NL2037202B1

NL2037202B1 - Method of inkjet printing a multi-material structure

Info

Publication number: NL2037202B1
Application number: NL2037202A
Authority: NL
Inventors: H W Lamers Norbert
Original assignee: Canon Production Printing Holding Bv
Priority date: 2024-03-08
Filing date: 2024-03-08
Publication date: 2025-09-22
Also published as: DE102025107259A1

Abstract

100303NL01 A versatile method for the three dimensional inkjet printing of a variety of multi-material structures (90, 90’) is provided. The method comprises the steps of: a) determining a first number (N) of printheads (11-14) and fixation units (21-24) required for printing a predetermined first multi-material structure (90, 90’); a) determining a first, relative positioning of the first number (N) of printheads (11-14) and the fixation units (21-24) for printing and curing the first multi-material structure (90, 90’); b) mounting the first number (N) of printheads (11-14) and fixation units (21-24) in the respective, first positions on a common carrier (50); c) printing the first multi-material structure (90, 90’) with the first number (N) of printheads (11-14) and fixation units (21-24) mounted in the respective, first positions; d) adjusting the first positions and/or the first number (N) of printheads (11-14) and fixation units (21-24) on the common carrier (50) for printing a second multi-material structure (90, 90’) different from the first, such that the relative positioning of the second number of printheads (11-14) and fixation units (21-24) on the common carrier (50) is different from during printing the first structure (90, 90’). Fig. 8

Description

100303NL01 1

Method of inkjet printing a multi-material structure

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to a method of three dimensionally inkjet printing a multi-material structure and a printing assembly for performing such a method. 2. Description of Background Art

It is known to apply inkjet printing to form three dimensional multi-material objects, such as for example dental protheses. Such objects generally comprise a wide range of shapes and materials, wherein each object requires different layers of material to be deposited onto one another in different orders, different amounts, and/or different shapes. The different materials may have different properties, such as color, hardness, chemical resistance, etc. NL 2021957 B1 discloses a printing assembly with a cyclic conveyor for the productive printing of dental protheses.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a printing assembly and/or a method that can easily and quickly accommodate to the different requirements for printing a variety of three-dimensional multi-material objects, specifically dental protheses.

In accordance with the present invention, a method for the three dimensional inkjet printing of a multi-material structure according to claim 1 and a printing assembly according to claim 10 are provided.

The method comprises the steps of: a) providing at least one printhead and at least one fixation unit on a common carrier in a first configuration, which common carrier comprises a receiving slot assembly defining a plurality of mounting positions, wherein each printhead and each fixation unit comprises a mounting part, which can be fittingly mounted into any of the mounting positions on the common carrier; b) activating at least one printhead and at least one fixation unit in the first configuration for printing and curing a first multi-material structure; c) adjusting the at least one printhead and the at least one fixation unit to a second configuration, different from the first configuration, for printing and curing a second multi- material structure.

100303NL01 2

The common carrier comprises a number of mounting positions greater than two, so that multiple printheads and/or multiple fixation units can be mounted together on the common carrier. Different configurations of printheads and fixation unit can be activated per print job dependent on the requirements of the respective multi-material structure to be printed in said print job. This allows for quick and optimization of the printhead and fixation unit assembly for different print jobs. Thereby, the object of the present invention has been achieved.

More specific optional features of the invention are indicated in the dependent claims.

In an embodiment, the method further comprises the step of selecting activating the at least one printhead and the at least one fixation unit based on print job information for each first multi-material structure. The selected printheads(s) and fixation unit(s) are activated when printing the respective structure. The printhead(s) and fixation unit(s) are selected, so that the intended structure can be printed using these printhead(s) and fixation unit(s). The print job information may define the materials required for forming the multi-material structure, the order in which said materials are to be deposited, and/or required fixation intensities and/or times for each of said materials, etc.

In an embodiment, the step of adjusting comprises at least one of the following steps: - changing at least one printhead and/or at least one fixation unit to a different mounting position with respect to the first configuration; - changing a total number of printheads and/or fixation units mounted on the common carrier with respect to the first configuration; and - controlling a different total number of printheads and/or fixation units mounted on the common carrier with respect to the first configuration.

The universal mounting parts allow for quickly adding or removing a printhead or fixation unit to a mounting position. Thus, the relative positions of printheads and/or or fixation units on the common carrier can be quickly changed. In addition, printheads and/or fixation units can be added or removed. Also, one or more printheads and/or fixation units mounted on the common carrier may not activated during a print job to reduce the number of active printheads and/or fixation units with respect to a previous or upcoming print job.

In an embodiment, the method further comprises the steps of: - determining the first configuration, which comprises the steps of:

100303NL01 3 -) determining a first number of printheads and fixation units required for printing a predetermined first multi-material structure; -) determining a first, relative positioning of the first number of printheads and the fixation units for printing and curing the first multi-material structure; -} mounting the number of printheads and fixation units in the respective, first positions on a common carrier, -) printing the first multi-material structure with the number of printheads and fixation units mounted in the respective, first positions; -) adjusting the first positions and/or the first number of printheads and fixation units on the common carrier to the second configuration for printing a second multi-material structure different from the first, such that the relative positioning of the second number of printheads and fixation units on the common carrier is different from during printing the first structure.

