Key Process Parameters for PLA Plastic Injection Molding

PLA plastic injection molding is an environmentally friendly injection molding process using bio-based biodegradable polylactic acid (PLA) as raw material. Its core advantages are low carbon footprint, high molding precision, and compatibility with most conventional injection molding equipment. Key process parameters include:

1. Raw Material Pretreatment

Strict drying is essential before production. Conventional PLA drying temperature is 75-85℃ for 4-6 hours, controlling the raw material moisture content below 0.025% to prevent hydrolysis during melting, which can cause bubbles and silver streaks.

For PLA/PBAT blends, a mid-range parameter of 65-75℃ for 5-7 hours can be used to balance moisture removal and prevention of PBAT aging.

2. Temperature Control System

The barrel uses a gradient cooling system: 170-180℃ at the rear, 165-175℃ in the middle, and 160-170℃ at the front. The nozzle temperature is controlled below 170℃ to prevent PLA from overheating and degrading.

Mold temperatures are differentiated according to crystallization type: amorphous PLA uses a cold mold at 40-50℃, semi-crystalline PLA uses a medium-temperature mold at 40-60℃, and crystalline PLA uses a hot mold to improve crystallinity, ensuring product hardness and shaping effect.

3. Pressure and Speed Control

Injection employs multi-stage control: low-speed flow through the runner, uniform speed filling the cavity, and final deceleration and pressure stabilization to reduce air entrapment and localized overheating.

Holding pressure is set at 50%-60% of the injection pressure, slightly lower than that for general plastics, to avoid excessive internal stress leading to warping and cracking after demolding.

Screw speed is controlled at 50-80 rpm, and back pressure is adjusted to 5-10 bar to ensure uniform plasticization while reducing the risk of shear thermal degradation.

4. Post-Demolding Treatment

Newly demolded products must be left to stand at room temperature for at least 24 hours to release internal stress before subsequent processes such as trimming and assembly, reducing the probability of stress cracking later.

After screening and drying, scrap materials can be mixed in small quantities for reuse. The reuse ratio must be strictly controlled to avoid a significant decrease in mechanical properties due to repeated regeneration.

Qingdao Xueyu Molding Products Co., Ltd. is mainly engaged in the design and manufacturing of injection molds, injection molding and secondary processing (spraying, pad printing, ultrasonic welding, stamping), etc. For more information about pla plastic injection molding, please contact us.

Website: www.xyzmould.com

Address: No.18 Henan Head Road, Henan Head Community, Jihongtan Street, Qingdao Industrial Park, Shandong Province, China

Email: wangmiaotian8@163.com