Blade, refiner comprising a blade, and method for manufacturing a blade

Abstract

The present invention relates to a blade (10) for a refiner for defibrating a lignocellulosic material, the blade (20) comprising a refining surface (40) having a plurality of bars (20) separated by grooves (30), wherein each bar (20) has a bar width (w) and a bar height (h), said bar height being a height from a bottom of an adjacent groove to an upper end of said bar, and wherein at least one bar of the blade has a bar width of 1.5 mm or less and a bar height of at least 5 mm, and at least one groove (30) of the blade having a groove width (gw) of 1.5 mm or less, at least one of the bars (20) comprises a bar opening (23) in the form of a through-hole that extends through the bar (20) from one groove (30) to an adjacent groove (30). The invention also relates to a refiner comprising at least one blade, and to a method for manufacturing the blade.

Description

[0001] BLADE, REFINER COMPRISING A BLADE, AND METHOD FOR MANUFACTURING A BLADE

[0002] TECHNICAL FIELD

[0003] The present invention relates to a blade for a refiner for refining lignocellulosic material. The invention also relates to a refiner comprising such a blade and to a method for manufacturing the blade.

[0004] BACKGROUND

[0005] A disc refiner is commonly used within the pulping industry for refining lignocellulosic material used in the production of fibrous material such as paper and board.

[0006] The disc refiner comprises two or more opposite refining elements, at least one of which is rotatable. The rotating refining element can be referred to as a rotor or a rotor side blade, whereas the non-rotating or stationary refining element can be referred to as a stator or a stator side blade. Between the refining elements is a refining gap, where the material to be refined is ground against the refining surfaces. The refining surface of the refining elements comprises a plurality of bars, separated by grooves, that serve to refine the lignocellulosic material during use.

[0007] In some applications, the rotor side blade and the stator side blade are circular blades that are mounted on one stationary and one rotary frame element in the refiner, such that they face each other during use. Often, the stator side blade and the rotor side blade are divided into many smaller blade segments that each cover a sector of the frame element and that when mounted together form the circular blades. There is generally an opening at the center of at least one of the circular blades for insertion of the lignocellulosic material, such that the material enters at the center and is transported in a radial direction during refining.

[0008] The wear on blades during use is typically very high, resulting in frequent need for replacing. To increase the lifetime of refiner blades and also their refining capacity, it is desirable to provide denser blades with a finer pattern having an increased combined length of refining surface bars, referred to as a total cutting-edge length. For this purpose, it is also desirable to provide narrow grooves to enable a high density of refiner bars.

[0009] When manufacturing such refiner blades however, casting them in traditional sand molds results in increasingly narrow grooves at the bottom of the bars due to the clearance angle of the mold that causes bars to be thicker at the bottom. Such narrow grooves are particularly prone to plugging, thus severely limiting the capacity of the blades for refining lignocellulosic material.

[0010] One attempt to resolve this problem is provided by US7419112B2, where grooves of different widths are arranged to increase the flow of material along the refiner blade.

[0011] However, there is a need for further improvements within this field.

[0012] SUMMARY

[0013] The object of the present invention is to eliminate or at least to minimize the problems discussed above. This is achieved by a blade, a refiner comprising a blade, and a method for manufacturing a blade according to the appended independent claims.

[0014] The blade of the invention is suitable for a refiner for defibrating a lignocellulosic material, and the blade comprises a refining surface having a plurality of bars separated by grooves, wherein each bar has a bar width and a bar height, said bar height being a height from a bottom of an adjacent groove to an upper end of said bar. Also, at least one bar of the blade has a bar width of 1.5 mm or less and a bar height of at least 5 mm. Furthermore, at least one groove of the blade has a groove width of 1.5 mm or less. Also, at least one of the bars comprises a bar opening that extends through the bar from one groove to an adjacent groove, said bar opening being a through- hole through the bar.

