Title of Invention: A Program-controlled System of a Slotting Tool and a Lathe Machine for Forming an Internal Spiral Grooving

Technical Field

[0001] The invention relates to a program-controlled system of a slotting tool and a lathe machine for forming of an internal spiral grooving, a method of slotting such a groove, a program for controlling the lathe machine and performing the method, a control system of the lathe machine with instructions for performing the method, and, furthermore, improved slotting tools.

Background Art

[0002] Many workpieces with an internal cylinder-shaped cavity require formation of internal spiral grooving in the wall of the cavity. In the current state of the art, internal spiral grooves of the workpieces are formed by removing part of the mass by sharp cutting tools fixed in CNC machines by continuous rotary cutting movement in the initial direction, the so-called lathing, and when the workpiece or the cutting tool is moved simultaneously, the spiral groove is formed.

[0003] For slotting a direct groove, slotting machines that perform a straight movement back and forth are used, and in the current state of the art, for workpieces with a cylinder-shaped cavity, they are used only for formation of longitudinal grooves, using structurally different slotting tools, for example to produce internal and external toothing. Because of the way in which the movement is performed, the slotting machine as well as the slotting tool have so far been used to form indirect grooves only with the use of a slide.

[0004] Lathe and machine tools or workpieces are cooled by a stream of water because a considerable heat is generated during machining, which negatively affects the service life of the workpieces and cutting parts of the tools.

[0005] Cutting tools, e.g., lathe tools, as well as slotting tools/knives have a carrier/holder/body and a functional part/head associated therewith provided with a cutting edge. The difference between lathe knives and slotting tools is that a lathe tool has a bed for a cutting plate embedded into the functional part in the form of a special shape recess, into which the cutting plate is inserted and fixed, from which the cutting edge protrudes in the shape of the desired profile of the shape of the groove. Therefore, the whole cutting plate can usually be replaced in the lathe tools. Cutting plates perform different movement and face different types of stress/pressure, therefore, there are different requirements and structural differences in the fixation to the functional part than in the case of slotting tools, which face mainly impacts.

[0006] As an example, the Czech patent no. 306972 describes a cutting tool composed of a carrier, a cutting plate with a cutting edge protruding therefrom, and, furthermore, at least one additional source of force effect presented by a hydraulic piston.

[0007] The Polish patent PL2125278T3 describes a slotting tool for slotting direct grooves in the internal openings of workpieces, however, the mentioned solution is aimed at increasing the rigidity by a special plate placement in the axis of the tool.

[0008] The Chinese patent CN106141180B describes a method of production of a machine tool, such as rotary end mills or drill bits, using an additive technology, sintering, and then coating by PVD/CVD, or physical vapour deposition I chemical vapour deposition methods with formation of a lightweight internal structure that is beneficial to high-speed rotary tools.

[0009] The patent application US20200282475A1 describes a cooling system for a rotary tool by means of a specially designed shape of cooling channels for increasing the flow rate of a cooling liquid that runs unconventionally through the body of the tool all the way to the cutting point, however, the direction of the process liquid supply is not further described.

[0010] The patent document US20200222990A1 describes a boring bar, with a damping effect, which can be used for lathing or boring holes. The principle of the damping effect of the boring bar is the internal structure of the body of the bar, where the document describes several possible fillings of the body of the bar which can have damping effects in the machining process. The interspace of the lattice structure is further filled with an elastomer, which provides the damping effect.

Summary of Invention

[0011 ] An alternative method of forming spiral grooves in a workpiece is solved by the new use of a slotting tool with a cutting edge plate in a program-controlled lathe machine, for example spiral grooves of the desired profile shape in the workpiece cavity.

