Dr. Tibor Cselle Guhring Inc.
Edited by Patricia L. Smith


In the coming years, manufacturers will face many new challenges in terms of machinability. Obviously, tool life and productivity will continue to be paramount concerns as these firms work with new materials and new methods of machining. For these reasons, technologies such as dry, high speed machining, new tool coatings, and minimum lubrication systems will become even more popular. In addition, users can expect that methods of tool purchase and management will change.

It is always hard to predict the future, but as companies strive to significantly lower holemaking costs, one of the most important factors influencing tooling development will be workpiece material. For example, in the automotive industry, aluminum alloys will likely play a dominant role. The aerospace industry too, will be using aluminum as well as nickel and titanium alloys. Other materials to keep an eye on are composite cast iron and magnesium.

But how will tooling change? One safe bet is that developments will center around three little words: hard, dry, and fast. Dry machining, in fact, will continue to be a major focus over the next several years, especially in Europe.

Without going into too much detail, let's review the "The 10 commandments of dry, high speed machining" as listed in American Machinist, May 1998, p. 66. These guidelines can help companies make the most efficient and economical use of dry machining.

1. Dry holemaking for total success
2. Honed cutting edges to lower cutting temperatures
3. Multilayer hard coatings for optimum thermal protection
4. Integrated soft coating to fight edge buildup and increase tool life
5. External mist lubrication for machining economy and flexibility
6. Internal mist lubrication to maximize productivity
7. Custom tool geometries for reducing cutting friction
8. Suction systems to evacuate mist, fumes, and chips
9. New machine concepts for fast, effective hot chip removal
10. Faster, not slower, cutting rates to improve tool life and control heat.

The last item is probably the most important, because widespread use of dry machining techniques hinges on improving productivity. Although no one can tell how quickly this technology will spread, some automotive manufacturers have already mandated that dry machining be used in all feasible operations. If not possible, these automakers check first on the applicability of mist lubrication and then immersed machining. If all else fails, and a flood coolant must be used, water-based coolants are preferred over straight oils.

Trends in tooling

As companies move toward dry machining, they will strive to replace high- pressure coolant with soft glide coatings and mist lubrication. Both technologies aim to reduce friction between the tool and the workpiece and avoid built-up edges.

Traditionally, soft coatings show the greatest potential when used in combination with hard coatings. In the area of soft coatings, three major directions of development are expected.

First, new deposition technologies will lead to the coating of carbides, steels, and even aluminum, lowering the coefficient of friction. Previously, rough surfaces and cobalt content made the coating of these materials difficult.

Secondly, the development of extremely soft coatings will continue. Available primarily on a MoS2 basis, these soft coatings improve the entry behavior of tools.

Third, users will see glide coatings of a "middle" hardness, for example WC/C, which have higher friction levels at entry but also higher abrasion resistance than the MoS₂ coatings.

As for mist lubrication, it has substantial advantages over full coolant, including better lubrication effects and avoidance of thermoshock. In addition, it uses around 60,0003 less oil and keeps chips and workpieces dry. When used in combination with chip and steam suction, the process fully protects both the environment and worker health. One might wonder if soft glide coatings are still necessary with all the advantages of mist lubrication. The answer is yes, especially in emergency situations when the minimal lubrication cannot reach the important parts of the tool.

Another market change is a move away from HSS and brazed PCD tooling to various carbide grades. The old dogma that P-grades were for steel and K-grades were for cast iron and aluminum is gone. In fact, the only reason for the existence of P-grades are the small advantages offered when machining steel after regrinding without recoating. However, coated, ultra-fine-grain carbides are even more advantageous. The extremely high toughness of these carbides means that HSS tools can be replaced even in unstable and critical environments.

Combining high toughness and hardness is now possible using nanograin carbides. But, because they are still exorbitantly expensive, multiple grade carbide blanks, which provide a tough core surrounded by a finer, harder grade, may be used instead. Multiple grade carbide blanks are a good solution for tools with edges on a constant radius, like reamers and end mills. But with tools that have radial edges, like drills and cone end mills, hardness and cutting behavior would change too much, and chisel edge wear would occur too quickly. Here, cutting tool manufacturers are exploring techniques like electrophoretic deposition (EPD) to encapsulate the carbide substrate in ceramic. This process provides greater control over the final toughness-hardness ratio. Additionally, it can be used to deposit diamond as the last surface layer, offering a much more cost-effective, reliable option to PCD brazing when working with complex-shaped tooling.