[0015] Thereby, a blade with narrow bars and deep grooves is achieved, and this provides a finer pattern with an increased cutting-edge length that improves refining as compared with prior art blade segments. Also, with a bar height of at least 5 mm, the lifetime of the blade is increased since the bars can be subjected to wear for a longer time before needing replacement. Providing narrow grooves enables a higher density of refiner bars to thereby increase the total cutting-edge length of the blade.

[0016] By providing the bar opening, steam and / or lignocellulosic material is able to flow through and the risk of blockage or plugging in the groove is decreased or even prevented. This is particularly advantageous where the groove width is small, since the risk of plugging the grooves increase with decreasing groove width. By thus providing at least one but preferably a plurality of bar openings, plugging of the grooves can be minimized or even eliminated, thereby improving refining of the lignocellulosic material and ensuring that flow of steam and lignocellulosic material is rendered efficient.

[0017] Suitably, at least one bar has a bar width of less than 1 mm, preferably less than 0.7 mm and more preferably less than 0.5 mm. Thereby, an even finer pattern can be achieved, thus further increasing the cutting edge length.

[0018] Also, at least one bar may have a bar height of at least 10 mm, preferably at least 15 mm and more preferably at least 20 mm. Thereby, the lifetime of the blade is further increased due to the increased wear that the bar can be subjected to before replacement is needed.

[0019] Suitably, at least one groove has a groove width of 1 mm or less, preferably 0.7 mm or less and more preferably 0.5 mm or less. Thereby, the total cutting edge of the blade is significantly increased since the bars may be provided very close together. In some embodiments, the groove width may be as small as 0. 1 mm.

[0020] Suitably, the plurality of bars have a mean bar width of 1.5 mm or less or have a mean bar height of 5 mm or more. Thereby, a fine pattern is achieved where the bars are narrow and able to withstand severe wear.

[0021] Suitably, two adjacent bars each comprise at least one bar opening, and the bar opening of one of the bars is non-aligned with the bar opening of the other bar. Thereby, a flow of steam and / or lignocellulosic material through the bars is enabled and by the openings being non-aligned, the material is encouraged to flow both along the grooves and through the bar openings, thus improving the flow.

[0022] Also, the bar openings may be non-aligned by being at different heights from the bottom of the groove between the two bars or at different positions in the radial direction. This provides a distribution of the bar openings that allows for an efficient flow of steam and / or lignocellulosic material through the bar openings and along the grooves.

[0023] Suitably, at least one of the bars comprises a plurality of bar openings. Thereby, the flow is further improved and the risk of blockage in the grooves further decreased.

[0024] In some embodiments, at least half of the bars comprise at least one bar opening. This ensures that the flow of lignocellulosic material is rendered efficient across the blade.

[0025] Suitably, two adjacent bars each comprise at least one bar opening, and the bar opening of one of the bars is aligned with the bar opening of the other bar to form a flow channel. Thereby, the steam and / or lignocellulosic material can flow through the flow channel and be transported efficiently across the blade without having to pass along a groove.

[0026] Suitably, the blade forms a circular sector with a central angle of 10° - 360°. Thereby, the invention encompasses refiner blades that are provided as a single portion forming the entire blade, as well as refiner blades that are formed by circular sectors that may combine to form the blade.

[0027] The present invention also comprises a refiner having at least one blade according to the invention. Thereby, the advantages of the blade are realised in a refiner for refining lignocellulosic material.

[0028] The present invention also comprises a method for manufacturing the blade of the invention. The method comprises providing production data of the blade, supplying the production data to a 3D printer, and 3D printing a pattern of the blade.

[0029] By manufacturing the blade using this method, a very fine pattern of refiner bars and grooves are obtainable. Traditional manufacturing methods use molding to produce blades for refiners, and this severely limits the density of refiner bars on the blade and thereby the total cutting-edge length of the blade.

