Research on Custom Milk Tea Cup Lid Plastic Mold

Abstract

1. Structural analysis and molding process evaluation of milk tea cup lid plastic parts

2. Performance analysis and molding characteristics research of PP plastic materials

3. Overall structural design and key component design of injection molds

4. Mold material selection and heat treatment process research

5. Optimal design and experimental verification of injection molding process parameters

• Injection pressure: 70-80MPa

• Injection speed: 30-50mm/s

• Holding pressure: 60-70% of injection pressure

• Holding time: 5-10 seconds

• Fixed mold base plate: 320mm×350mm×25mm

• Fixed template: 270mm×350mm×60mm

• Moving mold base plate: 320mm×350mm×25mm

• Moving template: 250mm×350mm×70mm

• Ejector pin fixing plate: 160mm×350mm×20mm

• Ejector plate: 160mm×350mm×15mm

• The cavity adopts an integral structure, and the material is 718H pre-hardened mold steel

• The cavity dimensions are calculated based on the plastic part dimensions and shrinkage rate, with the shrinkage rate taken as 1.5%

• The cavity surface roughness requirement is Ra≤0.4μm, requiring polishing treatment

• The core adopts a combined structure, facilitating processing and maintenance

• The core material is 718H pre-hardened mold steel, with a hardness of 36-38HRC

• The core surface needs to be mirror-polished, with a roughness of Ra≤0.2μm

• For complex-shaped molding parts, an insert structure is adopted

• The insert material is Cr12MoV mold steel, with a hardness of 58-62HRC after quenching treatment

• The fitting clearance between the insert and the template is 0.01-0.02mm

• Sprue diameter: 4-5mm

• Sprue taper: 2-3°

• Sprue length: Determined based on the template thickness, generally 80-100mm

• Sprue bushing material: T10A steel, with a hardness of 50-55HRC after quenching treatment

• Runner cross-sectional shape: Trapezoidal or semi-circular

• Runner diameter: 6-8mm

• Runner length: Minimized to reduce material waste

• Runner surface roughness: Ra≤1.6μm

• Gate type: Side gate

• Gate dimensions: Width 2-3mm, depth 0.8-1.0mm, length 1-2mm

• Gate position: Selected on the non-appearance surface of the plastic part edge

• Number of gates: One gate per cavity

• Water channel diameter: 8-10mm

• Water channel spacing: 30-40mm

• Water channel layout: Spiral or parallel layout is adopted to ensure uniform cooling

• Water inlets and outlets: Set on the mold side for easy connection

• Cooling time: Calculated based on the plastic part thickness and material thermal properties, generally 15-25 seconds

• Cooling water volume: Calculated based on the mold heat load, generally 5-10L/min

• Mold temperature control: The mold temperature is precisely controlled by a temperature controller, with an error of ±2℃

• Number of push rods: 8-12 pieces

• Push rod diameter: 3-5mm

• Push rod material: T8A steel, with a hardness of 50-55HRC after quenching treatment

• Fitting clearance between push rod and template: 0.02-0.03mm

• Ejector plate thickness: 15-20mm

• Ejector plate material: 45 steel, with a hardness of 230-270HB after quenching and tempering treatment

• Fitting between ejector plate and template: Guide pillar guidance is adopted to ensure smooth movement

• Ejection force: Calculated based on the contact area between the plastic part and the mold and the friction coefficient

• Safety factor: 1.5-2.0 is taken to ensure reliable ejection

• Chemical composition: C 0.35-0.42%, Cr 1.8-2.1%, Ni 0.8-1.2%, Mo 0.15-0.40%

• Mechanical properties: Hardness 36-38HRC, tensile strength 1000-1200MPa, impact toughness ≥20J/cm²

• Performance characteristics: Good polishing performance, cutting performance, and dimensional stability

• Chemical composition: C 1.45-1.70%, Cr 11.00-13.00%, Mo 0.40-0.60%, V 0.15-0.30%

• Mechanical properties: Hardness 58-62HRC after quenching, good wear resistance, high hardenability

• Performance characteristics: Suitable for making molding parts requiring high wear resistance

