1. Types of bottom plates and bases
Vertical machining centers mainly use base plates. In addition to the basic base plate, horizontal machining centers also have single-sided bases, double-sided bases and four-sided bases.
In order to accommodate different part sizes, horizontal machining centers also use six- and eight-sided bases. In Figure 2, the areas marked in darker orange on the part are the surfaces that can be treated.
2. Types of bottom plates and base mounting surfaces
The installation methods of the bottom plate and base clamp mounting surface include T-shaped groove shape, bolt hole shape, reference hole shape, etc. In addition, in actual processing, in order to make the precision of the machining center and the precision of the fixture mounting surface as perfect as possible, there is also a form of self-processing.
Figure 3 Advantages and Disadvantages of Typical T-Shaped Slots, Bolt Holes, and Reference Holes
Each machine tool has its own characteristics, such as the inclination of the floor in the factory where the machine tool is located, the inclination of the spindle after many years of use, etc. The remaining material retained by the fixture mounting surface can be processed to accommodate the individuality of the machine tool, so that the fixture mounting surface can be customized with greater precision. There is also a form of disassembly and assembly of tools and parts outside the machine tool: rapid tool change.
3. Determine size and positioning method
When choosing a base plate or base, you should first confirm the size and positioning method in advance. The basic dimensions of horizontal machining centers are 400X400, 500X500, 630X630 and 800X800. Depending on the machine tool manufacturer, there are also sizes such as 300X300, 1000X1000, and special sizes such as 550X550 are also produced by machine tool manufacturers. The dimensions of vertical machining centers vary from one machine tool manufacturer to another, and there are no specific rules dictating the dimensions. Each machine tool manufacturer has its own prescribed dimensions for the machine tool bench. Please refer to the machine tool manual.
Figure 4
Positioning the bottom plate and base of a horizontal machining center generally uses bench blocks installed in the X and Y directions. The base plate and base are positioned by adjusting the bench block. The position of the workbench support block is generally set at the 0° and 270° orientations of the machine tool workbench. The position of the workbench support block also varies depending on the machine tool manufacturer. The center of the worktable of a vertical machining center is usually equipped with a keyway. Position the X direction of the base plate and base through the keyway, then position the Y direction of the base plate and base through the T-shaped slot.
However, not all T-shaped slots can be positioned precisely. Depending on the machine tool manufacturer, there are usually only one or two T-shaped slots with positioning function in the machine tool.
4. Confirm the maximum load of the machine tool
Firstly, confirm the maximum load capacity of the machine tool, and secondly, confirm the total weight of the workpiece, fixture, base plate and base. The total weight must not exceed the maximum load capacity of the machine tool. There are also designers who calculate the weight of the part, base plate and base, but forget to calculate the weight of the fixture, which cannot be ignored.
Figure 5
If the total weight exceeds the maximum load of the machine tool, you can choose to reduce the thickness of the base plate, reduce the thickness of the base mounting surface, or make the base hollow to reduce the total weight.
5. Confirm the base height and maximum rotation diameter
The maximum height and maximum rotating diameter of the machine should be confirmed in advance when selecting the base plate and base. Especially for horizontal machining centers, the maximum rotating diameter should be confirmed. Generally, when the base size is 400X400, the maximum rotation diameter is φ630. When the base size is 500X500, the maximum rotation diameter is φ800. The two sizes above are the most common sizes and there are no clear requirements for using a base of this size. When the collet is clamping the workpiece up and down, the top of the collet (the top of the bolt in the image below) should be within the maximum turning diameter.
Figure 6
six,Confirmation of extent and timing of treatment
Confirm in advance whether the machining range of the machine tool (the range of motion of the spindle) covers all parts of the workpiece that need to be processed. Especially when using a milling cutter to process the surface, when retracting the tool, it should be considered in advance when designing whether the spindle stroke can completely withdraw the tool from the workpiece . If tool retraction is not taken into account, it will be more. difficult to ensure surface accuracy. When the cutter leaves the workpiece, the minimum distance between the cutter and the workpiece must be greater than 10 mm, that is, the cutter must completely leave the workpiece area.
Figure 7
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