To carry out any machining process, first of all you need to know the physical characteristics of the material you are going to work with, the cutting angles and the speeds among other parameters, all important factors when selecting cutting tools.
In the following entries, starting with this one, we will address the topic on the cutting tools needed to machine specific materials, and start with aluminum. In our previous article we addressed the topic on different types of materials of cutting tools that are used for machining.
Aluminum is one of the most common and popular materials for machining. Aluminum is, in its pure form, a chemical element of symbol Al and atomic number 13, silver, non-magnetic, relative low density (within metals) and low mechanical resistance, ductile and corrosion resistant and virtually no toxicity. Along steel, it is one of the most used materials in the modern metalworking industry due to the wide variety of alloys that give it multiple useful properties, forming the basis of industries such as food (for packaging), mechanical, automotive and aerospace. In this article we are going to refer to both aluminum and aluminum alloys simply as 'aluminum'.
Characteristics of aluminum machining
In metalworking, it is common to think that aluminum machining is a simple process, and that it is sufficient to have balanced and sharp cutting tools and rotate them at maximum speed, believing that this will allow the material to be cut like butter, but it is not always that easy. While it is true that, in comparison to steel, aluminum and its alloys require lower cutting forces (so the cutting edge of the cutting tools experiences a relatively low mechanical load) there are several other details that must be taken in account.
Aluminum has high thermal conductivity, so the chips produced during its machining transfer a large amount of heat out reducing the thermal load of the cutting edge and the consumption of coolant (in addition to being highly resistant to corrosion). Due to these characteristics, the machining of aluminum can be done with high cutting speeds and advances as mentioned above, but, this does not mean that the milling of aluminum is simple, because another of the characteristics of aluminum is that it is very susceptible to material accumulation on the cutting edge of the cutting tool when the chip gets trapped during the machining process (a kind of dulling). The incorrect selection of the cutting tool will also be reflected in the poor evacuation of the chip, a phenomenon that increases the mechanical load on the cutting edge and that will jam the tool decreasing the quality of the machining process. Therefore, unlike steel, the angles of attack tend to be greater.
From the machinability point of view, aluminum is not a uniform material. Alloy elements (especially silicon) and treatment methods affect the properties of the cutting process, and the hardness variability of the alloys may vary from HB15 (pure aluminum) to about HB110 of aluminum 7075 (AlZnMgCu).
There are other aspects, such as the shape of the piece to be machined, the operational requirements (precision, roughness, etc.) and the fixing conditions, which add their own limitations and need to be considered when selecting cutting tools and machining strategy.
Cutting tool brands for aluminum machining
We already mentioned that for aluminum machining the cutting tool requires special features; it is desirable that the tools used for this type of materials allow the efficient evacuation of the material to avoid dullness that can ruin the piece and the cutting tool, and diversity of materials for different cutting requirements; HSS cobalted for rough cutting, carbides for high speed, and diamond for finishing.
The manufacturers of tools of cutting take into account all the peculiarities of the machining of aluminum for the design of the tools. A key factor for success is the correct combination of the cutting geometry, the material and the treatment of the tool, in addition to the optimal cooling system.
Kyocera, Union Tools, Mitsubishi Materials, CKD, NTK, OSG, global suppliers of cutting tools in Mexico, have developed extensive ranges of tools with interchangeable cutting inserts, specially designed for efficient aluminum machining.
All high quality cutting tool families have an integral body design and are lightweight, with excellent fixing systems for carbide inserts, structures with adjustable cartridges, various types of rectifying and polishing inserts with different radii of tip; and the most popular for aluminum machining, polycrystalline diamond tip (PCD) inserts.
An industry's favorite in Cutting Tools, materials and grades for turning aluminum alloys in all types of cuts and hardnesses. HTi10, TF15 (carbides), MD205, MD220, MD230 (diamond cutting). Mitsubishi Materials also has a line of interchangeable head cutters (end mills), the iMX line, for versatile processes that require constant changes and adjustments in production.
Kyocera Precision Tools provides a variety of grades and geometries in inserts for aluminum cutting; carbides, DLC’s and PCD for turning, cutting, boring, milling and carbides for drilling (grades KW, GW, PDL, KPD), as well as solid cutters (end mills) of carbide and DLC. Superior features for different applications and a wide variety of geometries and chipbreakers. The wide variety of clamping tools allow any type of cutting: grinding, cornering, rounded, grooved, countersunk, radial or contour.
Union Tool Co. is a specialist in solid cutting tools. With a wide variety of cutter sizes, Union Tool tools allow machining of tiny diameters (0.05mm circular) on carbides (CSEB series) and have a variety of geometries (square, radial and circular) and DLC tools (series AZS, CSEB, CFB, CFLB, UTDF).
In conclusion, aluminum is one of the metals most machined in production processes and requires much less energy than that used in steel machining, it is done at high cutting and feed rates providing high quality surface finishes. And it is worth saying that the machining of aluminum is simple, if it is done intelligently!
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Saludos!
Luis Daniel Arzola (daniel.arzola@yamazen.com.mx)