Inserts
Deep Hole Boring and Vibration Resistance
Deep Hole Boring and Vibration Resistance
Deep hole boring is a metalworking process that can cut holes that are ten times deeper than their diameter.deep hole boring It is used in a range of industries to machine tight tolerances and superior straightness into workpieces. Typically, the bores are made from high-quality materials such as aluminum and super-alloys. Deep hole drilling is the foundation for a number of additional processes to improve straightness and add features to workpieces, including skiving (hydraulic cylinders), counterboring, trepanning, roller burnishing and pull boring. All of these processes machine the inside surface of an existing bore in a workpiece, and most are performed on BTA-style deep hole drilling machines.
One of the challenges with cutting high length-to-diameter holes is overcoming hole drift, which can lead to poor surface finish and reduced machined tolerances.deep hole boring One way to combat it is counter-rotating the workpiece, but this is not always possible with cylindrical parts. If counter-rotation is not an option, reverting to best metal cutting practices can be effective.
The use of the correct insert grade, geometry, nose radius and rake angle is essential to avoid poor surface finish, vibrations and tool wear. Choosing the correct bore bar is also crucial, as it needs to be as rigid as possible to maintain cutting stability, but should not be so large that it obstructs chip evacuation.
Another issue that arises when machining these long workpieces is chatter, which can disrupt the precision of the bore and lead to poor surface finish, rapid tool wear and short cutting life. A solution to this is increasing the static and dynamic stiffness of the bore bar, which can be accomplished by optimizing bar geometry and using materials with a higher modulus of elasticity. It can also be accomplished by adding damping to the bar.
This is achieved by building a ring of stiffeners around the bar, which increases its mass and reduces its amplitude in response to variable forces. The resulting bar is significantly less susceptible to chatter than conventional bars, according to Khoroshailo et al. [8].
In addition to addressing the problems of chatter and stiffness, this research also focused on improving the vibration resistance of a long-bar bore. A prototype was built, and experimental modal analysis and displacement tests were conducted to evaluate the results. The results showed that the prototype bore bar had a lower displacement value than the conventional one, and demonstrated a reduction in vibration amplitude values at the machining tip of the workpiece during the boring process. The results demonstrate the effectiveness of the proposed approach, and a further optimization of the machining process is planned. The full paper can be found here.
0users like this.