• Guide pillar material: 20 steel, surface carburizing and quenching treatment

• Guide bushing material: T10A steel, quenching treatment

• Fitting clearance: 0.01-0.02mm

• Mechanical properties: Hardness 50-55HRC after quenching

• Performance characteristics: Good strength and toughness

• Pre-hardening treatment: The supplier has completed pre-hardening treatment, with a hardness of 36-38HRC

• Post-processing treatment: If further hardness improvement is needed, nitriding treatment can be performed

• Nitriding process: 520-540℃, holding for 20-30 hours, nitriding layer depth 0.15-0.25mm

• Annealing treatment: 830-860℃, holding for 2-4 hours, slow cooling to 500℃ followed by air cooling

• Quenching treatment: 950-1050℃, holding for 0.5-1 hour, oil cooling

• Tempering treatment: 180-200℃, holding for 2-3 hours, air cooling, hardness 58-62HRC

• Quenching treatment: 780-800℃, holding for 0.5 hours, water quenching

• Tempering treatment: 180-200℃, holding for 1-2 hours, air cooling, hardness 50-55HRC

• Barrel temperature: Front section 180-200℃, middle section 165-180℃, rear section 150-170℃

• Nozzle temperature: 170-180℃

• Mold temperature: 50-80℃, precisely controlled by an oil temperature machine

• Injection pressure: 70-80MPa

• Holding pressure: 40-50MPa

• Clamping force: Calculated based on the projected area of the plastic part, generally 80-100MPa

• Injection time: 2-5 seconds

• Holding time: 5-10 seconds

• Cooling time: 15-25 seconds

• Total cycle: 25-40 seconds

• Causes: Insufficient holding pressure, uneven cooling, uneven wall thickness

• Solutions: Increase holding pressure and time, optimize cooling system, adjust plastic part structure

• Causes: Uneven shrinkage, improper cooling, mold temperature difference

• Solutions: Optimize gating system, adjust cooling method, control mold temperature

• Causes: Low temperature at melt confluence, insufficient pressure, poor venting

• Solutions: Increase barrel temperature, increase injection pressure, optimize venting system

• Causes: Insufficient material drying, too fast injection speed, poor mold venting

• Solutions: Strengthen material drying, adjust injection speed, optimize venting system

• Rough machining: Rough machining using CNC milling machines or machining centers

• Semi-finishing: Leave 0.5-1.0mm machining allowance

• Finishing: Finishing using high-speed machining centers, surface roughness Ra≤0.8μm

• Polishing treatment: Manual polishing or mechanical polishing, final roughness Ra≤0.2μm

• Plane processing: Grinding using surface grinders, flatness ≤0.02mm

• Hole processing: Hole processing using coordinate boring machines or machining centers, position accuracy ≤0.01mm

• Surface treatment: Deburring, chamfering, surface roughness Ra≤1.6μm

• Wire cutting processing: For inserts with complex shapes, use slow wire EDM processing

• EDM processing: For parts difficult to cut, use EDM processing

• Polishing treatment: Ensure molding surface roughness Ra≤0.4μm

• Part cleaning: All parts must be cleaned before assembly to remove oil and impurities

• Part inspection: Check the dimensional accuracy and surface quality of parts to ensure they meet design requirements

• Tool preparation: Prepare required assembly tools and measuring tools

1. Fixed mold part assembly: Fixed mold base plate → fixed template → cavity → gating system parts

2. Moving mold part assembly: Moving mold base plate → moving template → core → ejection mechanism

3. Guide pillar and bushing assembly: Press guide pillars into moving template, press guide bushings into fixed template

4. Mold closing adjustment: Adjust gaps in each part to ensure smooth movement

• Parting surface fitting gap: ≤0.02mm

• Guide pillar and bushing fitting gap: 0.01-0.02mm

• Core and cavity fitting gap: Determined according to plastic part requirements, generally 0.03-0.05mm

• Ejection mechanism movement accuracy: ≤0.05mm

• Injection molding machine preparation: Check the working status of the injection molding machine to ensure normal operation

• Mold installation: Install the mold on the injection molding machine, adjust clamping force and injection parameters

