Do you know the common sense of selecting and using CNC machine tool fixtures?

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. The following introduces the reasonable selection and application of CNC machine tool fixtures.
How to improve the utilization rate of CNC machine tools? Through technical analysis, the use of fixtures is closely related. According to incomplete statistics, more than 50% of domestic enterprises use unreasonable fixtures for CNC machine tools. By the end of 2018, the number of CNC machine tools in China was nearly one million, which means that more than 500000 CNC machine tools had 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.
Small batch production cycle=production (preparation/waiting) time+workpiece processing time. Due to the short processing time of small batch production, the length of production (preparation/waiting) time has a crucial impact on the processing cycle. To improve production efficiency, it is necessary to find ways to shorten the production (preparation/waiting) time.
1. Below are three types of CNC machine tool fixtures that can be prioritized for small batch production:
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.
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.
Smooth fixture base
Smooth fixture bases are not widely used in China, but they are widely used in industrialized countries such as Europe and America. It is actually a precision machined blank of the fixture base, and the positioning connection part between the components and the machine tool, as well as the positioning surface of the parts on the fixture, have been precision machined. Users can manufacture specialized fixtures according to their actual needs. 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. The precision combination flat pliers referred to here are a series of new flat pliers designed specifically for the characteristics of CNC machine tools and machining centers, originating from industrialized countries such as Europe and America. These products have the characteristics of large clamping flexibility, high positioning accuracy, fast clamping, and can be used in groups, making them particularly suitable for use in CNC machine tools and machining centers.
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 machine tool fixtures occupy a large space, while electric permanent magnet fixtures do not have these space occupying components. Therefore, compared with conventional 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 15-18Kgf/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 450Kgf.
2. CNC machine tool fixtures suitable for mass processing
Large batch processing cycle=processing waiting time+workpiece processing time+production preparation time. "Processing waiting time" mainly includes the time for workpiece clamping and tool replacement. The traditional manual machine tool fixture can achieve a workpiece clamping time of 10-30% of the large-scale processing cycle, making workpiece clamping a key factor affecting production efficiency and a key target for machine tool fixtures to tap into their potential. Therefore, it is advisable to use specialized fixtures for rapid positioning and quick clamping (loosening) in large-scale processing. The following three types of machine tool fixtures can be given priority consideration:
Hydraulic/pneumatic fixtures
Hydraulic/pneumatic fixtures are specialized fixtures that use oil pressure or air pressure as the power source to position, support, and compress workpieces through hydraulic or pneumatic components. Hydraulic/pneumatic fixtures can accurately and quickly determine the mutual position between the workpiece, machine tool, and cutting tool. The positional accuracy of the workpiece is guaranteed by the fixture, resulting in high machining accuracy; The positioning and clamping process is rapid, greatly saving time in clamping and releasing the workpiece; At the same time, it has the advantages of compact structure, multi station clamping, high-speed heavy cutting, and automatic control. The above advantages of hydraulic/pneumatic fixtures make them particularly suitable for use in CNC machine tools, machining centers, and flexible production lines, especially for large-scale processing.
Electric permanent magnet fixture
The electric permanent magnet fixture has the advantages of fast clamping, easy implementation of multi station clamping, multi face processing in one clamping, stable and reliable clamping, energy conservation and environmental protection, and automatic control. Compared with conventional machine tool fixtures, electric permanent magnet fixtures can significantly shorten clamping time, reduce clamping frequency, and improve clamping efficiency. Therefore, they are not only suitable for small batch production, but also for large-scale production.
Smooth fixture base
The smooth fixture base can effectively shorten the manufacturing cycle of specialized fixtures, reduce production preparation time, and thus overall shorten the mass production cycle, improving production efficiency; At the same time, it can reduce the manufacturing cost of specialized fixtures. Therefore, the smooth fixture base is particularly suitable for large-scale production with tight cycles.
Reasonably use fixtures to tap into the potential of equipment
Experience has shown that in order to improve the machining efficiency of CNC machine tools, simply selecting the right CNC machine tool fixture is not enough, and efforts must also be made to make good use of CNC machine tool fixtures.
3. Here are three commonly used methods:
Multi station method
The basic principle of the multi station method is to shorten the unit clamping time and extend the effective cutting time of the tool by clamping multiple workpieces at once. Multi station fixture refers to a fixture with multiple positioning and clamping positions. With the development of CNC machine tools and the need for users to improve production efficiency, the application of multi station fixtures is increasing. Multi station design is becoming increasingly common in the structural design of hydraulic/pneumatic fixtures, combination fixtures, electric permanent magnet fixtures, and precision combination pliers.
Group usage method
Placing the same fixtures on the same workbench can also achieve the goal of "multi station" clamping. The fixtures involved in this method should generally undergo standardized design and high-precision manufacturing, otherwise it is difficult to meet the requirements of CNC machine tool processing. The group use method can fully utilize the stroke of CNC machine tools, which is beneficial for the balanced wear of machine tool transmission components; At the same time, the relevant fixtures can be used independently to achieve multi piece clamping, and can also be used together to achieve large-sized workpiece clamping.
Local quick change method
The local quick change method is to quickly replace the local parts (positioning elements, clamping elements, tool setting elements, and guiding elements) of the CNC machine tool fixture, in order to achieve the goal of quickly changing the function or usage of the fixture. For example, the quick change combination flat nose pliers can change the clamping function by quickly changing the jaws, such as changing from clamping square materials to clamping bar materials; It is also possible to change the clamping method by quickly replacing the clamping components, such as changing from manual clamping to hydraulic clamping. The local quick change method significantly shortens the time for replacing and adjusting fixtures, and has obvious advantages in small batch production.