Förstå och minska bildandet av sliver vid stansning av plåt: En experimentell och numerisk studie tillämpad på C45E-stål

The formation of metal slivers during cutting and stamping operations is a major defect that affects part quality and tool wear, especially in the automotive industry where throughput is high and tolerances are tight. This work aims to identify the geometric parameters influencing this phenomenon and to better understand its mechanisms. The study focuses on a 12-stage progressive tool used to produce ball-bearing rings from C45E steel for the automotive industry.Each stage performs a distinct forming or cutting operation along the strip. Sliver formation was primarily observed in three tool regions — stages 4–5, 8–9, and 11–12 — corresponding respectively to cutting the carrier outline (thin metal bands connecting each part to the strip and designed to bend during forming), center-hole trimming, and final ring separation.A Taguchi L16 experimental design was implemented with six factors: the punch and die edge radii for all cutting operations (2 factors) and the punch–die clearances for stages 1, 2, 3, and 8 (4 factors). Fifteen tests of 400 cycles each were performed, with systematic collection of sliver number, size, length, and type. Statistical analyses using Ellistat showed that sliver count was highly random and poorly correlated with the studied factors (R² between 0.155 and 0.251), whereas morphology depended strongly on local tool geometry and on the clearance of the preceding cutting stage.In the stage 8–9 area, larger punch radii increased flake width by about 0.302 mm per 0.1 mm rise in edge radius (p = 0.012), while in stage 11–12, a larger die radius increased overall flake size by 0.051 mm per 0.1 mm (p = 0.055). In stage 4–5, greater clearance at stage 3 produced longer flakes, with an effect of +0.874 mm per 0.1 mm increase (p = 0.050). Numerical simulations confirmed that slivers form when previously sheared edges re-contact the tool and detach more easily after local deformation.This study shows that while sliver frequency is difficult to predict, morphology can be controlled by adjusting punch–die clearance and tool radii. Combining experiments and simulation provides practical guidelines for tool optimization: limit punch and die radii to reduce flake size, finely tune early-stage clearances to minimize flake length, and design dies to prevent unnecessary contact between the die and the strip such as U-shaped grooves to prevent carrier contact.