Asia Billion is a custom precise injection molding companies in China. this project is a micro molding part for medical industry. the material is medical grade PP, the part size around diameter 3.0 x 4.0 mm with thread. it is a 32 cavities hot runner mold with 32 drops hot runner system. the part is used for some medicine packing with huge volume each year. if you interest in it or want to know more about it , please contact us freely .
micro injection molding
Core surface finish:
Medical grade PP
Cavity surface finish:
No of Cavities:
S136 with heat treated and nitridation
Type of gating:
pin point gate
S136 with heat treated and nitridation
Lead time for T1
|Clean cold water|
1 000 000
Place of Origin
1. medical plastic injection molding . it is a very small part with thread
2. automatically un-screwing for the tinny thread
3. Complex ejector system between the unscrewing , the ejector pin is inside the un-screwing mold insert
4. very precision dimension control up to +/-0.02mm
Here Asia Billion would like to share with you for our points for micro precision plastic molding project experience as below.
Mold processing and key points:
In terms of molds, the requirements for micro-injection for processing equipment are much higher than for conventional injection molding. Micro-injection usually has two trends in mold processing: the first is to use mirror spark machining. In order to ensure high precision, it is best to use graphite electrodes for EDM because the loss of graphite electrode is better than ordinary copper electrodes. A lot smaller.
The second most common processing method is the use of electroforming molds. The electroforming process ensures very high precision, but the disadvantage is that the processing cycle is long, each hole must be processed independently, and if there is slight damage in production, it cannot be repaired. Only damaged acupuncture points can be replaced. Like the anti-slip lines and threads of medical products in this case, electroforming is required to achieve these subtle structures.
In terms of molds, mold temperature is also a very important parameter for micro injection molding. In the face of high-end customers, the current common practice is to use the concept of high-gloss injection molding to introduce rapid heating and cooling systems.
In theory, high mold temperature is very helpful for micro-injection. For example, it can prevent thin wall filling from being difficult and lack of material. However, too high mold temperature brings new problems, such as lengthening of the cycle and shrinkage deformation after mold opening. Therefore, it is quite important to introduce a new mold temperature control system. During the injection molding process, the mold temperature can be increased (can exceed the melting point of the plastic used), so that the melt can quickly fill the cavity and prevent the melt from lowering during the filling process. The filling is incomplete quickly, and when the mold is released, the mold temperature can be quickly lowered, kept at a temperature slightly lower than the plastic heat distortion temperature, and then the mold is ejected.
In addition, since the micro-injection molding process is a product of the mass of milligrams, if the ordinary gating system is used to inject the product, even after the optimization and improvement, the material quality ratio in the product and the gating system is still 1 :10. Less than 10% of the material is injection molded into micro-products, resulting in a large number of gating system aggregates, so micro-injection should usually use a hot runner gating system.
Material selection points:
In terms of material selection, it is recommended to select some general engineering plastics with low viscosity and good thermal stability in the early stage of development.
The low viscosity material is chosen because the viscosity of the melt is low during the filling process, the resistance of the entire casting system is relatively small, the filling speed is fast, the melt can be smoothly filled into the cavity, and the melt temperature is not significantly reduced. Otherwise, cold joints are easily formed on the product, and the molecular orientation is less during the filling process, and the properties of the obtained product are relatively uniform.
If a high-viscosity plastic is selected, not only the filling is slower, but also the feeding time is longer, and the shearing flow caused by the feeding tends to cause the chain molecules to be oriented in the shear flow direction, and in this case, the cooling state is below the softening point. It is frozen, and this degree of freezing orientation is likely to cause internal stress of the product, and even cause stress cracking or warping deformation of the product.
The reason for the good thermal stability of plastics is that the materials are prone to thermal degradation due to the long-term residence in the hot runners or by the shearing action of the screw, especially for heat-sensitive plastics, even in a short cycle time, due to material injection. The small amount of residence time in the casting system is relatively long, resulting in a considerable degree of degradation of the plastic, so the heat sensitive plastic is not suitable for micro injection molding.
Injection molding process points:
Finally, we look at the requirements of micro molding in the injection molding process. In the injection molding process, we need to consider the gas mark and stress problems of the gate. It is usually necessary to use multi-stage injection molding to ensure that the material can be filled in a steady flow state.
In addition, it is necessary to consider the size of the holding time. Too small a holding pressure will cause the product to shrink, but excessive pressure will cause stress concentration and size.
In addition, the time the material stays in the material tube is also strictly monitored. The residence time of the material in the material tube is too long, which may cause the degradation of the material to affect the function of the product. It is recommended to carry out standard parameter control on the process parameter management. It is best to do DOE verification before mass production, and all the changes in production should be re-tested for size and function.
As a branch of the injection molding field, micro-injection is developing in the direction of high dimensional accuracy, high functional requirements, and high appearance requirements. Only through strict control and continuous improvement of various processes such as molds, equipment, materials, and processes can it be satisfied. The development of the field.
Equipment selection points:
In terms of equipment selection, due to the size of the micro-injection parts of the micron-sized products, it is preferable to use an injection machine with a injection volume of milligrams.
The injection unit of this type of injection machine generally adopts a screw-plunger combination type, the plasticization of the material is completed by the screw part, and the melt is injected into the cavity by the plunger. The screw plunger injection molding machine can combine the high precision of the screw with the high speed of the plunger device to ensure the precision and filling speed of the production process.
In addition, such an injection machine usually consists of a mold clamping mechanism, an injection system, a pneumatic release mechanism, a quality inspection mechanism, and an automatic packaging system. A good quality inspection system guarantees the yield of micro-precision injection molded products and monitors fluctuations in parameters throughout the process.
If you need to find a good long-time partner for precision injection molding and micro molding project, you can contact Asia Billion freely to support your project.