NX helps educate the next generation of manufacturers using digital twins of production processes

Careers for the environment

The Environmental Campus Birkenfeld (ECB) at Neubruecke, Germany, not far from the borders of Luxembourg, Belgium and France, is part of the Trier University of Applied Sciences. Among the 14 bachelor’s, four dual bachelor’s and 12 master’s degree programs offered, three specific programs teach students how to work with contemporary production technologies.

“Every year, 30 to 50 students register for our bachelor’s courses and dual bachelor’s studies in production technology and mechanical engineering as well as our master’s courses in digital product development,” says Stefan Hirsch, special assignment tutor for mechanical engineering at ECB. “They learn how end-to-end digitalization makes product creation more sustainable and more environment-friendly.”

ECB members created a hybrid machine for conventional and additive manufacturing using a 6-axis industrial robot, fitted with an extruder for 3D printing and a spindle for subsequent machining. The NC programs for this unconventional manufacturing unit are created and simulated using NX CAM and then transferred to the robot’s control unit.

CNC education using NX software

ECB students are required to work on a subject-specific project as well as an interdisciplinary project as part of their degree program. During their second semester, they start using NX™ software from product lifecycle management (PLM) specialist Siemens Digital Industries Software for computer-aided design (CAD) tasks. During their third and fourth semesters, they use the same software to perform strength calculations, applying the finite element method (FEM).

Students are then introduced to machine tools and learn the basics of numeric control (NC) programming. In master’s level courses, this includes creating programs in computer-aided manufacturing (CAM) and performing multi-axis machining simulations. Finding ways to utilize industrial robots for machining operations is one of the focal points of ECB’s education program. Another is integrating additive manufacturing with traditional machining. In both cases, the goal is to cover the entire process with one comprehensive NC program.

Covering the entire CAD/CAM process chain, including additive manufacturing and robotics in this comprehensive software suite, proves an accelerator to ECB’s mechanical engineering and digital product development courses. “When students start programming NC code for machine tools using CAM, they are already familiar with both the structure and the handling of NX software,” says Hirsch. “This means we can go a lot further than we could if they needed to get used to a new software tool as well.”

This enables ECB master’s course students to proceed to levels where they program CAM post-processors for complex machine tools as part of their education.

Using NX software to prepare parts for additive manufacturing allows printing perfectly round shapes (left) that would not be possible using the STL files typically employed there.

Creating an NX e-learning platform

ECB developed an editor that allows controlling the digital twin of a real machine tool in the virtual environment of a 3D simulation within NX CAM. It features online help screens as well as a post-processor for the common simulation engine (CSE) in NX CAD/CAM. Based on NX software, the ECB created a tool that allows didactic organizations to teach knowledge that is directly compatible with requirements in the real world. The G-code instruction set of vendor-neutral pedagogic algorithmic language (PAL) is used to program computerized numerical control (CNC) machine tools. Students can use the PAL language to create and simulate code that can be used to run NX CNC machine tools simulations. This plugin for NX software can be helpful for education in CNC-technology for machine oprators in the german dual education system.

Pushing the limits of CAM simulation

NX CAM software is not only used to create programs for NC machine tools, but also to perform realistic simulations of complex machines’ behavior. The aim is to avoid collisions, to assure safe and scrap-free operations and to verify machining performance in a virtual process. For product creation, ECB uses NX software to create an environment that makes them independent of the hardware used, enabling the university’s students, professors and lecturers to set the borderline between software models and reality where it is best suited. The outcome of such research and education work sometimes spins off as a software product or a new feature within Siemens software.

In an interdisciplinary project, ECB students used the NX Mechatronics Concept Designer to link a physics-based process simulation with a SIMATIC S7-PLCSIM advanced virtual programmable logic controller (PLC) from Siemens. This involved defining sensors and actors as well as controlling and monitoring their response time behavior. The PLC simula-tion and the physics simulation permanently exchange information. This paved the way to performing an end-to-end simulation using digital twins of both the mechanics and the PLC of the machine, enabling project participants to identify and eliminate errors early in the planning phase without building physical prototypes.

Other ECB students integrated the virtual NC kernel (VNCK) for NC code simulation with the NX CAM application to facilitate machine simulation of NC code. This integration facilitates more realistic simulations than other simulation methods without VNCK, such as using the common simulation engine (CSE). NX CAM software provides the human machine interface (HMI) of the Sinumerik NC control software in the simulation environment. This eases creating NC programs from 3D models using NX CAM in the digital process chain. Nevertheless, it was not enough to satisfy ECB’s elevated expectations.

“We extended the simulation capabilities so they now not only include the contents of the HMI screen but also mechanical controls such as push buttons or knobs,” says Hirsch. “This extension allows monitoring and control operations using truly machine-identical controls.”

Fully compatible additive manufacturing integration

In additive manufacturing, stereolithography (STL) files are used to represent part geometry. They describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. Based on a triangulated shape description, their use leads to suboptimal results with round surfaces. Also, the parts’ support structures are typically added in the frontend software of the generative production equipment. This means that the data cannot be reused for other purposes. Simulations used for FEM strength analyses, for instance, would be more realistic if the volume models used include all supporting structures of the part.

In a master thesis, ECB students programmed a software application in NX software that automatically creates the supporting structures of parts to be made using additive manufacturing. The aim was to take advantage of the software’s end-to-end data consistency. This allows combining additive manufacturing techniques and traditional machining. It also provides the ability to manufacture perfectly round shapes and include other CAD model attributes. Furthermore, engineers can use all part-related data for downstream work on the parts’ digital twins.

The ECB took advantage of this when they created a hybrid machine for conventional and additive manufacturing. It uses a 6-axis industrial robot, fitted with an extruder for 3D printing and a spindle for subsequent machining. The NC programs for this unconventional manufacturing unit are created and simulated solely using NX CAM and then transferred to the robot’s control unit.

“We cannot regard different manufacturing technologies separately if we aim at mass customization as proposed by the principles of Industry 4.0,” says Hirsch. “NX provides us with the consistent data model needed to combine their strengths.”

ECB is not only using NX software but many other solutions from Siemens Digital Industries Software such as products from the Teamcenter® portfolio, Simcenter™ software, Rulestream™ software, and Intosite™ software as well as the Tecnomatix® portfolio. Using NX software as the central software tool for engineering education from very early to the theses for the students’ final degrees is viewed as the main advantage for the students.

“ECB graduates are familiar with the leading-edge technology they will use during employment,” says Professor Peter Gutheil, dean of the environmental planning and technology department, ECB. “Their future employers benefit from their ability to seamlessly integrate existing industrial equipment with the concepts of Industry 4.0.”