Cutting to the Point: Directly Machined Metal Molds for Directional Gecko-Inspired Adhesives

Fabrication techniques for gecko-inspired adhesives generally target mold durability, adhesive performance, and process efficiency and simplicity. With these goals in mind, we present a micromachining process for creating reusable aluminum molds used to fabricate directional dry adhesives. The molds require deep, narrow and overhanging grooves to create sharp and angled adhesive features. This geometry precludes most traditional machining and lithographic material removal processes. The presented process is a hybrid of indenting and orthogonal machining, using a diamond-coated microtome blade as the tool. An FEA analysis reveals the local extent of work hardening as each groove is created, and helps to define a trajectory that reduces the effects of tool deflection and chip build up. The results of a series of experiments agree with predictions from the analysis and reveal a range of blade approach angles and a lower bound on groove spacing to achieve the desired geometry. This range is narrower than for molds machined from wax in previous work. Nonetheless, adhesive samples cast from the new metal molds achieve comparable performance to those previously cast from wax.

Investigation on Tool Deflection During Tapping

Tapping is a challenging process at the end of the value chain. Hence, tool failure is associated with rejected components or expensive rework. For modelling the tapping process we choose a mechanistic approach. In the present work, we focus on the tool model, which describes the deflection and inclination of the tool as a result of the radial forces during tapping. Since radial forces always occur during tapping due to the uneven load distribution on the individual teeth, the tool model represents an essential part of the entire closed-loop model. Especially in the entry phase of the tap, when the guidance within the already cut thread is not yet given, radial forces can lead to deflection of the tool. Therefore, the effects of geometric uncertainty in the thread geometry are experimentally investigated, using optical surface measurement to evaluate the position of the thread relative to the pre-drilled bore. Based on the findings, the tool deflection during tapping is mapped using a cylindrical cantilever beam model, which is calibrated using experimental data. The model is then validated and the implementation within an existing model framework is described.

Influence of physical properties on boring operations of AISI 1050 steel bars

The main reason for vibration and tool deflection in boring processes are the geometrical, mechanical, and physical properties of the boring bar employed. The diameter of the boring bar is rather small when compared with its length due to the nature of the mechanism in the boring process., In the present study, the influence of the physical properties of boring bars on the deflection amplitudes, natural, and circular natural frequencies were investigated both theoretically and experimentally. For that purpose, seven kinds of boring bars were used. The influence of the characters of boring bars on the amplitudes of tool deflection was investigated both theoretically and experimentally. By contrast, this influence on the natural and the circular natural frequencies were investigated only theoretically. It was found that boring bars filled with rubber and silicon recorded the smallest deflection amplitudes. Particularly, bars filled with silicon manifested the lower tool deflection amplitudes under the selected conditions. It should be added that lower feed rates and cutting depths caused severe tool deflection amplitudes. Moreover, the optimum compatibility between the theoretical and experimental results of tool deflection amplitudes was observed in bars filled with silicon ∅ 16 mm.