[China Aluminum Network] In the extrusion production, there will be defects in the type, bar in the first part of the tail, the semi-finished part of the tail after alkali corrosion inspection commonly known as "shrinking" defects, the mechanical properties of the bar containing the organization of the Less than required, there are security risks. At the same time, when the production bar is subjected to surface treatment or turning, the continuity of the material is damaged due to the presence of the defect, which will affect the subsequent surface and finishing, and severely cause hidden lines to be scrapped or damage turning tools, etc. This is a common problem in production. Herein, this article briefly analyzes the reasons for the formation of shrinking tail and the methods for elimination. Cnc Punching,Cnc Parts,Wholesale Aluminum Parts,High Quality Aluminum Cnc Machining JIANGSU TONGDE INTERNATIONAL TRADE CO.LTD. , https://www.jstongdetrade.com
The classification of shrinking tail is classified into two types: hollow shrinking tail and ring shrinking tail. 1) Hollow shrinking tail: forming a hollow at the center of the extruded shape and the tail end of the bar, and the cross section presents a hole with a non-smooth edge. Or the edge is filled with other impurities in the hole, the longitudinal funnel-shaped (tapered), the funnel tip toward the metal out of the direction, mainly in the single-hole flat die extrusion, especially the extrusion coefficient is small, the product diameter is large, thick-walled Or the tail of the extruded profile using an oily extrusion pad is more pronounced. 2. Annular shrinkage: Discontinuous annular or arcuate shape at both ends (especially the head) of the extrusion-shunting molded product. The crescent shape is obvious on both sides of the welding line. Tail symmetrical.
The formation of tail-shrinking causes the formation of tail-shrinking: the mechanics of shrink-tail formation is: When the advection phase is completed, the pressing gasket gradually approaches the mold, and the extrusion pressurizes and creates a dN tube on the side surface of the extrusion tube. When the force and the friction force dT barrel together, when the balance condition of the damage (dN tube + dT tube) ≥ dT pad, the metal around the extruded gasket area flows back to the center of the blank along the edge, forming a contraction. tail. The extrusion conditions formed by shrinking tails are: 1. Extruded residue is too short 2. Squeeze gasket is oily or dirty 3. Ingot or wool surface is not clean 4. Product tail length is not specified 5. Extrusion Overshot of the cylinder liner 6. Sudden increase in extrusion speed at the end of the extrusion.
Elimination of shrinking tails Measures to reduce and prevent the formation of shrinkage tails: 1. Strictly press the cutting pressure and sawing heads and tails in accordance with the process, keep the inner liner of the extrusion tube intact, prohibit squeezing gaskets? {Oil, reduce aluminum The temperature before the rod extrusion, the use of special convex gaskets, the use of a reasonable length of the material. 2. Extrusion tools, aluminum rod surface should be cleaned 3. Regularly check the size of the extrusion cylinder and replace the unqualified tools 4. Smooth extrusion. In the late extrusion period, the extrusion speed should be slowed down, and the remaining thickness should be properly retained, or The use of increased residue method extrusion.