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What is the injection molding process
The following is the core process of injection molds from design to production, analyzed step by step:
1.Project initiation and requirement analysis
-Clearly define product usage, performance requirements (such as strength, precision, appearance), materials (plastic types, such as ABS, PC, nylon, etc.), production volume (batch production/small batch), and special requirements (such as demolding angle, surface treatment).
-Confirm product drawings (3D models/2D drawings), annotate technical parameters such as dimensional tolerances and surface roughness.
2.Product Design and Optimization
（1）Product modeling
-Design 3D models using CAD software (such as UG, Pro/E, SolidWorks) to ensure a reasonable structure (such as uniform wall thickness, reinforcement layout, and demolding slope ≥ 1 °).
Mold design (core stage)
Generally speaking in plastic molding since always injection molds for plastic mold Making
Determine the injection mold scheme
-Design of parting surface: Select the parting surface with the least impact on the product appearance and the most convenient for demolding (such as flat, inclined, curved).
-Number of cavities: Single or multiple cavities (such as 1 mold with 2 cavities, 1 mold with 8 cavities) are determined based on production volume.
-Structural design: including pouring system (main channel, diversion channel, gate type, such as hidden and point gate), cooling system (waterway layout to ensure uniform heat dissipation), ejector system (ejector pin, push plate, air ejector), exhaust system (to avoid trapped gas causing burning
（2）Manufacturability Analysis (DFM)
-Check whether the product has structures that are difficult to achieve with molds, such as inverted buckles, thin walls, and sharp angles. Communicate with customers to modify the plan and reduce mold difficulty and cost.
3.Injection Mold design (core stage)
(1) Generally speaking in plastic molding since always injection molds for plastic mold Making
Determine the injection mold scheme
-Design of parting surface: Select the parting surface with the least impact on the product appearance and the most convenient for demolding (such as flat, inclined, curved).
-Number of cavities: Single or multiple cavities (such as 1 mold with 2 cavities, 1 mold with 8 cavities) are determined based on production volume.
-Structural design: including pouring system (main channel, diversion channel, gate type, such as hidden and point gate), cooling system (waterway layout to ensure uniform heat dissipation), ejector system (ejector pin, push plate, air ejector), exhaust system (to avoid trapped gas causing burning
(2) CAE injection mold flow plastic analysis (optional)
-Simulate the plastic injection molding process using software such as Moldflow to predict issues such as filling, cooling, and warping, optimize gate positions and cooling water channels, and reduce the number of mold trials.
(3) Drawing output
-Draw the mold assembly drawing and part drawing (core, cavity, slider, hot runner, etc.), mark the fitting tolerance (such as H7/g6) and technical requirements (such as heat treatment hardness HRC45-50).
4.Selection of mold materials
(1) Select materials according to product requirements
-Ordinary plastics (such as ABS, PP): commonly used P20, 718 pre hardened steel (hardness 28-35HRC), with moderate cost.
-Engineering molding plastics (such as PC, nylon): choose high hardness steel (such as S136, H13, hardness 45-55HRC), wear-resistant and corrosion-resistant.
-Transparent products: require high mirror polished steel (such as S136) to avoid surface defects.
(2) Material handling
-Heat treatment (to increase hardness), surface treatment (such as chrome plating, TD coating, to enhance wear resistance).
5. Injection Mold processing and manufacturing
(1) Rough processing
-Steel cutting is processed into mold blanks through sawing and milling machines, with reserved processing allowance.
(2) Precision machining
-CNC machining center: Processing the main structure of the core and cavity, with an accuracy of ± 0.01mm.
-Electric discharge machining (EDM): Processing complex surfaces (such as flower patterns and inverted buckles) with an accuracy of
± 0.005mm.
-Wire cutting (WEDM): cutting inserts, sliders and other parts, suitable for high-precision thin-walled structures.
-Grinding: Surface grinding machine processes template surfaces, while forming grinding machine processes precision components such as guide columns and guide sleeves.
(3) Auxiliary processing
-Drilling (waterway, top needle hole), tapping, polishing (mirror polishing Ra ≤ 0.01 μ m, used for transparent parts).
6. Mold assembly and debugging
(1) Component assembly
-Assemble the Mold core/cavity, slider mechanism, ejector system, cooling/hot runner system according to the drawings, and check the fitting accuracy of each component (such as guide column and guide sleeve clearance ≤ 0.02mm).
(2) Functional testing after Mold manufacturing
-Manually adjust the ejection and slider core pulling actions to ensure smooth and unobstructed movement without any jamming; Connect the injection molding machine to test the hydraulic/pneumatic system (such as hot runner temperature control).
7. Trial molding and optimization
(1) First trial injection mold for plastic
-Install the mold onto the injection molding machine, set the process parameters (temperature, pressure, cooling time), and produce the first sample.
(2) Defect analysis and modification
-Common problems:
-Insufficient filling: Increase injection pressure and check gate size.
-Flying edge: Adjust the clamping force and correct the wear of the parting surface.
-Shrinkage/Bubbles: Optimize cooling water channels and increase wall thickness.
-Deformation/warping: improve gate position, adjust mold temperature.
-Based on the trial mold results, perform secondary processing on the mold (such as grinding the sprue and correcting the core) until the sample is qualified.rue.
8.Inspection and delivery
(1) Mold inspection after plastic molding done
-Dimensional inspection: Use a coordinate measuring machine (CMM) to measure the dimensions of the core/cavity to ensure compliance with the drawing tolerances.
-Performance testing: Conduct 50-100 consecutive mold tests to verify mold stability (such as needle life and slider wear).
(2) Delivery documents
-Provide injection mold drawings, trial mold reports, maintenance manuals, cooperate with customer trial production acceptance, and complete delivery.
9. Mold maintenance and upkeep (long-term use)
(1) Daily maintenance
-Clean the mold cavity (alcohol/soft cloth) after production and apply rust inhibitor; Check the lubrication condition of the top pin and guide post.
(2) Regular maintenance
-Disassemble and inspect worn parts (such as sprue sleeves and ejector pins) and replace vulnerable parts every 50000-100000 production cycles; Re polish the surface of the cavity to ensure accuracy.
10.Summary of key points:
-Balance between accuracy and efficiency: Complex structures require electrical discharge machining, and multi cavity mold design is prioritized for mass production.
-The importance of trial molding: About 80% of mold problems need to be discovered through trial molding, and multiple adjustments are the norm.
-Digital tools: CAE analysis and CNC machining technology improve the efficiency of mold design and manufacturing, and shorten the cycle.
Through the above mold manufacturing process, it is possible to achieve full process control from product design to mold delivery, ensuring that injection molds meet production needs.
