Method for Manufacturing of a Rotor

Abstract

A method for manufacturing a rotor includes the following operations: the clamping of a workpiece in a grinding machine; the performance of one or more cylindrical grinding operations whereby a rotor shaft section is ground to the desired diameter with a cylindrical grinding disk; the performance of one more profile grinding operations whereby a rotor body is profiled with a profile grinding disk. During the manufacture of the rotor in the grinding machine, the workpiece is not undamped and the cylindrical grinding operations and the profile grinding operations are done with the same grinding machine.

Claims

1. A method for manufacturing a screw rotor, the method comprising the steps of: providing a workpiece that has already been partially processed to have a shape of a rotor; clamping the workpiece in a grinding machine; performing grinding operations on the workpiece, wherein the grinding operations include performing a cylindrical grinding operation that includes cylindrical grinding of the workpiece with a cylindrical grinding disk, wherein one or more sections of the workpiece are ground to a desired diameter to form a rotor shaft section, and performing a profile grinding operation that includes profile grinding of the workpiece with a profile grinding disk, wherein a section of the workpiece is profiled to form a rotor body of the screw rotor; wherein the cylindrical grinding operation and the profile grinding operation are performed in the same grinding machine by switching with a switching mechanism between the cylindrical grinding operation and the profile grinding operation or between the profile grinding operation and the cylindrical grinding operation.

2. The method according to claim 1, wherein during the grinding operations, unclamping of the workpiece is not required when switching between the cylindrical grinding operation and the profile grinding operation or between the profile grinding operation and the cylindrical grinding operation.

3. The method according to claim 1, wherein performing the cylindrical grinding operation includes cylindrically grinding with the cylindrical grinding disk a first section on at least a first end of the workpiece to obtain a cylindrical clamping surface that is centered with respect to a centre line of the workpiece along the axis of the workpiece.

4. The method according to claim 3, wherein performing the grinding operations includes performing a second clamping by clamping the workpiece at the cylindrical clamping surface to provide rotational support to the workpiece during the profile grinding operation and controlling rotation of the workpiece about a longitudinal axis of the workpiece during the profile grinding operation.

5. The method according to claim 1, wherein performing the grinding operations includes supporting the workpiece in a direction perpendicular to a longitudinal axis of the workpiece with a stay that is supported on bearings or is a sliding stay, wherein the supporting of the workpiece includes supporting the workpiece by accommodating a force that occurs during the cylindrical grinding operation or the profile grinding operation so as to prevent or limit bending of the workpiece.

6. The method according to claim 1, wherein the cylindrical grinding operations include one or more different cylindrical grinding operations, and the profile grinding operations include one or more different profile grinding operations.

7. The method according to claim 1, further comprising a second clamping of the workpiece with a clamping system to a cylindrical clamping surface formed in a first section of the workpiece, wherein the cylindrical clamping surface is centered around a longitudinal axis of the workpiece.

8. The method according to claim 1, wherein the switching between the cylindrical grinding operation and the profile grinding operation with the switching system includes interchangeably switching between the cylindrical grinding disk and the profile grinding disk, wherein the cylindrical grinding disk is configured to be affixed and removed from a grinding spindle and the profile grinding disk is configured to be affixed and removed from said grinding spindle.

9. The method according to claim 1, wherein the switching between the cylindrical grinding operation and the profile grinding operation with the switching system includes removing the cylindrical grinding disk from the grinding spindle, and affixing the profile grinding disk to the grinding spindle.

10. The method according to claim 1, wherein clamping the workpiece includes making a centre hole in each of end of the workpiece, and clamping in a first clamping the workpiece in between two centre points of the grinding machine.

11. A grinding machine for manufacturing a screw rotor, the grinding machine comprising: a clamping system configured to clamp a workpiece that has already been partially processed to have a shape of a rotor; a grinding spindle; an interchangeable cylindrical grinding disk configured to be affixed and removed from the grinding spindle; an interchangeable profile grinding disk configured to be affixed and removed from the grinding spindle; a switching system configured to enable switching between grinding operations of the grinding machine, including switching between a cylindrical grinding operation with the cylindrical grinding disk and a profile grinding operation with the profile grinding disk; and a control system configured to automatically control the grinding operations to manufacture the rotor; and wherein the same grinding machine is configured to perform both the cylindrical grinding operation and the profile grinding operation by the control system controlling the switching system.

