Structural features of CNC machine bed castings:
Although there are many types of CNC machine bed castings, from the perspective of casting process, there are mainly the following features in the structure:
1) The basic parts of the CNC machine bed castings are box-shaped structures, and a lot of reinforcing ribs are added, which makes the structure of the bed castings more complicated. When casting, more cores are needed, and core supports are often used to fix the core; the gas generated by the core during casting is difficult to remove, and defects such as pores and blisters are easily generated.
2) Some parts on the bed castings, such as the guide surface, the shaft hole and the T-slot (after increasing the machining allowance), are thicker, except for the shrinkage and shrinkage, and the thickness of the cast iron. It is more sensitive, and it is easy to make the structure loose, the graphite is coarse, the hardness is low, and it is not wearable. When the thickness of these portions is too large to the surrounding connecting wall, defects such as cracks are likely to occur.
3) Some castings subjected to oil pressure and cutting fluid pressure are required to have high airtightness and no leakage is allowed.
4) Due to the development of cutting machining to automation, high speed and strong cutting, the emergence of CNC machine tools has caused some changes in the casting structure of CNC machine bed, which brings some problems in the casting process. Such as:
Due to the loading of the numerical control device, there are many wires in the casting of the box, and it is necessary to provide holes in the wall and the ribs of the bed for wiring, and the positions of the holes are not necessarily located at positions where the core exhaust is easily disposed. In addition, since these holes weaken the strength and rigidity of the box, cracks are easily generated at the edges thereof, and it is often necessary to set the ribs and the ribs to be reinforced, and it is often necessary to reinforced the ribs and the ribs to make the structure more complicated. In addition, the number of pallets to be cut will also increase, which will make the contour size of large machine tool castings larger.
On the basis of analyzing the defects and locations of large-scale machine tool castings, the technicians try to design reasonable structures to avoid defects.