One of the best kept secrets in manufacturing, chemical etching is the “go-to” technology for often complex, safety-critical, and exacting precision metal parts and components produced by leading names across all key industry sectors. Your competitors probably already use it, but will not share or discuss the benefits as they do not want to give away the secrets of the technology enabling their products. This article will detail everything that you need to know about chemical etching, which is opening up possibilities for design engineers that were previously deemed unattainable. Chemical etching stimulates real innovation across all industry sectors as it opens up new design and manufacturing frontiers.
Albert Tsang, Technical Manager
Let’s start with a bold but incontrovertible statement.
As a precision sheet metal machining technology, chemical etching achieves exacting tolerances, is highly repeatable, and in many instances is the only technology that can cost-effectively manufacture precision metal components with the accuracy necessary in demanding and often safety-critical applications.
There are teams of manufacturing engineers in countless OEMs asking themselves the question: “which metal fabricating process is the best fit for our requirements?”
The answer is not always simple! Geometries of the part to be manufactured will vary, as will the best-fit manufacturing technology. Technology choice will be affected not only by the type of metal being processed, but also by its thickness, the required quality of cut, and the speed with which the manufacturing operation needs to be completed.
Ultimately, however, there are some givens when it comes to process selection. Cost per part and quality are key and fairly universal drivers, and the customer is judge and jury when assessing the success of the manufacturing technology finally selected. This article explains why chemical etching is being specified as the “go-to” technology by so many manufacturers.
There are numerous metal cutting technologies available to OEMs, many of them very niche in their application, and often unable to process a sufficiently wide array of materials, or provide the accuracy and precision that is increasingly demanded by important industry sectors such as medical, aerospace, automotive, chemical, and electronics.
When benchmarking technologies that are able to produce “precision” metal parts, the field is narrowed, the key players being universally recognised as stamping, punching, laser cutting, and to a lesser extent, chemical etching.
Within the context of these alternatives, the unique characteristics of chemical etching overcome many of the issues associated with traditional metal cutting technologies, and as such — in some instances — when looking for a cost-effective solution for the manufacture of precision metal parts, it is the only viable choice.
Let’s start with design
Before drilling down into the comparison between chemical etching and its traditional alternatives, a little time needs to be spent reversing into the design department.
The best design in the world is only any good if it can be manufactured, and it is therefore up to the design engineer to ensure that the parts being designed are suitable to the vagaries of the manufacturing process being used. Ultimately, therefore, it is fair to say that the constraint on the level of innovation from the design side is the capabilities and often the limitations of the chosen manufacturing technology.
Once design engineers select chemical etching as their preferred metalworking process, it is important that they fully appreciate not just its versatility, but also the specific aspects of the technology that can affect — and in many instances enhance — product design.
Chemical etching has many attributes that can truly stimulate innovation and ’stretch the boundaries’ with the inclusion of challenging product features, enhancements, complexity, and efficiency, and it is important that design engineers fully exploit its potential.
Chemical etching can be applied to a vast spectrum of metals in a variety of thicknesses
Very often, optimum success involves early stage engagement with a chemical etching specialist. A partnership needs to be forged, not a customer subcontractor relationship if the true potential of chemical etching is to be realised.
So what are the key inherent characteristics of the chemical etching process that can be exploited at the design stage?
Well, first off, chemical etching can be applied to a vast spectrum of metals in a variety of thicknesses (typically sub 1.5 mm), grades, tempers and sheet sizes (up to 600 x 1500 mm). Precision Micro stocks over 2000 material types and in addition can supply specialist materials on request as well as work with customer materials on a case-by-case basis.
Next, accuracy — a key consideration in any design. With chemical etching, standard etching tolerances of ±10% of the metal thickness are possible, to a minimum of ±0.025 mm. With development, greater accuracy can be achieved, as are component features to sizes below the standard minimum.
Design engineers also need to be aware that due to the inherent edge “cusp” created during the process, unique characteristics can be designed into products manufactured using chemical etching. Etch cusp can be controlled, and by so doing, a range of profiles can be introduced that allow the manufacture of sharp cutting edges (such as those used in medical blades), or conical openings, such as those used to direct fluid flow in filtration meshes.
