Trends in Cutting Tools’ Development
Posted : September 28, 2004 at 6:52 pm [IST]
The reasons behind cutting tool developments are better manufacturing productivity, improved accuracy, and quality. One of the main trends influencing cutting tool design is developing cutting tools for small-part manufacturing, such as those for the medical industry, which is seeing a phenomenal growth annually.
Another important thrust is for the tools that can meet multitasking requirements.. The industry needs longer, yet rigid tools that can reach into limited spaces.
New Materials
There is an increased emphasis on the uses of titanium and titanium alloys.
The auto industry is going for more aluminum-silicon alloys as well as some magnesium,
The industry is also showing increasing interest in compacted graphite iron [CGI]- a variant of ductile iron. Though the tools that work well on ductile iron can, in general, do the job on CGI as well, but the absolute tool life is likely to be less when cutting CGI because of its abrasiveness and higher yield strength. Flank wear resistance is particularly important with this metal.
Among the trends:
” The nickel-based alloys are becoming more difficult to machine.
” Whisker ceramics and improved Sialons continue to be used.
” Sialons have extended the property range and toughness.
” Titanium/aluminum (TiAl) coatings have improved for cutting stainless, regular steels, and cast irons. This is because PVD technology has improved coating adhesion.
TiAlN coatings have better adhesion, and for cutting aluminum give better chemical stability and they dissolve more slowly in ferrous materials, and have higher hardness levels. As a result, tool life is longer and cutting speeds are higher.
Coatings have made major improvements. Majority of tools are coated. For the greatest portion PVD is used. At the same time there has been a surprisingly rapid development of CVD technology, chiefly improvements in adhesion to substrates and between layers. There have also been improvements in coating smoothness and thickness. Turning-tool coatings are now more than 20 µm and milling tools are up to 7µm.
There is now greater use of substrates with cobalt content less than 6%. They are used in high-volume ferrous machining applications. This reflects the trend in machining to higher speeds, smaller DOC, and fewer interrupted cuts.
There is a clear trend away from HSS to cemented carbide in end mills because new machining centers with higher speeds are stiffer and need more wear resistant tools. Milling is an area where big improvements in indexable end mills have been made. A new system called Mill 1- offers better surface finish, while requiring less power and lower cutting forces. The perpendicularity is now close to a true 90º, and it has good ramping capabilities.
Another innovation is the insert screw is mounted at an angle, instead of the traditional perpendicular mount. This has two advantages. It pulls the insert into the holder more tightly and has more screw threads engaging the holder. As a result cutting speeds can be higher.
In the last two years, there has been a lot of growth in applications of lightweight nonferrous materials as well as hardened steel and other difficult-to-machine ferrous materials. As a result, the market has significantly increased for custom-engineered round tools with brazed cutting edges of PCD or PCBN for milling, drilling, and reaming operations. Custom round tools with fixed cutting edges are intended for machining parts with small-diameter holes of approximately 0.25″ [13 - mm] diameter where the restricted space is a problem for insert-type cutting tools. They also apply for parts with relatively tight tolerances in the range of 3 - 5 µin. [0.002 µm] because of the possibility of cutting-edge movement with inserted-type cutting tools.
Ways are being found to cut deliveries of round tools by half or more by automating the process. Using the new software, standard delivery for high-precision custom round tools is 10 weeks, and in some cases as little as four weeks.
Our industry moves ahead relatively slowly, with cutting tool development usually ahead of machine tool performance. However, currently 70,000 rpm is achievable on the machine and spindle end, but at this time the inserts won’t hold up. Aerospace is where we most often see new alloys being used, then it falls on the cutting tool makers to develop products that will work Recently there have been some advances in diamond tooling.
Iinsert grades for turning steels and stainless steels are being designed for dry machining through a combination of wear resistance and edge toughness. Getting rid of coolant can extend tool life. New inserts offer reliability and improved surface finishes in medium-duty turning of steels because its toughness resists chipping. The inserts combine superior core toughness, high wear resistance and sophisticated chipbreaker geometries, and are especially designed to withstand heavy roughing, interrupted cuts, high-feed applications and processes on materials with high piece-to-piece or batch-to-batch variability.
A new line of indexable insert drills have a combination of features that allow drilling with much faster speeds and feeds even on applications with long overhangs, workpieces with poor fixturing, and thin-walled parts. The entire drilling line, which covers a range of 0.594 - 2.375″ [6 - 60-mm] diam and drilling depth capabilities from 2XD to 5XD, uses square inserts with 90º corners. The drill body resists deflection and evacuates chips. Plus, the drills have a non-stick coating that further enhances performance and drill life.
Tools are being developed to meet the industry’s requirement of lean manufacturing.
- Indra
Category: Machining |
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