Device, special paper, and method for producing shaped articles

Abstract

The invention relates to a device, a special paper and a method for producing three-dimensional objects.

Claims

1. A special paper, which is suitable for producing a three-dimensional body from individual layers, which includes the following properties: a. a variable tendency to be dissolved by printing with a medium; b. a capacity of the special papers to bind to each other due to an activation in the areas defined by printing; and c. a solubility of the unbound special paper due to the action of a suitable solvent, heat and/or mechanical energy; wherein the special paper comprises: i. a water soluble polymer including polyvinyl alcohol; and ii. a short cellulose fiber, a naturally occurring substance, a metal, a stone, a mineral, or a ceramic.

2. The special paper of claim 1, wherein the special paper includes the cellulose fiber.

3. The special paper of claim 2, wherein the special paper includes a fluid or a powder which provides the binding capacity to the special paper.

4. The special paper of claim 1, wherein the activation of the binding capacity of the special paper takes place by a transferring of a fluid or a powder from an ink ribbon of a dot matrix printer, from an ink of an ink-jet printer or from a fixed powder of a laser printer or a laser copier.

5. The special paper of claim 1, wherein the solubility of the unbound special paper is due to the action of a solvent.

6. The special paper of claim 1, wherein the solubility of the unbound special paper is due to heat.

7. The special paper of claim 1, wherein the solubility of the unbound special paper is due to mechanical energy.

8. The special paper of claim 1, wherein the special paper is flat and smooth and has a uniform thickness and/or the special paper is made of materials that may be glued together.

9. A material system including a special paper, and a printable medium capable of changing a binding capacity of the special paper in the printed locations; wherein the printable medium includes polyvinyl alcohol, polymethyl methacrylate, or a wax; and wherein the special paper is suitable for producing a three-dimensional body from individual layers, which includes the following properties: a. a variable tendency to be dissolved by printing with a medium; b. a capacity of the special papers to bind to each other due to an activation in the areas defined by printing; and c. a solubility of the unbound special paper due to the action of a suitable solvent, heat and/or mechanical energy; wherein the special paper comprises: i. a polymer; and ii. a short cellulose fiber, a naturally occurring substance, a metal, a stone, a mineral, or a ceramic.

10. The material system of claim 9, wherein the printable medium changes the binding capacity due to microwave selectability of the printed paper.

11. The material system of claim 9, wherein the material system includes a temperature activatable substance and the binding capacity is due to a diffusion of the temperature-activatable substance.

12. The material system of claim 9, wherein the material system includes a binder material that melts and the printable medium includes a material that evaporates and prevents melting of the binder material that melts in the printed regions.

13. The material system of claim 10, wherein the binder material that melts includes a material that has a high absorption of microwave radiation having wavelength characteristic of a conventional microwave oven that heats water.

14. The material system of claim 9, wherein the binder material that melts is a plastic, and the printable material is free of humectant or other volatile constituents.

15. The material system of claim 9, wherein the printable medium includes water and a component that prevents or reduces evaporation of the water, wherein the component that prevents or reduces evaporation includes a solid thickener or a liquid thickener.

16. The material system of claim 9, wherein the printable medium includes the polyvinyl alcohol or the polymethyl methacrylate.

17. The material system of claim 9, wherein the polymer is water soluble.

18. The material system of claim 17, wherein the polymer includes polyvinyl alcohol.

19. The special paper of claim 1, wherein the special paper includes the cellulose fibers.

20. The special paper of claim 19, wherein the cellulose fibers have a length that is shorter than a thickness of the special paper.

21. The special paper of claim 19, wherein the cellulose fibers have a length of 20 to 30 m and/or the special paper has a thickness of 80 m.

22. A special paper, which is suitable for producing a three-dimensional body from individual layers, which includes the following properties: a. a variable tendency to be dissolved by printing with a medium; b. a capacity of the special papers to bind to each other due to an activation in the areas defined by printing; and c. a solubility of the unbound special paper due to the action of a suitable solvent, heat and/or mechanical energy; wherein the special paper includes: i. a polymer; and a ceramic.