12. The grinding machine according to claim 11, wherein the grinding machine is configured such that unclamping of the workpiece is not required when switching between the cylindrical grinding operation and the profile grinding operation.

13. The grinding machine according to claim 11, wherein the control system controls the grinding machine such that the cylindrical grinding operation includes cylindrically grinding with the cylindrical grinding disk a first section on a first end of the workpiece to obtain a cylindrical clamping surface that is centered with respect to a centre line of the workpiece along the axis of the workpiece.

14. The grinding machine according to claim 13, wherein the clamping system is configured to perform a second clamping of the workpiece at the first end at the cylindrical clamping surface to provide rotational support to the workpiece during the profile grinding operation by controlling rotation of the workpiece about a longitudinal axis of the workpiece during the profile grinding operation.

15. The grinding machine according to claim 11, wherein the grinding machine further comprises a stay that supports the workpiece during the grinding operations in a direction perpendicular to a longitudinal axis of the workpiece, and wherein the stay supports the workpiece by accommodating a force that occurs during the cylindrical grinding operation or the profile grinding operation so as to prevent or limit bending of the workpiece.

16. The grinding machine according to claim 11, wherein the grinding machine is configured to perform one or more different cylindrical grinding operations or one or more different profile grinding operations through the control system controlling the switching system.

17. The grinding machine according to claim 11, wherein the clamping system is configured to perform a first clamping and a second clamping, the first clamping including an initial clamping of the workpiece, and the second clamping including clamping of the workpiece at a cylindrical clamping surface formed in a first section of the workpiece, wherein the grinding machine is configured to form the cylindrical clamping surface centered around a longitudinal axis of the workpiece.

18. The grinding machine according to claim 11, wherein the switching system is configured to switch between the cylindrical grinding operation and the profile grinding operation with the switching system configured to interchangeably switch between the cylindrical grinding disk and the profile grinding disk.

19. The grinding machine according to claim 11, wherein the switching system is configured to switch between the cylindrical grinding operation and the profile grinding operation by removing the cylindrical grinding disk from the grinding spindle, and affixing the profile grinding disk to the grinding spindle.

20. The grinding machine according to claim 11, further comprising a deburring brush, wherein the switching system enables the grinding machine to switch to an additional operating mode to debur the workpiece with the deburring brush.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0118] With the intention of better showing the characteristics of the invention, a preferred method and grinding machine according to the invention is described hereinafter by way of an example, without any limiting nature, with reference to the accompanying drawings, wherein:

[0119] FIG. 1 shows a side view of a rotor of a screw compressor;

[0120] FIG. 2 schematically illustrates a first cylindrical grinding operation, more specifically the oblique multiple insert grinding with a cylindrical grinding disk;

[0121] FIG. 3 schematically illustrates a top view of a cylindrical grinding operation, more specifically peel grinding with a cylindrical grinding disk;

[0122] FIGS. 4 and 5 show a cross-section of two possible profile grinding disks (intended for profile grinding a male and female rotor of a screw compressor respectively);

[0123] FIGS. 6 and 7 schematically illustrate the first two steps of a method according to the invention for manufacturing a rotor according to FIG. 1, whereby a cylindrical grinding operation is applied in these steps;

[0124] FIGS. 8 and 9 each schematically illustrate a front view of a next step of a method according to the invention to manufacture a male or female rotor of a screw compressor respectively, in which a coarse profile grinding operation is performed;

[0125] FIG. 10 illustrates a subsequent step of the method according to the invention in which a number of cylindrical grinding operations are done;

[0126] FIGS. 11 and 12 illustrate, analogous to FIGS. 8 and 9, the fine profile grinding of a male and female rotor for a screw compressor respectively;

[0127] FIG. 13 illustrates a last cylindrical grinding operation of the method;

[0128] FIGS. 14 and 15 show two possible embodiments of a grinding machine according to the invention; and

[0129] FIG. 16 schematically shows a side view of a set of flushports of the grinding machine.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0130] The rotor 1 shown in FIG. 1 is a male type rotor 1 for a screw compressor, that consists of a rotor shaft 2 on which there is a rotor body 3.

[0131] The rotor body 3 can be contained in a cylindrical body that has an outside diameter D.

