Luis Urena

My name is Luis Urena and I’m a Mechanical Engineering graduate from the Technological University of Panama. For my graduation project I studied Localization and Map Construction with a mobile robot named AmigoBot. I graduated from the same University with a Master’s Degree (MSc) in Science of the Mechanical Engineering and my work was focused on optimization parallel robot 3RPS for grinding purposes. The research that I performed during my Master’s program stimulated my interest in robotic machining. To further deepen my knowledge, I have completed my MSc (Res) in Advanced Manufacturing Technologies at the University of Sheffield. My research project involved working on the compliance error compensation in milling of an ABB-6660 robot.  Currently, I’m in the second year PhD student at the University of Sheffield and the main aim of my current research project is to experimentally validate the results of a helix angle optimization in a milling tool obtained in a previous work.

Research interests:

  • Milling with variable helix tools.
  • Robotic machining.
  • Optimization of the mechanical design of parallel robots.

Current research:

Nowadays, it has been an increasing demand for products made entirely or partially of metal parts. As a consequence, companies have been pursuing for ways to augment the productivity of machining processes by increasing the cutting velocities and depth of cuts. However, one of the main obstacles that emerges with these improvements is the appearance of vibration due to regeneration chatter.

Particularly in milling, one approach to cancel the regenerative chatter effect is by varying the helix and/or pitch angles of the tool flutes. By this means, the constant time delay found in regular milling tools is broken into a distributed group of time delays. 

Therefore, the chip thickness is not only dependant on the phase difference between the current and previous wavinesses, but also on the phase difference among the undulation left by all the preceding unequal spaced teeth in the previous revolution. Therefore, by selecting an adequate arrangement of teeth in the cutter, it is possible to suppress regeneration chatter vibration in milling.

The implementation of irregular tools in milling, and in particular the use of variable helix tools, is a subject that needs to be more studied in order to take advantage of its full potential.

The main aim of my current research project is to experimentally validate the results of a helix angle optimization in a milling tool obtained in a previous work. For this purpose, it will be implemented a compliant flexure along with displacement sensors, accelerometer and a laser tacho-probe, with the aim to gather vibration signals, one per revolution displacement data.

The vibration data will be analysed by frequency domain while with the one per revolution data in time domain, it will be created the Poincare diagram. With this information, it will be possible to categorize the cutting processes as stable or unstable and also categorize the unstable solutions as period one, double or Hopf bifurcation.

Cutting trials to determine the cutting force coefficients using copolymer acetal as workpiece and a 16 mm 3-teeth regular tool. 

Cutting trial to determine Stability Lobes diagram with the experimental flexure.