VL IX - Properties and Measurement Techniques

What Density Analysis are used in AM

• Archimedean Density

• Optical Method

How does the Archimedean Method work

1. Weight in air

2. Weight in liquid

Formel for Archimedean Method

Pros and Cons Archimedean Method

Pros:

• Simple

• Entire Volume of samle

Cons:

• No information about about type

• distribution and shape of structural porosities

How does Optical Method work for the Density

• Micrographs photographed in light microscope

• Images binarized into material or pore

• Ratio between pixels gives relative density

Pros and Cons of Optical density

Pros:

• Information about Size

• Shape and pore distribution

Cons:

• Other defects can be mistaken as pores

• Destructive

Relative densities for different AM Processes

• PBF-LB/M: >99%

• BJT: ca.95%

• MEX: up to 95%

• DED: ca. 99%

Density Green body BJT and MEX

50-60%

Which Density measurement gives a higher density

Depends on boundary conditions:

• For high density (optical)

• For low density (Archimedian)

How should surface qualities and densities be compared

Only between same measurement techniques

Name Optical Areal Surface Measurement

• Confocal Laser Scanning Microscopy

• Focus Variation

• Fringe Projection

How does a Profilometer work

• Probe Tip drawn ver sample surface

• Displacement is sampled as morphologic filtered line

• Calculation of Ra and Rz

How does a Confocal Laser Scanning Microscopy work

• Two aperatures integrated in the obeservation beam path

• Light of the focused surface point reaches the detector

• Since the illumination and onservation are indentical. Data of point in focal planewithout interference

• By line wise scanning of sample surface, layer images are generated

How does Focus Variation work

• Depth of focus is used to extract height information about the surface points

• For each camera pixel surface points is calculated

How does a Fringe Projection work

• Measurement system consists of camera and projector unit

• Projector generates planar and periodical structured pattern of fringes on component

• according to observed texture of measurement object fringes are deformed locally which is detected by camera

• Surface information can be calculated

Surface roughness of different AM Processes

• PBF-LB/M: Ra > 12 μm

• BJT: Ra > 12μm

• MEX: Ra > 100μm

• DED: Machining necessary WAAM and LMD different roughnesses

How can the grain/micro structure between MEX and BJT differenciated

• BJT has powder in Cavities due to being printed with powder

• MEX not due to being printed with Wire

Pros and Cons Profilometer

Pros:

• Well established, standardized

• High reproducability and traceaility

Cons:

• Probe tip as mechanical low pass filter

• Surface can be altered by touch of probe

Pros and Cons of Optical Areal Surface Measurement

Pros:

• Optical surface analyzing techniques are contactless

Cons:

• Optical disturbances of environment

• Material specific structure can create scattering

• Overexposure induces illumination peaks

Micrograph Preperation Steps

1. Cutting

2. Embedding

3. Grinding

4. Polishing

5. Etching

Powder Layer Size PBF-LB/M

20-60μm