METHOD AND DEVICE FOR CONTROLLING THE FEED SPEED OF CIRCULAR SAW BLADES

Description

[0001] The invention relates to a method for controlling the feed rate of a toothed saw blade rotating around a center of rotation relative to a workpiece during a machining process, wherein sector areas with one tooth or a plurality of adjacent teeth can be defined on the saw blade, wherein during one revolution of the saw blade around the center of rotation the feed rate is selected differently during a machining process caused by teeth of different sector areas of the saw blade, wherein the radial spacing of the teeth or the average radial spacing of the plurality of adjacent teeth of different sector areas differs and the feed rate is selected to be lower during a machining process caused by teeth of sector areas with a larger radial spacing of the teeth from the center of rotation.as during a machining process effected by teeth of sector areas with a smaller radial distance of the teeth from the center of rotation, according to the preamble of claim 1. The invention further relates to a machining device comprising a toothed saw blade, a drive device for rotating the saw blade about a center of rotation, and a feed device for achieving a relative movement of the saw blade to a workpiece, wherein the feed device comprises a control unit for controlling the feed rate of the saw blade relative to the workpiece, and the saw blade has sector areas, each with one tooth or a plurality of adjacent teeth, wherein the control unit is designed to control the feed rate differently during a machining process effected by teeth of different sector areas of the saw blade during one revolution of the saw blade about the center of rotation.by the feed rate being lower during a machining operation performed by teeth of sector regions of the saw blade with a larger radial distance of the teeth from the center of rotation or a larger average radial distance of the majority of adjacent teeth from the center of rotation than during a machining operation performed by teeth of sector regions of the saw blade with a smaller radial distance of the teeth from the center of rotation or a smaller average radial distance of the majority of adjacent teeth from the center of rotation, according to the preamble of claim 4.

[0002] During the machining process, the teeth of the saw blade are subjected to high stress. The teeth can be either integrally formed or screwed on; in the latter case, the saw blades are sometimes also referred to as disc cutters, but are hereafter also encompassed by the term "saw blades." Appropriate control of the machining process aims to minimize the stress while maintaining optimal cutting results. The machining process itself is carried out using a control system that preferably automates the cutting parameters such as the saw blade's rotational speed and feed rate. Monitoring the condition of the saw blade plays an increasingly important role in this process.Here, geometric, static, and dynamic analyses of the saw blade are performed using sensors at rest, during idling, and during the machining process. These analyses are used to draw conclusions about the load on the saw blade in order to subsequently control the machining process accordingly, or to detect excessive loads early and take appropriate maintenance or repair measures. These sensors can be cameras, force or strain gauges, directional microphones, piezoelectric sensors, and the like. A generic method and a generic device are described in DE 42 02 724 A1.

[0003] A method according to the preamble of claim 1 and a machining device according to the preamble of claim 4 are known from DE 44 05 660 A1.

[0004] For example, DE 19634336 A1 describes a device and a method for measuring the saw blade teeth of circular saw blades, in particular for measuring the tooth shape, tooth pitch, tooth height (tooth depth) as well as the radial and axial runout using optical scanning methods.

[0005] DE 10023566 A1 discloses a device and a method for optical inspection of saw blades and individual saw teeth.

[0006] EP 0949480 A2 describes a device for measuring the geometry of saw blades in order to determine essential parameters such as rake angle and clearance angle on the teeth.

[0007] EP 0403908 A2 shows the measurement of a cutting tool with a camera.

[0008] In GB 1072569 A, CH 653600 A5, WO 0107868 A1 and US 5861564 A, further devices and methods for the optical measurement of the geometry of saw teeth are described.

[0009] DE 202017103056 U and DE 102017126434 A1 disclose the acquisition of parameters for measuring and monitoring saw blades during operation. EP 0969340 A1 describes the monitoring of the actual drive current during the operation of a saw blade and its comparison with a target drive current, as well as corresponding control of the saw blade.

[0010] In the aforementioned state of the art, a geometric measurement of the saw blade is used to detect stresses or deformations of the saw blade or its teeth at an early stage and to take appropriate maintenance or repair measures.

[0011] The aim of the invention, however, is to reduce stress on the saw blade, so that maintenance or repair measures can be avoided and the service life is increased.

