Simulation of the plug-assisted thermoforming of polypropylene using a large strain thermally coupled constitutive model

Evaluation of the Thickness and Oxygen Transmission Rate before and after Thermoforming Mono- and Multi-layer Sheets into Trays with Variable Depth

“…Various studies have been conducted to assess the effect of processing parameters, such as mold temperature, film temperature, plug velocity, plug holding time, and plug clearance, on the wall thickness distribution. These parameters are strongly related to the thermoforming window of the tested polymers [12][13][14][15]. Amorphous polymers, such as polystyrene (PS), can be shaped with relative ease above their glass transition temperature and generally exhibit relative wide thermoforming windows [2,12], whereas semi-crystalline polymers, such as homopolymer polypropylene (PP), are more difficult to thermoform because they are so fluid above melting temperature that they must be processed within a narrow temperature range around the crystalline melting point [2,14,15].…”

“…These parameters are strongly related to the thermoforming window of the tested polymers [12][13][14][15]. Amorphous polymers, such as polystyrene (PS), can be shaped with relative ease above their glass transition temperature and generally exhibit relative wide thermoforming windows [2,12], whereas semi-crystalline polymers, such as homopolymer polypropylene (PP), are more difficult to thermoform because they are so fluid above melting temperature that they must be processed within a narrow temperature range around the crystalline melting point [2,14,15]. Furthermore, the optimization of the thermoforming process is even more complicated when a combination of polymers within a multilayer structure is processed, e.g., ethylene-vinyl alcohol co-polymer (EVOH) coextruded as an internal layer within PP, PS, polyethylene (PE), amorphous polyethylene terephtalate (APET), and/or polyamide (PA) layers [15].…”

“…In addition to traditional trial and error methods for product and process development, researchers have made significant advances in the simulation of thermoforming processing techniques. O'Connor et al have summarized experiments and test equipment that are able to simulate polymer behavior during thermoforming [14]. From these experimental test results, finite element analysis programs can be developed to model a wide range of mold geometries and polymer processing techniques, to predict and optimize the material distribution in a part prior to any thermoforming process [10,14,15].…”

An Experimental Study on Wall Thickness Distribution in Thermoforming

“…Some engineering packages that are based on Finite Element Analysis, are Ansys Polyflow, Abaqus, T-sim, Pam-form etc. Using simulation software is very effective to estimate how plastic deforms before real thermoforming operations especially in terms of lowering tool costs [3,5,8,14]. Heat transfer during heating plastic, applying positive or negative air pressure, including plug assist, deformation behavior of plastic material is possible to simulate by engineering packages mentioned before [3,8,14].…”

Improvements in thermoforming simulation by use of 3D digital image correlation

“…Secondly, the simulation software does not take into account all thermal and physical aspects of this complex process within its material models since not all characteristics of the large amount of possible thermoforming materials, at thermoforming conditions, have been researched and parameterized for usage in simulation software. Different material models were tested and compared to reality in either bubble inflation or actual forming experiments, an extensive overview of previous studies is given by O'Connor et al in [3]. Thirdly, variation of process parameters in practice jeopardizes the process robustness and requires higher safety margins and initial blank thicknesses.…”