Numerical Analysis of the Forming Mechanism of Exit Burrs in Metal Milling under Ice Boundary Constraint

In metal processing, exit burrs are usually inevitable, which is a huge challenge for high-precision manufacturing. This paper innovatively proposes an ice boundary constraint (IBC) method to actively suppress exit burrs to obtain better workpiece edge quality. Firstly, the formation mechanism of the exits burr is analyzed from the perspective of material flow at the edge of the workpiece, and the principle of the IBC method is explained. Secondly, a finite element model (FEM) is established to analyze the stress distribution and flow at the edge of the workpiece, so as to reveal the suppression mechanism of IBC on the exit burrs. Finally, the feasibility of IBC method and the validity of FEM are verified by the milling experiments. The experimental results show that the IBC method can reduce the exit burr height by 51.4% on average, and FEM can effectively predict the height of the exit burr. The IBC method proposed in this study can provide some reference and guidance for the active suppression of exit burrs in industry.

Analysis of the Influence of Blanking Clearance on the Wear of the Punch, the Change of the Burr Size and the Geometry of the Hook Blanked in the Hardened Steel Sheet

In this thesis, the results of an experimental analysis of blanking angled hooks with a punch of a sloping face in a thin steel sheet with a hardness of 55 HRC are presented. The blanking punch was made of K340 cold-work tool steel. Tests were carried out for three values of clearance, 5%, 10%, and 15% of sheet thickness. The results of the analysis of the influence of the number of cuts made by the punch on the growth of the burr at the sheet edge were presented. Moreover, the influences of the clearance on the initial values of burr (b_h), deflection (H_b), and the bending radius (R_b) of the hook have been shown. The influence of the friction path on the intensity of degradation of working surfaces and the blanking edges of the punch was also demonstrated. The obtained results allow the selection of the proper clearance and new tool materials for blanking blades working in particularly difficult tribological conditions.

Investigation on the Effect of Drill Geometry and Pilot Holes on Thrust Force and Burr Height When Drilling an Aluminium/PE Sandwich Material

Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product. Damages such as the burr at the drill entrance and exit, geometric deviations and delamination are typically found in composites subjected to drilling. Drills with special geometries and pilot holes are alternatives used to improve hole quality as well as to increase tool life. The present study is focused on the drilling of a sandwich composite material (two external aluminum plates bound to a polyethylene core). In order to minimize thrust force and burr height, the influence of drill geometry, the pilot hole and the cutting parameters was assessed. Thrust force and burr height values were collected and used to perform an analysis of variance. The results indicated that the tool and the cutting speed were the parameters with more weight on the thrust force and for burr height they were the tool and the interaction between tool and feed. The results indicated that drilling with a pilot hole of Ø4 mm exhibited the best performance with regard to thrust force but facilitated plastic deformation, thus leading to the elevation of burr height, while the lowest burr height was obtained using the Brad and Spur drill geometry.