Abstract
The disclosure relates to a method for producing of refiner disc segments. The method for producing of the invention allows for forming a multitude of refiner segments with only one forming process of a first die which may be lightweight and has reduced cost while at the same time a surface structure with high hardness which reduces wear of the die's surface. The method for producing a disc-type refiner segment for refining lignocellulosic material includes 3D printing a first model; forming a first die part using investment casting; 3D printing a second model; combining the first die part and the second model to create a first die model; using the first die model to generate for forming a sand model by compressing molding sand between the first die and the second die; and casting a refiner disc segment by casting a metal material using the sand model.
Claims
1. A method for producing a disc-type refiner segment for refining lignocellulosic material, comprising: providing production data of a first model; supplying the production data of the first model to a 3D printer; 3D printing the first model; using the first model to generate a first part mold; molding or casting with a first metal material having a first melting point a first inner die part using the first part mold; providing production data of a second model; supplying the production data of the second model to a 3D printer; 3D printing the second model from a printing material; combining the first inner die part and the second model to create a first die model; using the first die model to generate a first die mold; performing a burnout process on the first die mold; molding or casting with a second metal material having a second melting point a first die using the first die mold, wherein the second melting point is lower than the first melting point; providing a second die; forming a sand model by compressing molding sand between the first die and the second die; and casting a refiner disc segment by casting a third metal material using the sand model.
2. The method according to claim 1, wherein the steps of forming the sand model and casting the refiner disc segments comprise: subsequently forming at least sand models by compressing molding sand between the first die and the second die; combining the at least sand models to form a row; and casting the refiner disc segments by casting a metal material into the gaps between two neighboring sand models of the row.
3. The method according to claim 1, wherein the material with low melting point is selected from wax, plastic, resin, and a polymer material.
4. The method according to claim 1, wherein the step of 3D printing the first model comprises 3D printing the first model from a material with low melting point, and the step of using the first model to generate a first sand mold comprises performing a burnout process on the first sand mold.
5. The method according to claim 1, wherein the casting steps or molding steps comprise vacuum pressure casting, counter-gravity casting, an investment casting process, lost foam casting, or lost wax casting.
6. The method according to claim 1, further comprising at least one chasing process after one or both of the 3D printing steps.
7. The method according to claim 1, further comprising at least one chasing process after one or all of the molding steps or casting steps.
8. The method according to claim 1, wherein the first part mold is a sand mold or a ceramic shell mold.
9. The method according to claim 1, wherein the first die mold is a sand mold or a ceramic shell mold.
10. The method according to claim 1, wherein the step of providing the second die comprises: providing production data of a third model; supplying the production data of the third model to a 3D printer; 3D printing the third model; using the third model to generate a second die mold; and molding or casting with the second metal material the second die using the second die mold.
Description
BRIEF DESCRIPTION OF THE FIGURES
(1) FIG. 1(a)-(e) are side views illustrating a sand model fabrication process according to the known state of the art.
(2) FIG. 2(a)-(c) are side views illustrating a refiner disc segment fabrication process according to the known state of the art.
(3) FIG. 3 (a)-(g) are different views illustrating a fabrication process of a first inner die part according to an embodiment of the present disclosure.
(4) FIGS. 4 (a)-(f) and 5 (a)-(c) are different views illustrating a fabrication process of a first die according to an embodiment of the present disclosure.
(5) FIG. 6 (a)-(b) are side views illustrating a fabrication process of a sand model fabrication process according to an embodiment of the present disclosure.
(6) FIG. 7 (a)-(c) are side views illustrating a fabrication process of a refiner disc segment fabrication process according to an embodiment of the present disclosure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
(7) In the following, the present disclosure will be described with reference to figures schematically showing various exemplary embodiments. The embodiments shown in the figures are not necessarily shown to scale, and in some cases dimensions may have been selected which more clearly show the principle of the present invention. Identical or similar reference signs for identical or similar elements and components are used both in the drawing and in the description. All embodiments shown and described are combinable with each other in whole or in part, unless explicitly stated otherwise.
(8) Both in the description and in the figures, the same or similar reference signs are used to refer to the same or similar elements or components. In order to keep the description concise, elements already mentioned in other figures are not necessarily explicitly mentioned again in the description for each further figure, especially since a list of reference signs is attached.
(9) The present invention is based on the use of a 3D printer to produce a model of a refiner segment structure. Said model is used to produce a mold in which a first die is cast. The first die forms a surface of a sand model, which then is used for casting the final refiner disc segment.
(10) FIG. 3 (a)-(g) (also commonly denoted as FIG. 3) are different views illustrating a fabrication process of a first inner die part according to an embodiment of the present disclosure.
(11) In FIG. 3(a), a first model 10 is 3D printed using a 3D printer system comprising a 3D printer head 1 and a table 3. Further elements of such 3D printers are not explicitly shown and may comprise supply of printing material, motors for moving the printer head 1 and/or table 3, circuitry, power source, data storage and the like as acknowledged by the person skilled in the art. During fabrication indicated in FIG. 3(a), production data of a first model is provided, supplied to the 3D printer; and the first model 10 is 3D printed.
