Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N7/00—After-treatment, e.g. reducing swelling or shrinkage, surfacing; Protecting the edges of boards against access of humidity

Definitions

• the present invention concerns a method used for preparing an item made of MDF (medium density f ⁇ breboard) material before final treatment of the item, which e.g. may be a coating.
• MDF medium density f ⁇ breboard
• JP 60220704 A describes a method for edge finishing of fibre boards where a roller is heated with a burner and pressed against the edge of the board. It is very inexpedient to have open fire in a wood item production, and by the indicated method it is very difficult to control the temperature and thereby achieve a uniform quality of the treated items, hi many countries there is an outright ban on having open fire in production premises where the working of wood items occurs due to the impending fire hazard.
• the purpose of the present invention is to seal the edges of an MDF plate so that the edge coating is easier to perform, i.e. with less preparation, and simplified and in that a uniform quality for all treated items is achieved, the process being mechanical.
• the invention will strongly reduce the time consumption and the costs associated with the use of prior art.
• MDF material is widely used in the wood industry for making furniture, cabinets and fixtures, among others.
• MDF is made of fine wooden fibres with glue as binder.
• the material is relatively easy to work, and by cutting a stable structure is left which can be finished into an acceptable product quality.
• a very used finishing treatment is sanding and filling, ended by coating.
• the prior art method is inexpedient to integrate in an automated production facility.
• wax-containing components are used which are frequently deposited on various tool elements as an inadvertent side effect.
• the process typically requires manual handling in shifting between the different stages of production.
• a heating process will be a usable treatment of item edges in order to reactivate the glue, smooth the edge and thereby achieve a hardened, homogenous and tight surface which is ready for coating.
• a first aspect of the invention is a process for finishing edges of items (10) made of MDF material, the process being characterised by:
• the rotating tool being imparted a movement at a feeding speed along the edge of the item and in contact with the latter while acting on the edge of the item.
• the moving of the tool relative to the item may be by moving the item forward/back relative to the tool, or by moving the tool forward/back in relation to the item; this is termed the relative feeding speed of the tool.
• the friction between the edge of the item and the rotating tool causes a brief local heating which acts as a kind of reactivation of the glue component in the fibre structure of the MDF item.
• the glue in the MDF board is reactivated such that the mechanical action by the tool partly melts, extracts and redistributes the glue in the outermost material layer where the items is worked.
• reheating the glue in the MDF board is reactivated such that the mechanical action by the tool partly melts, extracts and redistributes the glue in the outermost material layer where the items is worked.
• the temperature of contact surface of the tool against the item is determined by: • the relative feeding speed of the rotating tool;
• the material and surface structure of the tool also influence the temperature, as well as MDF boards may be made with different densities, and in some cases it may be desirable to modify the surface structure of the tool such that the most optimal friction between the item and the tool is achieved with regard to reactivating the glue. Also, it would obviously be possible to change the rotational speed of the tool whereby the same advantages as mentioned above are achieved in connection with the feeding speed and the pressure, as an increased rotational speed entails increased friction and thereby increased temperature, and a lower rotational speed will lower the friction between the items and thereby the temperature.
• the process is controlled such that the range of the temperature of the tool surface in contact with the item is from 45 0 C to 9O 0 C.
• the glue may be reactivated in such a way that it becomes partially fluid and is smoothed whereby a smooth and relatively dense edge structure is achieved.
• the temperature begins to have influence on the MDF material, and therefore it is desirable to keep the friction at a level such that the temperature is kept in the indicated interval.
• the pressure action by the rotating tool is angled 0 -> 90° relative to the X - Y plane of the item
• the items treated will typically be plate items where the length and the width of the plate are presently referred to as X- and Y-axes, respectively, and the thickness of the plate will typically be termed the Z-axis.
• the X-Y plane is thus the larger part of the plate. It is important to control the angle of attack of the tool against the item, as there may be applied different bevellings on the edges according to the particular construction in which the MDF item is to form part; for example, it will often be natural in kitchen designs that the MDF boards are cut perpendicularly to the plane of the board, whereas in furniture production, there will often be a need for a sloping bevelling or even a rounding.
• pressure action of the rotating tool can be angled relative to the X-Y plane of the board, it is thus possible to configure the tool to largely all tasks.
• the MDF item can be moved relative to the rotating tool, or the rotating tool can be moved relative to the MDF item.
• the tool forms part of a large processing facility
