Multipolar system 6dof

This prototype is especially suitable for processes such as plasma cutting, laser cutting and waterjet. An important is the ability to share-out of efforts (torque, acceleration, speed) among several polar axes which are firmly hooked on the base. Thanks to the collaboration of Aerospace engineering department of Politecnico di Milano, published during the 2th Joint International Conference on Multi-body System Dynamics (IMSD 2012), trajectories with vertical or oblique end-effector  can be executed at constant velocity, both on straight-path and corners. On customer request we are testing the operation of plasma cutting and bevel of a 800mm square with the end-effector skewed 45 degree. We are working to obtain constant bean trejectories to obtain a cutting result much better than actual standads.

 

 

 

The video is showing a test trajectory with the cutting head substituted by a drawing pen moving at 10mm/s.
It is important to underline the wish to limit extremly the resources needed to build the mechanical structure with the goal of studying and estimating  the trajectory executability at a disadvantage. We want to obtain informations to make a very cheap product and a competitive advantage. This is the reason why this prototype has been built with low-power stepper motor unit (1Nm), heavy rotating disks (100 Kg) and steel chains as trasmission. Despite these limits, the result fulfill the expectations and this shows substamtial room for improvement. To reach our goals we are collaborating with Aerospace engineering department on a algorithm concerning multipolar systems. The software receives the digital description of the trajectory (example cad-cam document) and splits it into the list of time-based commands needed by every single axle.  Numerically the trajectory in the example has been calculated at a working speed of 800mm/s (and it is not the upper limit), afterwards it has been slowed down to requested speed.

The torque graphs compare two ways to make the same path with different parameters. The first case used without consider the limit of dynamic, shows a rought movement defined by over-torque and over angular speed. On the contrary the second case shows a soft dynamic with limited torque and forces. This evidences how the algorithm is able to fit different need and different systems. moreover it is important to say that both cases has been successfully executed by the prototype, in particular the video shows the worst case.

 

The same technology can be applied on different structures with different features. The following example made by Alpha Progetti shows how to get a cutting head with multipolar kinematic minimizing dimension.

 

References: LINK