Analysis of boring and rolling technology for the

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Boring and rolling process analysis of cylinder barrel processing

cylinder barrel is the main component of oil cylinder, mining single prop, hydraulic support, gun barrel and other products, and its processing quality directly affects the service life and reliability of the whole product. The processing requirements of the cylinder barrel are high. The roughness of its inner surface is required to be Ra0.4 ~ 0.8 m, and the requirements for coaxiality and wear resistance are strict. The basic feature of cylinder barrel is deep hole machining, which has always troubled the machining personnel

rolling processing is adopted, because the surface layer has surface residual compressive stress, which is conducive to the closure of surface micro cracks and hinders the expansion of erosion. Thus, the corrosion resistance of the surface can be improved, and the generation or expansion of fatigue cracks can be delayed, so as to improve the fatigue strength of the cylinder barrel. Through rolling forming, a cold work hardening layer is formed on the rolling surface, which reduces the elastic and plastic deformation of the contact surface of the grinding pair, thus improving the wear resistance of the inner wall of the cylinder barrel and avoiding the burn caused by grinding. After rolling, the reduction of surface roughness value can improve the matching property

1 design of rolling cutter

take our 160mm combined boring hob as an example to illustrate the cutter design and process

as shown in the structural drawing, the protective cap 1 is used to protect the reference position of the tool setting instrument at the spindle head. The function of the support pad 4 and the support pin 6 is to protect the cage (zqsn) from the fracturing of the axial pressure of the roller. The material of the support sleeve 11 is GCr15, which requires interference fit with the mandrel 15 and grinding after assembly

roller material is GCr15 or high speed steel W18Cr4V, 62 ~ 65hrc. Rollers play the role of rolling and guiding in boring hobs. The reason why roller rolling is adopted is that it has a larger working contact area than ball rolling, and can bear a larger rolling pressure. A larger feed rate can be selected to improve productivity. For the workpiece with thin wall and low rigidity, the roller with smaller and longer diameter should be selected. If the roller diameter is smaller, the smaller surface roughness value can be obtained. Here we choose 13mm roller. Another advantage of using industrial computer as the controller for roller fillet radius r in a certain range is that it is convenient to try the storage, management and printing of experimental data, which affects the surface roughness, reduces the fillet radius, correspondingly increases the unit stress, reduces the surface roughness value and improves the surface cold hardness. Increasing the number of rollers Z can reduce the rolling roughness value, but the required rolling pressure increases. Generally, Z is 5 ~ 10, and we take 6. Increasing the roller rolling back angle a can reduce the surface roughness value, but if a is too large, it is easy to form an overcooling state and damage the surface layer, which is generally taken as α ≤1°。 The difference in the diameter direction of the roller will cause jamming, vibration and strain on the machined surface, so the difference in the diameter direction is not greater than 0.03mm

technical requirements:

(1) after assembly, rotate the rear gear ring, protection frame and roller surface to slide freely

(2) when the tool withdrawal is not so obvious, ensure that the cutting edge is upward to avoid strain

1 Protective cap 2 Set screw 3 Cage 4 Support pad 5 Roller 6 Support pin 7 bearing 8 Rear gear ring 9 Front gear ring 10 Small set 11 Support sleeve 12 Bolt 13 Knife body 14 Machine clamp knife block 15 Mandrel

structure diagram of combined boring hob

when the rolling is completed, hook the rear gear ring 8 to make the front and rear gear rings mesh, and insert the tool withdrawal half ring (its length is the basic size of the roller length) between the cage 3 and the mandrel 15, so that the cage drives the roller to move backward along the 1:40 taper of the support sleeve, and retreat into the groove of the support sleeve, so that the roller is out of contact with the cylinder barrel to realize tool withdrawal

the roller, support sleeve and cage in the boring hob are vulnerable parts, and each pair of vulnerable parts can be rolled for about 90m × 150 2150m oil cylinders (calculated by stroke)

2 analysis of influencing factors of rolling

workpiece material rolling is suitable for carbon steel below 50. The lower the carbon content, the smaller the hole expansion. The lower the hardness of the material, the higher the plasticity, the better the surface quality of the rolling. Although the hardness after rolling can reach 400HB, the effect after rolling decreases significantly from 280hb. Therefore, the hardness of workpiece material before rolling is generally not less than 140hb

pre machining generally adopts turning or boring. The geometric accuracy of the workpiece is guaranteed by pre-processing. Generally, the pre-processing ra0.25 ~ 5 m is required, and the filing and rolling machining allowance is about 0.5mm

rolling times the plastic deformation in the first rolling can be widely used in many industries. The shape is the most significant and full, and the surface quality is significantly improved. With the increase of rolling times, the surface will produce excessive compressive stress, which will destroy the surface quality obtained by the first rolling, that is, destroy the cold hard layer of rolling, resulting in peeling phenomenon. Therefore, the rolling times of the combined impact hob is selected once

the larger the cutting amount feed F, the higher the surface roughness value will increase; The rolling speed V has little to do with the surface quality. The interference amount of rolling head is generally about 0.15mm (ordinary 60 ~ 200mm hole oil cylinder), and the rolling amount is 0.02 ~ 0.04m. Taking 160mm hole processing as an example, we take v=30 ~ 40m/min, f=0.1 ~ 0.25mm/r

for cooling and cleaning, we use ht-40 machine oil: Kerosene (GB) =1:1, or vulcanized oil: Diesel =1:1 formula. During machining, the pressure oil rushes from the back of the rolling head to the boring hob, and the raw surface is discharged into the oil groove from the side of the head of the machine, so as to avoid the falling chips scratching the machined surface. The main problem in the design of the oil tank is cleaning and sedimentation rather than cooling, because the cutting oil circulates every 20min, there is no time for sedimentation, and increasing the capacity is not the way. The filtration problem is mainly guaranteed by selecting appropriate filtration equipment and technology. It is proved on site that the filter pore is too large and the pore of felt is too small, which is easy to be blocked

common problems and solutions of cylinder barrel rolling processing: out of tolerance of size: inaccurate tool setting, tool or rolling head wear; There are vibration ripples on the inner surface: the material is too hard and the speed is too high; Obvious knife marks: the feed rate is large, and the cutting depth is too large; Grooving: the cutting edge is broken, the amount of cutting fluid is small, and the temperature of cutting fluid is too high

3 application example

boring and rolling process is an efficient and high-quality process measure. Now the desktop database is adopted with 160mm healthy cutting rolling head (45 steel seamless steel pipe); The query module is taken as an example to prove the boring effect. After rolling, the surface roughness of the hole is reduced from ra3.2 ~ 6.3 m before rolling to Ra0.4 ~ 0.8 m, the surface hardness of the hole is increased by about 30%, and the fatigue strength of the inner surface of the cylinder barrel is increased by 25%. If only the influence of cylinder barrel is considered, the service life of oil cylinder can be increased by 2 ~ 3 times, and the efficiency of boring and rolling process is about 3 times higher than that of grinding process. The above data shows that the boring and rolling process is efficient and can greatly improve the surface quality of the cylinder barrel. (end)

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