Plastic injection molding
makes plastic products acquire complicated shape and details. Under the conditions that maintain steady tolerance zone and high surface quality, mass production can be realized. For mold manufacturers, the quality of mold has direct influence on production efficiency of injection molding, deciding product quality and additional value of products further. So, how to highly cool plastic products in the minimum cycle has become consideration factor in design and manufacturing of conformal cooling mold.
The principle of conformal cooling is that rapidly reduce temperature of plastic products by using a uniform continuous pattern. Injection molding products cannot be ejected from mold during cooling, until being cooled. After that, plastic products are taken from mold. Any hot spots can delay injection molding cycle of plastic products which may result in warping and sunken of plastic products after demolding and cause damage to surface quality. Quick chilling is realized by cooling liquids flowing through the channel inside mold and taking the heat of injection molding parts away. The velocity and homogeneity of cooling effectiveness are depended by fluid pathway and the speed that cooling liquid flow through channel. The traditional cooling channel inside mold is acquired through secondary processing. Through cross drilling, inside network of straight pipe is formed. The flow velocity and direction are adjusted through built-in fluid plug. However, the method has limitation. The shape of flowing network is limited. Therefore, cooling channel is far away from the surface of mold, reducing cooling efficiency. Besides, it needs extra time for processing and assembling. The risk that blind channel network may be blocked also exists. In addition, under the complicated situation, for obligating processing of cooling channel, the mold is divided several parts for manufacturing, then, those parts are jointed together, which results in extra manufacturing and reducing service life of mold.
The difference of conformal cooling from traditional cooling is that the shape of cooling channel change with the shape of injection molding products, instead of straight linear. The cooling channel can well figure out inconsistent distance from traditional cooling channel to surface of mold cavity so that plastic products can be cooled equably with higher cooling efficiency. 3D printing help designers break away from the limiting of cross drilling. Internal channels closer to cooling surface of mold can be designed, having smooth corner, higher rate of flow, increasing the efficiency that heat is transferred to cooling liquids. Different cooling circuits also can be designed based on cooling requirements, aiming at heat dissipation at a consistent velocity, promoting homogeneity of heat dissipation. Flowing rate of cooling liquids is vital for cooling velocity of mold. Smooth corner is essential for reducing pressure loss along the channel. For metal powder, melting 3D printing is chosen so that metal powders can be produced inside cooling channel whose diameter is as small as 1.4mm. A benefit of powder laying 3D printing technology is that powder melting can cause surface with slight textures. The textures can increase contact area of cooling liquids, bringing better heat transferring effectiveness and improving cooling efficiency. What'more, it also forms small turbulences inside channels, realizing self-cleaning of channel.
Through conformal cooling plastic injection mold manufactured by 3D printing, processing efficiency of injection mold can be improved to as high as 70%. For example, injection time of a mold of ice scraper can be reduced from 80 seconds to 40 second by using additive manufacturing, which means that production rate of injection molding products are two times of original production rate. Other main advantages of conformal cooling mold manufactured by additive manufacturing include: more uniform plastic products can be formed, realizing non-defects, in case of shrinkage concave caused by uneven cooling velocity. Moreover, when developing injection molding products, the method is helpful for finishing development of products with less iteration. Without doubt, more advantages also contain that additive manufacturing is faster than traditional method with less processing and jointing of cooling channel when making complicated mold. It should be noted that the surface of mold made by additive manufacturing has poor surface precision. Demanded surface precision should be acquired though later finishing machining and polishing. In the link, advantages of traditional machining form complementation with advantages of additive manufacturing.