BMC Car Lighting Reflector Mold
Classification &. Application Of BMC Mold
BMC ia a bloock molding compound. BMC is a thermoplastic consisting of polymer resins, variuos insert fillers, fiber reinforced materials, catalysts, stabilizers and tacky pigments. BMC is highly filled and reinforced with short fibers. It is a glass fiber reinforced thermosetting polymer material that can be used in compression molds, injection molds, etc. BMC compression molding is used in a large number of indurstrial production of complex components, such as housings for electrical equipment, automotive components, appliances and tools.
BMC mixing operations can be performed in a variety of ways. There are three methods for mixing glass with paste: continous screw mixer, sigma blade mixer and plow blade mixer. The process of mixing depends on specific product attributes, product from and volume. Depending on the end application, compounds can be formulated to achieve strict dimensional control, flame retardancy, high dielectric strength, corrosion and stain resistance, and color stability. BMC' s outstanding flow characteristics make it ideal for a variety of applications requiring accuracy and dimensional accuracy. The material is available in a variety of colors.
Mold Design Of BMC Mold
Parting surface design
To facilitate product release, to ensure product accuracy, strength, and ease of mold processing and other factors, the selection of the parting surface should consider the following principles:
1.In order to make the product easy to push out and to simplify the ejector mechanism, the position of the parting surface should be left as much as possible in the lower mold after the mold is opened;
2.Minmize the damage of the flash on the appearance of the product, and at the same time, it should be easy to remove the residual flash;
3.Convenient mold manufacturing and mold parts processing;
4.For products with high radial dimensional accuracy, the effect of flash thickness on the accuracy of the product should be considered, and the vertical parting surface can be used to ensure the radial accuracy of the product.
5.To ensure product strength, to avoid sharp coners and thin walls.
The design of the parting surface is very important. It is necessary to design the product in the early stage of the mold design and draw the design drawings of the parting type to ensure that the product can be demolded smoothly and the production is easy.
Processing accuracy requirements
The new mold processing accuracy mainly has three aspects:Dimensional tolerance, shape and position tolerance and surface roughness. The machining accuracy that we usually require for mold manufacturers is mainly dimensional tolerance and surface roughness. The dimensional tolerance are roughly diviede into:external dimensions and cavity dimensions. The two types are relatively loose for the external dimensions of the mold, and the actual processing size and the theoretical size error of the mold drawing shall not exceed +1.5mm. The dimensional accuracy of the face mold cavity must be strictly controlled according to the drawings, generally not exceeding 0~0.1mm. The surface roughness of the mold we are referring to generally refers to the surface roughness. After the treatment, the roughness of the mold cavity is generally required, and the rest is. We can propose the corresponding mold surface machining accuracy according to the actual product surface requirements.
Mold draft design
As the BMC product shrinks after cooling, the product tightly wraps the mold core and the raised portion of the cavity. In order to facilitate the smooth removal of the product and to prevent it from hitting or scratching the product during demoulding, when designing the BMC product, both the inner and outer surfaces should have sufficient draft angles along the stripping direction.
When designing, you should pay attention to the following two aspects:
1.When molding larger BMC products, it is required that the internal surface demoulding slope is greater than the external surface demolding slopw;
2.Commonly used stripping slope value of 1 to 1.5 degress, can also be as small as 0.5 degrees.
About BMC Material
The BMC material is an abbreviation of bulk molding compound, namely a bulk molding compound. Domestic often referred to as unsaturated polyester bulk molding compound. Its main raw material is GF(chopped glass fiber), UP(unstaturated resin), MD(filler) and a variety of additives have benn mixed with a mass of prepreg. BMC pellts have excellent electrical properties, mechanical properties, heat resistance, chemical resistance, and adapt to a variety of molding processes, they can meet the performance requirements of various products, and are therefore increasingly used by a wide range of uners facorite.
Molding Process Of BMC Materials
The first is to properly grasp the barrel temperature and mold temperature. Under normal cirumstances, in the molding molding process, to keep the BMC material at the barrel temperature, keep the flow dynamics of low viscosity for a long time, the general barrel temperature should meet the low limit of BMC. The barrel temperature is generally divided into two or three sections, the lower end of the hopper is lower, and the temperature near the nozzle end is higer. Generally, the difference is 20~60 degree, and the mold temperature is generally controlled at 135~185 degree.
Next, we must ensure that the injection pressure used is suitable. Considering the limited fluidity of the BMC material itself, the curing is fast and the mold structure is complicated, so the injection pressure should be higher pressure, generally 80~160MPa. At the same time, the appropriate injection speed should be maintained. The increase of injection speed helps to improve the surface quality of the plastic parts and shorten the curing time, but it is not conducive to exhaust gas and increase the orientation of the glass fiber. Therefore, a lower injection speed should be adopted on the premise of ensuring the surface quality of the plastic parts.
In addition to these factors, care must be taken to determine the molding cycle of the material. In fact, the size and complexity of different plastic parts are different. The process time of each section of BMC material processing is different. The general injection time is 2~20s, and the holding time is 10~20(thickness).
Equipment For BMC Injection Molding
In BMC, due to the addition of glass fiber, the equipement used is somewhat different from the usual thermosetting plastic injection molding equipment. The injection molding machine, plunger type and screw type can all be used.
Whether it is a screw type or a plunger type, a squeeze type feeding device must be added to force the material into the cartridge. The charging device uses a plunger type pressurized feed material.
2)Injection molding system.
Because the injection quantity of theplunger injection molding machine is accurate and constant, the glass fiber is dispersed in the molten material with less damage. Therefore, the plunger injection molding machine is used more, but the exhaust is inconvenient.
In the injection molding of BMC, it is very important to control the temperature of the barrel. Theremust be a set of control system to control the temperature of ensure that the temperature from the feeding section to the nozzle is the best. At present, the use of constant temperature water or constant temperature oil heating. Electric heating can also be used.
4)Mold clamping device.
More use of mechanical, hydrsulic and fully-hydraulic type of serveral mold clamping device.
The BMC injection mold is somewhat different from the usual thermoplastic and thermost injection molding. The main reason is that the BMC has a low shrinkage rate, so it should be changed when desining the cavity size.
The advantage BMC Injection Molding
The advantage of BMC injection molding machine is that is can be automatically feild, eliminating the complicated steps of manual weighing materials, not only saving a lot of labor, but also producing more accurate and beautiful products, which can improve the profit of enterprise products and effectively reduce production costs. When using BMC injection machine for production and processing, only one person can complete the molding step independently, which is easy and conveninent, and also ensures the hidden dangers caused by the operator directly contacting the molding compound. Due to the large amount of glass fiber in the raw material of the unsaturated polyester resin molding compound, the human skin may have itching stmptoms if it is directly contacted. Overtime, serious consequences of occupational diseases may occur. The BMC injection molding machine reduces the oppprtunity for the operator to directly contact the raw materials. It is only necessary to put 20~30kg of raw materials into the injection molding machine hopper, which can realize multiple clamping molding, which is alomost the same as ordinary thermoplastics.
a. Product reverse engineering; product design optimization.
b.The mould design with CAE analysis, shorten lead time, improve molding efficiency.
c.Communication on the technical points in-time.
d.Weekly reporter for you about the mould machining progress and mould finishing schedule
e.Mould test and sample delivery in-time.
f.Supply trial molding parameters.
g.Spare parts and detailed parts list.
a.One-year warranty since the date of delivery (except manmade damages from use)
b.Under warranty, if customer encounters problem in mould quality, we shall supply the components free.
c.Our experienced engineers will provide the technical solutions to any problem occured in customers' mould operation.