METHOD FOR SEPARATING OLDER WORKPIECES AND MACHINING MACHINE FOR CARRYING OUT SUCH A METHOD

Description

[0001] The invention relates to a method for separating elongated workpieces according to the preamble of claim 1 and to a processing machine for carrying out such a method according to the preamble of claim 11.

[0002] It is a known method to cut elongated workpieces into thin lamellae using thin circular saw blades. The circular saw blades are mounted close together on a rotating spindle. The workpieces, especially those made of wood or wood-like materials, often have defects such as knots and the like, which can cause the circular saw blades to deform or even break due to increased cutting pressure. Deformation of the circular saw blades results in lower quality of the cut lamellae because the deformation causes a corresponding offset in the cut.

[0003] The circular saw blades of the saw assembly generate a certain noise level, which becomes very high if the blades deform or vibrate, for example. This increased noise prompts the user of a sawing device to stop the workpiece feed, move the workpiece back so that the circular saw blades are free from the workpiece (EP 2 845 674 A). However, this procedure is very time-consuming and unreliable. If the user does not hear or recognize the increased noise level, there is a risk that the saw assembly will be damaged and thus fail.

[0004] It has therefore been suggested that the workpiece feed should be automatically stopped when the noise level exceeds a permissible value. However, this method is also not very effective, because the workpiece still has to be retracted to clear the circular saw blades.

[0005] It is also known (EP 1 927 829 A2) to use a sensor unit to detect sound waves generated during the machining of a workpiece.

[0006] Other methods are known (US 4,644,832 A) in which lateral movements of a circular saw blade during the sawing process are detected. These lateral movements are converted into signals that are compared with stored signal values. The rotational speed of the circular saw blade is then controlled based on this comparison.

[0007] The invention is based on the objective of designing the generic method and the generic processing machine in such a way that the workpieces can be reliably and flawlessly divided into thin lamellae with high machine performance.

[0008] This problem is solved according to the invention in the generic method with the characterizing features of claim 1 and in the generic processing machine according to the invention with the characterizing features of claim 11.

[0009] In the inventive method, the sound level is monitored during rotation of the circular saw blade and during the sawing process. The sound level values ​​are fed to the evaluation electronics. If the circular saw blade is subjected to increased cutting pressure, the sound level of the circular saw blade increases. Based on the stored empirical data, the process-reliable feed rate for the respective sawing operation is determined and selected. A process-reliable feed rate means that the sound level remains below a critical limit during the sawing process. If this critical sound level is reached or approaches this limit, the feed rate of the workpiece is reduced. This reduces the cutting pressure acting on the circular saw blade, which in turn eliminates any deformation, vibration, or deviation of the circular saw blade.This manifests as a decrease in the current sound level value, which the evaluation electronics use to increase the workpiece feed rate again so that the current sound level value is within the permissible range. As soon as the actual sound level falls below the predefined limit, the workpiece feed rate is increased again.

[0010] The process-reliable feed rate is advantageous, as is the optimal feed rate, so that the machine has high performance for carrying out the process.

[0011] With the method according to the invention, it is possible to saw the workpieces into thin lamellae in a continuous process, even if an increased cutting pressure should occur temporarily, for example due to defects within the workpiece.

[0012] In the simplest case, the feed rate is reduced when the sound level limit is reached. In this case, it is advantageous for safety reasons to set this limit somewhat lower than it could be set at maximum utilization.

[0013] The stored empirical data is advantageous, including the feed rate, circular saw blade thickness, and / or sound level. Using this stored data, the optimal feed rate can be determined and selected.

[0014] Further empirical data regarding the workpiece type and / or thickness, the number of teeth on the circular saw blade, and / or the rotational speed of the circular saw blade can be advantageously used. This makes it possible, for example, to select the optimal feed rate with regard to the type of workpiece being cut. The workpiece-related empirical data can be correlated with tool-related data, allowing the various circular saw blades to be optimally matched to the different workpieces, thus preventing impermissible overloading of the circular saw blade during the sawing process.

[0015] In an advantageous procedure, the reference value of the sound level is first determined, from which the sound level limit value is set.

