“The Open Frame Proportional Controller” – explains Alessandro Speziali – is a valve whose function is to modulate the pressure and air flow in a through rod cylinder, allowing the application to meet the customer's operating requirements. In this case, the Open Frame Proportional Controller in positioner version is equipped with a specific control algorithm to guarantee high processing performance.”
“The Open Frame Proportional Controller was fitted to our 'EvoL' wood panel sanding machine,” explains Alessandro Fabbri, “so as to calibrate and accurately sand the surface of the workpiece. This is a constantly evolving product line, designed to offer the highest possible flexibility and ease of use, while guaranteeing high processing quality and savings in operating costs.
Specifically, we have fitted the valve near the pneumatic belt control cylinder of the sanding machine. These machines are equipped with contact roll units or a platen around which, with the help of a tensioning roller, an abrasive belt is stretched. The abrasive belt is then put into rotation and works on any material that is in contact. For the process to be successful, it is essential that the rotating abrasive belt maintains a stable controlled position in relation to the axis of the rollers. In fact, abrasive belts can have a taper due to their construction, which generates asymmetrical working forces. This results in a trend for the belt to move away from the desired position during use, leading to a deterioration in sanding quality and possible belt breakage. So, we need to keep it in position and for this we have a belt position detection system that drives a pneumatic cylinder on the tension roller. The Open Frame Proportional Controller is therefore controlled and has the task of supplying air in a modulated manner into the pneumatic cylinder, in a closed loop cycle between the position of the belt, the cylinder and the Open Frame Proportional Controller.
In less than two weeks, with the support of Camozzi Automation’s technical department, Imeas were able to find the right solution to the problem, as well as configure and customise the Open Frame Proportional Controller for their machines.
"Customising a solution to such an extent is not easy," added Alessandro Speziali. "It takes a lot of experience and analysis to be sure you are doing the right task in the shortest possible time, particularly considering the additional challenge that the Open Frame Proportional Controller is mounted right next to the cylinder, from where the mechanical movement starts.
To conclude, the use of the Open Frame Proportional Controller in the positioner version with closed-loop control allows us to manage the positioning of the cylinder in a direct and precise way, lightening the workload of the PLC. Furthermore, the proposed solution allows the PID control algorithm, to be calibrated in a customised way, optimising and accurately dosing the kinetic forces involved and preventing oscillation caused by the weight of the belt guide roller rotating on itself. This leads to improved stability and control during the sanding process, ensuring optimal processing without compromising the quality of the end result.