Mikron Tool SA Agno says it has achieved a quantum leap in milling of stainless steel, titanium, chrome-cobalt alloys and superalloys with the CrazyMill Cool. Machining stainless steels can be a challenge. One factor is that the tool becomes extremely hot due to the poor heat conductivity of these materials and thus wears and can be damaged quickly. Also the factor efficiency and surface quality is an ongoing topic. With the CrazyMill Cool, Mikron Tool SA Agno achieved a solid-carbide endmill with through-coolant capability in the diameters from 0.3mm to 4mm (0.02" to 0.15"), doing justice to the product's somewhat wild name. Slot or pocket milling into solid material and contour milling are its strengths. The tool combines roughing and finishing, promising at the same time high efficiency, long tool life and a much better surface quality, according to the company.
That these promises can be kept and that the researchers of the Swiss Tool manufacturer once more talk about a "crazy" tool, for that several factors are decisive. First is the raw material, a newly developed micro granulate carbide, which fulfills the requirements of hardness as well as toughness. Obviously, the design of the tool with its cutting geometry, which is specific but not limited for the machining of stainless steels, helps the tool to achieve its outstanding performance. A combination of different geometric characteristics lead to the targeted results. A robust cutting body, a radial relief and a very specific cutting edge preparation afford a very high cutting edge quality and stability. An important contribution for the tool life is also the coating, which is innovative and also specific for hard-to-cut metals. With a extremely low friction coefficient and a reduced affinity with steel, build up at the cutting edges is avoided. Furthermore the coating has a high oxidation resistance and heat hardness. This helps to maintain the temperature in the green range and a "burning" of the cutting edges is avoided, which in turn is positive for tool life and surface quality.
The essence of innovation is however connected with the "cool" part of the tool's name. Generally valid is that dry machining is not possible with stainless steels. Due to the bad heat conductivity of the material the tool would become extremely hot, the cutting edges burn out. The use of a coolant is a must. Mikron's microcutter has three to four internal coolant channels which go through the shaft and bring such coolant along the diameter to the cutting edges. The result is a targeted and massive cooling effect where it's needed: at the cutting edges in every machining position. Simultaneously chips are continuously flushed away from the milling area, where they would disrupt the milling operation and could influence the surface quality negatively. In relation to the small diameters of the milling cutters the cooling channels are rather large. The large volume of coolant created is highly efficient; the friction heat is substantially absorbed and removed by the coolant. It is also interesting that no special requirements are necessary for filtering and coolant pressure. Hence these tools can also be used profitably on conventional machines. Up to date an infeed of 0.1 to 0.2 x D was recommended to mill a channel into solid material. The CrazyMill Cool is able to achieved depths of 1 to 1.3 x D directly.
Markus Schnyder, the responsible for Mikron Tool International points out, that one does not have to be a calculus genius to find out, that with up to five times faster cutting speed and a comparable feed the efficiency of the milling cutter is improved by a factor of 10 to 20. With this it is interesting that expressly the "difficult" materials are the ones where the difference regarding performance is most astounding. The cherry on the cake is, according to Mikron Tool, the surface quality. Even though the cut goes into solid material, the CrazyMill Cool boasts Rz values which are 2 to 3 times better, than what can be expected from conventional cutters.
A complete inventory of standardized, small, milling cutters will be available for applications in industry segments such as watch-making, medicinal and surgical technologies etc. A first series of cylindrical, small cutters in diameter of 0.3mm to 4mm (0.02" to 0.16") has been launched. A short version for maximum depths of 1.5 x D, a medium version for 3 x D and a long version for 5xD are available. All of these have a cutting head of 1.5 x D.
Related Glossary Terms
Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.
Rotary tool that removes hard or soft materials similar to a rotary file. A bur’s teeth, or flutes, have a negative rake.
Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.
- cutting speed
Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).
- edge preparation
Conditioning of the cutting edge, such as a honing or chamfering, to make it stronger and less susceptible to chipping. A chamfer is a bevel on the tool’s cutting edge; the angle is measured from the cutting face downward and generally varies from 25° to 45°. Honing is the process of rounding or blunting the cutting edge with abrasives, either manually or mechanically.
Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- milling cutter
Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.
- milling machine ( mill)
milling machine ( mill)
Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.
Space provided behind the cutting edges to prevent rubbing. Sometimes called primary relief. Secondary relief provides additional space behind primary relief. Relief on end teeth is axial relief; relief on side teeth is peripheral relief.
- stainless steels
Stainless steels possess high strength, heat resistance, excellent workability and erosion resistance. Four general classes have been developed to cover a range of mechanical and physical properties for particular applications. The four classes are: the austenitic types of the chromium-nickel-manganese 200 series and the chromium-nickel 300 series; the martensitic types of the chromium, hardenable 400 series; the chromium, nonhardenable 400-series ferritic types; and the precipitation-hardening type of chromium-nickel alloys with additional elements that are hardenable by solution treating and aging.
Tough, difficult-to-machine alloys; includes Hastelloy, Inconel and Monel. Many are nickel-base metals.