The following is the detailed production process of plastic injection helmet, covering all aspects from raw materials to finished products, combined with the characteristics of the injection process and the functional requirements of the safety helmet:
I. Overview of the production process
Phases - critical steps
1. Material selection and pretreatment - Select the type of plastic (ABS, HDPE, PC, etc.) <br>- Raw material drying (remove moisture, such as ABS drying at 80℃ for 2-4 hours)
2. Mold design and manufacturing -- mold parting design (suitable for safety hat curved structure) <br>- Hot runner system (reduce waste, improve efficiency)
3. Injection molding -- injection molding parameter setting (temperature, pressure, cooling time) <br>- multi-color injection molding (warning stripe or logo integrated molding)
4. Post-treatment and assembly - trim gate and raw edge <br>- Install lining, adjusting belt, vent fittings
5. Quality testing and certification --- Impact test, puncture test, flame retardant test<br>- Comply with international standards such as ANSI Z89.1, EN 397, etc.
Second, step-by-step process details
1. Material Selection and Pre-treatment
Material type:
- ABS: Balance strength and toughness, suitable for general-purpose helmets.
- HDPE: Lightweight, chemical resistant, used for low cost requirements.
- PC (Polycarbonate): high impact resistance, suitable for high risk environments (e.g. power industry).
- Pre-treatment:
- Plastic pellets need to be dehydrated in a drying oven (e.g. ABS humidity needs to be <0.1%) to avoid bubbles or silvering during injection moulding.
2. Mould design and manufacturing
Mould structure:
- Parting surface design: adapt to the hemispherical or V-shaped contour of the helmet to avoid the closing line affecting the appearance.
- Ejector system: Adopt multi-point ejector or pneumatic ejector to prevent deformation during demoulding.
- Air venting groove: Micro air venting groove is set at the edge of the mould to avoid trapped air leading to lack of material.
- Hot runner technology:
- Reduce the generation of cold material and improve the injection efficiency, suitable for multi-cavity moulds (e.g. 4-8 helmets in one go).
3. Injection moulding process
Parameter setting:
Temperature: barrel temperature (e.g. ABS: 200-240°C), mould temperature (40-80°C).
Pressure: injection pressure (80-120MPa), holding pressure (60-80MPa) to ensure that the cap body is dense.
Cooling time: adjusted according to wall thickness (usually 20-40 seconds) to avoid shrinkage and deformation.
Multi-colour injection moulding:
Warning colour stripes (e.g. fluorescent yellow stripes) are moulded in one go by two-colour injection moulding machine, no need for post-painting.
4. Post-treatment and assembly
Surface treatment:
Electrostatic flocking lining (enhance wearing comfort).
UV spraying or labelling (to increase brand identity and reflective effect).
Accessories assembly:
Mounting adjustment strap, chin rest, breathable mesh cover (partly fixed by ultrasonic welding).
5. Quality testing and certification
- Physical performance test:
- Impact test: 5kg steel ball from 1m height free fall impact on the top of the cap, no rupture.
- Penetration test: 3kg conical drop body vertical impact, the cap body shall not be penetrated.
- Environmental adaptability test:
- High temperature (50℃), low temperature (-20℃) environment test deformation and strength.
- Flame retardant test (self-extinguishing time ≤ 5 seconds after contact with open flame).
Key Technical Difficulties and Solutions
| Problems | Causes | Solutions
| Deformation of brim | Uneven cooling or premature ejection | Optimise cooling water circuit of mould, extend holding time |
| | Surface shrinkage marks | Uneven wall thickness or insufficient injection pressure | Increase the injection pressure, adjust the wall thickness transition design
| Poor liner fit | Inadequate curing of flocking glue | Increase temperature of flocking process (80-100°C) or change to hot melt glue |
Production optimisation
1. Automation upgrade:
- Robot automatic pickup + visual inspection, reduce human intervention.
2. Lightweight design:
- Adopt micro-foam injection moulding work
6. Application Scenarios and Standards
- Construction industry: EN 397 standard (Europe) is required.
- Power industry: Class E electrical insulation certification (withstanding 20kV voltage) is required.
- Mining industry: add built-in headlamp bracket and dustproof design.
Through the above process, injection moulded helmets can be efficiently produced in compliance with safety standards to meet the protection needs of different industries. In actual production, the process parameters need to be adjusted according to the specific material and mould characteristics, and product consistency is ensured through continuous testing.