Each printhead is configured for jetting droplets of a certain liquid material and each fixation unit is configured is at least partially hardening or solidifying liquid material into a solid state. Fixation units preferably comprise an emitter for applying heat, cold, radiation, or other forms of energy to change the phase of the jetted material. The same common carrier is applied for mounting the printheads and fixation units throughout all print jobs. The print job determines the number of printheads and fixation units to be mounted on the common carrier in the respective configuration. For example, the number of printheads may be equal to the number of different materials required to print a respective multi-material structure, and the number of fixation units may be equal to the number of printheads, so that each material is cured before a different material is printed over it. The different materials may be different colors and/or have different mechanical, physical, and/or chemical properties. For every print job, the corresponding number of printheads and fixation units is mounted onto the common carrier, thus allowing for printing a wide variety of multi-material, three-dimensional objects with a single printing assembly. The single printing assembly can thus be easily and rapidly adjusted for determining an (optimal) working range for printing an object, when researching the printing conditions for a new type of object.

In an embodiment, the common carrier defines a plurality of mounting positions, wherein all printheads and fixation units comprise a mounting part fitted to be received into any of the mounting positions. The mounting parts allow each printhead and each fixation unit to be positioned in any of the mounting positions. This allows an operator to easily

100303NL01 4 move or swap printheads and/or fixation units into or out of the common carrier. Not only the number of fixation units and printheads can be adjusted in this manner, but also a spacing between printheads and fixation units. Thereby, an operator may adjust the jetting intensity, curing intensity, and a setting for cooling or heating period between printheads and/or fixation units. Printheads and fixation units may be easily exchanged and/or swapped. It will be appreciated that certain printheads and fixation units may be present in the printing assembly in a disabled state as well, if that is compatible with the current print job. Thus, the printing assembly can be easily adjusted to accommodate to any print job.

In an embodiment, all printheads and fixation units comprise similar mounting parts and all mounting positions comprise similar alignment means arranged to fittingly receive any of the mounting parts, such that all mounted printheads or fixation units are aligned with one another. Every mounting part is fitting to all alignment means at all mounting positions. For example, a mounting position may be defined by a receiving slot with alignment means for receiving corresponding portions of a mounting part, so that the mounting part is aligned with respect to the common carrier. The alignment means provide a common or similar alignment for all mounting positions.

In an embodiment, the number of printheads and fixation units is equal or proportional to a number of different materials specified for forming the multi-material structure. Based upon print job information for a multi-material structure, a number of different materials for forming the respective multi-material structure is determined. The number of printheads matches the number of different materials, wherein optionally multiple printheads may be provided for jetting the same material, for example in case large guantities of said material are required. Preferably, every printhead is configured to jet a different material. The number of fixation units is preferably at least equal to the number of different materials, so that each material may be cured before the multi-material structure reaches the next printhead for jetting a different material. This allows for productive printing.

In an embodiment, the number of printheads and/or fixation units varies per printing and curing process. A first multi-material structure may be printed with a first number of different materials, while a second multi-material structure may be printed with a second number of different materials, which second number is different from the first number. In

100303NL01 one print job, the number of printheads and fixation units is different from in another print job to accommodate to the different specifications of each print job, for example a number of different materials, curing times, etc. In another embodiment, the number of printheads and fixation units is equal or proportional to a number of different materials 5 specified for forming the respective multi-material structure. The number of materials may change per print job and the printing assembly can be easily adjusted to change to the corresponding number of printheads and fixation units. The number of printheads and/or fixation units preferably varies per one or more multi-material protheses. The number of materials and thus the number of printheads and/or fixation units for the first multi-material structure is then different from the second multi-material structure.

In an embodiment, each printhead has a row of nozzles extending in a first direction when mounted on the common carrier and the plurality of mounting positions extend in a row on the common carrier in a second direction perpendicular to the first direction.

The row of nozzles determines a working range in the first direction, which working range is preferably at least the same for all printheads and fixation units. The row of mounting positions extends in a second direction perpendicular to the first direction, so that the multi-material structure may be moved with respect to the common carrier in the second direction, such that it consecutively passes printheads and fixation units.

In an embodiment, a fixation unit is positioned between every two adjacent printheads configured for jetting a different material in the second direction. Preferably every printhead or group of printheads jetting the same material is provided with at least one fixation unit. A fixation unit cures a first layer of a first material before the multi-material structure is positioned under a printhead for jetting second material on the first layer.

The second material may be the same or different from the first material in terms of color or chemical composition. One or more final fixation units may be provided at an end of the row of mounting positions to cure the final layer.

Ina further aspect, the present invention relates to a printing assembly for the three dimensional inkjet printing of a multi-material structure, the printing assembly comprising: - a common carrier comprising a slot assembly, which carrier is positionable and movable with respect to a print substrate support; - a plurality of separate printheads for jetting a radiation curable fluid onto the print

100303NL01 6 substrate support; - a plurality of separate fixation units for irradiating the curable fluid on the print substrate support, so that the fluid solidifies, wherein: - the printheads and the fixation units each comprise a mounting part, wherein each mounting part is configured to be fittingly received into the receiving slot assembly; and - a controller configured for activating at least one printhead and at least one fixation unit mounted on the common carrier in different configurations for printing and curing different multi-material structures.

The controller preferably includes an electronic circuit for activating a printhead and a fixation unit mounted on the common carrier in each available position of the printhead and a fixation unit. In every configuration, the controller can activate a printhead or fixation in accordance with the requirements for the present print job. The electronic circuit allows the controller to activate a printhead or fixation unit in any available position on the common carrier, regardless of the total number of printheads or fixation units. The printheads and fixation units are electrically connectable to the controller in any position. The controller may further selectively activate a subset of the mounted printheads and/or fixation units, leaving the non-selected devices in an idle state, while the selected device are active in forming the multi-material structure.

