BMC Parts Maintain High Mechanical And Electrical Properties

BMC Parts pressing principle and its process and other thermosetting plastics are basically the same. In the suppression, a certain amount of BMC Parts into the preheating die, the pressure, heat curing molding for the required products.

1, BMC molding process characteristics

① waste less material, usually only the total consumption of 2% -5%, the actual material loss also depends on the shape of the finished product, size and complexity.

② in the molding process, BMC Parts, although it contains a lot of glass fiber, but it does not produce a strong orientation of the fiber, so the product of uniformity, high density, and residual internal stress is also small.

③ In the processing process, because the filler and fiber rarely broken, it can maintain a high mechanical properties and electrical properties.

④ in the press because of its relatively long flow length, so the cavity is not serious wear, mold maintenance costs are low.

⑤ Compared with the injection molding, the molding equipment, molds and other investment costs are low, so the entire product molding costs are low.

2. Press the molding process

In the press molding, a certain amount of prepared BMC molding is placed in a preheated steel die, and then the mold is closed at a constant speed; the BMC molding is flowed under pressure and filled the entire cavity; The required temperature, the pressure to maintain a certain time, until it completed the physical and chemical process of curing, stereotypes and achieve the best performance when the mold, remove the product.

3. Prepare the work before pressing

BMC Partss as wet premixes contain volatile reactive monomers that should not be removed prematurely before use. Otherwise, these active monomers will evaporate from the BMC material to reduce the fluidity of the material, And even cause performance degradation so that scrap. Of course, for unpacked and unused BMC Parts, it must be re-sealed and sealed for the next time to suppress the use.


① calculation of the amount of feeding and weighing

In general, the first is to know the volume and density of the pressed products, coupled with burrs, burrs and other losses, and then the amount of feeding calculation. Accurate calculation of the amount of charge, to ensure the accuracy of the geometric size of the product to prevent the lack of material or due to excessive material caused by waste and waste materials, etc., have a very direct relationship, especially for the BMC after this molding can not be recycled Thermosetting composite materials, for the preservation of materials, reduce costs, more important practical significance.

In fact, since the shape and structure of the molded product are complicated, the calculation of the volume is complicated and not necessarily accurate, so the loading is often based on the estimated method. For automatic operation of the machine, the amount of feed can be controlled in the total amount of soil within 1.5% or less, and reach 5% or more than this number, it will certainly die in the mold surface flash. This thin layer of excess material in the heating state of the role of high mold temperature, will quickly cure to form a flash.

There are many ways to estimate the amount of charge. Such as the so-called "shape, size simple estimation method", "density comparison method" and "injection type comparison method" and so on.

With the above method to estimate the basic amount of charge, and several times the pressure test, you can more accurately get BMC Parts compression molding charge.

② mold preheating

BMC molding is a kind of thermosetting reinforced plastic. For thermosetting plastics, the mold should be preheated to the required temperature before molding. The actual temperature is the same as that of the pressed BMC Parts. Shape and wall thickness, the use of molding equipment and operating environment have a relationship. It should be noted that when the mold temperature does not reach the set value and is uniform, do not feed the mold cavity.

③ placement of the insert

In order to improve the strength of the connecting portion of the molded product or to make it possible to form a conductive path, it is often necessary to place the insert in the article. When you need to set the insert, then in the loading, before pressing the insert should be used in the cavity placed. The inserts should meet the design requirements and, if they are metal inserts, need to be cleaned before use. For larger metal inserts, it is also necessary to preheat them before they are placed to prevent defects such as cracking due to the large difference in shrinkage between the material and the metal.

 In the same cavity, such as the placement of different types, different specifications of the insert, but also should seriously check the placement of the insert. The dislocation of the insert will not only produce waste, but it is more likely to damage the cavity. In short the insert should be placed in place, accurate and fast and reliable.

④ release agent brushing

For the compression molding of the BMC Parts, since sufficient internal release agent has been added to the component at the time of its formulation, it is easier to remove the molded part after the opening, and therefore it is generally not necessary to Brush the outer release agent. However, since the BMC material has a good flowability, it is possible to penetrate into the gap between the connecting surfaces of the molded parts constituting the cavity, and the mold is difficult to be demolded. Therefore, for the newly manufactured or long-used mold, Or after the clear mold, to the mold cavity brushing some of the external release agent is also good. The external release agent used is typically paraffin or zinc stearate.

⑤ installed mold

In the compression molding of BMC Partss, it is noteworthy that the mold operation is appropriate, which will not only affect the flow of the material in the mold cavity, but also affect the quality of the product, especially for the shape and structure Are more complex products of the molding. Therefore, how to put BMC Parts into the die, is a very important issue.