23. The special paper of claim 22, wherein the special paper is a green state film.

24. The special paper of claim 23, wherein the special paper is dried for removing an evaporable liquid.

25. The special paper of claim 24, wherein the special paper has a thickness of less than 100 m.

26. The material system of claim 9, wherein the printable medium includes the wax.

27. The material system of claim 26, wherein the printable medium includes ceramic particles.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1: shows a schematic representation of the method according to the invention

(2) FIG. 2: shows a schematic representation of different printing methods;

(3) FIG. 3: shows a diagram of finishing methods;

(4) FIG. 4: shows the binding of the layers by means of diffusion, gravity or pressure;

(5) FIG. 5: shows different processes for removing the molded part

(6) FIG. 6: shows a device according to the invention for producing 3D molded bodies with the aid of paper rolls.

(7) Additional details, examples of preferred specific embodiments and advantages of the invention are discussed below.

EXEMPLARY EMBODIMENTS

Exemplary Embodiment 1 (Special Paper-Laser Printer-Home Oven

(8) In this embodiment of the invention, the focus is on home application. The embodiment facilitates the following scenario. A user is particularly interested in a 3D object on the Internet. He buys the special paper that is compatible with his 2D printer. Special software then allows him to convert a 3D format into individual 2D images. The operation is also accompanied by the program, and software assistants are provided that control the sheet sequence. The user can now print out his stack. After careful layering, the entire stack is placed in the oven. After a cooling phase, the user flushes his component out of the stack.

(9) This technology enables the user to produce a 3D component at home in less than 1 day. He does not have to make any investment or possess any special technical skills.

(10) The paper composition is crucial to the process steps. In this application example, cellulose-based paper is used. The fibers are short and have a length that is far less than the sheet thickness. The sheet thickness is 80 m, and the fibers are therefore 20 to 30 m in length.

(11) The grammage of the paper must be far less than 60 g/m.sup.2. It is thus a very loose and lightweight paper.

(12) The paper is bound by means of a water-soluble substance. In this example, the polymer polyvinyl alcohol (PVA) is used. The latter may be easily removed in the flushing process. Warm water increases the speed. If residues of PVA enter the sewage system, this does not pose an environmental hazard, since this plastic is biodegradable.

(13) The polymer must be selected in terms of its melting point or glass transition in such a way that it survives the fixing process during laser printing and does not melt. Otherwise, the printout would be damaged.

(14) This special paper (100) is subsequently printed according to layer data (101). The printing program ensures a numbering of sheets (100) and the highest possible toner application in each case. Individual sheets (100) are compiled into a stack (102, 400).

(15) Toner based on polymethyl methacrylate (PMMA) is generally used in laser printers. This toner, which is made of micro-balls, is stuck to the paper in a layer (203) according to the data and subsequently melted with the paper due to high heat.

(16) A paper printed in this manner demonstrates the desired hydrophobic property when placed in water. The image remains in the form of a thin film. The rest of the paper dissolves when gently stirred.

(17) This stack (400) is then subjected to finishing treatment by heat (103) in the oven. Since paper (100) is generally a poor heat conductor, the operation must last several hours, for example in the case of a 10-cm stack made of DIN A4 papers (400). The glass transition temperature of PMMA must again be exceeded to bind the paper. The glass transition temperature of the PVA should advantageously not be exceeded so that entire stack (401) is not compressed and thus harder to dissolve later on. The oven must therefore be expediently set to approximately 100 C.

(18) Paper stack (401) is then removed from the oven. To avoid internal distortion of the component because the thermoplastic is still soft, stack (401) must be cooled after the oven treatment. Once again, a certain amount of time is needed in this case, due to the heat conductivity. Stack (401) described above, which is 10 cm high and has the dimensions of a DIN A4 paper, should be age-hardened at room temperature for one hour.

(19) To dissolve (FIG. 5) the unprinted paper, stack (401) is placed in a water bath (501). This may be a tub or a sink. Warm water accelerates the operation. Additional rubbing by hand or with a brush detaches adhering paper faster (500). The water should not be too hot to prevent the component from distorting, and to avoid scalding the user. If the binding of the layers is insufficient, the individual layers will separate from each other.