The common carrier has a slot assembly which defines a plurality of mounting positions extending in a row in a second direction. A printhead or a fixation unit can be mounted in each mounting position, such that a width or working range of the respective printhead or fixation unit extends in a first direction perpendicular to the second direction. The working range is the widest dimension of the working area of a printhead or fixation unit. The mounting parts of all printheads and fixation unit have been similarly fitted, so that these fit onto or into any of the mounting positions. This allows the positions and numbers of the printheads and fixation units to be varied to conform to the requirements of a specific print job. Thus, a wide variety of multi-material structures may be printed using a single printing assembly.

In an embodiment, the printing assembly is provided with a locking mechanism movable into a closed position for simultaneously securing the respective printheads and fixation units in their receiving slots. By releasing the locking mechanism, the fixation units and printheads are freed, so that these can be easily adjusted in position and/or number. By closing the locking mechanism all mounted printheads and fixation units are secured in

100303NL01 7 place for a print job.

In an embodiment, the printheads and the fixation units have a similar working range in a first direction defined by respective a width of a row of nozzles or one or more lamps, and wherein the receiving slots are positioned in a row extending in a second direction perpendicular to the first direction, when the printheads and fixation units are received in the common carrier. The widest operational width of the fixation units and printheads is perpendicular to the direction of relative movement between the common carrier and the multi-material structures.

In an embodiment, the printing assembly further comprises a transport mechanism for moving the common carrier with respect to the print substrate support in the second direction. The transport mechanism moves the print substrate support and/or the common carrier, so that the multi-material structure passes the different printheads and fixation units. This movement may be in a single pass, but a multi-material structure may also be reciprocally moved between a specific printhead and fixation unit before moving to a different printhead for jetting a different material.

In an embodiment, the locking mechanism is arranged to facilitate easy loading and unloading of the printheads and fixation units into and out of the printing assembly and securing these in place on the printing assembly. Any suitable locking mechanism may be applied, such as mechanical or magnetic lock. Preferably the locking mechanism is arranged to simultaneously lock all mounted printheads and fixation units on the printing assembly simultaneously. For example, the locking mechanism may comprise a lever connected to a locking beam extending in the second direction, so that by pivoting the lever the locking beam moves to a locking position, wherein all printheads and lamps on the common carrier are secured thereto. A central lever may be moved by hand or an actuator to move the locking to secure or release all mounted printheads or fixation units simultaneously.

In an embodiment, the printing assembly comprises heigh adjustment means for adjusting the height of the printheads and/or fixation units in a jetting direction of the printheads. The height of the common carrier can be adjusted by providing it with a translating mechanism, such as a slider or a rack and pinion system. The height adjustment may be manual or motorized.

100303NL01 8

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

Fig. 1 is a block diagram illustrating the step of the method of printing multi-material structures;

Fig. 2 is a schematic, cross-sectional view of a first embodiment of a dental prothesis;

Fig. 3 is a schematic, side view of a first configuration of a printing assembly for printing the dental prothesis in Fig. 2;

Fig. 4 is a schematic, perspective of a first configuration of the printing assembly in Fig. 3

Fig. 5 is a schematic, cross-sectional view of a second embodiment of a dental prothesis;

Fig. 6 is a schematic, side view of a second configuration of the printing assembly for printing the dental prothesis in Fig. 5;

Fig. 7 is a schematic, perspective of a third configuration of the printing assembly;

Fig. 8 is a schematic, perspective of a fourth configuration of the printing assembly;

Fig. 9 is a schematic, perspective of a fifth configuration of the printing assembly;

Fig. 10is a schematic, side view of the first configuration of the printing assembly for printing the dental prothesis in Fig. 2; and

Fig. 11is a schematic, perspective of a sixth configuration of the printing assembly for printing the dental prothesis in Fig. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views.

100303NL01 9

Fig. 1 illustrates the step of a method of printing multi-material structures on a printing assembly 1 as shown in Figs.3, 4, 6- 11. In step i, a first print job for a dental prothesis as shown in Fig. 2 is specified. The print job is based on a three-dimensional structure for a dental prothesis 90 which preferably comprises a plurality of different materials to form the different layers 91-93 of the prothesis 90.

In step ii, a required number N of printheads 11-14 and a required number N’ of curing lamps 21-24 is determined from the print job specification. For example the number N of required printheads 11-14 is equal or proportional to the number of different materials applied in the respective dental prothesis 90. For example, the dental prothesis 90 comprises three different materials, resulting in at least three different printheads 11-14.

It will be appreciated that a single printhead 11-14 may be configured to jet multiple materials, for example by having two rows of nozzle, each connected to a different material reservoir. Similarly, multiple, individual printheads 11-14 may be applied to jet the same material to accelerate the deposition, for example for the bulkier parts of the dental prothesis 90. A number N’ of curing lamps 21-24 required for curing the jetted marking material is proportional or equal to the number of printheads 11-14. For each different type of marking material at least one curing lamp 21-24 is required for curing the liquid material into a solid, printed layer. In this example in Fig. 1, the number N' is taken equal to N, but in another embodiment the numbers N, N’ may be different.

Additionally, a relative positioning of the printheads 11-14 and curing lamps 21-24 is determined, resulting in a first configuration of the printing assembly 1. The positioning may be in the form of an order wherein the printheads 11-14 and curing lamps 21-24 are positioned in the second direction D2 wherein the print substrate support 41 moves relative to the printheads 11-14. The positioning may further include distance information determining a spacing between printheads 11-14 and curing lamps 21-24.

Preferably, the one or more printheads 11-14 positioned together for jetting the same material are followed in the second direction D2 by at least one curing lamp 21-24 for curing said material before a further printhead 11-14 for jetting a further material is reached. The further material may be the same material or a different one, in terms of color or chemical properties. This further printhead 11-14 is then followed by its respective curing lamp 21-24 before another printhead 11-14 for jetting another, different material is reached. Etc. In the second direction D2 a printhead 11-14 is positioned upstream and a curing lamp 21-24 on the downstream side, wherein

100303NL01 10 between these, printheads 11-14 and curing lamps 21-24 substantially alternate to consequently jet and cure layers of different materials. In correspondence with the to be jetted materials, printheads 11-14 and curing lamps 21-24 are selected.

