The Technique of FURNITURE MAKING
Working robots
Computers are now being used very effectively to control other machines directly, with only limited human supervision or intervention. These machines are used for transporting work or raw materials, or for shaping, sanding or polishing the finished article. Efforts are currently being made to link the design and manufacturing stages electronically so that machines can make an article from an electronic drawing sent by wire. This method will be used only for very simple components for some time, but the possibilities will no doubt increase. One of the most widespread and successful computer controlled machines in the furniture industry is the CNC router. CNC means Computer Numeric Control, and refers to the programming language used to control the machine's operations. This control language consists of strings of numbers which, rather like map reference numbers, tell the machine where it is and where it is heading next. Information on the task the tool is to perform is fed into the keyboard attached to the router as a series of code numbers. Some of the more common operations, such as circle cutting, are built into the machine memory. This simplifies the programmer's task considerably, but even so a complex set of operations may require a fault - free program of up to 1000 lines in length. This operating software is expensive to produce, and difficult to debug if problems arise. One of the areas in which the present generation of
machines can be improved is in the flexibility and power of this programming, or 'operating system'.
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The hardware—the actual machinery which the software is used to control—is superficially similar to a conventional router, the differences being that the cutting head rises and falls automatically, while the workpiece is fixed to a power driven table that moves the wood past the cutter under constant control. Large machines may have mobile cutter heads in order to reduce the floor-space required for the machine. The addition of a vacuum table to the machine to hold the work down during machining reduces jig costs and improves loading times between cycles. The chief benefits of this machine are the very fine tolerances it can work to, and the consistent high speed with which it can make complicated shapes. Dimensional accuracy of the finished work is normally expected to be within 0.1 mm. Pierced and moulded chair backs are typical of the complex items that can be made. This type of machine can be fitted with several heads, so that each cycle of the main program produces two or more components. Alternatively, each cutter head may be fitted with a different type of tool, in order that the machine may perform different operations without stopping the work-cycle. This type of dual tasking is not practical using the conventional machine. Drill units can be fixed to these machines for precision boring fixing holes for flat-pack furniture kits etc.