[0012] This objective is achieved by the features of claim 1. Claim 1 relates to a method for controlling the feed rate of a toothed saw blade rotating about a center of rotation relative to a workpiece during a machining operation, wherein sector areas with one tooth or a plurality of adjacent teeth can be defined on the saw blade, and wherein, during one revolution of the saw blade about the center of rotation, the feed rate is selected differently during a machining operation effected by teeth of different sector areas of the saw blade.wherein the radial spacing of the teeth or the average radial spacing of the majority of adjacent teeth from different sector areas differs, and the feed rate is selected to be lower during a machining process carried out by teeth from sector areas with a larger radial spacing of the teeth from the center of rotation than during a machining process carried out by teeth from sector areas with a smaller radial spacing of the teeth from the center of rotation. According to the invention, it is proposed that a measuring device for measuring the radial spacing of the teeth from a center of rotation of the saw blade is provided, which is connected to the control unit. The method according to the invention thus reduces stresses on the saw blade by combining geometric condition monitoring of the saw blade with suitable control of the machining process. The applicant has determined thatIt is sometimes observed that, during the manufacturing, assembly, or operation of saw blades, sector areas with one or more adjacent teeth can be found, where the radial spacing of the teeth or the average radial spacing of the multiple adjacent teeth differs between different sector areas. These deviations usually manifest as an eccentricity of the saw blade, with a first sector area exhibiting the largest average radial spacing of the teeth in that first sector area and a second, usually opposite, sector area exhibiting the smallest average radial spacing of the teeth in that second sector area. Observations by the applicant show that wear and breakage of teeth occur more frequently in segment areas with a larger radial spacing.In this case, where the saw blade radius is in the meter range, the deviations from the average radial spacing of the saw blade teeth are in the range of micrometers to hundredths of a millimeter. The distance of the tooth tip from the center of rotation can be used as the radial spacing of the teeth, as it is easily measurable; however, it would also be conceivable to use other reference points for determining the radial spacing. By measuring the radial spacing of each tooth using methods known per se, it can be determined whether sector areas according to the invention can be defined in which the average radial spacing is greater than in other sector areas. If this is the case, the machining process is subsequently controlled such that the feed rate is reduced during one revolution of the saw blade.as long as teeth of the sector area with a larger radial spacing are involved in the machining process. The lower feed rate reduces the loads on the teeth of this sector area during the machining process. Conversely, the feed rate can be increased again as soon as teeth of a sector area with a smaller radial spacing are involved in the machining process. The method according to the invention is therefore suitable for saw blades where the feed rate can be controlled according to the invention during one revolution of the saw blade, which is the case for many applications of saw blades with a radius in the meter range and rotational speeds in the range of 100 m / min. Due to the reduced load on the teeth resulting from the control of the feed rate, maintenance or repair measures can be postponed and the service life increased.

[0013] Provided the geometry of the saw blade allows it, the division into sector areas could be so precise that each sector area contains only one tooth. The feed rate would then be controlled accordingly, based on the radial spacing of each tooth. Such a procedure would be advantageous, for example, during the initial cutting process, where only individual teeth are engaged with the workpiece.

[0014] For the aforementioned case of saw blade eccentricity, it is proposed that the feed rate reaches a minimum speed during a machining operation performed by teeth in a sector of the saw blade with a plurality of adjacent teeth at the largest average radial distance of the teeth from the center of rotation, and a maximum speed during a machining operation performed by teeth in a sector of the saw blade with a plurality of adjacent teeth at the smallest average radial distance of the teeth from the center of rotation. The feed rate is thus varied between a minimum and a maximum speed during one revolution of the saw blade.The extent of the increase and decrease in feed rate during the inventive method will generally depend on the degree of eccentricity. As the saw blade rotates, a sector with a larger radial distance of the teeth from the center of rotation approaches the workpiece, resulting in an apparent increase in feed rate. This apparent increase in feed rate must be compensated for by a reduction in feed rate according to the inventive method. Conversely, as the saw blade rotates, a sector with a smaller radial distance of the teeth from the center of rotation approaches the workpiece, resulting in an apparent decrease in feed rate. This apparent decrease in feed rate must also be compensated for by an increase in feed rate according to the inventive method.It should also be mentioned at this point that the feed rate refers to a relative movement between the saw blade and the workpiece, so it is irrelevant whether the saw blade is moved relative to the workpiece or the workpiece relative to the saw blade.

[0015] As will be explained in more detail later, with low eccentricity of the saw blade, for example, a triangular feed rate profile can be selected over one revolution of the saw blade. Alternatively, a trapezoidal profile is also proposed, whereby the feed rate during a machining process caused by teeth in a sector of the saw blade with a plurality of adjacent teeth at their largest average radial distance from the center of rotation is a constant minimum speed, and the feed rate during a machining process caused by teeth in a sector of the saw blade with a plurality of adjacent teeth at their smallest average radial distance from the center of rotation is a constant maximum speed.Phases of constant feed rate thus transition into one another via comparatively rapid changes in feed rate, which will be advantageous, for example, with saw blades with greater eccentricity.

