METHODS OF USE

[0001] The present disclosure relates to a flying saw for cutting extruded profiles with a cutting speed control using the temperature of the cutting edge of the saw blade of the flying saw, a method for controlling a cutting speed of a flying saw for cutting extruded profiles using the temperature of the cutting edge of the saw blade of the flying saw, and an extrusion apparatus for manufacturing extruded profile cuts comprising such a flying saw, all of them especially suitable for cutting extruded plastic or plastic/metal compound profiles for windows, doors and fa- cade elements.

[0002] Many types of windows, doors and facade elements for buildings include insulating profile elements like insulating connector strips connecting metal profiles on the weather side and metal profiles on the indoor side of the windows, doors and facade elements or insulating spacer profiles used in insulating glass units (IGUs). Such insulating profile elements are usually made from extruded plastic or plastic/metal compound profiles. The plastic material may include fiber reinforcement such as glass fibers. Another technical field in which corresponding extruded plastic or plastic/metal compound profiles are used is the field of profiles for sliding windows or roofs in automobiles.

[0003] The plastic or plastic/metal compound profiles are produced by extrusion as an endless extrusion profile and then cut into profile cuts, usually of 6 m length. The cutting is usually done by a saw, often a flying saw. The quality of the cutting in terms of precision and avoiding burrs and the like is important to avoid excessive scrap. The quality of the cutting depends, however, on the materials and geometry of the profiles to be cut, on the type of the saw blade and on the rotational speed of the saw blade and on the cutting speed of the saw blade and on the wear of the saw blade, etc. as know in the art. At present, the parameters rotational speed and cutting speed of the saw blade are set in view of the materials and geometry of the profiles to be cut, the wear of the saw blade, etc. based on the experience and skill of the operator of the saw. This may lead to unnecessary scrap and low production yields.

[0004] There are techniques to automatically set cutting parameters of saws as described in the prior art, e.g. a saw for cutting extruded profiles including a control for controlling the drive power of the drive motor of the saw to be constant described in DE 196 22 374 Al, a saw for cutting extruded profiles including a control for indirectly controlling the cutting speed of the saw by changing the feed rate described in DE 44 08 886 Al, a saw including a control for controlling the cutting speed of the saw considering parameters such as saw blade angle, saw position, motor drive current and speed and acceleration signals described in DE 44 05 660 Al, a device for determining the sharpness degree of a saw blade by vibro-acoustic analysis described in DE 100 57 661 Al, a saw for a harvester including a control for controlling the sawing speed to be constant described in DE 10 2011 108 814 Al .

[0005] However, these techniques do not allow to consider the specific issues for flying saws and the above profiles to be cut.

[0006] Therefore, it is an object of the invention to provide an improved flying saw for cutting extruded profiles, an improved method for controlling a cutting speed of a flying saw for cutting extruded profiles, and an improved extrusion apparatus for manufacturing extruded profile cuts comprising such a flying saw, which are especially suitable for cutting extruded plastic or plastic/metal compound profiles with or without fiber reinforcement for windows, doors and facade elements, sliding windows or roofs in automobiles, and the like. It is also an object to apply the technique to stationary saws for cutting extruded profiles.

[0007] This object is achieved by a flying saw for cutting extruded profiles according to claim 1 , an improved method for controlling a cutting speed of a flying saw for cutting extruded profiles according to claim 8, and an improved extrusion apparatus according to claim 10. The additional object is achieved by a stationary saw according to claim 11 and a method for cutting extruded profiles according to claim 12.

[0008] Further developments of the invention are indicated in the dependent claims.

[0009] The provision of the temperature detector allows to keep the processing temperature at the cutting edge to be below the glass transition temperature and/or below the melting temperature of the thermoplastic materials of the profile to be cut. These temperatures can be measured or taken from a material data sheet. Thus it is possible to define an acceptable temperature maximum and an intended temperature range for the processing. The acceptable temperature maximum and intended temperature range can be stored in the control system and compared it to the continuous measured/detected temperature. The system is quite simple and can be included in the saw control unit.

[0010] This control does not only allow to keep the temperature below the acceptable temperature maximum but also allows to increase the cutting speed if the temperature is low and thus increase the efficiency and to conclude form the detected temperature to the wear of the saw blade as the temperature will be increased for the same cutting speed with increasing wear of the saw blade. If combined with a vibration based control and/or with an optical burr detection, the temperature based control can be improved and potential errors can be avoided more likely.

