Research group

Wood and Composites Machining

Research projects of Wood and Composites Machining

Research projects of Wood and Composites Machining

Prototypes of a wall system with insulating slots
Prototypes of a wall system with insulating slots

Production and joining optimization for multi-storey exterior walls made of squared solid timber with slots

The enormous challenge facing the building and construction industry is how to reduce the consumption of resources, emissions and pollution in all areas of the process chain from raw materials production, the use in the building up to the recycling at the end of the life cycle. As wood is a renewable, local building material, it offers very good prerequisites for an efficient and energy-saving use of resources.

In the predecessor project, a novel wooden construction was developed only consisting of squared solid timber as supporting and insulating material. Thus, it is only made of wooden components and joints, requiring no adhesives for joining as well as no additional insulation. To evaluate the system, a full-scale microhouse (IBA Timber Prototype House) was realized successfully for the International Building Exhibition (IBA) Thüringen.

The intention here is to make these characteristics applicable to multi-storey residential and office buildings within an optimized system. By further developing the profile of the squared solid timber and the prototypical machining process into a production process applicable in industry, it is intended to increase both the production efficiency and the airtightness of the component layers.

In the joint project "Economical, high-insulation, layer-reduced, mono-material, adhesive-free, digitally produced solid timber construction" with the Institute for Computational Design and Construction (ICD) at the University of Stuttgart, the task of the IfW is to optimize the production of the wooden elements. The goal of the production optimization is to contribute to realizing the high-performance cutting of solid timber by means of machining centres. The centre of attention here is on the integral complex out of „workpiece, tool and production process parameters“, looking at it from the aspects of process effectiveness. By conducting experimental cutting tests, it is planned to obtain findings about process parameters as well as tool characteristics and to take them into account in the design of an optimum machining strategy.

Funded by the Federal Ministry of the Interior, Building and Community (BMI) within the research funding “Zukunft Bau“.

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The data flow of the „digital wood laboratory“ at the IfW
The data flow of the „digital wood laboratory“ at the IfW

Implementation of an IoT platform for digitalizing the machine hall for wood machining

The progressive digitalization and automation in industry offer versatile, new possibilities for networked and intelligent machining. For that purpose, the machining centres at the IfW were made fit by means of an IoT platform for a SmartLab („digital wood laboratory“) in the course of a trilateral „Industry 4.0“ project. This enables the merging of diverse data sets, which can be connected with each other by means of intelligent analytical methods. Thus it is possible to draw conclusions about the respective machine conditions and hence about the production process as well as to derive predictions. This transformation is based on the cloud-based technology platform by Tapio and the central data acquisition unit by Schneider Electric SE.

In order to further digitalize the machine hall at the IfW, a central data acquisition unit was installed to collect the data of several measurement stations, process them and make them visible via different output mediums. For that purpose, a sensor system was implemented to establish the climate data in the machine hall and control the limiting values so that it is possible to monitor environmental influences on machines and facilities. The energy consumption of the central wood chip and dust exhaustion system as well as of the CNC machining centres is measured by means of wattmeters so that conclusions about the utilization can be drawn. This is necessary because there is no other way of measuring the power consumption of the present machines. The present machines were connected to the IoT according to the BrownField approach.

The machine and sensor data are recorded here in the form of OPC UA items by an OPC UA server so that they can be read out by a cloud connector. It forwards these data to the digital ecosystem, which makes them available for various applications. The MachineBoard, an application by Tapio, was used exemplary in the SmartLab. The MachineBoard runs as an app on mobile terminals (smartphones, tablets, smartwatches, etc.) and visualizes the information about the machining centres and the machine hall.

The special quality of the solution realized at the IfW is that the machines and facilities already implemented can be supplemented not only by numerous other machines and test stands in the machine hall but also by further sensor and actuator systems. Thus it is possible to flexibly adjust and expand the digitalization of the machine hall to the changing requirements, e.g. in test procedures. For any application, it is possible to choose sensors or read data directly out of the machine. In contrast to industrial production, the project described here is not focused on increasing the productivity but on establishing basic data, such as e.g. the spindle utilization, the variance in rotational speed, the machine condition, etc. Moreover, the centre of attention here is on the testing of the IoT platform and the generation of new knowledge, from which industrial production can derive benefit in turn.