(20) According to the invention, it is highly preferred that the basic substance of paper (100) is absolutely non-toxic and does not harm the environment. Dissolved material (502) may now be roughly separated from the water using a sieve and placed in the household trash. The rest is rinsed into the waste water.

Exemplary Embodiment 2 (Ceramic Special Paper-Ink-Jet Printer-Industrial Oven)

(21) The second example describes an industrial application of the aforementioned principle. The further benefits of the method are used here. An investment must be made prior to use.

(22) This time, a ceramic film in the green state is used as paper. It is essentially made of a silicate ceramic compound. This compound is mixed with PVA and water and rolled out into a paper/film. A drying process the

(23) follows, in which all evaporable liquid is removed. The drying process must take place below the glass transition point of the PVA and in a gentle manner to avoid cracking. The temperatures must be kept below 100 C. The paper may subsequently be plasticized between two heated rollers, due to the action of heat, and calibrated for good parallelism and layer thickness control.

(24) This paper may be further processed into sheets or used as a roll (600). After drying, it is elastically pliable, due to a thickness of less than 100 m, and may be bent into relatively narrow rolls having a radius of 50 mm.

(25) A device according to the invention for printing this roll provides for an unrolling unit, from which the material is fed to the process units. It is fed in a straight web under an ink-jet print head (602), an intermediate heating system and a calibration station (603).

(26) In the example according to the invention, wax is used as the ink. The melting point is set by adding a low-melt polymer (polyethylene PE). This material may be safely processed with the aid of an ink-jet print module at a temperature of 70 C. Ceramic particles may preferably be added to the ink to reinforce the ceramic films.

(27) The wax striking the paper is immediately cooled by the films and remains on the surface. A targeted local heating is therefore carried out in a subsequent step. The wax penetrates the paper. A precise setting of the speed of the web and the heating power are necessary to bind the paper roll afterward.

(28) Another possible unit comprises diametrically opposed rollers. The projecting wax after the heating process, which is still flexible, is calibrated to an exact projection over the film.

(29) The web is then rolled up onto a roller (601) under a defined pretension. Ideally, the images should now be situated one on top of the other, so that the desired components would be accurate in terms of geometry and size with imaginary cuts through the roll.

(30) Since inaccuracies in the system are to be anticipated, sensors are used which continuously monitor the roll thickness. This signal is used to actively adjust the position and content of the printed images. All necessary conversions, such as conversion to polar coordinates, must take place.

(31) The printing process runs continuously. The speed is limited only by the ink-jet print head and its design. All processing units may also be present multiple times. A true high-capacity production process is thus to be implemented by the invention.

(32) At the end of the printing process, the roll is subjected to binding. As in the process for the home user, an oven is used for this purpose. The wax layers now melt into each other, and water-insoluble bodies form. The exact calibration and the high density of the rolled ceramic paper results in a highly dense ceramic green body.

(33) The removal in this case takes place in the same manner as described, using a water bath. Water changes, other temperature controls, filtration at the dissolving medium, mechanical cleaning by means of high-pressure jets and automatic brushing may take place on an industrial scale. The loose parts may be removed from the solution by sieving.

(34) In this example using ceramic paper, a sintering step advantageously takes place after these processes. The wax is burned off in a first step. This takes place at a temperature of up to 500 C. The molds are self-supporting, due to the high packing density even after this so-called unbinding. The burning takes place at 1,200 C.

LIST OF REFERENCE NUMERALS

(35) 100 Special paper 101 Printed area 102 Paper stack 103 Heat 104 Component 200 Ink-jet print head 201 Ink droplet 202 Toner roller 203 Toner image 204 Printing needle 205 Ink ribbon 300 Heat source 301 Penetrated material 302 Spreading with material 303 Blow-off device 400 Unbound stack 401 Bound stack 402 Capillary action 403 Gravity action 404 Pressure action 500 Adhering paper 501 Water bath 502 Free paper remnant 503 Molten paper 504 Pulverized paper 600 Roll, including source material 601 Finished stack 602 Print unit 603 Heating and leveling unit