Lesson 52 of
Industrial Engineering ONLINE Course
Lesson 9 of
Process Industrial Engineering ONLINE Course (Module)
When Taylor started his productivity improvement studies and research, only carbon steel is the tool material. Taylor, developed high speed steel and did number of experiments to find the maximum cutting speed, feed and depth of cut combinations for various machining jobs. This productivity improvement of machining by Taylor is the foundation for industrial engineering. Industrial engineering is engineering with productivity focus.
In the area of cutting tools, number of new materials were discovered and invented increasing the cutting speed, feed and depth of cut combinations to give very high material removal rate. Industrial engineers have to know the application of each tool materials and its best use in a machining job. They need industrial engineering knowledge base to guide them in this area of productivity improvement. They need to examine productivity aspect of each and every cutting tool element and develop ways to use the productivity potential in their process plans. Some aspects are covered in this note at the moment. They will be updated.
Cutting-Tool Materials
High-Speed Steel (HSS) and Related Materials
Sintered Tungsten Carbide (WC).
Cermets
Ceramics
Polycrystalline Tools
Polycrystalline Cubic Boron Nitride (PCBN)
Polycrystalline Diamond (PCD)
Tool Coatings
Coating Methods
Conventional Coating Materials
Diamond and CBN Coatings
Tool Geometry
Cutting Tool Materials
Ceramics - Ceramic Tools
Ceramic cutting tools can be divided into four categories
1. Alumina and Alumina mixed with zirconium oxide
2. Alumina-titanium carbide composites
3. Reaction-bonded silicon nitride (Si3N4, RB)
Si3N4 is the most appropriate ceramic tool material for machining cast iron at a speed up to 1200 m/min.
4. Silicon carbide whisker-reinforced alumina, [SiCw-Al2O3]
Polycrystalline Diamond (PCD)
PCD, the hardest of all tool materials, exhibits excellent wear resistance, holds an extremely sharp edge, generates little friction in the cut, provides high fracture strength, and has good thermal conductivity. These properties contribute to PCD tooling’s long life in conventional and high speed machining of soft, nonferrous materials (aluminum, magnesium, copper, and brass alloys), advanced composites and metal-matrix composites, superalloys, and nonmetallic materials. PCD is particularly well suited for abrasive materials (i.e., drilling and reaming metal-matrix composites)
where it can provide significantly better tool life than carbide.
PCD is not usually recommended for ferrous materials due to the high solubility of diamond (carbon) in iron. However, they can be used to machine some of these materials under special conditions; for example, light milling cuts can be made in gray cast iron at speeds below 200 m/min.
PCD tooling requires a rigid machining system because PCD tools are very sensitive to vibration.
In mass production operations, the attainable tool life may be over 1 million parts (e.g., for diamond-tipped drills or PCD milling cutters machining soft aluminum alloys). However, tooling breaks due to vibration or rough handling might occur before wear becomes significant.
Grades of PCD vary between 1 and 100 μm. Grades are grouped in several categories with average grain sizes of 1–4, 5–10, and 20–50 μm. The abrasive wear resistance, thermal conductivity, and impact resistance increase with increasing grain size, but finer grained tools produce smoother machined surface finishes. A coarse-grained PCD tool may provide 50% better abrasive wear resistance than a fine-grained tool, but produce a surface with 50% higher roughness. New laser-honing methods can reduce edge radii for coarse grained PCD and produce finer finishes with these grades. Because of their increased impact and abrasive wear resistance, coarse grades are preferred for milling and for machining high-silicon aluminum alloys and metal-matrix composites.
Multimodal PCD grades (made with bimodal, trimodal, or quadimodal distributions of PCD particles) provide the high abrasion resistance of coarse-grained unimodal grade with the high toughness and superior edge sharpness of medium-size grain tools. The PCD density increases with multiple particles sizes. Multimodal grades are less prone to chipping than unimodal grades.
