Compared to other materials, aluminium is rather simple to machine. At least it seems much more effortless than steel, for example. Nevertheless, there are several mistakes that can be made when machining this material, including the choice of the wrong tool, that impact productivity.
Milling aluminium appears to be a remarkably easy process. Often, people who are not directly involved in machining aluminium hold misguided views. They believe that it’s enough to take a balanced, sharp, polished tool and rotate it at maximal speed, set at medium feed, and the material will cut like butter.
In comparison to machining steel, aluminium and its alloys require much less cutting force, and therefore the cutting edge of a milling tool experiences relatively low mechanical loading. For the purpose of this article, we refer to aluminium and its alloys as aluminium. Aluminium exhibits high thermal conductivity and therefore the chips produced when machining aluminium transfer high levels of generated heat, resulting in significantly reduced thermal loading of the cutting edge. Due to these properties, milling aluminium is characterised by extremely high cutting speeds and feeds. Nonetheless, this does not guarantee that milling aluminium is quite so simple.
The material characteristics of aluminium result in the formation of built-up edge (BUE) when machined. This unwelcome phenomenon increases the mechanical load on the cutting edge, making efficient chip flow more difficult to achieve, affecting the balance of rotating tools and causing the entire machining process to be less efficient.
The evacuation of aluminium chips may also be affected by using the wrong kind of cutting tool. If the volume of a tool’s chip gullet (flute) is not sufficient, the long chips during aluminium milling will clog the tool. Overcoming this obstacle demands the use of a tool with less teeth or reducing the applied cutting data; actions that negatively impact productivity.
From a machinability point of view, aluminium is not a material that is uniform. Alloying elements (in particular, silicon), material type (wrought, cast) and treatment methods all affect cutting properties. Multiple other factors such as the shape of a machine part, workholding conditions and operational requirements (accuracy, roughness, etc.) add their own limitations and must be considered when choosing machining strategies and selecting a tool. Hence, in many cases, machining aluminium in general and milling aluminium, in particular, are often not the simple tasks they appear to be.
The correct combination of geometry, material and treatment
Tool manufacturers take the specific features of milling aluminium into consideration when developing cutters. A key to success is the correct combination of cutting geometry, tool material and tool treatment, in addition to the options for delivery of optimum coolant supply.
When considering applications for milling aluminium, large aircraft components, such as wing elements, door or window frames, etc., come to mind. Generally, these parts are produced from whole blocks, often weighing several tons, and it is often necessary to remove up to 80-85% of the block weight to produce the final required shape of a component. In contrast, the global automotive industry, which is also a massive consumer of aluminium, has introduced various hard cast aluminium grades to their components. The increased abrasiveness of these parts negatively affects tool wear.
Iscar, a full-line supplier of cutting tools, has developed a comprehensive range of indexable milling cutters, designed specifically for the efficient machining of aluminium. Each family of these high-quality cutters features integral or lightweight body designs, unique principles of carbide insert clamping, structures with adjustable cartridges, various ground and polished inserts with different corner radii, and, most popular in aluminium machining, inserts with polycrystalline diamond (PCD) tips. The vast majority of the cutters have inner channels for coolant supply through the body. The Iscar Heliali line of indexable milling tools enables efficient high-speed machining (HSM) of aluminium, ensuring powerful metal removal rates (MRR), high accuracy and excellent surface finish characteristics, all of the qualities demanded by the world’s producers of aluminium components.
Iscar produced its own video about the machining of aluminium. Watch it here to learn more about the tools:
Metalworking industries produce large and small aluminium parts, and in many cases require milling cutters with more modest dimensions. The size of these tools is not suitable for indexable inserts and solid carbide tools have distinct advantages. Moreover, the high accuracy of solid carbide endmills renders them beyond comparison when used in precision finishing of larger components. Therefore, Iscar remains heavily involved in the design and development of advanced solid carbide tools for the milling of aluminium. Recent progressive additions to this all-embracing range have further increased their value to users throughout the industrial world.
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