Design and Research of 3D Precision Mobile Workbench

In the field of modern industrial applications, different requirements have been put forward for precision moving tables. Most of the precision mobile worktables in the field of optical fiber communication require assembly, and are assembled into two-dimensional precision mobile worktables by precise moving mechanisms in both X and Y directions: assembled by precise moving mechanisms in three directions: X, Y, and Z. As a three-dimensional precision mobile workstations. Because the precision and stiffness of the contact surface of the assembly and the relative movement of the moving parts all affect the precision of the workbench, the accuracy of the existing three-dimensional precision mobile worktable cannot meet the requirements of use. In order to meet the requirements in the field of optical fiber communication, a three-dimensional precise moving table with a stroke of 15 to 20 mm and an accuracy of 0.003 mm in three directions must be designed. 1 The overall design According to the requirements, the designed three-dimensional precision mobile worktable should meet the requirements of the specified range, precision, and sensitivity. At the same time, the work performance should be stable and reliable, eliminate empty return, and reduce errors. In the assembly design, the three directions are perpendicular to each other, so the direction of movement of the active and driven parts in the three directions from bottom to top can be set as the X, Y, and Z in the Cartesian coordinate system. Axial. Since the matching surfaces in the X, Y, and Z directions and the assembly relationship directly affect the accuracy of the overall operation, the respective surfaces and the contact surfaces of the operating components are required to maintain the corresponding accuracy. Structural Design The three-dimensional precision moving table is mainly composed of a support device, a micro-displacement driven reading device, a load-bearing and micro-displacement mechanism, and a connecting device. The selection and design of micro-displacement-driven reading devices, load-bearing and micro-displacement mechanisms play a decisive role in the design of the entire product. It is mainly driven by a screw micro-motion device, the number of cylinder reading devices, and the rolling friction guide for guiding. In other words, the entire three-dimensional precision moving table is composed of a supporting device - a base, a bottom plate, a micro-displacement driven reading device, a load-bearing and micro-displacement mechanism - a three-dimensional sliding plate, a guide rail, and a connecting device - a right angle fixed block, etc. . Design Principles and Design Principles On the basis of the long-term practice of geometric measurement instrument design, some design principles and design principles with universality or in certain situations with universality have been formed. These design principles and design principles, according to the specific conditions of different instrument design, as the technical measures in the instrument design, have brought good results in ensuring and improving the accuracy of the instrument, improving the performance of the instrument, and reducing the cost of the instrument. Therefore, how to follow or properly use these principles and principles in the overall plan of the instrument is a content that should be considered in the overall design stage of the instrument. In this design, in order to reduce the impact of Abbe's error, in the design of the base as much as possible to ensure the linear relationship between the movement of the active part and the follower, the guide rail structure design and process to ensure that the rail has a good linear movement Sex. Spiral micro-displacement drive reading device, follow the principle of the shortest measurement chain, as far as possible to minimize the measurement link, thereby reducing errors, improve the overall mechanism accuracy. The principle of spiral micrometering refers to the principle that the linear displacement of the spiral motion is proportional to the angular displacement. The upper and lower rows of engraved lines are engraved on the sleeve. The distance between the lines in the same row is 1mm, and the two rows of upper and lower lines are staggered by 0.5mm, which equals the pitch of the micrometer screw. The differential cylinder is engraved with 50 aliquots. When it rotates one revolution, the screw is displaced by 0.5 mm: one grid is rotated and the spindle moves by 0.01 mm. So the spiral micrometer has a division value of 0.01mm and a sensitivity of 0.001mm.

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Figure 1 Calculation of the length of a moving part

2 Design of key components The key parts of the three-dimensional precision moving table are mainly the rolling friction guides, micro-displacement driven reading devices and spring tension devices. Dividing reeds are the most critical parts. It can be seen from Fig. 1 that L=e+l+ab (1) and ab=a'b'=a'c+cb'=e+cb' (2) The relationship between the linear velocity Vr of the center of the ball and the velocity Vm of the moving member. Vr=Vm/2 (3) then cb'=Smax/2 (4) Therefore, L=2e+l+(Smax/2) (5) The above formula shows that when the stroke is Smax, the shortest length of the moving piece is 5) can be found, when the trip to take the maximum displacement of 30mm, l is the center distance between the two balls, in order to ensure the carrying capacity, the three-dimensional precision moving table on each side choose 4 steel balls, l can take the middle two or two two The distance between steel balls. e is the amount of insurance, with a reed isolation and fixed, so the two sides of the ball e optional 5mm. From the formula (5) available l = L-2e-(Smax/2) = 55mm (6) The total length of the reed can be designed as L' = l + 2e = 65mm (7) 3 precision analysis accuracy is one of the instrument The key technical indicators, instrument accuracy analysis is an important part of the instrument design, usually it is a major issue that should always be considered in the design process. Accuracy analysis here refers not only to the synthesis of errors in various parts and components of the instrument, but also to the assignment of tolerances and the determination of the main technical conditions in the design of the instrument, and even the technical measures that need to be taken in order to further reduce the instrument error: such as errors. The adjustment method, the design of compensatory parts, etc. As shown in FIG. 2 , the three-dimensional precise moving table is realized by the following three constituent rings.

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Figure 2 Measurement principle

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Figure 3 The schematic diagram of the sub-card reading

Sources of Error Three-dimensional precision mobile workstations are designed and manufactured to solve some of the more precise measurement problems. It is mainly used to measure the length or distance within a certain range of space. It is an absolute measuring instrument based on the positioning and coordinate measurement of the drive of the centimeter card. It compares the length reference element with the measured length (or distance) to determine the size to be measured. During the measurement, first read the first reading on the reading device—differential cylinder, then rotate the centimeter card to drive the slide, align the workpiece, and read the second reading on the reading device. The difference between the two readings is It is the measured size of the workpiece. The measurement equation is L = ba where: L is the measured size: b is the second reading: a is the first reading. X, Y, Z triaxially upwards is a direct reading using a spiral micrometer method. Therefore, the measurement equation is μ=x. According to the reading principle of the centimeter card, as shown in Figure 3, the error mainly includes the pitch error 1μm, and the micrometer reading error. 1 r, it is generally assumed that the reading error is 1/10 of the reading of the instrument, and the minimum reading of the centimeter card is 10 μm, ie 1 r=t/10=1 μm. Accuracy Analysis From the above error analysis, the total error of the three-dimensional precision moving table can be obtained as: x direction: 1 SX micrometer pitch error, 1 rX centimeter reading error, 1 Error in the X direction on the second dimension of X2, 1 X3 error in the X direction on the third dimension. 1 limX=±( 1 2SX+ 1 2rX+ 1 2X2+ 1 2X3)1⁄2=±1.581μm Similarly find 1 limY=±( 1 2SY+ 1 2rY+ 1 2Y2+ 1 2Y3)1⁄2=±1.581μm 1 limZ=±( 1 2SZ+ 1 2rZ+ 1 2Z2+ 1 2Z3)1⁄2=±1.581μm The total measurement error of the three-dimensional precision moving table is 1 Lim=±( 1 2limX+ 1 2limY 1 2limZ)1⁄2=±2.793μm

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