Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B21/00—Machines or devices using grinding or polishing belts; Accessories therefor
  • B24B21/04—Machines or devices using grinding or polishing belts; Accessories therefor for grinding plane surfaces
  • B24B21/06—Machines or devices using grinding or polishing belts; Accessories therefor for grinding plane surfaces involving members with limited contact area pressing the belt against the work, e.g. shoes sweeping across the whole area to be ground
  • B24B21/08—Pressure shoes; Pressure members, e.g. backing belts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B21/00—Machines or devices using grinding or polishing belts; Accessories therefor
  • B24B21/04—Machines or devices using grinding or polishing belts; Accessories therefor for grinding plane surfaces
  • B24B21/12—Machines or devices using grinding or polishing belts; Accessories therefor for grinding plane surfaces involving a contact wheel or roller pressing the belt against the work
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
  • B24B49/02—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent

Definitions

• the invention relates to a method for monitoring a grinding process, to a method for controlling and / or regulating a grinding process, and to a monitoring system and a belt grinding machine according to the independent claims.
• Belt grinding machines are known from the prior art. Furthermore, devices and methods are known to control and / or regulate a grinding process and monitor.
• the DE 199 15 909 C2 proposes a method for controlling a grinding process.
• sensors are to be used to monitor the grinding process.
• the operator is responsible for ascertaining whether chatter marks are present on the surface by circling the surface of a workpiece, for example a chipboard.
• the DE 10 2012 109 086 A1 deals with the monitoring of a grinding process. For this purpose, it proposes, for example, provide sensors for each change in position of the workpiece to be ground. It is also proposed that the belt grinding machine be followed by a test station whose sensors examine the machined workpiece with regard to compliance with certain parameters. If this investigation shows that the workpiece can not be released, it is forwarded to an operator for follow-up.
• a scanner bar is known, which is similar to the aforementioned test station.
• the scanner bar can be arranged in front of the grinding unit.
• the information captured by the scanner bar may be passed to a controller of the belt grinder to determine which press bar pressure elements to use to machine the workpiece.
• the DE 10 2007 012 780 A1 further proposes to place a scanner bar behind the sanding unit to capture information about the surface of the machined workpiece.
• Such information can relate, for example, to the structure or color of the surface and its roughness or roughness. This information can then be compared with reference values. Thus, the grinding result and the wear of the abrasive can be judged.
• Known belt grinders usually require intensive and close-meshed control of the grinding process by an operator. Furthermore, often a desired grinding result is not achieved. Furthermore, wear parts such as the abrasive belts are often prematurely replaced prematurely to prevent the abrasive belt from operating for too long. A subsequent premature disposal of the abrasive belts leads to high operating costs and pollutes the environment.
• the object of the invention is to overcome the disadvantages of the prior art.
• a method for monitoring a grinding process in which a workpiece is ground in a belt grinding machine, wherein the belt grinding machine has a grinding head which comprises a contact roller and / or a sanding shoe and at least one deflection roller, wherein an abrasive belt is guided by the at least one deflection roller or together by the at least one deflection roller and the contact roller, wherein the belt grinding machine has a feed device for moving the workpiece relative to the grinding head during the grinding process, the grinding belt being pressed onto a surface of the workpiece during grinding by the contact roller and / or by the grinding shoe, wherein the belt grinding machine is further assigned a sensor unit for scanning the surface of the workpiece, which communicates with an evaluation unit, the sensor unit scans the surface of the workpiece after grinding, wherein the sensor unit and the evaluation unit are adapted to detect the presence of at least one chatter mark.
• the workpiece may, for example, be a plate, for example a chipboard, an MDF board (medium density fiberboard), an oriented strand board (OSB), a chipboard or a board made of another material such as wood, Laminate or the like act.
• MDF board medium density fiberboard
• OSB oriented strand board
• chipboard or a board made of another material such as wood, Laminate or the like act.
• the feed device may be, for example, a transport table or a conveyor belt.
• the feed device moves the workpiece relative to the grinding head.
• the workpiece with the aid of the feed device is guided past the grinding head such that it can machine the surface of the workpiece.
• the sensor unit is expediently arranged in the feed direction downstream or behind the grinding head in order to scan the surface of the ground workpiece.
• the sensor unit comprises at least one sensor, but it may also comprise a plurality of sensors of the same or different type.
• Ratter marks are surface defects. These usually occur in series and often have a characteristic appearance.