• Material preparation: Prepare dried PP plastic raw materials

1. First mold test: Conduct mold test using initially determined process parameters

2. Plastic part inspection: Measure dimensions and check appearance of mold-tested plastic parts

3. Problem analysis: Analyze problems and defects occurring during mold testing

4. Mold adjustment: Make necessary adjustments to the mold based on mold testing results

• Dimension adjustment: Control plastic part dimensions through mold repair or process parameter adjustment

• Appearance adjustment: Optimize gating system, adjust process parameters to improve appearance quality

• Process optimization: Optimize injection molding process parameters based on mold testing results

• Cavity dimension accuracy: IT7-IT8 grade

• Core dimension accuracy: IT7-IT8 grade

• Template parallelism: ≤0.02mm

• Guide pillar and bushing coaxiality: ≤0.01mm

• Molding surface roughness: Ra≤0.4μm

• Non-molding surface roughness: Ra≤1.6μm

• Surface defects: No scratches, bumps, rust or other defects allowed

• Ejection mechanism movement: Smooth, no jamming

• Guide pillar and bushing movement: Flexible, no abnormal noise

• Mold closing gap: Uniform, no leakage

• Clean the mold surface and parting surface after each shift

• Check the wear of guide pillars, bushings, and other moving parts

• Lubricate moving parts, add lubricating oil or grease

• Disassemble and clean the mold every 10,000-20,000 cycles

• Check the wear of molding parts and replace severely worn parts

• Re-polish the molding surface to maintain surface quality

• Establish a mold maintenance record system

• Formulate a reasonable maintenance plan based on production conditions

• Train operators on correct mold use and maintenance methods

• Material performance: Hardness, wear resistance, toughness of mold steel

• Processing quality: Processing accuracy and surface quality of parts

• Usage conditions: Injection molding process parameters, production batch, maintenance

• Plastic part characteristics: Material hardness, filler content, molding temperature

• Empirical evaluation: Evaluate based on usage experience of similar molds

• Experimental evaluation: Evaluate through accelerated life testing

• Theoretical calculation: Calculate based on material wear theory

• Cavity and core: 500,000-1,000,000 cycles

• Molding inserts: 300,000-500,000 cycles

• Guide pillars and bushings: 1,000,000-2,000,000 cycles

• Push rods: 500,000-1,000,000 cycles

1. As a typical thin-walled plastic part, the mold design of milk tea cup lids needs to fully consider the molding characteristics of materials and the structural characteristics of plastic parts, and adopt reasonable mold structures and process parameters.

2. Adopting technical schemes such as a two-cavity mold structure, CI-2735-A60-B70-C80 type standard mold base, and 718H pre-hardened mold steel can effectively meet the production requirements of milk tea cup lids, achieving the goals of high product precision, short molding cycle, and long mold life.

3. The injection molding process parameters of PP plastic have a significant impact on product quality. The process parameter combination optimized through orthogonal experiments can effectively improve product quality and production efficiency.

4. The manufacturing accuracy and assembly quality of the mold directly affect product quality and mold life. Establishing a complete quality control system and maintenance system is the key to ensuring the long-term stable operation of the mold.

1. Aiming at the structural characteristics of milk tea cup lids, an optimized gating system and cooling system were designed, effectively solving the problems of uneven flow and uneven cooling during the molding process of thin-walled plastic parts.

2. Using 718H pre-hardened mold steel as the cavity and core material, combined with a reasonable heat treatment process, achieved a balance between high hardness, high wear resistance, and good processing performance of the mold.

3. Established a process parameter optimization method based on orthogonal experiments, providing a reference for the injection molding process optimization of similar thin-walled plastic parts.

1. In the milk tea packaging industry: It can provide technical references for the mold design of milk tea cup lids and similar food packaging containers, improving product quality and production efficiency.

2. In the injection mold industry: It can provide technical references for the design and manufacturing of thin-walled plastic part molds, promoting technological progress in the industry.

3. In the material processing industry: It can provide practical experience for the molding process optimization of PP plastic and similar materials, improving the molding performance of materials.

1. Adopt CAE technology for mold design and molding process simulation to further optimize mold structures and process parameters.

2. Research new mold materials and surface treatment technologies to improve mold service life and molding quality.

3. Develop intelligent mold design systems to achieve automation and intelligence in mold design.

4. Research green molding technologies to reduce energy consumption and environmental pollution, achieving sustainable development.

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