The installation base is called the place on the table of the machine - in a vice, in clamps, in squares or in its other compartments, in which the workpiece is secured, as well as this type of work, as the workpiece is based. This term refers to the fixation of the position of the workpiece by the location of the installation base.
Base Description
For example, if you are milling a bar, then its installation base will be the side part, along which the product is installed. When processing some templates, the central hole and its lower surface can act as such a basis. In other words, two parts serve as a surface for installation.
From this we can conclude that the installation base can be both the outer surface and the inner one. The bases themselves are also divided into several types. For example, if the surface is untreated, then it is called a rough base. However, there is a minus, which consists in the fact that the workpiece cannot be installed twice on the rough surface twice. Because of this, for the second processing operation and all subsequent, it is necessary to install the product on a surface that has been machined. In this case, the installation base is called finishing.
Database Options
Such a basis has a parameter, which is usually called the basing error. This term refers to any inaccuracy that arose in the size of the part itself. The reason for this is the vibrations that occur when installing the workpiece on the installation base. In addition, one more thing is required from these parts - they must ensure the correct relative positioning of the elements, and also have the most reliable fastening for the workpiece. In order to choose the right surface for such criteria, there are several rules for choice.
The choice
Firstly, you need to use draft bases only once, for the initial installation of the product. In addition, it is impossible to remove the workpiece from the machine until the finishing base for subsequent fastening is ready. This rule can only be neglected if roughing of the material is carried out, and the surface is initially relatively flat, for example, after rolling.
Secondly, as a rough installation base of the part, you need to choose a surface that has the smallest allowance. If you follow this rule exactly, the result will be that the amount of residual black on the workpiece will significantly decrease. Another important point concerns the case if it is necessary to process the part not from all sides. In such a situation, the side that has the smallest allowance should be used as the base of the draft type.
The last rule for choosing installation bases requires that the final processing of the product be carried out with an exact relative position of the elements. In other words, the processing can be carried out in several stages. But at the same time, you must always use the same version of fasteners.
Additions to the selection rules
When processing the surface in one installation, the errors of the base used, as well as the devices used for work, will not affect the accuracy of the parts. Thanks to this, it becomes possible in this case to use any plane as an installation element, regardless of whether it is machined or rough. Most often, this approach is used when an enlarged method of the technological process is used. The advantage is that it is possible either to significantly reduce processing costs, or to increase the accuracy of the devices.
If you process products on several installations, then in this case the error of both the surface and the device itself will greatly affect the accuracy of the work. From this it follows that they can only be processed when installed on the same plane, that is, on the finishing base.
One of the important requirements that is presented to the plane is that it must provide longitudinal and constant movement of the workpiece along the machine. As the base it is allowed to use the ends of the product or ledges. Compliance with this requirement is most important if there is a process of serial production of parts or just a very large batch.
Installation elements
The installation base of fixtures, machines and the assembly of some parts includes the need for such operations as basing and fastening. To perform these two procedures, the principle of different bases is used.
As for the need for fastening, that is, force contact with the surface of the machine, its need, in principle, is obvious. In order to work with maximum accuracy, it is necessary to install the workpiece so that its location is correct in relation to the working parts of the device. In addition, the installation technological base should provide continuous contact with the supports.
Another important requirement is to ensure complete immobility of the product in relation to the fixtures on the machine during work. In order to fulfill this requirement, it is necessary that the part has a mount with all the main supports. The number of such supports depends on the number of degrees of freedom that the workpiece must completely lose. Since vibrations are allowed during operation, it is necessary that the stiffness is maximum, and there is also a device at hand that will increase the vibration resistance of the material. To do this, you need to use support auxiliary and self-regulating type, together with installation bases.
Base for different types of products
In order to create a connection with such elements that have a spherical, notched and flat head, use fastening with bushings. They are connected to the holes of the housing during landing, forming a mounting surface.
If you need to fix a product that has cylindrical holes, as well as one plane perpendicular to them, it is best to use flat supports and mounting fingers of the standard type. To avoid problems during operation, in particular jamming, it is necessary that one of the installation fingers be cut off and the second cylindrical type. In this case, the installation base will meet all the requirements.
Plane misalignment
A similar problem arises if the installation base is not simultaneously measuring. In this case, the occurrence of a basing error is simply inevitable, and therefore there are rules that must be followed in this case.
The first rule is that initially it is necessary to process the surface, which in the future may become the best finishing surface for the part. This rule is based on the principle that the second and subsequent operations will always be more demanding on the process. Naturally, this requires a good foundation.
The second rule says that as a base, you can choose the surface that has a minimum error indicator relative to others.
Crankshaft Mounting Base
A crankshaft is a part that is one of the most important in an internal combustion engine. This element has parts such as necks, which during operation will experience high specific loads, since sliding friction is observed. The installation base for the crankshaft are precisely these necks. It is also worth noting that such an element will be constantly operated in conditions of variable dynamic load.
From the foregoing, the following conclusion can be drawn. The right choice of installation base, compliance with all the rules of such a choice, as well as the right approach to work in the event that an error is inevitable, is the key to a correctly manufactured part. In other words, the choice of base largely determines the quality of the final product.