Patent Application
20210170531
The invention relates to a method for welding hard material bodies to teeth of a saw blade, in particular of a band saw blade or circular saw blade, each tooth having a joining surface, and each hard material body having a joining surface, and it being possible to weld the joining surface of the hard material body to the joining surface of the tooth, and the method comprising the following steps:
The invention also relates to a saw blade comprising teeth for welding hard material bodies thereto, and to a hard material body for welding to teeth of a saw blade.
In this case, a hard material body is understood to mean a body of any geometry, in particular a sphere, cylinder or plate shape, which is made of a hard material, in particular hard metal, cermet, cutting ceramic or diamond. The hard material body has, for example, a height of from 1 mm to 4.5 mm, preferably 1.5 mm to 3.5 mm, a width of from 1 mm to 6 mm, preferably 1.5 mm to 3.5 mm, and a length of from 2 mm to 6 mm, preferably 3 mm to 4.5 mm.
Methods for welding hard material bodies to teeth of saw blades are already known from the prior art. WO 2015/140345 A1 discloses a method of this kind, for example. It is usually desirable to weld the hard material bodies to the teeth of the saw blades with a high degree of accuracy. DE 10 2007 057 880 A1 also discloses a resistance-welded connection for cutting and grinding tools for connecting a cutting element of the tool to a carrier element. In the region of the connection zone, a plurality of protruding attachments are provided on the cutting element, which attachments are kept almost complete and unchanged when the cutting element is welded to the carrier element, such that the finished welded connection has an interlocking tooth-like course, in particular meandering course, in the joining direction.
The problem addressed by the invention is that of providing an improved method for welding hard material bodies to teeth of a saw blade.
According to the invention, at least one welding introduction attachment protruding from the joining surface is formed on each tooth, or at least one welding introduction attachment protruding from the joining surface of the hard material body is formed on each hard material body, the welding introduction attachment being melted upon introducing a welding pulse.
By providing the welding introduction attachment, when the hard material body is guided toward the tooth, an abutment over a small surface area, i.e. a punctiform or linear abutment, is produced between the tooth and the hard material body, which are thereby held apart from one another at a distance corresponding approximately to the height of the welding introduction attachment before being welded to one another, wherein, as a result of the small surface area of this abutment, a relatively high electrical contact resistance is produced which is favorable for the introduction of heat into the workpieces by means of introducing a welding pulse. During the welding pulse, the welding introduction attachment is melted more and more and thereby, in the region of the joining surfaces, fuses with the tooth and the hard material body pressed thereon.
The thickness of the weld connection and the resulting height of the tooth together with a hard material body welded thereto are therefore specified to a certain extent by the welding introduction attachment.
The welding introduction attachment is advantageously pointed-cone-shaped, hemispherical, semicylindrical, drop-shaped, pea-shaped or pyramidal, and protrudes from a relevant joining surface. The height or length of the welding introduction attachment is 0.02 mm to 2 mm, preferably 0.05 mm to 0.8 mm, in particular 0.1 mm to 0.8 mm, such that the welding introduction attachment protrudes from the joining surface by 0.02 mm to 2 mm, preferably 0.05 mm to 0.8 mm, in particular 0.1 mm to 0.8 mm. The width of the welding introduction attachment is, for example, 0.1 mm to 3 mm, preferably 0.4 mm to 2 mm.
It proves particularly advantageous if the welding introduction attachment is elongate, in particular obliquely or orthogonally with respect to the saw blade plane, so as to form a type of rib or projection. In this way, it can be formed economically on the teeth of the saw blade by arranging a plurality of saw blades parallel to one another and then machining them in a transverse direction.
It can prove to be advantageous that each tooth comprises a tooth face and the joining surface of the tooth is formed on the tooth face of the relevant tooth such that each hard material body is welded to the tooth face of the relevant tooth. In the teeth of the saw blade, the tooth face is formed on a front side of a relevant tooth in a cutting direction, with the cutting direction meaning the direction in which the saw blade is moved relative to a workpiece to be sawed during a sawing process. The face of a relevant tooth therefore contacts a workpiece to be cut first.
The space available on the tooth face for welding the hard material body thereto is limited both by the height of the teeth and by the distance to the tooth preceding in the cutting direction, and is often limiting. It can prove to be advantageous that each tooth comprises a tooth back and the joining surface is formed on the tooth back of the relevant tooth such that each hard material body is welded to the tooth back of the relevant tooth. The tooth back is formed on the rear side of the tooth facing away from the cutting direction. There is typically more space available here.
According to a further concept of the invention, it proves advantageous for each hard material body to be ground, in particular to its final shape, in a step preceding the welding process. This can be done by the manufacturer or supplier of the hard material body.
In this case, grinding to its final shape is understood to mean that a desired cutting geometry, for example a cutting edge, is formed on the hard material body, such that no further grinding process is subsequently necessary after the welding process. Furthermore, with different types of saw blades it may sometimes be necessary to design individual teeth of a saw blade differently in a targeted manner. In this case, the final shapes of different hard material bodies can differ from one another. For example, saw blades comprising so-called pre-cutting and post-cutting geometry include teeth which have cutting edges of different widths, which are joined alternately one behind the other in the case of successive teeth.
In order to improve the cutting and/or sliding properties, it can prove to be advantageous for the hard material body to be coated in a further step preceding the welding process. The coating comprises, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN) or aluminum oxide (Al2O3). The coating can be carried out in a PVD or CVD process. In particular, it can prove to be advantageous that the hard material body is only partially coated, with no coating being provided in particular on the joining surface.
