When it comes to toys, most people probably think of LEGO. LEGO toys believe that everyone is particularly familiar with the world. It seems like you can build a new world using your imagination and assembling LEGO bricks. Many people have an endless demand for it. A small piece of block from which a magical world is built. A world you can create, whatever you want, as long as you have enough imagination and enough LEGO bricks.
But how can you make so many and so small LEGO bricks and still ensure that the gap after each block is assembled is less than 2 microns, while still ensuring a high enough number of LEGO bricks to meet the standard a be fulfilled? In fact, LEGO mainly relies on the injection molding process, which requires high injection molding tolerances. LEGO bricks are a typical example of the application of injection molding technology. Traces can still be seen on the surface of LEGO bricks after injection molding.
Injection molding is often used in toys
Injection molding is a very common process. Tolerances in injection molding are crucial because the toy industry has very high demands in terms of appearance and play experience and most toys rely on this process. Injection molding is a common manufacturing process in which heated molten liquid material is injected into a mold after passing through a long chamber. At the end of the chamber, the liquid plastic is forced to cool through the nozzle, which closes the mill and the semi-finished product exits the press as the plastic cools and hardens. To achieve high precision and high tolerance of injection molded parts with this process, we can take several aspects.
Aspects to improve injection molding tolerances
Mold design accuracy
In order to improve tolerances in plastic injection molding, such as the shape or basic structure of the mold, not only the parting surface of the mold must be taken into consideration when molding and demolding the plastic part, but also the fluidity of the melt during plastic part molding, sprue distribution, etc. Sprue position, exhaust, mold cooling or heating, etc. During injection molding, the mold cavity must withstand high pressures. If the rigidity of the mold is not sufficient, the mold will deform and thus reduce the standard tolerances in injection molding. Therefore, the influence of cavity structure on stiffness must be fully considered. Mold wear and deformation must be overcome. Mold manufacturing accuracy is the main factor affecting injection molding tolerances.
Plastic materials
Types and classes of plastics, such as: B. Shrinkage, fluidity, moisture and volatile content. Different plastic materials have different shrinkage differences and fluctuations. This can lead to fluctuations in injection molding tolerances.
Factors related to the forming process
Temperature, pressure, time. Due to the performance of the machine itself and the practical experience of the operator, process parameters often fluctuate, resulting in differences and changes in the material shrinkage rate, which affects tolerances in plastic injection molding.
Changes caused by the external environment of the formed part
The temperature and humidity of the environment, the degree of crystallization of the molecules and the orientation of the fillers or inadequate storage lead to the expansion and contraction of molded products. Injection molding tolerance may change due to external environment.
Other factors
For example, the shape and wall thickness of the workpiece, the measuring environment, and the reading habits of measuring personnel can influence the tolerance of injection molded parts.
Focus on injection molding tolerances
With this in mind, there are many subjective and objective factors that can affect the tolerances of injection molded parts. However, it is clear that injection molding still offers many advantages, such as: Such as the ability to use a wide range of polymers as raw materials, its very smooth surface, its high production speed and its excellent dimensional control system. So it's easy to explain why LEGO bricks are made by injection molding.