[0016] Furthermore, the invention relates to a machining device comprising a toothed saw blade, a drive device for rotating the saw blade around a center of rotation, and a feed device for achieving relative movement of the saw blade to a workpiece, wherein the feed device includes a control unit for controlling the feed rate of the saw blade relative to the workpiece, and the saw blade has sector areas, each with one tooth or a plurality of adjacent teeth, wherein the control unit is designed to control the feed rate differently during a machining process effected by teeth of different sector areas of the saw blade during one revolution of the saw blade around the center of rotation.by ensuring that the feed rate is lower during a machining process performed by teeth of sector regions of the saw blade with a larger radial distance of the teeth from the center of rotation or a larger average radial distance of the majority of adjacent teeth from the center of rotation than during a machining process performed by teeth of sector regions of the saw blade with a smaller radial distance of the teeth from the center of rotation or a smaller average radial distance of the majority of adjacent teeth from the center of rotation. According to the invention, it is proposed that the machining device includes a measuring device for measuring the radial distance of the teeth from a center of rotation of the saw blade, which is connected to the control unit.

[0017] Measuring the radial distances of the saw blade teeth to the center of rotation can be performed on a test bench at the manufacturer's or user's site. The results can then be implemented in the control unit to control the feed rate according to the invention. However, the invention proposes that the machining device includes a measuring device for measuring the radial distance of the teeth from the center of rotation of the saw blade, which is connected to the control unit. This allows for continuous measurement of the radial distances of the saw blade teeth to the center of rotation, for example, during idling, in order to continuously monitor the geometric conditions of the saw blade and compare them with the control specifications.Of course, it is also conceivable to send this measurement data to a remote monitoring system, where the geometric conditions on the saw blade are continuously checked, compared with the current control specifications, and, if necessary, new control specifications are sent to the control unit in order to optimize the operation of the saw blade and increase its service life.

[0018] The invention will be explained in more detail below with reference to exemplary embodiments and the accompanying drawings. These drawings show the following: Fig. 1 a real example of measuring the radial distances of the teeth of a saw blade from the center of rotation, Fig. 2 a possible control curve for the feed rate with a triangular shape, and the Fig. 3 another control curve for the feed rate with a trapezoidal shape.

[0019] First, attention will be drawn to the Fig. 1 Reference is made to a real-world example of measuring the radial distances of a saw blade's teeth from the center of rotation. This measurement can be performed using optical methods, where a measuring device is positioned around the circumference of the saw blade and is traversed by the teeth. As mentioned earlier, the distance of the tooth tip from the center of rotation can be used as the radial distance, since it is easily measurable. However, other reference points could also be used to determine the radial distances. The radial distance can be measured as absolute values ​​or as relative values, representing deviations from a reference value. Fig. 1 The figure shows measured values ​​for 58 teeth of a saw blade in the form of deviations from a reference value, with each tooth assigned a sector s. For each sector s, the corresponding deviation is plotted on a radial beam, with the measurement points connected to each other to show the deviations in the Fig. 1 to generate a visible curve. The reference value is marked with "0" in a first sector s. Clockwise of the Fig. 1 Starting with the first sector s, the radial distances between the teeth initially decrease, reaching a minimum value in the eleventh sector. The radial distances then increase again, reaching a maximum value in the forty-second sector s. Subsequently, the radial distances decrease once more, eventually returning to the reference value in the first sector s. These deviations range from micrometers to hundredths of a millimeter.The saw blade thus exhibits an eccentricity for which two sector regions S1 and S2, each with several sectors s, can be defined. The teeth of a first sector region S1 of the saw blade comprise a plurality of adjacent teeth exhibiting the largest average radial distance from the center of rotation, while the teeth of a second sector region S2 of the saw blade comprise a plurality of adjacent teeth exhibiting the smallest average radial distance from the center of rotation. The choice of sector boundaries for the two sector regions S1 and S2, which are defined in the... Fig. 1 which are indicated by the dashed lines, is fundamentally not decisive and only relevant in connection with the control curve of the feed rate v according to the Fig. 3 relevant, as will be explained in more detail later.

[0020] Determining the eccentricity of the saw blade according to the Fig. 1 According to the invention, this serves to determine a feed rate v that varies over one revolution of the saw blade by selecting a lower feed rate v during a machining process carried out by teeth of the first sector area S1 of the saw blade than during a machining process carried out by teeth of the second sector area S2 of the saw blade. During the machining process, the teeth of the saw blade do not usually penetrate the workpiece simultaneously, but rather, depending on the penetration depth into the workpiece, only the teeth of a larger or smaller number of adjacent sectors s penetrate.For saw blades where the feed rate v can be changed during a revolution of the saw blade, the feed rate v can be selected differently for different sector areas during their respective participation in the machining process, which is the case for many applications of saw blades with a radius in the meter range and rotational speeds in the range of 100m / min.