Refinements to deposition technologies used to lay down multilayer coatings is another trend expected to change tooling. These refinements will bring about an enormous gain in productivity, especially when compared to TiN and other PVD coatings.

Properly applied, superlattice nanolayer coatings feature far superior hardness and wear resistance, delivering significant gains in both machining speed and tool life. The key lies in reducing the size and number of coating droplets formed during the deposition process. Within nanolayers, droplets can create an uneven surface, reducing coating lubricity, or glide factor.

Minimizing droplet formation requires ultra-precise synchronizing of electronic ignition control and tool rotation within a coating chamber. This can only be done when coating a large number of tools all with the same geometry. At a coating service company, where habit and market demand typically dictate filling machines with mixed loads, this is currently not possible. This, coupled with the technical challenge of effectively stripping multilayer coatings back down to the substrate before recoating, will ensure that good old, smooth, easy-to-recoat TiN will not go away for the foreseeable future.

One promising new coating technology is plasma ion implantation (PII). This process increases the hardness of a tool without changing its dimensions, which can be crucial for fine cutting tools. PII technology effectively forms a lattice structure by "shooting in" metal ions, growing roots into a tooling substrate. Finally, tooling will adapt to be self-adjusting and intelligent. Although measuring and self-adjusting toolholders (actorics) in agile machining centers have made the rounds, measuring, computing, and drive technology is new. The following are showing great promise in tooling applications: µGPS. Using satellites, Global Positioning Systems (GPS) precisely determine a position on the earth's surface. The same principle, when used on machining centers, is called «GPS. This technology has become necessary with the increasing popularity of hexapod machines, where measuring through the axes is extremely difficult. Actorics. Used in tools and machines, actorics use wireless connections for transmitting commands to compensate for tooling size deviations. These devices are able to detect the end of tool life automatically. Intelligent coatings. When worn, deformed, or exposed to high temperatures, these coatings' electric resistance changes, emitting an electronic signal that can be read by a machine tool.

Adaptive balancers. Employing gels and piezo crystals, these units cancel out imbalances and reduce chatter and vibration.
 

Tool selection and management

Tooling technologies will not be the only things changing the shop floor. In addition, users will have more tool selection, management, and procurement options.

For example, there now is a choice between solid carbide and interchangeable-insert carbide tooling. While solid carbide drills will continue to dominate the lower diameter ranges (below 16 mm), the trend seems to be going towards interchangeable-insert tooling for large-diameter holemaking.

While this has long been the domain of spade drills and carbide-tipped brazed tooling, new tool designs marry the convenience and cost-effectiveness of a disposable insert with high performance cutting geometries. Whereas the straight, "Plain Jane," cutting edge of spade drills fractures and must be "pushed through" materials, new tool designs feature high performance points that cut and pull themselves through the workpiece, delivering high feedrates, longer tool life, reduced heat generation, and lower required torque and horsepower. The trend toward outsourcing tool management is likely to continue. The key will be to delegate responsibility to the right partner, balancing the desire for lower administrative, purchase, and carrying costs against the need for quality product and value-added engineering support and problem solving. In-plant tool crib management will evolve with the introduction of advanced automated tool vending machines, which will greatly improve tool-use tracking, analysis, and forecasting. Finally, the Internet will change distribution systems.

Today, the tool industry primarily uses the Internet to advertise its products. A few catalogs are on-line, but tooling sales have not really started. But the Internet will not stop at the desk of the purchasing agent or the tool planner. Soon, machine operators will be able to download cutting data, just like they will be able to perform simple cutting tool troubleshooting.

Buckley Owens Machinery Corp. 6416 Fly Road | East Syracuse, New York 13057 Telephone 315.432.0708 Fax 315.432.0736 Email: info@buckleyowens.com