How To Blow Long Bottle, wall thickness control in the Extrusion Blow Molding (EBM) process is essential to ensure the quality and consistency of the final product. This control involves several techniques and parameters to manage and adjust the thickness of the walls of the molded part, which directly affects the product’s performance, material efficiency, and overall quality.

These products are small cans used to hold baby rice puffs. The cans are made from high-density polyethylene (HDPE) using blow molding, paired with polypropylene (PP) screw caps. The can height is 200mm, with a maximum diameter of 78mm, and a design weight of 41 grams. Wall thickness control is crucial for this process, as uniform wall thickness affects the can’s stability, sealing, and material efficiency. Here are the key points for wall thickness control in this process:

Die Head Design:

• Mold Design: Precise mold design ensures even flow and distribution of molten plastic. For these 200mm high, 78mm diameter cans, the mold needs well-designed flow channels and orifices for uniform wall thickness.
• Adjustable Die Head: Use an adjustable die head to dynamically control parison wall thickness during production. This will ensure also uniformity at different parts of the can, like the top and bottom.

Parison Uniformity Control:

• Extrusion Speed: Control the extruder screw speed and haul-off rate to maintain consistent wall thickness along the parison length. For the 41-gram can, precise material flow control is essential.
• Parison Temperature: Keep the molten plastic at the right temperature by controlling the extruder and mold heating and cooling systems. This helps to prevent thickness variations due to temperature changes.
• Length Challenges: The 200mm length imposes significant difficulties in controlling uniform parison thickness. Extruding such a long parison takes comparatively longer, during which gravity and weight pull the parison down. This effect causes the upper part of the parison to become thinner while the lower end becomes thicker.

Blow Molding Process Parameters:

• Blow Ratio: Manage blow air pressure and mold closing speed to ensure even inflation of the parison. This helps a lot in achieving the desired 200mm height and 78mm diameter. Proper blow ratio ensures uniform wall thickness.
• Mold Cooling: Precise cooling control of the mold affects wall thickness distribution. For the 41-gram can, accurate cooling prevents thickness irregularities.

Wall Thickness Detection and Feedback System:

• Online Detection: Modern extrusion blow molding equipment includes online wall thickness detection systems. These systems monitor parison thickness in real time and provide feedback to the control system, ensuring consistent can wall thickness during production.
• Feedback Control: Adjust extrusion and blow molding parameters based on detection data to maintain wall thickness consistency through a closed-loop control system.

Wall thickness control in the extrusion blow molding process involves mold design, extrusion process control, blow molding parameters, and real-time detection feedback. The 200mm length of the can poses additional challenges, as gravity and the weight of the molten plastic can cause uneven thickness. By precisely controlling these factors, manufacturers can produce HDPE blow-molded cans with uniform wall thickness, meeting the design weight of 41 grams, height of 200mm, and diameter of 78mm, ensuring performance and stability in use.

VolksMolds is a leading plastic injection mold manufacturer known for its expertise, experience, and proven history. Moreover, the company excels in producing high-precision molds for various sectors, including packaging, store displays, and homewares. With a commitment to quality and innovation, VolksMolds consistently delivers reliable and efficient molds, thereby earning a strong reputation in the global market.