[0012] The object of the invention is a program-controlled system of a slotting tool and a lathe machine with a rotary spindle for clamping a workpiece, with a machine tool holder, most often an existing turret head can be used as the holder, and with a control system of the lathe machine programmable for slotting internal spiral grooving in a cavity of the workpiece, with a predefined helix pitch, number of grooves, and length of grooving, direction of helix winding, and with programmed gradual mutual approaching of the machine tool towards the rotary spindle with simultaneous rotation of the workpiece, where the essence of the invention is that the slotting tool with a cutting edge plate for forming the groove according to the desired profile shape is fixed in the machine tool holder by its clamping part, and the control system of the lathe machine is also programmed for a repeated straight forward cutting and reverse non-cutting back and forth movement of the slotting tool in the direction of the longitudinal axis axially to the workpiece, the so-called C-axis, the definition of which is known in the art of lathe machines. Forward and backward movement back and forth is performed in such a way that in the forward direction the cutting edge plate is engaged and material is removed from the workpiece wall to form the groove, while the reverse movement takes place without engaging the cutting edge plate into the workpiece wall, i.e. idly. A detailed description of said movements is provided below in an exemplary embodiment.

[0013] For slotting the spiral grooves of a specified profile, it is advisable to use a machine that can efficiently synergistically control the linear movement of the tool with the rotary movement of the workpiece. The CNC lathe or program-controlled lathe machine with controlled C-axis meets these requirements and is able to provide the desired repeatable accuracy for mass production, therefore, it is used to form a thread with a large pitch, by slotting a spiral groove in the internal cavity of the workpiece of the present invention, for example for left-handed grooving. Slotting on the CNC lathe enables production of spiral grooving with the possibility of selecting the desired pitch of the grooves, number of grooves, length of the grooving, direction of winding of the spiral groove, and other technological parameters using specially adapted programs of the control system of the lathe machine specially adapted for this purpose. This is an advantage over using a slotting machine that does not allow this programmable adjustment. The structural design of the tool is adapted to suit the specific production technology, for example, the size, shape, and orientation of the slotting tool are adapted to the given pitch of the groove of the workpiece and so that no undesirable contact and collision of any part of the slotting tool with the workpiece occurs during the production of the grooving.

[0014] To perform this method, a program for the control system of the CNC lathe machine has been specially developed that is imported into the control system of the lathe machine, on the basis of which the control of the entire production process takes place.

[0015] A workpiece with an internal cavity is mainly defined by geometric requirements: diameters of the head, pitch, and heel circle of the grooving, length of the grooving, left-handed or right-handed orientation of the spiral winding in the cavity of the workpiece, etc.

[0016] The clamping part of the slotting tool can be adapted for clamping in the holder of the CNC lathe, for example by means of the so-called Weldon clamping system.

[0017] The control system of the CNC lathe machine is therefore programmed for different movements characteristic of the slotting process compared to conventional lathing, i.e., not for the conventional cutting of material by continuous draw in the initial direction, but for repeated forward cutting and backward non-cutting movements, but to form the spiral groove the slotting tool is also gradually moved in the longitudinal direction towards the clamping end of the workpiece. The solution of the invention uses in the CNC lathe a slotting tool, not boring bars or conventional lathe tools such as, for example, lathe tools. The slotting tool is dimensioned quite differently for the expected different load in the process of slotting and lathing of the thread by conventional methods is not possible with regard to too large helix pitch.

[0018] Another object of the invention is a slotting tool that comprises a clamping part and a functional part, wherein the functional part comprises a body and a cutting edge plate with a face and a back, wherein this slotting tool is special in that at least a part of the body of the functional part and/or the clamping part has a Gyroid-type lightweight lattice structure with hollow interspaces. This slotting tool as well as its detailed embodiments described below can be used in the system of the lathe machine described above.

[0019] The lightweight structure is not primarily aimed at increasing the rigidity or strength of the body of the slotting tool in the present invention but is provided to reduce vibrations in a particular machining direction, nevertheless, the rigidity is maintained the same as if the slotting tool were made of solid material.

[0020] The solution of the invention uses a special internal lattice structure, the so- called Gyroid-type lattice, without filling the interspaces of the lattice with additional filling material. These interspaces therefore remain hollow and thus provide lightweighting. Thanks to the lightweight internal structure, the tool absorbs shocks and vibrations generated during the slotting process due to the forces of the cutting process.