[0016] To determine the reference value, a new circular saw blade is used, with which standard workpieces are cut over a defined period during normal production. It is advantageous if the sound level recording only begins after a short production period. At this point, the circular saw blade has reached its working sharpness. A circular saw blade that has not yet been used for workpiece processing exhibits an over-sharpening characteristic that is not typical of a saw blade that has been put into operation. The same applies if the circular saw blade has been newly sharpened. It, too, will then have an over-sharpening characteristic. Therefore, in this case as well, it is advisable to use the newly sharpened circular saw blade briefly before recording the sound level values.

[0017] In addition to or instead of reducing the workpiece feed rate, it is also possible to change the rotational speed of the circular saw blade if the measured sound level reaches the limit value. For example, natural frequencies excited during workpiece machining can be problematic. In such cases, machining can be carried out within the optimal operating range by combining (increasing or decreasing) the rotational speed of the circular saw blade with a reduction in the workpiece feed rate.

[0018] The reference value and the limit value of the sound level are advantageously stored in a memory of the evaluation unit or a control system, so that they can be retrieved in later applications when using the same circular saw blade and similar workpieces.

[0019] The feed rate of the workpieces and / or the rotational speed of the circular saw blade can be continuously or incrementally variable. Continuous adjustment of the feed rate or rotational speed has the advantage that these values ​​can be reduced only to the extent necessary.

[0020] When making incremental changes, the corresponding increments for reducing the feed rate or changing the rotational speed are correspondingly larger. For this reason, it is advantageous to keep the step size relatively small.

[0021] In a preferred training setting, the reference value of the sound level of the circular saw blade is automatically determined and saved.

[0022] It is also advantageous if the feed rate of the workpieces is changed automatically. This allows the workpieces to be machined without an operator.

[0023] It is also advantageous if the sound level limit is automatically determined based on the reference value. This allows the procedure to be carried out by less experienced workers.

[0024] It is advantageous to use an additional limit value to activate a warning message. The warning message can be an acoustic and / or visual signal that gives the user of the process a hint, for example, to check or monitor the process or to inspect the wear of the circular saw blades.

[0025] The machining machine according to the invention is characterized in that it is equipped with at least one sound sensor which is arranged in the sound field of the circular saw blade and which records the sound level of the circular saw blade. The sound sensor sends its recorded sound level signals to the evaluation unit, which evaluates these signals and uses them to change the feed rate of the workpieces if necessary.

[0026] The sound sensor can advantageously send the sound level signals to the evaluation unit without the need for an intermediate bandpass filter.

[0027] The machine's memory stores empirical data. This data pertains to at least the workpiece feed rate and noise level limits. The evaluation unit or control system can access this stored data and use it to select and determine the optimal, and ideally, the most reliable feed rate. Feed rates and noise level limits are stored for a wide variety of circular saw blades, workpieces, and other components. This allows any type of workpiece to be machined with any type of circular saw blade within its optimal operating range.

[0028] The evaluation unit is part of the control system for the processing machine.

[0029] The processing machine is advantageously a tenoning machine, in which the workpieces are machined on four sides in a continuous process using the upper and lower horizontal processing tools as well as the right and left vertical processing tools before being fed to the circular saw blade. The workpieces thus only reach the circular saw blade once they have already been machined on all four sides.

[0030] The circular saw blade is advantageously positioned behind the last processing tool, still within the grooving machine, in the direction of workpiece transport. This allows the sawn-out thin lamellae to exit the grooving machine. The sound sensor and evaluation unit can be retrofitted to existing grooving machines.

[0031] It is advantageous if additional process and processing parameters are stored in the data storage.

[0032] A single circular saw blade is generally sufficient for cutting the workpieces. However, it is advantageous if the circular saw blade is part of at least one circular saw package. With such a package, the workpiece can be divided into several thin strips, depending on the number of circular saw blades in the package.

[0033] The subject matter of the application is not only defined by the subject matter of the individual patent claims, but also by all information and features disclosed in the drawings and the description. These are claimed as essential to the invention, even if they are not explicitly stated in the claims, insofar as they are novel, individually or in combination, compared to the prior art.

[0034] Further features of the invention will become apparent from the further claims, the description and the drawings.