• the present invention aims to analyze and evaluate both a frequency with which the chatter marks occur or the distances between the chatter marks, as well as properties and / or the nature of individual chatter marks.
• non-contact sensors for example optical sensors
• optical sensors are used.
• the sensors are preferably adapted to scan the surface of the workpiece after grinding and to detect at least one property of the surface of the workpiece. These include, for example, the presence, location, orientation, nature, such as dimensions or amplitude, of chatter marks, and roughness. Furthermore, it can be thought of any other characteristics. Since chatter marks occur both as depressions and as elevations, the amplitude of a chatter mark their depth or height understood in comparison to the rest of the workpiece. The amplitude can be recorded and handled as an amount. On the other hand, the amplitude can also be recorded and handled as a signed variable, so that in each case not only the magnitude of the amplitude is fixed, but also whether it is a height or elevation or a depth or depression.
• the sensors can perform their function individually or in combination, for example by being interconnected. The same applies to several sensor units.
• Such sensors for determining, in particular, a three-dimensional nature as well as properties and properties of surfaces are known.
• Suitable measuring methods are, for example, a white light interferometry, a focus variation, confocal measuring methods such as profilometry, an interferometry, a measurement of holography and the like.
• the belt grinding machine may comprise a control and / or regulating device. In this case, it may be thought to integrate the evaluation unit in the control and / or regulating device. However, the evaluation unit can also be designed as a separate component or integrated into the sensor unit.
• the present invention particularly relates to so-called wide-belt sanding machines, but is not intended to be limited thereto.
• wide-belt sanding machines in particular permanently installed, i. understood not hand-guided grinding machines whose abrasive belts have a width of over one meter.
• the width of the sanding belts is between 1.3 and 3.3 meters.
• a belt grinding machine comprises at least one grinding head, often also referred to as an abrasive aggregate.
• the grinding head is understood to mean the unit described above, which comprises at least the components likewise described and supports or guides the grinding belt during grinding.
• a belt sander may include one or more sanding heads. If the belt grinding machine comprises several grinding heads, these can be accommodated in only one housing or in several housings. In the latter case, the housing can be modularly assembled.
• a belt grinder comprises at least two each other opposite grinding heads, so that in particular both sides of a plate to be processed can be ground at the same time. With respect to an imaginary plane, within which the feed device is located, such paired grinding heads are arranged substantially mirror-inverted above and below the imaginary plane. However, it can also be thought to edit a workpiece to be machined only from one side and provide instead of paired grinding heads individual grinding heads.
• a pressure applied to the workpiece can be adjusted by adjusting the pressure of the contact rollers and / or the sanding shoes of the two sanding heads accordingly.
• a pressure applied to the workpiece can be adjusted by adjusting the pressure of the contact rollers and / or the sanding shoes of the two sanding heads accordingly.
• the function of this counter bearing can meet either the feed device or a counter-pressure roller.
• Such a counter-pressure roller is preferably provided opposite to the individually arranged grinding head and causes from the non-machined or to be grounded side of the workpiece a pressurization, which is directed to the grinding belt.
• a plurality of belt grinding machines comprising one or more grinding heads can cooperate in such a way that a workpiece to be machined is processed successively by at least two belt grinding machines.
• the cooperating belt grinding machines for example, use the same feed device or share this feed device.
• a handover in particular by means of an automatically operating transfer device, can be used, which transfers the workpiece processed by a first belt grinding machine to a second belt grinding machine for processing.
• the belt grinding machine or the grinding line comprises a plurality of grinding heads, it may be conceivable to arrange one sensor unit behind each of several grinding heads or even behind all the grinding heads.
• At least one sensor unit downstream of the at least one sensor head at least one further sensor unit upstream, ie before the at least one grinding head to arrange.
• a sensor unit would thus be arranged in front of and behind the grinding head.
• the upstream sensor unit can scan the surface of the workpiece to be machined in the same manner as already described with regard to the sensor unit arranged downstream. Further, the measurement data detected by the upstream sensor unit may be compared with the measurement data detected by the downstream sensor unit. This comparison can be automated, for example by subtraction of comparative measurement data regarding roughness or chatter marks.
• An upstream sensor unit may allow the method of monitoring the grinding process to automatically adapt to different workpieces of different nature or materials.
• the method described herein for monitoring the grinding process is often superior to monitoring the grinding process by an operator or may at least assist the operator.
