Plastic injection mold
can make plastic products in daily life acquire complicated shapes and details. Under the circumstance that maintains stable tolerance zone and high surface quality of products, plastic injection mold realizes mass production.
For mold manufacturers
, the quality of mold has direct influence on the production efficiency of plastic injection and quality of product, determining additional value of products further. So, how to efficiently cool plastic products in the minimum period becomes the critical consideration factor for design and manufacturing of conformal cooling plastic injection mold.
Cooling plays a key role.
1. Conformal cooling break away from the limitation of conventional methods
The principle of conformal cooling is that the temperature of plastic injection part is decreased sharply by using a uniform continuous method. The plastic injection part cannot be taken out from the mold during cooling until it is cooled adequately. Then, the plastic injection part is ejected from the mold. Any hot spots can extend injection cycle of injection part, which may cause warping and riding of plastic injection part, damaging surface quality of plastic injection part.
Rapid cooling refers to that refrigerants flow through passageway inside mold and take the heat of injection part away. Velocity and homogeneity of cooling depend on fluid passageway and velocity that cooling liquids flow through the passageway.
Traditional cooling channel inside mold is realized by secondary processing. Cross drill forms internal network of straight pipes and flow velocity and direction is adjusted by inbuilt fluid plug. The method has limitation and the shape of waterway network is limited. So, the cooling channel is far away from the surface of mold and reduces cooling efficiency. Moreover, it also has to face with extra processing and assembling and the risk that channel of blind spots may also be blocked. What's more, under complicated situation, for obligating processing of cooling channel, the mold should divided into several parts for manufacturing, then, the parts are jointed into a mold again, which result in extra manufacturing chain and reduce service life of mold.
The difference between conformal cooling and traditional cooling is that the shape of cooling channel varies with the shape of plastic injection products. The channel is not straight any more. The cooling channel can figure out inconsistent distance between traditional cooling channel and surface of mold cavity, making plastic injection products be cooled equably and having high cooling efficiency.
2. 3D printing
3D printing help people get rid of the limitation of cross drill. Now, internal passageways closer to cooling surface can be designed, having smooth corners and higher flow, increasing the efficiency of heat transfer to cooling liquid. What’s more, different cooling circuits can be designed to meet different cooling requirements, for heat dissipation at consistent velocity, promoting homogeneity of heat dissipation. The flow rate of cooling liquid is critical for cooling velocity of mold. So, smooth corner is necessary to reduce pressure loss along the passageway.
Metal powders can choose melting 3D printing, which also can be produced in cooling channel whose diameter is as small as 1.4mm. One of advantages of 3D printing of laying powder is that powder melting causes surface having mild texture. The texture structure increases surface area of cooling contacting, causing better heat transfer effectiveness and improving cooling efficiency further. It also forms small turbulence inside channel and realizes self-cleaning inside channel.
3. 3D printing brings additional values to plastic injection products
Conformal cooling plastic injection mold made by 3D printing can improve processing efficiency of plastic injection mold by as high as 70%. In terms of mold of ice scraper, through additive manufacturing, injection time can be reduced from 80 seconds to 40 seconds, which means that the production rate of plastic injection parts is 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; besides, development of products can be completed with less iterations. Other advantages include that when manufacturing complicated mold, additive manufacturing is faster than conventional methods without the processing and jointing of cooling channel.
It should be noticed that the mold made by additive manufacturing has less surface accuracy. The required surface accuracy needs later finish machining and polishing. In this link, the advantages of traditional machining and additive manufacturing form complementation.