Differences And Technical Challenges in Heating Molding Techniques Of Hollow Cup Machine And Ordinary Paper Cup Machine

In the field of packaging container manufacture, hollow cup machine and ordinary paper cup machine, as two kinds of core equipment, have great difference in heating and molding process, which directly affects product performance, production efficiency and equipment stability. This paper analyzes their differences from three aspects of ofprocess principle, temperature control and mold design,and discusses their technical challenges.
I. Core Differences differences between heating and Forming Processes
1.Process principle: Biaxial Stretching vs. Unidirectional Pressing
Hollow cup machine adopts the technique of biaxial tensile forming and realizes the directional alignment of the material by the synergistic effect of axial stretching and radial blow expansion. For example, in the production of polycarbonate (PC) hollow cups, billets are heated to 250–310°C, then stretched axial on the mandrel to the design height while compressed air (0.35–0.7 MPa) is injected to induce radial expansion, which is then cooled and molded in the die. This process arranges molecular chains along the tensile direction, greatly increasing the shock resistance and transparency of the product.
Instead, ordinary paper cup machines rely on unidirectional hot-press forming. The process involves placing the blower billet in a packing mold, heating the the longitudinal seam at 180–220°C, heating it with a hot seal, positioning the bottom of the cup through vacuum suction, and then sealing the cup with a a a crimping process. This method requires lower material ductility, but requires precise control of the heat seal temperature to prevent paper carbonization or coating degradation.
2.Temperature control: gradient and temperature distribution. Precise regulation
Hollow cup machine requires multi-region temperature gradient control. For example, in the production of high-density polyethylene (HDPE) vats, the temperature of the extruder drum is broken down to 175–210°C, the cooling water temperature of the die is maintained at 6–10°C, and when blown in parallel, the temperature of the die must be precisely controlled at 80-85°C to 75-80°C to 60° C. This complex temperature system balances the fluidity and crystallinity of the material and avoids wall thickness variations due to uneven heating.
Temperature control of ordinary paper cup machine mainly focuses the hot sealing head and roller. The thermoseal temperature of the PLA cup must be dynamically adjusted according to the melting point of the coating (usually 160-180°C), while infrared sensors continuously monitor the temperature of the thermoseal area to ensure sufficient seal strength without damaging paper fibers. Some advanced models use ultrasonic sealing technology to generate heat through high frequency vibrations and achieve adhesive-free sealing, eliminating the risk of material degradation due to overheating.
3. Mold Design: Dynamic Adaptation and Static Positioning
The die of hollow cup machine requires dynamic adaptability. For example, in the moltencore blowing process, the molded core must be precisely designed according to the inner cavity shape of the product at a melting point 5-10°C below the solidification temperature of the plastic. In the production of PC kettle, the core is made of tin lead bismuth alloy with low melting point, which is melted and discharged through a special pipe. The die must have an expansion capacity of 0.5 -1 mm to prevent cores from solidifying and cracking.
Static positioning accuracy is very important in Regular paper cup machine die. The gap between molds used for cup body forming must be controlled to ±0.05 mm to ensure correct alignment of the longitudinal seam when packing billets. The cup bottom socket is precisely positioned with a -80 kPa negative pressure vacuum suction system, and the curling wheel pressure can be adjusted (usually 0.2-0.5 MPa) to meet sealing requirements of different weights of paper.
ii. Analysis of technical challenges
1.Hollow Cup Machines: Multi-Physics Field Coupling Control
The hollow forming process involves complex coupling of heat transfer, hydrodynamics and phase change reactions. For example, in PC hollow bottle production, the parison blow expansion stage requires simultaneous control melt viscosity (temperature-dependent), blow pressure (gas-flow-related) and mold cooling rate (heat-conduction related). Any parameter fluctuations may lead to defects, such as crystallization spots, flash points or uneven wall thickness. Current solutions include:
Dynamic temperature compensation Based on temperature compensation control algorithms
Integrated laser thickness to monitor wall thickness in real time;
CAE simulation of mold runner Design
2. Plain Paper Cup Machine: Material Adaptability Challenges
With environmental regulations tightening, ordinary paper cup makers must adapt to novel materials such as PLA and bamboo fiber. For example, technical challenges in producing uncoated paper cups include:
absorption control: Adhesives reduce water absorption to ≤3%, preventing deformation during molding
Narrow Thermal Seal Window: Development of Precision Temperature Control System for Narrow Melt PLA Materials (±5°C)
Waste recycling: Design Mould, 100% Recycling edge trimmings
III. Technology Development Trends
Hollow cup machines are moving towards intelligence. defect detection systems based on machine vision can recognise variations in 0.1mm wall thickness in real time, while digital twin technology reduces mould conversion time by 40% through virtual commissioning. Common paper cup machines focus on green manufacturing, such as permanent magnet synchronous motors energy consumption reduced by 15%, development of water-based ink printing processes, reducing volatile organic matter emissions. The technological convergence of these two equipment types is driving packaging container manufacturing toward higher efficiency, accuracy and sustainability.