Deep-hole machining of shotgun barrels

Shotgun barrel shotgun is not only a product design benchmark, but also a process benchmark for processing various sizes of magazines and barrels. Therefore, the quality of shotgun barrels directly affects the performance of the whole gun. According to the traditional military product processing technology, the shotgun barrels are processed and manufactured using deep-hole low-speed reaming, and the machining allowance is divided into rough-joint, semi-finished hinges, precision hinges and other multiple processing, resulting in barrel processing. The productivity is low and the reject rate is high. Carbide reamers are now used for high-speed reaming gun barrel boring processing methods, and have been applied in production. 1 The method and method of deep hole reaming of gun barrel The method of deep hole reaming of gun barrel The following two kinds of movement are usually used when the gun is being machined: The reamer rotates with the spindle, and the workpiece does not rotate. Only axial feed; the workpiece rotates with the spindle, the reamer does not turn, only the axial feed. The two methods have their own advantages and disadvantages. The first is the first method, which facilitates the clamping of workpieces and can simultaneously clamp 6 to 8 barrels at a time. The machine tool structure is simple. Therefore, it is widely used; followed by the second method. This kind of structure is easy to make the center of the barrel and the tool center coaxial, but the machine vibration during the work is large, and limited by the machine structure, only one or two guns can be installed at a time. tube. Deep-hole speed reaming methods There are two methods for deep-hole high-speed reaming: push-hinge method—the reamer pushes the rifle; the pull-hinge method—the reamer pulls over the rifle. As shown in Figure 1 ~ Figure 2.

Figure 1 push hinge

Figure 2 Pulling hinge

When the hinge is pushed, the front cone of the knife is the cutting edge. The machining and the sharpening of the cutter are more convenient. The cutter rod passes through the hinged gun and its diameter can be slightly larger. However, because the shank bears axial pressure and torque, its pressure can cause the shank to bend and scratch the surface of the processed rifle. After the reaming is completed, the reamer needs to be withdrawn from the barrel in order to re-seize. In this case, the surface of the processed barrel may be damaged, or after the reaming is completed, the reamer is removed and then the tool shaft is withdrawn from the barrel. , And then install the reamer, which will increase the auxiliary time, so that the reaming method is more suitable for low-speed reaming. When the hinge is pulled, it will bear the axial tension and torque, and will not bend. After machining, the reamer has pulled out the gun barrel. When the clamp is newly installed, the machined surface will not be damaged. Chips are ejected through the revolving barrel and the chip removal conditions are more favorable. However, the cutting edge of the reamer is close to the shank and grinding is difficult. After each barrel has been articulated, the reamer must be removed to reinstall and process it, resulting in an increase in auxiliary time. Therefore, the reaming method is suitable for low speed reaming and high speed reaming. 2 gun barrel gun deep hole reaming process characteristics The main technical parameters of the shotgun barrel gun rifle: diameter Ø18.4 +0.20mm; roughness Ra1.6μm; full-length 460 ~ 800mm; gun straightness Ø0. 20mm. Through these technical parameters, we can see that the processing technology of the gun barrel is poor, and the barrel gun barrel is processed according to the traditional processing technology—the deep-hole low-speed reaming process. The main process features are: small amount before cutting, low productivity, and cutting. Velocity v=5.5-8 m/min, feed rate f=0.10-0.15 mm/r, depth of cut ap=0.05-0.25 mm. If the machining allowance is 1mm, it takes 5-6 cutters to reach the dimensional accuracy. The length of the barrel is calculated as 760mm, and the time for one pass will reach 35-45min. After high-speed reaming, high precision can be achieved, usually up to IT7 ~ IT8, surface roughness up to Ra1.6μm, but the need to use vegetable oils such as soybean oil for lubrication, can guarantee. Because of some defects in the tool manufacturing process, such as: the roughness of the cutting edge, the edge is not sharp enough, the straightness of the reamer, the cutting angle and the matching of the processed material and other factors, will make the inner surface of the gun Groove, reaming hole after the aperture enlargement or reduction, oval hole, reamer wear fast, knife edge chipping, straight hole in the reaming hole and other block. Low-speed hinges have small margins and long working hours. Therefore, it is necessary to ensure that each cutting edge of the cutting tool must participate in cutting. This requires the operator to perform boring on the reamer. This is a technical and empirically demanding operation. At the same time, it also needs to make high-precision knife sets to test the quality of boring tools. In order to achieve a higher dimensional accuracy grade and a smaller surface roughness of the inner hole, in order to improve the barrel productivity, yield and prolong the life of the tool, I plant in the deep hole hinge gun film using carbide reamer The deep-hole high-speed reaming of the gun barrel has the following features: The tool is a cemented carbide reamer (YT15), the working part is made shorter than the low-speed hinged reamer, the pull-hinge method is adopted, and the cutting cone is near The shank is accompanied by a squeezing effect on the inner hole at the same time as the cutting. After processing, the rifle slightly shrinks, and its shrinkage is generally 0.005 to 0.02 mm. The large amount of cutting, the productivity of the business, the cutting amount up to v = 100 ~ 120m/min, f = 0.2 ~ 0.4mm / r, ap = 0.5 ~ 1.5mm. It can obtain high quality holes with processing accuracy of IT7~IT9 grade and rough surface roughness of Ra1.6~0.4μm. As a result of the pull hinge method, the tool bar is subjected to tensile force, no bending deformation, and can withstand a large pre-cut resistance, so it can be used for deep holes with smaller hole diameter and the straightness of the hole is good. After the hinge is pulled, the hinge The knife has left the deep hole so that the machined surface will not be damaged; the operator's boring knife is not required during the processing. The high-pressure coolant is introduced into the tool bar and reaches the cutting position of the tool, so that the chip can be eliminated in time, and the barrel and the cutting tool can be cut in the tropical zone at the same time. Due to the large amount of cutting of the high-speed hinge, the cutting heat generated by the high-speed cutting is large, so it is most suitable to use emulsified oil lubrication. 3 Carbide reamer specific structure and parameters The specific structure of the carbide reamer and its parameters are shown in Figure 3.