In step iii, the selected printheads 11-14 and the curing lamps 21-24 are mounted onto a common carrier 50 in the order and/or positions determined in step ii. The common carrier 50 is arranged to hold a plurality of both printheads 11-14 and curing lamps 21- 24 in a variety of different relative positions, for example as defined by a row of receiving slots 60 extending in the second direction D2. The printheads 11-14 and the curing lamps 21-24 are positioned corresponding to the positioning determined in step ii, either manually by an operator or by an actuator, such as a motor or robot arm. After positioning, in step iv, the printheads 11-14 and curing lamps 21-24 are secured into said position, such these are fixed with respect to the carrier 50. Figs. 3,4 illustrate a first number and positioning of printheads 11-14 and curing lamps 21-24 for a first dental prothesis 90 in Fig. 2, while Fig. 6 illustrates a second number and a different positioning of printheads 11-13 and curing lamps 21-23 for a second dental prothesis 90’ in Fig. 5. The mounted printheads 11-13 and curing lamps 21-23 are connected to a controller.

In step v, the print job is started and the print substrate support 41 is moved with respect to the carrier 50, so that a print position for the dental prothesis 90 first passes the upstream printhead or printheads 11, 12. In correspondence with the print job, the controller controls the printheads 11-13 and curing lamps 21-23. In step vi, the printhead 11-14 jets its respective material onto the print position 42 to form a part of the respective layer 91-93 of the dental prothesis. The jetted material is then cured by exposure to radiation from the curing lamp 21, 22 directly downstream of the upstream printhead(s) 11, 12 in step vii. The radiation may be in the form of e.g. UV light or heat.

The respective layer 91 may be printed in a single pass or the print position may be moved back and forward in the second direction D2 to alternatingly jet and cure layer segments of the same material until the layer 91 has been completed.

The print position 42 is then moved to the next printhead 13 for jetting a different material on top of the first layer 91. Steps vi and vii are then repeated to jet and cure this layer 92. Step vi and vii are repeated an N number of times to complete the dental

100303NL01 11 prothesis 90. It will be appreciated that the number N is preferably equal the number of different materials required for printing the dental prothesis 90.

Steps iv and vii are then repeated for each different layer 91-93 in the dental prothesis 90, wherein the prothesis 90 is moved between sets of printheads 11-14 and curing lamps 21-24 when a layer of material is completed. Upon completion of the print job step i is executed again to determine a new number and relative positions for the printheads 11-14 and curing lamps 21-24 for another dental prothesis 90, wherein this new number and relative positions are different from those previously applied. As shown in Fig. 6, a different number of printheads 11-13 and curing lamps 21-23 is required for this printing the dental prothesis 90’ in Fig 5. Also, the relative positioning of the printheads 11-13 and curing lamps 21-23 in this second configuration is different. As well be explained below, the printing assembly 1 can be easily adjusted to different numbers and positioning of printheads 11-14 and curing lamps 21-24 due to the configuration of a common carrier 50 upon which the printheads 11-13 and curing lamps 21-23 are mountable.

The printheads 11-14 and the curing lamps 21-24 are both provided with mounting parts that are matching with the receiving slots 60 on the carrier 50, so that a printhead and/or a curing lamp 21-24 can be mounted at any position defined by the receiving slot(s) 60.

In the example in Fig. 7 and 8 multiple, identical slots 60 are provided on the carrier 50, and the printheads 11-14 and the curing lamps 21-24 are provided with similar or identical mounting parts, so that these all fit into any of the receiving slots 60. Fig. 9 illustrates an embodiment, wherein the carrier 50° comprises a receiving slot 60’, 60”, which allows for stepless positioning of the printheads 11-14 and curing lamps 21-24 by means of a guide rail like alignment surface 62’. This allow for rapidly adding and/or removing printheads 11-14 and/or curing lamps 21-24 from the carrier 50, as well as for changing their relative positions. The common carrier 50 will be discussed in detail with reference to configurations of the printing assembly 1, 1’ for respectively printing the dental protheses 90, 90’ in Fig. 2 and 5.

Fig. 2 illustrates a first embodiment of a multi-material dental prothesis 90. The dental prothesis 90 comprises several different material deposited over one another. The inner body 91 may for example be a structural bulk material, which is non-transparent. Over the inner body 91, two layers 92, 93 are deposited, which are both at least partially

100303NL01 12 transparent to create a realistic appearance of a tooth. The transparency and/or color of the outer layer 93 preferably differs from that of the middle layer 92. Also, the outer layer 93 may be provided with different (chemical and/or mechanical) properties than the other layers 91, 92. To mimic the appearance of the respective tooth to be replaced or fixed by the dental prothesis 90, the form and composition of each dental prothesis 90 is preferably different.

Custom dental protheses 90 like in Fig. 2 can be productively manufactured by means of a dental prothesis printing assembly 1, as shown in Figs. 3 and 4. The printing assembly 1 comprises a plurality of printheads 10, each configured to jet at least one type of marking material for forming at least one of the layers 91-93. The printheads 10 jet the marking material in liquid form onto a print substrate support 41. A plurality of curing lamps 20 is provided to irradiate the jetted marking material so that it solidifies.

The marking material is preferably a UV curable ink, comprising a photo-initiator that upon exposure to UV radiation triggers a phase change in the liquid marking material.