[0021 ] The Gyroid-type lightweight lattice structure can be produced by using the Power Bed Fusion 3D additive technology, specifically the Selective Laser Melting technology, without supporting elements, where all the printing elements of the lattice structure form an angle between 45° and 135° with the printing bed with respect to the printing bed. The Gyroid-type lightweight lattice structure is therefore designed such that no supporting elements need to be formed between the individual cells during production using the Power Bed Fusion 3D additive technology, namely the SLM, or Selective Laser Melting, technology, i.e. the structure complies with the rule that it does not contain elements that form an angle of less than 45° with the printing bed, i.e. the angle of all printing elements of the lattice structure relative to the printing bed must be in the range of 45° to 135°. By the supporting elements are meant such elements which must be formed when printing overhangs, bridges, or surfaces that have an angle of less than 45° to support the wall of the printed product or printed element such that the element and the entire printing structure do not collapse. Therefore, this means that if the printing plan of the slotting tool by 3D printing comprised orienting the slotting tool in the wrong position, the supporting elements would have to be inserted during printing. The Gyroid-type structure is preferred because it leads to the formation of structures of maximum area per unit volume with minimum cross-section of the printing material, which is desirable in printing both from the economic point of view and from the point of view of maximum lightweighting of the material while maintaining its sufficient strength. Said structure exhibits the same mechanical properties in all directions, which is very desirable for a slotting tool.

[0022] The dimensions of the cell of the lightweight lattice structure can be purposefully planned, in particular the cell thickness and height adjustments can be selected, and the slotting tool can be produced in different modifications of the lattice structure.

[0023] The lattice structure preferably has a cell dimension size of 25 to 35 mm, most preferably 20 mm.

[0024] Maintaining the same rigidity as if the tool were made of solid material is achieved primarily by the appropriate choice of wall thickness of 2.5 to 4 mm, preferably 3 mm, where this wall surrounds a core composed of a lightweight lattice structure. This core may extend inside the functional part and/or the clamping part of the slotting tool. By the wall is meant the shell case of the body of the tool around the core made of a Gyroid-type lightweight lattice structure, in which cooling channels can lead, see below. The wall has a solid structure, not a lattice one, so it can be composed of a commonly used material and a solid structure as used for common lathe tools.

[0025] Another object of the invention is a slotting tool in which an internal channel suitable for the supply of a process liquid, that is, for example a process liquid, for example a cooling liquid, but also suitable for lubricant and/or chip evacuation, passes through at least the functional part thereof and preferably also the clamping part, wherein this channel is bifurcated into two outlets, wherein one outlet is directed to the face of the cutting edge plate and one outlet is directed to the back of the cutting edge plate. Such a slotting tool, including the possible detailed improvements described below, can be used in the program-controlled system of the lathe machine mentioned above. Such a slotting tool, possibly including the above-mentioned detailed improvements, may have the Gyroid-type lightweight lattice structure mentioned above, most preferably, such a machine tool is then used in the program-controlled system of the lathe machine mentioned above.

[0026] Directing the channels not only to the face but also to the back of the replaceable cutting edge plate increases the cooling effect, which significantly increases the durability of the cutting edge plate and its protection during slotting, as it is undesirable to change the cutting edge plate during the grooving of one piece of workpiece or numerous changes during mass production. The embodiment of the invention thus increases the efficiency of the process and also reduces the overall cost. Said channel thus bifurcates and is terminated by two different process liquid supply directions to opposite surfaces of the cutting edge plate. Said solution reduces the wear of the cutting edge plate and contributes to achieving an optimal machining process, thus reducing the overall economic costs of the slotting process.

