# Investigation of the Machining Stability of a Milling Machine with Hybrid Guideway Systems
## 5 Conclusions  
This study employed the finite element modeling technology to investigate the machining stability of a horizontal milling machine with a movable column on hybrid guideway mechanism. Currently, a number of studies based on finite element methods have been employed to analyze the dynamic behavior of a machine tool with different configurations. As mentioned above, a realistic model should be created to reflect the various characteristics of different components such as the linear guide system and spindle bearing system. In this study, a full FE model of the milling machine with a hybrid guide system was created in this way. Apart from the machine frame, the linear components such as linear roller guides were also simulated by solid elements and interface elements at the sliding/rolling interfaces. These interfaces were respectively characterized by appropriate contact properties, which were determined based on associated mathematical models according to their preloaded status. A solid spindle-bearing model, which was experimentally verified by means of physical spindle, was also incorporated into the machine frame model. The full FE model is different from the rigid-flexible coupling models in which reduced FE model of the main modules were coupled at the connection joints with spring elements. The coupled FE model provides a relevant approximation of the dynamic properties and less vibration modes because of the reduced degree of freedoms in each flexible body. Whereas the full FE machine model can offer accurate visualizations on the dynamic behaviors of the spindle system and machine structure. According to the finite element simulation, the fundamental vibration modes relating to the spindle module are dominated by the feeding mechanisms of the movable column and the spindle ram. The frequency response of the milling tool shows two apparent characteristics, including the lower modes dominated by the yawing vibration of the spindle ram coupled with the twisting vibration of the movable vertical column, and the higher modes associated with the bending of the spindle shaft.  
The machining stability based on the machine structure mode allows the cutter to operate with high axial depth under lower spindle speed, while the machining stability based on spindle structure mode is valid for a high speed machine with less cutting depth. In addition, in this case the horizontal spindle head with low preloaded linear guides show a lower cutting depth for stable machining than that with higher preloaded guides. As a conclusion, the realizations on the dynamic behaviors of a milling machine based on the proposed FE model can provide valuable design improvements of the machine structure or guideway system of the machine tool.  
We gratefully acknowledge the support for this work provided by National Science Council in Taiwan through project number MOST103-2221-E-167-004.  
[PERSON] contributed to the organization of the research work as well as the analysis of the machine system and manuscript preparation. [PERSON] [PERSON] contributed to the design and analysis of the machine structure. [PERSON] conducted the experimental work of the spindle systems.  
The authors declare no conflict of interest.