New technology of scraping on the fixed joint surf

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Abstract: This paper studies the traditional scraping method, puts forward the quality problems caused by this method, and puts forward a new scraping technology - vibration point scraping method. The advantages of this new process are discussed: increasing the actual contact area; Reduce contact deformation and eliminate the influence of macro unevenness

key words: scraping grinding vibration grinding point contact area contact deformation

the fixed joint surface of lathe spindle box and lathe bed is an important joint surface. Because this surface determines a precision of the lathe spindle, and such important contact surface is scraped by the traditional scraping and grinding method. The contact surface of the lathe bed is the scraping and grinding surface, and the bottom surface of the spindle box is the fine planing surface. After fastening, due to the macro unevenness of the machined surface, only a few hard points are in contact with the machined surface, so that the contact stiffness of the fixed contact surface is low, the dynamic stiffness of the machine tool is low, and the anti vibration performance is poor. At the same time, the contact points wear fast and the accuracy of the machine tool is unstable

the author proposes the vibration point scraping method, also known as the in place point scraping method. With this new process, the number of contact hard points can be controlled, and the contact stiffness of the interface can be controlled. It is easy to interact with the electrolyte and produce gas precipitation in the process of charge discharge cycle reaction

because the vibration lapping must install all parts of the machine tool in place, it is also called in place lapping method. For example, the joint surface between the spindle box and the lathe bed of an ordinary lathe can be machined by the traditional scraping and grinding method, and then the spindle box and the lathe bed can be fastened, and the driving generator can be started. For example, if the assembly process is complex, the vibration exciter can be used to excite the machine tool. At this time, vibration friction occurs on the fastened joint surface, and a few hard points in contact will be displayed, and then the hard points will be scraped to allow more high points to participate in the contact. At this time, the scraped surface is no longer flat. The contact between the scraped surface and the fine planed surface is like the bite of people's upper and lower teeth, which can eliminate the impact of macro unevenness. At this time, the hard contact points are evenly distributed. With the increase of scraping times, the number of contact points per square inch will also increase. For the contact surface between the spindle box and the lathe bed of the ordinary lathe, if the contact hard point reaches 7 points per square inch, the contact deformation can be zero, meeting the contact stiffness requirements. The deformation of this contact surface is zero, which reduces the deformation of the general lathe by 15%. At this time, Solvay TORLON and spire super performance polymers that are actually used in these fields have more advantages, and the contact area is equal to the nominal contact area. Due to the large contact area, the pressure is small and the wear is small under the action of external force. The precision life of the machine tool directly enters the stable period

A mathematical model can be used to describe the mechanism of the vibration grinding point of the speed bed which is more suitable for the setting of the

machine. In case of forced vibration of the machine tool, the displacement response of the fixed joint surface is

where p - excitation force, mpa

ω N -- natural angular frequency of the system, rad/s

ω—— External force angle frequency, rad/s

δ—— Attenuation coefficient,

t - time, s

in the process of metal cutting, the inertia system composed of machine tool, workpiece and tool is a vibration system. The joint surface between the headstock and the lathe bed is a part of the system, and vibration may also occur. The transfer function of the system is KC - cutting stiffness in the formula

, which represents the cutting force generated by the unit cutting cross-sectional area, n/(mm μ m)

b - cutting width, mm

μ—— Overlap coefficient of two cuts

w (s) -- transfer function (s=i) under the open-loop state of the system ω)

u - displacement response, μ M

the displacement responses of the above two vibration modes show that the vibration friction occurs under the excitation force after the fixed joint surface is fastened, and the light appears after contacting the hard point friction

vibration lapping point scraping lapping method eliminates the influence of the macroscopic unevenness of the joint surface, so that the actual contact area increases equal to the nominal contact area, and the contact deformation is zero. From the contact stiffness formula k=p/δ (where p is the acting force; δ For deformation) analysis, when δ → 0, the contact stiffness tends to infinity. The practical significance is that two separate components are equivalent to an integral part. As a result, the anti vibration performance of the machine tool is significantly increased. The cutting width of the lathe assembled with the new process is increased by 2mm compared with that before the sensor. The machined surface roughness value is reduced by one grade. The correlation accuracy is more stable than before

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