Research

INNO-KOM 49MF190165

Abstract

The development of a finishing technology for textiles to be used as substrate for Fused Deposition Modelling (FDM) prints is the aim of the present project PrintTexFinish. FDM is more and more used to create functional and decorative surfaces on products with outer fabrics like sneakers and other sportswear. Furthermore, FDM offers novel opportunities to integrate electronic devices in textiles to design interactive smart electronic textiles. The FDM printed structures stabilises interactive the electromechanic and cover sensitive electronic devices as for example the power supply driven by chargeable batteries. The basic requirement for such printed structures is an excellent adhesion of the FDM print to the textile substrate.

Problem

The aim of this research project is to develop a technology for the defined surface modification of textile fabrics for 3D printing processes as a basis for the adhesive application of 3D printed structures to textiles. To this end, the potential of otherwise used technologies for functionalising textile substrates by applying thin layers to improve adhesion is being analysed and utilised. The adhesive layer created with this surface modification enables the subsequent printing of textile surfaces with 3D structures with very high adhesive strength without having to intervene on the 3D printer or in the printer control. It thus significantly increases the range of substrate choices for users of standard printers. Within the scope of the project, the FDM process is used as the most common 3D printing process. At TITV Greiz, a CNC portal milling machine with a 3D print head from Stepcraft and a standard printer (CubePro Trio from 3D Systems Inc.) are available for this purpose. The adhesive layer is created in such a way that the textile properties in the areas left free by 3D-printed structures are not lost and remain in their original state without restriction. This means that the surface modification of the textiles is either only partial in the areas where 3D-printed structures are applied or is designed in such a way that the textile properties are not affected. With the developed technology, the textile surface is modified so that the printed structures adhere to the surface with an adhesive strength of at least 50 N/cm².

Solution

In order to achieve the goal of applying adhesion-promoting layers for 3D printing on textiles, the following solution approach has been successfully implemented. The structure of the adhesive layer to be developed is such that it forms a firm, non-detachable mechanical bond with the textile surface. The foundations for the implementation of this research project have already been laid at TITV Greiz in several industrial projects and in numerous preliminary tests on a laboratory scale. In order to be able to implement these findings on an economically viable scale, further investigations are necessary. Based on the knowledge already gained in the preliminary tests, four different technological approaches are emerging, which are to be investigated in more detail within the scope of this research project:

• Application of embroidered structures with special thread materials,
• Application of powder technology in combination with laser fixation,
• Application of classical coating and
• Development of special 3D print structures.

A wide variety of hot melt adhesive fleeces (hot melt webs) have been investigated on textiles as a bonding layer between textile and FDM print. To characterise the adhesion, standardised FDM test prints were designed and subjected to an adhesion test. The test results show that with the help of thermoplastic finishes on the selected textile structures, the required release force of 50 N can be exceeded.

Results and Applications

The textiles equipped with hot-melt adhesive fleece enable homogeneous deposition of the melted thread trace with very good adhesion to the textile substrate when this is homogeneously heated at a temperature adapted to the melting point of the polymer used for printing. In this way, 3D prints that firmly adhere to the textile could be demonstrated in the first tests. The test results already show that 3D FDM prints with the following properties can be produced on the equipped textiles in this way:

• Adhesion of 3D-printed structures to the textiles by means of the FDM process
• Adhesive force of the printed structures higher than the pull-out force of the fibres from the textile surface; at least 50 N/cm²
• No or visually appealing visibility of the adhesive layer on the reverse side of the textile
• Preservation of textile properties on unprinted areas
• Roll-to-roll and individual production possible
• Reproducibility of the technical properties of the adhesive layer with a maximum deviation of +/- 5% in individual properties
• Textile surface must not warp when applying the adhesive layer
• Adhesive layer thickness maximum 500μm

Fig. 1a: test body printed on textile substrate for 1b: determining the delamination force for optimum adhesion in the subsequent application such as the 1c: switching matrix with 3d printed dimple structure and enclosure of the evaluation electronics.

We thank the Federal Ministry for Economic Affairs and Energy for the funding based on a resolution of the German Bundestag.