It can also prove advantageous that guiding each hard material body toward the tooth located in the working region comprises supplying and transferring the relevant hard material body onto the welding device by means of a supply device, in particular comprising a robot gripping device. The welding device, together with the hard material body transferred thereto, can then be advanced into the working region and guided toward the tooth located there.
In a further development of this concept of the invention in particular, it proves advantageous if the hard material bodies are provided in such a way that they can be easily gripped by means of the robot gripping device. For example, it is conceivable to hold the hard material bodies in line next to one another and/or stacked, for example in the manner of a matrix, in particular aligned depending on their geometry. In particular, it may be suitable to hold the hard material bodies in a magazine or in a blister.
In so doing, it is possible, for example, to grip hard material bodies that have already been ground in a certain orientation and to transfer said bodies to the welding device.
The invention also relates to a saw blade, in particular a band saw blade or circular saw blade, comprising teeth having a joining surface for welding hard material bodies thereto, at least one welding introduction attachment which protrudes from the relevant joining surface being formed on each tooth.
Each welding introduction attachment is advantageously pointed-cone-shaped, hemispherical, semicylindrical, drop-shaped, pea-shaped or pyramidal, and protrudes from a relevant joining surface.
It proves particularly advantageous that each welding introduction attachment is elongate, in particular obliquely or orthogonally with respect to the saw blade plane, so as to form a type of rib or projection.
The invention also relates to a hard material body for welding to teeth of a saw blade, having a joining surface, at least one welding introduction attachment which protrudes from the joining surface being formed.
Further advantages, features and details of the invention can be found in the dependent claims and in the following description, in which a preferred embodiment is described in detail with reference to the drawings. The features shown in the drawings and mentioned in the claims and in the description may in each case be essential to the invention individually or in any desired combination. In the drawings:
The hard material bodies 4 are welded to the teeth 6 of the saw blade 8 in a working region 10 of the apparatus 2. For this purpose, the saw blade 8 is moved in a feed direction 14 by means of a saw blade feed device 12, such that a relevant intended tooth 6a of the saw blade 8 can be brought into the working region 10 of the apparatus 2. According to the embodiment shown, the saw blade feed device 12 comprises gripping or clamping devices 18 for grasping the saw blade 8 that are mounted on feed carriages 20. The feed carriages 20 can be moved, for example by means of a drive, in the direction of the double arrow 22 in parallel with the feed direction 14. The drive is preferably an electric linear drive. Moving the saw blade 8 in the feed direction 14 is understood to mean a translatory movement in the case of a band saw blade and naturally at least also a rotary movement in the case of a circular saw blade.
According to the embodiment shown, a welding device of the apparatus 2 for joining the hard material bodies 4 to the teeth 6 of the saw blade 8 is as a resistance welding device 24 comprising a welding electrode 26 that can be advanced into the working region 10 and withdrawn again out of the working region 10, such that the hard material bodies 4 are joined to the tooth backs 100 of the teeth 6 of the saw blade 8 by means of resistance welding.
By means of a supply device 28, each hard material body 4 is supplied to the welding electrode 26 and transferred thereto. The structure and the mode of operation of the supply device 28 are explained in the following with reference to
The apparatus 2 according to the embodiment shown also comprises a first centering device 30 for centering the saw blade 8 transversely to the feed direction 14 before the welding process, and a second centering device 32 for centering each hard material body 4 transversely to the feed direction 14 before said body is welded to the relevant intended tooth 6a of the saw blade 8 located in the target position. The first and second centering devices 30, 32 can be formed by any actuating elements. Furthermore, the centering devices 30, 32 can each comprise a gripper arrangement comprising first gripper jaws which can be moved toward or away from one another transversely or obliquely with respect to the feed direction. The mode of operation and the structure of the first and second centering devices 30, 32 will not be discussed further at this point.
After the welding process has ended, the saw blade 8 is moved further in the feed direction 14 by means of the saw blade feed device 12, such that a subsequent tooth 6b can be brought into the target position.
In the following, the structure and mode of operation of the supply device 28 will now be explained with reference to
The hard material body has, for example, a height H of from 1 mm to 4.5 mm, preferably 1.5 mm to 3.5 mm, a width of from 1 mm to 6 mm, preferably 1.5 mm to 3.5 mm, and a length L of from 2 mm to 6 mm, preferably 3 mm to 4.5 mm, the width of the hard material body according to the embodiment shown in
According to the embodiments shown, the teeth 6 are aligned in the cutting direction 102, i.e. tips 104 of the teeth 6 point in the direction in which the saw blade 8 is to be moved relative to a workpiece (not shown) during the sawing process. The tooth back 100 is formed on the rear side 108 of the tooth 6 facing away from the cutting direction 102, a tooth face 110 being formed on the front side 112 of the tooth 6 in the cutting direction 102.
According to the embodiments shown in
According to
Due to the geometry of the welding introduction attachment 120, when the hard material body 4 is guided toward the tooth 6, an abutment over a small surface area, i.e. a punctiform or linear abutment, is produced between the tooth 6 and the hard material body 4, which are thereby held apart from one another at a distance corresponding approximately to the height of the welding introduction attachment 120 before being welded to one another, wherein, as a result of the small surface area of this abutment, a relatively high electrical contact resistance is produced which is favorable for the introduction of heat into the tooth 6 and hard material body 4 by means of introducing a welding pulse. During the welding pulse, the welding introduction attachment 120 is melted more and more and thereby, in the region of the joining surfaces 116, 118, fuses with the hard material body 4.
In principle, more than one welding introduction attachment 120 protruding from the joining surface 116 can also be formed on each tooth 6.
According to the embodiments shown in
Finally,
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 120 242.3 | Aug 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/071911 | 8/15/2019 | WO | 00 |
