High-performance titanium drilling, in one shot
Press release, September 2022, Mikron Switzerland AG, Divison Tool
Titanium is a high-performance material and poses a chip removing machining challenge. Also, not all titanium is alike. Depending on whether it is pure titanium or alloyed titanium, the chip removing process behaviour differs. Mikron Tool has come up with different drill series that are perfectly tailored to the various titanium grades allowing to machine them safely with higher cutting performance results and longer tool life.
Drilling into stubborn titanium is exceptionally challenging, partly because the combination of high elasticity and tensile strength properties. The great toughness of this metal means that chip breaking is difficult to achieve. Due to the lower thermal conductivity, heat is not moved from the cutting area through the chip; but still needs to get rid of somehow. Also, titanium has a propensity to create edge built-up which in turn can lead to higher levels of wear and reduce process reliability when drilling. Mikron Tool specializes in developing drilling technologies that are perfectly tailored to the material properties of pure titanium and titanium alloys. This is a complex task but then offers enormous production benefits for users.
Titanium: “Like drilling into rubber”
“It’s like drilling into rubber”, says Alberto Gotti, Head of R&D at Mikron Tool. “Drilling titanium is much more challenging than milling; and it is even more difficult when the diameter-drilling depth ratio increases“. It becomes problematic above 3 x d. Titanium’s viscoelastic properties cause the drill to jam, which increases the pressure on the cutting edges. Material build-up on the cutting edges and margins increases the cutting forces which, in turn, can cause cutting edge breakout. Once the surface is compromised, even more material will build up and lead to higher friction. Also, the chip shape becomes problematic because the titanium chips tend to accumulate in the tip area and prevent smooth flowing of chips. In turn, this often leads to uncontrolled drill breakage. A further compounding factor are the high temperatures to which edges are exposed. From a temperature of 600° Celsius, the cobalt binding matrix in the carbide substrate becomes ‘soft’ and is no longer able to bind the hard tungsten carbide optimally. That leads to plastic deformation and micro-wear, and ultimately cutting-edge breakouts.
Material-specific tools are the solution
One remedy are cutting edges which need to be very sharp and very stable at the same time – a contradiction in itself. Mikron Tool has developed an ingenious specific cutting geometry that manages this balancing act and, as a result, cutting pressures can be reduced significantly. As described above, the heat needs to be moved from the machining area. The solution: two cooling channels with very large cross-sections deliver large quantities of coolant through to the drill tip to guarantees constant cooling, including lubrication of the cutting edges. At the same time, the solid coolant jet flushes the chips through the polished flutes and prevents jamming chip backup.
There is nothing new here, but: the patented special design of the cooling channels by Mikron Tool allows 4 times the amount of coolant quantity to be shot into the tool with constant pressure.
This is a further key to success and stands for innovation in the thermal dissipation and chip removal technology.
Also, the flute profile helps significantly with the chip removal. But that’s not all: the R&D specialists focused on a carbide grade that combines wear resistance and fracture resistance strength. The coating is distinguished by its excellent wear and oxidization resistance, and as an additional benefit diminishes the tendency of material sticking.
“Not all titanium is alike”, says Markus Schnyder, COO of Mikron Tool. “Anyone who wants to process this material efficiently needs to know it inside out. During our development work, we examined various titanium materials and established that the different titanium types differ greatly; this is highly relevant for the way it is machined in industrial production. Pure titanium (Grade 1–4) stands out due to its high corrosion resistance, while it has lower mechanical strength”.
The right drill for each grade of titanium
Markus Schnyder: “Alloyed titanium (grade 5 and higher) is incredibly strong but has low ductility. We worked like crazy to master these differences with chip removal technology. Three years of meticulous development work lie behind us. Our passion and the insights we gained have led us to a perfect solution: two specific geometries, one for pure titanium grades and one for titanium alloys. Thus, we can guarantee perfectly controlled chip removal, high drilling speeds and precisely repetitive processes with optimum machining quality for these difficult titanium materials. The right and specific drill for each titanium grade. This is our answer for handling this complex and ‘divine’ material”.
Crazy Drill Cool Titanium – Twice as fast
The new Crazy Drill Cool Titanium series is available in a diameter range of 1.00 to 6.35 mm (.04″–.250″). Mikron Tool has developed short drills with 3 x d and drills with 6 x d for pure titanium (CrazyDrill Cool Titanium PTC) and drills with 6 x d and 10 x d in combination with a special pilot drill for titanium alloys (CrazyDrill Cool Titanium ATC).
For the cost-effective production of titanium components, tools are required which are specially adapted to the material properties of the various titanium grades.
Titanium material as well as the workpiece are expensive, which is why high process reliability and calculable tool live are so important. If the latter can be improved, so much the better. Mikron Tool’s new high-performance drills for titanium have up to 3 times longer tool life and work with twice the feed than current competitors. Another outstanding aspect: With the ATC-version drilling is completed in one shot, without multiple machining steps.
The result is impressive and proves, once again, that Mikron Tool is a technological leader and will defend its position by machining difficult materials successfully. “We love getting the best out of our tools for our customers. Nothing is too ‘crazy’ for us”, says Alberto Gotti.
INFORMATION BOX TITANIUM:
Titanium is by no means rare; in fact, it is the 9th most common element in the continental crust. However, pure titanium is rarely found on earth, it is produced from titanium ore or rutile. Today, we still use a procedure that was developed by William Justin Kroll, a metallurgist from Luxemburg, in 1930 for the complex production of titanium: it became possible to produce the metal for commercial applications thanks to the introduction of the industrial reduction of titanium (IV)-chloride with magnesium. The production process used here is extremely complex, as reflected by the very high price for titanium. Some call titanium a temperamental diva that screams when treated incorrectly. Titanium developed into an ultra-material for the industry due to its excellent properties. The application horizon is broad: aerospace, motor racing, medical and dental equipment, surgical orthopaedics, and the jewellery and watch sectors all use it. Titanium is also ideal for eyeglass frames. In short, this metal is very popular in industry thanks to the broad market base. 330.000 sh tn are processed every year. Titanium’s supernatural image is the reason for this figure.
Rightly so because it is indestructible. It hardly weathers when it encounters oxygen because it is coated in a thin, transparent oxide layer. Even the most aggressive media, like acids, have very little impact on titanium. It is almost as light as aluminium, but much stronger, almost on a par with tempered steel. It is also biocompatible and anti-magnetic.
Mikron Switzerland AG, Division Tool
Via Campagna 1
CH-6982 Agno
Tel. +491 91 610 4000
mto@mikron.com
www.mikrontool.com