• the often high feed rate or the high number of cycles mean that the operator does not have enough time to judge a grinding result.
• quality features and properties of the surface of a workpiece can already reach an undesirable extent if they are not recognizable to an eye of the operator or only with great difficulty.
• Monitoring as described above is therefore often superior to operator supervision in terms of precision, reliability and speed.
• the sensor unit and the evaluation unit detect a property and / or a condition of the at least one chatter mark in the event of the presence of at least one chatter mark on the surface of the workpiece.
• the sensor unit and the evaluation in the presence of at least one chatter mark on the surface of the workpiece on the basis of the property and / or the nature of the chatter mark determine whether the chatter mark by a belt connection of the abrasive belt and / or by the contact roller and / or caused by the feed device and / or by another component of the belt grinding machine.
• Sanding belts are usually designed as endless belts.
• Such an endless belt is produced by connecting a flat abrasive belt to a closed belt, in particular by gluing. Methods for producing such a continuous abrasive belt, in particular by gluing, are known.
• a thickness of the abrasive belt often deviates from a thickness of the remaining abrasive belt, which can lead to chatter marks.
• chatter marks can be generated by targeted manipulations in preliminary experiments. This can be thought of a targeted manipulation of a component or a component of the belt grinding machine or to a targeted execution of at least one setting of the belt grinding machine, which leads to the formation of chatter marks. These chatter marks can then be examined and characterized. If the abovementioned preliminary test is carried out separately for different manipulations and the chatter marks caused thereby differ from one another in at least one property, then this property can be detected by the sensor unit in order to conclude the cause of the detected chatter mark on the basis of this property.
• chatter marks can also be thought to assign certain properties of chatter marks to certain causes based on empirical values or regularities and without preliminary tests and to ensure by appropriate measures that the sensor unit can also make this assignment if it recognizes the at least one specific property of a detected chatter mark ,
• the following properties of the chatter marks come into consideration: amplitude of the chatter mark in the workpiece, for example the amplitude at a certain position in the workpiece or the maximum amplitude or the average amplitude or a depth and / or height profile ; a location of the chatter mark on the workpiece; an orientation of the chatter mark on the workpiece; a width of the chatter mark; a length of the chatter mark and the like.
• chatter marks In addition to the abovementioned properties of individual chatter marks, it may also be considered to use properties relating to at least two chatter marks in a corresponding manner. Of course, these properties may also be used singly or in combination, also in combination with the above mentioned properties of individual chatter marks. In this case, for example, at a distance of at least two chatter marks; at an average distance of at least three chatter marks; be thought of mean values of the properties described above with respect to individual chatter marks as well as the change of such a property of individual chatter marks when comparing multiple chatter marks.
• the properties relating to at least two chatter marks can be assigned in advance by means of preliminary tests certain causes. In the evaluation of these properties, in turn, a conclusion can be drawn on the cause or at least on the most likely cause. If the distances of the chatter marks, for example, indifferent to a change in the feed rate, so a defect in the feed device or in the feed system is assumed. For example, a feed roller of the feed device could be defective or faulty.
• a known law is that a formula can be used to judge whether given chatter marks are caused by the band connection.
• the distance M of two chatter marks caused by the band connection is calculated by dividing the product of the grinding belt length L and the feed speed v v by the product of the sixty times the grinding belt speed v s and the number of belt connections n of the respective grinding belt.
• the distance between the chatter marks and the abrasive belt length are measured in mm.
• the feed rate is measured in meters per minute, the grinding belt speed in meters per second.
• chatter marks are caused by a faulty, for example out-of-round, contact roller
• the sensor unit and the evaluation unit detect all chatter marks on a workpiece and then it is determined whether the distances between some or all chatter marks satisfy at least one of the above regularities.
• chatter mark series which are based on various causes and which are superimposed occur, can be analyzed.
• the sensor unit and the evaluation unit can detect the distances to all other chatter marks on the workpiece for each chatter mark present on a workpiece.
• those chatter marks can be identified which satisfy one of the aforementioned laws and thus, for example, indicate the band connections or a non-circular contact roll.
• chatter marks may be assigned to specific causes on the basis of their properties or properties or to verify an already assigned assignment with the aid of properties or quality features. For example, if the distance of an identified plurality or series of chatter marks on the contact roller as the cause and is also known that such chatter marks are within certain limits with respect to certain characteristics such as amplitude or depth and / or height profile or width, so by analyzing this Characteristics and comparison with the aforementioned limits are verified, whether the considered chatter marks are actually due to the contact roller as a cause.
