FIELD OF THE INVENTION

The present invention relates to apparatus, hereinafter “rapid production apparatus”, (RPA) for producing a 3-dimensional object by sequentially forming thin layers of material, one on top of the other, responsive to data defining the object.

BACKGROUND OF THE INVENTION

Rapid production apparatus (RPAs) form objects by sequentially forming thin layers, hereinafter “construction layers”, of construction material one on top of the other responsive to data, hereinafter “construction data”, defining the objects. There are numerous and varied types of RPAs and different methods by which they form the thin construction layers from which they build an object.

One type of RPA, conventionally referred to as an “ink-jet RPA”, “prints” each layer of an object it builds. To form a given layer, the ink-jet RPA controls at least one dispenser, referred to as a “printing head”, to dispense at least one construction material (CM), hereinafter a “building material” (BM), in liquid form in a pattern responsive to construction data for the object and then solidifies the dispensed material. Generally, the layer is printed in the shape of a cross section of the object. Building material in adjacent, contiguous construction layers is printed in the shape of thin cross sections of the object that are displaced relative to each other by a small incremental distance along a same direction, hereinafter referred to as a “stacking direction”, relative to the object. The incremental distance is generally equal to the thickness of the layers.

For convenience of exposition, the cross sections of the object in whose shapes the construction layers are formed are assumed to be parallel to the xy-plane of a suitable coordinate system and the stacking direction is in the z-direction of the coordinate system. Optionally, the building material is a photopolymer, which is hardened after dispensing by exposure to suitable electromagnetic radiation, typically UV radiation.

For many construction objects, because of the complexity and/or shape of the objects, construction layers comprising only BM printed in the shape of cross sections of the construction objects are not completely self-supporting and require support during construction of the object. For such cases, at least one additional construction material CM, hereinafter referred to as “support material” (SM) is printed as required in suitable regions of each layer, to provide support for the building material in following layers. The support material and/or a shape in which it is formed, is such that upon completion of the object it can be removed from the object without substantially damaging the building material. In some embodiments, the support material, like the building material, is also a photopolymer.

An ink-jet type of RPA typically comprises at least one ink-jet printing head comprised in a “printing head block” that is mounted to a “shuttle”. Each printing head has an array of one or more output orifices and is controllable to dispense construction material, BM and/or SM, from each orifice independently of dispensing construction material from the other orifices. The construction material generally comprises one or more types of photopolymer materials typically stored in at least one supply cartridge. A suitable configuration of pipes and pumps transports the material or materials from the at least one supply cartridge to one or more reservoirs in the printing head block from which the at least one ink-jet printing head receives the construction material. Optionally, to maintain appropriate viscosity of the at least one photopolymer, a controller controls at least one heater, optionally mounted to the printing block, printing head and/or reservoir, to heat the photopolymer to a suitable operating temperature. The one or more types of photopolymers may, generally, be dispensed in any combination, separately or together, simultaneously or consecutively.

During construction of an object, a controller controls the shuttle to repeatedly move over a support surface, hereinafter a “construction platform”, parallel to the x-y plane on which the object is formed by the RPA. The support surface and shuttle are generally housed in an at least partially enclosed “construction hangar” that protects the object while it is being built. As the shuttle moves, the controller controls each printing head to dispense construction material selectively through its orifices responsive to construction data defining the object, to print one construction layer of the object on top of the other on the construction platform.

Optionally, in moving the shuttle over the support surface during production of a construction layer, the controller controls the shuttle to move back and forth along a “scanning direction” conventionally defined as the x-direction. Optionally, at any one or more reversals of the shuttle along the x-direction, the controller increments displacement of the shuttle in a direction perpendicular to the scanning direction, in a direction referred to as “displacement” direction, conventionally the y-direction. Following production of a given construction layer, either the construction platform is lowered or the shuttle raised, along the stacking direction by a distance equal to a thickness of a next construction layer to be produced over the just formed given layer.

