Skip to content
  • Newsletter
  • About us
  • Contact
  • EN
  • DE
Menu
  • Newsletter
  • About us
  • Contact
  • EN
  • DE
Search
Close
  • Overview
  • Research
  • Here & now
  • Smart minds
Menu
  • Overview
  • Research
  • Here & now
  • Smart minds
  • Overview
  • Research
  • Here & now
  • Smart minds
  • Contact
  • Newsletter
  • About us
Menu
  • Overview
  • Research
  • Here & now
  • Smart minds
  • Contact
  • Newsletter
  • About us
Search
  • EN
  • DE
10. August 2022

Laser transmission welding of additively manufactured components

IPH | LZH | How can additively manufactured components be laser welded? Their layered structure makes the welding process more complicated than for conventionally produced parts. IPH and LZH are jointly researching how components can nevertheless be joined in a quality-assured manner.

Homogeneous thermoplastics can nowadays be joined together in a process-safe manner using laser transmission welding. This technology cannot be transferred to the joining of additively manufactured thermoplastic components without facing any difficulties. Due to the component structure resulting from the printing process, the welding process must be further developed. In the QualLa project, the Laser Zentrum Hannover e.V. (LZH) and the Institut für Integrierte Produktion Hannover gGmbH (IPH) are jointly researching how additively manufactured components can be joined with quality assurance using laser transmission welding.

Challenges in welding additively manufactured components

Laser transmission welding is a process for joining conventionally manufactured thermoplastics such as injection molded parts that has been established industrially since the 1990s. It involves the joining of two parts by means of a material bond. One of the joining partners must have a high degree of transmission, the other a high degree of absorption. During the welding process, the laser beam penetrates the transparent joining partner and is completely absorbed by the second joining partner near the joining plane. The energy of the laser is converted into thermal energy by the absorption and melts the plastics, joining them together (see Fig. 1).

Even with conventional thermoplastics, setting up the welding process requires a large number of trials to determine optimum process parameters for laser power and feed rate. Once the setup process is complete, the process parameters are set to the determined values and the components can be joined together. The homogeneity of the components resulting from the manufacturing process makes it possible to set the process parameters to constant values, as there are no major fluctuations in the joining process. For additively manufactured thermoplastic and transparent components, it is not possible to handle the welding process as described above – because additively manufactured components are not homogeneous.

Additive manufacturing and inhomogeneous component structure

The additively manufactured thermoplastic components being investigated in the research project are produced at IPH using fused deposition modeling (FDM, German: Schmelzschichtung). In this manufacturing process, a filament of thermoplastic is fed into a print head and melted, extruded through a nozzle and applied layer by layer to a print bed (see video). The applied layers fuse together and form a bond.

Due to the layer-by-layer structure in the additive manufacturing process, the components have an inhomogeneous structure. This is due to process variations in the printing process. Reasons include:

  • The liquid plastic is never deposited in the same place when the print head is moved.
  • Material distortion occurs when the plastic solidifies.
  • The extruded material quantity is not constant and inaccurate.

Underfilled and overfilled areas cause local defects in the additively manufactured component in the form of bubbles and air inclusions (see Fig. 2) as well as beads, and lead to component warpage. These inhomogeneities lead to the need to control the laser welding process depending on the existing component structure and resulting transmission.

Determination of transmission for additively manufactured components

For homogeneous components, the transmission depends primarily on the component thickness, since other material- and process-related influencing factors can be considered constant. In the case of additively manufactured components (see Fig. 3), further influencing variables resulting from the manufacturing process are added. The LZH and IPH have jointly identified corresponding influencing variables from the additive manufacturing process in order to model transmission. Current experiments show that the following influencing variables have a major effect on transmission during the additive manufacturing process:

  • Thickness of the component at the area to be welded.
  • Layer thickness
  • Line width
  • Flow
  • Printing speed

In addition, the influences of the printing temperature, the pattern and the material were investigated in further tests at IPH and LZH. Using software specially developed for this purpose at IPH, the expected transmission can be calculated on the basis of the input variables from the printing process. This enables a statement to be made about the weldability (see Fig. 4).

Determining the optimum process parameters

After determining the transmission based on the influencing variables from the additive manufacturing process, it is determined whether the component is weldable by laser. If this is the case, the process parameters for the laser welding process are determined in the subsequent step.

The optimum parameters for this purpose are determined in welding tests at LZH. Welding specimens with different laser powers and welding speeds are produced and tested in tensile tests. The maximum tensile force achieved serves as a quality characteristic and is used to create a laser process model based on the associated measured transmission and the process parameters from the additive manufacturing process.

With the help of the model, the optimum parameters for laser power and welding speed are determined, stored in an expert system and output via the software developed at IPH (see Fig. 5). This eliminates the need for time-consuming parameter studies to determine optimum process parameters. High-quality joining of the components can thus be ensured.

Long-term goal: Intelligent process monitoring

Work is currently being carried out at LZH on a measurement method to measure the transmission of the additive components in a simple way with local accuracy. The results from the tests will then be used at IPH to control the welding process with spatial accuracy using the laser process model.

In the long term, the LZH and IPH are pursuing the goal of installing an intelligent process monitoring system that monitors the welding process in real time and provides operators with feedback on the quality of the welding process. This will serve as the basis for further development of the laser process.

by Torben Mente and Julian Kuklik

Similar posts

  • Printing complex glass structures in 3D using the laser
  • RFID tags: 3D printing opens up new possibilities
  • Additive manufacturing in microgravity using laser metal deposition

At a glance

  • Laser transmission welding of additively manufactured components is made possible
  • Additively manufactured components are optimally adapted to the welding process
  • Software determines optimum laser power and welding speed
  • High quality of the joint is ensured
laser transmission welding
Fig. 1: Additively manufactured sample with visible pilot laser during laser transmission welding. (Photo: LZH/IPH)
transverse section additively manufactured component
Fig. 2: Transverse section of an additively manufactured component with inhomogeneous structure and air inclusions. (Photo: LZH)
additively manufactured transparent sample
Fig. 3: Additively manufactured transparent sample: the IPH logo is visible through the sample. (Photo: IPH)
QualLa software
Fig. 4: Output of expected transmission based on input variables from the additive manufacturing process (German language). (Photo: IPH)
QualLa software
Fig. 5: Output of the process parameters for laser transmission welding (German language). (Photo: IPH)
Previous
Next
The video shows FDM 3D printing in fast motion: molten plastic is deposited layer by layer onto a print bed. FDM stands for Fused Deposition Modeling, a type of additive manufacturing. (Video: IPH)

Contact

Torben Mente, M.Sc.

+49 (0)511 279 76 236

mente@iph-hannover.de

qualla.iph-hanover.de

The IGF project QualLa (No. 21571 N) of the Research Association Quality (FQS) is funded via the German Federation of Industrial Research Associations (AiF) in the programme of Industrial Collective Research (IGF) by the Federal Ministry for Economic Affairs and Climate Action (BMWK) based on a decision of the German Bundestag.

This Page

drucken

recommend

  • tweet 

Similar posts

  • Printing complex glass structures in 3D using the laser
  • RFID tags: 3D printing opens up new possibilities
  • Additive manufacturing in microgravity using laser metal deposition

This Page

drucken

recommend

  • tweet 

ISSN 2198-1922 | Legal Information | Privacy notice | Article Sitemap