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10 steps in plastic mold design

2020-02-29 hqt

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The task of molding plastic parts is usually proposed by the designer of the part, and its content is as follows:
1. Drawings of conventionally produced parts that have been inspected and signed, and indicate the grade and transparency of the plastic.
2. Specifications or technical requirements of plastic parts.
3. Production output.
4. Samples of plastic parts.
Usually, mold design tasks are presented by plastic craftsmen based on plastic molding tasks. Mold designers design molds based on the task of molding plastic and mold design.
Collect and organize data on product design, molding process, molding equipment, machining and special processing for designing molds.
1.Extract the drawings of plastic parts, understand the use of the parts, analyze the technical requirements of the plastic parts, such as manufacturability and dimensional accuracy.
For example, what are the requirements for the appearance, color transparency and performance of plastic parts, whether the geometry, slope and insert of the plastic parts are reasonable, the degree of molding defects such as welding defects, shrinkage holes, and whether there is post-coating , Such as assembly, plating, gluing, drilling, etc. Select the size with the highest dimensional accuracy of the plastic part to be analyzed, and see if the estimated forming tolerance is lower than the plastic part’s tolerance, and whether it can form a satisfactory plastic part. In addition, it is necessary to understand the plasticization and molding process parameters of plastics.
2. Extract process data and analyze whether the molding methods, equipment models, material specifications, mold structure types and other requirements listed in the process task book are appropriate and can be implemented.
The molding material should meet the strength requirements of plastic parts, and have good fluidity, uniformity, isotropy and thermal stability. According to the use of plastic parts, the molding material should meet the requirements of dyeing, metal plating conditions, decorative properties, necessary elasticity and plasticity, transparency or opposite reflectivity, adhesion or solderability.
3. Determine the molding method-use direct compression, casting or injection molding.
4. Select molding equipment
The mold is made according to the type of molding equipment, so you must be familiar with the performance, specifications and characteristics of various molding equipment. For example, for an injection machine, you should understand the following in terms of specifications: injection volume, clamping pressure, injection pressure, mold installation size, ejector and size, nozzle hole diameter and nozzle ball radius, gate sleeve positioning ring size, mold The maximum and minimum thickness, stroke of the template, etc. For more information, please refer to the relevant parameters.
A preliminary estimate of the mold size is required to determine if the mold can be installed and used on the selected injection molding machine.
5. Specific structural scheme
(1) Determine the mold type
Such as compression mold (open, semi-closed, closed), casting mold, injection mold, etc.
(2) Determine the main structure of the mold type
Choosing the ideal mold structure is to determine the necessary molding equipment and the ideal number of cavities. Under absolutely reliable conditions, the work of the mold itself can meet the technical and production economic requirements of plastic parts. The technical requirements for plastic parts are to ensure the geometry, surface finish and dimensional accuracy of plastic parts. The economic requirement of production is to make the cost of plastic parts low, the production efficiency high, the mold can work continuously, the service life is long, and the labor is saved.
3. There are many factors that will affect the structure of the mold and the individual system of the mold. These factors are very complicated:
1. Cavity layout. According to the geometric characteristics of plastic parts, dimensional accuracy requirements, batch size, ease of mold manufacturing, mold cost, etc., determine the number of cavities and their arrangement.
2. Determine the parting surface. The parting surface should be positioned to facilitate mold processing, venting, demolding and forming operations, and the surface quality of plastic parts.
3. Determine the gating system (shape, position and size of the main flow channel, runner and gate) and the exhaust system (exhaust method, position and size of the exhaust box).
4. Select the ejection method (ejector, ejector, push plate, combined ejection), and then determine the undercut processing method and core extraction method.
5. Determine the cooling and heating method, the shape and position of the heating and cooling grooves, and the installation position of the radiator

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