[0132] The axial ends of the rotor body 3 are formed by two end faces 4 and 5, whereby upon assembly of the rotor 1 in the screw compressor, the end face 4 is specifically intended to be oriented towards an outlet side, while the end face 5 is intended to be oriented towards an inlet side of the compression chamber of the screw compressor.

[0133] As the rotor body 3 is intended for compressing or expanding air or another medium in a compressor, vacuum pump or expander, it also has spiral 6, whereby the teeth 7 are separated from one another by grooves 8.

[0134] The rotor shaft 2 consists of different sections with varying diameters, both on the inlet shaft side and on the outlet shaft side.

[0135] In the example shown, at one end of the rotor shaft 2 there is a suitable section 9 for driving the rotor shaft 2.

[0136] Moreover, on each side of the rotor body 3 there is a section for supporting the rotor shaft 2 while rotating with respect to a housing of a screw compressor by means of a bearing, sections 10 and 11 respectively.

[0137] In the example shown, adjacent to the section 10 for a bearing of the rotor shaft 2 there is a certain step to form an axial contact surface 12 that is perpendicular to the axis AA of the rotor 1, and which can act as an axial contact surface 12 for the bearing to be fitted.

[0138] Moreover, between sections 10 and 11 for the bearings and the rotor body 3, there is also a section for sealing the rotor 1 in the housing of the screw compressor, sections 13 and 14 respectively.

[0139] To clamp and centre the rotor shaft 2 in a grinding machine, there is a centre hole 17 centrally in both ends 15 and 16 of the rotor shaft 2.

[0140] It is clear that this complicated shape requires a multitude of different operations.

[0141] More specifically the different sections 10 to 14 of the rotor shaft 2, and the external diameter D of the rotor body 3, are obtained by performing a number of cylindrical grinding operations.

[0142] By way of an example, FIG. 2 illustrates such a cylindrical grinding operation, more specifically the multiple oblique insert grinding with a cylindrical grinding disk 18.

[0143] Such a cylindrical grinding disk 18 generally has an abrasive such as corundum or CBN (Cubic Boron Nitride) and has a typical cutting profile 19.

[0144] In the case of FIG. 2, the cutting profile 19 is such that when the cylindrical grinding disk 18 is obliquely inserted, a part of a shaft can be ground to a certain diameter and a radially oriented surface can be ground on this shaft at the same time.

[0145] In this case the workpiece is a shaft 20 that undergoes a rotary movement around its axis BB and in which the stepped cutting profile 19 of the cylindrical grinding disk 18 is copied a number of times by moving the cylindrical grinding disk 18, which in this example rotates around the oblique axis CC, towards the shaft 20 along the oblique direction DD during the insert grinding.

[0146] In this way the shaft 20 can be given a stepped profile.

[0147] Another form of cylindrical grinding shown in FIG. 3, more specifically a peel grinding operation whereby a part of a shaft 21 is ground to a certain diameter with a cylindrical grinding disk 18.

[0148] In contrast to what was the case with the insert grinding, when peel grinding the cylindrical grinding disk 18 only undergoes a small feed movement in the direction of the shaft 21, and the further peel grinding is done by moving the rotating cylindrical grinding disk 18 in the longitudinal direction EE parallel to the shaft direction FF.

[0149] To realise the end faces 4 and 5 of the rotor body 3, and possibly the contact surface 12 between the rotor shaft sections 10 and 13 (see FIG. 1), a grinding operation is required, for example by grinding with a grinding disk end on to the end faces 4 and 5 or the contact surface 12.

[0150] A cylindrical grinding disk 18 can also be used for this grinding operation, for example of the type as shown in FIG. 3, and hereinafter such a grinding operation shall also be considered as a cylindrical grinding operation.

[0151] To realise the spiral toothing 6 of the rotor body 3 another grinding operation is needed, i.e. a profile grinding operation using a profile grinding disk 23, a few examples of which are shown in FIGS. 4 and 5.

[0152] It is clear that these profile grinding disks 23 have a profile 24 that corresponds to the profile of the spiral grooves 8 of the rotor body 3.

[0153] Moreover, the grinding of the spiral toothing 6 requires a combined movement of the workpiece and the profile grinding disk 23 that is much more complicated than with cylindrical grinding.

[0154] According to the known methods, the cylindrical grinding and profile grinding are done on different grinding machines, which leads to a number of disadvantages, as set out in the introduction.

[0155] The steps that a method according to the invention preferably contains are set out below.