[0011] Burrs at the cutting edge of thermoplastic profiles occur usually, if the cutting speed is too low. There are many variables which define a low level of cutting speed, e.g. saw blade design, saw blade wear, room temperature, profile temperature, etc. Therefore, it is difficult to define a model to calculate the optimum cutting speed. However, the saw blade cutting edge temperature based control allows to conclude to the possible range of increasing the cutting speed such that it becomes easier to define a control scheme. [0012] Further advantages and characteristics follow from the description of embodiments referring to the accompanying drawings, which show:

Fig. 1 a cross-sectional side view of an exemplary schematic extrusion apparatus in a) and enlarged views of parts of the apparatus in b) and c);

Fig. 2 a schematic view of a flying saw according to an embodiment;

Fig. 3 a more detailed schematic view of a flying saw according to an embodiment; and

Fig. 4 a) to d) cross-sectional views of four exemplary profiles to be cut.

[0013] Fig. 1 is a cross-sectional side view of an exemplary schematic extrusion apparatus in a) and enlarged views of parts of the apparatus in b) and c).

[0014] The extrusion apparatus shown in Fig. 1 comprises an extruder 1, an extrusion die

2 and a calibration unit including a cooling unit 3 and a vacuum unit 4 as known in the art. For extruding plastic or plastic/metal compound profiles, the plastic material is fed into the extruder 1, heated up above its melting temperature and then pressed through the extrusion die. The plastic material described further below may but does not have to include reinforcing fiber materials such as glass fibers, carbon fibers, aramid fibers and the like. Of course, the usual fillers, additives, etc. may be included in the plastic material. The extrusion die schematically shown in a cross-sectional side view in Fig. la) and b) results in a hollow extrusion profile, but any type of extrusion profiles suitable for the above indicated purposes is possible. The extrusion die 2 can be suitable for a co-extrusion or for adding one or more metal sheets or metal wires as known in the art. The feeding direction of the plastic material in the extruder 1 and in the extrusion die 2 as well as in the calibration unit 3, 4 is from left to right in Fig. 1. A pulling and/or conveying unit 5 is positioned downstream of the calibration unit 3, 4 in the feeding direction. The drawing/conveying unit 5 draws the calibrated extrusion profile in the feeding direction to maintain a continuous movement of the extruded profile. A flying saw 10, a further drawing/conveying unit 5, a conveying unit 6 and product table 7 are positioned in this order downstream of the first drawing unit 5 in the feeding direction, as shown in Fig. la) and lc). The flying saw 10 is moveable back and forth parallel to the feeding direction in order to cut the moving extrusion profile P into pieces or profile cuts CP of a predetermined length. For this purpose, the flying saw 10 comprises a saw blade which can be moved perpendicular to the feeding direction as schematically shown in Fig. la) and c). The profile cuts CP are singled and transported in the feeding direction and finally laid on to the product table 7.

[0015] Fig. 4a) to d) show cross-sectional views perpendicular to the longitudinal direction of four exemplary profiles to be cut. A profile is formed, for example, from a thermoplastic polymer selected from the group consisting of polyethylene terephthalates, polyurethanes, poly- imides, polyetherimides, polytetrafluoroethylenes, polyvinylchlorides, polyamides, polycarbonates, epoxy resins, polymethylmethacrylates, polystyrenes, polysiloxanes, polyphenylene oxides, polyketones, polyetheretherketones, biopolymers, and mixtures thereof, or a mixture thereof with one or more polyolefm(s), and/or a thermoplastic polymer is selected from the group consisting of PA66, PA6, PA/PPO, SPS, and the biopolymers PA4.10, PA5.5, PA5.10, PA6.10, PA10.10, PA11 and PA10.12, and mixtures thereof, or a mixture thereof with one or more polyolefm(s). The profile is manufactured by extrusion. As already described above, usual fillers and additives and reinforcing materials such as glass fibers can be added. Furthermore, depending on the application of the profile, the extruded profile may be a plastic/metal com- pound profile. For example, if the extruded profile is designated to be a spacer for IGUs, it is common to coextrude a thin metal layer of stainless steel or coated steel with the plastic material to cover at least one side of the profile or to laminate or deposit the thin metal layer thereon. The cross-section perpendicular to the longitudinal direction of such a spacer profile is shown in Fig. 4d). It is also possible to include reinforcements such as metal sheets embedded in the plastic material or metal wires or fiber wires embedded in the plastic material. Examples for such rein- forcements are disclosed in EP 1 055 046 B2. The profiles shown in Fig. 4a) and b) are designed to connect metal profiles of windows, doors and facade elements. It is obvious, that they can have cross-sectional shapes of a rather simple design as shown in Fig. 4a) or of a more sophisticated design with many arms or branches, which are more difficult to cut. The same applies to a profile such as the one shown in Fig. 4c), which, in the cross-section perpendicular to its longitudinal direction, has hollow spaces, partly open spaces and protruding arms. It goes without saying that these profiles may include corresponding reinforcements or metal or other coatings as described with respect to Fig. 4d). Moreover, it may be necessary to cut the plastic or plastic/metal compound profiles shown in Fig. 4 together with other attached profiles such as the metal profiles of windows, doors and facade elements.

