SpreadStation Powder Analyser
The SpreadStation Powder Analyser measures the spreadability of powders by actually spreading powders in a layer and then analysing the properties of the layer.
Powder is loaded into a spreading device that includes a feeder and a spreading plate. The spreading device rests on a build plate and has an adjustable gap at the bottom to control the powder layer thickness. The build plate is rotated to create linear motion between the spreading device and the build plate. This linear motion spreads the powder in a layer on the build plate.
Images of the created layer are captured and the thickness of the layer is measured using a laser distance sensor. The layer is then removed from the build plate by a scraping blade and is weighed.
The SpreadStation can be equipped with up to four spreaders and the build plate can be a solid plate or a powder bed. Spreading speed is programmable from 1 to 300 mm/s. Spreading layer thickness can be set from 20 micrometers to 2 millimeters. The build area can be heated to 250C.
Images of good spreading and poor spreading alloy using the SpreadStation Powder Analyser
The SpreadStation can be equipped with up to four powder spreading assemblies. Each spreading assembly is set up with a powder feeding system and a powder spreading plate. The feeders and spreading plates can be changed quickly to study different printer parameters and simulate different printer feeding and spreading systems. The spreadering assemblies are removed from the SpreadStation for cleaning between samples. This requires approximately 30 seconds.
The angle feeder allows the feeding angle of the sample powder to be adjusted as well as the gap at the bottom of the feeder.
The straight feeder allows the feeding width and the feeding gap from the sample powder to be adjusted.
The pressure feeder allows the pressure on the top of the sample powder to be adjusted as well as the feeding width and feeding gap.
The powder feeders deliver sample powder to the spreading zone of the spreading assembly. The feeder can be removed without tools for cleaning and quick changes. The gap that the powder must flow through to reach the spreading zone can be adjusted for all feeders. The height of the exit of the feeder can also be adjusted.
The flat spreading plate has a flat bottom and can be rigid or flexible. The standard plate is made of polished stainless steel but many optional materials are available
The round spreading plate has a round profile at the bottom.
The rotating roller plate uses a rotating roller to spread the test powder. The rotating direction and rotation speed is controlled by software.
The powder spreaders determine how the powder layer is formed when the powder is being spread. The spreading gap (leveling height) is set when installing the spreader on the spreading assembly.
Layers created by the SpreadStation are analysed using three independent measuring systems and produce three independent sets of data. The measuring systems are: 1) weighting system; 2) laser triangulation distance system; and imaging system.
The weighting system measures the mass of powder being spread by the SpreadStation over time. The weighting system uses load cells to measure the powder mass and 24 bit A to D converters to digitize the load cell readings.
Weighting System Data:
Spreading Efficiency: The spreading efficiency is the ratio of the spreading density to the material density. A spreading efficiency of 100% means the spread layer is equivalent to a solid layer of material while a spreading efficiency of 0% means there is no powder in the layer.
Spreading Density: The density of the layer of the powder, units grams/cm3
Spreading Rate: The mass of powder exiting the spreader over time, units grams/cm
Spreading Uniformity: The uniformity of the layer density from the start of the test to the end of the test, units %
Laser Triangulation System
The laser triangulation system measures the thickness of the powder layer created by the SpreadStation.
Laser Triangulation System Data:
Layer thickness: The thickness of the powder layer measured over time, units micrometers
Layer Thickness Uniformity: The unformity of the powder layer thickness, units %
The imaging system consists of digital cameras and LED lighting that collect images of the powder layers created by the SpreadStation. Image analysis software is then used to extract information about the layer quality.
Imaging System Data:
Area Coverage: The area coverage is the ratio of the area in the image covered by powder to the total area of the image, units %
Channel Detection: The image analysis software determines if there are any channels is the powder layer and if so the width of the channel, units % channels, width millimeters
Wave Detection: The image analysis software determines if there are any waves in the powder layer and their widths, units % waves, width millimeters
The spreadability of a stainless steel sample was tested using a flat rigid spreading plate at increasing recoater speed with a leveling height of 150 micrometers.
|50 mm/s||49.3%||3.95 g/cm3||206 mg/cm||158 um|
|100 mm/s||38.3%||3.06 g/cm3||157 mg/cm||117 um|
|150 mm/s||31.4%||2.51 g/cm3||129 mg/cm||100 um|
|200 mm/s||22.8%||1.83 g/cm3||94 mg/cm||72 um|