[0027] Preferably, at least one of the above-mentioned channel outlets is provided with a means for adjustable spray direction of the process liquid. The means for adjustable spray direction is preferably provided with an outlet facing the face of the cutting edge plate, wherein this means with adjustable spray direction of the process liquid comprises a nozzle in the form of a built-in housing with a ball recess and with an opening for the supply of the process liquid, and with a threaded opening for the nozzle screw, wherein a ball of a diameter smaller than that of the ball recess is disposed in this ball recess of the housing, provided with a through hole for the passage of the process liquid, where the housing is further provided with a circular opening to allow the liquid to exit from the through hole of the ball that is smaller than the diameter of the ball such that the ball is retained in the housing and fits tightly to the circumference of the opening such that the liquid flows out of the housing only through the through hole in the ball and not around the ball. The direction in which the process liquid exits from the through hole can be changed by positioning the ball via the nozzle screw, wherein the ball can be pressed by the nozzle screw and the through hole thus adjusted in a certain desired direction. The nozzle screw secures the ball in the desired position, allowing the direction of the liquid flow to be effectively changed to the face of the replaceable cutting edge plate. The circular opening in the housing for the exit of the liquid is therefore large enough to allow the process liquid to exit at different orientations of the ball with the through hole. The slotting tools in the prior art have only a fixed direction of the process liquid flow, which may be sufficient for slotting linear grooves but has been more effectively solved herein in the present invention in the case of spiral grooves. When slotting a helix-shaped groove, an adjustable direction of the process liquid supply is highly preferable.

[0028] By turning the ball, the direction of the liquid flow to the face of the replaceable cutting edge plate can be effectively changed. The second outlet facing to the back of the cutting edge plate may have a constant, fixed spray direction of the liquid and to the internal diameter of the workpiece, wherein it may also direct the process liquid to the machined surface of the workpiece where further spray of the process liquid occurs.

[0029] The channel may have a non-constant, i.e., variable diameter, preferably in the direction of the flow of the process liquid, for example cooling liquid, the entrance part of the channel has a larger diameter than the exit part of the channel, in this way the pressure can preferably be increased at the exit. The exit part of the channel is closer to the process liquid exit, the entrance part of the channel is closer to the entrance of the process liquid into the channel.

[0030] Preferably, the functional part of the slotting tool comprises a bed into which the cutting edge plate, which is replaceable, for example, clamped by a screw of the cutting edge plate, can be removably attached. By replacing the special replaceable cutting edge plate, the formation of a different desired groove profile can be achieved.

[0031] Another object of the invention is a method of slotting a groove to form a spiral grooving in the cavity of the workpiece, where the workpiece fixed on a rotary spindle of the program-controlled lathe machine rotates while the holder of the program-controlled lathe machine gradually approaches the spindle, where the essence of the invention is that the slotting tool with the cutting edge plate fixed in said holder repeatedly performs a forward main cutting movement forth and a non-cutting movement back such that the cutting edge plate drives material out of the internal wall surrounding the cavity of the workpiece to form the spiral groove in said wall. Preferably, this method uses a slotting tool having the Gyroid-type lightweight lattice structure with hollow interspaces mentioned above.

[0032] Further objects of the invention include a program for controlling the lathe machine and the performance of the above method comprising instructions for performing the method for the control system of the lathe machine comprising the program with instructions for performing the method.

Brief Description of Drawings

[0033] The summary of the invention will be explained by means of drawings, in which:

Fig. 1

[0034] shows an exploded view of the slotting tool of the invention.

Fig. 2

[0035] shows the internal layout of the slotting tool with the arrangement of the channel bifurcated into two outlets facing the face and back of the cutting edge plate.

Fig. 3

[0036] shows a section through the slotting tool already shown in Fig. 2 and a channel leading to the face of the cutting edge plate.

Fig. 4

[0037] shows a section through the slotting tool already shown in Fig. 2 and a channel leading to the back of the cutting edge plate.

Fig. 5

[0038] shows a Gyroid-type lattice structure.

