Joinery machine
Joinery machines are CNC- controlled wood cutting systems. The first, still mechanically controlled, system was developed by Prefabricated House Weiss and Fezer in 1963. In 1984 the first actually computer-controlled joinery system P8 was developed by Hans Hundegger Maschinenbau GmbH.
Working method
Joinery machines process the timber that the carpenter needs to build a house in log or timber frame construction (timber frame construction, half-timbered construction) or a roof truss. The carpenter constructs the house or the wooden structure with a joinery program (e.g. cadwork , TrimFox, S & S, Dietrichs, Sema ) according to the specifications of the architect or structural engineer . As a rule, this data is then transferred to the computer of the joinery machine. In the meantime, manufacturer-independent data interfaces such as B. BTL used by most CAD and machine suppliers. This computer contains software that controls the processing of each individual component. The latest software offers the operator extensive options for intervening in component optimization and alignment as well as in tool selection.
Depending on the company structure, modern beam machines can be used in various sizes and designs, depending on the type and design.
Most manufacturers offer the possibility of equipping the desired systems in a modular system as required and expanding them if necessary, so that any equipment variant is possible from the pure cutting saw to the fully equipped joinery machine. Almost all processing and connections that occur in timber construction are to be made with joinery systems. Even free profiles and decorations can be designed in CAD or by the machine operator himself.
Intelligent multi-processor controls enable an efficient workflow without pre-sorting wood. The timbers can be entered and called up in any order, processed by the machine and automatically debited from the timber list. Marking and writing devices or label printers enable the components to be identified so that they can be loaded and assembled correctly.
The components are removed piece by piece from cross conveyors or trestles, aligned in parallel and conveyed onto the machine table. The length of the raw wood can be determined fully automatically with laser measuring devices or with the intake gripper. With regard to the determined timber length, the machine operator is shown an optimization suggestion from the timber list in order to minimize the waste that occurs as much as possible. The wood cross-section is also automatically checked for width and height and the machine is stopped in the event of deviations outside the preselected tolerance. This enables precise machining without manual cross-section correction. If the component is incorrectly positioned, it is automatically folded over. It is achieved that z. B. pegs are always exactly in the middle of the component or mouths have exactly the same depth on both sides.
The workpiece is then usually fed to the respective unit (sawing, milling, marking, ...) and processed. The components or workpieces are transported using various transport systems such as B. Gripping and guide car. With these, the necessary machining precision can be achieved even with twisted or crooked wood.
The waste and short good parts are partially automatically separated and transported out on separate conveyor belts.
State of the art
The latest generation of joinery machines can approach the components without restriction on six sides and process them at all angles and inclinations. Thanks to this processing on the reverse side, turning or the second processing cycle is no longer necessary, even with large components. This not only saves time, it also enables machining with absolute precision and accuracy.
The heart of a machine can, for example, be a six-axis unit with twelve kW of power, a speed range from 0 to 12,000 rpm and a 16-fold tool changer. The automatic tool holder enables saw blades, drills, end mills, disc milling cutters, dovetail milling cutters, cylindrical milling cutters and marker pens to be changed in a matter of seconds.
Tools
Saws
All types of saw cuts, such as shifter, hex, tapering and miter cuts at every angle, every inclination and in all lengths, are carried out fully automatically and with millimeter precision using saw spindles or under-table swivel cross-cut saws.
Fillets, trimmings and grooves are possible in any length. Shelf grooves can be machined in any width and at any angle. Automated edging and 5-axis machining enable almost every conceivable processing of the desired workpiece.
Milling
In order to increase the flexibility of the joinery machines, five-axis milling units are increasingly being used. With an additional inclination axis, they can also carry out milling for rising mouths, inclined holes, conical dovetail pins on the shifter, trimming and grooving, etc. Modern milling units can be rotated a full 360 °, mounted horizontally and vertically and process the components according to the input and the required and available tools on all four component sides and on the front side.
Finger and cylindrical milling cutters are used. End mills are used to create holes, protrusions and profiles, and cylindrical milling cutters to work out protrusions, trimmings, grooves, tenons and mouths.
Special dovetail cutters also enable conical dovetail connections to be made . The dovetails can be made parallel or conical, with or without a shoulder. The advantage of five-axis machining becomes particularly clear here. Only in this way can such complicated wood connections , such as conical dovetail tenons on the shifter , be produced economically.
With special tools, traditional, otherwise extremely complex processes such as dovetail and Tyrolean lock can also be produced efficiently and precisely.
Through the use of longitudinal and transverse groove cutters, not only adjusting board grooves, but also grooves in the longitudinal direction of the component, can be made either with a saw blade or a side milling cutter.
