1 Composition of injection mold. It mainly consists of molding parts (referring to the parts that make up the mold cavity of the moving and fixed mold parts), pouring system (the channel through which the molten plastic enters the mold cavity from the nozzle of the injection machine), guiding parts (to make the mold accurately aligned when the mold is closed), pushing mechanism (the device that pushes the plastic out of the mold cavity after the mold is split), temperature regulating system (to meet the mold temperature requirements of the injection process) The exhaust system (the air in the mold cavity and the gas volatilized by the plastic itself are discharged from the mold during molding, and the exhaust groove is often set on the parting surface) and the supporting parts (used to install and fix or support the molding parts and other parts of the mechanism) are composed, and sometimes there are side parting and core-pulling mechanisms.
2. Design steps of injection mold
1. Preparation before design
(1) Design assignment
(2) Familiar with plastic parts, including their geometric shape, use requirements of plastic parts, and raw materials of plastic parts
(3) Check the molding process of plastic parts
(4) Specify the model and specification of the injection machine
2. Formulate forming process card
(1) Product overview, such as schematic diagram, weight, wall thickness, projected area, overall dimensions, whether there are side recesses and inserts
(2) Overview of plastics used in the product, such as product name, model, manufacturer, color and drying
(3) The main technical parameters of the selected injection machine, such as the relevant dimensions between the injection machine and the installation mold, screw type, power (4) the pressure and stroke of the injection machine
(5) Injection molding conditions such as temperature, pressure, speed, mold locking force, etc
3. Structural design steps of injection mold
(1) Determine the number of cavities. Conditions: maximum injection volume, mold locking force, product accuracy requirements, economy
(2) Select the runoff surface. The principle should be that the mold structure is simple, the parting is easy and does not affect the appearance and use of plastic parts
(3) Determine the cavity layout plan. Use balanced arrangement as far as possible
(4) Determine the gating system. Including main flow channel, diversion channel, gate, cold hole, etc.
(5) Determine the release mode. Different demoulding methods are designed according to different parts of the mold left by the plastic parts.
(6) Determine the structure of the temperature regulating system. The temperature regulating system is mainly determined by the type of plastic.
(7) When the insert structure is adopted for the female die or core, the machinability and installation and fixation mode of the insert are determined.
(8) Determine the exhaust type. Generally, the clearance between the parting surface of the mold and the ejection mechanism and the mold can be used for exhaust. For large and high-speed injection mold, the corresponding exhaust form must be designed.
(9) Determine the main dimensions of the injection mold. According to the corresponding formula, calculate the working size of the molding part and determine the thickness of the side wall of the mold cavity, the cavity bottom plate, the core backing plate, the thickness of the moving template, the cavity plate thickness of the modular cavity and the closing height of the injection mold.
(10) Select standard mold base. Select the standard mold base of the injection mold according to the main dimensions of the injection mold designed and calculated, and try to select the standard mold parts.
(11) Sketch the structure of the mold. Drawing the complete structure sketch of injection mold and drawing the mold structure drawing 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, mold locking force, and the size of the installation part of the mold, mold opening stroke and ejection mechanism.
(13) Review of structural design of injection mold. Conduct preliminary review and obtain the user’s consent, and it is necessary to confirm and modify the user’s requirements.
(14) Draw the assembly drawing of the mold. Clearly indicate the assembly relationship of each part of the injection mold, necessary dimensions, serial numbers, details Title block and technical requirements (the contents of technical requirements are as follows: a. performance requirements for die structure, such as assembly requirements for ejection mechanism and core-pulling mechanism; b. requirements for die assembly process, such as fitting clearance of parting surface, parallelism of upper and lower parts of die; c. requirements for die use; d. requirements for anti-oxidation treatment, die number, lettering, oil seal and storage; e. requirements for die test and inspection. (15) Draw mold part drawing. The order of disassembling and drawing the part drawing from the mold assembly drawing or the part drawing is: first inside then outside, first complex then simple, first forming parts then structural parts.
(16) Review the design drawings. The final review of the injection mold design is the final check of the injection mold design, and more attention should be paid to the processing performance of the parts.
3. Audit of injection mold
1. Basic structure
(1) Whether the mechanism and base parameters of the injection mold match the injection machine.
(2) Whether the injection mold has a clamping guide mechanism and whether the mechanism design is reasonable.
(3) Whether the selection of parting surface is reasonable, whether there is the possibility of flash, and whether the plastic part stays on the side of the moving die (or fixed die) set in the ejection and release mechanism.
(4) Whether the layout of the cavity and the design of the gating system are reasonable. Whether the gate is compatible with the plastic raw material, whether the gate position is equivalent, whether the geometric shape and size of the gate and runner are appropriate, and whether the flow ratio is reasonable.
(5) Whether the design of formed parts is reasonable.
(6) Ejection release mechanism and lateral male. Or whether the core-pulling mechanism is reasonable, safe and reliable. Whether there is interference and occlusion. (7) Whether there is an exhaust mechanism and whether its form is reasonable. (8) Whether temperature regulation system is required. Whether the heat source and cooling mode are reasonable.
(9) Whether the structure of supporting parts is reasonable.
(10) Whether the overall dimension 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 screw hole position on the injection mechanism and fixed mold fixing plate.
2. Design drawings
(1) Assembly drawing
Whether the assembly relationship of parts and components is clear, whether the matching code is properly and reasonably marked, whether the marking of parts is complete, whether it corresponds to the serial number in the list, whether the relevant instructions have clear marks, and how standardized the whole injection mold is.
(2) Parts drawing
Whether the part number, name and processing quantity are clearly marked, whether the dimensional tolerance and various tolerance marks are reasonable and complete, whether the parts easy to wear are reserved for grinding, which parts have ultra-high accuracy requirements, whether this requirement is reasonable, whether the material cushion of each part is appropriate, and whether the heat treatment requirements and surface roughness requirements are reasonable.
(3) Cartographic method
Whether the drawing method is correct, whether it conforms to national standards, and whether the geometric figures and technical requirements expressed on 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 plastic raw materials have been correctly considered, the possible impact of the type of injection machine on the molding quality, and whether the corresponding preventive measures have been taken for the possible problems during the molding process during the design of the injection mold.
(2) Whether the requirements of plastic parts on the guiding accuracy of injection mold have been considered, and whether the guiding structure has been designed reasonably.
(3) Whether the working dimension calculation of formed parts is correct, whether the accuracy of products can be guaranteed, and whether they have sufficient strength and rigidity.
(4) Whether the supporting parts can ensure that the mold has sufficient overall strength and rigidity.
(5) Whether mold test and repair requirements are considered
4. Whether there are grooves, holes, etc. convenient for assembly and disassembly in terms of assembly and disassembly and handling conditions, and whether they are marked.
Post time: Mar-06-2023
