When it comes to toys, most people probably think of LEGO. LEGO toys believe that everyone is particularly familiar with the world. It seems to be able to build a new world by using your imagination and putting LEGO blocks together. Many people have an endless demand for it. A small piece of building blocks, built out of a magical world. A world created by you, anything you want, as long as there is enough imagination and enough LEGO blocks.
But how to make so small and so many LEGO blocks, and still ensure that the clearance is less than 2 microns after each block is put together, and must also ensure a high enough rate of LEGO bricks to meet the standard? In fact, LEGO mainly relies on the injection molding process, which requires high injection molding tolerances, LEGO blocks are a typical example of the application of injection molding technology, you can still see the marks left after injection molding in the surface of LEGO blocks.
Injection molding is widely used in toys
When it comes to injection molding, it is actually a very widely used process, Injection molding tolerances are critical because the toy industry is very demanding in terms of appearance and toy play experience, and most toys rely on this process to make it happen. Injection molding is a common manufacturing method in which heated liquid molten material is injected into a mold after passing through a long chamber, which is located at the end of the chamber and the fluid plastic is forced to cool through the nozzle, closing the grinder, and the semi-finished product exits the press as the plastic cools and cures. In this process, to get high precision as well as high tolerance of injection molded parts, we can start from several aspects.
Aspects of improving injection molding tolerances
Mold design accuracy
To improve the plastic injection molding tolerances, such as the form or basic structure of the mold, not only the parting surface of the mold should be considered for the molding and de-molding of the plastic part, but also the fluidity of the melt during the molding of the plastic part, and the distribution of the sprue, the location of the gate, the exhaust, the cooling or heating of the mold, etc. In injection molding, the mold cavity has to bear high pressure, if the mold stiffness is not enough, it will make the mold deformation and thus reduce the standard injection molding tolerances, so the influence of the cavity structure on the stiffness needs to be fully considered. It is necessary to overcome the wear and deformation of the mold, in which the manufacturing accuracy of the mold is the main factor that affects the injection molding tolerances.
Types and grades of plastics, such as plastic shrinkage, flow, moisture, and volatile content. Different plastic materials have different shrinkage differences and fluctuations. These can lead to fluctuations in injection molding tolerances.
Forming process-related factors
Temperature、 pressure、 time. Due to the performance of the machinery itself and the practical experience of the operator, the process parameters often fluctuate, resulting in differences and changes in the shrinkage rate of the material, which affects the plastic injection molding tolerances.
Changes caused by the external environment of the molded workpiece
The temperature and humidity of the environment, the degree of crystallization of molecules, and the orientation of fillers, or improper storage lead to expansion and post-shrinkage of molded products. The tolerance of injection molding can change due to the external environment.
For example, the shape and wall thickness of the workpiece, the measuring environment, and the reading habits of the measuring personnel can affect the tolerance of injection molded parts.
Focus on injection molding tolerances
From these aspects, there are many subjective and objective factors that can affect the tolerances of injection molded parts, but it is obvious that injection molding still has many advantages, such as its ability to use a wide range of polymers as raw materials, it’s very smooth surface, its high production speed, and its excellent dimensional control system, which makes it easy to explain why LEGO bricks are manufactured by injection molding.
At any time WayKen can provide you with a professional rapid injection molding service, and we can do the tolerances of injection molded parts as tight as +/-0.0005” (+/-0.0127mm) to +/-0.002” (+/-0.05mm), and the min roughness to Ra 0.05μm, please feel free to contact us for your toy prototype.