• chatter marks or individual chatter marks series can also be used to assess the quality of the workpiece. Provided that the sensor unit is sufficiently sensitive, it is possible that chatter marks series are detected, but the individual chatter marks of this series do not yet represent a quality defect of the work piece with regard to their characteristics, in particular with regard to their amplitude or their depth and / or height profile. In most cases, however, chatter marks initially occur to such an extent and to such an extent that no intervention is necessary. However, without intervention, chatter marks usually occur to such an extent and extent that intervention is absolutely necessary
• the sensor unit and the evaluation unit detect the roughness of the surface of the workpiece.
• the sensor unit and the evaluation unit detect the roughness both before and after making the change in case of a change in a setting of the belt grinding machine.
• At least one desired or necessarily occurring effect to be aimed at making the above-described change in attitude is a change in roughness, then the above-described before and after measurement can determine whether the desired effect entry.
• Such a change may, for example, be the replacement of an abrasive belt, since abrasive belts have different characteristics and differ, for example, as to whether they produce a coarser or a finer finish. Whether the finish is coarser or finer may depend, inter alia, on the following abrasive belt parameters: a grain type, a grain shape, a grain size, a grain spread, and a selection of a binder and a filler.
• such a change can also be a change in a pressure with which, for example, the contact roller or the sanding pad act on the sanding belt and thus press it onto the workpiece to be machined.
• a pressure with which, for example, the contact roller or the sanding pad act on the sanding belt and thus press it onto the workpiece to be machined.
• this pressure is adjusted to steer the roughness in the desired direction, and it is determined by the above-described before-and-after measurement that the desired effect is missing, this may indicate that the abrasive belt or one of the abrasive belts has reached its maximum service life and the so-called lifetime is exceeded.
• measurement data detected by the sensor unit and evaluated by the evaluation unit are compared with predetermined limit values, a signal being output when a predefined limit value is exceeded or undershot.
• the measurement data which are detected by the sensor unit and evaluated by the evaluation unit, relate in particular to roughness and chatter marks, but may also relate to other properties of the workpiece.
• the predetermined limit values can be set, for example, by an operator. Depending on which characteristics or properties are detected by the sensor unit and forwarded as measurement data to the evaluation unit, it may be expedient to specify an upper limit value or a lower limit value. Further, if the characteristic feature to be detected is to move within a certain range and thus does not exceed an upper limit value or fall below a lower limit value, it may also be considered to specify both an upper limit value and a lower limit value.
• the output signal may be a warning signal or a control signal. Of course, it may also be thought to output both a warning signal and a control signal.
• warning signal In the case of a warning signal, individually or in combination, an acoustic, an optical or a different type of warning signal may be intended.
• the warning signal can also be passed on to a suitable signal generator, for example to a siren or to a horn.
• the signal can also be displayed on a control panel of the belt grinder.
• a control signal can be thought that when exceeding or falling below the limit value generates a control signal and the belt grinder, in particular their control and / or regulating device is supplied. If a roughness limit is exceeded and the surface of the workpiece is thus too rough, for example, a control signal can be generated which increases the pressure with which the contact roller or the sanding pad acts on the sanding belt. If a conditional feature is detected which indicates a repair of a defective belt grinder, a control signal can be generated which causes an emergency stop of the belt grinder. Accordingly, it may be conceived to detect and evaluate a multiplicity of features and, after a comparison with a predetermined limit, to generate a control signal in order in particular to regulate the grinding process. Thus, an automatic readjustment of at least one, but preferably several settings of the belt grinding machine can take place during operation.
• limit value In an analogous manner, as described above with respect to only one limit value, it may also be intended to assign a plurality of limit values and a plurality of signals to one another in different ways. On the one hand may be thought that, for example, exceeding a limit, the output causes multiple signals, including multiple control signals. Furthermore, it can be thought that exceeding different limit values causes the output of the same signal. For example, both certain chatter marks and a certain roughness can cause an emergency stop. Further assignments of limit values and signals are conceivable.
• measured data detected by the sensor unit and evaluated by the evaluation unit are compared with limit values, a signal being output if a predetermined limit value is exceeded or undershot, the limit value of at least one property or setting of the belt grinding machine depends.