• handheld or small apparatuses that may be moved along the side of MDF panels may therefore be used for small or special production series.
• electronic means are used for an automatic control and optimisation based on the parameters and process data for tool pressure against item, tool temperature and/or temperature of the point of attack by the tool on the item, rotational speed of the tool and feeding speed of the tool.
• the entire process in particular in a large plant, can be controlled via a central computer such that the process parameters can be optimised all the time and be kept within the given intervals, either by regulating the pressure, the feeding speed, the positional speed of the tool, etc.
• edges of the MDF items will, after being treated by a process as mentioned above, be prepared to a painting or varnishing process which thus finishes the treatment of the item.
• the invention furthermore comprises an apparatus for edge finishing items made of an MDF material, characterised in that the apparatus contains a tool, the tool including a machining surface designed to bear on an edge of the MDF material, that the tool may be caused to rotate about an axis of rotation by means of a motor, that the motor and the tool are arranged in a mount, the mount including means for bringing the machining surface of the tool into contact with the edge of the MDF item under the action of a predetermined pressure.
• This apparatus is designed such that the process steps and the advantages of the process steps specified above can be achieved.
• the tool in the apparatus can be replaced such that, depending on which edge structure or which thickness of the board is desired, or which type of board to be treated, the most optimal tool can be mounted in the apparatus without the entire apparatus necessarily having to be replaced in connection with the upcoming process.
• the apparatus moreover includes means for controlling and adjusting the temperature of the machining surface, wherein the means may include one or more of the following means:
• Fig. 1 shows an example of how an MDF board is processed by a tool
• Fig. 2 shows another example of how an MDF board is processed by a tool
• Fig. 3, 4, 5 show various examples of edge formation that can be processed
• Fig. 6 shows schematically the control means used for controlling the process
• Fig. 7 shows an example of a production line of which the invention forms a part.
• the invention finds application in a fully automated production unit in which the processed MDF items are finished such that they are ready for coating.
• An important aspect of the invention is the use of a rotating tool which is fed under pressure along the edge of the MDF item in a continuously progressing movement.
• the friction arising between the rotating tool and the MDF item develops heat that reactivates, redistributes and re-hardens the glue in the MDF material.
• Feeding speed of tool/item even and continuous at 6 -> 10 m/min; typically 8 m/min.
• Circular tool and size will depend on the capacity of the machine, 10-20 cm in diameter, made of hardened tool steel, Cr-Va-steel, steel K340 or similar; diameter typically 17 cm.
• the steel item may be chromium-plated.
• All geometric edge profiles can be processed and the shape of the machining tool in question can be adapted correspondingly, for example but not limited to: ellipse, circle, triangle and rounded square.
• the rotational speed of the tool varied between 1100 and 1300 rpm, but nice results has also been achieved at substantially higher speeds, up to 6000 rpm.
• the tool contact against the edge of the item may vary, depending on the desired edge profile:
• Fig. 1 shows an example of how the edge (12) of an MDF board (10) is processed by a rotating tool.
• the rotating tool has a bevelling that fits the edge profile by a tolerance of typically 1/10 mm.
• the rotating tool is not a cutting tool but rather bevelled in such a way that a homogenous pressure is exerted across the entire edge.
• the tool is advanced along the edge and bears physically on the edge with a constant pressure/temperature.
• the rotating tool has a rotary axis (15) which is perpendicular to the surface of the board.
• the pressure (13) is directed inwards against the edge of the board in parallel with the X, Y plane of the board, i.e. in parallel with the surface of the board.
• Standard means (5) for producing the rotation of the tool can be a motor with fixed rotational speed or a motor where the rotational speed can be varied up/down.
• the rotating means can be controlled by pneumatics or hydraulics.
• Standard means (16) for performing the required pressing (13) by the tool against the item can be implemented by hydraulics, by pneumatics or as a controllable spring arrangement, e.g. torsion mechanics and a piston.
• Fig. 2 shows another example of how the edge (12) of an MDF board (10) is processed by a rotating tool (11).
• the rotating tool has no bevelling.
• the rotating tool is not a cutting tool but bevelled in such a way that a homogenous pressure is exerted across the entire edge.
• the tool is fed along the edge and bears physically on the edge with a constant pressure/temperature.
• the rotating tool has an axis of rotation (15) which is angled about 45° relative to the surface of the board.
• the pressure (13) is directed inwards against the edge of the board perpendicularly to the surface of the edge, thus angled relative to the X, Y plane of the board, i.e. angled relative the surface of the board.
• Figs. 3, 4 and 5 show various examples of edge shapes that may be processed.
• the edge of the item may have arbitrary geometric shape, e.g. but not limited to: rectangle, ellipse, circle, triangle and rounded square.