[0035] The invention is explained in more detail with reference to an embodiment illustrated in the drawings. The drawings show... Fig. 1 shows a simplified and perspective view of a processing machine according to the invention, Fig. 2 shows an enlarged view of a sawing device of the processing machine according to the invention. Fig. 1 .

[0036] Fig. 1 Figure 1 shows a molding machine as an example of a processing machine, which can process workpieces 1 on all four sides as they pass through the machine. The workpieces 1 are preferably made of wood, but can also be made of wood-like materials, plastic, and the like. The elongated workpieces 1 have a rectangular outline and are processed on all four long sides as they pass through the molding machine.

[0037] The workpieces 1 are fed via a feed table 2 to a machine table 3, on which the workpieces 1 are transported by the grooving machine. Transport rollers 4 are provided for transporting the workpieces 1; these rollers are rotatably driven about their axes and bear against the top of the workpieces 1 under pressure. The workpieces 1 are transported by the grooving machine in the direction of arrow 5.

[0038] The workpiece 1 entering the grooving machine is first machined on its underside by a lower tool 6, which is rotatable about a horizontal axis. In the transport direction 5 behind the lower tool 6, a right-hand tool 7 is located in the grooving machine. This tool is rotatably driven about a vertical axis and machines the right-hand longitudinal side of the workpiece 1 in the transport direction 5 as it passes through. The opposite left-hand longitudinal side of the workpiece 1 is machined by a left-hand tool 8, which is also rotatably driven about a vertical axis, as it passes through. Advantageously, the left-hand tool 8 is positioned behind the right-hand tool 7 in the transport direction 5.

[0039] In the transport direction 5 behind the left tool 7, an upper tool 9 is provided, which is rotatably driven about a horizontal axis and with which the top of the workpiece 1 is machined as it passes through the grooving machine.

[0040] In the transport direction 5 behind the upper tool 9, the grooving machine has a lower tool 10, which is rotatably driven about a horizontal axis and with which the underside of the workpiece 1 is machined again.

[0041] Depending on the application, the tenoning machine may have additional right, left, upper or lower spindles that carry the corresponding tools.

[0042] In the exemplary embodiment, the grooving machine is also provided with a lower table roller 11, which is rotatable about a horizontal axis and is provided behind the lower tool 10 in the transport direction 5.

[0043] In order for the lower tools 6, 10 to machine the underside of the workpiece 1, the machine table 3 is interrupted in the area of ​​these tools 6, 10.

[0044] To set the chip removal rate on the right-hand tool 7, the workpiece 1, when fed into the tenoning machine, rests with its right longitudinal side (in the transport direction 5) against a guide rail 12 extending in the transport direction 5. It extends from the infeed table 2 into the tenoning machine as far as the right-hand tool 7. To ensure the precise alignment of the workpiece 1 during its passage through the tenoning machine, the workpiece 1, after being machined by the right-hand tool 7, rests with its right longitudinal side against a stop (hidden by the workpiece 1 in the figures).

[0045] Following the four-sided machining of the workpiece 1, the tenoning machine contains two adjacent saw packs 13 and 14, which are rotatably driven about vertical axes. Each saw pack 13, 14 consists of stacked circular saw blades 15 ( Fig. 2The circular saw blades 15 are arranged vertically on a spindle 16, 17, spaced apart. Following surface processing, the workpiece 1 is cut into thin lamellae using these blades. The rotatably driven spindles 16, 17 are located laterally to the workpiece 1 as it passes through the machine. The circular saw blades 15 of the two saw packs 13, 14 are arranged such that the workpiece 1 is cut into thin lamellae across its width. The circular saw blades 15 of the two saw packs 13, 14 are at the same height.

[0046] The thin lamellae exit the grooving machine at outlet 18. To ensure reliable lamellae exit, at least one horizontal table roller 19 is located at outlet 18. This roller is positioned behind the saw packs 13 and 14 in the transport direction 5 and supports the thin lamellae as they exit the grooving machine. At least one further transport roller 4 is located approximately at the level of table roller 19, which transports the lamella pack.

[0047] To detect damage during the sawing of the workpieces 1 at an early stage, the processing machine is equipped with a monitoring device 20, which includes at least one microphone 21 connected to a control unit 22. The control unit 22 can be operated using an operating panel 23 on a control cabinet 24 of the processing machine.