Fig. 4 illustrates that each printhead 11-14 has at least one row of nozzles 15, 16 extending in the first direction D1. The width of the nozzle rows 15, 16 defines the working range WR of the printing assembly 1 in the first direction D1. In Fig. 3 all printheads 11-14 have the same working range WR. Similarly, all curing lamps 21-24 have a similar working range WR. Where the working WR of the printheads is defined by the row of nozzles, the working range of a fixation unit may be determined by a length or width of its lamp, or row of lamps 25..

The print substrate support 41 defines one more print positions 42, which may be moved in the second direction D2 with respect to the printheads 11-14 and the curing lamps 21-24. Multiple print positions 42 may be provided besides one another in the first direction D1 to allow for the simultaneous printing of multiple dental protheses 90. A transport mechanism 41 comprising a drive 42 is provided for moving the print positions 42. In the example in Fig. 3, the transport mechanism 41 comprises an endless belt, but any other suitable transport mechanism may be applied as well. It will further be appreciated that in another embodiment, the print substrate support 41 may be stationary and the printheads 11-14 and curing lamps 21-24 are moved with respect to the print substrate support 41. The dental protheses 90 may be printed in a single pass,

100303NL01 13 but may also be formed by moving a single prothesis 90 back and forth in the second direction D2 along one or more printheads 11-14.

In the second direction D2, the printheads 11-14 are provided with curing lamps 21-24 downstream of the respective printheads 11-14, so that a first type of marking material may be cured before applying a second type of marking material different from the first.

In the second direction D2, every printhead 11-14 is provided with a respective curing lamp 21-24, which in most cases is upstream of any downstream printhead 11-14 for jetting a different marking material. Each curing lamp 21-24 comprises one or more UV lamps 25 which span the width of the working range WR. It will be appreciated that other types of fixation units may also be applied, for example heaters, coolers, IR radiators, blowers, dryers, etc. In Figs. 2 and 3, on the upstream side two printheads 11, 12 for jetting the material for the inner body 91 are positioned besides one another, so that the relatively larger volume of the inner body 91 can be rapidly deposited. Two rows of curing lamps 21, 22 are positioned downstream of the two printheads 11, 12 to ensure that sufficient UV radiation is provided to cure the relatively large amount of the first marking material being jetted per unit time. Another printhead 13 for jetting the second marking material for forming the middle layer 92 is positioned downstream of the two curing lamps 21, 22. Since the middle layer 92 requires less marking material than the inner body 91 a single printhead 13 followed by a single curing lamp 23 suffices.

The curing lamp 23 cures the second marking material of the middle layer 92 before the dental prothesis 90 arrives at the final printhead 13. The final printhead 14 jets a third type of marking material different from the first and the second to form the outer layer 93. Consequently the outer layer 93 is cured by the respective curing lamp 24 downstream of the printhead 14.

In the embodiment in Fig. 6 a different configuration of the printing assembly 1’ is shown for printing another embodiment of a dental prothesis 90’ shown in Fig. 5. The relative order and positions of the printheads 11-13 and the curing lamps 21-23 are different as compared to Figs. 2 and 3. The printheads 11-14 and the curing lamps 21-24 in Figs. 3, 4, and 6 are mounted on the same common carrier {50 in Fig. 7 and following), which carrier 50 allows for quick and easy variations in the positions of the printheads 11-14 and curing lamps 21-24 between print jobs. The rapid swapping of printheads 11-14 and curing lamps 21-24 does not only allow for rapidly readying the printing assembly 1’ for anew print job, but it further aids in quickly determining or optimizing a print process for

100303NL01 14 forming a new type of multi-material structure. When researching how to print a new multi-material structure, printheads 11-14 and curing lamps 21-24 can be quickly adjusted in correspondence to observations made during research.

The dental prothesis in Fig. 5 comprises two layers 91’, 92’, wherein the inner body 971’ makes up the bulk of the total volume. The outer layer 92’ is formed of a different material, for example a protective layer of relatively high hardness. To print the inner body 91’ two printheads 11, 12 are provided. Both printheads 11, 12 are configured to jet the same marking material, whereas the third printhead 13 jets a different material.

Dual curing lamps 21-22 are positioned directly downstream of the printheads 11, 12 to rapidly cure the inner body 91°. The third printhead 13 is spaced apart some distance from the dual curing lamps 21, 22 to allow the inner body 81’ to cool down or heat up, so that the inner body 91’ has the optimal temperature for applying the outer layer 92’. The outer layer 92’ is then printed by the third printhead 23 and cured by the third curing lamp 23.

Fig. 7 illustrates another configuration of a printhead assembly 1”. Fig. 7 shows the common carrier 50 for mounting the printheads 11 and the curing lamps 21 in different positions. The carrier 50 is formed as a matrix plate, which defines a plurality of receiving slots 60. The receiving slots 60 during printing extend in a row in the second direction D2. Each insertion slot 60 comprises an opening 61 formed as a through-hole in the matrix plate, so that the mounted printhead 11 or curing lamp 21 freely faces the print substrate support 41. The width of the opening 61 corresponds to the working range WR. Each receiving slot 60 further comprises alignment means 62 on one or more sides of the opening 61. The alignment means 62 ensure that when mounted the printheads 11 and/or curing lamps 21 have the same or a similar orientation. The alignments means 62 are preferably on the sides or edges of opening in the first direction D1.

Inthe example in Fig. 7, the alignment means 62 comprise at least one spherical recess in the matrix plate, preferably in combination with a V-groove, as described in

US 1008990149 B2. Each printhead 11 or curing lamp 21 is provided with a corresponding mounting part in the form of a spherical ball dimensioned to at least partially fit into said recesses. In Fig. 7 pairs of recesses are positioned at the same positions in the second direction D2. When the balls in a printhead 11 or curing lamp 21

100303NL01 15 are inserted into the recesses, the printhead 11 or curing lamp 21 is aligned to the first direction D1. The working ranges WR of the printhead 11 and/or curing lamps 21 are thereby aligned with one another.

