Portal milling machine
As portal milling machine (or Portalfräswerk ) is a milling machine referred to, in which the milling head is guided on a cross-beam between two uprights, whereby a portal is formed. The workpiece is depending on the design at a gantry drive mounted on a fixed clamping table or a span and in fixed columns corresponding to a slidable through the portal clamping table.
Portal milling machines in industrial machine size are suitable for the effective machining of large areas. They are preferred for face milling, for example, of large panels. In addition to the milling head on the crossbeam, portal milling machines often have two milling heads on the uprights, so that the sides of the workpiece can be machined at the same time in one pass.
Portal milling machines are more often used than small CNC machines with stepper motor drives for engraving or surface processing as well as the 3D creation of shapes in wood, plastics, stone and non-ferrous metals. It can also be used for dosing applications or plasma fusion cutting and CNC welding. When rapid prototyping , they are used as advertising agencies or ambitious DIY enthusiasts, schools and institutions.
Compared to their industrial "big brothers", these small systems have the decisive advantage of mobile use in dimensions of up to approx. 1500 × 1000 × 200 mm. This property makes them indispensable for many trades in terms of the variety of applications. The positioning accuracy of these 3D CNC milling and engraving units is often below 0.02 mm.
In industrial machines , due to the very rigid design, the positioning accuracy of the milling tools used is very high, up to 5/1000 mm, despite the often extreme dimensions of such machines. Accordingly, the design is also relatively insensitive to vibrations, which is an important prerequisite, especially when high dimensional accuracy, surface quality or high cutting performance are required.
Smaller CNC milling machines, on the other hand, are often not built to be sufficiently rigid, so that mechanical errors (backlash, low repeat accuracy) have to be corrected using appropriate software.
A major disadvantage of portal milling machines is the design-related limitation of the width and height of the workpieces , corresponding to the internal dimensions of the portal.