[0048] The connection between the microphone 21 and the controller 22 can be wired or wireless. In the drawings, this connection is symbolically represented by line 25.

[0049] The microphone 21 is suitably mounted in the machine tool and positioned so that it can record the sound generated by the saw packs 13, 14 during the sawing of the workpieces 1. The microphone 21 is advantageously located in the immediate vicinity of the saw packs 13, 14, enabling reliable sound measurement. The control unit 22 includes an evaluation unit for analyzing the sound recorded by the microphone 21. This evaluation unit is advantageously integrated into the machine control unit 22. However, it is also possible to provide the evaluation unit as a separate unit that supplies signals to the control unit.

[0050] The monitoring device 20 monitors the processing of the workpiece 1 by the saw assemblies 13, 14 by means of the noise level of the saw assemblies 13, 14. If a predetermined noise level is exceeded, this indicates that the circular saw blades 15, for example, are showing excessive wear, the cutting pressure is too high due to defects in the workpiece 1 (causing the saw blades to vibrate or wander), the circular saw blades 15 have become jammed in the workpiece 1 to such an extent that a clean cut is no longer possible, or there is a risk of the respective circular saw blade 15 breaking. Preferably, the feed rate is automatically adjusted depending on the noise level.

[0051] First, at the start of a new production run or when a new saw package 13, 14 is used, the sound level is recorded while sawing through a workpiece 1. Preferably, workpieces from the production batch to be processed, covering the average quality range, are used for this purpose. The determined sound level value serves as a reference value for setting a limit value for the sound level, at the point where the feed rate V s of the workpiece 1 is reduced or the feed is switched off.

[0052] The reference value and the limit value, along with process data such as machining, workpiece, and tool parameters that can influence the sound level, are stored as empirical values ​​in a memory or database of the evaluation unit or control system. Such parameters include, for example, feed rate, tool speed, wood type, wood thickness, cutting depth when sawing or through, number of saw cuts or saw blades, saw blade diameter, saw blade thickness, number of teeth, and tooth shape. The use of saw blades with reamers, riving knives that prevent recutting, or spray or lubrication media can also influence the sound level; therefore, it is advantageous to store corresponding information as well.

[0053] The database can also be implemented remotely from the machine in the form of a cloud solution, to which the machine transmits the data and from which it receives reference and limit values.

[0054] This data is advantageously obtained through measurements for the various machining tasks and for the different types of workpieces and saw packages.

[0055] If the saw packages 13, 14 are fitted with circular saw blades 15 of different thicknesses and / or sizes, then the measurements are also taken with regard to the different circular saw blades. All measured values ​​are stored in the memory or database. The database makes it possible to provide limit values ​​for new machining tasks.

[0056] In this way, the separation of the workpieces 1 (optimal feed rate, sound level limits) can be determined depending on the saw packages 13, 14 used or their circular saw blades 15 and / or the material from which the workpieces 1 are made.

[0057] This allows the optimal process parameters for the respective processing task to be found and defined.

[0058] If the workpieces 1 are sawn into thin lamellae using the two saw packs 13 and 14 after their four-sided machining, the resulting sound level is recorded by the microphone 21. The recorded sound level values ​​are fed to the evaluation unit, which compares the recorded actual sound level values ​​with the respective stored limit value. As long as the actual sound level value is below the limit value, the workpieces 1 can be transported at their optimal feed rate V s and sawn into thin lamellae.

[0059] Should the sound level during the sawing process reach the limit value, the evaluation unit or the control system sends a signal to the feed drive(s) for the workpiece 1 to reduce the feed rate Vs. This, in turn, reduces the cutting pressure acting on the circular saw blades 15, thus decreasing the sound level generated by the saw assemblies 13, 14. As soon as the actual sound level falls below the predefined limit value, the feed rate Vs of the workpiece is increased again.

[0060] If the sound level does not decrease despite a reduction in the feed rate V s of workpiece 1, the evaluation unit can be designed to generate a warning signal and / or switch off the feed for workpiece 1.

