Page 26 - PCMI Journal December 2020

Manufacturing Bespoke Aesthetic and Functional Surfaces via Photochemical Machining, Electrolytic Photoetching and Electrolytic Photopolishing Presented by: David M. Allen, Emeritus Professor of Microengineering, Cranfield University, UK
Figure 12 (a) Micromixer consisting of two inlet channels leading into a serpentine mixing channel. The micromixer was machined into the surface of an aluminium disk 15 mm in diameter at an applied potential of 1.4 V at 75°C in a quiescent solution for a cumulative passed charge of 10 C and (b) SEM image (200x magnification) showing where the inlet channels merge into the mixing channel. The two inlets are 90 μm wide and 45 μm deep while the mixing channel is 140 μm wide and 50 μm deep [10].
Abrasive Structures
Figure 13 shows a blackened, heat-hardened steel abrasive plate (60 x 112 mm) with
an adhesive backing and cover sheet, which on removal, will allow the plate to be fixed onto an appropriate power sanding tool. The plate surface detail shows the nested circular patterns of cutting points and planing edges as described in US Patent 4,240,806 [11]. The new random orientation geometry of the 150 μm high asperities, made by PCM, gave faster abrasion and less clogging than conventional metal abrasive plates.
A similar PCM technique has been used to manufacture a stainless steel pedicure disc for removal of hard skin, as illustrated in Figure 14.
Tribological surfaces
The purpose of such surfaces is to reduce friction and reduce part wear when
contacting other moving parts. Recesses on bearing surfaces are used as reservoirs for lubricants and different reservoir geometries in dimple, groove, chevron and other shapes may be fabricated readily by conventional PCM [12].
In a very recent development, published in 2020, simulation of a Horned Viper (Vipera ammodytes) snakeskin surface texture (Figures 15 and 16) into a photoresist allowed the replication of the texture pattern onto the surface of AISI 52100 steel to form a hard (920 HV) and durable bearing [13].
Issue 136 December 2020 PCMI Journal 26