[0156] It is of great importance here that in such a method according to the invention, only one grinding machine is used and that the workpiece is not unclamped during the manufacture of the rotor 1.

[0157] FIG. 6 shows a first step of the method, whereby a workpiece 25, that has already been partially processed for example and more or less already has the shape of a rotor 1 as shown in FIG. 1, is clamped by clamping the workpiece 25 in between the two centre points 26 of the grinding machine 27.

[0158] After clamping the workpiece 25 between the two centre points 26, a first cylindrical grinding operation is preferably done with a cylindrical grinding disk 18 of the grinding machine 27, which consists of cylindrically grinding the section 10 at the end 15 of the workpiece 25, to obtain a cylindrical clamping surface 28 that is centred with respect to the centreline GG.

[0159] It is clear that for the good removal of the ground material and/or to obtain a certain cooling and lubrication of the workpiece 25 during grinding, it is best to use a flushport 29 or a set of flushports 28.

[0160] It can also be the intention to extinguish sparks that occur during grinding with such a flushport 29.

[0161] FIG. 16 shows a typical configuration in which a set of flushports 29 is used to cool, lubricate and clean the grinding disk 18 and the workpiece 25, and to extinguish sparks that occur during grinding.

[0162] The flushport 29 to provide cooling and lubrication is placed above the contact zone between the cylindrical grinding disk 18 and the workpiece 25.

[0163] This cooling port 29 for cooling and lubrication is oriented in the direction of rotation of the grinding disk to the aforementioned contact zone between the cylindrical grinding disk 18 and the workpiece 25.

[0164] The flushport 29 that is intended to extinguish sparks is oriented in a direction opposite to the direction of rotation of the cylindrical grinding disk 18 and towards the aforementioned contact zone between the workpiece 25 and the cylindrical grinding disk 18.

[0165] Finally there is a further flushport 29 for cleaning the cylindrical grinding disk 18 that is oriented to a part of the grinding disk 18 in a direction perpendicular to the surface of the grinding disk 18.

[0166] When turning the grinding disk 18, a part of the grinding disk 18 will first be cleaned at the flushport 29 concerned, after which this part comes into contact with the workpiece 25 whereby it is lubricated to reduce the development of heat, and whereby the heat released by the grinding is dissipated by cooling and any sparks that occur are extinguished with the flushports 29 concerned.

[0167] Of course the same set of flushports 29 can be provided during the profile grinding, and more or fewer flushports 29 can be used and/or configured differently.

[0168] In a subsequent step of the method according to the invention, shown in FIG. 7, the workpiece 25 is first additionally clamped with a clamping mechanism or clamping system 30, that moves towards the workpiece, of the grinding machine 27 that engages around the clamping surface 28 formed in the previous step.

[0169] Moreover, a section 11 at the other end 16 of the workpiece 25, for example a section 11 intended for fitting a bearing, but other components are not excluded, is cylindrically ground with a cylindrical grinding disk 18 of the grinding machine 27, either the same cylindrical grinding disk 18 or a different cylindrical grinding disk 18 than in the previous step, to form a cylindrical support surface 31 that is centred with respect to the centre line GG.

[0170] FIGS. 8 and 9 show a subsequent step of the method according to the invention, whereby a coarse profile grinding operation is performed to grind a first coarsely finished spiral toothing 6 of the rotor body 3, respectively for grinding a male rotor 1 and a female rotor 1 of a screw compressor.

[0171] To perform a profile grinding operation, the workpiece 25 has to be fully supported at the end 15, whereby it is driven during grinding.

[0172] To this end, the workpiece 25 is at least clamped between the centre points 26 and clamped in with a clamping mechanism or clamping system 30 at the end 15.

[0173] If desirable for stability, the other end 16 of the workpiece 25 is supported in a rotating way by means of a stay 32 supported on bearings or a sliding stay 32 that is fitted around the support surface 31 ground in the previous step.

[0174] In this way the workpiece 25 is sufficiently supported to accommodate the large forces that occur during the profile grinding and/or to prevent or limit the bending of the workpiece 25 during the profile grinding.

[0175] To perform the profile grinding operation, a profile grinding disk 23 of the grinding machine 27 is of course used.

[0176] It is important to note that, in contrast to what is the case in the known methods, here it is a profile grinding disk 23 of the same grinding machine 27.