Mounted to the shuttle, adjacent to the printing head block are one or more sources of electromagnetic radiation, optionally UV radiation, for curing the photopolymer construction material printed in each construction layer. Also, optionally, mounted to the shuttle adjacent to the at least one printing head block is a “leveling roller” which levels newly printed layers of construction material to a predetermined layer height by removing surplus material from the layer. The surplus material removed from the layer is wiped off the roller by a “cleaning wiper” and gathered in a waste container comprised in the shuttle. Alternatively, the support surface moves.

Configurations of ink-jet type RPAs are described in U.S. Pat. No. 6,193,923 (Leyden), U.S. Pat. Nos. 6,259,962, 6,658,314, 6,569,373, 6,850,334 and U.S. applications Ser. Nos. 10/716,426, 10/336,032 and PCT Publication WO 2004/096527, the disclosures of which are incorporated herein by reference.

SUMMARY OF THE INVENTION

An aspect of some embodiments of the invention, relates to providing improved control of dispensing BM and/or SM material by a printing head in the RPA by providing improved control of the temperature of dispensed material.

Temperature of a BM or SM material dispensed by a printing head tends to decrease as a rate at which the printing head dispenses the material increases, because a time period available to a conventional RPA heater to bring the material to a desired temperature decreases as dispensing rate increases. The temperature decrease in general adversely affects viscosity of the material and thereby its ability to flow and form a homogenous, quality construction layer that bonds properly to adjacent construction layers. If dispensing rates vary during production of an object or objects, it is generally difficult to compensate for reduced heating time by controlling temperature of the heaters.

In accordance with an embodiment of the invention, an RPA is provided with a heating unit hereinafter referred to as a “flow-heater” or “pre heater” that substantially reduces dependence of temperature at which BM or SM is dispensed by its printing head on a rate at which the material is dispensed. In accordance with an embodiment of the invention, the flow-heater comprises a heat sink having a relatively large thermal capacity that is formed with an internal flow channel through which material dispensed by the printing head flows to reach the reservoir in the printing head. A heating element provides heat to the heat sink to maintain the temperature of the heart sink at a temperature at which it is desired that the BM or SM should be dispensed. The flow channel is made sufficiently long so that for a range of material dispensing rates at which the RPA operates, during passage of the material through the channel, temperature of the material equalizes to that of the heat sink. In some embodiments of the invention a pre heater is supplemented or replaced by a flow-heater that heats the BM or SM material after it leaves the reservoir.

An aspect of some embodiments of the invention relates to a method and apparatus for removing finished objects from an RPA construction platform.

In general, before beginning construction of an object (or objects), an RPA lays down a “foundation” on the RPA construction platform. The object is then built by depositing layers of BM or SM on the foundation and planning off the deposited layers with an RPA leveling roller. The foundation provides a relatively accurately planar surface parallel to the x-y motion of the RPA printing head block on which to build the object and provides material between the object and the surface of the construction platform that enables the object to be scraped off the construction platform without damaging the object. Conventionally, each finished object is removed by scraping and/or peeling the foundation off the construction platform using a conventional scraping tool such as a paint scraper. Whereas to save construction costs and time it is advantageous for the foundation to be as thin as possible, the foundation is formed sufficiently thick so that it and the object may be scraped or lifted off the construction platform without damage to the object.

In accordance with an embodiment of the invention, a “spatula shovel” is provided for removing finished objects from the construction platform. The spatula shovel comprises a relatively thin plate formed with a straight, relatively sharp leading edge and optionally has a length and width substantially equal respectively to the length and width of the construction platform. Optionally, the structural shape of the spatula is reinforced by upturned edges. The sharp front edge of the spatula shovel is forced between the foundation and the construction platform to peel and/or scrape and lift off the foundation and finished objects from the construction platform and functions as a support and carry tray for the objects once they are lifted off the construction platform. The leading edge is sufficiently sharp and the plate sufficiently thin yet rigid so that the objects are relatively easily removed without damage.

The inventors have found that using a spatula shovel in accordance with an embodiment of the invention to remove finished objects from a construction platform generally enables the objects to be removed more easily and with less chance of damage than by using a conventional scraping tool. As a result, a foundation on which objects are formed may be made substantially thinner than conventional foundations. The thinner foundation provides savings in production materials and object production time. An aspect of some embodiments of the invention relates to providing different production modes for an object printed by the RPA so that a user of the RPA can tailor production time and quality of an object to the user's needs.

