Lid Injection Molding Process for Stainless Steel Insulated Bottles
After the bottle body is finished, you enter our lid injection molding workshop — the stage where precision molds, food-grade materials, and automated equipment come together to create a leak-proof, durable lid. For buyers, the lid quality directly affects user experience, so this part of production is just as critical as the bottle itself.
Mold Installation and Machine Setup
The process begins with the mold.
Workers mount the custom lid mold onto the injection molding machine and fine-tune the operating parameters — including temperature, pressure, injection speed, and cooling time.
Correct setup ensures:
Stable dimensions
Clean parting lines
Consistent mass-production results
Preparing Food-Grade PP Material
Your lid is made from PP (polypropylene) — a widely used, food-safe plastic ideal for drinkware.
PP is selected because it is:
Non-toxic and BPA-free
Heat-resistant
Corrosion-resistant
Lightweight and easy to mold
Excellent for sealing designs
Workers pour snow-white PP pellets into the mixer, then add color powder according to the Pantone shade you specify. After thorough mixing, the pellets take on the exact color required for your brand.
High-Temperature Injection Molding
Once the material is ready, it enters the injection unit:
PP pellets are heated until molten
The melted plastic is injected into the mold cavity under high pressure
The mold cools and holds the shape during the pressure-holding phase
When the cooling cycle ends, the mold automatically opens.
High-Temperature Injection Molding
Once the material is ready, it enters the injection unit:
PP pellets are heated until molten
The melted plastic is injected into the mold cavity under high pressure
The mold cools and holds the shape during the pressure-holding phase
When the cooling cycle ends, the mold automatically opens
Robotic Arm Extraction
A robotic arm removes each newly-formed lid from the mold with steady precision and places it neatly onto the conveyor line.
Immediately after removal, the mold closes again and begins the next injection cycle.
This smooth, repetitive rhythm is what allows us to maintain high output and uniform quality.
Silicone Seal Assembly
To achieve a leak-proof structure, workers manually install the food-grade silicone ring onto each lid.
This step ensures:
Tight sealing
No dripping
Compatibility with both hot and cold beverages
Final QC Check for Lid Components
Before lids move to the packaging area, our QC team checks:
Fit and flexibility of silicone seals
Smoothness of mold surfaces
Dimensional accuracy
Color consistency with the approved Pantone code
Only qualified lids proceed to final assembly with the bottle body.
Follow each step to see how we produce stainless steel insulated bottles from raw materials to finished products.
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