The printhead in Fig. 7 is provided with an inlet 15 for receiving marking material, such that it may be jetted from the nozzles of the printhead 15. The marking material may be supplied to the inlet 15 in liquid or solid form. In the latter case, the printhead 11 comprises means for liquifying the marking material, such as a heater. Additionally control electronics 18 are provided on the printhead 11 to process the signal required for jetting droplets of marking material from the nozzles in correspondence to the print job.

The curing lamps 21 each comprises a LED lamp array 25 for emitting UV light. The curing lamp 25 is provided with cooling and/or heating channels 25 to maintain the curing lamp 21 at its operational temperature. The wavelength and/or intensity of the curing lamps 21 may be matched to the type of marking material.

In Fig. 7, all receiving slots 60 are configured identically, so that the alignment means 62 are the same for all receiving slots 60 and have the same respective positions in the first direction D1 as well. The mounting parts on the printheads 11 and the curing lamps 21 are also configured similarly, so that each printhead 11 and each curing lamp 21 fits onto any of the receiving slots 60. Additionally, a suitable locking mechanism is provided on the common carrier 50. The locking mechanism comprises a securing beam (70 in

Fig. 8) which extends in the second direction D2 over all receiving slots 60. The locking mechanism is movable between an open and a closed position by means of a single lever. The lever may actuated by an operator or by an actuator, so that with a single movement all mounted printheads 11 and curing lamps 21 are secured onto matrix plate of the carrier 50. In the open position, the securing beam 70 is away from the receiving slots 60 to allow for the easy placing or removing of printheads 11 or curing lamps 21. In the closed position, the securing beam 70 engages a locking portion of each mounted printheads 11 or curing lamps 21, so that these are urged towards the matrix plate. The securing beam 70 is sufficiently rigid and dimensioned such that empty insertion slots 60 do not substantially affect the securing function of the locking mechanism. This allows an operator to easily change the configuration of the printing assembly 1°”.

Fig. 9 illustrates another configuration of a printhead assembly 1””, which includes another embodiment of the carrier 50. The carrier 50 is configured to allow for stepless

100303NL01 16 adjustment of the positions of the printheads 11 and/or the curing lamps 21. The carrier 50’ comprises a reference receiving slot 60 configured as the receiving slots 60 in Figs. 6-8. Additionally the matrix plate is provided with stepless positioning receiving slots 60, 60”. The receiving slots 60’, 60” comprise an opening 61’, 61” and stepless positioning alignment means 62’, 62". In Fig. 9, the stepless positioning alignment means 62’, 82” comprise a guidance element, such as a flat surface extending continuously in the second direction D2. Such surfaces are positioned on opposite sides of the openings 671, 61". The flat surfaces act as guide rail on either side of the opening 61’, 61”. The printheads 11 and curing lamps 21 are provided with mounting parts configured to slidingly fit onto these guide rail, so that when mounted but not locked by the mechanism, the printheads 11 and curing lamps 21 in the receiving slots 60’, 60” may be moved stepless in the second direction D2. When the intended positions have been reached, the locking beam 70 is moved to secure the printheads 11 and curing lamps 21.

As shown in Fig. 8, the printing assembly 1” in Fig. 6 can be easily adjusted to hold more printheads 11, 12 and curing lamps 21, 22 by opening the locking mechanism and adding a printhead 12 and a curing lamp 22 to a respective empty slot 60. The relative positioning between printheads 11, 12 and curing lamps 21, 22 may also be adjusted by including one or more empty receiving slots 60 between e.g. a printhead 12 and its corresponding curing lamp 22. When the printheads 11 and curing lamps 21 have been positioned in their intended positioned, the locking mechanism is actuated, so that the securing beam 70 secures the printheads 11 and curing lamps 21 in said positions.

Thus, the number of curing lamps 21-14, the number of printheads 11-14 and their relative positioning may be easily adjusted to match the requirement of any print job.

Figs. 10 and 11 illustrate a different configuration for printing the different dental protheses 90, 90’ in Fig. 2 and Fig. 5. In Fig. 10, the printing assembly 1 is configured as described for Fig. 3. The controller in Fig. 3 and Fig. 10 controls al the printheads 11- 14 and all the curing lamps 21-24 to respectively jet ink and cure the dental protheses 90 as these pass along the printheads 11-14 and all the curing lamps 21-24. For printing the two-material prothesis 90’, the controller prevents one printhead 13 and one curing lamp 23 from respectively jetting and curing. In consequence, the protheses 90’ pass along this disabled printhead 13 and curing lamp 23 without material being added or cured to the prothesis 90’. The controller may apply a subset of the total number of

100303NL01 17 mounted printheads 11-14 and/or curing lamps 21-24 to form a prothesis 90. 90’. This prevents the need for swapping in one or more printheads 11-14 or curing lamps 21-24 for one or a low number of print jobs.

Although specific embodiments of the invention are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are examples only and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

It will also be appreciated that in this document the terms "comprise", "comprising", "include", "including", "contain", "containing", "have", "having", and any variations thereof, are intended to be understood in an inclusive (i.e. non-exclusive) sense, such that the process, method, device, apparatus or system described herein is not limited to those features or parts or elements or steps recited but may include other elements, features, parts or steps not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "a" and "an" used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms "first", "second", "third", etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects.