Automatic tool changers can be installed in order to optimize the machining time for particularly complex machining operations or many very different components . Their magazines hold the different tools required and change them depending on the requirements of the component to be processed. In this way, downtimes due to frequent, time-consuming manual tool changes can be minimized.
Drill
In addition to the conventional simple drilling rigs, some of which are also mounted on multiple axes, multiple drilling rigs are also often offered. Multiple drilling rigs are particularly advantageous when building log houses , where they can be used for all types of drilling. Various, recurring drilling patterns can of course also be saved as a macro and called up at any time. The computer-controlled working stroke enables all kinds of blind holes, countersinks and ring dowel milling.
In order to avoid tearing out holes, they can be drilled from two sides. The high level of precision that is common today results in tear-free through holes. Alternatively, so-called splinter wood can be used. The splinter wood consists of a counter wood which is guided on a linear guide opposite the drilling unit and which is pressed against the wood with a pneumatic cylinder .
Slot machines
For load-bearing structures, connection or connecting plates, weld-on plates and connections to load-bearing nodes, slots of various sizes and depths are required. Slotted chains of the required sizes can be mounted on the corresponding units. Since the processing widths of the latest generation of systems from the leading manufacturer already reach up to 1250 mm and a particularly precise execution is essential for these processing operations, guided slotting machines are used. When slitting through, the sword is automatically fixed on the opposite side and the wood is continuously moved lengthways. This prevents the slot from running out due to heat-related deformation of the tool.
Edging and spreading
Since most common five-axis joinery systems can only be processed on five sides, the components have to be folded over. Since it is absolutely necessary for the precise further processing of the components to be carried out exactly in the longitudinal axis, the bars are partially folded over automatically. This is done pneumatically by means of gripper jaws mounted on a rocker - in the ideal case hydraulically fixed because of the higher contact pressure and precisely positioned in 90 ° steps. As an alternative to this, some manufacturers offer fully automatic measurement of the already half-machined component after edging, which enables manual turning and ensures greater component accuracy.
After processing in the individual workstations is completed, the components are pushed onto subsequent cross conveyors or trestles with ejectors.
Advantages and disadvantages
The main advantages of such systems are their accuracy and processing speed. Only one person and a forklift or overhead crane are required for the beam .
Joinery systems are an enormous gain for carpentry and timber construction as a whole. They enable the extremely precise, quick and economical production of new and traditional constructions, but of course they do not replace solid knowledge of sensible and functioning wooden constructions. The machine does not recognize knots, resin pockets or other wood defects . It also does not react to splintering. Like any machine, it is still dependent on the technical expertise and knowledge of the operator. When it comes to accuracy, the conventional manual joinery by trained staff can definitely compete with the joinery system, since very precise results can be achieved with today's hand machines with the help of guide rails and precision gauges. However, this requires a very high level of personnel and time.
The main disadvantage is the high investment cost, depending on the equipment. The purchase price of a new machine starts at around 80,000 euros with the basic equipment and is therefore not profitable for every carpentry company. However, the large number of system variants offered today makes individual adaptation to the respective operational and economic circumstances ever easier. In the meantime, joinery systems are also offered especially for smaller carpentry businesses, which already enable 5-axis machining at a moderate price.
In some cases, special construction measures are necessary for chip disposal, which, especially with entry-level machines, disproportionately increase the investment amount. Alternatively, machines with above-ground chip disposal are available.
In order to make the benefits and advantages of the most modern joinery systems accessible to smaller companies, joinery centers have been established all over Europe in recent years. In these joinery centers, some of which are run jointly by several carpentry companies, the wooden components ordered by the carpenters are processed on a subcontract basis without being in competition with them. Even the small carpentry business can use the existing know-how without having to take excessive economic risks. Associations of carpenters such as B. the "Association of High-Tech in the Carpentry Trade" and various professional associations act as interest groups for machine manufacturers, software providers, wood suppliers and authorities or offices.
literature
- Target-oriented business process management to promote the profitability of beam processing centers . Doctoral thesis, Department of Civil Engineering at the University of Kassel, April 2002
- Timber Construction Manual , Series 0 Part 2; Information service wood
- Timber Construction Manual , Series 1 Part 1; Information service wood
- Timber Construction Manual , Series 2 Part 3; Information service wood
Web links
Individual evidence
- ↑ Christoph Schindler: An architectural periodization model based on manufacturing criteria, illustrated using the example of timber construction . Self-published, 2009, ISBN 978-3-03302322-2 ( google.de [accessed on September 6, 2019]).