Since the quality of our additively manufactured parts and components is very important to us, we have a very extensive catalog of measures for checking a wide range of parameters. Here is an overview of our in-house measuring and testing techniques. For more detailed information please click the link or scroll down.
In industrial computed tomography, sectional images are calculated from the absorption values of the X-rays that pass through the object during scanning. Highly accurate representations of outer and inner contours are generated which are used for analyzing the interior of the component. The object is fixed in a suitable position on the manipulator. Next, the tube or detector parameters are set depending on material, wall thickness, or geometry. In special cases, in is not necessary to scan the complete component, but only an enlarged section, the so-called ROI (Region of Interest). The scanning process is non-contact and non-destructive. Independent of the post-processing technique, any object and any material can be scanned and, depending on the size of the component and the wall thickness, a 2D projection is generated in a short time, which is converted into a 3D volume by a high-performance computer.
An optical 3D scan is used to make an exact, non-contact analysis of shape and dimension of a component without contact. In preparation, the component surface is sprayed with a special spray and adhesive dots are applied to the object to ensure that sufficient measuring points are available even for reflective surfaces and undercut objects. Precise fringe patterns are then projected onto the object surface and captured by two cameras using the stereo camera principle. Since the beam paths of both cameras and the projector are defined through calibration, up to 2x16 million coordinate points can be precisely calculated from the three different beam intersections. The result is complete measurement data set without holes or errors. The projection unit of the Triple Scan is based on Blue Light Technology. The sensor works with narrow-band blue light so that interfering ambient light can be filtered out when the photo is taken. Due to the strong light source short measuring times can be achieved.
In tactile 3D measurement, the component surface is measured point by point using precise probes. This is used to determine various geometry elements such as hole distances, bore diameter, depth dimensions, or angles of a workpiece. The measuring probes are equipped with ruby tips and are automatically exchanged by the measuring arm of the system, depending on the measuring task or customer specification. This significantly speeds up the whole measuring process. Using the main x/y/z axes, measured values can be determined independently of shape and geometry, which again helps to save time. Tolerance violations can be detected in the shortest possible time.
For tensile and compression tests with a static universal testing machine (type: Inspect Table from H&P) different test methods are possible. A specific test piece conforming to the standard is manufactured according to each test technique. In the 3-point bending test, the test piece is positioned on two fixed brackets and force is exerted from a third point from above until the material breaks. In the compression test, the brackets are removed and the test piece lies flat on a plate. A second flat plate exerts more and more pressure from above on the sample part until, again, it breaks. In the static and dynamic tensile test, the tensile bar is clamped at both ends between two specially shaped brackets, and force is applied in two opposite directions. The dynamic tensile test does not use ultimate force but stops at a restricted value. This procedure is repeated several times. This causes material fatigue by fine cracks. The values describe the longevity of a material under repeated application of force until ultimate failure. In the static tensile test, the procedure is carried out only once, and force is increased until the material breaks. A graph simultaneously records the curve of tensions and force until the part breaks in order to determine the characteristic values.
A Hall flowmeter is used to analyze the flow rate of a particular material. Exactly 50 g of a material is weighed and poured into a cylinder located in a fixture. The time it takes for the material to flow through a standardized opening into a vessel below is then stopped. The flow rate of the powder is influenced by the size, distribution, and surface topography of the grains.
In the hardness test, static force is used to make an indenter penetrate a test piece, which is susually made of soft metals. The resistance is measured by the penetration depth or indentation size of a cylindrical indenter (Rockwell hardness) or a ball indenter (Brinell hardness). Most commonly, this indentation measurement technique is used at the end of a process chain to check the final hardness.
This non-destructive technique can be used to determine the elemental composition of various raw materials. When X-rays enter a test piece, characteristic rays are reflected, collected, and assigned to elements depending on the type of radiation. Like this, it is possible to determine the composition of all used materials. Since additive manufacturing processes mostly use alloys, this analysis plays an important role in reliable quality control.
When inspecting through a light microscope, the test piece is examined under an LED cold light source, making visible pores, cracks, or other defects of the inspected surface. The test piece is embedded into fast curing resin and the surface is polished smooth with a grinding and polishing machine.
In roughness measurement a perthometer is used, i.e. a pointed needle is placed on the surface of the test piece and a standardized route is traced on its surface. Average values for the measurement result are calculated from the transmitted surface roughness profile.
With a 2D height gauge, precise measurements of the component's outer contours (max. height 600 mm) can be determined and checked very quickly; a high repeatability is given. A test arm with a ball tip is located on a static, height-adjustable measuring tower. The component is positioned in such a way that the ball tip with the integrated dynamic probe system hits the desired surface and determines the data for this measuring point. This procedure is then repeated at the second measuring point and the value of the distance is determined.
During a surface measurement with a microscope, a fringe pattern from two light sources is projected onto the component (max. 200 × 100 × 10 mm). Elevations or indentations on the surface of the measured object cause the light stripes to be distorted. The shape of the object is determined on the basis of their reflection. In the resulting 3D model, line and surface roughness can be determined very precisely (height: ±3 μm; width: ±2 μm).
To determine the density of a body, the analytical balance uses the Archimedean principle. A density cube (max. 220 g) is weighed on a high-precision balance as well as in a liquid medium, and the difference between the two weighing results is calculated. This technique is recommended to determine the volume or density of the test piece in a fast and simple way.
In laser beam quality measurement, the cross-section of the laser beam (during laser melting) is measured at a specific point in order to determine the laser power and focusability. This shows that the laser beam intensity decreases towards the edge. In technical optics, this is referred to as “caustic“. These findings are important in the setup and optimization of machine and parameters.
The accurate and fast analysis of grain size or grain shape is essential to increase the quality of additively manufactured components. By means of an oscillating conveyor trough, the powder is transported into the measuring device. There, a dust cloud is created by an air jet in front of a two-camera system and images are taken and transmitted. The image analysis provides insights into the quality of the powder particles which can vary in size from 0.8 μm to several millimeters. At FIT, the technique is also employed in incoming goods inspection and machine monitoring.