Investigation of achievable form tolerance of parts produced by polymer additive manufacturing processes for biopharmaceutical industry

Polymer Additive Manufacturing (AM) has been increasingly used to produce end-use parts and products in recent years. Continued technological advances have enabled certain polymer AM processes to make significant inroads into the biopharmaceutical industry. In Sartorius, a multinational biopharmaceutical equipment manufacturer, the three mainstream polymer AM processes, including laser powder bed fusion, vat photopolymerisation and material extrusion have been adopted for series production. A critical step to accelerate the uptake of polymer AM in new product development is to provide concrete tolerance information to product design and production departments. However, unlike established international standards for tolerances for machining and injection moulding, little information is available on form tolerance for polymer AM. Thus, this study investigates the form tolerance capability of the above three processes. An artefact was designed, which included six typical features, i.e. boss, pocket, cylinder, hole, thin wall and underside surfaces. Ten artefacts for each AM process were produced, and the form tolerance, including cylindricity, flatness, coaxiality, angularity, perpendicularity and parallelism, were measured using a Coordinate Measuring Machine. It was revealed that vat photopolymerisation achieved the best form tolerance in most cases. Coaxiality of cylinder and hole is the highest among all tolerance types, which is primarily due to accumulated deviation when printing two features combined as compared to a single feature. The achievable tolerances by the three processes vary depending on the tolerance type, but they were all found to be capable of producing parts with excellent and consistent parallelism and angularity.