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In most machining areas, technical designers and production engineers often have to connect to a variety of different parts and require such connections to be disassembled. The use of screw-threaded connections is the most common solution.
Most threads are now processed using conventional tapping and molding methods, especially for long chips and high rigidity, and there is often a risk of cutting the tool due to chip wedges when machining deep threads. In addition, spurious chips may also cause a lot of stops Machine time, in order to avoid cutting the tool, you must manually remove the chip. In the processing time, this phenomenon can not be underestimated. In addition to technical considerations, the intensification of international competition has forced factories to improve the manufacturing process, including cost reductions in every possible way.
Cold extrusion may be a cost-effective and safer alternative to tapping for almost 70% of the material used in the industry (at least 7% stretch). Cold extrusion in the processing strength of 1000 N / mm2 within the steel, stainless steel, aluminum Alloy (silicon content less than 12%) and soft copper alloy and other materials have outstanding performance.
In the cold extrusion process, the tool is screwed into the core hole. The material flows into the groove of the tap, thereby forming a characteristic thread profile. Therefore, cold extrusion is a transfer process that does not produce chips. It is much easier to clean up the threads and will not Lead to chip processing costs. In addition, in this way does not produce in the deep thread due to the chip wedge and cause the tool fracture. In the traditional tapping process, the core aperture is equal to the diameter of the pre-drilling, and in the cold extrusion process core hole diameter in the extrusion process
form. Therefore, the characteristics of the cold extrusion thread are different from tapping. Since the saddle has a high cold toughness, this does not have a negative effect on the thread. In order to obtain the final extruded thread, and in order to prevent the tool from being wedged, with the molding method Compared to the extrusion drilling diameter must be greater than the manufacturer recommended.
As with various transfer processes, effective lubrication is of great importance for cold extrusion. The conventional constraints on the use of variable oil for lubricating oils in most applications are no longer present today. For modern tool coatings,
It becomes no longer needed. Today, a variety of cold extrusion tapes are used in conventional machining centers that use cooling lubricants or even at least lubricated.
In contrast to conventional tapping processes, high-speed accompanying high-production safety can also be achieved for cold extrusion because there is no chip flow against the feed direction, especially when processing blind holes. For materials with high deformability, such as aluminum or structural steels, The service life of the cold extrusion workpiece can greatly exceed the life of the tapping process. These two facts mean shortening the production cycle time and saving the user costs.
In the cold extrusion process, the tap will be imported into the thread. As the thread is not cut out, but the formation of, so there will be no failure. In the case of cold extrusion, poor quality threads are produced, resulting in very little waste. Dimensionality is limited only by the size At that time the impact of tool wear. Under normal conditions, wear is gradual and the production process can be controlled by torque regulation or power control. During the extrusion process, the sides of the thread are smooth and the material fibers are joined together, rather than being cut off.
The fibers are continuous and hardened during the extrusion threading process, both of which ensure that the thread strength of the cold extrusion is significantly higher than that of the conventional machining. The structure of the cold extrusion tap is completely different from that of the conventional tap. In order to make the workpiece material Deformed in a very smooth and simple way, the cross section of the tool uses a special polygon outline. The cold extrusion tap has no slots because the thread is formed without any chip removal. The advantage of this particular structure is that, compared to conventional tap, The entire tool structure of the cold extrusion tap is more robust and can be machined under unfavorable conditions. Some cold extrusion tapes have narrow lubricated grooves. Their introduction is for specific materials and deep hole machining, in which case they can assist in the distribution of lubrication Liquid, but will not have any negative impact on the stability of the extruded tool.
One of the great advantages of cold extrusion tapes and cold extrusion processes is that blind holes and vias can be machined in a variety of materials using only one tool. In this way, the tool cost is reduced because it is not necessary to use a different tool. Compared with the traditional cutting process, the cold extrusion thread Processing has many important advantages. In the planning stage of the new production process, the traditional threading process must be carefully used, since cold extrusion is usually a good alternative to conventional thread processing.