3 Things That Make Precision Metals Precise
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How do you define “precision metals” for your product or manufacturing needs?
In the world of metal machining, people are often looking for what they call precision metals. But what exactly does that mean? Depending on the application, the term *precision* can pertain to a number of characteristics. These include the precision of a metal’s dimensions, the precision of its composition, and the precision of the metal’s performance. What, then, is important to consider about precision metals for your product or manufacturing need in terms of each of these important characteristics?
The Dimensions of Precision Metals
For our customers, dimensions are the primary focus when it comes to precision metals. In fact at Metal Cutting, where we hold the very tightest cutting tolerances with the highest Cpk/Ppk values, our methods will deliver a level of dimensional precision that may actually be greater than what a customer needs.
In general, precise dimensions and cost are highly correlated, in that greater precision comes along with a higher price tag. That is because attaining precise dimensions usually require machinery that itself has the tightest tolerances, being made from components of the tightest tolerances. Moreover, to get the ultimate results from this machinery requires years of experience, requiring the best operators. Therefore, the cost of the machinery and labor — and, ultimately, the cost of precision metals with dimensions of the tightest tolerances — is high.
Is the precision of laser worth the cost?
One great example is laser processing. While it can be versatile and precise, producing tight tolerances and small kerfs, laser cutting is generally slow and expensive, especially for 2-axis cutting. While large power lasers can make faster cuts, in doing so they produce rough end cut surface finishes and wide, deep heat-affected zones — probably not the results you’re looking for in precision metals. For laser cutting of tubing, the inside of the tube must be coated with anti-spatter fluid and the materials must be laser cut one at time, both of which increase production time and add to the cost.
Is 3D all it’s cracked up to be?
Another example of the tradeoff between cost and dimensions is 3D manufacturing. Here, the laser sintering process relies on a number of variables, including the size of the laser, the laser spot, the micron size of the metal powder, and finally, the height intervals of the ”elevator” steps presenting the fresh powder to be laser sintered. In the early days of laser sintering, these gradations — especially the height interval of the elevator steps — were quite large compared with the contemporaneous state-of-the-art Swiss-style turning and milling machines. So, although the 3D method could add metal features that could never be achieved through subtraction using conventional machining, the end product was surprisingly rough looking due to the comparatively poor resolution of early 3D printing.
At least when it comes to direct metal laser sintering, while the precision of the intervals and powder and laser size have now improved greatly, some of those basic tradeoffs remain. For instance, there have been some extraordinary advances in shrinking the laser spot; however, because of the nature of sintering, along with this comes an increase in the time required to additively construct a part, making for higher part prices. And so we have another example of where greater precision correlates with higher cost.
In addition, with the nature of sintering and the challenges of annealing, laser sintering a material such tungsten element remains a work in progress. While some advances have been made, successful 3D printing of tungsten remains elusive.
The Composition of Precision Metals
There are a lot of engineered metals and alloys whose composition makes them “precise.” One famous example is nickel titanium alloy. First popularly used back in the day to make eyeglass frames, niti (or nitinol) is what provided the frames with shape memory and super elasticity — enabling the rugged frames to withstand being bent and to pop back into shape. Today, niti is used widely for tubing in the medical device industry. (You can learn more about niti and other tubing materials in our white paper Medical Device Tubing in the 21st Century: Who Needs It?. Another example is tungsten element, which requires a precise composition in order to achieve its desired and very specific performance goals.
Tungsten element and niti neatly illustrate the basic dichotomy in the chemical composition of precision metals: namely, purity vs. recipe. For some applications, a precision metal is a pure element, such as tungsten element. But for other applications, it is a blend requiring a specific recipe.
Purity testing is done with both pure precision metals and those that come from a recipe, determining the number of decimal points of purity (How pure is it? e.g., 99.95% to 99.99%) and the exact percentages of ingredients (*Was the exact recipe achieved?* e.g., 55% nickel by weight).
The recipe will vary, but the results must be precise.
For example, niti is a custom blend, varies by manufacturer, and is never exactly a 50/50 blend. In fact, while there should be ASTM specifications for all metals, there are exceptions and niti is a case in point: There is no ASTM spec for it. Even “pure” metals, such as pure titanium, can have various recipes (basically alloys) and be available in different grades.
Another good example is stainless steel, which is frequently alloyed with other metals; different manufacturers produce their own unique brand of stainless steel using a secret recipe that requires precision. The same way that not all peanut butters are the same — even when they use the same ingredients — not all stainless steels are the same. Each recipe must meet purity testing requirements for a certain ratio of ingredients, put together consistently and repeatedly, to produce precision metals.
Purity can also determine the results.
In our business, our pure tungsten element is in demand for use in projector lamps such as in small, portable, self-contained projectors often utilized by businesspeople to display presentations from their laptop or notebook computers onto a screen. These small units require a very intense lamp, and the tungsten element used must be very pure to achieve that level of performance. Metal Cutting has 99.999% pure tungsten powder, which when sold in rod form delivers 99.99% pure tungsten element; this reduced purity is some due to some tiny amount of impurity entering in the process.
The Performance of Precision Metals
Performance may be closely related to a metal’s composition. For instance, a new metal may be invented or an alloy specially engineered to deliver a particular performance. Again, niti is the poster child for shape memory, super elastic alloys. (Imagine finding out the hard way that those vintage aviator sunglasses bought at the thrift store are NOT made with niti!) In another example, an application requiring the high melting point characteristic of tungsten — such as, famously, the incandescent bulb — would require the purest tungsten element; otherwise, the material would not perform correctly and would fail prematurely.
Another precision metal utilized for its performance is magnesium, which along with iron, zinc, and manganese is finding wide application in medical devices due to its bioabsorbable properties. While we might imagine that the performance relates to spaceships, rockets, radar, satellites, and other complex, high-energy processes and equipment, there is probably no more important application than making sure that magnesium used in bioabsorbable stents is made precisely and will degrade safely within the body as designed.
The most important characteristic of precision metals — the thing that makes a particular metal precise — is going to vary depending on your application and production goals. As a precision metal fabricating company, Metal Cutting Corporation is an expert in very tight tolerance cutting, grinding, and polishing of metals for a wide range of applications. We also provide secondary operations such as bending, angle cutting, and pointing and slotting of small diameter tubes, wires, and rods; in addition, tungsten and molybdenum products, such as wire, ribbon and rod, are available
Whether your emphasis is on dimensions (as it is here at Metal Cutting), composition, or performance, you can help to ensure you get the right results by carefully crafting your parts specifications. For tips on specifying tolerances, materials, cutting methods, and other requirements for your small parts needs, download a free copy of our comprehensive guide, How to Fine-Tune Your Quote Request to Your Maximum Advantage: Frequently Asked Questions in Small Parts Sourcing
For tips on how to choose the right vendor for your metal parts needs, please download our free guide, 7 Secrets to Choosing a New Contract Partner: Technical Guide to Outsourcing Your Precision Metal Fabrication.
Metal Cutting Corporation manufactures burr-free tight tolerance parts from all metals. We provide the precision required by medical device, automotive, electronic, biotechnology, semiconductor, aerospace, fiber-optic, electrical and many other diverse industries.
We are specialists with over 45 years cutting, grinding, lapping, polishing and machining metal parts. Our experience, inventory and capabilities provide the skills and capacity to meet the needs of technology device manufacturers. Specialty metals, micron tolerances, low or high volumes, complex metrology--all these and more are the requirements we achieve every day for products shipped worldwide.