Influence from production parameters on the surface roughness of a machined short fibre reinforced thermoplastic

Machining is a relatively new manufacturing method for short fibre reinforc ed thermoplastics (SFRTP), and the theory and experience from other materia ls cannot be directly applied. It is therefore necessary to set up new guid elines for how to ensure a satisfactory result from the machining. Experime nts were carried out to study how the surface roughness of a SFRTP, machine d by turning, was influenced by variations of the feed rate, the cutting sp eed, the tool radius, the fibre orientation and the interactions between th em. The roughness increased for an increasing feed rate and a decreasing to ol radius. These parameters interacted, which shows the difficulty of decid ing the setting of the production parameters by trial-and-error. Interactio n also results in more complicated guidelines for the machining. A slight i nfluence on the roughness was found for low cutting speeds, whereas higher speeds had no significant influence. The roughness was found to be independ ent of the fibre orientation. The overall conclusion was that it seemed to be possible to set up guidelines for an optimal machining of SFRTP. These r ecommendations differ from the theoretical ones applicable for the machinin g of metals. (C) 1999 Elsevier Science Ltd. All rights reserved.