Computer controlled automation is becoming increasingly important for production technology. Even in the wood processing industry, CNC ("computerized numerical control") machines are finding wider use. These employ the on-board computer to perform all control functions to execute the machining processes. They represent complex and integrated CNC machining centres, which execute the various machining steps on the workpiece secured into a workpiece clamp. Turning, sawing, milling, drilling, sanding or gluing – all these are performed on the wood using programmed tool motions. Conventional control elements, such as foot and hand levers or hand wheels are eliminated. The control motions are instead performed with the computer keyboard or a mouse click, while the functions and operation are monitored with the monitor. The computer controls the machining centre with the data entered to execute all feed motions and clamping processes. Manual intervention by the operator is no longer required. Using a CNC machining centre, the manufacturing operation can attain significantly higher machining accuracies and machining speeds. The frequency of defects and the risk of malfunctions is reduced. Moreover, CNC machines are highly flexible using text or graphics-based reprogramming interfaces, and can be modified with ease to accommodate the individual needs of the specific workshop. CNC technology generally establishes a close link to the design-engineering department, which can use CAD applications to directly develop and implement programmes for the CNC machine.
Due to their highly flexible uses, CNC machines are becoming increasingly indispensable for wood processing operations - for industry and workshops alike. A growing number of companies are upgrading to CNC machines in an effort to confront market demands and cost pressures. CNC machining centres are in use particularly when various wood species need to be machined, frequently also in combination with other materials, such as plastics or non-ferrous metals. Solid wood or wood materials, such as plywood, particle board or MDF panels, can be milled (CNC routers), sawed or sanded automatically and in series production. This permits the use of CNC machines to produce construction elements (doors, windows, etc.), for solid wood processing (furniture, interior design), and for panel machining. The use of CNC wood processing machinery even results in highly satisfactory and cost-effective outcomes for the production of intricate musical instruments.
CNC machining centres for wood generally consist of four units: the machine frame, the vacuum fixture with suction elements, the machining bed and the machining unit. All units can employ e-chain systems® and highly flexible cables from igus®, where they can provide maintenance-free operation and a long service-life. e-chains® are an ideal protection for cables and hoses, even against the high heat and high dynamics developed in wood processing operations.
Machine frame: The machine frame is a basic unit of the machine that houses the control panels. The machine drive is generally also located here. The other traveling units are installed with the machine frame as the foundation. Vacuum fixture with suction elements: Using the suction elements on the vacuum fixture, the workpieces are precisely located in accordance with the tool size. The vacuum fixture adjustment is controlled from the computer. This is accomplished in part with laser technology. The vacuum fixture and the suction elements can be controlled independently. Machining bed: Workpieces are clamped on the processing or machining bed for subsequent machining. Some machines are equipped with multiple machining stations that can be operated independently from one another. For instance, while the workpiece is still being machined, the workpiece is adjusted at the queued workstation. Machining unit:The CNC machine functions are centrally located in the machining unit. Various processing steps can be executed that depend on the installed tools.
The tool changer in the machining unit allows CNC machines to execute a variety of processing sequences. The tool can be changed in the background while the processing sequence is completed, facilitating time savings. Since most processing steps remove material in the form of chips, these chips are permanently vacuumed from the CNC machining centre during the process. The following are specific examples of machining processes that can be used:
Drilling is a chip generating process to create and machine cylindrical bores in workpieces, or more generally, to create or widen (bore size increases) a hole or through-hole in a solid body.
Milling refers to a chip generating process on metals, wood or plastics by means of a milling tools. This is accomplished on special machine tools, generally on a milling machine or a machining centre. In contrast to turning, the cutting motion needed to remove chips is accomplished with a rotation of the cutting tool relative to the workpiece, which is clamped in a fixed position on the machine bed. Depending on the design, feed motions can be executed in the X, Y and Z axis (also in combinations), or along the respective axis of rotation.
Sawing is a chip generating process with circular or straight-line cutting motions. Sawing is used to cut off workpieces, to cut rods and profile material to length, to cut out openings in panels, and also to cut grooves and slots. In this case, the multi-tipped tool performs the cutting motion and the feed motion.