[0061] To prevent the feed rate from being reduced if the limit value is only briefly exceeded, the evaluation unit is advantageously designed so that the sound level must remain above the limit value for a predetermined period of time.

[0062] If the sound level is reduced by reducing the feed rate V s, then it is advantageous not to immediately increase the feed rate again after falling below the sound level limit, but to wait a predetermined time to see if the sound level of the saw packages 13, 14 remains below the limit during this period.

[0063] In an advantageous design, the feed rate V s of the workpieces 1 is continuously adjusted.

[0064] The evaluation electronics can also be designed in such a way that the feed rate V s is reduced or increased in steps.

[0065] The evaluation electronics are advantageously designed so that the monitoring and adjustment of the feed rate Vs of the workpieces 1 is carried out automatically. In this case, unmanned production of the thin lamellae is possible.

[0066] Since the sound level of the saw packs 13, 14 is monitored, very thin circular saw blades 15 can be used, which are generally more susceptible to damage. The use of such thin circular saw blades 15 leads to a significant saving of material, since more lamellae can be sawn out of the workpiece 1 with the thin circular saw blades 15 than with thicker circular saw blades.

[0067] Due to the sound level monitoring during the sawing process, damage to the circular saw blades 15, the saw packs 13, 14, and the processing machine can be prevented. Thanks to the described sound level monitoring, the thin lamellae can be produced with very high dimensional accuracy. Furthermore, the sound level monitoring, in conjunction with the adjustment of the feed rate Vs of the workpieces 1, results in a long service life for the saw packs 13, 14. This, in turn, leads to increased availability of the processing machine or the corresponding system.

[0068] The described sound level measurement also allows for reliable monitoring of the wear condition of the saw assemblies 13, 14. As the circular saw blades 15 of the saw assemblies 13, 14 wear down, the baseline sound level increases. When the sound level of the saw assemblies 13, 14 approaches the limit value, it is advisable to replace the saw assemblies 13, 14, or possibly just individual circular saw blades 15 of the saw assemblies 13, 14. This ensures optimal utilization of the service life of the saw assemblies 13, 14.

[0069] Advantageously, a second limit value can be used for a warning message or indicator. This value is below the monitoring limit value for the feed rate. The warning message can also alert the operator that something has changed in the process, requiring, for example, closer observation or checking the tool wear.

[0070] Furthermore, it is possible not to use the saw packages 13, 14 for their maximum possible service life, but to provide replacement intervals for the saw packages 13, 14 which can be selected to be optimally long due to the sound level monitoring.

[0071] The interaction of sound level and feed rate of the workpieces allows the saw packages 13, 14 to be used in the optimal working range.

[0072] The sound level monitoring system with the evaluation unit and the control or regulation of the machine's feed drives can be retrofitted into existing machines, so that such processing machines can also benefit from the described advantages when sawing.

[0073] It is advantageous if the reference sound level is determined automatically after the processing machine is switched on. Manual intervention by the user is not necessary. Such a system has the advantage that the reference sound level is determined automatically when the saw packs 13 and 14 are changed. The measurement is advantageously started only when newly sharpened tools have reached their working sharpness, i.e., not immediately at the start of production, but after a few linear meters.

[0074] Furthermore, the evaluation unit is advantageously designed so that the operator of the processing machine can adjust the reference values ​​before the actual production start. This allows the operator to iteratively approach the optimal reference value for the sound level.

[0075] The sound level values ​​measured by microphone 21 can be transmitted to the evaluation unit via analog or bus system. The monitoring device can be implemented using commercially available standard components consisting of a microphone and evaluation unit and requires no special modifications or additional components, such as bandpass filters or similar.

[0076] The evaluation unit, control system, or database application can link the sound level value with other stored process parameters. As already described, such process parameters include parameters relating to the machining process (feed rate, rotational speed of the saw packs 13, 14, cutting depth, sawing or through-cutting, use of riving knives or lubricants), the tool (diameter, thickness, and number of circular saw blades 15, number of teeth, tooth shape, use of reamers), and the workpiece 1 (workpiece type, material, thickness, moisture content).

[0077] These parameters influence the sound level, possibly in addition to other, unmentioned factors. Therefore, if these process and machining parameters are stored, the machine control or evaluation unit can relate the measured sound level value to one or more of these parameters and thus set or specify the optimal feed rate Vs of workpiece 1. Statements about the optimal process can be made even before production begins.

