Considerations Regarding the Quality of Welds on Hollow Plastic Balls Obtained by Joining Two Ball Halves

Abstract

The requirements for sustainability and transition to a circular economy are key elements in the design and production of the components made by polymeric materials. The European Commission has issued a number of new directives with strict roadmaps to all State Members, in this regard. Some directives have already started to take effect; others are reaching their implementation deadlines. Limiting the consumption of raw materials and energy, as well as recyclability will lead to an increased reconversion of the current manufacturing technologies. However, all these goals must also take into account the quality aspects of the products. The testing methods must be adapted to certify the properties stated in the product sheets. This paper analyzes welding quality aspects in the production of hollow balls, made of polymeric materials, objects resulting from the joining of two hemispheres. As a case study, benchmarks from the cosmetic industry commonly known as deo roll balls were used. The first part of the paper presents the classic technology for manufacturing deo roll balls by extrusion blowing process. Below are some alternative technologies for manufacturing these balls by joining two hemispheres. The last part of the paper analyzes the welded joints by destructive and non-destructive testing methods. The basics that underlie the joining by welding polymeric materials as well as notions of rheology and material structure in the heat-affected zone are essential elements in explaining defect occurrence. A strict control of the welding parameters can offer good chances for implementing technologies to produce large series of spherical objects made of polymeric materials, objects that are made through alternative joining methods, more precisely by welding two hemispheres. The experiments carried out also highlighted some vulnerabilities of the proposed alternative technologies, their possible causes as well as the possibility of solving defects. These studies may underlie similar applications in which spherical objects are used.