Polymer-Binder Powder-Bed Routes ER-155 Engineering Review

Indirect polymer-binder powder-bed shaping uses selective thermal energy to join binder-bearing particles into a green geometry, followed by depowdering, debinding and densification. The route is variously described as indirect selective laser sintering, indirect laser powder-bed fusion, polymer-assisted powder-bed processing or, in commercial implementations, cold fusion. These names can obscure the essential distinction between the phase that creates the printed bond and the material expected in the final product. This qualitative engineering review follows the complete state chain from released powder-binder feedstock to accepted metal, ceramic, glass, carbide or other advanced material. It examines composite-powder architecture, binder distribution, powder flow and spreading, bed packing, energy absorption, thermal softening, neck formation, scan history, curl, build layout and green-body removal. It then treats green metrology, depowdering damage, green machining, geometry-dependent binder removal, sintering, infiltration, isostatic pressing, shrinkage, distortion, phase control and final-property qualification. The analysis shows why a broad shaping window can coexist with a narrow final-product window. Binder improves green cohesion but increases organic-removal burden; bed support enables complex green shapes but does not prevent weak-feature damage; dense nesting can improve machine utilisation while overloading depowdering or furnace capacity; and lower shaping temperature does not establish lower total energy or cost. Material-specific examples in alumina, silica, glass, silicon carbide, carbon-fibre/SiC, aluminium and infiltrated metal systems demonstrate feasibility and expose non-transferable assumptions. A three-level qualification gate separates feedstock and machine capability, thermal-conversion capability and final-product acceptance. The paper concludes that the route is selected correctly only when its complete-cell advantage survives evidence for powder genealogy, green integrity, binder removal, dimensional transfer, final composition, defect population, property statistics, safety and accepted-part economics.