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A Drill For All Materials

A Drill for All Materials

It’s said that life is a marathon, not a sprint. For automotive manufacturers, longer lasting tooling solutions are integral to more profitable production—but, often, manufacturers see little reason to change their existing tool set-up. In this article, James Thorpe, global product manager at Sandvik Coromant, explains why the benefits of longer-lasting tools shouldn’t be underestimated, particularly for reducing costs-per-part or increasing overall output.

A Drill for All Materials

Unpredictable tool life is one of the biggest threats in mass automotive production, particularly as its operations are so highly-automated and use some of the world’s most advanced robotics and automation systems. Downtime is time-consuming, disrupts production and is also expensive, so it goes without saying that tool failures should be avoided at all costs. 

In some instances, manufacturers set the tool change interval to less than the maximum tool life. This approach is normally preferred because material variations in automotive components are minimal. It follows that the tool changes should be predictable, and safer, than trying to extend the tool life to manufacture a few more components. 

Multi-material Drilling

For Sandvik Coromant’s specialists, the key to longer tool life is not limited to the amount of time a tool spends in use, but also the drill design itself. This approach led to the development of the CoroDrill 860 with enhanced -GM geometry, a new design solid carbide drill that’s optimized for a wide range of materials and applications, across all industry sectors. 

For the CoroDrill 860-GM, Sandvik Coromant applied its machine tooling and metal cutting expertise to develop a new grade, a unique fine-grained carbide substrate known as X1BM. The fine-grained carbide is imbued with increased hardness while maintaining toughness.

Furthermore, the drill is tip-coated with a multi-layer physical vapor deposition (PVD) thin film coating. This is key to improving the drill’s productivity and delivering a consistent tool life across a variety of materials. The result is a tool with excellent stability, machining security and improved tool life when machining cast iron, steel, stainless steel, hardened steels and non-ferrous metals.

Assessing Tool Life

A better way to assess tool life is by measuring the amount of material removed. To aid productivity, the CoroDrill 860-GM has an innovative, polished flute design that improves the evacuation of chips and yields greater hole quality. This also helps to reduce heat build-up in the tool, and further benefits are high core strength and reduced cutting forces while drilling.

The 860-GM forms part of Sandvik Coromant’s CoroDrill range of solid carbide drills. They are designed not only for optimized performance but also versatility, which means they can be deployed in a variety of applications and materials across multiple industries.

This includes use with the following material groups: ISO-P, the largest material group in metal cutting that ranges from unalloyed to high-alloyed material; ISO-M that includes difficult-to-cut stainless steels, austenitic steels and duplex steels; ISO-K grey, nodular and compacted graphite cast iron; ISO-H steels with a Rockwell hardness of between 45-65 HRc; and ISO-N for softer, non-ferrous materials such as aluminium, copper and brass. 

Advanced Geometry

As mentioned, the CoroDrill 860-GM has an enhanced design, but what exactly does this entail? Much of this relates to the design of the drill itself that includes an advanced optimized point and flute geometry, reinforced core and corner chamfers, edge preparation to remove cutting edge micro defects, and a double margin to enhance drilling stability. The drill’s point is also designed with refined clearance angles and improved surface quality. 

Overall, these design features stabilise the drill, reduce entry and exit burr and improve the hole tolerance, finish and straightness. The drill also gives stable wear progression and delivers excellent hole accuracy. 

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New Dimensions In Deep-Hole Drilling With Walter

New Dimensions In Deep-Hole Drilling With Walter

With the X·treme Evo solid carbide drills from the DC160 Advance range of drills, Walter is forging a link to the “next generation of drilling”. By introducing lengths of 16 to 30 × D, the tool manufacturer its expanding its range to now include deep-hole drilling. As the successor to the Alpha 4XD drills which have been established on the market for a long time now, the DC160 Advance, like its predecessor, makes deep-hole drilling possible in a single operation without pecking – and therefore boasts the advantages of XD Technology. The coating and geometry have been optimised. Just like the existing versions of the DC160 Advance, the deep-hole drills also feature the innovative new thinner web with 140 deg point angle and the fourth land in an advanced position. The former ensures increased positioning accuracy and reduced cutting forces in the centre, while the latter optimises the guidance of the drill.

The grades of the drills (WJ30ET and WJ30EU) are another new addition. These comprise the K30F fine-grained substrate and a TiSiAlCrN/AlTiN multi-layer coating (as a point or complete coating). The layer structure makes the drills both tough and wear-resistant and plays a crucial part in the process reliability and performance of the DC160 Advance drills. Polished flutes from 8 × Dc also optimise chip evacuation. Typical application areas of the drills, which are available with or without (internal) cooling, include general mechanical engineering, mould and die making, and the energy and automotive industries. Walter offers intermediate sizes and special dimensions via its Xpress service with faster delivery times.