(12) In the embodiment shown in FIG. 1, the material used by the 3D printer head 1 (“printing material”) is a material with low melting point, e.g. below 200° C., preferably below 150° C., most preferably below 100° C., e.g. wax, plastic, resin, or a polymer material (e.g. photopolymer on wax basis assisted by LED curing at printing). Most preferably, the printing material is ductile at room temperature to allow for convenient 3D printing at room temperature.
(13) Further, the printing material preferably as a low viscosity (e.g. at or below 800 cps, preferably 700 at 25° C.) above a certain temperature, e.g. 200° C. so that the printing material is able to flow our of a form during a burnout process described later. Alternatively, the printing material may also be burned to ashes or evaporated during the burnout process.
(14) FIG. 3(b) shows the finished 3D printed first model 10. As shown in FIG. 3(b) the first model contains features of the refiner disc segment to be produced, e.g. surface structures 4, and also a tree-like structure (“spruing”, no reference signs) of the printing material that will provide paths for the molten casting material to flow and for air to escape (see FIG. 3(c) et seqq.). The spruing does not have to be hollow, as it will be melted out later in the process. The spuring also includes the so-called cups (funnel-shaped structures on the right of FIG. 3(b)) which later serve for forming a reservoir and casting aid during casting (see FIG. 3(e)).
(15) FIG. 3(c) shows that the first model 10 is used to form a mold 100, denoted as first part mold 100. In one embodiment, the mold 100 may be formed by embedding the first model in casting sand (like the sand used for forming the sand models 80, 80 p described herein). Alternatively, the first model 10 may also be coated (dipped) in silica slurry and dried repeatedly until a silica coat around of desired thickness is formed around the model. The way of forming the first part mold 100 is not particularly limited herein.
(16) In the embodiment shown in FIG. 3(d), a burnout process is performed on the mold 100 obtained in FIG. 3(c). That is, the first part mold 100 containing the first model 10 is placed cup-down (i.e. openings of the mold 100 facing down) in a kiln or the like, whose heat hardens the mold material (e.g. sand, silica) into a shell, and the printing material W of first model 10 melts and runs out. The melted material W can be recovered and reused or it is simply burned up or evaporated (not shown). Now all that remains of the original first model 10 is the negative space formerly occupied by the printing material inside the hardened shell of the first part mold 100. The spuring, i.e. feeder, vent tubes and cup are also now hollow. The temperature of the burnout process is also dependent on the used printing material.
(17) FIG. 3(e) shows a casting process according to one embodiment of the present disclosure. The burned-out mold 100 obtained in FIG. 3(d) is turned by 180° and a first casting material (“first metal material having a first melting point”) M1 is filled into the cups of the mold 100. The first metal material is characterized by both, a relatively high melting point (compared to the second metal material M2 described below) and high hardness. Preferably, the first melting point is above 1200° C., more preferably above 1350° C.
(18) More particularly, the first melting point may refer to a melting temperature of a hard metal alloy, e.g. 316L stainless steel, 347L stainless steel, carbon steel, tungsten steel or the like. Another desired characteristic of the first metal material is hardness, most preferably a Knoop Hardness (KHN) of 200 kg/mm.sup.2 or more, more preferably 250 kg/mm.sup.2 or more.
(19) The casting process in FIG. 3(e) results in the first inner die part 50 depicted in FIG. 3(f). In the present embodiment, the cast first inner die part 50 is removed from mold 100 by destroying the mold 100. Alternatively, mold 100 may also be a reusable mold of two shell parts which are separated to lay open the first inner die part 50. The word “inner” in first inner die part 50 refers to the location of the first inner die part 50 in the final die 30 (see FIGS. 4(b) and (c)). That is, the first inner die part 50 provides the surfaces that will be in contact with the casting sand S during compression of the sand model (c.f. 80 in FIG. 7, 80p in FIG. 1). Accordingly, the position of the first inner die part 50 is on the inside of the gap between first and second dies (60 and 70 in FIG. 7).
(20) The first inner die part 50 is subjected to a chasing process for removing the vents and feeders formed by filling the spuring cavities which results in first inner die part 50 depicted in FIG. 3(g). Further, surface processing may be performed during chasing.
(21) As mentioned above, the most important part of the first inner die part 50 are the surface structures 4 which will determine the corresponding surface structures 4 of the final refiner disc segments (2 in FIG. 7). To reduce wear of said surface structures 4 first metal material M1 has high hardness.
(22) FIG. 4 (a)-(f) (also denoted as FIG. 4) and FIG. 5 (a)-(c) (also denoted as FIG. 5) are different views illustrating a fabrication process of a first die 60 according to an embodiment of the present disclosure.
(23) In FIG. 4(a), a 3D printing process of a second model 20 using a 3D printer is depicted. The 3D printer as well as the characteristics of the 3D printing process may be similar or identical to the 3D printing of the first model 10 in FIG. 3(a) (apart from the production data, apparently) and details thereof are not repeated here.
