In the production process of PU self-skinning, there are many undesirable production phenomena such as pinholes, bubbles, dry scars, lack of material, uneven surface, broken, color difference, soft, hard, release agent and paint are not sprayed well. Let's talk about the problem and generation of bubbles today. First of all, the generation of bubbles is related to three major parts: mold, machine and raw material formula. Today, let's talk about mold. When the temperature of the mold is not high enough, it does not reach the temperature required for product production. If the mold is opened at the normal production speed, bubbles may occur.

There are steel mold, aluminum mold, resin mold, three different materials mold, copper mold, and fiberglass mold have faded out of sight in recent years.

1. Some production units use electric ovens for heating.

2. Some are heated with water.

3. More gas heating. Relatively speaking:

A. The cost of electric heating is high, which is suitable for continuous production and large-scale production, and requires higher proficiency in operation.

B. Water heating is simple, convenient and easy to control.

C. It is not advisable to heat the gas. Fireworks are prohibited in the original production place, which is unsafe, dangerous and difficult to control.

During the production of steel and aluminum molds, it is necessary to prepare for heating. Some of them are grooved on the surface, and then buried with aluminum tubes. Heat transfer through the aluminum tubes, and some of them are drilled directly on the mold. I think direct drilling is the best, convenient, and heating is the most direct. The low temperature of the mold will produce bubbles, the curing time is not enough, the mold temperature is too high, the product is relatively bloated, and it is easy to crack when opening the mold. Different mold production lines, such as steel mold requirements of 45 degrees, and resin mold requirements of only 40 degrees, can properly adjust the water inlet of the ball valve of the water pipe to achieve the effect of temperature control. In general, mold heating has relatively little effect on the formation of self-skinning bubbles.

Some molds need exhaust to reduce the formation of bubbles

2、 Mold exhaust:

A. The hole L1.0 -- 1.5 mm directly punched on the surface of the mold is good and too large, and the scar of the product is too large after the nail is cut.

The peripheral exhaust of the mold is called slotting, which can be done with a blade, saw blade, or grinder. No matter which method is used, it should be noted that the more close to the parting line at the slotting time, the shallower. It can be deeper away from the parting line, so

A. From shallow to deep, if the parting line is too deep, it will directly affect the appearance of the product parting, and the scar after edge cutting will also be too large. The position of vent hole and vent slot is generally to put the mold at the angle of normal foaming, and confirm the best position of vent hole and vent slot according to the product. The principle is to minimize the opening of vent hole and vent slot. When the products with high requirements cannot have vent holes and vent slots, after shaking the mold, set the foaming angle and make the mold buckle a little easier. When the original foaming reaches the edge of the mold, quickly buckle the mold, which can also achieve the effect. Some molds are flat, some molds have an angle, and some molds need to be 360 ° shake the mold. Personally, the product requires a flat surface, and the back is not tight, which can also lead to poor quality.