The present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

100303NL01 18

EMBODIMENTS

1. A method for the three dimensional inkjet printing of a multi-material structure (90, 90"), comprising the steps of: - providing at least one printhead (11-14) and at least one fixation unit (21-24) on a common carrier (50} in a first configuration, which common carrier (50) comprises a receiving slot assembly defining a plurality of mounting positions, wherein each printhead (11-14) and each fixation unit (21-24) comprises a mounting part, which can be fittingly mounted into any of the mounting positions on the common carrier (50); - activating at least one printhead (11-14) and at least one fixation unit (21-24) in the first configuration for printing and curing a first multi-material structure (90, 90°); - adjusting the at least one printhead (11-14) and the at least one fixation unit (21-24) to a second configuration, different from the first configuration, for printing and curing a second multi-material structure (90, 90’). 2. The method according to claim 1, wherein the step of adjusting comprises at least one of the following steps: - changing at least one printhead (11-14) and/or at least one fixation unit (21-24) to a different mounting position with respect to the first configuration; - changing a total number of printheads (11-14) and/or fixation units (21-24) mounted on the common carrier (50) with respect to the first configuration; and - controlling a different total number of printheads (11-14) and/or fixation units (21-24) mounted on the common carrier (50) with respect to the first configuration. 3. The method according to any of the previous claims, further comprising the step of - determining the first configuration, which comprises the steps of: - determining a first number (N) of printheads (11-14) and fixation units (21-24) required for printing the first multi-material structure (90, 90’); - determining a first, relative positioning of the first number (N) of printheads (11- 14) and the fixation units (21-24) for printing and curing the first multi-material structure (90, 90’); - mounting the first number (N) of printheads (11-14) and fixation units (21-24) in the respective, first positions on the common carrier (50); - printing the first multi-material structure (90, 90°) with the first number (N) of printheads (11-14) and fixation units (21-24) mounted in the respective, first positions;

100303NL01 19 - adjusting the first positions and/or the first number (N) of printheads (11-14) and fixation units (21-24) on the common carrier (50) to the second configuration for printing a second multi-material structure (90, 90°) different from the first, such that the relative positioning of the second number of printheads (11-14) and fixation units (21-24) on the common carrier (50) is different from during printing the first structure (90, 90’) . 4. The method according to claim 3, wherein the common carrier (50) defines a plurality of mounting positions, wherein all printheads (11-14) and fixation units (21-24) comprise a mounting part fitted to be received into any of the mounting positions.

5. The method according to any of the claims 3 and 4, wherein all printheads (11-14) and fixation units (21-24) comprise similar mounting parts and al mounting positions comprise similar alignment means (62) arranged to fittingly receive any of the mounting parts, such that all mounted printhead (11-14) or fixation unit (21-24) are aligned with one another. 6. The method according to any of the claims 3 to 5, wherein the number (N) of printheads (11-14) and fixation units (21-24) is equal or proportional to a number (N) of different materials specified for forming the respective multi-material structure (90, 90").

7. The method according to claim 5, wherein the number (N) of printheads (11-14) and/or fixation units (21-24) varies per one or more multi-material structures (90, 90’). 8. The method according to claim 8, wherein each printhead (11-14) has a row of nozzles (15, 16) extending in a first direction (D1) when mounted on the common carrier (50) and the plurality of mounting positions extend in a row on the common carrier (50) in a second direction (D2) perpendicular to the first direction (D1). 9. The method according to claim 8, wherein a fixation unit (21-24) is positioned between every two adjacent printheads (11-14), wherein one printhead (11-14) is configured for jetting a different material in the second direction(D2) than the other printhead (11-14). 10. A printing assembly (1) for the three dimensional inkjet printing of a multi-material structure (90, 90’), the printing assembly (1) comprising:

100303NL01 20 - a common carrier (50) comprising a receiving slot assembly with at least one receiving slot (60) defining a plurality of mounting positions, which carrier (50) is positionable and movable with respect to a print substrate support (41); - a plurality of separate printheads (11-14) for jetting a radiation curable fluid onto the print substrate support (41); - a plurality of separate fixation units (21-24) for irradiating the curable fluid on the print substrate support (41), so that the fluid solidifies; characterized in that: - the printheads (11-14) and the fixation units (21-24) each comprise a mounting part, wherein each mounting part is configured to be fittingly received into the receiving slot (60) assembly in any of the mounting positions; and - a controller configured for activating at least one printhead (11-14) and at least one fixation unit (21-24) mounted on the common carrier (50) in different configurations for printing and curing different multi-material structures (90, 90°).

11. The printing assembly (1) according to claim 10, wherein the common carrier (50) is provided with a locking mechanism movable into a closed position for simultaneously securing the respective printheads (11-14) and fixation units (21-24) in their at least one receiving slot (60).

12. The printing assembly (1) according to claim 10 or 11, wherein the printheads (11- 14) and the fixation units (21-24) have a similar working range (WR) in a first direction (D1) defined by respective a width of a row of nozzles (15, 16) or one or more lamps (25), and wherein the at least one receiving slot (80) is positioned in a row extending in a second direction (D2) perpendicular to the first direction (D1), when the printheads (11-14) and fixation units (21-24) are mounted on the common carrier (50). 13. The printing assembly (1) according to claim 12, further comprising a transport mechanism (40) for moving the common carrier (50) with respect to the print substrate support (41) in the second direction (D2). 14. The printing assembly (1) according to claim 12 or 13, wherein the locking mechanism comprises a lever connected to a locking beam (70) extending in the second direction (D2, so that by pivoting the lever the locking beams (70) moves to a locking position, wherein all printheads (11-14) and fixation units (21-24) on the

100303NL01 21 common carrier (50) are secured thereto.

