This method can help to open the door for ceramic components to manifold applications such as ceramic reactors, surgery tools, or customized luxury products. The main advantage of this technique is that the position of some material happens selectively. And the certification of some material occurs independently of some material properties.
We first had the idea for this method when we thought about the adaption of our knowledge in the field of multi-material approaches to additive manufacturing. To make the thermoplastic suspension, first select the powders. Additive manufacture of black and white objects requires two powders.
In this case, the choices are zirconia black-1 and zirconia white-1. Which have comparable centering temperatures. Obtain field emissions scanning electron microscope images of both powders to characterize some with respect to particle shape and surface area.
Here the average particle diameter of the zirconia white particles is approximately 4/10 of a micrometer. As measured with a laser diffractometer, the zirconia black particles have an average diameter of 1/2 a micrometer. Move on to prepare the suspensions in a heatable dissolver.
Prepare each suspension separately with the dissolver at 100 degrees celsius by melting a mixture of paraffin and beeswax. Before continuing check the vessel to insure that melting is complete. Once melting is complete, homogenize the polymer mixture.
Next, reduce the speed of the resolver disc. Then, over several steps, slowly add one of the zirconia powders, so it becomes 40%of the mixture by volume. After melting the paraffin, beeswax, and other chemical components, homogenize the polymer mixture.
Next reduce the speed of the dissolver disc. Then, over several steps, slowly add one of the zirconia powders, so it becomes 40%of the mixture by volume. Stop when the powder content is 40%by volume.
The target value for both the black and white suspensions. Then, stir the powder polymer mixture for two hours at 100 degrees celsius. After stirring, ensure the mixture is homogenized before preceding.
As they created, characterize each molten suspension using a rheometer. Plot the dynamic viscosity as a function of the shear rate for different temperatures. These data are for zirconia black-1, and zirconia white-1 at two different temperatures.
For a given suspension and temperature, make sure the dynamic viscosity is below 100 pascal seconds for a shear rate of 10 per second. Below 20 pascal seconds for a shear rate of 100 per second. And below one pascal second for a shear rate of 5000 per second.
If necessary, alter the dynamic viscosity by increasing the temperature or adding polymer mixture. Begin working with a thermoplastic 3D printing device. This drawing depicts the devices three micro dispensing systems.
Which can work simultaneously or individually. Also depicted is the profile scanner used to help characterize the printhead output. This is the thermoplastic 3D printhead as it appears in the printing system.
Select two of the dispensers to use. For black and white additive manufacturing, add the black suspension to one dispenser, and the white suspension to the other. When ready, experiment by varying the deposition frequency, the axis speeds, and other parameters for single droplets and droplet chains.
Employ the profile scanner, which uses a blue laser to collect data to characterize the output. Identify dispensing parameters so the droplets of both materials have the same characteristics. Adjust the distance between single droplets to avoid differences in the heights for different materials.
Here are examples of single droplets and droplets chains, produced with different parameters and using both black and white suspensions. Review the output of a range of parameters for shape, volume and homogeneity. After determining the print parameters, decide on the desired part.
Use a generated 3D model of the part, and save the models file in an additive manufacturing format. In Slicer software, assign the two materials to the different component areas by allocating the corresponding micro dispensing system. Generate and upload the G codes to the printer.
Ensure the parameters are set and start the job. Printing this piece will take about an hour at eight millimeters per second. Recover the sample when the building process is complete.
At this point, the sample is ready for debinding. Take the sample to prepare it for debinding. Place the sample in a coarse screen to alumina powder bed for support and temperature distribution.
Next, put the powder bed with the sample into an air atmosphere furnace. And set the heating and cooling program to ensure a defect free bonding. Retrieve the sample when it is at room temperature.
And continue with the next steps. Remove the sample from the bedding powder. Then, carefully remove any bedding powder with a fine brush.
For a second debinding, place the sample on alumina kiln furniture. Return to the air atmosphere oven and use a more rapid heating rate and the same cooling rate for the sample. After cooling, take the sample to an air atmosphere centering furnace.
Center the sample at 1, 350 degrees celsius, for two hours. This is the manufactured piece at the end of the debinding and centering steps, along with its 3D model. Use a 3D scanner to characterize component shrinkage, which should be about 20%in each direction.
Perform further characterization on cut and polished printed samples. This field emissions scanning electron microscopy image is of the cross section at the planer interface between centered zirconia white-1 and zirconia black-1. Obtain more information with energy dispersive x-ray spectroscopic analysis of the two regions.
On searching for peaks associated with alumina, the results indicate that more alumina cross occurs in zirconia black-1. These measurement points are within the zirconia black region. Their composition is revealed with energy dispersive x-ray spectroscopy.
The spectra from this more detailed analysis, shows the zirconia black microstructure has alumina precipited. Once mastered, this technique can change the way of designing and using ceramic components. While using this technology you have to remember that it's only a shaping technology.
And the green bodies have to be debinded and centered to achieve the final ceramic properties. After watching this video, you should have a good understanding for how to combine, ceramic materials by additive manufacturing.