We are grateful to Tapio and Schneider Electric SE for their previous and continuing support in the realization of the BrownField  approach for digitalizing the machine hall at the IfW.

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Sample workpiece
Sample workpiece

Increasing the efficiency of chip collection in the machining of composites, wood and plastics

With an average of 45 %, the suction system has by far the greatest demand for electrical energy in woodworking companies. In the past, the focus was primarily on increasing collection rates in order to comply with legal limits, but today energy efficiency is becoming more and more important in production.

The basic objective of this research project is to significantly reduce the energy demand of the suction systems in machines for woodworking as well as for the machining of fibre composites and plastics. Two paths are being taken to increase the energy efficiency of suction systems:

- self-regulating decentralized suction system

- chip collection device close to the tool

For an energy-efficient dust and chip collection of material removal machine tools, both approaches are to be combined.

Within the framework of the research project, a sample process or sample workpiece was developed for the evaluation of detection levels for CNC machining centres. Investigations with the sample workpiece showed that the degree of detection depends not only on the air speed inside the hood but also on the size distribution of the chip and dust fractions.

Funded by: Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF) within the framework of the programme for the promotion of joint industrial research (IGF) with funds from the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag

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Simulation of air flow
Simulation of air flow

Low-noise circular saw blades in the machining of wood and engineered wood products

Noise is still one of the most common health hazards in the woodworking industry. The noise level of circular saws is almost always at or above the permissible noise limits. However, the strategies pursued to date to reduce noise emissions do not significantly change the acoustic behaviour of a circular saw blade, as they are more likely to combat the consequences rather than the mechanism by which the sound is generated when circular saw blades rotate.

Investigations at the IfW have shown that today's circular saw blades have an oversized chip space so that safe chip removal is guaranteed in any case during cutting. Within the scope of the research work, design changes to the blade and tooth shape geometry are to be investigated, which, for example by reducing and optimizing the chip spaces, cause less air turbulence. The focus is on the influence of different geometry parameters such as tooth back length, tooth shape or chip space radius on the acoustic behaviour of a circular saw blade. The aim is to influence the flow behaviour with regard to a reduction of the noise emissions by suitable measures in the design of the circular saw blades without essentially impairing the machinability of the circular saw blade. The project is based on experimental machining investigations, acoustic measurement analyses and aeroacoustic simulations.

Funded by: German Research Foundation (DFG)

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Separating protective device
Separating protective device

Increasing work safety on stationary woodworking machines through machine enclosures made of plastics and fibre composites

The trend towards complete machining through process integration is leading to an increasing demand for additional auxiliary units in woodworking machines. Due to these demands, however, the machine enclosures of the machining centres must be dimensioned ever larger in order to accommodate the large number of units. Furthermore, these aggregates inevitably lead to an increase in the masses to be moved. In order to counteract this trend, the use of lightweight materials for machine enclosures is becoming interesting, although these materials are not considered in the current EN 848-3 standard for retention capability.

The aim of the research project is to find suitable lightweight materials that can be used as separating protective devices as an alternative to existing solutions, which are usually made of sheet steel. For this purpose, the safety-related properties (including retention capacity) of these weight-reduced materials are to be determined. Another aim is to improve the acoustic behaviour through the new material, since the machine enclosure shields the prominent sound sources (spindle, cutting point).

By systematically investigating and determining alternative enclosure materials, it will be possible to use these materials later on without additional extensive and expensive safety tests by manufacturers as early as the design phase. This demonstrates and documents the major economic and ecological advantages over existing solutions.

