What is the CO2 footprint of a machine tool? Anyone who wants to prepare a sustainability report for a manufacturing company or document progress in greenhouse gas emissions will probably pass this question on to the supply chain. The answer is not easy: After all, a machine tool consists of tens of thousands of individual parts, including purchased materials and preliminary products. There is a huge variety of products, ranging from compact milling machines for intricate clock mechanisms to presses for aircraft parts: Almost every machine is unique. How do you arrive at a value that is also valid and comparable for accountants?
"The CO2 assessment itself is already complex," says Prof. Felix Hackelöer from the Institute for Automation and Industrial IT at Cologne University of Applied Sciences, "and it is very complex for machine tools." Hackelöer is a member of a group of experts formed on the initiative of the VDW (German Machine Tool Builders' Association). The group was faced with the task of developing so-called Product Category Rules (PCR) for machine tools. This involves a calculation approach that can be used to determine the product carbon footprint (PCF), i.e. the CO2 of a machine tool. Also on the team: Experts from six VDW member companies - Chiron, DMG Mori, Grob, Heller, Schuler and United Grinding - as well as experts from the VDW and VDMA departments involved in standardization. The aim should be to use a VDMA standard to create a guideline that can ideally be developed into an ISO standard.
Premise: Ensure applicability also for SMEs
The project group met for the first time in February 2024. There was a short discovery phase in which different experiences were reported and possible approaches were discussed. Jörg Süssdorf, Global Quality Manager at Schuler Pressen, Göppingen, reports that agreement was quickly reached on a few key points: "Many companies long for a simple, well-structured paper," he says. "We agreed that our rules must also be able to be implemented for SMEs without a great deal of bureaucracy." The results should be comparable and internationally adaptable. However, they should also make it possible to recalculate or check if market participants appear to be less trustworthy. Finally, the goal was set that the PCF could be calculated in a single day using the method to be developed. Until now, three months at best was considered realistic. "If all these requirements are met," says Süssdorf, "there is a clear benefit for companies."
The method: Just don't get too lost in the details
The PCF includes all greenhouse gas emissions caused by a product in the various phases of its life cycle. In the first step, the VDW project group agreed on the cradle-to-gate approach, i.e. an approach that focuses on resources, the manufacture of preliminary products and finally the production of the end product - right up to the point at which the machine leaves the manufacturer's factory.
Henning Bornkessel, Senior Manager Sustainability & Process Management at DMG Mori, Bielefeld, explains the reasons for this approach. "The decisive factor for us was the customer perspective," he says. "Cradle-to-gate is a well-defined area for which we can make reliable statements. This is exactly what our customers are interested in for their CO2 footprint."
The "most heated" discussions in the expert group were - as they say - about the question of how much detail was needed. "Higher-level approaches require a detailed consideration of up to 99 percent of a machine's mass," says Felix Hackelöer and emphasizes: "This is not possible with machine tools." According to the Cologne scientist, the question arose as to what sense it makes to calculate the PCF down to the smallest washer. The aim of the working group was therefore to develop a methodology for the PCF of machine tools that combines good accuracy with reasonable effort.