the transfer device 104a primarily transfers a material layer formed by an electrostatic system in the image forming section 10, onto the intermediate transfer belt 11. Two material images formed by the respective

image forming sections

10a and 10b are aligned and transferred on the intermediate transfer belt 11, and a material layer for one layer made of a structure material and a support material is formed.

(Stacking process)
While the operation for forming the material layer is performed as explained above, the stacking belt 30 and the intermediate transfer belt 11 are rotating in synchronization at the same speed in a state in which the stacking belt 30 and the intermediate transfer belt 11 are in contact with each other. The control unit U1 applies a predetermined transfer voltage to the secondary transfer roller 110 according to timing when the front end of the material layer born on the intermediate transfer belt 11 reaches the secondary transfer section N and causes the secondary transfer roller 110 to transfer the material layer to the stacking belt 30.
The material layer transferred onto the stacking belt 30 is conveyed to the stacking position by the rotation of the stacking belt 30. The control unit U1 stops the rotation driving of the stacking belt 30 and at timing when the material layer on the stacking belt 30 reaches the stacking position and positions the material layer in the stacking position.
Thereafter, the control unit U1 lifts the stage 34 (brings the stage 34 close to the surface of the stacking belt 30) and brings the stage surface (in the case of a first layer) or the upper surface of a shaping object formed on the stage surface (in the case of second or subsequent layers) into contact with the material layer on the stacking belt 30.

In this state, the control unit U1 controls the temperature of the heater 33 according to a predetermined temperature control sequence. Specifically, first, the control unit U1 performs, for a predetermined time, a first temperature control mode for heating the heater 33 to a first target temperature and thermally melts the shaping material forming the material layer. Consequently, the material layer is softened and the stage surface or the upper surface of the shaping object being shaped and the sheet-like material layer adhere to each other. Thereafter, the control unit U1 performs, for a predetermined time, a second temperature control mode for controlling the heater 33 to reach a second target temperature lower than the first target temperature and solidifies the softened material layer. After the second temperature control mode ends, the control unit U1 lowers the stage 34 (separates the stage 34 from the stacking belt 30). In this way, the stacking of the material layer for one layer is completed.

The temperature control sequence, the target temperatures, the heating times, and the like are set according to characteristics of shaping materials used for the image formation. For example, the first target temperature in the first temperature control mode is set to a value higher than a highest temperature of melting points or glass transition points of the shaping materials used for the image formation. On the other hand, the second target temperature in the second temperature control mode is set to a value lower than a lowest temperature of crystallization temperatures of the shaping materials or glass transition points of amorphous materials used for the image formation.
By performing such temperature control, after thermally plasticizing (softening), in a common melting temperature region, the entire material layers in which a plurality of kinds of shaping materials having different thermal melting characteristics are mixed, it is possible to solidify the entire material layers in a common solidifying temperature region. Therefore, it is possible to stably perform melting and solidification of the material layers in which the plurality of kinds of shaping materials are mixed.

Note that, in the first temperature control mode and the second temperature control mode, if a control region of temperatures is too wide, it takes time to stabilize the temperature control. A stacking process time is consumed more than necessary. Therefore, as a control region for the first target temperature, it is desirable to set the highest temperature of the melting points and the glass transition points of the shaping materials used for the image formation as a lower limit temperature and set an upper limit temperature to approximately +50℃ of the lower limit temperature. Similarly, as a control region of the second target temperature, it is desirable to set the lowest temperature of the crystallization temperatures of the shaping materials or the glass transition points of the amorphous materials used for the image formation as an upper limit temperature and set a lower limit temperature to approximately -50℃ of the upper limit temperature. For example, when ABS (the glass transition point: 130℃) is used as the structure material and maltotetrose (the glass transition point: 156℃) is used as the support material, the temperatures may be set as follows: the control region of the first target temperature may be set to a lower limit 150℃ to an upper limit 190℃ and the control region of the second target temperature may be set to a lower limit 90℃ to an upper limit 130℃.

After the stacking of the material layers ends, execution of a cleaning process for removing the shaping material remaining on the stacking belt 30 is started.
When the residual shaping material passes a contact region of the stacking belt 30 and the roller 302 while remaining adhering on the stacking belt 30, the residual shaping material is heated by the

heating heaters

37a and 37b (in the case of the ABS and the maltotetrose, heated to 160℃ or more) and melted.
Subsequently, the residual shaping material is scraped off by the web cleaning means 51 in contact with the stacking belt 30 and removed from the stacking belt 30.
After the cleaning process ends, execution of an image forming process for forming the next material layer is started.

A desired shaping object is formed on the stage 34 by repeating the image forming process and the stacking process a necessary number of times.
Finally, a desired shaping target object can be obtained by detaching the manufactured shaping object from the stage 34 and removing the water-soluble support body with hot water or the like. After the support body is removed, a final product may be obtained by applying predetermined processing such as surface treatment and assembly to the shaping target object.

As explained above, in this embodiment, the stacking belt 30 is formed in a two-layer configuration including the base layer 30a of metal and the surface layer 30b having an insulating property.
By forming the base layer 30a with the material excellent in electric conductivity and electrically grounding the base layer 30a in this way, it is possible to cause the stacking belt 30 to function as a counter electrode of the secondary transfer roller 110 in the secondary transfer section N. By forming the surface layer 30b as the insulating layer, it is possible to suppress occurrence of electric discharge and deterioration in transferability in the secondary transfer section N. Consequently, it is possible to satisfactorily perform the transfer of the material layer in the secondary transfer section N. Therefore, according to this embodiment, it is possible to improve transferability of the material layer from the intermediate transfer belt 11 to the stacking belt 30 in the secondary transfer section N.
In this embodiment, the base layer 30a of the stacking belt 30 is made of metal. Therefore, the stacking belt 30 is excellent in heat resistance. Moreover, heat from the heater 33 on the belt rear surface side can be efficiently transferred to the material layer present on the surface layer 30b. Consequently, it is possible to suppress excessive heating and an increase in a heating time in the heater 33.