[0030] Also, by 3D printing the blade, bar openings can be provided on the blade to achieve the advantages disclosed herein. Bar openings, preferably forming channels through multiple refiner bars or being non-aligned to encourage flow both along refiner bars and through them, cannot be achieved by molding or by other known prior art methods for manufacturing blades.

[0031] Many additional benefits and advantages of the present invention will be readily understood by the skilled person in view of the detailed description below.

[0032] DRAWINGS

[0033] The invention will now be described in more detail with reference to the appended drawings, wherein:

[0034] Fig. 1 discloses a perspective view of a portion or a blade according to a first embodiment of the invention;

[0035] Fig. 2 discloses schematically a planar view from the side of a refiner bars and grooves of the blade of Fig. 1 ;

[0036] Fig. 3 discloses a perspective view of a cross section of the blade of the second embodiment showing bar openings;

[0037] Fig. 4 discloses a planar view from above of refiner bars showing bar openings;

[0038] Fig. 5 discloses one embodiment of a profile of a bar opening; Fig. 6 discloses a perspective view of a portion of the blade according to a second embodiment showing flow channels formed by bar openings in refiner bars;

[0039] Fig. 7 discloses a perspective view of the blade according to the second embodiment showing more flow channels formed by bar openings; and

[0040] Fig. 8 discloses the method according to the invention.

[0041] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the respective embodiments, whereas other parts may be omitted or merely suggested. Any reference number appearing in multiple drawings refers to the same object or feature throughout the drawings, unless otherwise indicated.

[0042] DETAILED DESCRIPTION

[0043] Fig. 1 discloses a blade 10 for a disc refiner according to a first embodiment of the present invention. The term “blade” is used to denote a circular sector of a refiner blade, where the circular sector has a central angle of 10° - 360°. Thus, the blade of the invention may be a circular blade, but it may also be a circular sector of a blade so that a plurality of blades can be combined to form a circular refiner blade.

[0044] If the blade has an angle smaller than 360°, the blade is delimited by edges in a circumferential direction of the circular sector, and it is in particular to be noted that such edges are not limited to being radii of a circle but instead can have any straight or curved form as long as they are able to connect an inner periphery to an outer periphery.

[0045] When in use, the blade 10 is generally mounted in a disc refiner (not shown) and serves to refine lignocellulosic material by acting as a blade within a blade pair that are arranged to face each other, wherein at least one of the blades in the pair is arranged to rotate. Generally, a blade that is arranged to rotate in the disc refiner is referred to as a rotor side blade, whereas a blade that is arranged to be stationary is referred to as a stator side blade. The term lignocellulosic material is used herein to mean materials containing lignin, cellulose and hemicellulose. One example of such materials is wood, others include other agricultural or forestry wastes. When refining lignocellulosic material with a disc refiner, the material is generally fed into the disc refiner through an opening at a center of one of the blades and is refined while moving radially outwards between the blade pair.

[0046] The term opposite or opposing when referring to blades of a disc refiner is used herein to denote blades that are arranged facing each other and with a common central axis on which at least one of the blades can rotate. Generally, opposing blades are arranged so that a refiner zone of one blade is directly facing a refiner zone of the other blade when the blades are not moving and so that the refiner zone of a rotor side blade passes directly opposite a refiner zone of a stator side blade during operation in which the rotor side blade rotates around the central axis.

[0047] Fig. 1 discloses the blade 10 as a circular sector with curved edges 11, 12. The blade 10 is further delimited by an inner periphery 13 and an outer periphery 14. On the blade 10, a plurality of refiner bars 20 are arranged on a base 15 and the bars 20 are separated by grooves 30 that may extend down to the base 15 or that may be of varying depths as seen from a refining surface 40 that is defined as a surface formed by upper ends 21 of the bars 20. In some embodiments, the blade 10 comprises bars 20 distributed across the entire blade 10, but in other embodiments there may be portions lacking bars 20 completely. In some such embodiments, portions lacking bars 20 may be placed between portions with bars 20, or alternatively or additionally portions lacking bars may be placed at the inner periphery 13 and / or at the outer periphery 14.