Chemical etching not only copes well with difficult geometries, but it also allows design engineers enormous flexibility, facilitating the adjustment of designs right up to the point of manufacture due to the use of digital tooling (about which much more below!).
Manufacturing advantages and benchmarking
Chemical etching 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, lead frames for integrated circuit boards, fuel cell and heat exchangers plates, precision springs, washers and gaskets, and aesthetic parts such as automotive interior trim.
When compared with traditional metal manufacturing technologies, it has a number of inherent advantages.
For example, chemical etching is agnostic to metal choice. Metals suitable for etching can be both ferrous and non-ferrous and include austenitic and martensitic steels, coppers, brass and nickels. Hard to machine metals such titanium and its alloys, and aluminium can be processed, and also high-temperature alloys such as Inconel.
As an ambient temperature, no contact machining process chemical etching produces 100% burr-free, stress-free parts
When looking at each of the conventional processing technologies, each suffers from a number of drawbacks, key among which is the degradation of the material being processed due to high impact, or in the case of laser cutting the use of intense heat. In addition, traditional processes often leave burrs and require costly and time-consuming post-processing operations. As an ambient temperature, no contact machining process chemical etching produces 100% burr-free, stress-free parts.
Another crucial differentiator is in the area of tooling, which can be illustrated by comparing chemical etching to stamping.
Tooling for chemical etching is digital, 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.
Also, as the tooling is digital, it can be adapted and changed extremely quickly and economically, making it ideal for the design engineer to tweak designs right up to the eleventh hour, but also making it ideally suited for anything from prototype runs to high volume production runs. This allows for design optimisation without financial penalty, helps ensure a low-risk entry strategy, and also facilitates easy product updating. Turnaround time using photo-tools is about 90% 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 etching.
The economy and adaptability of the tooling for chemical etching is a key stimulus to design freedom, along with the ability to produce what may seem like impossibly complicated products.
Keith Jackson, CTO at Precision Micro’s parent company Meggitt, once summarised this by saying that with chemical etching “you can try stuff!”
There are no barriers to entry with the technology, as the cost of creating prototypes is low, and because complex designs can be produced in a matter of days, and designs iterations in a few hours.
Today, an increasing number of OEMs from across all industrial sectors make products that are extremely complex and also very fragile. In many instances, geometric complexity and the requirement for extremely exacting tolerances and precision mean that chemical etching is not just “a” potentially desirable manufacturing process, but is, in fact, the “only” technology able to make certain products.
Let’s take a closer look at the complexity conundrum
More often than not, when using stamping, part complexity adds cost, whether in low, medium, or high volume applications. The complexity of a product means the necessity for a complex mould tool, and complex tooling means increased costs, increased potential for tool failure, and increased lead-times for satisfactory completion.
Chemical etching is unaffected by the level of tool complexity, and it makes no difference in terms of costs or lead-time how complex the geometry of the part is and therefore the complexity of the digital tooling.
Chemical etching also has the ability to produce finer detail than is possible with stamping, and all with minimal if any degradation and deformation of the metal being processed, and little to no likelihood of burrs or defects. Failure rates are minute, and unlike in the stamping process, every part produced is absolutely flat, which in some applications is absolutely vital.
Chemical etching’s “sweet spot” is in the manufacture of complex parts in small to medium sized production runs. In extremely high volume runs where the tooling expense is justifiable, and where designs are not overly complex, stamping typically represents a more economic process.
The advantages of chemical etching over more traditional fabrication processes such as stamping and laser cutting are its low cost, high speed, flexibility, suitability for complex designs and — most important — its ability to produce burr-free components the properties of which have not been changed by heat or stress.
Standard lead-times for Precision Micro using the chemical etching technology are around one to two weeks, and even this can be shortened if there is urgent demand. For stamping, it can take months just to design, build, and de-bug a tool.
Perhaps of greatest importance, however, are the possibilities that are opened up to design engineers to innovate through the use of this versatile and cost-effective metal processing technology.