Machining Dynamics Group performs research in the following areas:
- Predictive Models
- Spindle Dynamics
- Workpiece Dynamics
- Workholding and Automation
- Vibration Control
- Robotic, Robotic Assisted Milling
- Composite Milling
- Micro milling
- Power Skiving
Machining dynamics deals with the interaction between the machining process, machine tool and workpiece. As a result of the machining process, machine tool and workpiece are exposed to cutting forces. This causes tool and workpiece displacements which contribute to the form errors.
High cutting forces lead to high form errors which can lead to unacceptable parts due to the dimensional tolerances on the parts. Moreover, higher cutting forces may even break the tool due to the resulting bending stresses or they can cause the spindle to stall if torque and power limits of the machine are exceeded. On the other hand, stability of the process is also important for the performance of the process. Resulting vibrations due to instability can cause surface marks on machined surface which result in surface quality problems. In order to prevent these issues, predictive process models can be used in parameter selection phase to find the optimum process parameters that maximises productivity while respecting the aforementioned constraints.
The group makes use of process models in optimum parameter selection for many machining process like turning, milling, parallel machining, ceramic milling, composite milling, 5-axis milling, etc. against constraints such as cutting forces, torque, power, form errors and surface roughness.Moreover, these models can be used in model based control of the machining processes as planned in the Twin-control project.
Depending on the design of the machine tool spindle, spindle can demonstrate non-linear dynamic response under rotating or operational conditions. The non-linearity may be due to the centrifugal forces, gyroscopic effects, thermal loads, preload and/or cutting forces. These effects can cause erroneous predictions of process stability. Spindle dynamics research is instrumental to understand the source of these errors and take this non-linearity into account to calculate stable cutting parameters more accurately.
Machining system consists of machine tool, process and workpiece. Unless workpiece is considerably rigid compared to the cutting tool, the flexibility of the workpiece needs to be taken into account in stability predictions. Depending on the workpiece geometry, dynamics of the workpiece can be location dependent. Workpiece flexibility can be measured by standard tap testing process although it may be more time consuming depending on the complexity of the part unlike tap testing of the tool. Furthermore, the dynamics of the workpiece can change considerably due to material removal in the machining process, which makes the dynamic properties of the part time dependent. Workpiece dynamics strand researches the methods to predict the location and time dependent variation of workpiece dynamics. The output of this research feeds the stability predictions.
Work-holding and Automation
Work-holding and Automation research strand focuses on fixture static, fixture dynamics, vibration control, noise control, distortion control, residual stress release, flexible hinge, hydraulics, pneumatics, precision engineering & related product development.
Application of active and passive vibration control techniques can considerably increase the material removal rate in machining processes while avoiding vibration problems. The group has delivered a project on passive vibration control using piezoelectric patches in turning. The projects to further this work and active vibration control projects are in the future plans of the group.
Robotic, Robotic assisted machining
Large part manufacturing, reconfigurable manufacturing and parallel machining are three drivers that will make robots appear more and more in machining operations. The Group has recently won a H2020 project, COROMA, to work on this area between 2016 and 2019.
Machining Dynamics Group has been working in close collaboration with composites group on developing analytical process models fro cutting forces and stability to guide the parameter selection and optimise composite milling processes.
In micro milling, achieving the required accuracy and surface finish is a trial and error process that relies on past experience.The group is aiming to change this by using the new micro machining capability (Kern Evo) to explore the science involved and develop modelling and simulation tools that will enable manufacturers to achieve right first time and optimise existing processes. The group is planning new intern, MSc and PhD projects to develop simulation and measurement capabilities in micro milling. The group also hopes to work with manufacturers facing micro machining challenges, while also collaborating with researchers worldwide to cut costs, improve quality and boost the competitiveness of companies involved in micro machining. The group organised a seminar and a demonstration day at AMRC. For more information on this event, please visit the link.
Power skiving is a high productivity machining process for manufacture of gears. Although its development dates back to 1910, it is still not considered as a mature process compared to other machining processes. The group is working on elimination of barriers for wider adoption of the process in gear manufacturing.