Description of Embodiments

[0039] An example of an embodiment is a program-controlled system of a slotting tool and a lathe machine, i.e., a CNC machine with a rotary spindle in which a workpiece is clamped, which rotates around the axis of the spindle during the machining of a groove. This workpiece has a cavity in which a left-handed spiral groove is driven out by machining. In the holder of the CNC machine, specifically in the turret head of an existing CNC machine, a slotting tool with a cutting edge plate 8 is fixed by its clamping part 1 to form a groove according to the desired profile shape. In addition to the rotation of the workpiece, the holder with the slotting tool gradually approaches the rotating spindle during the slotting process, allowing the formation of a spiral instead of circular groove. Furthermore, during machining, the machine tool performs a straight forward and reverse movement back and forth in the z-axis direction, i.e. the longitudinal axis axially to the workpiece, such that a groove is formed on the internal wall of the cavity of the workpiece by contact and movement of the cutting edge plate 8.

[0040] The coordinate system of machine tools is well known in the art. The so-called main, i.e., cutting movement in the direction of the Z-axis is performed within the repeated straight forward and reverse movement of the slotting tool back and forth in the direction of the longitudinal axis axially to the workpiece. The secondary, i.e., movement of rotating the workpiece in the direction of the C-axis, i.e., rotating around the Z-axis, is performed by the workpiece. The detailed performance of these movements is described as follows. The shift into the cut, i.e., the adjustment of the depth of the cut, is in the X-axis direction. A groove is gradually formed in small depths of the cut, e.g., in 10 strokes/passes, in the X- axis direction to a final groove depth corresponding to the heel diameter of the grooving. The cutting movement is performed in the direction of the Z-axis toward the spindle of the machine. At the end of the groove, the tool moves out of the cut by the rapid traverse in the X-axis direction, i.e., to the centre of rotation of the workpiece, then the tool is moved by the rapid traverse in the Z-axis direction from the spindle back to the start of the cut, followed by another movement by the rapid traverse in the X-axis direction into the cut, which is actually adjustment of the next depth of the cut. During these three rapid movements by the rapid traverse, the workpiece is not rotated, and the tool does not cut. This is again followed by a cutting movement in the direction of the Z-axis toward the spindle.

[0041] All three types of movements have to be coordinated according to the desired parameters and are programmed in the control system of the lathe machine, i.e., CNC machine, such that the predefined parameters of the slotted groove in the workpiece, such as, for example, the pitch of the spiral, the number of grooves, and the length of the grooving, the direction of the spiral winding, are met.

[0042] The use of the slotting tool for forming of the internal spiral grooving is as follows: The slotting tool performs a straight-line reversible movement. The workpiece then performs a rotary movement. Therefore, all the movements are linked and mutually coordinated and adjusted according to the desired result. By using the programmable control system of the lathe machine with a controlled C- axis, the desired grooving pitch and the desired number of internal spiral grooves can be formed thanks to the special structure of the tool and a specially developed NC program for controlling the lathe centre with the controlled C-axis. The slotting tool is adapted to the given pitch of the groove so that there is no unwanted contact of the functional part 2 with the workpiece and no collisions.

[0043] For example, a slotting of the internal left-handed grooving with the following parameters was performed: diameter of the head circle - 170 mm, diameter of the heel circle - 177 mm, pitch - 500 mm, number of grooves - 35, length of the grooving - 80 mm, speed of the main cutting movement in the Z-axis - 5,000 mm/min, the speed of rotating the workpiece is exactly determined by calculation according to the pitch of the grooving, length of the grooving, and cutting speed in the Z-axis. The shape and size of the groove profile, i.e., in the section in the normal plane: width - 5 mm, with radii in the corners, side of the groove according to the curve of the widening groove.

[0044] This exemplary embodiment has been performed in an alternative with a conventional slotting tool, with a tool with a Gyroid-type lightweight structure 6, see details below, with a tool having a special cooling channel 7 and with a method of directing the spray, see below, and with a slotting tool with said lightweight structure 6 and also said cooling channel 7.