In accordance with an embodiment of the invention, an RPA is configured to operate selectively in different production modes chosen from a plurality of production modes. Optionally, the plurality of production modes comprises three production modes: a draft mode, a standard mode and a high quality mode. For each of the different production modes, production parameters that determine RPA operation and affect quality and rate of production of an object are adjusted as required to assume values that correspond to the production mode and are compatible with each other.

Cost of an object produced by an RPA depends upon amounts of material used in producing the object and its production time. Whereas, in general there is little control over an amount of BM required to produce an object, because the amount is determined by the object's volume, an amount of SM required to produce the object depends, in general, upon the object's orientation on the RPAs production platform.

An aspect of some embodiments of the invention relates to providing an algorithm for determining orientation of an object to be built on an RPA construction platform in order to reduce an amount of SM used in its production.

Production time of an object or objects is a function, inter alia, of a number of scan passes, i.e. passes along, optionally, the scanning, x-direction, that the shuttle makes in order to produce the object or objects, and the lengths of the scan passes. The number and lengths of the scan passes are functions of orientation and relative position of the objects on the construction platform.

An aspect of some embodiments of the invention relates to a method for determining relative orientation of objects to be built by an RPA, and relative position of the objects on the RPAs construction platform in order to reduce the number and lengths of scan passes used to produce the objects.

Hereinafter, an orientation on an RPA construction platform of a single object to be produced by the RPA and a configuration of orientations and relative positions of a plurality of objects to be produced on the RPA construction platform are referred to as “build configurations”.

An aspect of some embodiments of the invention relates to providing methods of calibrating a printing head block so that CM material is accurately deposited at desired locations during production of an object.

To control CM deposition so that the CM is deposited accurately at desired locations during production of an object, position of an RPA shuttle during its motion along scanning and displacement directions should accurately be known and timing of activation of printing heads mounted in the shuttle to dispense CM material should accurately be coordinated with the shuttle motion and position. In accordance with an embodiment of the invention, calibration is performed to determine if printing heads are misaligned relative to each other and/or to scanning and displacement directions and to correct and/or compensate for misalignment. In an embodiment of the invention, calibration is performed responsive to at least one test pattern printed by the RPA. Optionally, the at least one test pattern comprises a plurality of straight lines.

Optionally a determined misalignment is corrected, at least in part, by mechanically realigning the printing head and/or the printing head block in which it is mounted and/or the shuttle that comprises the printing head block. Optionally, misalignment is compensated for, at least in part, by adjusting relative timing of command signals transmitted to at least one printing head to control dispensing material from an orifice or orifices of the at least one printing head.

There is thus provided, in accordance with an embodiment of the invention, a method of producing an object by sequentially printing layers of construction material one on top of the other, the method comprising:

providing the construction material at a first lower temperature;

flowing the construction material through a heated flow path in a flow structure to heat the construction material and delivering the heated construction material to a heated reservoir in a printing head; and

dispensing the heated construction material from the reservoir to build the object layer by layer.

Optionally, the method includes controlling one or more of the flow rate and the temperature of the flow structure to provide a desired temperature of construction material to the reservoir.

In an embodiment of the invention, the temperature and length of the flow structure is high enough so that the temperature of the construction material leaving the reservoir remains substantially constant up to a flow rate of at least 5 gm/sec. Optionally, the temperature of the construction material leaving the reservoir remains substantially constant up to a flow rate of at least 5 gm/sec.

Optionally, the method providing a controller that controls the temperature of the flow structure such that the temperature of the flow structure changes with flow rate to assure the substantial constancy of the temperature of construction material leaving the reservoir.

Optionally, the method forming the flow path as a channel in a heat sink heated by a heater. Optionally, the at least one channel is spiral shaped.

In an embodiment of the invention, the flow path is provided as a meandering path at least a portion of which is heated.

In an embodiment of the invention, the flow path is located inside the reservoir. Optionally, the heating unit of the flow path is mounted to the reservoir. Optionally the heating units of the flow path and of the reservoir are the same unit.