(24) As indicated in FIG. 4(b), the second model 20 is then combined with the first inner die part 50 obtained in the process of FIG. 3. “Combined” may mean that a cavity of the first inner die part 50 corresponds to a protuberance of the second model 20 and that the form-fitting first inner die part 50 and second model are simply stuck together. Alternatively, the two parts 20 and 50 may also be adhered to another or the 3D printing of the second model may be performed directly onto the first inner die part 50 (instead of the table 3 of FIG. 4(a)). The second model 20 depicted also contains spuring as descried above.
(25) FIG. 4(c) indicates the result of the combination of first inner die part 50 and second model 20, i.e. the first die model 30 as intermediate product. The first die model 30 is then used to produce a first die mold 200 as shown in FIG. 4(d). The process of forming the mold is preferably similar or identical to the process of forming the first part mold 100 (FIG. 3(c) with related description above) and details thereof are not repeated herein.
(26) The difference between the burnout process of FIG. 3(d) with description above and the burnout process in FIG. 4(e) is that only the parts occupied by the second model 20 are burned-out of the first die mold 200. The part of first die model 30 established by the first inner die part 50 is made from hard metal and is not affected by the burnout process and remain in the first die mold 200.
(27) In FIG. 4(f), a casting process using a second metal material M2 and the burned-out first die mold 200 obtained in FIG. 4(e) is depicted which results in the first die 60 illustrated in FIG. 5. As shown, during casting with the second metal material M2 in mold 200, the first inner die part 50 is encapsulated (on the “backside” thereof) with the second metal material M2.
(28) As mentioned above, the second metal material M2 must have a lower melting point than the first metal material M1 to avoid re-melting of the first inner die part 50 is made from the first metal material M1. Since the hardness of the second metal material is of reduced relevance, a rather soft and light material is preferred, e.g. aluminum or an aluminum allow. The combination of a hard but rather thin hard metal surface provided by first inner die part 50 and a softer metal core form the second metal material also offers advantageous resistance to breaking due to higher flexibility compared with a die only made from the hard metal material M1. To avoid damage (cracks) during heating or cooling of the first die (e.g. after the casting of the second metal material M2 or during operation) stress release gaps may be provided (not shown).
(29) In FIG. 5(a), a cut through the second die 60 and the resulting surface structures 4 of the first die 60 are shown. The spuring (vents and flow channels) of the second model now cast in the second metal material M2 and part of the first die may not need to be removed (chasing) but may serve as holding structures to improve stability and rigidity of the first die 60. FIG. 5(b) show the second die 60 after a chasing process. FIG. 5(c) is a side view from outside showing the outline of the second die 60 including the surface structures and the side wall.
(30) FIG. 6 (a)-(b) are side views illustrating a fabrication process of a sand model according to an embodiment of the present disclosure. The first die 60 is then used to form a sand model by compressing (e.g. foundry) sand between the first die 60 and a second die 70 as shown in FIGS. 6(a) and (b) (commonly denoted as FIG. 6). The process indicated in FIG. 6 may be similar or identical to the process described with reference to FIG. 1 (i.e. the prior art section). However, the inventive is not limited thereto. The second die may also be formed by a flat surface (e.g. a fixed wall) and the first die is pressed against the wall with sand filled in a gap between them. The resulting sand model may have a side wall forming a trough with the negative of the surface structures on its bottom. In this very simple embodiment, the resulting refiner disc segment may be cast by filling the trough with a metal melt (third metal material).
(31) In the shown embodiment, however, sand S is compressed between the first and second dies 60 and 70 (also refer to dies 60 and 70 in FIG. 1). Thus, the side of the sand model (80 in FIG. 7) corresponding to the second die's surface may also have certain structures which may serve fixing the resulting refiner disc segment to a carrier or the like, for example protrusions fitting to holes of the carrier (or vice versa), bolt holes etc.
(32) FIG. 7 (a)-(c) (commonly denoted as FIG. 7) are side views illustrating a fabrication process of a refiner disc segment fabrication process according to an embodiment of the present disclosure. The process shown in FIG. 7 may be similar or identical to the process described with reference to FIG. 2 above, i.e. the prior art section. Difference between the embodiment of FIG. 7 and the prior art is the stable quality of the sand models 80 produced. This, in turn, leads to improved quality, higher operation lifetime and reduced costs of the obtained refiner disc segments.
(33) From the above, it should be appreciated that the refiner disc segments may be comprise complex geometrical shapes, e.g. corners, edges and angles, which are not or hard reproducible issuing cutting tools or the like. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to accommodate various modifications and equivalent arrangements include within the spirit and the scope of the appended claims. Further, it should be understood that all described embodiments are combinable and compatible unless otherwise specified.
REFERENCE SIGNS LIST
(34) 1 3D printer 2 refiner disc segment 3 table 4 surface structures 10 first model 20 second model 30 first die model 50 first inner die part 60 first die 70 second die 80 sand model 100 first part mold 200 first die mold M1 first metal material M2 second metal material M3 third metal material W printing material with low melting point S molding sand 2p refiner disc segment (prior art) 4p surface structures (prior art) 60p first die (prior art) 70p second die (prior art) 80p sand model (prior art) M3p third metal material (prior art)
