injection mould design

1 Composition of injection mold. It is mainly composed of molding parts (pointing to the parts that form the cavity in the moving and fixed parts of the mold), pouring system (the channel through which the molten plastic enters the mold cavity from the nozzle of the injection machine), guide parts (so that the mold can be accurately aligned when the mold is closed), the push mechanism (after the mold is parted, the plastic is pushed out of the cavity), the temperature control system (to meet the mold temperature requirements of the injection process), the exhaust system (the air in the cavity during molding and the volatile gas of the plastic itself are discharged out of the mold, Exhaust grooves are often provided on the parting surface) and supporting parts (parts used to install fixed or supported parts and other mechanisms), and sometimes lateral parting and core pulling mechanisms.

2. Design steps of injection mold

1. Preparation before design

(1) Design the mandate

(2) Familiar with plastic parts, including their geometry, the use requirements of plastic parts, and the raw materials of plastic parts

(3) Check the molding processability of plastic parts

(4) Clarify the model and specifications of the injection machine

2. Develop the molding process card

(1) Product overview such as diagram, weight, wall thickness, projection area, external dimensions, whether there are side recesses and inserts

(2) Overview of the plastics used in the product such as product name, model, manufacturer, color, drying situation

(3) The main technical parameters of the selected injection machine, such as the relevant size between the injection machine and the installation mold, screw type, power
(4) injection machine pressure and stroke

(5) Injection molding conditions such as temperature, pressure, speed, clamping force, etc

3. Injection mold structure design steps

(1) Determine the number of cavities. Conditions: maximum injection volume, clamping force, product precision requirements, economy

(2) Select the parting surface. It should be based on the principle of simple mold structure, easy parting and does not affect the appearance and use of plastic parts

(3) Determine the layout of the cavity. Use a balanced arrangement whenever possible

(4) Determine the gating system. Including main stream, shunt, gate, cold cavitation, etc.

(5) Determine the demolding method. Different demolding methods are designed according to the different parts of the mold left in the plastic parts.

(6) Determine the structure of the temperature control system. The temperature control system is mainly determined by the type of plastic.

(7) When determining that the die or core adopts the insert structure, the workability and installation and fixing method of the propositionally dividing the insert and the inserting at the same time.

(8) Determine the exhaust form. Generally, the exhaust can use the mold parting surface and the gap between the pushing mechanism and the mold, and for large and high-speed molded injection molds, the corresponding exhaust form must be designed.

(9) Determine the main size of the injection mold. According to the corresponding formula, calculate the working size of the molded parts and determine the thickness of the side wall of the mold cavity, the thickness of the cavity floor, the core gasket, the moving template, the thickness of the cavity plate of the block cavity and the closing height of the injection mold.

(10) Choose a standard mold base. According to the main size of the injection mold designed and calculated, the standard mold base of the injection mold is selected, and the standard mold parts are selected as much as possible.

(11) Sketch the structure of the mold. Drawing a complete structural sketch of the injection mold, drawing the mold structure diagram is a very important work of mold design.

(12) Check the relevant dimensions of the mold and injection machine. Check the parameters of the injection machine used: including the maximum injection volume, injection pressure, clamping force, and the size of the mounting part of the mold, the mold opening stroke and the ejection mechanism.

(13) Review of injection mold structure design. A preliminary examination is carried out and the consent of the user is obtained, and it is necessary to confirm and modify the request made by the user.

(14) Draw the assembly drawing of the mold. Clearly indicate the assembly relationship, necessary dimensions, serial numbers, schedules, title blocks and technical requirements of each part of the injection mold (the content of the technical requirements is as follows: a. Performance requirements for the mold structure, such as assembly requirements for the pushing mechanism and core pulling mechanism; b. Requirements for mold assembly process, such as the fitting gap of the parting surface, the parallelism of the upper and lower parts of the mold; c. Requirements for the use of molds; d. Anti-oxidation treatment, mold number, engraving, oil seal and storage requirements; e. Requirements for mold testing and inspection. (15) Drawing mold parts. The order of disassembling and drawing part drawings from mold assembly drawings or component drawings is: first inside and then outside, first complex and then simple, first forming parts and then structural parts.

(16) Review the design drawings. The final review of injection mold design is the final check of injection mold design, and more attention should be paid to the processing performance of parts.

3. Audit of injection molds

1. Basic structure

(1) Whether the mechanism and parameters of the injection mold match the injection machine.

(2) Whether the injection mold has a mold clamping guide mechanism and whether the mechanism design is reasonable.

(3) Whether the selection of parting surface is reasonable, whether there is a possibility of flash generation, and whether the plastic parts are stuck on the moving mold (or fixed mold) side of the ejection release mechanism.

(4) Whether the layout of the cavity and the design of the gating system are reasonable. Whether the gate is suitable for plastic raw materials, whether the gate position is comparable, whether the geometry and size of the gate and runner are appropriate, and whether the flow ratio quantity is reasonable.

(5) Whether the design of the molded parts is reasonable.

(6) Ejection release mechanism and lateral male type. or whether the core pulling mechanism is reasonable, safe and reliable. There is no interference and bite. (7) Whether there is an exhaust mechanism and whether its form is reasonable. (8) Whether a temperature regulation system is required. Whether its heat source and cooling method are reasonable.

(9) Whether the structure of the supporting parts is reasonable.

(10) Whether the external dimensions can ensure the installation, whether the fixing method is selected reasonably and reliably, and whether the bolt hole used for installation is consistent with the position of the screw hole on the injection mechanism and the fixed mold fixing plate.

2. Design drawings

(1) Assembly drawings

Whether the assembly relationship of the parts is clear, whether the matching code is properly and reasonably marked, whether the labeling of the parts is complete, whether it corresponds to the serial number in the schedule, whether the relevant description has a clear mark, and how standardized the entire injection mold is. (2) Single-part drawings

Whether the part number, name, and processing quantity are accurately marked, whether the dimensional tolerances and various tolerances are reasonable and complete, whether the parts of the molded parts that are prone to wear are reserved for regrinding amount, which parts have ultra-high precision requirements, whether this requirement is reasonable, whether the material cushions of each part are appropriate, whether the heat treatment requirements and surface roughness requirements are reasonable.

(3) Cartographic methods

Whether the drawing method is correct, whether it meets the national standards, and whether the geometry and technical requirements expressed by the drawing are easy to understand. 3. Injection mold design quality

(1) When designing the injection mold, whether the process characteristics and molding performance of the plastic raw materials are correctly considered, the impact that the type of injection machine may have on the molding quality, and whether corresponding preventive measures are taken in the design of the injection mold that may occur during the molding process.

(2) Whether the requirements of plastic parts for injection mold guiding accuracy are considered, and whether the guide structure is reasonably designed.

(3) Whether the working size calculation of the molded parts is correct, whether the accuracy of the product can be guaranteed, and whether it has sufficient strength and rigidity.

(4) Whether the supporting parts can ensure that the mold has sufficient overall strength and rigidity.

(5) Whether the mold trial and mold modification requirements have been considered

4. In terms of assembly and disassembly and handling conditions, whether there are slots, holes, etc. that are convenient for assembly and disassembly, and whether they are marked.