[0048] Each of the bars 20 extend at least partially in a radial direction D, i.e. in a direction from the inner periphery 13 towards the outer periphery 14. That the bars 20 extend in the radial direction at least partially is to be understood as the extension of the bars 20 having a radial component but they may also have a component that is perpendicular to the radial direction. The blade 10 may also comprise at least one mounting opening 16 that is provided for mounting the blade 10 in the refiner. In other embodiments, mounting of the blade 10 may take place in any other manner and may optionally comprise other features or details that facilitate or enable mounting. Such features or details are well known to the skilled person, as is the manner in which blades 10 can be mounted and used in the refiner.

[0049] When in use, the bars 20 refine the lignocellulosic material by an edge 22 at the upper end 21 cutting the material (see Fig. 2). This edge 22 is referred to as a leading edge 22 and is the edge 22 of the upper end 21 that faces in an intended rotational direction R. A cutting-edge length of the blade 10 is defined as a total length of the leading edge of the bars 20 divided by a radius r of the blade 10, i.e. a line from a point on the inner periphery 13 to the closest point on the outer periphery 14. When increasing the cutting- edge length by providing a fine pattern with narrow bars 20 arranged closer together, the refining is improved as is well known in the art.

[0050] Each bar 20 has a bar width w and a bar height h. The bar width w is suitably measured at a broadest part of the bar 20 and the bar height h is a height from a bottom of a groove 30 adjacent to the bar 20 and to the upper end 21 of the bar 20, i.e. from the bottom of the groove 30 to the refining surface 40. In some embodiments, a plurality of bars may have the same bar width w and bar height b, but in other embodiments they may vary from one bar 20 to another. Also, in some embodiments the bar height h measured in each of the adjacent grooves 30 for one refiner bar 20 may be the same (i.e. the grooves 30 may have an equal or substantially equal depth), but in other embodiments the bar height h may differ depending on which of the adjacent grooves 30 are used for measuring the bar height h. In such embodiments, when it is said herein that the bar height h of the bar 20 has any given length, this is to be understood as the bar height h measured in at least one of the adjacent grooves 30 having this length.

[0051] In the blade 10 of the present invention, at least one bar 20 has a bar width w of 1.5 mm or less and a bar height h of at least 5 mm. This renders the bar 20 both narrow, so that a fine pattern can be achieved in order to provide a long cutting-edge length on the blade 10, and tall to ensure a long lifetime of the blade 10. In some embodiments, at least one bar 20 has a bar width w of less than 1 mm and preferably less than 0.7 mm, more preferably less than 0.5 mm. This ensures an even finer pattern to be created on the blade 10. In some embodiments, at least one bar 20 has a bar width 2 of 0.2 mm.

[0052] Also, in some embodiments, the bar height h is at least 10 mm, preferably at least 15 mm and more preferably at least 20 mm. This ensures an increased lifetime of the blade 10 to ensure less frequent replacement of worn blades.

[0053] Also, in the blade 10 of the present invention, at least one of the grooves 30 has a groove width gw of 1.5 mm or less. This renders the groove 30 narrow so that the density of the bars 20 is increased, thereby significantly increasing the total cutting-edge length of the blade 10. In some embodiments, at least one groove has a groove width of 1 mm or less, preferably 0.7 mm or less and more preferably 0.5 mm or less. Also, at least one of the grooves 30 may have a groove width of 0.2 mm.

[0054] Advantageously, a plurality of grooves 30 may have the groove width gw disclosed above. Also, the groove width gw may vary along a single groove 30 or may vary such that the groove width 30 of one groove 30 differs from that of another groove 30 of the blade 10.

[0055] The design of the bars 20 and grooves 30 of the refiner blade 10 according to the present invention render the blade 10 particularly suitable for use in low consistency refining where the pulp consistency is typically in the range 3 - 5 %.

