scholarly journals Methods and procedure of referenced in situ control of lateral contour displacements in additive manufacturing

2021 ◽  
Vol 10 (2) ◽  
pp. 219-232
Author(s):  
Martin Lerchen ◽  
Jakob Hornung ◽  
Yu Zou ◽  
Tino Hausotte
Keyword(s):  
Additive Manufacturing ◽  
Measurement Data ◽  
Detection Algorithm ◽  
Contour Detection ◽  
Layer By Layer ◽  
Powder Bed ◽  
In Situ Control ◽  
Melting Pool ◽  
Lateral Displacements

Abstract. Additive manufacturing technologies are further developing from prototype to serial production. This trend requires rising challenges to the process-accompanying quality assurance. Optical in situ quality control approaches show great potential to generate accurate measurement data, which are essential for feedback control. If a reliable referencing concept for the layer-by-layer measured data is guaranteed, contour information can be used during the manufacturing to correct occurring geometrical deviations. Within this scientific study, two methods of optical, referenced in situ control of lateral displacements of additive manufactured contours are presented. In the first approach the 2-D contour of the melting pool is analysed in relation to a position-stable reference system implemented in the powder bed. The second approach uses the translucent contour of deeper layers covered with powder as a reference. Within the image evaluation several pre-processing steps like calibration, undistortion, rectification, illumination correction and low-pass filtering are essential for reliable and correct geometric measurements. The following adapted contour detection and position determination of the referenced melting pool contours are based on an extended edge detection algorithm according to Canny (1986). With the evaluation of further manufacturing layers of already lowered powder bed levels, it is possible to specify the influence of powder application on geometrical displacements separately. This is done by a comparison of the position of the detected powder-covered melting pool contours with the previously applied melted region. Consequently a better understanding of lateral contour displacements within the additive manufacturing process is the goal, which is important for a process-accompanying correction of geometrical deviations.

scholarly journals Referencing of powder bed for in situ detection of lateral layer displacements in additive manufacturing

2021 ◽  
Vol 10 (2) ◽  
pp. 247-259
Author(s):  
Martin Lerchen ◽  
Julien Schinn ◽  
Tino Hausotte
Keyword(s):  
Additive Manufacturing ◽  
Data Acquisition ◽  
Reference System ◽  
Contour Detection ◽  
In Situ Monitoring ◽  
Measuring System ◽  
Layer By Layer ◽  
Powder Bed ◽  
Measurement Systems

Abstract. An increasing number of additive manufacturing (AM) applications leads to rising challenges for the process-accompanying quality assurance. Beside post-processing measurement systems, in situ monitoring systems in particular are currently requested to ensure feedback controlling during AM processes. For data acquisition and subsequent evaluation, a high data quality is of importance. It depends on a high resolution and accuracy of measurement systems, adapted measurement conditions and a reference to the powder bed or component for geometric measurements. Within this scientific study, a new reference system has been implemented into the powder bed to reduce measurement deviations by an abbreviated metrological loop. After data acquisition and image processing layer by layer, the position stability of the reference system has been analysed in relation to the optical measuring system. Based on a contour detection of the reference markers, the evaluation of geometrical process deviations is presented as an essential basis for a closed-loop controlling system. Thermally induced and mechanical drifts within the manufacturing process can be verified by the reference system in the powder bed. As an outlook, two methods are suggested for a process-accompanying referenced detection of the melting pool and resulting contour displacements during additive manufacturing.

scholarly journals A STRUCTURED APPROACH TO REDUCE DESIGN ITERATIONS IN ADDITIVE MANUFACTURING

2021 ◽  
Vol 1 ◽  
pp. 231-240
Author(s):  
Laura Wirths ◽  
Matthias Bleckmann ◽  
Kristin Paetzold
Keyword(s):  
Additive Manufacturing ◽  
Spare Parts ◽  
Design Guidelines ◽  
Final Part ◽  
Layer By Layer ◽  
Powder Bed ◽  
Batch Sizes ◽  
Manufacturing Technologies ◽  
Structured Approach ◽  
Design Freedom

AbstractAdditive Manufacturing technologies are based on a layer-by-layer build-up. This offers the possibility to design complex geometries or to integrate functionalities in the part. Nevertheless, limitations given by the manufacturing process apply to the geometric design freedom. These limitations are often unknown due to a lack of knowledge of the cause-effect relationships of the process. Currently, this leads to many iterations until the final part fulfils its functionality. Particularly for small batch sizes, producing the part at the first attempt is very important. In this study, a structured approach to reduce the design iterations is presented. Therefore, the cause-effect relationships are systematically established and analysed in detail. Based on this knowledge, design guidelines can be derived. These guidelines consider process limitations and help to reduce the iterations for the final part production. In order to illustrate the approach, the spare parts production via laser powder bed fusion is used as an example.

