B. Moetakef-Imani, N.Z.Yussefian 10 July 2009 Aaron Boyd October 28, 2009

FUNCTION To simulated the dynamic response in boring processes To predict vibrations in the operation

Why Important? Tool vibrations result in reduced tool life, poor surface finish and may also introduce chatter. Predicting these vibrations allow the operator to know under what conditions the operation will be most efficient.

References

Boring Process Process of enlarging a previously drilled hole High Precision and good surface finish

Vibrations 3 types Free/Transient: most common, caused by initial engagement between tool and part, will vibrate naturally until damped Forced: applied to tool structure, commonly caused by multi-insert tools and run-out of the tool tip; also caused by other machinery; if it hits natural frequency, resonance can occur Self-Excited: caused when tool cuts, chatter occurs when parameters (DOC, feed rate, etc.) are incorrect; can cause part deflection

Chatter Loop

Equations of Motion Euler-Bernoulli Beam Differential Equation Natural Frequency Beam Deflection

Kinematics of Chip-Load Formation Cutting Edge Equations B-Spline Parametric Curves

Instantaneous Chip Load Cutting Edge Contact Length

Dynamic Simulation

Tests Test A: Undergoes transient vibrations, but stabilizes Chatter free Vibrates at constant amplitude Test B: Process that doesn’t stabilize Chatter present

Results (test A) Simulated peak frequency is 672 Hz compared to a measured value of 594 Hz – 12.94% error. Deviation stems from overestimation by the Euler- Bernoulli beam equation For x, y and z measurements – 9%, 2%, and 12% error respectively

Results (test B) simulation shows chatter chattering freq. at 573 Hz random oscillation variation increases tool plunges into workpiece makes prediction almost impossible However, still useful to predict chatter

Conclusions More accurate than previous models Previous models only predicted stability region, while this model predicts dynamic region – very useful In chatter-free operation, the simulation predicts within +/- 15% of the actual measured value It is a valid simulation for both smoothing and roughing Predicts chatter so operators can avoid it completely Uses all influential parameters

Impacted Industries Automotive Industry Firearms Pretty much any industry that involves drilling holes

Useful? There seemed to be a lack of some vital information, but this information could be found by referring to the references (the refer to them often). However, the results will allow operators to know what to expect from their operations. They will be able to know what frequencies to expect and will be able to prevent chatter. Overall, it’s a rather useful paper.