[0056] In some embodiments, a plurality of refiner bars 20 in at least one portion of the refiner blade 10 has a mean bar width of 1.5 mm or less or have a mean bar height of 5 mm or more. Similarly, a plurality of grooves 30 in at least one portion of the refiner blade 10 has a mean groove width of 1.5 mm or less. This ensures that a fine pattern can be achieved across the blade 20 and thereby increases the advantages described above. In other embodiments, all refiner bars 20 of the blade 10 have the mean bar width of 1.5 mm or less or have the mean bar height of 5 mm or more, and all the grooves have a mean groove width of 1.5 mm or less.

[0057] In such embodiments, the mean bar width, mean bar height and mean groove width may preferably be as the bar width w and bar height h given above for a single bar 20 and as the groove width gw given above for a single groove 30.

[0058] In the first embodiment, at least one of the bars 20 comprises a bar opening 23 that extends through the bar 20 from one adjacent groove 30 to the other. This is shown in Fig. 4 where bar openings 23 are indicated by dashed lines and where two bars 20 comprise bar openings 23 but another bar 20 does not. The bar opening 23 may have any suitable cross-sectional shape such as circular, oval, rectangular, or any other shape. Fig. 5 shows one embodiment where the bar opening 23 has an elongated lower portion and a narrowing upper portion, and this is one suitable shape but there are many others. The bar opening 23 has an opening width ow and an opening height oh, and the size of the opening width ow and the opening height oh may vary as desired to achieve a bar opening 23 with suitable dimensions to allow a flow of steam and / or lignocellulosic material through the bar opening 23. Also, the size and shape of one bar opening 23 may differ from any other bar opening 23 provided on the same blade 10.

[0059] The bar opening 23 is defined as an opening that extends through the bar 20 so that a connection is established between the groove 30 on one side of the bar 20 and the groove 30 on an opposite side of the bar 20. The bar opening 23 is delimited by material of the bar 20, and it is in particular to be noted that the bar opening 23 is delimited by material of the bar 20 around its entire circumference, i.e. that the bar opening 23 is not in the form of a notch, a groove or an indentation. Also, it is an advantage that the bar opening 23 is arranged in the bar 20 as such and not underneath it.

[0060] The purpose of the bar opening 23 is to allow the lignocellulosic material and / or steam to pass through during refining to facilitate the transport across the blade 10. It also serves to minimize or even eliminate the risk of inefficient refining due to clogging of the grooves 30 on the blade 10 since it allows for lignocellulosic material and steam to move not only along the grooves 30 but also through the bar opening 23 from one groove 30 to the other. It is a particular advantage that the bar opening 23 is provided as a through-hole in the bar 20 rather than as a groove through the bar 20 or even an interruption of the bar 20, since this enables any number of bar openings 23 provided on the blade 10 without decreasing the refining area provided by the bars 20. If the bar opening 23 were instead to be provided as interruptions or grooves in the bars 20, this would significantly decrease the area available for refining the lignocellulosic material, thereby also decreasing refining efficiency of the blade 10.

[0061] Where bar openings 23 are provided in adjacent bars 20 such as shown in Fig. 4, they may be non-aligned so that they do not overlap or only partially overlap. This may be achieved by the bar openings 23 being offset from each other, either in their distance from the refining surface 15 on the upper end 21 of the bars 20 (i.e. from the bottom of the groove 30 between the refiner bars 20) or in the radial direction D, or both. Such non-aligned bar openings 23 are disclosed both in the planar view of Fig. 4 and in the perspective view of Fig. 3 where a plurality of bars 20 having bar openings 23 are shown. The bar openings 23 being offset or non-aligned means that the flow of lignocellulosic material and steam is unable to travel in a straight line through the bars 20 and instead forces the flow to seek other paths across the blade 10.

