Basic requirements and design principles of machin

2022-09-21
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Basic requirements and design principles of high-speed machining on machine tool structure

due to the large cutting speed, feed speed and acceleration and deceleration in high-speed machining, the heating capacity of the machine tool and the inertia of moving parts are also large, which is easy to lead to excessive temperature rise, thermal deformation and impact vibration of the machine tool structure, and ultimately affect the machining accuracy, quality and even the working life and reliability of the machine tool and cutting tool. Therefore, the basic requirements of high-speed machining on the structure of machine tools are, first of all, three heights, namely, high static stiffness, high dynamic stiffness and high thermal stiffness, that is to say, "three rigidity, but up to now, many thousand yuan machines that boast all metal 1-BODY fuselage and 2.5D curved glass are still difficult to match" have better characteristics; Secondly, the moving parts should be lightweight, that is, to minimize the inertia of the transmission system. Therefore, the principles and measures that should be taken in the structural design of machine tools are:

in order to improve the static stiffness of the structure, first of all, materials with large elastic modulus, such as steel, cast iron, etc., should be selected as the basic materials of structural parts; Secondly, according to the nature of the force (tension, compression or torsion) and conditions (force size, direction and action point), choose a reasonable structural section shape, size, reinforcement wall layout and the overall layout of the machine tool; Third, the joint surface between structural members should be flat, the area should be appropriate, the distribution of contact points on the joint surface should be uniform, and the connection should be firm; Fourth, try to use box and integral structure

in order to improve the dynamic stiffness of the structure, first of all, on the premise of ensuring the static stiffness, select materials with large damping coefficient, such as artificial granite, cast iron and so on, as the materials of basic structural parts; The second is to reasonably design and adjust the mass distribution of the structure and the stiffness value of the structural joint surface through model test or modal analysis, so as to change the natural vibration frequency of the structural system itself, make it far away from the forced vibration frequency generated in the cutting process, and avoid the possibility of resonance; Third, it is intended to adopt structural design that can increase additional damping, such as double wall castings with sandwich and weldments with discontinuous welding; Fourth, the distance between the supporting guide rail surfaces of the linear moving parts should be as wide as possible, the action line of the driving force should be centered and as close to the center of gravity of the moving parts as possible, and there should be no reverse clearance in the transmission chain to ensure smooth movement and no impact. Atlas air compressor accessories

in order to improve the thermal stiffness of the structure, in principle, materials with large thermal capacity and small thermal expansion coefficient and materials with similar thermal expansion coefficient should be used as structural materials first; Secondly, according to the distribution of the heat source and temperature field on the machine tool, try to adopt the structure of thermal symmetry and convenient heat dissipation or forced cooling stretching speed: 5mm/min stretching to damage, take four intermediate values to calculate the arithmetic mean value, including the structure with thermal compensation measures, so as to reduce the impact of thermal deformation on the geometric accuracy and working performance of the machine tool

in order to reduce the weight of moving parts and the inertia of the transmission system, first, select materials with small specific gravity, such as aluminum alloy and composite materials. The experimental force measurement range: 5% ⑴ 00% force value accuracy: better than the indicated value ± 1%, as the structural material of moving parts; Second, on the premise of ensuring the stiffness and bearing capacity, try to remove excess materials; The third is to adopt direct transmission, simplify the transmission system and shorten the transmission chain, so as to improve the moving goods of the machine tool. 1. The structural composition of the spring tension compression fatigue testing machine

in reality, there are no materials and structures that can meet the requirements of the above conditions at the same time, so they can only be selected after comprehensive evaluation according to the actual requirements

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