Laser structuring has recently been applied to flat-topped PCD inserts to produce 3-D chipbreaking grooves and similar features, which have proven effective in ductile material applications where chip control has traditionally been an issue.
PCD-tipped HSS or carbide rotary tools (e.g., reamers, end mills, drills, etc.) are available in a limited range of geometries due to difficulties in grinding complex geometries, particularly on small diameter tools. More complex geometries can be used on carbide rotary tools by sintering the diamond into slots (veins) located at the point and/or along the flutes.
Issues to be resolved include identifying the optimal cutting edge geometry for the diamond tip and the best method of pocketing the polycrystalline blank for strength and manufacturability. The methods of brazing the polycrystalline/carbide substrate tip to the main tool body have been improving steadily, but one of the major failure modes is still the detachment of the polycrystalline tip or the wear and erosion of the braze joints intersecting the cutting edge. Wear and erosion of brazed joints is avoided when the diamond is sintered into veins within the carbide tool.
The point geometry, flute geometry, and web thickness have not been refined sufficiently to allow use of polycrystalline brazed drills at penetration rates comparable to the feed rates attainable in turning and milling. (Stephenson-agapiou)
BASIC TYPES OF CUTTING TOOLS
The six basic types of cutting tools are solid tools, welded or brazed tip tools, brazed head tools,
sintered tools, inserted blade tools, and indexable tools
https://www.productionmachining.com/search?q=PCD
Case Studies
Production Machining - Cutting Tool Case Studies
Systems Approach to Tooling
Advanced Turning Insert Selection - Mitsubishi Course
http://www.mitsubishicarbide.com/permanent/courses/75/index.html
17.1.2020
Pocketing with high speed router RAL 90
The RAL90 aluminium milling cutter is designed for extremely high metal removal rates. The extra robust cutter body with optimized insert seats sets the standard for a new level of process stability in high speed milling - ideal for heavy roughing to semi-finishing pocketing of aerospace frames in aluminium alloys.
In applications requiring even higher metal removal rates, the new RAL90 Super MRR milling cutter can reach extra high spindle rotation, e.g. up to 33000 RPM for DC 50 mm compared to 23500 RPM for RAL90. This means a 40% productivity increase.
Machining aluminium for lighter and better recyclable vehicles
https://www.sandvik.coromant.com/gb/News/technical_articles/pages/machining-aluminium-for-lighter-and-better-recyclable-vehicles.aspx
Options, Benefits and Applications of Machining with Ceramic Turning or Milling Inserts
26/06/2019
https://www.cutwel.co.uk/what-are-the-benefits-of-machining-with-ceramic-turning-or-milling-inserts
12.2.2019
Kennametal’s KBH10B and KBH20B grades are designed for hard turning. They are available in double-sided inserts for materials as hard as 65 HRC. The inserts are for “high-volume production of hardened gears, shafts, bearings, housings and other drivetrain components. A ceramic binder structure and TiN/TiAlN/TiN coating provide extreme wear resistance even at elevated cutting speeds. A gold PVD coating makes it easier to identify when an insert needs indexing, while the numbered corners ensure that a machine operator does not inadvertently switch to a used edge. Edge preparation in a “trumpet-style” hone, is for heavier and interrupted cuts.
A light hone edge inserts are for continuous turning. Both inserts give extending tool life and generate surface finish values as low as 0.2 Ra.
https://www.mmsonline.com/products/pcbn-inserts-from-kennametal-make-hard-turning-more-cost-effective
2014-07-29 (Reg Ral 90)
An optimally designed, high-precision insert seat with seat numbering ensures a maximum runout accuracy of 20 microns axially and 15 microns radially, a
feed rate of 0.3 mm/tooth and cutting
depths of up to 14 mm.
https://www.sandvik.coromant.com/en-gb/news/press_releases/pages/ral90.aspx
Sandvik Coromant 2020 catalogues
https://www.sandvik.coromant.com/en-gb/downloads/pages/default.aspx