[0016] For all these profiles, but especially for profiles for sliding windows or sliding roofs in automobiles or for example for spacer profiles which need to be sealed against gas diffusion, the quality of the cross-sectional face cut by the flying saw is of great importance. If the quality is not good enough, the corresponding profile cut is a scrap. The quality of this cut de- pends on many parameters such as the saw blade design, the saw blade angle, the saw blade wear, the rotational speed of the saw blade, the speed of moving the saw blade perpendicular to the longitudinal direction of the profile, the temperature of the profile, the temperature of the surrounding space such as the room temperature, the type(s) of the material(s) and the combination of material(s) as well as the cross-sectional shape of the profile. Therefore, it is difficult to define a control model to calculate an optimum cutting speed for cutting such profiles. For example, depending on the angle of the saw blade or the wear of the saw blade or the materials in the profile, the temperature at the cutting edge of the saw may be too high for the plastic material of the profile. Especially if the temperature at the cutting edge of the saw blade is at or above the glass transition temperature and/or the melting temperature of the plastic materials of the profile to be cut, an acceptable quality of the cut face cannot be obtained. For example, if metal inserts are present in the profile to be cut, the temperature of the cutting edge may be significantly higher than without such metal inserts, even if the other materials and the design of the profile are the same otherwise. On the other hand, if a cutting speed is to low, burrs are likely to be generated at the cut face of the profile. Moreover, as a flying saw by nature of its design and purpose has to move along the feeding direction of the profile while cutting the same, vibration analysis is less reliable than in case of a stationary saw.

[0017] Fig. 2 shows a schematic view of a flying saw according to an embodiment and

Fig. 3 shows a more detailed schematic view of a flying saw according to an embodiment. In Fig. 1, 2 and 3, corresponding elements have corresponding reference signs. As schematically shown in Fig. 2, the saw unit 10 comprises a temperature sensor 12. This temperature sensor may be, for example, an infrared temperature sensor detecting the temperature of the cutting edge of the saw blade 11 based on the infrared radiation of the same. Of course, it is also possible to use other technologies such as a temperature-dependent metal coating changing its resistance based on its temperature. In such a case, eddy currents in the rotating saw blade that change with the temperature could be measured. However, an infrared temperature sensor is considered to be the easiest way to implement the temperature detection in the present case.

[0018] In the schematic drawing in Fig. 2, the feeding direction is represented by the arrow F. The movement of the flying saw and its saw blade 11 back and forth parallel to the feeding direction F is represented by the arrow FS H. A movement perpendicular to the longitudinal direction of the profile which corresponds to the feeding direction F, is represented by the arrow FS L. The rotational speed is represented by the arrow SR. The temperature sensor 12 is connected to the control system 13, which controls the rotational speed SR and the movement FS L perpendicular to the longitudinal direction of the profile P depending on the detected temperature. The rotational speed SR and the movement of the saw blade perpendicular to the longitudinal direction of the profile P combine to a cutting speed. Accordingly, the cutting speed can be changed by changing the rotational speed SR of the saw blade 11 and/or by changing speed of the movement of the saw blade 11 perpendicular to the longitudinal direction of the profile P. The movement of the saw blade 11 perpendicular to the longitudinal direction of the profile P can be of course in movement in the lateral direction only, as indicated by the arrow FS L in Fig. 2, or can be a movement in a vertical direction FS V only or a combination of the same. Fig. 3 shows a more detailed schematic drawing of an embodiment of a flying saw. The flying saw 10 comprises the saw blade 11 driven for rotation by a first saw blade drive 17, which usually includes an electric motor for rotating the saw blade 11. The flying saw 10 further comprises a support 14 for the circular saw. The support 14 allows to move the circular saw 11, 17 in the first direction FS H corresponding to (= parallel to) the feeding direction F. This is accomplished in the shown embodiment by circular saw 11, 17 on a saw carriage 16, which is supported on a linear movement unit 15. The saw carriage 16 allows to move the circular saw 11, 17 in the lateral horizontal direction FS L and/or in the vertical direction FS V as indicated by the arrows in Fig. 3. The saw carriage 16 is moveable back and forth in the first direction FS V by the linear mov- ing unit 15 as also indicated by the arrows in Fig. 3. Accordingly, the saw blade 11 can be rotated by the first saw blade drive 17 and can be moved perpendicular to the longitudinal direction of a profile P which longitudinal direction corresponds to the feeding direction F, by the saw carriage 16 and can be moved back and forth along the longitudinal direction (P = feeding direction F) by the linear moving unit 15. In addition, the moveable workpiece support 18 is posi- tioned below the profile to be cut to support the profile during the cutting operation. The work- piece support 18 is also moveable back and forth in the first direction FS V.