[0021] One possible control curve for the feed rate v is shown in the Fig. 2 The feed rate v is varied between a minimum speed vmin and a maximum speed vmax during one revolution of the saw blade. The extent of the increase and decrease in the feed rate v during the inventive method will generally depend on the degree of eccentricity, as already explained. The change between the minimum speed vmin and the maximum speed vmax can be achieved via a triangular profile of the feed rate v over one revolution of the saw blade, as shown in the Fig. 2 as is evident.

[0022] Alternatively, the control sequence can be determined according to the Fig. 3 It can also be done in such a way that during the involvement of teeth of the person in the Fig. 1 In the first sector area S1 shown, a constant minimum speed v min is maintained during the machining process, and during the involvement of teeth of the Fig. 1 The second sector area S2, as shown, maintains a constant maximum speed vmax during the machining process. These phases of constant feed rate vmax transition into one another via comparatively rapid changes in feed rate vmax, as shown in the diagram. Fig. 3 This is evident. Of course, more complex control patterns for the feed rate v are also conceivable than those of the Fig. 2 und 3This should be considered if the saw blade measurement reveals a more complex geometry. Provided the saw blade geometry allows, the division into sector areas S could even be so precise that each sector area S contains only one tooth. The feed rate v would then be controlled accordingly, based on the radial spacing of each tooth. Such a procedure would be advantageous, for example, during the initial cutting process, where only individual teeth are engaged with the workpiece.

[0023] The measuring device required for measuring the saw blade can also be part of the machining device and connected to the control unit. The radial distances of the saw blade teeth to the center of rotation can thus be continuously measured to constantly check the geometric relationships of the saw blade, compare them with the current control specifications, and, if necessary, send new control specifications to the control unit. In this way, the operation of the saw blade can be optimized and its service life increased.

Claims

1. Method for controlling the feed rate (v) of a toothed saw blade rotating around a center of rotation relative to a workpiece during a machining operation, wherein sector areas (S) with one tooth or a plurality of adjacent teeth can be defined on the saw blade, wherein during one revolution of the saw blade around the center of rotation the feed rate (v) is selected differently during a machining operation caused by teeth of different sector areas (S) of the saw blade, wherein the radial spacing of the teeth or the average radial spacing of the plurality of adjacent teeth of different sector areas (S) differs, and the feed rate (v) is selected lower during a machining operation caused by teeth of sector areas (S1) with a larger radial spacing of the teeth from the center of rotation than during a machining operation caused by teeth of sector areas (S2) with a smaller radial spacing of the teeth from the center of rotation, characterized in that the sector areas are defined by measuring the radial spacing of each tooth.

2. Method according to claim 1, characterized in that the feed rate (v) during a machining process carried out by teeth of a sector area (S1) of the saw blade with a plurality of adjacent teeth with a largest average radial distance of the teeth from the center of rotation reaches a minimum speed (vmin), and the feed rate (v) during a machining process carried out by teeth of a sector area (S2) of the saw blade with a plurality of adjacent teeth with a smallest average radial distance of the teeth from the center of rotation reaches a maximum speed (vmax).

3. Method according to claim 1 or 2, characterized in that the feed rate (v) during a machining process carried out by teeth of a sector area (S1) of the saw blade with a plurality of adjacent teeth having the largest average radial distance of the teeth from the center of rotation is a constant minimum rate (vmin), and the feed rate (v) during a machining process carried out by teeth of a sector area (S2) of the saw blade with a plurality of adjacent teeth having the smallest average radial distance of the teeth from the center of rotation is a constant maximum rate (vmax).

4. A machining device comprising a toothed saw blade, a drive device for rotating the saw blade around a center of rotation, and a feed device for achieving relative movement of the saw blade to a workpiece, wherein the feed device includes a control unit for controlling the feed rate (v) of the saw blade relative to the workpiece, and the saw blade has sector sections (S) with one tooth or a plurality of adjacent teeth, wherein the control unit is designed to control the feed rate (v) differently during a machining operation caused by teeth of different sector sections (S) of the saw blade during one revolution of the saw blade around the center of rotation, by making the feed rate (v) lower during a machining operation caused by teeth of sector sections (S1) of the saw blade with a larger radial distance of the teeth from the center of rotation or a larger average radial distance of the plurality of adjacent teeth from the center of rotation than during a machining operation caused by teeth of sector sections (S2) of the saw blade with a smaller radial distance of the teeth from the center of rotation or a smaller average radial distance of the majority of adjacent teeth from the rotation center, characterized in that a measuring device for measuring the radial distance of the teeth from a rotation center of the saw blade is provided, which is connected to the control unit.