• the shape of the tool is designed such that it fits the given task, and may be formed with a cutout like the tool (11) indicated in Fig. 1, or without cutout like the tool (11) indicated in Fig. 2.
• Fig. 6 shows a preferred process setup.
• the rotating tool (11) is driven by a motor including means for controlling rotation of the tool (17) at a stable rotational speed.
• the tool is fed (14) along the item (10) via means, e.g. a motor and a spindle, including means (18) that ensure stable and continuous feeding speed.
• the board (10) may be advanced (26) in contact with the tool (11) via a standard conveyor system (22, 23) simultaneously holding the board.
• the direction of rotation of the tool (11) may advantageously be following in relation to the feeding direction (26) of the item.
• means (16) which can influence the acting pressure of the tool on item (10) are used. During the machining there will compensated in this way for inhomogenities in the hardness of the item.
• These means can be a simple spring load or a controlled hydraulic device.
• the temperature of the attack surface of the tool (11) against the item (10) is an important and decisive factor in order to achieve high finish on the machined edge.
• the temperature can be measured via standard means, e.g. by means of an optical/thermographic external measuring apparatus (20), or alternatively via a built-in thermometer in the metal part of the tool.
• Means (6) for stabilising the temperature of the tool i.e. keeping the temperature constant when the tool is not actively processing a board edge may advantageously be implemented, e.g. in the time between the end of processing a board until the next board is brought to engage the tool.
• Standard means in the form of a heating element (6) in which fire does not form part is usable, e.g. based on electric/magnetic induction.
• a practical arrangement may be that the tool is rotated in a gap between two heating elements.
• an MDF board piece with same edge profile may temporarily be introduced.
• the board piece may e.g. be mounted at the end of a cylinder rod which is activated when no items for machining pass by.
• the surface temperature of the tool is registered by means of a temperature sensor including a laser.
• a temperature sensor including a laser.
• standard means for detecting when a new board is machined for example, a simple infrared sensor (21) may sense whether a board is processed or not.
• the feeding speed of the conveyor belt is accessible, and the speed in possibly measurable and controllable via standard control means (22).
• the invention can be used as element in large/small cell concept, wherein:
• One cell has means for processing an item on one edge at a time; or • one cell has means for processing an item on two edges at a time, where in this setup typically parallel edges are machined simultaneously and pressure is exerted on the tool simultaneously on both edges;
• further electronic means (19) may be used for an automatic control and optimisation based on the parameters and process data for tool pressure against item, tool temperature, rotational speed and feeding speed of the tool.
• a control may be achieved in several alternative ways where the primary goal is to keep the temperature in the point of attack of the tool constant and at operational value or in a permissible operational range.
• the primary goal is to keep the temperature in the point of attack of the tool constant and at operational value or in a permissible operational range.
• control parameters primarily become:
• Standard equipment can be used for the necessary control (19), as an example but not limited to: pneumatics, springs, rubber rollers, PC's, microprocessors and PLL controls.
• the control unit may include a stand-alone unit containing computer, screen, operating means, memory and storage medium, and/or it may be a component in an integrated automated production facility which comprises network based client/server technology with access to intranet and to Internet.
• Fig. 7 shows a preferred implementation of the invention in a production setup of which several cells coupled together via conveyor belts (23) are part.
• a fully automatic processing system may have an integrated coating cell (24) which is part of finishing the item; in that case items may automatically be moved to a position (35) where coating of the edges is effected via nozzles/rollers (25) disposed in the coating cell.
• the nozzles may e.g. be movable and controllable.
• a more simple coating process in which no movable nozzles are required can be effected with two coating cells provided in the course of the process (24.1 and 24.2). In each of these cells, two edges are coated at a time, while items are conveyed via the conveyor belt (23).
• the invention may find application in production of objects which are made of MDF material and where high quality of the visible edges is demanded.
• the list of items is long, and the following are just examples: racks, shelves, cabinets, boxes, strips, panels, partitionings, frames etc.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Treatment Of Fiber Materials (AREA)
• Milling, Drilling, And Turning Of Wood (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Turning (AREA)
• Milling Processes (AREA)

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Citations (8)

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• 2008
  • 2008-07-10 DK DKPA200800968A patent/DK177227B1/da active
• 2009
  • 2009-05-12 WO PCT/DK2009/050108 patent/WO2010003418A1/en active Application Filing
  • 2009-05-12 CN CN200980135071.XA patent/CN102149522B/zh active Active
  • 2009-05-12 EP EP09776218.1A patent/EP2310173B1/en active Active

Patent Citations (8)

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