Mott Corporation

I did a co-op at Mott Corporation for the spring semester of 2021. Mott Corporation is a company that makes all sorts of products with porous metals and sometimes ceramics. They make metal filters, spargers, gas diffusers, and many other products using techniques such as 3d printing, die pressing, and sintering.

At Mott I ran testing equipment, improved lab procedures, ran studies, helped problem shoot metal 3D printed parts, and did light data analysis.

Technical skills developed:

Bubble point test

The bubble point test is a test that lets you know the size of the largest pore in a porous material. This is useful in the QC of filters but is also useful to quickly check the approximate pore size in a part for R&D. The test takes about a minute per part rather than the 30 minutes per part of a capillary flow porometer making up for its lack of information on the spread of pore sizes. I used the bubble point test to help calibrate the metal 3d printer in creating porous materials with the correct pore sizes.

Cappilary flow porometer

A capillary flow porometer is a very powerful tool for characterizing porous metals, it tells you the distribution of pore sizes in the media. First it finds the flow of compressed gas through the medium at various pressures creating a "dry curve". Then you thoroughly wet the part and it once again finds the flow at various pressures creating a "wet curve".

This diagrams shows what the machine measures

Tensile tester

I used the Tensile tester to measure the shear strength of an adhesive Mott considered using comparing it to welds.

Hirox digital microscope KH-8700

I used a Hirox digital microscope to perform several tasks for Mott:

  • general microscopy

  • 3d imaging

  • measurements of exposed area

  • measuring relative porosity

I took the image of the screw you see on the left to learn the ins and outs of the machine before I started work on a project the next day. It was taken with 136 slices on the scope's lowest power lens.

Stereoscopes

I used a Nikon Epiphot bright field and an Olympus general-purpose stereoscope for various tasks. The Hirox is better for images but I like using real optics for everything else. I found that the bright field capabilities of a real Epiphot were far greater than the Hirox even if it has less digital capabilities in the camera software. The ability to stereoscopically inspect samples that I am polishing also has immense value to me to check if I have polished enough on one grit.

Permeability stand

I set up and ran this permeability stand, it measures the ease at which fluids pass through a filter, in this case it was compressed nitrogen. This stand was comprised of: a compressed nitrogen tank, a pressure regulator, a flow meter, a temperature sensor, an inlet pressure sensor, the filter, an outlet pressure sensor and finally a valve. By varying the valve and pressure regulator you can target a specific flow rate and inlet pressure recording the outlet pressure creating a graph like you see below.

Flow stand

This is the flow stand I used to characterize filters. Flow stands are very similar to permeability stands but you set the pressure and measure the flow instead of setting the flow and measuring the pressure.

High-performance liquid chromatography (HPLC)

An HPLC is a tool that allows chemists to separate mixtures into their composite parts and then, depending on the sensor used, identify those parts. Mott makes several parts for HPLC's so they have one to test new components on. I used the HPLC to precisely measure the interior volume of components by running a program which varies the concentrations of a liquid running through the machine. This varying of concentrations creates peaks in the data measured by the UV VIS detector. Running the program through a known volume and an unknown volume creates peaks that are offset by a time, the difference in time multiplied by the flow rate is the difference in volume.

Cut/mount/polish

I cut/mounted/polished many samples at Mott both metal and ceramic. Mott's samples can be extremely difficult to grind, mount, and polish as they can be intentionally porous, very brittle, and very hard. The bottom photo is a "green" part (not yet sintered so very brittle), that is made of ceramic Al₂O₃ (comparably hard to most samples), and is porous, because of these factors It was very difficult to mount and polish.

Solidworks

I designed many parts in Solidworks based on technical drawings for the metal powder bed 3D printer and other purposes, I do not believe I can show any of the objects that I modeled for production.

I can show this little grabber for retrieving samples from the furnace (after they cool).

I also modeled this fixture so someone working off site could design some testing equipment.

Before buying expensive hardware and materials for a molybdenum furnace part holder I modeled everything in CAD to ensure it would all fit together.

Metal 3D printer

I did not operate the metal PBF (powder bed fusion) 3D printer but did work on many projects it was involved with and learned a lot about how all of the variables affect the final outcome of prints. I helped problem-solve issues with uniform density, porosity, and heat expansion. I also helped turn around the printer and finish parts; removing them from the bed, pulling off their supports, cleaning them in the sonic cleaner, and sending them to the furnace.

Light data analysis

In addition to the data analysis I did for other projects (especially for the HPLC work) I did some light data analysis for other peoples projects as well. I made these two graphs on the left comparing our filters to a competitors filters from data collected by a customer to help them visualize how our filter was helping their plant perform better and convince them to replace their existing filters with ours.


The graphs show the amount of ash measured on the back side of a filter, as you can see the A&B setup which has one of Mott's filters in it let less ash through than the C&D setup.

Improvements:

Equipment scheduling

I noticed that the two most used pieces of equipment, the bubble point and flow stand, usually had an informal line for them and it was very difficult to organize your day so that you could use them when they weren't being used. To fix this I created the spreadsheet you see above so people can write down their intentions to use the stand. This allows me to reference the schedule when planning my day so that the time I plan on using the stand does not conflict with someone else's.

Epoxy Project

Mott was not happy with two aspects of their epoxy: it was too viscous to get into the smallest pores of their samples, and it cures too slowly. They had me test out several other brands of epoxy after which I suggested instead of using a different brand of epoxy simply heat up the epoxy currently being used to decrease its viscosity during the pouring process and speed up the hardening. I designed and set up two experiments to test this.

Heating the epoxy to make it cure quicker

In this experiment, I increased the temperature of the environment the epoxy was hardening to see how much faster it would harden.

After 2 hours the 12-hour epoxy had hardened even if it did yellow slightly.

the mount on the top here was made with my current best procedure, it hardened in 2.5 hours and showed very little yellowing in comparison to the normal mount below. This allowed me to have a less than 1 day turnaround on a cut/mount/polish which allowed us to start a new metal powder bed 3D printer build addressing the issues we observed the same day.

Heating the epoxy to decrease viscosity for pouring

I heated up a beaker of water and dropped a container of epoxy resin in it, then I mixed the epoxy regularly and poured it. The epoxy was definitely more fluid and mixed faster than the room temperature control. This effort was successful, however, it is probably only worth it on particularly difficult parts.

Data consolidation

All of the 3D printed filter data used to have a separate spreadsheet for every build for all of the data, this made it very difficult to find the builds with the properties or draw any conclusions about what changing a certain variable does. I made a spreadsheet which organized each build together with all of the important variables. This made it very easy to pick out a build which has the results you want and replicate it instead of having to open up 20 spreadsheets and remember what values each build had.

Fiber study

Mott was not satisfied with the current method of welding together fibrous metal sheets to make tubes. They tasked me with running a study on using a special adhesive to bond fibrous metal. This adhesive would greatly reduce costs by eliminating castoff parts from bad welds on a difficult to weld material. I first ran an initial test using the tensile tester to experiment with different curing environments for the adhesive and found that the adhesive could be 60-95% as strong as the welds depending on how much was used. This was pretty encouraging so I constructed a full scale tube to test it under real world conditions (shown below next to its welded counterpart). With my suggestions Mott decided to pursue a less viscus adhesive that could penetrate into the fiber further.