There is further provided, in accordance with an embodiment of the invention, apparatus for producing an object by sequentially printing thin layers of a construction material one on top of the other in a stacking direction, the apparatus comprising:

at least one printing head arranged for relative motion with respect to a surface on which the object is to be constructed and having orifices from which the construction material is dispensed to print the layers;

a controller having a plurality of selectable operation modes;

an interface configured to receive input indicating a selected operation mode and transmit data indicating the selection to the controller; wherein

the controller controls the relative motion and/or the operation of the at least one printing head and/or the layer thickness responsive to the selected operation mode.

Optionally, the production modes comprise at least two of draft, standard and high quality production modes.

Optionally the controller sets at least one production parameter that affects production to satisfy a specification of the selected production mode. Optionally, the at least one production parameter comprises at least one of: a rate of depositing construction material; scanning velocity; UV power for curing construction material; flow rate of air for cooling deposited construction material; construction layer thickness.

There is further provided, in accordance with an embodiment of the invention, a method for producing an object by sequentially printing thin layers of construction material the layers being printed one on top of the other in a stacking direction on a surface of a construction platform, the method comprising:

adding support construction for supporting down facing facets of the object;

orienting the object in respect to the construction platform in a way that the volume of supporting structure is minimum, and

printing the object on the platform so that it is oriented in the determined build configuration.

In an embodiment of the invention, the orientation of minimum support is approximated by the orientation of lowest center of mass of the object in respect to the construction platform

Optionally, orientation of minimum support is approximated by:

orienting the object on the platform at a first orientation a;

rotating the object about an X axis by + and −90° and denoting those orientations as orientations b and c respectively;

rotating the object from orientation a about a Y axis by + and −90° and denoting those orientations as orientations d and e respectively;

rotating the object from orientation a about Y axis+180° and denoting that orientation as orientation f;

computing the volume of supporting structure for each of orientations a to f;

determining the orientation for placement of the object on the platform as one of orientations a through f requiring minimum support.

There is further provided, in accordance with an embodiment of the invention, a method for producing an object by sequentially printing thin layers of build material, the layers being printed one on top of the other in a stacking direction on a surface of a construction platform, the method comprising:

determining a plurality of surface vectors each of which is perpendicular to a surface region of the object;

defining groups of surface vectors for which an angle between any two vectors in the group is less than a predetermined maximum angle;

defining for each group of surface vectors a group vector having a magnitude equal to a sum of the absolute values of the surface vectors in the group and a direction substantially parallel to at least one of the surface vectors;

determining a production orientation of the object responsive to the group vectors; and

printing the object on the platform so that it is oriented in the determined production orientation.

Optionally, the predetermined maximum angle is less than or equal to about 1° or about 5°.

In an embodiment of the invention, printing comprises depositing construction material in a first pass parallel to a scanning direction and, as required, in an additional pass parallel to the first pass and displaced therefrom along a displacement direction.

In an embodiment of the invention, determining the production orientation comprises orienting the object so that a maximum group vector is parallel to one of the three directions: scanning (X), displacement (Y), and stacking (Z). Optionally, the method includes orienting the object so that a next largest vector is parallel to one of the rest of X, Y, Z directions.

There is further provided, in accordance with an embodiment of the invention a method for producing an object by sequentially printing thin layers of build material, the layers being printed one on top of the other in a stacking direction on a surface of a construction platform, the method comprising determining a production orientation for the object for which a rectangular parallelepiped having a volume that just contains the object and for which each face of the parallelepiped is perpendicular to one of the stacking, scanning and displacement directions, has a minimum volume.

In an embodiment of the invention, the method includes:

determining a coordinate system fixed to the object and having axes parallel to the stacking, scanning and displacement directions; and

orienting the object in a plurality of different orientations for which each axis is parallel to one of the stacking, scanning and displacement directions.

Optionally, building the objects includes adding supporting structure, and determining for each of the plurality of orientations an amount of support material required to produce the object in the orientation. Optionally, the method includes determining the production orientation to be that orientation of the plurality of orientations, for which support material is a minimum.

