Analysis of common problems in the processing technology of EVA foam die-cutting parts

Among the die-cut parts we process, we often encounter EVA foam processing. Generally, the thickness will be 1-2mm, and the final thickness may reach 5 mm. For this kind of foam processing, in the production process , Will definitely encounter many problems of this kind or that kind. Then the problems we often encounter are mainly manifested in the following three points:

1. Beveled edges are prone to appear in the foam punching process (the beveled edges of circular knife die cutting are larger);

2. It is easy to produce debris and dust during the punching process of these thickness foams;

3. For some porous products, it is difficult to discharge waste (the hole diameter is too small, the thickness of the foam is large, and the waste discharge is difficult to achieve);

This is some very common phenomenon we encountered in the process of EVA foam operation. Below, the editor will analyze the above three common problems and give relevant solutions; we will discuss the characteristics of EVA foam itself. Let’s make a brief introduction: EVA foam has a high thickness, a certain degree of elasticity, and a low elastic limit, which is easy to generate dust. Due to the above characteristics of EVA foam, the three basic problems we have mentioned before will occur in the die-cutting process of EVA foam;

hypotenuse problem

First of all, regarding the beveled edges that are prone to appear in the die-cutting and punching process, the reason for this problem is that the thickness of the foam is high. In the punching process, the foam is extruded and cut after the foam is extruded. Beveling, the main method for solving such problems is to change the choice of tools.

Usually the die-cutting tool we use is a double bevel cutting tool for punching operations. So here to ensure effective reduction in the generation of beveled edges, we use a single-edged knife to punch the inner straight and the outer bevel, which can effectively reduce the generation of foam beveled edges.

At the same time, for EVA foam die-cutting parts with a relatively simple structure, we use slitting, edge splitting, and skip cutting methods to reduce the factor that affects the beveling, so as to avoid the beveling problem. For some products with a slightly complicated structure, we can use the method of knife line decomposition to punch, instead of closing the knife line, and multi-wire overlap, to reduce the extrusion stress during the foam punching process to reduce the foam skew Side issue.

debris dust

Secondly, with regard to the problem of EVA foam debris and dust, the root cause of this problem lies in the characteristics of the foam itself. Due to the low toughness of the foam, the composition structure is a foam material. All in the punching process, because The repeated action of the knife makes the debris foam particles easily form dust and float in the air. For some die-cutting operations that require cleanliness, there are many ways to solve such problems. The common method is to spray a release agent. The method often used on the production line is to compound an OPP protective film on the surface of the EVA foam. Solve this problem. Of course, this solution may cause some waste of auxiliary materials.

Waste is difficult

Third, with regard to the difficulty of discharging waste with porous waste, the most fundamental reason for this kind of reason is that the foam is too thick, and the small hole diameter causes the waste to be difficult to extract in the process of discharging. The general traditional method is to make a set of thimble fixtures outside the die-cutting machine die base to discharge waste, and eject the hole-shaped waste through the thimble to discharge the falling material. However, this kind of waste discharge method is not easy to operate, and it is easy to scratch the foam and cause product failure. The commonly used method on the round knife is the extraction knife for extraction and waste disposal. Today, for the occurrence of this kind of problem, the editor gives a better job plan, which is the asynchronous job plan.

Solution-on asynchronous operation

Fourth, the benefits of the upper asynchronous operation scheme; as everyone knows, the upper layer material is asynchronously pulled and the lower layer material is synchronously die-cut to achieve the purpose of saving materials. Here, we use the asynchronous method to separate the foam and the backing film to pull the material, which not only saves the foam material, but in the actual operation process, the upper material belt is taken away, and the foam outer frame waste It is also taken away at the same time, and due to the effect of stress, the hypotenuse will be greatly improved. Moreover, through this operation method, the basic dust problem has also been effectively solved.