Claims

100303NL01 22 CONCLUSIONS

A method for three-dimensional ink jet printing of a multiple material structure (80, 90’), comprising the steps of: - providing at least one print head (11-14) and at least one fuser unit (21-24) on a common substrate (50) in a first arrangement, said common substrate (50) comprising a receiving slot assembly defining a plurality of receiving positions, wherein each print head (11-14) and each fuser unit (21-24) comprises a receiving portion mated to each of said receiving positions on the common substrate (50); - activating at least one print head (11-14) and at least one fuser unit (21-24) in the first arrangement to print and cure the first multiple material structure (90, 90°); - adapting the at least one print head (11-14) and the at least one fixing unit (21-24) to a second arrangement, different from the first arrangement, for printing and curing a second multi-material structure (90, 90°).

A method according to claim 1, wherein the step of adjusting further comprises at least one of the following steps: - changing at least one print head (11-14) and/or at least one fusing unit (21-24) to a different receiving position relative to the first arrangement; - changing a total number or print heads (11-14) and/or fusing units (21-24) disposed on the common carrier (50) relative to the first arrangement; and - controlling a different total number or print heads (11-14) and/or fusing units (21-24) disposed on the common carrier (50) relative to the first arrangement.

A method according to any preceding claim, further comprising the step of: - determining the first arrangement, comprising the steps of: - determining a first number (N) of print heads (11-14) and fuser units (21-24) required for printing the first plurality of material structure (90, 90’); - determining a first, relative positioning of the first number (N) of print heads (11-14) and fuser units (21-24) for printing and curing the first plurality of material structure (90, 90’);

100303NL01 23 - arranging the first number (N) of print heads (11-14) and fixing units (21-24) in the respective, first positioning on the common carrier (50), - printing the first multi-material structure (90, 90’) with the first number (N) of print heads (11-14) and fixing units (21-24) arranged in the respective, first positioning; - adjusting the first positioning and/or the first number (N) of print heads (11-14) and fuser units (21-24) on the common substrate (50) to a second arrangement for printing a second multi-material structure (90, 90°) different from the first, such that the relative positioning of the second number or print heads (11-14) and fuser units (21-24) on the common substrate (50) is different than during printing of the first structure (90, 80°).

A method according to claim 3, wherein the common carrier (50) defines a plurality of receiving positions, each of the print heads (11-14) and fusing units (21-24) comprising a receiving portion configured to be received snugly in each of the receiving positions.

A method according to any one of claims 3 and 4, wherein all print heads (11-14) and fuser units (21-24) comprise mating receiving parts and wherein the receiving positions comprise mating alignment means (62) arranged to matingly receive each of the receiving parts, so that all mounted print heads (11-14) and/or fuser units (21-24) are aligned with respect to each other.

Method according to any of claims 3 to 5, wherein the number (N) of print heads (11-14) and fusing units (21-24) is equal to or proportional to a number (N) of different materials predetermined for forming the respective multi-material structure (90, 90’).

Method according to claim 5, wherein the number (N) of print heads (11-14) and/or fusing units (21-24) varies per one or more material structures (90, 90’).

The method of claim 6, wherein each print head (11-14) comprises a row of nozzles (15, 16) extending in a first direction (D1) when disposed on the common support (50), and wherein the plurality of receiving positions are

100303NL01 24 extend in a row on the common support (50) in a second direction (D2), which is perpendicular to the first direction (D1).

Method according to claim 8, wherein a fixing unit (21-24) is provided between each two adjacent print heads (11-14) in the second direction (D2), one print head (11-14) each being arranged to jet a different material than the other print head (11-14).

10. Printer assembly (1) for three-dimensional ink jet printing of a multiple material structure (90, 90’), the print assembly (1) comprising: - a common carrier (50) comprising a receiving slot assembly with at least one receiving slot (60) defining a plurality of receiving positions, the carrier (50) being positionable and movable relative to a print substrate carrier (41); - a plurality of separate print heads (11-14) for jetting a radiation curable fluid onto the print substrate carrier (41); - a plurality of separate fixing units (21-24) for jetting the curable fluid onto the print substrate carrier (41) such that the fluid transitions to a solid phase; characterized in that : - the print heads (11-14) and the fusing units (21-24) each comprise a receiving part, each receiving part being adapted to be received appropriately in the at least one receiving slot (60) of the receiving slot assembly in each of the receiving positions; and - a control unit adapted to activate at least one print head (11-14) and at least one fusing unit (21-24), arranged on the common carrier (50), different arrangements for printing and curing different, plural material structures (90, 90’).

Printer assembly (1) according to claim 10, wherein the common carrier (50) is provided with a locking mechanism movable into a closed position for simultaneously securing the respective print heads (11-14) and fuser units (21-24) in their at least one receiving slot (60).

Printer assembly (1) according to claim 10 or 11, wherein the print heads (11-14) and the fusing units (21-24) have an appropriate working range (WR) in a first direction (D1)

100303NL01 25, which is determined by a width of a row of nozzles (15, 16) or one or more lamps (25), respectively, and wherein the at least one receiving slot (60) is located in a row extending in a second direction (D2) perpendicular to the first direction (D1), when the print heads (11-14) and fixing units (21-24) are arranged on the common carrier (50).

The printer assembly (1) of claim 12, further comprising a transport mechanism (40) for moving the common carrier (50) relative to the print substrate carrier (41) in the second direction (D2).

A printer assembly (1) according to claim 12 or 13, wherein the locking mechanism comprises a lever connected to a locking bar (70) extending in the second direction (D2), such that pivoting the lever moves the locking bar (70) to a locking position, wherein all print heads (11-14) and fuser units (21-24) on the common carrier (50) are secured thereto.