There is further provided, in accordance with an embodiment of the invention, a method of simultaneously producing a plurality of objects by sequentially printing thin layers of construction material one on top of the other in a stacking direction Z on a surface of a construction platform, the method comprising:

determining a build configuration for producing the objects which defines a position and orientation of each of the objects on the platform; and

producing the objects by printing layers of construction material, each layer being printed in a series of scans along a scanning direction and being mutually displaced in a direction Y;

wherein at least two said scan series have different positions of the scans in the Y direction responsive to the layer Y geometry.

Optionally, at least three layers are produced using scan series having different positions of scans in the Y direction.

Optionally, the method includes determining a position for an object such that the object's projection on the Y-Z plane is included in the sum of the projections of previously placed objects on the Y-Z plane. Optionally, the method includes determining a position for an object comprising:

determining the projection on the Y-Z plane of the object;

ordering the objects responsive to the dimensions of their Y-Z projections.

Optionally, the method includes determining a position for an object, such that the object's projection on the Y-Z plane includes the sum of the projections of previously placed objects on the Y-Z plane.

There is further provided, in accordance with an embodiment of the invention, a method of calibrating a rapid production apparatus comprising a printing head block mounted with a plurality of printing heads, each having an array of orifices equally spaced along a respective printing head axis, from which orifices construction material is deposited and wherein the arrays are parallel to each other and construction material is printed during motion of the block along a scanning x-direction, the method comprising:

first printing at least one dot of material from at least one orifice of one of the printing heads;

then printing a second at least one dot of material from an orifice of a same or different printing head;

determining a distance between the two at least one dots;

adjusting or calibrating the apparatus responsive to the distance.

Optionally, the distance is less than 5 mm.

Optionally, the dots are printed on a transparent substrate.

Optionally, the two heads are different from each other, the distance is measured along X direction, and the distance is used to calibrate the jetting X distance between said heads.

Optionally, the distance is measured along the X direction, and the distance is used to aligning the head's block so that the heads are substantially parallel to Y axis.

In an embodiment of the invention the two heads are the same head, where the first at least one dot is jetted by one of the lower nozzles of the head and the second at least one dot is jetted by one of the upper nozzles of the head, where between the first and second jetting of the two at least one dots the block is moved along the indexing Y direction. Optionally, the distance is measured along Y direction, and the distance is used to calibrate Y movement.

In an embodiment of the invention, the first at least one dot is jetted by one head and the second at least one dot is jetted by a second head, where between the first and second jetting of the two at least one dots the block is moved along the scanning X direction, where said distance is measured along Y direction, and the distance is used to aligning the head's block so that the heads are substantially perpendicular to X axis.

There is further provided, in accordance with an embodiment of the invention, a method of removing an object produced by the layer wise laying down of construction material on a construction platform, the construction material being laid down on a thin base of material, the method comprising:

providing a shovel having a flat lifting surface at least as wide as an extent of the object along the base;

sliding the flat surface under the object, while keeping the flat surface parallel to the construction platform; and

lifting the object from the construction platform.

Optionally, at least a portion of the base is lifted together with the object.

Optionally, the flat surface is less than 1 mm thick.

Optionally, the shovel is formed with stiffening edges.

Optionally, the flat surface is formed with a feathered leading edge. Optionally, the feathered leading edge is composed of one single slope from the upper surface of said flat surface to the lower surface of the flat surface.

There is further provided, in accordance with an embodiment of the invention, a method of simultaneously producing a plurality of objects by sequentially printing thin layers of construction material one on top of the other in a stacking direction Z on a surface of a construction platform, the method comprising:

determining a build configuration for producing the objects which defines a position and orientation of each of the objects on the platform; and

producing the objects by printing the construction material in a first pass parallel to a scanning direction X and, as required, in an additional pass parallel to the first pass displaced therefrom along a displacement direction Y so that each object is in the position and orientation of the build configuration;

wherein the Y coordinate of at least one pass on one layer is different from that of any of the passes on a lower layer.

Optionally, objects having a requirement for printing upper layers are so aligned that a minimum number of passes is required to print the upper layers.