[0177] The only difference between FIGS. 8 and 9 relates to the orientation of the profile grinding disk 23 in the grinding machine 27, which demonstrates that with the same grinding machine 27 both a female and male rotor 1 for compressors, blowers, vacuum pumps, or expanders, can be easily manufactured, just by changing the orientation of the profile grinding disk 23.

[0178] After this first coarse profile grinding operation to obtain a workpiece 25 with a coarsely ground rotor body 3, according to the invention, one or more interim cylindrical grinding operations are preferably performed, as illustrated in FIG. 10.

[0179] Such cylindrical grinding operations can consist of cylindrically grinding one or more rotor shaft sections, such as the fine cylindrical grinding of the sections 10 to 14 or the external diameter D of the rotor body 3.

[0180] In such interim cylindrical grinding operations, one or both end faces 4 and 5 of the rotor body 3 are finely ground.

[0181] For these interim grinding operations, a cylindrical grinding disk 18 of the grinding machine 27 is again used.

[0182] The advantages of performing these interim grinding operations primarily consist of the fact that the fine grinding of the parts concerned is only done after the profile of the rotor body 3 has already been ground into its rough shape, so that the negative effects of the coarse profile grinding, such as the accumulation of heat in the workpiece 25, deburring, and so on, can no longer affect the finish of the rotor 1.

[0183] According to a preferred method according to the invention, one of the steps consists of a deburring operation with the same grinding machine 27.

[0184] The large burrs can be deburred, for example, by cylindrical grinding the end faces 4 and 5 of the rotor body 3 and/or the outside diameter D of the rotor body 3.

[0185] In a subsequent step of the method, the spiral toothing 6 of the rotor body 3 can be finely ground using a profile grinding disk 23 with a fine grain and accurate profile.

[0186] This is shown in FIGS. 11 and 12, again for manufacturing a male and female rotor 1 respectively for a screw compressor.

[0187] In a subsequent step of the method, the finely ground spiral toothing 6 can be deburred, for example, by removing the fine burrs with a deburring brush 40.

[0188] Finally, in a last step of the method according to the invention, the clamping mechanism or clamping system 30 can be opened and pulled back and the supporting stay 32 removed, after which the clamping surface 28 can be finely ground in a last grinding operation by cylindrical grinding with a cylindrical grinding disk 18 of the grinding machine 27 to form a finely ground section 10 for fitting a bearing.

[0189] It is clear that in this way a rotor 1 can be manufactured without having to unclamp the workpiece 25, which brings about the intended advantages as set out in the introduction.

[0190] In summary it can be said that a method according to the invention preferably comprises the following steps whereby the following order of operations is preferably followed: [0191] the cylindrical grinding of a clamping surface 28 for a clamping mechanism or clamping system 30; [0192] the cylindrical grinding of a support surface 31 for a stay 32; [0193] the coarse profile grinding of the rotor body 3; [0194] the cylindrical grinding of one or both end faces 4 and 5 of the rotor body 3, whereby the large burrs on both surfaces are at least partially removed at the same time; [0195] the cylindrical grinding of the less critical shaft diameters of the rotor 1; [0196] the cylindrical grinding of the bearing surfaces 10 and 11; [0197] the cylindrical grinding of the outside diameter D of the rotor body 3, whereby the large burrs are at least partially removed at the same time; [0198] the fine profile grinding of the rotor body 3, the fine cylindrical grinding of the clamping surface 28 for the clamping mechanism or clamping system 30, or in other words the section 10 at the end of the rotor shaft 2.

[0199] Of course the application of another order of operations and/or the addition of operations and/or elimination of operations, are not excluded according to the invention.

[0200] According to a preferred method according to the invention the method is at least partially automated.

[0201] According to the invention use can be made of a grinding machine 27 to manufacture a rotor of a compressor, an example of which is shown in FIG. 14.

[0202] This grinding machine 27 has clamping means in the form of centre points 26 and a withdrawable clamping mechanism or clamping system 30 for clamping a workpiece 25, but they can just as well take on another form.

[0203] Moreover, the grinding machine 27 has one universal grinding spindle 33 and a number of exchangeable cylindrical grinding disks 18 and a number of exchangeable profile grinding disks 23, as well as a number of deburring brushes 40, that are contained in a magazine 34 of an automated exchanger 35 of the grinding machine 27.

