SECTION TITLE
MATERIALS • PROCESSES • FINISHES
Dr Angel Lopez discusses precision titanium parts and photo chemical etching THE PCE PROCESS T
he demand from many sectors of industry today is for the use of lightweight but strong metals for a variety of applications. As such, titanium is often the material of choice for components used in end-use medical and aerospace products due to its high strength- to-weight ratio, its biocompatibility, corrosion resistance, extensive temperature range and low thermal expansion coefficients. But titanium is a notoriously difficult to
process metal, due in no small part to its inherent attributes. It is time-consuming and extremely awkward to machine, and abrasion-based technologies produce a lot of waste, which with such an expensive metal is to be avoided. Even when considering the use of next- generation metal processing technologies such as photo-chemical etching (PCE) – which is a “corrosive” process – anti- corrosive titanium presents issues that have to be overcome by an intelligent and well-informed focus on etchant chemistries. Very few etching companies possess the know-how and understanding of the PCE process to be able to produce such etchant chemistries, which explains why so few PCE companies can produce titanium parts
with the required geometric complexity and accuracy at volume.
WHAT IS PCE?
PCE is the go-to metal fabrication technology when the focus is on the production of highly accurate, geometrically complex, feature-rich, burr- and stress- free parts and components. It consists of a number of steps, some of which are fundamentally different from legacy metal fabrication process, and which open up an array of hitherto impossible opportunities for designers and manufacturers. First, and most obviously different from traditional production processes is tooling. For PCE, there is no need for hard tooling with all that this requires in terms of cost and lead-time, but instead the process uses digital photo-tools created from customer CAD data. Most PCE suppliers use digital photo tooling created on films, but PCE tools can also be produced on glass which can achieve greater precision and attain tighter tolerances. Glass photo tooling can achieve tolerances in the range of 1-2 microns, and negates issues with distortion due to environmental factors such as humidity that are a constant problem when using
film tooling. Using glass tooling, over a 700 mm etch area, it is possible to consistently achieve 5-10 micron tolerances, whereas PCE companies using film-based tooling can only claim 50-60 micron tolerances. Digital photo tooling is by its very
nature quicker to make than traditional tools for such processes as stamping, has a higher resolution, and exhibits greater life- time stability. Once the digital tool is created and
arrayed in such a way as to maximise the number of units per sheet, the metal to be processed is prepared and cleaned, and then the photoresist is applied. Once in place, the phototool image is applied to the metal sheet, and reacts with the photoresist. Te phototool allows UV light through in some areas (which harden the resist) and blocks it in others (meaning no hardening or curing). Te etchant is then applied to the sheet, dissolving the bare metal but not the metal covered in resist. Finally, the resist is removed, and the sheets of finished components are ready for inspection and packaging.
PROCESS ADVANTAGES Te easy-to-produce and low-cost tooling used in the PCE process allows
Micrometal’s customers benefit from the positive attributes of titanium without the use of dangerous chemicals
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The PCE process means parts are free from damage and inconsistencies
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