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Sounding new depths with the new CoroDrill® DS20

Technology 2019-09-26 Alexander Farnsworth Stefan Estassy, Borgs

After seven years of development, the CoroDrill DS20 is set to become the benchmark for deep and high-precision drilling.

​In linguistic terms, the transformation from five to seven is no big deal. But for Sandvik Coromant, which is launching the new CoroDrill DS20 family of indexable insert drills in October 2019, the two-digit increase from 5xDC to 7xDC is a giant leap for the company and its offering.

The CoroDrill DS20 will be launched in the range of 4–7xDC and will replace the 14-year-old CoroDrill 880 4–5xDC range, which will be phased out.

The terms 5xDC and 7xDC refer to the length of the drill, which is five or seven times the diameter of the actual drill. In practice, this means that a giant steel component, ordinarily drilled from two ends with the CoroDrill 880 to accommodate long bolts and screws, can now be drilled from one side all the way through. Doing this in a single pass on a 220-pound windmill slewing ring, for example, with the precision of the CoroDrill DS20, delivers huge time and money savings for industrial customers, as the component no longer needs to be flipped over and expensive mistakes can be avoided.

​The older CoroDrill 880 family, the predecessor of the CoroDrill DS20, was launched in 2005 and soon commanded the number-one position on the market for indexable insert drills to make precision holes in metal components. CoroDrill 880 was reliable and efficient, but while numerous attempts were made to tweak the drill’s rigidity and its chip-evacuation process, it just could not be made long enough.

Håkan Carlberg, Sandvik Coromant’s senior R&D engineer for indexable drilling, explains the reasoning behind the new drill family. “We knew that the indexable insert drill market was mature and filled with competition. To grow our business, we had to look beyond the conventional. Rather than rely only on taking market share from competitors, we started looking at how we could grow the potential instead.”

​In 2012, a series of development projects on drill body material, production technology, drill body design and insert design, among many other parameters, were initiated by Sandvik Coromant to discover ways to drill up to 7xDC with an indexable insert drill. To succeed, it would have to be easy to use (plug and play), have a broad application area, be predictable and consistent, and offer increased productivity with extended tool life and high penetration rates. Many competitors had tried but failed to do this.

What ensued was a total rethinking of the geometry of the drilling process as well as the manufacturing process of the drill body and inserts themselves. To ensure the highest stiffness and rigidity possible with high process security, repeatability and consistent quality, special attention was paid to improving the chip evacuation process.
 
One of the biggest problems with elongating a drill is that it tends to bend or deflect exponentially at high speeds. Double the length and there is eight times as much deflection in the drill, resulting in imprecision. In other words, the longer the drill, the messier the result.

One challenge, according to Carlberg, was to guarantee four cutting edges on a double-sided insert and tweak the geometry of the cutting edges to balance the forces. But as Carlberg points out, the industrialization of this new concept across 256 drill body articles in total was more complex than that.

“To give an analogy of the complexity of developing the CoroDrill DS20,” Carlberg says, “imagine a mixer table with 50 knobs. With the drills, there are around 50 parameters to control and, in order to function, you need to balance all 50, as they are co-dependent. Adjust one and you have to adjust the other 49 as well.

“After having tried and developed concepts that the R&D team believed in and that showed great promise in lab testing,” Carlberg continues, “we field tested and learned that they simply were not as good as we thought. The breakthrough or pivotal moment came once we developed analysis software that simply did not leave anything to chance. All of the above-mentioned parameters could be controlled, modulated and analyzed virtually. In short, we created a program that optimizes CoroDrill DS20 drills—not as individual articles but for the entire assortment.

“We could and probably should have stopped the project many times over because the hurdles to overcome were massive,” he says. “At the same time, it is a fantastic thing to be able to break new ground and present true innovation within a product area that has been around for such a long time.”

 

 

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