How to choose a reasonable fixture for machine tools!
Why does the production efficiency of the same machine tool differ by several times? The conclusion drawn is that the fixture selected for CNC machine tools is inappropriate, which significantly reduces the production efficiency of CNC machine tools. How to improve the utilization rate of CNC machine tools? Through technical analysis, the use of fixtures is closely related.
According to incomplete statistics, the proportion of domestic enterprises using unreasonable fixtures for CNC machine tools is over 50% (note from the editor: the statistical data is relatively old), which means that more than half of CNC machine tools have experienced "idle work" due to unreasonable fixture selection or improper application; From another perspective, there is much to be done in the selection and application of CNC machine tool fixtures, as they contain significant potential economic benefits. To help the gold powder better understand the fixtures, the following are several modern CNC machine tool fixtures.
1, Adjustable fixture
Adjustable fixtures are divided into two categories: universal adjustable fixtures and group fixtures (also known as specialized adjustable fixtures). Their common feature is that as long as individual positioning, clamping, or guiding components are replaced or adjusted, they can be used for the processing of multiple parts, thereby transforming the single piece small batch production of multiple parts into a group of parts on the same fixture for "batch production". After product updates, as long as the parts belong to the same type, they can still be processed on this fixture. Due to the strong adaptability and good inheritance of adjustable fixtures, the use of adjustable fixtures can significantly reduce the number of specialized fixtures, shorten production preparation cycles, and lower costs.
2, Combination fixture
Combination fixtures, also known as "block type fixtures," are composed of a series of standardized design, different functions, and different specifications of machine tool fixture components. Customers can quickly assemble various types of machine tool fixtures according to processing requirements, like building blocks. Due to the combination of fixtures saving time in designing and manufacturing specialized fixtures, the production preparation time is greatly shortened, effectively shortening the small batch production cycle and improving production efficiency. In addition, combination fixtures also have advantages such as high positioning accuracy, large clamping flexibility, cyclic reuse, energy-saving and material saving in manufacturing, and low operating costs. Therefore, for small batch processing, especially when the product shape is complex, the use of combination fixtures can be prioritized.
3, Precision combination flat nose pliers
Precision combination pliers actually belong to the "assembly" of combination fixtures. Compared with other combination fixture components, they have stronger universality, higher standardization, easier use, and more reliable clamping. Therefore, they have been widely used worldwide. Precision combination flat nose pliers have the advantages of fast installation (disassembly) and quick clamping, which can shorten production preparation time and improve small batch production efficiency. At present, the commonly used precision combination flat nose pliers in the international market generally have a clamping range of less than 1000mm and a clamping force of generally less than 5000Kgf.
It should be noted that the precision combination pliers referred to here are not old-fashioned machine added pliers. Old style machine added pliers have a single function, low manufacturing accuracy, cannot be used in groups, and have a short service life, making them unsuitable for use on CNC machine tools and machining centers.
4, Electric permanent magnet fixture
Electric permanent magnet fixture is a new type of fixture designed using new permanent magnet materials such as neodymium iron boron as magnetic sources and modern magnetic circuit principles. A large number of machining practices have shown that electric permanent magnet fixtures can significantly improve the comprehensive machining efficiency of CNC machine tools and machining centers.
The clamping and loosening process of the electric permanent magnet fixture only takes about 1 second, greatly reducing the clamping time; The positioning and clamping components of conventional CNC machine tool fixtures occupy a large space, while electric permanent magnet fixtures do not have these space occupying components. Therefore, compared with conventional CNC machine tool fixtures, electric permanent magnet fixtures have a larger clamping range, which is conducive to fully utilizing the workbench and machining stroke of CNC machine tools, and improving the comprehensive machining efficiency of CNC machine tools. The suction force of the electric permanent magnet fixture is generally between 147~176.4N/cm2, so it is necessary to ensure that the suction force (clamping force) is sufficient to resist 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 increasingly widespread. During CNC machining, the movement of the cutting tool or worktable is controlled by a program and carried out according to a certain coordinate position.
When designing CNC machine tool fixtures, attention should be paid to the following points:
1. The origin (tool alignment point) should be set on the CNC machine tool fixture.
2. CNC machine tool fixtures do not require the installation of tool guide devices. 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 to determine the position between the tool and workpiece.
3. CNC machine tools often require machining of workpieces in several directions, so CNC machine tool fixtures should be open.
4. Adjustable fixtures, assembly fixtures, and combination fixtures should be selected as much as possible on CNC machine tools. Because the workpieces processed on CNC machine tools are often produced in small batches, flexible fixtures with short preparation times must be used.
5. The clamping of CNC machine tool fixtures should be firm, reliable, and easy to operate. The position of the clamping element should be fixed to prevent collision between the element and the tool during automatic machining.