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Cutting Tools That Cut Out Vibrations

Cutting Tools That Cut Out Vibrations

How to say no to vibrations in machining? Find out more in this article by Andrei Petrilin, Technical Manager at ISCAR.

Figure 2: The FINISHRED series of solid carbide endmills features chip-splitting geometry coupled with variable pitch flutes.

Vibrations in machining are generally an unavoidable part of the metal cutting process. They have a forced or self-excited nature and always accompany a cutting action. Machining vibrations are referred to as “chatter,” highlighting their specific nature, which inheres in every processing where chips are formed. Even if cutting is considered as stable, it does not mean that vibrations do not take place. In this case, the vibrations simply remain on a level that provides the required machining results, and is considered as a “no vibration” operation.

READ: Machining for the Aerospace Industry

In fact, vibrations in cutting are a damaging factor that reduces performance. Manufacturers make every effort to diminish vibration and, ideally, bring them to a level that does not affect machining results. Chatter is a subject of serious research that has already provided manufacturers with ways to model vibrations in machining which, despite their complexity, can be very effective in finding a way to reduce chatter. However, this modelling takes time and requires various input data, including sometimes additional measurements. In most cases, when manufacturers face vibrations during machining, they only have a few tools at their disposal for a real-time response to decrease the chatter. The most common practice is to vary cutting speed and feed, which usually leads to productivity reduction. Therefore, any effective method of diminishing vibrations that does not adversely affect machining operation productivity will be attractive to manufacturers.

Vibration reduction in machining requires consideration of a manufacturing unit as a system comprising the following interrelated elements: a machine, a workpiece, a work-holding device, and a cutting tool. While the influence of each element on total vibration reduction is different, improving a vibration characteristic of one element may have a significant impact on the system’s overall dynamic behaviour. Most efforts to protect against vibrations focus on developing more rigid machines with intelligent sensors and computer control, and advanced vibration-dampening tooling. Can a cutting tool, the smallest – and probably the simplest – system component, dramatically change the vibration strength of a manufacturing unit? Even though producers might not have great hopes for the role of cutting tools in decreasing chatter, in certain cases a correctly selected tool can simply stop vibration without any adverse effect on productivity.

Cutting Geometry

Figure 3: The SUMOCHAM-IQ family of HCP exchangeable carbide heads.

The right tool geometry makes cutting action smooth and stable. The geometry strongly influences cutting force fluctuations, chip evacuation and other factors, which are connected directly with vibration modes. ISCAR’s tool design engineers believe that the cutting geometry can considerably strengthen vibration dampening of a tool and have developed interesting solutions accordingly.

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ISCAR’s various indexable inserts, exchangeable heads, and solid carbide tools feature chip-splitting cutting edges. Such an edge may be serrated or have chip-splitting grooves. The chip splitting action causes a wide chip to be divided into small segments, resulting in better dynamic behaviour of a tool during machining, and vibration is stabilised. In rough machining, extended flute milling cutters remove a large material stock and work in heavy conditions. Significant cutting forces acting cyclically generate vibration problems. When using chip-splitting indexable inserts, it is possible to tackle these difficulties. Mills with round inserts, a real workhorse in machining cavities and pockets, particularly in die and mold making, are often operated at high overhang that affects rigidity and vibration resistance of a tool. Problems with cutting stability occur when the overhang already exceeds 3 tool diameters. Applying serrated round inserts with a chip-splitting effect redresses this situation and substantially improves robustness (Figure 1).

A skilfully defined tooth pitch is an effective way of taking the dynamic behaviour of a cutting tool to the next level. ISCAR’s CHATTERFREE family of solid carbide endmills (SCEM) was designed on the basis of a pitch control method. The family features a variable angle pitch in combination with a different helix angle. This concept ensures chatter free milling in a broad range of applications.

The FINISHRED series of solid carbide endmills features chip-splitting geometry coupled with variable pitch flutes (Figure 2) that provide surface finish when machined according to rough machining data.

The principles of vibration-proof cutting geometry, which demonstrated their effectiveness in solid carbide endmills , have been applied to the design of exchangeable multi-flute milling heads made from cemented carbides in the MULTI-MASTER family.

Chatter-Free Drilling

Figure 4: ISCAR’s ISOTURN WHISPERLINE family of anti-vibration cylindrical bars.

Chatter in drilling leads to poor surface finish and accuracy problems. In ISCAR’s SUMOCHAM family of assembled drills with exchangeable carbide heads, the double margin design of QCP/ICP-2M heads substantially increases tool dynamic stability. 

