Iscar’s recently launched Logiq campaign introduced new families of cutting tools targeted to address challenges in metalworking, from increasing efficiency and developing cost-beneficial small-size tool solutions to reducing machining vibrations. One of the issues confronting Iscar’s specialists was how to increase productivity in drilling? Although a traditional approach, based solely on advanced cutting geometry and progressive tool materials, can result in some improvements in productivity, it is still far from a dramatic change. A significant breakthrough calls for another concept.
The development of the Logiq3Cham family of drills with exchangeable heads offers a solution to this challenge (Fig 1). The drills feature heads with three flutes instead two, which is the standard number in a drill design. As a result, machining cycle times can be reduced by up to 50% when compared to the conventional two-flute drills. The idea looks logical and simple – more flutes means more feed speed, which leads to higher productivity. However, a translation of this idea into action is not as easy as it may seem. Iscar’s engineers had to solve several complex tasks in order to design a robust and reliable three-flute drill.
An increase in metal removal rates leads to a subsequent growth in cutting forces. This means that the drill’s chisel point must be capable of withstanding high cutting forces. To ensure a stable drilling process, the drill should enable good centring and a smooth penetration into the material. When compared to a two-flute drill, a three-flute drill of the same nominal diameter generates a smaller flute area for chip evacuation (Fig 2). Therefore, another important design requirement for the new drill is to enable efficient chip formation and unconstrained chip flow.
An additional method of improving productivity can be found by decreasing non-productive machine time. This can be achieved by significantly reducing the time lost in replacing a worn drill.
Development of the Logiq3Cham line offers a good example of how to find and implement effective solutions for these challenges.
The cutting element of a Logiq3Cham drill is a three-flute exchangeable head H3P, made from cemented carbide. The head, which features a durable and precise chisel point combined with an appropriate gash angle, successfully stands against a heavy cutting load. Iscar’s latest research and development projects for high-performance two-flute drills brought an unusual concave shape of cutting edges. The resemblance of the shape to a pagoda profile even generated the shoptalk term, a pagoda edge. The concave cutting edges result in smooth and stable drilling. Following the logic of this successful design, the pagoda shape was integrated into the new three-flute head.
In the Logiq3Cham drills, the concave shape of the head edge significantly contributes to generating the optimal chip form and makes chip evacuation process easy. In addition, the 15° corner chamfer improves wear resistance and strengthens the head cutting corner. A dovetail clamping concept prevents the head from being extracted from its pocket in a drill body during retraction. The head clamping method, which provides face contact between a head and a drill body, ensures the realisation of the no setup time principle that already characterises several Iscar tool families. According to this principle, replacing a worn head does not require any additional setup procedure and may be done when a drill is mounted in a machine tool spindle. This capability significantly decreases the unproductive time component in a cycle time.
A Logiq3Cham drill body that carries an H3P head has its own specific features. In designing the drill body, Iscar’s tool engineers faced some difficulties caused by the three-flute concept. The growth in metal removal rate necessitated a proportionate increase in flute volume to ensure an unconstrained chip flow. However, this was shown to reduce body strength and stiffness when compared with a two-flute design of the same diameter and therefore a non-standard solution was required. Finite element modelling assisted in identifying a solution, a variable flute helix angle, which provides a durable body structure to resist a high axial load and improve the body’s dynamic rigidity. A helical margin prevents chip adhesion between the body and the drilled hole.
The head pocket enables a large face contact surface, which spreads out the pressure during machining. The pocket is designed to avoid plastic deformation and increase heat resistance, so prolonging pocket tool life even in difficult conditions.
Iscar’s Logiq approach has combined the advantages of a pagoda-shaped cutting edge, reliable head clamping method, and a specially designed drill body with its ‘no setup time’ concept to provide an extremely efficient tool for high-performance drilling in a diameter range of 12mm to 25.9mm (Fig 3).
For further details contact Iscar South Africa on TEL: 011 997 2700 or visit www.iscar.com