Solving challenges of small part machining

CoroDrill® 462 and CoroDrill® 862 mark a new era for micro drilling difficult-to-machine materials

“If you can’t do the little things right,” wrote the retired US admiral and author William H. Raven, “you will never do the big things right.” This approach certainly applies to small part machining, where the advantages of smaller electronic components benefit a range of sectors like medical, automotive, electronics and aerospace. But could manufacturers be better equipped to produce smaller parts productively and cost-effectively? Here, James Thorpe, global product manager at the leader in metal cutting Sandvik Coromant, explains how its new CoroDrill^® range of micro drills can help manufacturers increase productivity and tool life.

 Technologists frequently predict the end of Moore’s Law, a famous prediction by the engineer and Intel Corporation founder Gordon Moore that the number of transistors that can be made on an integrated circuit doubles every two years or so. In 1965, Moore predicted that the number of circuits on an integrated circuit would double to an incredible 65,000 by 1975. When this forecast proved true, Moore’s Law was established and is called the “the greatest technological prediction of the last half-century” by Massachusetts Institute of Technology (MIT).

Moore’s Law has become something of a golden rule for the computer industry, as the biggest electronic device manufacturers, like Intel and Samsung, continue to squeeze ever more functionality into each square micron for applications like medical, automotive, electronics and aerospace.

The advantages of smaller modern devices are most clearly seen in electronics. Smaller digital circuits can do more processing in less time and smaller transistors can pack more storage space in the same volume, while smaller and more numerous pixels in screen displays can achieve a higher resolution. Take the rising trend of minimally invasive surgery, for instance, which demands surgical tools and medical devices that are more intricate to minimize the size and degree of incisions a surgeon makes.

But what about the supposed end of Moore’s Law? A road-mapping initiative by the Institute of Electrical and Electronics Engineers (IEEE) predicts that Moore’s Law will end around 2025, because engineers are reaching a point where they are unable to develop chips with smaller and more numerous transistors. Other analysts argue that the end of Moore’s Law won’t be the end of progress but will instead open the door to new innovations. This includes new quantum computing designs from the likes of IBM, Google and Intel or graphene transistors that, according to research by US universities, can work 1,000 times faster than traditional silicon transistors.

If one thing’s certain, as the size of technology scales down and levels of sophistication scale up, manufacturers must produce tools with smaller, more complicated parts. This creates a growing need for producing holes smaller than three millimetres (mm) in diameter — otherwise known as micro drilling.

Difficult-to-machine materials

Micro drilling can be applied by micro component manufacturers in several industries — they include medical, general engineering, electronics, watch-making, automotive, oil and gas and aerospace. The technique is used to produce components ranging from hydraulic valves, watch cases and medical devices to surgical instruments, electrical connectors, electronics, actuators, sensors, navigational systems and more.

In response to these multiple challenges, Sandvik Coromant introduced two new micro drill families to its product range at the end of 2021: CoroDrill^® 462 with -XM geometry and CoroDrill^® 862 with -GM geometry. The new geometries offer a wide range of cutting diameters and lengths, and each tool is designed to be ideal for precision machining in industries dealing with small parts.

Not only do electronic component manufacturers face the challenges of increasing miniaturisation, but these components are often manufactured from difficult-to-machine materials like Inconel, stainless steel and titanium that must maintain the utmost component quality — flawless surface finishes for fiber optic connectors, for instance. In response to these challenges, CoroDrill^® 462 with -XM geometry and CoroDrill^® 862 with -GM geometry are designed to deliver outstanding performance with challenging materials including ISO P, M, K, N, S, O and H. The drills’ superior wear resistant properties also help manufacturers meet rising pressure to reduce manufacturing costs.

On top of the lifecycle advantages of the CoroDrill^® 862 micro drill, customers also have the option of purchasing the micro dill with a polycrystalline diamond (PCD) vein cutting edge. Based on successful tests of PCD drills on micro parts made from platinum, Sandvik Coromant has found that PCD is up to 100 times more wear resistant than solid carbide and, in addition, is more accurate and can produce tighter tolerances than solid carbide tools. Sandvik Coromant’s engineers recommend that customers seeking to drill micro-sized holes in notoriously difficult-to-machine materials, such as titanium, aluminium, glass and ceramics, should consider PCD for extended tool life in these demanding applications.

There is also the importance of coolant. As with macroscale applications, it’s critical to have quality coolant delivery to effectively evacuate chips when performing deep-hole drilling with micro tools. CoroDrill^® 462 has the capability to drill up to 6xD with external coolant, and CoroDrill^® 862 can easily drill hole depths of up to nine times diameter (xD) when using external coolant. A through-coolant option is also available for drilling diameters of 1.00 mm and above and hole depths of up to 16xD. The immediate effects of coolant are extended tool life and reduced risk of chip jamming.

Best of three

CoroDrill^® 862 was benchmarked against two other drills in a performance test. One was the previous generation CoroDrill^® R862 drill from Sandvik Coromant, and the other was a major micro drill competitor’s tool. Each tool was used in a DMG Mori Seiki Multitap 700 milling centre, for the purpose of drilling blind holes in an ISO M 316L stainless steel workpiece — a tough material that poses challenges in terms of productivity and tool life. In all three cases, the cutting diameter (Dc) was 2.5 mm (0.098 inch), speed (v_c) was 40 m/min (131 ft/min) and feed rate (f_n) of 0.04 mm/z (0.002 in/z).

The results revealed a significant improvement in tool life and number of holes drilled by the new-generation CoroDrill^® 862 micro drill, compared with the other two drills. While previous-generation CoroDrill^® 862 drilled 840 holes, and the competitor’s micro drill produced just 630 holes before showing signs of wear, the new CoroDrill^® 862 drilled 1260 holes — a 50% increase in tool life over the preceding generation, and a remarkable 100% increase in tool life over the competitor’s micro drill.

Going forward, both micro drills can support a new era for micro drilling — and help micro component manufacturers in a range of sectors facing constant innovation to ensure they always do the little things right.