The design of the
Glasses And Clocks Micro Screws positioning system is a core element in ensuring accurate blank positioning and avoiding defects in the stretching process. Its rationality directly determines the wall thickness uniformity, shape accuracy, and production stability of the stretched parts. In the field of thin sheet stretching, positioning errors can cause problems such as localized tearing, wrinkling, and eccentricity. Therefore, system design must focus on dimensions such as datum selection, structural optimization, and precision compensation.
First, the rational selection of the positioning datum is the foundation of the design, and must adhere to the principles of datum coincidence and process uniformity. The positioning datum for the stretched blank should preferably be the outer edge rather than the inner hole, because most stretched blanks are flat parts, and their external dimensions are easily observed and aligned, avoiding additional errors caused by inner hole machining. For small, precision stretched parts, a process boss can be added as an auxiliary datum, utilizing the regular shape of the boss to simplify alignment. The selection of the datum should avoid datum transfer. For example, the positioning datum should coincide with the design datum of the drawn part during the design process to reduce accumulated errors. In manual feeding scenarios, the datum should also be operable, such as reserving a 10-15mm wide positioning edge on the edge of the blank to facilitate quick alignment by operators and reduce the rate of manual alignment deviation.
Secondly, the customized design of the positioning structure must adapt to the blank shape and production mode, adhering to the core principles of three-point positioning and centering. For symmetrical drawn parts (such as cylindrical or box-shaped parts), a V-shaped centering positioning mechanism is used instead of a single-sided stop. Through the symmetrical constraint of the positioning surfaces on both sides, the center of the blank and the center of the punch are ensured to be coaxial, avoiding single-sided wall thickness differences. For asymmetrical complex drawn parts, a combination of multiple stop pins is used for positioning. At least three positioning stop points are set and distributed in the non-collinear area of the blank edge. Utilizing the principle of three points determining the plane, the translational and rotational degrees of freedom of the blank are restricted to prevent positioning offset. For large-sized, thin blanks, it is necessary to combine them with elastic floating positioning elements, such as spring-loaded positioning blocks, to ensure blank positioning accuracy while avoiding blank deformation caused by rigid jamming. This is especially suitable for the rapid docking requirements of automated feeding systems.
Third, precision compensation and error control are key to ensuring positioning accuracy. On the one hand, the precision of the positioning element itself needs to be controlled: the flatness error of the positioning surface should not exceed 0.02mm, and the surface roughness should not be lower than Ra1.6 to reduce frictional resistance deviation during alignment; the coaxiality between the positioning element and the punch should be controlled within 0.05mm to avoid tensile uneven loading. On the other hand, it is necessary to address the tolerance fluctuations of the blank. The diameter of ordinary stop pins should be 0.1-0.2mm smaller than the positioning edge of the blank to allow for minor adjustments. For the thermal deformation problem caused by high-speed continuous stretching, the positioning element should be made of a material with a coefficient of linear expansion close to that of the mold matrix, or a temperature compensation structure should be designed to avoid the impact of thermal expansion and contraction on positioning accuracy during production.
The positioning system needs to be validated through simulation and trial production: CAE stretching simulation software is used to analyze the displacement distribution of the blank after positioning and to predict the risk of eccentricity; during trial production, the wall thickness of the stretched part is measured using a coordinate measuring machine. If the wall thickness difference exceeds 10%, the position or size of the positioning element needs to be adjusted until the process requirements are met.
In summary, the design of the Glasses And Clocks
Micro Screws positioning system must take into account the rationality of the benchmark, the adaptability of the structure, the controllability of accuracy, and the iterative verification to ensure the accuracy of blank positioning from the root and provide core support for the quality stability of the stretched part.
