Lubricant Evaluation Technique for Single Point Incremental Forming Process

Abstract

Single-point Incremental Forming (SPIF) is highly flexible dieless forming process suitable for a small batch production. The higher the feed rate and tool rotational speed, the higher the production rate will be. Therefore, the selection of the suitable lubricant is a key important factor to maintain the formability of the material when increasing the feed rate and tool rotational speed. This paper proposes the technique to evaluate and later on select the proper lubricant for these conditions. This technique was divided into two phases; 1) screening, and 2) stabilization. The screening phase is a quick method for preliminary selection of the lubricants. The stabilizing phase is a step to evaluate reliability as well as ensure efficiency of the lubricant throughout the process, because of the significant increase of the forming temperature which affects directly to the performance of the lubricant. Two types of lubricants, namely solid (Graphite) and liquid (Callington Calform NF-206) lubricants mixed with the base oil (coconut oil) at different ratios were tested. The cold rolled hot-dipped zinc-coated steel sheet with thickness of 0.176 mm. and wall angles of 45, 50, 55 and 60 degrees with the depth of each wall angle of 5 mm were used. During the screening phase, the fifteen mixtures firstly were tested by using the achieved maximum wall angles without fracture as a criterion. Later on, the lubricant mixtures which could successfully form at the wall angle of 60 degrees with the forming depth of 20 mm would be tested in the stabilization phase to evaluate the formability and the forming temperature. The results showed that during the screening phase 11 lubricants could perform successfully, while the stabilization phase with the wall angle of 60 degrees only 3 lubricants could successfully form the workpiece. Therefore, this evaluation technique could help to evaluate and, for later on, be a criterion to select the select lubricant.