skills requirement
1. The blade adopts YT15, model E320 2. The material of cutter body 45; 3. The blade and cutter body are brazed, and it is necessary to carry out retreat after welding 4. The number of teeth Z=3
Figure 3 The specific structure of rigid reamer

The carbide reamer consists of a body, a blade and a guide bush, and a knife pad. The cutter body can be further divided into a working part fitted with a cemented carbide blade, and a guiding part of the guiding sleeve and a part connected with the cutter bar are installed. The guide sleeve is made of cloth bakelite material, and the knife pad is quenched by 45 steel. The function of the knife pad is to prevent the tool from being screwed into the arbor when the tool is working. The connecting part adopts a rectangular thread and the working part of the reamer is made shorter. This is because the working part length of the reamer equals the length of the cemented carbide blade, and shortening the working part of the reamer can enhance the vibration resistance of the reamer. The working part is divided into the cutting part, the calibration part and the back cone part. The carbide reamer adopts the pull hinge method, so the cutting part is close to the arbor side. The specific geometric parameters are as follows: The cutting cone angle is also called main cutting. The taper angle y1 is the main declination angle, which is one of the basic angles that affects the durability of the reamer and the back surface roughness of the reaming hole. When y1=5°, it will easily vibrate when cutting in, and the knife will be generated; when y1=45° , knife tip cusp load is too heavy, prone to cracking, so that the surface roughness increases, through the experiment to take y1 = 15 °, then you can get a smaller surface roughness and higher tool life. The transitional cutting taper angle y2 should produce a transitional blade between the cutting edge and the calibration blade. Its length is 2~3mm, and the inclination is y2=2°~3°. Its function is to make the reaming smooth, and the tool has high durability. Surface roughness is good. The length and diameter of the calibration part affect the roughness and precision of the hole and the shrinkage of the hole diameter. In order to ensure the guiding action of the dumpling and the sharpening of the cutting part of the reamer, the length of the calibration part generally takes 0.5 to 1 times the reamer. diameter. Reamer diameter should be determined as follows: d1max=Dwmax+Pamin
D1min=Dwmax+Pamin-G
Dif = Dwmin + Pamax where: d1 is the diameter of the reamer; Dw is the diameter of the workpiece reaming hole; dif is the scrapped size of the reamer; Pa is the shrinkage of the reaming hole, generally 0.005 ~ 0.02mm; G is the manufacturing tolerance of the reamer. The front corner g adopts a negative rake angle, generally 0° to -6°, and the cutting edge is ground with whetstone in production, and the cutting edge has a fillet radius of more than 0.05 mm, in order to make the chip easier when reaming. For discharge, it is better to make only the major negative rake angle of the reamer main cutting edge and the transitional cutting edge rake angle, and the absolute value of the negative rake angle of the calibrating edge should be reduced appropriately, so that not only the tool is easy to sharpen, but also It also facilitates the discharge of the chips in the machined direction so that they do not interfere with each other. The rear corner a The rear corner a affects the durability of the reamer, and the subsequent degree of durability increases, but can not be less than 6°, otherwise it will increase the friction, increase the cutting heat and reduce the working ability of the alloy blade. Take the main posterior angle a1=8° to 12°, and the second posterior angle a2=15° to 25°. The calibration zone of the land f should be left in the edge zone, but not too large, otherwise the hole shrinkage and roundness errors will increase, and the surface roughness will deteriorate. The general calibration site blade width is 0.10 ~ 0.25mm, the main cutting edge of the blade is as small as possible, the general width is set to 0.03 ~ 0.05mm. The reverse taper should be made into the inverted taper angle in the calibration part, which can make the reamer smooth and no noise when reaming, and make the axial force and cutting torque drop significantly, generally taken as 0.02 ~ 0.10mm, and the larger diameter is larger value. The back taper angle y2 and its length calibration part should have a back cone, the role of which is to avoid scratching the processed hole wall, generally the reverse taper angle y2=6°~10°, and the back cone length 3~5mm. The cutting edge of the cutting edge l Carbide inserts are machined into a left-angled pattern that is 3° from the center of the tool body. This angle is the blade angle l. Its role is to allow the chips to automatically flow to the finished hole, while reducing Circular torque. 4 Conclusions Through the practical application of our factory in recent years, the quality, yield, and productivity of high-speed reaming of barrels with carbide reamers are quite different from those of conventional gun barrels machined with low-speed hinges. The first is that the processing quality has been greatly improved. The pass rate of the low-speed hinge processing barrel can only reach 60% to 70%, while the high-speed hinge reaming process is more than 95%; followed by the production efficiency, the old production monthly production only Can reach 1500 to 2000 barrels, and the new process can reach 3500 to 4000 barrels. Therefore, it is said that high-speed reaming of barrel bores is a new process that can guarantee quality and increase productivity.