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Machining with greater precision and without waste? Numerical modeling can be the solution

25 November 2020
Article by Tiago Fraga, researcher, and Diogo Fula, responsible for business development in the area of advanced manufacturing technologies at INEGI. 

Machining is the most common manufacturing process for creating precision metal components. It is a process of cutting a material to create a part, and it is transversal and complementary to all other manufacturing processes, from casting to forging. 

Most components that have functional technical surfaces need to be subjected to the most diverse machining processes, in order to obtain the surface quality and dimensional tolerances required for the function for which they are intended. 

However, from an economic point of view, it is an expensive process, as it involves the waste of large amounts of material and results in a short tool longevity. It is still conventional to use tuning methods based on empirical experience and "trial and error" techniques, which is why it is important to improve the cutting process. Essentially, understand the mechanisms of shaving formation and predict results depending on the cutting parameters. 

The numerical modeling of the machining processes is a possible answer to this challenge, which we have been exploring, since it would allow to estimate the useful life of the tools and the quality obtained according to the working conditions, namely the cutting parameters. 

The design of a cutting tool is a complex process, and numerical simulation appears as an appropriate solution. The finite element simulations allow an adequate and efficient three-dimensional representation of the shavings, and respective analysis from the point of view of the ideal geometry design of the cutting tool. 

Modeling contributes to production control and prediction of tool longevity 

The objective is simple: to maximize productivity, without jeopardizing the surface quality and dimensional accuracy of the products. For this, production control is crucial, particularly in relation to shavings, since high-speed machining results in a large amount of shavings obtained in a short period of time. 

The inability to control the size and shape of the chip translates into frequent stoppage of the equipment and increased production costs, which may even jeopardize the safety of operators. The surface finish, dimensional accuracy and premature wear of the tools are also affected by the incorrect control in their formation. 

At the same time, the correct estimate of wear and remaining tool life is also a critical area in the planning and optimization of the machining process. Achieving maximum productivity, with the lowest possible costs, involves determining the material and geometry of the tool, in addition to, of course, the appropriate cutting parameters. And this is where numerical simulation comes in. 

When using numerical models, we obtain a more in-depth view of the cutting process from the prediction of cutting forces, contact pressure, temperature field and shaving morphology. Information that can be used to produce more efficient tools and provide feedback on its useful life and the degree of machinability under certain cutting conditions. 

There are also gains in post-processing of parts made by Additive Manufacturing 

This solution can also add value to the additive manufacturing process. 3D metal printing is close to becoming a sustainable production process, with a wide range of metallic material options available today, capable of obtaining intricate geometries, making the process attractive to various industries. 

However, the majority of metal parts resulting from additive manufacturing will require post-processing, namely machining of contact areas where it is necessary to guarantee smooth surfaces, or simply to remove construction supports. These post machining, cutting and drilling operations on printed parts, however, have additional challenges due to the anisotropic behavior derived from the layered construction, which accumulate residual stresses that are distributed evenly over the part. 

That is why complete control of metal cutting operations is essential to ensure successful post-processing of these components, which are too valuable to compromise on defective machining. 
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