4. Ensure sufficient mold strength
Mold strength is a very important issue in mold design due to the harsh working conditions of the mold during extrusion. In addition to the proper placement of the die holes, the selection of suitable mold materials, and the design of a reasonable mold structure and shape, it is also important to accurately calculate the extrusion force and check the allowable strength of each dangerous section.
At present, there are many formulas for calculating the pressing force, but the modified Birling formula still has engineering value. The upper limit solution of the pressing force also has a good applicability value. It is relatively simple to calculate the pressing force by the empirical coefficient method. As for the check of the strength of the mold, it should be carried out separately according to the type of the product, the structure of the mold, and the like. Generally, the planar mold only needs to check the shear strength and the bending strength.
Tongue and flat split molds need to be checked for shear, bending and compressive strength, and tensile strength is also required for the tongue and tip. An important fundamental problem in strength checking is the selection of a suitable strength theory formula and a relatively accurate allowable stress. In recent years, the finite element method can be used to analyze the stress and check strength of a particularly complicated mold.