HOME > OKUMA Only-One Technology > Thermo-Friendly Concept
 Getting on friendly terms with heat is what it's all about. Machine tools to date have been built to reduce heat as much as possible. The new idea, while still trying to minimize the amount of heat generated, is to deal with the heat that cannot be eliminated despite these attempts. Thermal deformation occurs in complex ways, and predicting the amount of displacement is nearly impossible. However, if we can arrange for thermal deformation to occur only in predictable ways, it may be possible to eliminate the effects of heat through compensation. Thus, even without large-scale air conditioning equipment to control the temperature in an entire plant or shop floor, high machining accuracy can be maintained if the temperature remains within the range of normal atmospheric temperatures. Now, let's see how the MB-46VA vertical machining center embodies the "Thermo-Friendly" concept with some actual examples.   Now Okuma has developed a simple, new block stacking construction for the column called a box-built structure, which at the same time is thermally symmetric in which the right and left sides have roughly equal masses. With this simple, balanced block assembly, the machine will grow and shrink—as predicted—as the ambient air changes. The amount of expansion and contraction can be predicted in the design stage based on thermal analysis, and comparisons with measurement data from actual machines have shown nearly equivalent amounts of change. Moreover, if the column includes both exposed and covered sections there will be differences in the way the ambient air is transmitted so as to prevent uniform temperature changes. To counter this, a thermally balanced structure (Fig 1) is used to obtain the same conditions on the front and back sides, with a column cover on the front and the NC cabinet located in back. These measures make it possible to predict the amount of heat change. 
 The largest source of heat generation in a machine tool is from the main spindle motor. To reduce the amount of heat generated and for efficient cooling, a double-structure oil jacket is used to enclose the main spindle bearings. These bearings are lubricated with oil air, with the nozzles positioned on both sides to provide thermal balance. Nevertheless, more heat is generated as the spindle speed increases. These measures alone cannot eliminate the thermal growth caused by the higher spindle speeds. This is why Okuma has developed a new spindle thermal deformation control TAS-S that predicts and compensates for changes in the amount of heat generated by the main spindle. Temperature sensors are attached to the machine so minor adjustments to changes in various conditions (at the start, during, and end of machining, spindle speeds, etc) can be made. Temperature tracking delays, minute temperature changes and other conditions are also factored in the compensation equation. (Fig 2) 
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