5.3 Foundation
The main function of the foundation is to support the machine and it is not allowed to have any deformation in the place where it contacts the machine. If there is deformation, the entire working status of the machine will be affected. In severe cases, the accuracy of the machine will be destroyed and the quality of the printed product will not be guaranteed. Therefore, the foundation must not be deformed. The construction of the foundation should take into account the weight of the machine. The higher the weight of the machine, the higher the capacity requirement for the foundation bearing. If the weight of the unit is W, the impact force generated during operation is F, the contact area between the supporting screw of the machine and the foundation is S, and the average surface pressure on the ground surface is P, then:
P·S>W+F P>(W+F)/S
It can be seen from the above equation that the pressure P on the foundation is inversely proportional to the contact area S. The larger S is, that is, the larger the contact area is, the larger P is. The contact area S refers to the place where the bearing of the machine comes into contact with the foundation, not the entire foundation. From the foundation point of view, the bigger the contact area, the better, and the lower the requirement for the foundation. If a large piece of rigid material is placed under the supporting screw, as shown in Figure 5.9, the contact surface between the machine and the foundation is enlarged, thereby reducing the unit pressure P that the foundation bears.
If the rigid material is too thin to function as shown in Figure 5.10, it is necessary to increase the strength of the rigid material against deformation. In addition to the properties of the material itself, the surface deformation can be resisted by increasing the thickness of the material, as shown in Figure 5.11. However, the greater the thickness of the pad, the higher the center of gravity of the machine and the poorer the smoothness of the machine, so the thickness of the material cannot be increased blindly. The larger the area of ​​the block, the smaller the unit pressure on the foundation and the lower the requirement on the foundation. The size of the foundation is directly related to the supporting screw. Generally, the supporting screw should be included. The foundation should be a single entity. It is not possible to make a foundation only under the supporting screws, but not in other non-contact areas, as shown in Fig. 12a.
In doing so, one is the poor coordination between each foundation; the second is that the contact pressure between each foundation and the ground is much greater than the contact pressure between the entire foundation and the ground, which is likely to cause greater stress in large areas. The deformation. In fact, the foundation is equivalent to a rigid cushion with a large thickness. The larger the foundation, the smaller the unit pressure between it and the ground below, as shown in Figure 5.12b.
However, with the increase of the foundation, the cost also increases. From an economic point of view, the smaller the better the foundation. The greater the volume of the foundation, the greater its ability to maintain its own inertia, and the greater its resistance to impact, thus keeping the machine in place.
The foundation is often eroded by oil, so oil-resistant materials must be used as a foundation. Some equipment also has special oil pans on the foundation. One way to do this is to prevent the oil from flowing to the entire ground, and the other is to prevent the oil from seeping into the foundation. The use of the oil pan is only suitable for machines with less oil leakage. If the oil leakage of the machine is serious, an oil cylinder (made together when doing the foundation) should be installed somewhere around the foundation so that the escaped oil can flow. In the cylinder, as shown in Figure 5.13.
Also pay attention to the level of the surface of the foundation. If the contact surface between the foundation and the machine support is not even, it will cause difficulty in finding the level. Therefore, if the underside of the support is uneven (wire support, rebar head, etc.), it should be leveled before the machine is in place.