[0019] The control system 13 is connected to the drives of the drawing/conveying units 5 via signal lines 19, 21 and is connected to the drive of the conveying unit 6 via signal line 22. The control system 13 is connected to the support 14, the saw blade drive unit 17, the saw car- riage 16, the linear moving unit 15, the workpiece support 18 and the temperature sensor 12 via signal line 20. Thus, the control system 13 can control the speeds of movement of the profile P to be cut and of the profile cuts CP after the profile has been cut as well as the rotational speed of the saw blade 11 and the speed of movement of the saw blade 11 in the three directions FS H, FS L and FS V as well as the corresponding movement speed in the direction FS H of the workpiece support 18. Furthermore, the control system 13 can obtain the result of the IR measurement of the temperature of the cutting edge of the saw blade 11 via signal line 20.

[0020] Thus, the control system 13 is enabled to move the saw blade 11 and the work- piece support 18 in synchronization with the movement of the profile P to be cut and, at the same time, to control the cutting speed resulting from rotational speed SR of the saw blade 11 and of the speed of movement of the saw blade 11 perpendicular to the longitudinal direction of the profile P using the temperature detected by the temperature sensor 12. The control scheme is described further below. It is obvious from Fig. 3, that the conveying speed of the drawing/conveying unit downstream of the saw blade 11 in the feeding direction F is higher than the conveying speed upstream of the saw blade in order to single the profile cuts CP. Furthermore, the conveying speed of the conveying unit 6 is at least equal to this higher conveying speed of the second drawing/conveying unit 5 in order to maintain the singling and to be able to properly lay the profile cuts CP on the product table 7. It is obvious that these conveying speeds are controlled by the control system 13 via signal lines 19, 21 and 22.

[0021] Furthermore, the flying saw 10 may optionally include a vibration detection de- vice 23 for detecting vibrations of the saw blade and/or of the profile P to be cut. The vibration detection is made in the usual way by detecting the vibrations acoustically and/or optically. The vibration detection device 23 is connected to the control system 13 via signal line 24.

[0022] The flying saw 10 optionally includes an optical detection device for detecting burrs at the cut face of the extruded profile after it has been cut and/or of the profile cuts CP. This optical detection device 25 is connected to the control system 13 via signal line 26. [0023] The control scheme for the operation of the flying saw 10 can consider the above described cutting parameters in the usual way. In addition, the control scheme uses the detected temperature of the cutting edge of the saw blade 11 to prevent to exceed a maximum temperature for cutting the material and optionally to optimize the cutting speed based on the detected tem- perature. As already described above, depending on the material of the profile and/or depending on the design of the profile, a specific cutting speed will result in a corresponding temperature of the cutting edge of the saw blade 11. However, this correspondence changes over time due to the wear of the saw blade and/or other factors such as room temperature, profile temperature, the saw blade wear, changing saw blade angle and so on. Moreover, as also described above, burrs will occur at the cut face, if the cutting speed is too low. Whether the cutting speed can be increased can be decided based on the detected temperature of the cutting edge of the saw blade as an important factor. Moreover, a temperature of the cutting edge of the saw blade below a specific temperature for a given profile indicates a cutting speed, which is too low.

[0024] Accordingly, the flying saw is controlled to be keep the temperature of the cutting edge of the saw blade within a predetermined temperature range. The upper limit of the temperature range is determined by the glass transition temperature and/or the melting temperature of the plastic material of the profile to be cut minus a certain offset value of, for example 5K, 10K, 15K, 20K, 25K, 30K, 35K, 40K, 45K, 50K. For usual thermoplastic materials that preferable offset is at least 10K. The offset does not need to be bigger than 50K under normal circumstanc- es.

[0025] The lower limit of the temperature range is usually set to be 10K, 15K, 20K, 25K,

30K, 35K, 40K less than the upper limit. Within this temperature range, the control can increase or decrease the rotational speed of the saw blade 11 and/or the speed of movement of the saw blade 11 perpendicular to the longitudinal direction of the profile P in order to control the cutting speed and the quality of the cut face of the profile P to be cut and of the profile cuts CP. [0026] HM and HSS saw blades with different teethings can be used, where the saw blade diameter is usually in the range between 250 and 350 mm, preferably 300 mm, and the rotational speed of the saw blade is usually set in a range between 1000 and 1500 rpm. The moving speed of the profiles to be cut is in the range of 4 to 12 m/min. [0027] The technique and control of the temperature can also be used for stationary saws and not only for flying saws. In such a case, the plural profiles can be cut simultaneously.

[0028] It is explicitly stated that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and/or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges.