A shortcut to the finished component

A scientist at the Fraunhofer IPA has found a way to save some of the numerous process steps from the first sketch to the finished component. CAD model, technical drawing and the settings on the machine are no longer necessary. All that designers and manufacturers still need are nine simple characters.

Between the first sketch and the finished component there are always numerous error-prone process steps and a lot of working time: first, the design department creates a three-dimensional CAD model. From this, the employee then derives a two-dimensional technical drawing and adds additional information: tolerances, fits, parallelisms, the roughness of the surface and so on. The CAD model and the technical drawing are then passed on to the machine operator. In the case of simple components, he makes the appropriate settings directly on the machine.

For more complex geometries, on the other hand, it is advisable to load the da- ta into CAM software, which then generates machine commands automatically. However, it is up to the manufacturer to decide which milling cutters and drills are suitable for machining the raw material and how the raw part should best be clamped.

The optimised procedure

Tobias Herrmann from the Lightweight Construction Technologies department at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) has now found a way to save some of these many process steps in design and production. The CAD model and technical drawing are replaced by a nomenclature of nine basic characters that can be used to specify everything that a milling machine is to implement. A worker writes these characters directly on the raw material with a pen, Figure 1: R5, for example, stands for a rounding with a radius of five millimetres, F20 for a 20-millimetre-wide chamfer or E10 for a milled-out area of ten millimetres, the exact shape and dimensions of which are specified by lines on the raw material.

In addition, there are nine conventions – for example, that only lines at an angle of 0°, 45° or 90° are permissible when drawing contours and features, or that the workpiece zero point is always located in the upper left corner from the machine operator‘s point of view.

Quality assurance measures

Once the raw material is labelled and clamped, it is scanned by a laser scanner. First, a rough scan is performed to determine the component position and size. This is followed by a fine scan in which the markings on the component are recorded. If there are problems, for example due to dirt on the component, the milling machine cleans the raw material automatically and then scans it again.

The recognised characters are interpreted and a vector graphic is derived from them. Then, within a few seconds, software translates the vector graphic into machine commands (NC code) and creates a reference component as a CAD model. The machine commands contain not only precise information about where the machine should do what with which tool, but the software also provides for tool changes. In other words, it prescribes where the machine has to use different milling cutters or drills.

A remedy for the shortage of skilled workers

Once the raw material has been processed (Figure 2), further quality assurance measures take effect: first, the workpiece is automatically cleaned to remove dust and chips. Then it is scanned once more by the laser scanner and checked to see whether the determined component shape matches the previously calculated reference component. If it is determined that not all machining steps have been carried out, for example because a drill broke during machining, a corresponding message is displayed to the machine operator. As soon as the operator has replaced the corresponding drill, the milling machine catches up on all machining steps that it was previously unable to perform correctly.

With these features, „EasyCNC“, as Tobias Herrmann calls his development, would not only be a shortcut to the finished machined component, but also a remedy for the prevailing shortage of skilled workers. For EasyCNC transfers the expertise of experienced designers and manufacturers into software commands. „The know-how for machining is thus no longer stored in the heads of the designers and manufacturers, but in the machine and software,“ says the researcher. „So in the future, unskilled or inexperienced personnel could be used on the machines.“

Intermediate control for access to existing machines

However, there are still a few unanswered questions to be clarified before this can happen. First and foremost: How do you gain access to old CNC machines? Because existing machines are often not designed for digitalisation. There is no provision for external systems to access them and give them commands. Herrmann is now trying to influence the machine commands via an intermediate control. CNC machines could then also access networks and databases by these means. In addition, this would allow instructions and directions to be passed on to the machine operator. To implement this, howe- ver, many tests on machine communication and system integration are still necessary.

Meanwhile, Herrmann‘s project partners at EVT Eye Vision Technology GmbH, a provider of machine vision solutions, continue to refine their deep learning algorithms. This is because the algorithms that recognise and classify the lines and characters on the blank in conjunction with a laser scanning system developed by EVT are essential for the further processing steps.

Reuss Maschinenbau GmbH & Co. KG, another project partner, is meanwhile developing the prototype of a milling machine into which EVT‘s laser scanning system is to be integrated together with equipment for component cleaning and the additional control connection. The project is scheduled to end on 30 September 2023.

The technical contact is Tobias Herrmann, tel. +49 711 970-1953, e-mail: tobias.herrmann@ipa.fraunhofer.de, www. ipa.fraunhofer.de.