The selection of fixtures for half of the machine tools is unreasonable

The same machine tool, why the production efficiency is several times different? The conclusion is that the fixture selected for the CNC machine tool is not suitable, which greatly reduces the production efficiency of the CNC machine tool. Through technical analysis, the improvement of the utilization rate of CNC machine tools has a great relationship with the use of fixtures.

According to incomplete statistics, the proportion of unreasonable fixtures selected by domestic enterprises for CNC machine tools is as high as more than 50% (Editor's Note: Statistics are older), which means that more than half of CNC machine tools appear due to unreasonable fixture selection or improper application. From another point of view, there is much to be done in the selection and application of CNC machine tool fixtures, because it contains considerable potential economic benefits. In order to enable gold powder to better understand the fixture, the following introduces several modern CNC machine tool fixtures.

1 Adjustable clamp

Adjustable clamps are divided into general adjustable clamps and group clamps (also called special adjustable clamps). Their common feature is that as long as the individual positioning, clamping or guiding elements are replaced or adjusted, they can be used for the processing of various parts, so that the single-piece small batch production of various parts can become a group of parts on the same fixture. mass production". After the product is updated, as long as the parts belong to the same type, they can still be processed on this fixture. Since the adjustable fixture has strong adaptability and good inheritance, the use of the adjustable fixture can greatly reduce the number of special fixtures, shorten the production preparation cycle, and reduce costs.

2 Combination clamps

The combined fixture is also called "building block fixture". It consists of a series of machine tool fixture components with standardized design, different functions and different specifications and sizes. Customers can quickly assemble various types of fixtures like "building blocks" according to processing requirements. Types of Machine Tool Fixtures. Since the combined fixture saves the time for designing and manufacturing special fixtures, the production preparation time is greatly shortened, and the small batch production cycle is effectively shortened, that is, the production efficiency is improved. In addition, the combined fixture also has the advantages of high positioning accuracy, large clamping flexibility, cyclic and repeated use, energy-saving and material-saving manufacturing, and low cost of use. Therefore, for small batch processing, especially when the product shape is more complex, the use of combined fixtures can be given priority.

3 Precision Combination Pliers

Compared with other combination fixture components, the precision combination vise is actually a "combination" in the combination fixture. Compared with other combination fixture components, it is more versatile, has a higher degree of standardization, is easier to use, and has more reliable clamping, so it has been recognized worldwide. Wide range of applications. The precision combination vise has the advantages of quick installation (removal), quick clamping, etc., so it can shorten the production preparation time and improve the efficiency of small batch production. At present, the clamping range of the commonly used precision combination flat-nose pliers in the world is generally within 1000mm, and the clamping force is generally within 5000Kgf.

It should be noted that the precision combination vise mentioned here is not an old-fashioned machine vise. The old-fashioned machine vise has a single function, low manufacturing precision, cannot be used in groups, and has a short service life. It is not suitable for CNC machine tools and machining centers. use on.

4 Electric permanent magnet fixture

The electric permanent magnet fixture is a new type of fixture designed by using new permanent magnet materials such as neodymium iron boron as the magnetic source and applying the principle of modern magnetic circuit. A large number of machining practices have shown that electric permanent magnet fixtures can greatly improve the comprehensive processing efficiency of CNC machine tools and machining centers.

The clamping and unclamping process of the permanent magnet clamp only takes about 1 second, so the clamping time is greatly shortened; the positioning elements and clamping elements of the conventional CNC machine tool clamp take up a lot of space, but the permanent magnet clamp does not have such space. Therefore, compared with the conventional CNC machine tool fixture, the clamping range of the electric permanent magnet fixture is larger, which is conducive to making full use of the CNC machine tool table and processing stroke, and is conducive to improving the comprehensive processing efficiency of the CNC machine tool. The suction force of the permanent magnet clamp is generally 147~176.4N/cm2, so it must be ensured that the suction force (clamping force) is sufficient to resist the cutting force. In general, the adsorption area should not be less than 30cm2, that is, the clamping force should not be less than 4.41kN.

In modern automated production, the application of CNC machine tools has become more and more extensive. During CNC machining, the movement of the tool or worktable is controlled by the program and carried out according to a certain coordinate position.

The following points should be paid attention to when designing CNC machine tool fixtures:

1. The origin (tool setting point) should be set on the CNC machine tool fixture.

2. The CNC machine tool fixture does not need to be equipped with a tool guide. This is because during CNC machining, the machine tool, fixture, tool and workpiece always maintain a strict coordinate relationship, and there is no need for guiding elements between the tool and the workpiece to determine the position.

3. CNC machine tools often need to process workpieces in several directions, so CNC machine tool fixtures should be open.

4. Adjustable fixtures, assembled fixtures and combined fixtures should be used as far as possible on CNC machine tools. Because workpieces processed on CNC machine tools are often produced in small batches of single pieces, fixtures with good flexibility and short preparation time must be used.

5. The clamping of CNC machine tool fixtures should be firm and reliable and easy to operate. The position of the clamping element should be fixed to prevent the element from colliding with the tool during automatic machining.