Servomechanical discharging for online sheared part monitoring with high productivity
WZL researches potentials of discharging concepts for fine blanking in networked production
One challenge in fine blanking is to reliably remove the sheared parts from the tool space in the short time available. Particularly in highly productive processes, part removal must function reliably at high stroke rates.
Compressed air is often used for blowing out for this purpose. After cutting, the components are blown out of the tool space against a deflector with a blast of compressed air. From there they fall onto a chute and are transported out of the press. The components move in an uncontrolled manner and can receive undesirable impact marks. In addition, blowing out results in high compressed air consumption with high noise generation and impairment of the lubricant film on the sheet metal strip.
The Feintool XFT 2500 speed fineblanking press at the Laboratory for Machine Tools and Production Engineering WZL of RWTH Aachen University is suitable for high stroke rates of up to 140 strokes per minute. In addition, it is equipped with a drive designed for servomechanical part discharging, which allows sheared parts free of impact marks to be discharged separately by cavity in multiple drop fine blanking processes. When the tool is opened, a discharging slider is moved into the tool space, into which the sheared parts are ejected. It pulls the sheared parts in the correct position onto a chute or into channels located behind the tool. The sheared parts can thus be handled safely even at high stroke rates and transported away by a conveyor belt.
At the Laboratory for Machine Tools and Production Engineering WZL, defined part handling is used to obtain information from the process and to assign the produced parts to the measurement data from the process with true-to-stroke accuracy. Online sheared part analysis makes it possible to link data from the process with the process result and to use the sheared part quality as a variable for a control loop for process control. With this approach, boundary conditions for resilient process control were thus created at the WZL.
Use of the servomechanical discharger concept at the WZL
The servomechanical discharger was used at the WZL to discharge sheared parts in a two-up fine blanking process. For this purpose, a fine blanking tool was used that was developed in cooperation between the WZL and the Working Group Fineblanking and designed and manufactured by the project partner Precision Resource Canada Ltd. The WZL was also supported by the project partner Feintool Technologie AG in setting up and launching the servomechanical discharger.
In initial test series, stroke rates of 100 strokes per minute have already been realized with a sheet thickness of 6 millimeters. Particularly in fine blanking with cemented carbide punches, the servomechanical discharger ensures maximum process control and unimpaired lubricant film distribution on the sheet strip, as no compressed air is used. For more advanced research, a conveyor belt will be installed at the facility to realistically replicate industrial series production. Devices will be set up on the conveyor belt to allow online shreared part inspection to take place. In this context, the servomechanical discharger will be used to integrate sensors directly in the discharging slider and, for example, perform a lubricant film check or record quality-determining characteristics of the sheared part.
Image-processing AI methods, which were researched and developed at the WZL, are again integrated for the sheared part control. With these methods, it is possible to determine quality characteristics such as die roll, the smooth sheared portion, the sheared surface roughness, and the detection of defects. Surface analysis is also used to uniquely identify the sheared part by means of an individual digital fingerprint, thus enabling traceability of the individual component. Individual traceability is another requirement of modern production standards.
Advanced discharging technology enables valuable research into networked production at the WZL.