Reasonable mold design is a prerequisite for the success or failure of molds, and the design of plastic molds is particularly important. There are n ways to mold the same structure,. The molding method determines the structure and processing cost of the mold, the product parting line, and the service life of the mold. More importantly, different parting and molding methods also determine the appearance of the product. Let's take a look at some basic points to consider in plastic mold design:

First,Mold opening direction

first.After determining the direction of the mold opening, an appropriate parting line can be selected to avoid any reverse bending in the mold opening direction, in order to improve the appearance and performance.

second. After determining the mold opening direction, the reinforcing ribs, buckles, protrusions, and other structures of the product should be designed to be as consistent as possible with the mold opening direction to avoid core pulling, reduce seam lines, and extend the mold life.

Second,Product wall thickness

first.Uneven wall thickness can cause porosity and weld marks.

second .Uneven wall thickness can cause surface shrinkage of plastic products.

third.All kinds of plastics have a certain range of wall thickness, generally 0.5~fourthmm. When the wall thickness exceeds fourthmm, it will cause problems such as long cooling time and shrinkage, and the product structure should be considered to be changed.

Third,snap-fit

first,Design the buckle device to share multiple buckles simultaneously, so that the overall device will not be unable to operate due to damage to individual buckles, thereby increasing its service life. Additionally, consider adding more filters and rounded corners to increase strength.

second,The tolerance requirements for the relevant dimensions of the buckle are very strict, and too many reverse buckle positions can easily cause damage to the buckle; On the contrary, if there are too few reverse positions, it is difficult to control the assembly position or the combination parts may become too loose. The solution is to reserve a way to easily add glue for mold modification.

Fourth,Draft angle

first,Appropriate demolding slope can avoid product fraying (flower pulling). The demolding slope of a smooth surface should be ≥ 0.5 degrees, with fine grain (sand surface) surfaces greater than first degree and coarse grain surfaces greater than first. 5 degrees.

second,Appropriate demolding slope can avoid product top damage, such as top whitening, top deformation, and top breakage.

third, When designing products with deep cavity structures, the outer surface slope should be greater than the inner surface slope as much as possible to ensure that the mold core does not deviate during injection molding, obtain uniform product wall thickness, and ensure material strength at the opening of the product.

Fifth,stiffener

first,The rational application of reinforcing bars can increase product rigidity and reduce deformation.

second, The thickness of the reinforcing rib must be ≤ (0.5~0.7) t of the product wall thickness, otherwise it will cause surface shrinkage.

third, The single-sided slope of the reinforcing rib should be greater than the first. 5 ° to avoid top damage.

Sixth,Core pulling, sliding mechanism and avoidance of plastic molds

first,When the plastic part cannot be smoothly demolded according to the mold opening direction, a core pulling slider mechanism should be designed. The sliding block of the core pulling mechanism can form complex product structures, but it is prone to defects such as seam lines and shrinkage, which increase mold costs and shorten mold life.

second,When designing injection molded products, if there are no special requirements, try to avoid core pulling structures as much as possible. If the axial direction of the hole and the direction of the rib are changed to the mold opening direction, methods such as using the cavity core to penetrate can be used.

Seventh,Integrated hinge

first,By utilizing the toughness of PP material, hinges can be designed to be integrated with the product.

second,The size of the film used as a hinge should be less than 0.5mm and kept uniform

third,When injecting integrated hinges, the sprue can only be designed on one side of the hinge.

Eighth,Welding (hot plate welding, ultrasonic welding, vibration welding)

first, Welding can improve the connection strength.

second,Welding can simplify product design.

Ninth,insert

first,Inserting inserts into injection molded products can increase local strength, hardness, dimensional accuracy, and provide small threaded holes (shafts) to meet various special requirements. At the same time, it will increase product costs.

second,The embedded parts are generally made of copper, but can also be other metals or plastic parts.

third,The part embedded in plastic should be designed with anti rotation and anti pull structures. For example: embossing, punching, bending, flattening, shaft shoulder, etc.

fourth,The plastic around the embedded parts should be appropriately thickened to prevent stress cracking of the plastic parts.

fifth,When designing inserts, full consideration should be given to their positioning in the mold (holes, pins, magnetism).

Tenth,rounded corner

first,Too small a fillet may cause stress concentration in the product, leading to cracking.

second,Too small a fillet may cause stress concentration in the plastic mold cavity, leading to cavity cracking.

third, Setting reasonable rounded corners can also improve the machining process of the mold, such as directly milling the mold cavity with an R-knife, avoiding inefficient electrical machining.

fourth,Different rounded corners may cause movement of the parting line, and different rounded corners or cleaning corners should be selected based on the actual situation.

Eleventh,hole

first,The shape of the hole should be as simple as possible, usually circular.

second,The axial direction of the hole is consistent with the mold opening direction, which can avoid core pulling.

third,When the aspect ratio of the hole is greater than second, the demolding slope should be set. At this point, the diameter of the hole should be calculated based on the small diameter size (maximum physical size).

fourth,The aspect ratio of blind holes generally does not exceed the fourth.