Funded by: Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF) within the framework of the programme for the promotion of joint industrial research (IGF) with funds from the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag

Concept for a tool body of CFRP
Concept for a tool body of CFRP

Development of lightweight tool bodies with highly dynamic load-carrying capacity for the machining of wood and engineered wood products

The trend towards ever higher cutting speeds in the machining of wood and engineered wood products requires increasingly higher tool rotational speeds and tools capacble of machining bigger parts. The increase in geometric dimensions is always accompanied by an increase in the mass of the tools. This directly influences the dynamic behaviour of the machine tool and the tool spindle. In moving axes (e.g. in CNC machines for window machining), heavy tools sometimes cause high acceleration forces. The critical rotational speeds of spindles are also reduced by heavy tools, thus limiting the maximum rotational speeds.

In order to meet the trend towards ever higher rotational speeds, a tool with a basic body made of carbon fibre composite is to be developed in the research project. This material is characterized by excellent specific stiffness and damping properties, as required for the use of tools in the machining of wood. In the IGF project 20128N "Development of lightweight tool bodies with highly dynamic load-carrying capacity for the machining of wood and engineered wood products", funded by the German Federal Ministry for Economic Affairs and Energy (BMWi), solutions will be worked out to apply these advantages to tools. In the project, a prototype tool with a lightweight base body for planing tasks is to be developed. The pre-competitive development work will work out questions regarding suitable manufacturing processes for the basic body and the connection of cutting and interface elements to it.

The process development of prototypes for tool bodies designed to withstand high loads is carried out by the German Institutes for Textile and Fiber Research (DITF), whereas the tool-related developments and investigations are conducted by the Institute for Machine Tools (IfW). The knowledge gained in the project will create the suitability of basic processes and concepts for the production of tools with basic bodies made of fibre composite, which can then be implemented by the members represented in the working group from the industrial side. Due to the largely small and medium-sized textile processing enterprises as well as the woodworking machinery industry, new markets will be opened up for all participating companies. At the same time, the efficiency of tools in woodworking is increased by lighter tools, so that technological advantages are developed.

Funded by: Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF) within the framework of the programme for the promotion of joint industrial research (IGF) with funds from the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag

Continuous process chain
Continuous process chain

Simplified Robotic Woodworking (SiRoWo)

The use of industrial robots (IRs) for machining tasks is becoming more and more widespread in production. The reason for this is that an IR has a wide operating range at comparatively low investment costs compared with machine tools. In the machining of metallic materials, it has shown, however, that IRs often cannot achieve the close manufacturing tolerances in metalworking due to their great dynamic compliance.  This situation is clearly better in the machining of non-metallic materials such as wood and fibre composite materials, since the specific forces are lower and the manufacturing tolerances are greater. For that reason, IRs are predestined for many fields of application in the woodworking industry.

It is necessary to develop a hardware concept suitable for everyone so that IRs can be widely applied in the trade. This requires a programming environment which is orientated towards various tasks of a workshop and can be operated intuitively. A database is also planned to help with supplying operations and production steps, sketches, industrial design and material requirements with few clicks. Apart from software-related problems, the project is also focused on the development of hardware components such as clamping and suction.

The IfW is working on the subproject „Development and integration of strategies for the machining of wood and composite materials with robots and a suction device for a fully integrated robot machining cell”. The goal of this subproject is to create the technological requirements for the different machining processes of wood and composite materials and to develop the necessary peripherals for removing chips and dust as well as for clamping the workpieces. Within the framework of this subproject, the considered machining processes are to be adapted to the kinematic conditions of an industrial robot. Moreover, the knowledge required for an intelligent continuous-path planning of robot motions and the necessary indicators of process monitoring are to be established by means of experimental analyses and then supplied to the project partners.

Funded by the funding initiative „KMU-NetC“ from funds of the Federal Ministry of Education and Research by order of the German Bundestag

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This picture showsKamil Güzel
Dipl.-Ing.

Kamil Güzel

Team leader Wood Machining

This picture showsMatthias Schneider
Dipl.-Ing.

Matthias Schneider

Team leader Composite Materials Machining

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