Wear Mechanisms and Performance of PET Shredder Blade with Various Geometries and Orientations

Abstract

Shredder blade is the main component of a shredder machine used in plastic recycling. A comparative performance study was conducted on the shredder blade with different geometries and orientations to understand its wear and shredding mechanism. Identification of the loading distribution along the shredder blades was observed in different orientations. The microstructure and hardness of the worn cutting edge and as-received shredder blade were characterised by optical microscopy, scanning electron microscopy along with the energy dispersive X-ray, X-ray diffraction analysis and hardness testing. The wear mechanism in the shredder blades was categorised as progressive wear. The progressive wear was due to the abrasive, adhesive, and oxidation wear. Recycling efficiency, shredding efficiency, and percentage retention are the parameters used to evaluate the performance of the machine with various geometries and orientations. The best combination of the geometry and orientation is the double-edge shredder blade with spiral orientation, which exhibited recycling efficiency at 97.39 ± 0.04%, shredding efficiency at 69.53 ± 1.32%, and retention at 2.61 ± 0.04%, along with a smaller number of blades recorded severe wear.

Wear processes and performance of blade pair in small‐scale single‐shaft plastic shredder machine

“…The shredded workpieces crumbled randomly which might wind up at the blade pair resulting an increase of the retention percentage. Comparatively, current shredder machine was able to maintain the performance after increasing the loading of the workpieces from 1.25 kg to 5.0 kg [15]. This indicated that the small‐scale single‐shaft shredder machine able to shred a higher loading of workpieces without deteriorating its shredding performance.…”

“…A small-scale single-shaft shredder machine for polyethylene terephthalate (workpiece) was built and the experimental procedure was done with some modification based on reference [15]. The specifications of the smallscale single-shaft shredder machine were: (i) rotational speed: 47 min À 1 and (ii) throughput: 10 kg h À 1 .…”

“…The shaft consists of 10 spacers and 9 shredder blades and assembled adjacent to the 10 fixed blades and 9 dividers, respectively, based on reference [15]. All the components in the small-scale single-shaft shredder machine were made of low-carbon steel since it is available at minimal cost, and ease of welding due to its specific properties [11,12].…”

“…Based on the studies, helix and V‐configuration shredder blades provide a better shredding performance with a better grab on the plastic workpieces and uniform loading distribution on the cutting‐edge to reduce retention in the shredder machine. Nevertheless, helix configuration of two‐edge shredder blades provided better shredding performance than the V‐configuration [15].…”

“…Wear conditions between the blade pairs and polyethylene terephthalate plastic are complicated to be observed and quantified due to the random shifting of the workpieces during the shredding process. Hence, estimating the wear mechanism of the blade pairs using laboratory scale models is difficult [15,16].…”