Structural Design of Screw
In our plastic mold design industry,there are many types of mold structures.For general mold designers,ordinary sliders and inclined roof structures are familiar to everyone,and they can be designed.But for some special and typical molds there will always be a feeling that there is no way to start with the structure.Today I will explain to you the design points of the screw thread mold structure.I hope that the majority of university mold design enthusiasts and partners who want to know more about the screw thread heart pumping structure will be inspired:
There are two types of threads for plastic products: External threads and internal threads.For external threads with low precision,Huff blocks are generally used to form them,while internal threads mostly require thread unloading devices.Here is a brief introduction to the demoulding method of internal threads and the introduction of gears:
1.According to the action mode:
1)The threaded core rotates,and the push plate pushes the product out;
2)The threaded core rotates and retreats at the same time,and the product is naturally separated.
2.According to the driving mode: the types of tooth extraction molds are generally divided into two types: one is the movement of the rack driven by the oil cylinder,and the other is the movement of the chain driven by the motor.The following figure shows the movement of the rack driven by the oil cylinder:
The picture below shows the motor drives the chain to twitch:
3.The twitching principle of the screw tooth mold:the tooth pitch of the braces and the braces must be the same as that of the product,and the braces play a guiding role.Oil cylinder drives rack 1 to move–rack 1 drives gears 2 and 3 to rotate-gear 3 drives gear 4 to rotate-gear 4 and the screw are positioned as one and rotate together,as shown in the figure below:
4. When designing the thread mold, you need to know the tooth pitch. The definition of the thread pitch is the distance that the thread moves in the vertical direction after one rotation, as shown in the figure below:
5. The tooth pitch at the glue position of the product must be the same as that of the screw, otherwise the product will be easily scratched.
6. How to call gears and racks: Hu Bo plug-in can call gears and racks. According to the product ranking in our mold, we can determine the index circle required by our gears directly, and then the gear modules are the same. The gear can be called out as shown in the figure below:
7. The method of calling the rack: the rule of calling with Hu Bo’s external rack is also to follow the formula of (modulus X number of teeth = diameter of the indexing circle)
8. If you want to design a thread mold, you must understand the relationship between the rack and the gear. The following figure shows the relationship between the rack and the gear and the relationship between each gear:
9. Calculation of the number of turns required for the product and the length of the rack: if the number of turns of the tooth is 5, then at least 5 turns are required for the screw to exit. The screw exits for 6 turns. Then you can reversely calculate the rack twitching distance according to the previous page.
