Highlights are typical of non-mark injection molding highlights, but not all of the non-mark injection. We have been making high-light molds for several years, mainly for the external decorative parts of home appliance products, such as front panels, decorative pieces, etc., but every time we have encountered the same problem, that is, we cannot solve the fusion mark, shrinkage mark and other forming problems, which greatly affects the structural strength and appreciation of the product taste.

1. Technical principle

We compare the traditional injection molding process, to illustrate the characteristics of high light non-trace injection molding process in the traditional ordinary injection molding process, the mold temperature set low, although can reduce the warpage and shrink marks, shorten the molding cycle, but easy to produce weld marks and material lines, dark gloss, rough surface and other appearance quality. On the contrary, when the mold temperature is set high, the appearance quality of the product surface can be improved, but it is easy to produce warpage, shrinkage mark, poor size, etc., and at the same time, the molding cycle is prolonged, and the cost is increased.

The high-gloss non-trace injection molding technology adopts special fast cooling, fast heating and temperature control equipment, which can solve the above two problems simultaneously. It uses the steam produced by the steam furnace or high temperature water and cooling water, through rapid exchange to control the temperature of the mold in a molding cycle, so that the advantages of the above two methods can be played.

First, high temperature water or steam (such as 150℃) is injected into the mold before injection, so that the mold temperature exceeds the viscous flow temperature of the resin thermal deformation, and then the molten resin is injected, so that the material temperature at the front end of the sink can be maintained in the viscous flow state, and the molding product with good surface quality and no sink line (melting wire) will be formed. After injection of the melted resin, the cooling process begins. Cooling water is used to make the mold temperature drop quickly below the temperature of resin thermal deformation (e.g. 40℃). In this way, the curing speed of resin can be accelerated to shorten the molding cycle and solve problems such as warping and subsidence.

High light non-trace injection molding can eliminate the product surface dissolution connection, dissolution mark, ripple and silver silk, completely solve the plastic product surface shrinkage phenomenon, and make the product surface finish to mirror level, can almost completely reproduce the surface state of the mold, to achieve the effect of no trace.

Products do not need follow-up processing spraying, effectively reduce the cost, shorten the delivery time. In addition, the high light injection molding can also solve the floating fiber phenomenon produced by the fiber products, so as to make the product quality more perfect. In thin-wall molding, injecting molten resin at high temperature helps to improve the fluidity of injection molding, reduce injection pressure, avoid problems such as insufficient pouring and trapped gas, and improve product quality and strength. And through the rapid cooling after forming, it can also reduce the shrinkage stress, so that the demoulding becomes easy. It can also reduce the injection cycle of thick wall molding by about 60-70%.

2. Technology application

High light non-trace injection molding can be widely used in DVD/DMR/BD/BR/PDVD and other audiovisual player panel, LCD TV, computer LCD display, automotive LCD display, air conditioning, automotive interior parts, car lights, optical instruments and other home appliances, automotive, communication, medical and other industries.

3. Control principle

The whole closed-loop system controls the detection of input and output temperature, and the temperature sensor is designed inside the mold. The actual temperature of the mold is fed back to PLC, and the change of the digital and color picture is displayed to ensure the accuracy and stability of the output. Steam (high temperature water, cold water, and mold temperature display, interlocking with injection molding machine signals with time and action.

4. Technical points

High light non-trace injection molding, the key technology lies in the mold, material, mold temperature control machine.

The response sensitivity of injection molding machine should be high, the stability should be good, and the feedback signal can be fast in real time.

4.1 Mold matching

The design of the mold should consider the design of high temperature resistance, suitable for water design, installation matching and other factors. High light non-trace injection is to use high temperature hot water or steam, making balanced heating way, in the mold after the injection molding machine out high temperature circulating water is piped in, first of all increase the mold temperature to a set value, and then start to cavity injection plastic, pressure into the cooling after the completion of the injection molding machine, began injecting cold water into hot water recycling, mold temperature quickly fell to a set value after the mould opening the cold water recycling, Complete the injection molding process. Because it is the quench and quench molding process, the die has to undergo rapid cold and hot impact, so the material selection of the die is very important, and the die steel with good thermal fatigue strength must be selected.

4.2 Match mold temperature machine (control machine)

It can quickly generate enough high temperature water (steam) and can interlock with the injection molding machine signal to achieve closed-loop control.

5. Investment analysis

5.1 Mold cost

Due to the use of matching water design and the use of high temperature resistant parts, the cost of small simple mold slightly increased by about 15-30%, large mold should be calculated according to the actual.

5.2 Device Solution

It is composed of high speed heating (steam or high temperature water) device, rapid cooling device, control device and injection molding machine.

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