At present, CNC machining process can be divided into two categories according to the production batch. One is single piece, multi-variety, small batch (referred to as “small batch production”); the other is small variety but large batch (referred to as” mass production”). The small batch accounts for about 70-80% of the total output value of machining and is the main body of machining.
Why the production efficiency is several times different forthe same CNC machines? The conclusion is that the jig selected by the CNC machine tool is not suitable, so that the production efficiency of the CNC machine tool is greatly reduced. We would like to introduce 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 has a great relationship.
According to incomplete statistics, the proportion of unreasonable fixtures used in CNC machine tools in domestic enterprises is as high as 50%.
By the end of 2010, the number of CNC machine tools in China was nearly 1 million, that is to say, there were more than 500,000 CNC machine tools.
From another point of view, there is much to be done in the selection and application of CNC machine tool fixtures, because of the potential economic benefits.
Small batch production cycle = production time + workpiece processing time. Since the "workpiece processing time" of small batch production is very short, the length of the "production time" has a crucial impact on the processing cycle. In order to improve production efficiency, we must find ways to shorten the production time.
■ 3 types of CNC machine tool fixtures for small batch production.
2. Precision Combination Pliers
4. Electric permanent magnet fixture
■ 5 types CNC machine tool fixtures for mass processing
3 types of CNC machine tool fixtures for small batch production.
1. Combination fixture
Combination fixtures, also known as building block fixtures, are composed of a series of machine tool fixture components with standardized designs, different functions, and different sizes.
According to the processing requirements, customers can quickly assemble various types of machine tool fixtures like "building blocks". Since the combined fixture saves the time of designing and manufacturing special fixtures, and greatly shortens the production preparation time, 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, repeated use, energy saving and material saving, and low cost of use, so small batch processing, especially when the product shape is more complex, can give priority to the use of combined fixtures.
2. Precision Combination Pliers
Compared with other combination fixture components, the precision combination vise is actually a "combination" in the combination fixture, which is more versatile, more standardized, easier to use, and more reliable for clamping.
Therefore, it has been widely used around the world. It has the advantages of quick installation (disassembly), quick clamping, etc. Therefore, it can shorten the production preparation time and improve the efficiency of small batch production.
At present, the clamping range of precision combination flat-nose pliers commonly used in the world is generally within 1000mm. The clamping force is generally within 5000KGF
3. Glossy Fixture Base
The smooth fixture base is not widely used in China, but it is widely used in industrialized countries such as Europe and the United States.
It is actually the finished blank of the fixture base, and the positioning connection part between the component and the machine tool and the positioning surface of the part on the fixture have been processed.
Users can make special fixtures by themselves according to their actual needs.
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.
The precision combination vise here originated from developed countries such as Europe and the United States, and is a series of new vise specially designed for the characteristics of CNC machine tool machining centers.
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 Ru, iron and boron as the magnetic source and applying the principle of modern magnetic circuit.
A large number of machining practices show that the electric permanent magnet fixture can greatly improve the comprehensive machining efficiency of CNC machine tools and machining centers.
The clamping and unclamping process of the electric permanent magnet clamp takes only about one second, thus greatly shortening the clamping time.
The positioning elements and clamping elements of conventional machine tool fixtures take up a lot of space, while electro permanent magnet fixtures have no space-consuming elements, so compared with conventional machine tool fixtures, it has a larger clamping range, which is conducive to the use of CNC machine tools.
It is beneficial to improve the comprehensive processing efficiency of CNC machine tools.
5 types CNC machine tool fixtures for mass processing
Mass processing cycle = processing waiting time processing + workpiece processing time + production preparation time.
"Processing waiting time" mainly includes the time for workpiece clamping and tool change. The traditional manual machine tool fixture "workpiece clamping time" can reach 10%-30% of the high-volume machining cycle.
In this way, "workpiece clamping" has become a key factor affecting production efficiency, and it is also the key target for machine tool fixtures to tap the potential.
Therefore, special fixtures for quick positioning, quick clamping and loosening have been adopted for mass processing, and the following three types of machine tool fixtures can be given priority.
1. Hydro-pneumatic grips
Hydraulic pneumatic fixture is a special fixture that uses oil pressure or air pressure as the power source, and realizes the positioning, support and compression of the workpiece through hydraulic components or pneumatic components.
He can accurately and quickly determine the mutual position between the workpiece and the machine tool and the tool. The positional accuracy of the workpiece is guaranteed by the fixture, which greatly saves the time for 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 make it especially suitable for use in CNC machine tools, machining centers, flexible production lines, and especially suitable for mass processing.
2. Electric permanent magnet fixture
The electric permanent magnet fixture has the advantages of quick clamping, easy multi-position clamping, multi-face processing in one clamping, stable and reliable clamping, energy saving and environmental protection, and automatic control.
Compared with conventional fixtures, it can greatly shorten the clamping time, reduce the number of clamping times, and improve the clamping efficiency, so it is not only suitable for small batch production, but also suitable for large batch production.
Experience has shown that in order to improve the processing efficiency of CNC machine tools, it is not enough to select the correct CNC machine tools and fixtures, and we must also make good use of CNC machine tool fixtures. Three commonly used methods are described below.
3. Multi-station method
The basic principle of the multi-station method is to shorten the clamping time of the workpiece and prolong the effective cutting of the tool by clamping multiple workpieces at one time.
4. Group usage
Putting the same several fixtures on the same workbench can also achieve the purpose of multi-station clamping. The fixtures designed by this method should generally be standardized and manufactured with high precision, otherwise it will be difficult to meet the requirements of CNC machine tool processing.
5. Local quick change
It is to quickly change the function or use of the fixture by quickly replacing the part of the fixture of the CNC machine tool. The local quick change method greatly shortens the time for changing and adjusting the fixture, and has obvious advantages in small batch production.
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