# Prediction Methods and Experimental Techniques for Chatter Avoidance in Turning Systems: A Review
## 5 Practical Solutions for Industry  
Although chatter has been known for some time and different tools have been developed to dominate and control surface quality, the use of these tools must be implemented on a case by case basis. If vibrations occur, the operator intuitively reduces the cutting parameters. This reduces productivity and is not always a guaranteed solution. To solve this gap between theoretical knowledge of vibrations  
Figure 7: (**a**) CLD tool holder in turning; (**b**) Frequency Response function with steel tool holder and CLD tool holder [110]. and the industrial field, different simulation packages have been developed based on the measurement of some characteristic magnitudes during cutting. CutPro/MachPro/ChatterPro/SpindlePro/NPro(c) (developed in the Manufacturing Laboratory of the British Columbia University, Vancouver under the direction of Professor [PERSON] [115]): probably represents the best package to solve problems in machining as these functionalities deal with different machining aspects/problems. Cut Pro was the original software resulting in a wide family of products. It allows determining the best cutting parameters. As usual, prior to the simulations, the customer needs to identify the dynamic parameters (modal mass, damping ratio, and stiffness) of the tool/piece system as well as cutting coefficients. If one of the following elements is changed: (1) machine-tool and/or fixtures; (2) workpiece material (maybe the same material but from another batch); (3) cutting tool (overhang, toolholder, wear), the system needs to be characterized again because, in general, the cutting coefficients and the modal parameters will be different. To obtain the modal parameters, the software is capable of performing 3D modal analysis to filter and process the transfer functions and to obtain the fundamental modes. These are then used to simulate the stability lobes. SpindlePro is focused on the design and analysis of spindle systems; NPro is the implementation of CAM (Computer-Aided Manufacturing) and its combination with chatter requisites. The software is capable of simulating and optimizing tool paths. Harmonizer(c) (developed in the MLI (Manufacturing Laboratories Inc.) of Las Vegas [116]): this software has been developed by years of experience for the control and reduction of vibrations in machining and leading to different packages: MilSim, CRAC (Chatter Avoidance and Recognition), MTDA (Machine Tool Dynamic Analyzer) and finally, Harmonizer(c). Given a certain depth of cut and spindle speed, the analysis of the acoustic signal during machining allows to determine chatter frequency if the cut is unstable. In two or three iterations, the program is able to find a suitable spindle speed where the cut is free of chatter. If the initial depth of cut is too far from the final one or the modes are highly variable (magnitude and direction) over time such as in finishing operations, the system may have converging difficulties. Therefore, the system is more useful for 1-DOF systems and roughing operations. Recently, researchers presented BlueSwarf (MetalMAX(c)) which is an evolution for the rapid characterization of cutting process dynamics. EMMATools from SMARTIbox(c) (Spindle Measuring and Analyzing Relevant Tool for Industry Box): this software emerged from the collaboration between the University of Nantes [117] and the Airbus company for the monitoring and preventive maintenance of high-speed spindles. Rotor displacements are measured, cutting frequency harmonics are analyzed through embedded sensors. By means of spindle monitoring, the stress levels and associated frequencies are controlled for the best benefit of spindle life, thus protecting the bearings. Machining Navi(c) [118]: machine builders are also interested in selling machines with superior capacities. Machining Navi is one of the latest developments from Okuma for solving online chatter problems, it integrates a detection software within the numerical control of the machine itself.