Improving the Machining Efficiency of Mold Guide Grooves Using A Separable-Insert Method: An Experimental Comparison of Machining Time, Tool Wear, And Surface Roughness

Abstract

Machining the complex working surfaces of metal mold dies — in particular the narrow guide grooves along which thread-forming components move — is one of the most time-consuming and tool-intensive operations in mold making. When such grooves are cut directly into the monolithic die body on a vertical milling machine, the long, small-diameter end mills required have low rigidity, are prone to vibration, wear rapidly and leave a poor surface finish, while repeated re-clamping and special fixtures extend the cycle time. This paper proposes and experimentally evaluates a separable-insert method, in which the difficult-to-machine groove zone is removed from the die body, manufactured as a separate small insert under favourable cutting conditions using rigid standard tools, and then installed into a milled seat by a transition fit secured with a bolt. Comparative experiments were carried out on 40X alloy steel (28–32 HRC) using a DMC 1035 V CNC milling centre, with five specimens machined by each method. Machining time, flank wear (VB) and surface roughness (Ra) were measured and compared. The separable-insert method reduced the mean machining time from 281.2 to 184.2 min (−34.5%), reduced flank wear by 32.4% with a corresponding increase in tool life, and improved surface roughness from Ra 1.42 to 0.77 µm (−45.8%), while the coefficient of variation of Ra fell from 9.7% to 6.4%. A two-sample Student t-test (P = 0.95) confirmed that the differences in machining time and surface roughness are statistically significant. The results show that the proposed method substantially improves the machining efficiency and surface quality of mold guide grooves and is suitable for industrial implementation.