[0045] The slotting tool with the Gyroid-type lightweight structure 6 with hollow interspaces, shown in Fig. 5, has a clamping part 1 and a functional part 2, which are shown in Fig. 1 , wherein on the functional part 2 of the body, a replaceable cutting edge plate 8 with a face and a back, which is preselected according to the desired shape of the groove profile, is fixed into the bed 3 by means of a screw 9 of the cutting edge plate.

[0046] The clamping part 1 of the slotting tool is best suited for clamping in a holder, in this exemplary embodiment, in a turret head of an existing CNC lathe using the so-called Weldon element.

[0047] The Gyroid-type lightweight lattice structure 6 of the slotting tool was produced by the Power Bed Fusion 3D additive technology, specifically the Selective Laser Melting technology, wherein this technology was applied in such a way that it was not necessary to use supporting elements, therefore all printing elements of said lattice structure 6 were built in such a way that relative to the printing bed, they formed an angle between 45° and 135° with the printing bed. For example, some formed an angle of 90° and others of 60°. In particular, lattice structures with a cell with dimensions of 20x20x20mm were formed in several series, but slotting tools with a cell of the lattice structure of 35x25x20mm or 25x25x20mm were also tested. The material used for production of this structure was maraging steel with the designation M300 (1 .2709). However, other materials can also be used, for example stainless steel with the designation 316L (1.4404).

[0048] In order to increase the strength of the slotting tool, this lightweight structure was further used in an exemplary solution in which it formed only the internal part of the slotting tool, the so-called core, and this was surrounded by a wall that was 3 mm thick and was formed by a solid material, rather than lattice, structure of the same material as the “core”, namely M300. Alternatively, the entire wall was mostly 4 mm thick, but only 2.5 mm thick in some of the narrowest areas.

[0049] A slotting tool with an internal channel 7, whether used in a slotting tool with a solid or the above mentioned Gyroid-type lattice structure 6, has channels 7 arranged as follows:

[0050] Through the functional part 2 and the clamping part 1 of the slotting tool passes an internal channel 7 for a process liquid, in particular cooling liquid, but it can also be used for a lubricant and/or chip evacuation, where this channel 7 is bifurcated into two outlets 4, 5, wherein one outlet 4 faces the face of the cutting edge plate 8, and one outlet 5 faces the back of the cutting edge plate 8, see Fig. 2, Fig. 3 and Fig. 4, in which it can also be seen that the channel 7 has a variable, non-constant diameter. In this exemplary embodiment, the main channel 7 has an internal diameter of 8 mm and the two secondary channels 7 leading from it after the bifurcation have a diameter of 3 mm each.

[0051] In an improved exemplary embodiment, the outlet 4 facing the face of the cutting edge plate 8 has an adjustable spray direction, which is implemented by including a nozzle in the form of a built-in housing with a ball recess and with an opening for the supply of the process liquid, and a threaded opening for the nozzle screw 11 , wherein in this ball recess of the housing, a ball 10 with a diameter smaller than that of the ball recess is disposed, provided with a through hole for the passage of the process liquid, where the housing is further provided with a circular opening to allow the liquid to exit from the through hole of the ball 10 that is smaller than the diameter of the ball 10, the ball 10 tightly fitting to the circumference of this circular opening, where the position of the through hole can be positioned relative to the opening for the drainage of the liquid via the nozzle screw 11 , wherein the circular opening in the housing for the exit of the liquid is large enough to allow the process liquid to exit in multiple directions of orientation of the through hole, see Fig. 1 .

Industrial Applicability

[0052] An example of practical use is the production of special spiral internal grooving of workpieces that can be used as components of hydraulic rotary actuators that convert linear movement into rotary movement.

Reference Signs List

[0053] 1 - clamping part

[0054] 2 - functional part

[0055] 3 - bed

[0056] 4 - outlet facing the face of the cutting edge plate

[0057] 5 - outlet facing the back of the cutting edge plate

[0058] 6 - gyroid-type lightweight lattice structure

[0059] 7 - channel [0060] 8 - cutting edge plate

[0061] 9 - screw of the cutting edge plate

[0062] 10 - ball

[0063] 11 - nozzle screw