Towards process consistency and in-situ evaluation of porosity during laser powder bed additive manufacturing

2020 ◽  
Vol 25 (8) ◽  
pp. 679-689
Author(s):  
J. Raplee ◽  
J. Gockel ◽  
F. List ◽  
K. Carver ◽  
S. Foster ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Powder Bed

scholarly journals Effects of Positioning Conditions on Material Properties In Powder bed Fusion Additive Manufacturing

2021 ◽  
Author(s):  
Mevlüt Yunus Kayacan ◽  
Nihat Yılmaz
Keyword(s):  
Additive Manufacturing ◽  
Material Properties ◽  
Layer By Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Cooling Rates ◽  
Powder Bed ◽  
Manufacturing Technologies ◽  
Average Size ◽  
Hardness Values

Abstract Among additive manufacturing technologies, Laser Powder Bed Fusion (L-PBF) is considered the most widespread layer-by-layer process. Although the L-PBF, which is also called as SLM method, has many advantages, several challenging problems must be overcome, including part positioning issues. In this study, the effect of part positioning on the microstructure of the part in the L-PBF method was investigated. Five Ti6Al4V samples were printed in different positions on the building platform and investigated with the aid of temperature, porosity, microstructure and hardness evaluations. In this study, martensitic needles were detected within the microstructure of Ti6Al4V samples. Furthermore, some twins were noticed on primary martensitic lines and the agglomeration of β precipitates was observed in vanadium rich areas. The positioning conditions of samples were revealed to have a strong effect on temperature gradients and on the average size of martensitic lines. Besides, different hardness values were attained depending on sample positioning conditions. As a major result, cooling rates were found related to positions of samples and the location of point on the samples. Higher cooling rates and repetitive cooling cycles resulted in microstructures becoming finer and harder.

scholarly journals Correlation between surface texture and internal defects in laser powder-bed fusion additive manufacturing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Makiko Yonehara ◽  
Chika Kato ◽  
Toshi-Taka Ikeshoji ◽  
Koki Takeshita ◽  
Hideki Kyogoku
Keyword(s):  
Additive Manufacturing ◽  
Surface Texture ◽  
In Situ Monitoring ◽  
Mean Square ◽  
Powder Bed Fusion ◽  
Internal Defects ◽  
Powder Bed ◽  
Texture Parameters ◽  
Areal Surface

AbstractThe availability of an in-situ monitoring and feedback control system during the implementation of metal additive manufacturing technology ensures that high-quality finished parts are manufactured. This study aims to investigate the correlation between the surface texture and internal defects or density of laser-beam powder-bed fusion (LB-PBF) parts. In this study, 120 cubic specimens were fabricated via application of the LB-PBF process to the IN 718 Ni alloy powder. The density and 35 areal surface-texture parameters of manufactured specimens were determined based on the ISO 25,178–2 standard. Using a statistical method, a strong correlation was observed between the areal surface-texture parameters and density or internal defects within specimens. In particular, the areal surface-texture parameters of reduced dale height, core height, root-mean-square height, and root-mean-square gradient demonstrate a strong correlation with specimen density. Therefore, in-situ monitoring of these areal surface-texture parameters can facilitate their use as control variables in the feedback system.

Additive Manufacturing of Nickel-Based Super Alloys for Aero Engine Applications

2020 ◽  
pp. 48-70
Author(s):  
Raja A. ◽  
Mythreyi O. V. ◽  
Jayaganthan R.
Keyword(s):  
Additive Manufacturing ◽  
Complex Geometry ◽  
Source Parameters ◽  
Raw Material ◽  
Layer By Layer ◽  
Powder Bed ◽  
Complex Design ◽  
Direct Energy ◽  
Second Phases ◽  
Metal Addition

Ni based super alloys are widely used in engine turbines because of their proven performance at high temperatures. Manufacturing these parts by additive manufacturing (AM) methods provides researchers a lot of creative space for complex design to improve efficiency. Powder bed fusion (PBF) and direct energy deposition (DED) are the two most widely-used metal AM methods. Both methods are influenced by the source, parameters, design, and raw material. Selective laser melting is one of the laser-based PBF techniques to create small layer thickness and complex geometry with greater accuracy and properties. The layer-by-layer metal addition generates epitaxial growth and solidification in the built direction. There are different second phases in the Ni-based superalloys. This chapter details the micro-segregation of these particles and its influence on the microstructure, and mechanical properties are dependent on the process influencing parameters, the thermal kinetics during the process, and the post-processing treatments.

scholarly journals In-situ characterization of laser-powder interaction and cooling rates through high-speed imaging of powder bed fusion additive manufacturing

2017 ◽  
Vol 135 ◽  
pp. 385-396 ◽  
Author(s):  
Umberto Scipioni Bertoli ◽  
Gabe Guss ◽  
Sheldon Wu ◽  
Manyalibo J. Matthews ◽  
Julie M. Schoenung
Keyword(s):  
Additive Manufacturing ◽  
High Speed ◽  
Powder Bed Fusion ◽  
In Situ Characterization ◽  
High Speed Imaging ◽  
Cooling Rates ◽  
Powder Bed

scholarly journals Sensor-Based Additive Manufacturing Technologies

2021 ◽  
Vol 12 (3) ◽  
pp. 3513-3521
Keyword(s):  
Additive Manufacturing ◽  
Wearable Sensors ◽  
Sensor Technology ◽  
Layer By Layer ◽  
Environmental Sensors ◽  
Direct Energy Deposition ◽  
Powder Bed ◽  
Direct Energy ◽  
Building Components ◽  
Manufacturing Technologies

Additive manufacturing is the term that uses the CAD data to build components layer by layer; it is also termed layered manufacturing or 3D printing. The major advantage of additive manufacturing is the capability of building components without the use of molds or tools. Five major categories of AM processes include Powder Bed Fusion (PBF), Direct Energy Deposition (DED), Material Jetting (MJ), Binder Jetting (BJ), and Sheet Lamination (SL). The sensor may be defined as a device that responds to a physical stimulus and transmits a resulting impulse. Sensor technology has been widely adopted in advanced manufacturing, aerospace, biomedical and robotic applications. Commonly used sensors are temperature sensors, strain sensors, biosensors, environmental sensors, and wearable sensors, etc. Additive manufacturing technologies can fabricate sensors and microfluidic devices with less labor. This paper focuses on various sensors developed by additive manufacturing processes, and their practical application for the particular purpose is reviewed.

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