Stretch molding is a key process encompassing deep stretching of plastic parts and sheet metal. Temperature, as a core parameter determining molding quality, directly impacts the product's appearance, dimensional accuracy, mechanical properties, and production efficiency through its control precision and adjustment strategies. Temperature control schemes for different molding needs must be specifically designed to adapt to diverse molding scenarios.
Temperature adaptation based on material thermal properties is fundamental. The significant differences in heat distortion characteristics among different materials determine the baseline temperature range for
Display Micro Screws: In thermoplastics, deep stretching of amorphous polycarbonate (PC) requires temperature control between 80-120℃. This range ensures sufficient melt flow to fill complex cavities while avoiding excessively high temperatures that prolong the cooling cycle. Deep stretching of crystalline polyethylene (PE) uses a temperature range of 30-60℃; lower temperatures allow for controlled crystallinity, reducing uneven shrinkage after molding. In the field of sheet metal deep drawing, aluminum alloy automotive body panels require maintaining a temperature of 200-300℃ to reduce deformation resistance and suppress deep drawing cracks. For ordinary low-carbon steel, the deep drawing temperature is typically room temperature to 50℃; excessively high temperatures can exacerbate mold wear.
Dynamic temperature control at different process stages is crucial for forming quality. Deep drawing consists of three stages: pre-stretching, main stretching, and holding/cooling. Temperature needs to be dynamically adjusted with each stage: In the pre-stretching stage, the temperature is slightly higher than the material's glass transition temperature (Tg) to place the material in a transitional state between elasticity and plasticity, facilitating pre-deformation. The main stretching stage is the core of the forming process; the temperature needs to be increased to promote uniform deformation and avoid localized stress concentration. For example, when stretching optically transparent parts, the temperature fluctuation in the main stretching cavity needs to be controlled within ±1℃ to prevent excessive haze or dark lines. In the holding/cooling stage, a gradient cooling method is required, reducing the temperature from the forming temperature to the material's demolding temperature. Temperature uniformity in this stage directly affects dimensional stability; the cooling rate fluctuation for precision metal drawn parts needs to be controlled within 5℃/min to avoid warping.
Performance-oriented temperature control strategies must precisely match the requirements. For high-gloss surface products, such as plastic stretch parts for mobile phone frames, zoned temperature control is necessary: heating circuits are set up for areas with lower temperatures at the cavity edges to prevent shrinkage caused by excessively rapid edge cooling; cooling circuits are set up for the central area to shorten the cycle time, while the electric arc temperature is close to the material's Tg to ensure the melt replicates the mold texture effectively and improves surface gloss. For high-mechanical-performance structural parts, such as stretch parts for appliance casings, the electric arc temperature needs to be increased to promote material crystallization. When the electric arc temperature of polypropylene (PP) based structural parts is increased to 70-90℃, the tensile strength can be increased by approximately 12%. For low-stress transparent products, such as food packaging containers, a slow cooling process is required, with the electric arc temperature decreasing from the stretching temperature to the demolding temperature at a rate of 2℃/min to reduce residual internal stress and lower the risk of later cracking.
Currently, mature temperature control systems mostly employ mold temperature equipment with water circulation (suitable for low-temperature scenarios below 150℃) and oil circulation (suitable for medium-high temperature scenarios between 150-350℃). These systems combine real-time temperature monitoring with PID algorithm control to achieve dynamic temperature balance at various points in the cavity, adapting to temperature variations required for different molding processes. In summary, temperature control for Display
Micro Screws needs to be integrated throughout the entire chain, from material selection and process design to product performance. Through targeted temperature settings, dynamic control, and zone optimization, molding defect rates can be effectively reduced, and overall product performance improved. This is the core guarantee for the efficient and stable operation of the stretching process.
