Deeper, faster, more productive

When Sandvik Coromant approached SKF’s production plant in Monterrey, Mexico, to invite the company to take part in trials of a new CoroDrill DS20 4-7xD (40 to 70 millimetres long x diameter) drill that was seven years in the making, the customer leaped at the opportunity. SKF already had a successful track record with Sandvik Coromant that had enabled it to reduce the time spent in completing a gear-cutting process to 50 minutes from the original eight hours. In addition, the company was facing the realities of competing in a market marked by falling prices and increasing product complexity. A solution was urgently needed to reduce costs and increase speed in the drilling process.

The product in question was a wind turbine bearing with a diameter of three metres. Producing this bearing required specialised machining centres in which two machines drill holes simultaneously with depths from 39 millimetres to 231 millimetres on a 42CrMo4 ring, up to a total of 92 holes.

Although the parts were produced using special custom-made 6-7xD drills, the tool length made the process more unstable, and production was frequently interrupted by broken inserts. David Gutiérrez, the production engineer responsible for the process, had to battle the uncertainty of never knowing how long the inserts were going to last, slow drilling rates of 102 millimetres and continual halts to prevent damage to the tool, the machine or the workpiece.

For the plant’s engineering manager, Valdemar Garza, there were also the economic aspects to worry about. “We’re talking about very expensive parts because of their size,” he says. “We had to monitor the tool very carefully to prevent it or the workpiece from suffering any damage. So we were looking for more efficient, faster options that could give us the best cost per part.”

In 2017 Sandvik Coromant’s drilling experts came up with the solution – the CoroDrill DS20 7xD drill expectations were high, and not just for the reliability, speed and consistency promised by the new tool. Because it was a catalogue product, it would be cheaper than ordering special drills, and it would also improve the company’s stock management.

The results spoke for themselves. The first test, carried out on scrap, was successfully completed with a diameter of 36 millimetres. For the following tests, carried out on production parts, the cutting conditions were intensified and the diameter was increased to 39 millimetres, with clear improvements in terms of tool life and a resulting increase in productivity.

In total, explains Arely Sánchez, the Sandvik Coromant drill specialist who provided field support for the process, three tests were performed. In real data, they showed a 100 percent increase in the tool’s service life (compared with the special drill that SKF was using) and a 98 percent increase in productivity, calculated as the ratio between the quantity of material removed and the time taken to produce each part.

“This means high cutting conditions, few tool changes and a longer life,” says Sánchez. “With this level of productivity, we can make more components per day or year.”

Gutiérrez explains that the tests started at feed rates of 114 millimetres per minute, but after making several adjustments, they were able to achieve up to 198 millimetres per minute.

In May 2019, SKF received 10 drill bodies, 300 centre inserts and 300 peripheral inserts for what is known as a long test. Since then, the CoroDrill DS20 7xD has had a significant impact on production. The drills can drill all 92 holes of the ring without needing to change the inserts (although SKF still changes inserts as a precautionary measure because they operate at twice the feed rate), and the drilling capacity has already reached four parts per shift, or 12 a day. This has been their highest production capacity since the company has been using Sandvik Coromant drills.

Garza comments, “The advantage of this tool, and what makes it particularly interesting for us, is that as well as giving us the opportunity to increase our cutting speed and reduce the cycle time [to half the previous cycle time], its cost is as if it were a tool from a previous generation. In this case, with the CoroDrill DS20 7xD, we have the speed of the latest tools but the cost of previous tools.”

SKF are so satisfied with the results that they are waiting for the product to be included in the catalogue to assess what other applications the company can trial it in. In addition to all the benefits mentioned earlier for the drilling process, Garza highlights the machines’ increased capacity and the ability that the company now has to schedule machine maintenance and cover operator vacations without having to use overtime. “This drill gave us flexibility to use the resource in different ways without having to depend on the product’s output or having the machine operating non-stop,” he says.

About SKF

Founded in 1907, the SKF Group operates in more than 130 countries and has more than 100 production centres, including SKF Mexico. The company offers products and solutions to all branches of industry through its business platforms: bearings, seals, lubrication systems, mechatronics and services.

In Mexico, SKF has been marketing its products and services since 1920. At present, it has more than 1,500 employees and five factories (three that manufacture seals and bearings for automotive customers, and two for industrial clients). In Mexico, the company specialises mostly in manufacturing bearings for industrial and heavy equipment used in various industry segments, including wind power generation.