READ: Iscar F3S Chipformer For Finish Turning On Superalloys And Exotic Materials

If vibration occurs when a drill enters material, it may cause serious damage and even breakage of the drill. The SUMOCHAM-IQ family of HCP exchangeable carbide heads (Figure 3), intended for mounting in the bodies of standard SUMOCHAM tools, can ensure reliable self-centring capabilities. The key is an unusual concave profile for the head cutting edge reminiscent of a pagoda shape. This original cutting geometry enables high-quality drilling holes of depths of up to twelve hole diameters, directly into solid material without pre-drilling a pilot hole.

The “magic pagoda” features another ISCAR innovation: the LOGIQ3CHAM family of latest-generation drills carrying exchangeable carbide heads with 3 teeth to ensure higher productivity. The steel drill bodies have 3 helical flute that weaken the body structure when compared with a 2-flute assembled drill of the same diameter. In order to improve the dynamic rigidity, the flute helix angle is variable. This design principle in combination with the pagoda-shaped cutting edge provides a durable chatter-proof solution for stable high-efficiency drilling.

Tool Body Material

An assembled cutting tool comprises a body with mounted cutting elements such as indexable inserts or exchangeable heads. Choosing the right body material presents an additional option for forming a chatter-free tool structure. Most tool bodies are made from high-quality tool steel grades, for which the material stress-strain behavior is similar. However, in some cases tool design engineers have identified successful material alternatives to improve vibration strength.

READ: ISCAR CTO Stresses On Productivity Improvement

The MULTI-MASTER, an ISCAR family of rotating tools with exchangeable heads, provides a range of tool bodies, referred to as shanks, produced from steel, tungsten carbide or heavy metal. A steel shank is the most versatile. Tungsten carbide with its substantial Young’s modulus provides an extremely rigid design, so carbide shanks are used mainly when milling at high overhang and machining internal circumferential grooves. Heavy metal, an alloy containing around 90 percent tungsten, is characterised by its vibration-absorbing properties, and heavy metal shanks are most advantageous for light to medium cutting operations in unstable conditions.

Anti-vibration Tools for Deep Turning

A typical tool for internal turning or boring operations comprises a boring bar with a mounted insert or a cartridge carrying an insert. The bar is the main factor in the dynamic behaviour of a tool. Stiffness of a bar is the function of the bar overhang to diameter ratio, and large ratios may be a reason of tool deflection and vibrations, affecting dimensional accuracy and surface finish during machining.

ISCAR has developed three types of boring bar to cover a wide range of boring applications: two integral (from steel and solid carbide) and one assembled, having a vibration dampening system inside.

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The steel bars enable stable machining with the overhang up to four diameters. Exceeding this value can induce vibrations due to steel’s elasticity characteristics. Changing the bar material from steel to a more rigid solid carbide ensures efficient vibration-free boring with the overhang of up to seven diameters. However, further increasing the boring depth is also limited by the material stress-strain behaviour. In order to clear this overhang barrier, ISCAR developed the ISOTURN WHISPERLINE family of anti-vibration cylindrical bars. The bars carry interchangeable boring heads for indexable inserts of different geometries and have inner coolant supply capability. The main element of the bar design is a built-in vibration-dampening mechanism to provide “live” vibration damping during machining. This enables effective boring with the overhang from seven to 14 diameters (Figure 4).

A vibration-dampening unit is used also in ISCAR deep grooving and parting tools. The unit is in a tool blade under the insert pocket. Each blade is pre-calibrated by ISCAR for optimal performance for a wide range of overhangs, but end-users can complete fine tuning calibration themselves if needed.

Cutting tool manufacturers have a limited choice of means in the abatement of machining vibrations, with only tool cutting geometry, tool body material, and maybe a cutting tool with built-in vibration-damping device at their disposition. Considerable skill and ingenuity are required to make a chatter-free tool with these limited resources. It is feasible, however, and ISCAR’s solutions highlighted in the above examples affirm the possibilities.

 

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Walter: Carbide Drilling Tools

Walter: Carbide Drilling Tools

Walter has developed the DC170 and is offering the first two models in dimensions 16xDc and 20xDc. The drill offers more process reliability, stability, running smoothness and efficiency than carbide drills with traditional geometries.

The drills are internally cooled. As a result, the coolant flows unimpeded, while hazardous chip jams are at the same time avoided. The manufacturer also says that the solid carbide mass directly behind the cutting edge makes the drill sturdy.

Finally, drills straight from the factory are supplied with eight visible channels that can be used as a scale for regrinding. The drills can be reconditioned up to three times, until only two cooling channels are left remaining.

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