Jochen Kern, Head of Sales & Marketing, micrometal
There are numerous metal cutting technologies available to OEMs, from oxyfuel cutting and plasma cutting, all the way through to laser cutting, punching, stamping and electrical discharge machining (EDM). Some of the less common metal processing technologies suffer from an inability to process a significant number of materials, or they do not provide the accuracy and precision that is increasingly demanded by industry sectors such as aerospace, automotive, chemical, electronics and medical.
As such, when benchmarking technologies that are able to produce precision metal parts, the field is narrowed, and most people consider the viable alternatives to be photochemical etching (PCE), stamping, punching and laser cutting. The unique characteristics of PCE overcome many of the issues associated with more traditional metal cutting technologies, and when looking for a cost-effective solution for the manufacture of precise metal parts, it is sometimes the only viable choice.
Traditional metal cutting technologies
In this article, the main focus of comparison will be between PCE and stamping, as both can produce whole intricate metal parts at volume. Punching is a relatively limited technology, in that it is not used to make complete parts but specific features (such as holes or slots) on parts. Also, while punching is characterised by its relatively low tooling costs, it is usually only appropriate for low-to-medium production runs.
Laser cutting also has some inherent disadvantages. First, the thickness of the material affects the quality of the cut of a laser. For thin materials, a very thin kerf, approximately the width of a human hair, is easily achievable. However, as the material becomes thicker, the cut becomes less clean. This is because when thicker materials heat up, the cut line itself starts to fill with molten metal slag, choking the cut. This can only be overcome through the use of a secondary blowing process to remove the slag, which adds to the cost. In addition, laser cutting involves high power consumption in comparison with alternative technologies, and the rate of production varies significantly depending upon the thickness of the workpiece, type of material and type of laser.
Stamping is an automated, high-speed process suitable for large production runs that make the requirement for initially high tooling costs tolerable. The sheet metal, which is typically in roll form, is pierced along both edges to create indexing holes that position the sheet during further processing. The location holes are used to advance the sheet metal strip through the stamping machine. Conventional stamping processes can provide an apparent cost advantage when precision, quality and repeatability are less critical. However, these savings are quickly lost when secondary operations are needed to achieve flatness, functional edge precision and exacting size features, which are required for component performance in many applications. Stamping is usually utilised for the manufacture of a whole part or multiple whole parts that can be produced at the same time.
Photochemical etching (PCE) can be used to produce a minimum hole diameter of 80 percent of the material’s thickness at repeatable single digit micron tolerances.
Benchmarking PCE
PCE is a metal processing technology that produces stress-free, flat components by selective etching through a photo-resist mask. It is especially well suited to the manufacture of precision parts such as grids and meshes, precision filters, sharp piercing or cutting edges, lead frames for integrated circuit boards, fuel cell and heat exchanger plates, precision springs, and washers and gaskets.
PCE has a number of inherent advantages over the aforementioned conventional production processes, key among these being:
- it is possible to produce parts without degrading material properties;
- there is almost no limit to part complexity; and
- a wide range of materials can be processed.
Metals suitable for PCE can be both ferrous and non-ferrous and include:
- austenitic and martensitic steels, coppers, brass and nickels;
- hard to machine metals such as titanium and its alloys, and aluminium;
- high-temperature alloys such as Inconel; and
- precious metals, including silver.
Each of the conventional processing technologies has several drawbacks, kmost notably degradation of the material being processed due to high impact and, in the case of laser cutting, the use of intense heat. However, the other major differentiator is in the area of tooling, and this can be illustrated by comparing PCE with stamping. The tooling for PCE is digital or glass, so there is no need to start cutting expensive and difficult to adapt steel moulds. This means that large quantities of products can be reproduced with absolutely zero tool wear, ensuring that the first and millionth part produced are precisely the same.
Furthermore, as the tooling is virtual, it can be adapted and changed extremely quickly and economically, and so is ideally suited for anything from prototype runs to high-volume production runs. It allows for design optimisation without financial penalty, helps ensure a low-risk entry strategy and facilitates easy product updating. Turnaround time using digital or glass tooling is about 90 percent less than that for stamped parts. Stamping requires substantial investment in mould fabrication, which is not only costly but, in some instances, can take from six to ten months to complete, compared with a few hours for PCE.
The economy and adaptability of the tooling for PCE is a key stimulus to design freedom, along with the ability to produce what may seem like impossibly complicated products. As the cost of creating prototypes is so low, there is no barrier to entry, with complex designs being produced in a matter of days and design iterations in a few hours. Perhaps the key drawback for industry in general is that in many instances, PCE is not part of some engineers’ repertoire, and because of this, innovation can be somewhat stunted. PCE pushes back the barriers that constrain many design engineers and allows for the manufacture of parts many thought impossible.
PCE can be used to produce extremely small holes that have novel cone-shaped openings, making them ideal for filtration applications.
Complexity
Many of today’s products are extremely complex and very fragile. Indeed, in many instances, geometric complexity and the requirement for extremely exacting tolerances and precision mean that PCE is not just a potentially desirable manufacturing process but in fact the only one able to make certain products.
The complexity of a part adds to the cost when stamping, whether in low-, medium- or high-volume applications. A complex product requires complex tooling, and complex tooling means increased costs, increased chance of tool failure and increased lead time for satisfactory completion. With PCE, it makes no difference how complex the geometry of the part and therefore the digital tooling are. Costs and lead times do not increase with this increased complexity.
PCE can produce finer detail than is possible with stamping, and there is no degradation and deformation of the metal being processed, and no burrs or defects produced. Failure rates are minimal, and every part produced is absolutely flat, which is vital in some applications.
Stamping fabricates a product by pressing a substrate into a mould and forming a shape. It is best suited economically to extremely high-volume runs, where the tooling expense is justifiable and where product geometry is not too complex.
PCE is a more complicated process, and so it can be applied to more complex geometries and can achieve exacting levels of precision. There is a number of variables in the process that can lead to tolerance creep, but such risks can be negated by employing a PCE specialist such as micrometal.
Photochemically etched parts can be delivered on reels to enable a highly efficient, ongoing automatised production process.
micrometal