• the limit value or the limit values therefore need not be fixed unchangeable for each belt grinding machine, but can be adapted to the settings and properties, that is to say to the configuration of the belt grinding machine.
• the abovementioned properties and settings of the belt grinding machine include, for example, a condition or type of the grinding belt, a grain sequence, i. Properties and properties of a grain of a plurality of successive abrasive belts, a predetermined and / or an actually measured feed or a feed rate, a feed direction, a grinding belt speed, a nature or a type of grinding head, a nature or a kind of the sanding pad and a condition or a genus of contact roller.
• the limit value or the limit values can either be set by an operator or automatically predefined.
• the operator selects the limit value based on his or her experience or specific work instructions and on the abovementioned properties and settings or on the configuration of the belt sander.
• the limit value is set automatically, it may be thought, for example, that an operator inputs the abovementioned properties and settings of the belt grinding machine via an operating panel and the control and / or regulating device calculates the limit value on the basis of this input.
• the properties and settings of the belt grinding machine are automatically detected by suitable sensors and the calculation of the limit values is carried out automatically and without the intervention of an operator.
• suitable sensors for detecting the nature or type of the abrasive belt, the grinding head, the sanding shoe, the contact roller, etc. are used.
• measured data acquired by the sensor unit and evaluated by the evaluation unit are combined over a period of time and combined to form a measurement curve, whereby a characteristic of the measurement curve is calculated, wherein a signal is output if the characteristic of the measurement curve lies within a certain range Mass deviates from a specification regarding this property.
• the calculated property of the measurement curve it is possible, for example, to think of all properties which can be determined by mathematical methods and in an automated manner. For example, the detection of the following properties as well as the change of these properties in the stated period may be considered: local or global minima and maxima, regression curves and regression lines and their slopes, limits, fluctuations, inflection points, symmetries, derivatives and integrals. Of course, it may be thought to calculate not only one but at the same time several properties of the waveform as described above and, if appropriate, to use to generate a signal.
• a measurement over a period of time is often more meaningful. Which of the aforementioned properties of the measurement curve is meaningful enough to be used to output the signal can be determined in preliminary tests.
• the period can be adapted to the grinding process. It may also be conceived to combine the acquired measured values into different measured curves, based on different time periods. For example, it may be thought to calculate fluctuations or maxima of the trace both on a given day and in the previous 10 days. If the fluctuations or maxima on the observed day deviate to a large extent from the fluctuations and maxima of the preceding 10 days, this could necessitate an intervention in the grinding process, which can be effected by the output of a signal.
• the aforementioned method makes it possible for the first time to control and / or regulate the grinding process based on measurement data which are acquired during operation.
• belt grinding machine is expediently usually equipped with the control or regulating device already described.
• At least one sensor unit is arranged upstream, then it may also be considered to use the measured data acquired by this sensor unit in the same way as already described for the downstream sensor unit for controlling and / or regulating the grinding process.
• the roughness of a workpiece to be machined can be detected and then at least one setting, for example the pressure of a sanding pad, can be adapted accordingly.
• the present invention further proposes a monitoring system for a belt grinding machine with a sensor unit for scanning a surface of a workpiece and an evaluation unit, wherein the sensor unit and the evaluation unit are adapted to detect the presence of at least one chatter mark.
• the sensor unit and the evaluation unit may be configured as described above with respect to the method for monitoring. It may be thought to integrate the monitoring system into belt grinders already in operation or to retrofit them with the monitoring system. If available, an evaluation unit already installed in the belt sander can be used.
• the sensor unit and the evaluation unit are adapted to determine in the presence of at least one chatter mark on the surface of the workpiece on the basis of a property and / or on the nature of the chatter mark, if the chatter mark by a belt connection of the abrasive belt and / or caused by the contact roller and / or by the feed device.
• the sensor unit for scanning the surface of the workpiece and the evaluation unit are set up in order to transmit control or regulation commands to a control or regulation device based on measurement data detected by the sensor unit and evaluated by the evaluation unit. This is also described above with reference to the method for monitoring the grinding process.
• the present invention proposes a belt grinding machine comprising the monitoring system described above.
• the present invention proposes a belt grinding machine comprising the control system described above.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)

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• 2016
  • 2016-09-06 DE DE102016116622.7A patent/DE102016116622A1/de active Pending
• 2017
  • 2017-09-06 EP EP17189558.4A patent/EP3290154A3/fr active Pending

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