[0062] Preferably, at least half of the bars 20 comprise at least one bar opening 23, and this enables an efficient flow across the blade 10 when in use to refine lignocellulosic material.

[0063] Fig. 6 discloses the blade 10 with flow channels 24 that are formed by bar openings 23 distributed in the bars 20. In such flow channels 24, the bar openings 23 may be offset in height but aligned in the radial direction D or in a direction at an angle to the radial direction D to provide a suitable direction of flow. In Fig. 6, the flow channels 24 are distributed with a distance between them that may either comprise portions with bars 20 lacking bar openings 23 or with bars 20 having bar openings 23 that are not aligned so as to form flow channels 24.

[0064] Fig 7 discloses an embodiment of the blade 10 with flow channels 24 placed closer together to further increase the flow across the blade 10. Providing the bar openings 23 as flow channels 24 has the advantage of facilitating transport of steam and / or lignocellulosic material inside the flow channels 24 to improve its transport across the blade 10 from the inner periphery to the outer periphery. Suitably, at least some of the flow channels 24 are arranged at an angle to the radial direction D in a natural flow direction to further improve transport of steam and / or lignocellulosic material in the flow channels 24. The natural flow direction is a main flow direction across the blade 10 as the blade 10 rotates in the rotational direction R.

[0065] In some embodiments, bar openings 23 may be provided one on top of the other in the same bar 20, and suitably flow channels 24 through multiple bars 20 may also be provided one on top of the other so that they extend in parallel or at an angle to each other but at different heights. It is particularly advantageous to provide flow channels 24 closer to the outer periphery 14 where the risk of plugging of the grooves 30 is increased.

[0066] In some embodiments, the grooves 30 are provided with a smaller groove width gw closer to the outer periphery 14 but a larger groove width closer to the inner periphery 13. This allows for a higher density of bars 20 and thereby a larger cutting-edge length closer to the outer periphery. It also renders providing bar openings 23 close to the outer periphery 14 more advantageous in order to avoid blockage in the grooves 30 there.

[0067] The invention also encompasses a refiner comprising at least one blade 10 according to any embodiment of the invention. The blade 10 may be used as the rotor side blade or the stator side blade, or alternatively two blade 10 according to the invention may be used together, one of them being the rotor side blade and the other the stator side blade. Where the blade 10 has a central angle smaller than 360°, a plurality of blades 10 are combined to form the circular blade in the refiner. In some embodiments of the refiner, different embodiments of the invention may be used as the stator side blade and the rotor side blade.

[0068] Blades 10 with the narrow bars 20 disclosed herein are very difficult or even impossible to manufacture using known prior art manufacturing methods (typically casting in a sand mould, although other manufacturing methods are also known and used). The dimensions of the bars 20 that are achieved in the present invention are due to additive manufacturing that has not previously been used for blades 10 for refiners. Also, bar openings 23 such as disclosed above cannot be manufactured by casting but are instead formed by using the inventive manufacturing method set out below.

[0069] The method for manufacturing the blade according to the invention will now be described with reference to Fig. 8.

[0070] The method comprises providing 101 production data of the blade 10 according to any embodiment disclosed herein.

[0071] Generally, in the present disclosure, the production data may be provided in any suitable data type. Usually, 3D printable models may be created with a computer-aided design (CAD) package, via a 3D scanner, or by a plain digital camera and photogrammetry software. 3D printed models created with CAD result in reduced errors and can be corrected before printing, allowing verification in the design of the object before it is printed. Accordingly, CAD data are preferred in the present disclosure.