[0204] There are also a number of exchangeable flushports 29 or a number of sets of exchangeable flushports 29 in the magazine 34 of the exchanger 35, that may or may not be exchanged at the same time with the grinding disk 18 or 23.

[0205] During the manufacture of a rotor 1, the tool exchanger 35 is intended to affix the exchangeable grinding disks 18 or 23, or the deburring brushes 40, from the magazine 34 to the universal grinding spindle 33 of the grinding machine 27 or vice versa.

[0206] In this way a method according to the invention can be applied whereby a grinding disk, either a cylindrical grinding disk 18 or a profile grinding disk 23, or a deburring brush 40, is removed from the universal grinding spindle 33 after performing an operation and another tool, either a cylindrical grinding disk 18, a profile grinding disk 23, or a deburring brush 40 is placed on this universal grinding spindle 33 to perform a subsequent grinding operation.

[0207] Preferably a flushport 29 or a set of flushports (for example, according to FIG. 16) is also exchanged between two grinding operations, or alternatively such a flushport 29 or set of flushports 29 can just be positioned differently.

[0208] Moreover, the grinding machine 27 has a control 36 for automatically performing grinding operations for the manufacture of the rotor 1.

[0209] FIG. 14 schematically presents this control 36, but such a control 36 can for example consist of a computerised system for controlling all types of motors 37 of the universal grinding spindle 33, or robot arms for moving grinding disks 18 and 23, and/or deburring brushes 40 and/or flushports 29 and so on.

[0210] To close, the grinding machine 27 also has switching means 38 that enable switching between at least two operating modes, more specifically between a first operating mode for grinding with a cylindrical grinding disk 18 and a second operating mode for grinding with a profile grinding disk 23, all such that the workpiece 25 does not have to be unclamped for the changeover between the possible operating modes.

[0211] The switching means 38 preferably enables the grinding machine 27 to switch to an additional operating mode for deburring a workpiece 25 with a deburring brush 40.

[0212] The switching means 38 and the tool exchanger 35 can again be realised in a thousand and one ways according to the arts of automation, and are preferably controlled by the control 36.

[0213] The grinding machine 27 also preferably has one or more positionable and/or exchangeable flushports 29 or set of flushports 29 that are also controlled by the control 36.

[0214] FIG. 15 shows another embodiment of a grinding machine 27.

[0215] This grinding machine 27 has one or more task-specific grinding spindles 39 that each have a specific grinding disk, either a cylindrical grinding disk 19 or a profile grinding disk 23, and an appropriate flushport set 29.

[0216] The grinding machine 27 also has one or more separate deburring brushes 40 that is or are placed on a deburring brush spindle 41 suitable for this purpose.

[0217] Moreover, this grinding machine 27 has a control 36 and switching means 38 for switching between the different operating modes, as in the previous case.

[0218] The intention here is that during the manufacture of a rotor 1, the control 36 controls a task-specific grinding spindle 39 or a deburring brush spindle 41 without a specific grinding disk 18, 23 or deburring brush 40 being exchanged on its task-specific grinding spindle 39 or deburring brush spindle 41 concerned.

[0219] In this way a method according to the invention can be realised in which a first grinding operation is performed using a first specific grinding disk 18 or 23 that is mounted beforehand on a first task-specific grinding spindle 39 of the grinding machine 27, and a second grinding operation is performed using a second specific grinding disk 18 or 23 that is mounted beforehand on a second task-specific grinding spindle 39 of the grinding machine 27 and/or a deburring operation is done using a deburring brush 40 that is mounted beforehand on a deburring brush spindle 41 of the grinding machine 27.

[0220] Preferably in such a method, both for the aforementioned first and second grinding operations, a flush is applied by making use of a first and second flushport or set of flushports 29 respectively, and these first and second flushports or set of flushports 29 are mounted on the grinding machine 27 beforehand such that a flush can be projected to the workpiece 25 in the vicinity of the first and second grinding disk 18 and/or 23 respectively.

[0221] It is clear that the ideas behind the embodiments of FIGS. 14 and 15 can be combined by combining one or more universal grinding spindles 33 with one or more task-specific grinding spindles 39 and/or deburring brush spindles 41 in one grinding machine 27.

[0222] The present invention is by no means limited to the method for manufacturing a screw rotor 1 of a compressor, a blower, a vacuum pump, or an expander, described as an example and illustrated in the drawings, but such a method according to the invention can be realised in all kinds of variants, without departing from the scope of the invention.