Sanding is a chip generating production process with multi-tipped tools, whose geometrically randomized cutting surfaces are formed by a multitude of embedded sanding elements made from natural or synthetic sanding agents. These remove the material at high speeds, typically involving discontinuous contact between the workpiece and the sanding grain.
Edge gluing with laser technology involves melting a pre-defined surface of the edge material by means of laser rays. The molten edge material penetrates the workpiece surface when the edge material is pressed against the pressure zone, forming a fully bonded contact between the workpiece and the edge material as the edge material cools. Accordingly, there is no visible gap between the workpiece and the edge material. The CO2 laser process and the diode laser process have proven to be effective for edge gluing. Both processes employ an edge material as the actual glue surface and a co-extruded functional surface made from a polymer. This functional surface is only a few tenth of a millimetre in thickness and represents the "anchor" for the edge material to the workpiece as it melts, penetrates and cools.
CNC machining centres primarily employ e-chains®, e-tubes and igus® PVC cables. Because the dimensions of CNC machinery for the wood industry differ greatly, and are generally based on the size of the wood pieces to be processed, these three igus® product groups are requested in many versions.
energy chain for vacuum fixture adjustments2
energy chain for suction elements3
Z axis - various cables to supply the tool4
Y axis - energy chain for transverse travel - control, data, motor cables and pneumatic hoses5
X axis - energy chain for longitudinal travel - control, data, motor cables and pneumatic hoses
E2 and E4 e-chains® are used most frequently. But small CNC machining centres also use single and two part E2 mini and E2/000 chains. Various chain types are typically in use, since the individual travels to supply the X/Y/Z axis and the vacuum fixture with energy and air feature greatly differing travel lengths and fillings. The Z axis typically needs several energy chains, since these usually involve several applications. Each vacuum fixture uses one energy chain (primarily filled with pneumatic hoses). This can either involve installing e-chains® on the machine exterior or within the machine bed for protection.
E2 e-tubes are a particularly suitable candidate for use in wood processing CNC machinery, since they provide effective protection against chips. By covering the cables, they are also visually very appealing due to their uniform appearance. They are easy to assemble, cost-effective, while their good ratio of inner to outer dimension facilitates a very space-saving installation into CNC machining centres.
The twisterband is used when CNC machines need special rotational motions in confined spaces, such as for edge cutting. The twisterband facilitates a process-capable energy supply to a rotating milling spindle without wear and the need for maintenance intervention. In comparison to slip ring solutions, twisterband solutions are more cost-effective overall, have less wear and require less installation space.
All e-chains® primarily have two advantages in comparison to conventional PMA hoses for CNC machines: They are visually more appealing and provide a "clean" solution for the energy supply system. The machine operator is no longer distracted by freely hanging PMA hoses.
chainflex® PVC cables are particularly well suited as fillings for e-chains® on CNC machining centres. These are used for the interior and are not exposed to contact with oil. They are primarily used in unsupported configurations and do not need to address specific loads. chainflex® PVC cables are therefore a very good and cost-reducing alternative as replacements for competing cables with PUR or TPE cables in CNC wood processing machinery. CA PU hoses are also used in addition to PVC cables.
igus® therefore provides an assortment of customised energy supply solutions for any CNC machining centre. However, igus® not only supplies e-chains®, cables and bulk connectors, but also harnessed and fully integrated systems, such as readycable® or readychain®. These complete systems consist of ideally matched components and represent the best possible solution for CNC wood processing machinery. Other igus® products are available in addition to energy supply systems. For machine doors, we recommend drylin® linear plain bearings, which compel with their smooth, maintenance-free and lubricant-free travel. Due to their dry-running properties, they are particularly dirt-resistant and will work trouble-free even when exposed to large chip volumes. We invite you to get a first-hand impression of the quality and product variety supplied by igus® GmbH at one of the trade fairs for the wood industry, such as LIGNA, Xylexpo, WoodMac China, CIFM/ interzum Guangzhou.