[0072] In one specific embodiment of the present disclosure, a 3D model of a refiner blade is produced with a CAD program package, where the 3D refiner blade model created by the CAD program is a mathematical representation stored in a first data file with a suitable file format, e.g. a STL file. Suitable CAD program packages are, for example, Pro / Engineer and SolidWorks. Optionally but preferably, the data on the first and second data files are checked for errors and imperfections with a suitable software program package, e.g. a program package provided by the company EOS e- manufacturing solutions. Besides correcting errors in the data files, it is important that all geometrical structures in the refiner blade models are reproducible in subsequent manufacturing steps and are suitable for such manufacturing steps. Depending on the geometrical structures incorporated in the refiner segments and on the specific 3D printer and 3D printer software chosen, the data contained in the data files is mathematically sliced into layers, which can have a virtual thickness of, e.g., 0.01 mm.

[0073] The method also comprises supplying 102 the production data to a 3D printer.

[0074] Generally, in the present disclosure, the printing step may be performed by any suitable 3D printer type. Preferred printing materials are selected from metals or metal alloys. The present invention is not limited to a specific printing material.

[0075] The method further comprises 3D printing 103 a pattern of the blade 10.

[0076] The mathematically sliced data files are thus input into a suitable 3D printer package and the refiner blade is printed using the 3D printer. Different 3D printing techniques can be employed, but a preferred technique is so-called direct metal laser sintering (DMLS), which utilizes an ytterbium (Yb) fiber laser fired into a bed of metal powder.

[0077] It is to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

Claims

CLAIMS1. Blade for a refiner for defibrating a lignocellulosic material, the blade (10) comprising a refining surface (40) having a plurality of bars (20) separated by grooves (30), wherein each bar (20) has a bar width (w) and a bar height (h), said bar height (h) being a height from a bottom of an adjacent groove (30) to an upper end of said bar (20), wherein at least one bar (20) of the blade (10) has a bar width (w) of 1.5 mm or less and a bar height (h) of at least 5 mm, and wherein further at least one groove (30) of the blade has a groove width (gw) of 1.5 mm or less, characterized by at least one of the bars (20) comprising a bar opening (23) that extends through the bar (20) from one groove (30) to an adjacent groove (30), said bar opening (23) being a through-hole through the bar (20).

2. Blade according to claim 1, wherein at least one bar (20) has a bar width (w) of less than 1 mm, preferably less than 0.7 mm and more preferably less than 0.5 mm.

3. Blade according to claim 1 or 2, wherein at least one bar (20) has a bar height (h) of at least 10 mm, preferably at least 15 mm and more preferably at least 20 mm.

4. Blade segment according to any previous claim, wherein at least one groove (30) has a groove width (gw) of 1 mm or less, preferably 0.7 mm or less and more preferably 0.5 mm or less.

5. Blade according to any previous claim, wherein the plurality of bars (20) have a mean bar width of 1.5 mm or less, a mean bar height of 5 mm or more, or the plurality of grooves (30) have a mean groove width of 1.5 mm or less.

6. Blade according any previous claim, wherein two adjacent bars (20) each comprise at least one bar opening (23), and wherein the bar opening (23) of one of the bars (20) is non-aligned with the bar opening (23) of the other bar (20).

7. Blade according to claim 6, wherein the bar openings (23) are non- aligned by being at different heights from the bottom of the groove (30) between the two bars (20) or at different positions in a radial direction (D).

8. Blade according to claim 6 or 7, wherein at least one of the bars (20) comprises a plurality of bar openings (23).

9. Blade according to any previous claim, wherein at least half of the bars (20) comprise at least one bar opening (23).

10. Blade according to any previous claim, wherein two adjacent bars (20) each comprise at least one bar opening (23), and wherein the bar opening (23) of one of the bars is aligned with the bar opening (23) of the other bar to form a flow channel (24).

11. Blade according to any previous claim, wherein the blade (10) forms a circular sector with a central angle of 10° - 360°.

12. Blade according to any previous claim, wherein the blade (10) is made by additive manufacturing.

13. Refiner comprising at least one blade (10) according to any of claims 1- 12.

14. Method for manufacturing the blade according to any of claims 1- 12, comprising:- providing production data of the blade (10),- supplying the production data to a 3D printer, and- 3D printing a pattern of the blade.

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