In this embodiment, the base layer 30a of the stacking belt 30 is electrically grounded and a voltage is applied to the secondary transfer roller 110 to transfer the material layer from the intermediate transfer belt 11 to the stacking belt 30. However, the present invention is not limited to this. That is, a voltage for transferring the material layer from the intermediate transfer belt 11 to the stacking belt 30 only has to be applied to the secondary transfer section N. For example, a voltage may be applied to the secondary transfer counter roller 31 and the secondary transfer roller 110 may be electrically grounded. Voltages may be respectively applied to the secondary transfer roller 110 and the secondary transfer counter roller 31. In this case, the voltages are desirably applied to the secondary transfer roller 110 and the secondary transfer counter roller 31 such that a potential difference for transferring the material layer from the intermediate transfer belt 11 to the stacking belt 30 is formed between the rollers.
In this embodiment, the base layer 30a of the stacking belt 30 is made of metal. However, the present invention is not limited to this. The base layer 30a only has to be made of a material excellent in heat resistance and electric conductivity. The belt-like member is used as the first conveying body and the second conveying body. However, the present invention is not limited to this. Another form such as a drum-like member or a plate-like member may be used.

<Second Embodiment>
Fig. 3 is a diagram schematically showing the overall configuration of a shaping apparatus according to a second embodiment of the present invention.
Note that, in this embodiment, since components other than a stacking unit are the same as the components in the first embodiment, components different from the components in the first embodiment are explained. Explanation of components same as the components in the first embodiment is omitted.

In the first embodiment explained above, the secondary transfer counter roller 31 is opposed to and brought into contact with the secondary transfer roller 110 to configure the secondary transfer section N. On the other hand, in this embodiment, a grounded roller 35 made of metal is provided instead of the secondary transfer counter roller 31. The roller 35 and the

rollers

301, 302, 303, and 304 are equivalent to a tension member.
The roller 35 is not opposed to and brought into contact with the secondary transfer roller 110. A portion stretched by the roller 35 and the roller 301 in the stacking belt 30 is opposed to and brought into contact with the secondary transfer roller 110 across the intermediate transfer belt 11 to configure the secondary transfer section N.
In this embodiment, as in the first embodiment, the conductive base layer 30a of the stacking belt 30 comes into contact with the

rollers

35, 303, and 304 to change to a grounded state and function as a counter electrode of the secondary transfer roller 110, whereby secondary transfer is performed.

According to this embodiment, it is not always necessary to provide the secondary transfer counter roller 31 in the first embodiment. Therefore, it is possible to improve flexibility of configuration design in the shaping apparatus. It is possible to achieve a reduction in the size of the shaping apparatus.
In this embodiment, the roller 35 is provided. However, the present invention is not limited to this. For example, the stacking belt 30 may be stretched by the

rollers

301, 302, 303, and 304, and a portion that is stretched between the

rollers

301 and 302 may be opposed to and brought into contact with the secondary transfer roller 110 across the intermediate transfer belt 11, to thereby configure the secondary transfer section N. Any configuration may be employed so long as the position of the secondary transfer section N is set in a range in which the influence of heat by the stacking unit U3 does not affect the image forming unit U2.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2015-241367, filed on December 10, 2015, which is hereby incorporated by reference herein in its entirety.

Claims

A shaping apparatus that forms a three-dimensional solid object by stacking material layers each made of a shaping material on a stage, the shaping apparatus comprising:
an image forming section that forms the material layers on the basis of given image data;
a first conveying body that conveys the material layers formed by the image forming section;
a second conveying body that conveys the material layers, which are transferred from the first conveying body, to the stage in a nip section formed between the second conveying body and the first conveying body; and
a voltage applying unit that applies, to the nip section, a voltage for transferring the material layers from the first conveying body to the second conveying body, wherein
the second conveying body includes a base layer having electric conductivity and a surface layer having an insulating property.
The shaping apparatus according to claim 1, wherein the base layer is made of metal.
The shaping apparatus according to claim 1 or 2, wherein volume resistivity of the second conveying body at a room temperature is equal to or higher than 1 × 10⁵ Ω・cm and equal to or lower than 1 × 10¹² Ω・cm.
The shaping apparatus according to any one of claims 1 to 3, wherein the shaping apparatus includes, in the nip section, a first member disposed to be opposed to the second conveying body across the first conveying body.
The shaping apparatus according to claim 4, wherein the shaping apparatus includes, in the nip section, a second member disposed to hold the first conveying body and the second conveying body between the second member and the first member.
The shaping apparatus according to claim 4, wherein
the second conveying body is a belt-like member, and the shaping apparatus includes a plurality of tension members on which the second conveying body is stretched, and
the nip section is provided between the first member and the second conveying body which is stretched between two tension members adjacent to each other among the plurality of tension members.
The shaping apparatus according to any one of claims 4 to 6, wherein the voltage applying unit applies a voltage between the base layer and the first member.
The shaping apparatus according to any one of claims 4 to 7, wherein
the base layer is electrically grounded, and
the voltage applying unit applies a voltage to the first member.