[0078] It is advantageous, when the sound level limit is exceeded, not only to reduce the feed rate Vs, but also to change the rotational speed of the saw blades 13, 14. In this way, by adjusting the degree of reduction in feed rate Vs and / or the change in rotational speed, it becomes possible to avoid impermissible vibrations and damage to the circular saw blades 15 and / or the workpiece 1.

[0079] The described training and procedure is also possible if only a single circular saw blade is used.

Claims

1. Method for cutting elongated workpieces (1) which consist of wood, plastic and the like, by means of at least one rotatably driven circular saw blade (15), in which the sound level is recorded during rotation of the circular saw blade (15) and supplied to an evaluation unit, and wherein the feed rate (VS) of the workpieces (1) is monitored, characterized in that a process-safe feed rate for the sawing process to be carried out is determined and selected on the basis of stored empirical values, that during the sawing process with the process-safe feed rate the sound level remains below a critical limiting value, that the feed rate of the workpiece is reduced when the sound level approaches or reaches this limiting value and that the feed rate of the workpiece (1) is increased again as soon as the actual value of the sound level falls below the predefined limiting-value sound level.

2. Method according to Claim 1, characterized in that the stored empirical values are the feed rate and / or the circular saw blade thickness and / or the sound level.

3. Method according to Claim 1 or 2, characterized in that the stored empirical values are the workpiece type and / or the number of teeth of the circular saw blade (15) and / or the rotational speed of the circular saw blade (15).

4. Method according to one of Claims 1 to 3, characterized in that a reference value of the sound level is firstly determined, from which the limiting value of the sound level is determined.

5. Method according to one of Claims 1 to 4, characterized in that the rotational speed of the circular saw blade (15) is changed at least when approaching the limiting value of the sound level.

6. Method according to one of Claims 1 to 5, characterized in that the reference value and the limiting value of the sound level are stored in a memory or in a database.

7. Method according to one of Claims 1 to 6, characterized in that the feed rate (VS) of the workpieces (1) and / or the rotational speed of the saw blade (15) can be changed continuously or stepwise.

8. Method according to one of Claims 1 to 7, characterized in that the reference value of the sound level of the circular saw blade (15) is automatically determined and stored.

9. Method according to one of Claims 1 to 8, characterized in that the feed rate (VS) of the workpieces (1) is automatically changed.

10. Method according to one of Claims 1 to 9, characterized in that the limiting value of the sound level is determined automatically as a function of the reference value, and that preferably a further limiting value is used to activate a warning message.

11. Processing machine for carrying out the method according to one of Claims 1 to 10, comprising at least one circular saw blade (5), in the sound region whereof at least one sound sensor (21) is arranged, which supplies the recorded sound level signals to an evaluation unit and comprising at least one memory in which empirical values of limiting values of the sound level are stored to which the evaluation unit has access, characterized in that empirical values with regard to the feed rate (VS) are stored in the memory, that the evaluation unit is part of a control (22) of the processing machine and that the control has access to the stored empirical values, that the control (22) determines and selects a process-safe feed rate (VS) for the sawing process to be carried out with reference to the stored empirical values so that the sound level remains below a critical limiting value during the sawing process with the process-safe feed rate (VS), that the control (22) reduces the feed rate (VS) of the workpiece (1) when the sound level approaches or reaches this limiting value and the feed rate (VS) is increased again as soon as the actual value of the sound level falls below the predefined limiting value sound level.

12. Processing machine according to Claim 11, characterized in that the processing machine is a moulding machine having at least one upper horizontal machining tool (9), at least one lower horizontal machining tool (6, 10), at least one right vertical machining tool (7) and at least one left vertical machining tool (8), and that the circular saw blade (15) is advantageously arranged in the transport direction (5) of the workpieces (1) behind the last machining tool (11) in the moulding machine.

13. Processing machine according to Claim 11 or 12, characterized in that further process and processing parameters are stored in the data memory.

14. Processing machine according to one of Claims 11 to 13, characterized in that the circular saw blade (15) is part of at least one circular saw package (13, 14).