With the stone processing industry, the need for product, processing accuracy has been improving the mechanical properties of the formation of stone requirements are rising. To meet the market needs, enhance the development of new products to meet market demand. Stone machinery products representative stone bridge cutting machine for its high precision, low failure rate, easy operation, wide by the majority of users. I cut stone on the bridge of stone processing machine, the accuracy of key mechanical components of the design principles of beam rail and processing technology, to make some personal views for the peers to participate.
Stone Machinery beam rail common design, there are two combinations: the first is a dual three-shaped rail solution portfolio. These two combinations are the combination of open rail, the guiding properties of a triangle with the top rail solution size and different α, α-oriented solutions of the smaller the better, but when the angle α decreases the equivalent rail surface the more friction coefficient Large, usually limits the angle α is the triangular track 90 °, for the heavy, large stone machinery, the load is large, it is desirable α = 110 ° ~ 120 °. When the triangular face has worn rail, the table automatically goes down, wear compensation, rectangular high with steel rails, processing, inspection and repair are more convenient features, but the direction is poor. Double triangular guide rail and to maintain the accuracy of all high, but the super-positioning, processing, inspection and maintenance are more difficult. Poor working conditions of stone machinery, stone dust, mist, diamond particles in the cutting process easier splashing in the track surface, due to heavy cutting is the cutting, making the track surface wear increased. At present there are still some stone machinery dual triangular beam rail designed to compensate rail wear, rail in the design process should meet the following requirements.
1, the precision-oriented
Rail movement and cutting no-load conditions, movement, orientation accuracy should be sufficient to ensure the accuracy of rail movements, this guide is to ensure the quality of the premise. Guiding accuracy of the main factors are: the rail structure, guide and contact the geometric accuracy precision, rail and basic parts of the stiffness of the film thickness and film guide stiffness, rail and basic parts of the thermal deformation.
(1) geometric accuracy
Geometric precision linear motion guides generally include: rail line in the vertical plane degrees (referred to as the A term precision), rail line in the horizontal plane of the precision (the precision of item B), two parallel guide surfaces also called the twisted (the accuracy of C entry), in A, B are set in both the accuracy of each meter length of rail straightness and rail on the length of the straightness, accuracy of entries in C, provides rail per meter in length and the length of the rail, the two rail surfaces per meter length in the horizontal distortion values. The A, B, C three precision tolerances, please refer to the relevant machine precision test.
(2) contact accuracy
Fine planning, grinding and scraping the track surface, the contact by JB2278-78 accuracy requirements, the use of shading to check the percentage of contact surface or with a 25 × 25 (mm) area of the contact points to measure.
2, to maintain the accuracy of
To maintain the accuracy of the wear resistance is mainly determined by the rail, the nature of its friction with the guide rail, rail and materials, process methods, and the forces and so on. In addition, pieces of rail and infrastructure also make rail residual stress affects creep to maintain the accuracy of the rail. To maintain the accuracy of the main factors of wear and improve the wear resistance in order to maintain accuracy is to improve the quality of one of the main machine is a major topic of scientific research. There are many factors to improve wear resistance, increased wear resistance from design, technology, materials, heat treatment, the use of other areas considered. Here mainly from the design point of view for analysis. Improve the wear resistance from the design point of view the basic idea is: to fight for no wear and tear; wear and tear can not be avoided as far as possible for less wear, uniform wear, and worn to compensate for increased lifespan.
2) Second is to strive for even wear
Wear is uniform on large parts of the work period, such as beam guide, if wear is uniform, the general had little effect on the machining accuracy, and can be compensated. Uneven wear for two main reasons: the uneven distribution of pressure in the friction surface, the use of opportunities in different parts. Uniform wear for the following measures: seek to pressure the friction surface of the uniform distribution, such as shape and size of the rail on the concentrated load symmetrical as possible to minimize the torque and subversive moment; ensure adequate supports for rigidity; rotary motion guide should not be too wide, so much speed difference; friction in the use of full-length inequality of opportunity that a hardness should be higher.
3) Another point is the wear and tear should be able to compensate for wear
Wear bigger the space, the design should be considered on the structure can compensate for this gap, the compensation method is automatic and continuous compensation can also be a regular labor compensation. Automatic and continuous compensation can be by weight, such as triangular and V-shaped rail, regular compensation can paste PTFE artificial plastic, closed by the adjustment guide plate and so on.
Common form of wear and tear of the following:
(1) abrasive wear or durum
This often happens in the boundary friction wear and mixed friction state. Relative sliding friction between the abrasive (or durum) is mainly derived from: Micro uneven state of high friction surface, in the relative motion be cut down and stay in between the friction surface, with the entry of lubricating oil guide surface between the hard particle; the protection not to fall into the rail surface of the chip friction between the particles, the friction force between the particles can be decomposed into the friction surface and perpendicular to the direction of movement along the friction surface The two pitch, vertical pitch will be abrasive to the metal surface pressure, the greater the force the more hard and abrasive, he was pressed into deeper; along the friction surface of the force, will produce abrasive and sliding metal surfaces, "cutting" rail surface, the friction surface have a "scratch" or a "grooves." The higher the hardness of abrasive, the greater the relative sliding velocity, the greater the pressure on the friction the greater the harm. Abrasive wear is inevitable and can only be minimized. Therefore, the design should maximize the hardness of the support rail, and to limit P * V (the product of pressure and speed) value does not exceed the allowable value of the material.
(2) adhesive wear and tear or bite welding
Adhesive wear is also known as molecules - mechanical wear, when the two friction surfaces in contact with each other in the high-pressure plastic deformation of materials under high, relative movement of the friction, but also the surface layer of oxide film destruction, exposed metal in the new arise between the surface attraction between molecules and infiltration, so that bonding occurs bite point of contact welding. Contact surfaces in relative motion but also the bite spot opened to cause tearing of the damage. Welding is not allowed to bite occurred, in order to avoid this situation, the design should be the right choice except materials, hardness and maximum pressure control, it must also correct the provisions of the plane sliding surface error, surface roughness, or the number of contact points.
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