Modifying a Noztek Hopper for Vertical Extruding
Background:
I created this website to capture all of the aspects of my life in one place and to share my adventures with family, friends, and anyone else interested in what I’m doing. To this point I’ve been writing about my personal experience of moving to Charlottesville with my wife, Laura, and the adventures we’ve had thus far. Now, I’m excited to share my first technical post covering some of the work I’ve been doing at UVA as a graduate research assistant.
Why:
When I arrived at UVA I was assigned to a Department of Energy project to create cheaper and stronger carbon fibers. The project was already halfway through the 1st quarter of its 2nd year, so I have been doing my best to get up to speed and contribute. A component of this research involves spinning precursor fibers that will be turned into carbon fibers, and the team had purchased a Noztek Xcalibur filament extruder to perform this task. After I arrived we mounted the extruder vertically to mimic the industrial melt spinning process that we’re trying to approximate. Noztek sent us a new hopper we could use to feed the pellets into the barrel in the new vertical orientation, but the design wouldn’t feed the extruder screw properly without a large quantity of raw pellets. Our test batches are pretty small, the fibers we’re extruding are on the order of 50 micro-meters in diameter, so we needed a better solution.
A better hopper would:
Require less pellets to feed the extruder screw consistently
Feed all of the sample pellets into the extruder automatically
Allow for removal of remaining pellets without removing the hopper from the extruder, so that we can try different test batches more quickly
What:
With a university research project budget in mind, I set about designing a modification to the Noztek hopper that we received. To improve the hopper’s ability to feed the extruder screw, I designed a ramp that closes out the bottom corner of the hopper away from the barrel inlet. I attached two vibrating motors to the bottom side of the ramp to agitate the pellets and encourage them towards the extruder barrel. I chopped the top off of the stock hopper for easier top feeding. I removed the front face of the hopper and reattached it with a hinge, so the ramp and vibrators could be accessed as well as allowing for easier removal of pellets that aren’t consumed in a test run. To keep the new front door closed I fixed a pair of magnets to L-brackets that I attached to the hopper body with 3M VHB tape; No fasteners needed!
Sure, it’s an expensive way to cut out a simple flat pattern, but it’s way easier than doing it by hand.
How:
I planned the modifications by modeling the OEM hopper in Solidworks and then making a second version with the desired edits, so I could easily assess fitment and produce engineering prints to guide my fabrication work. The CAD model for the as-delivered hopper and the modified hopper can be found on my GrabCAD profile, here and here respectively. Caveat Downloader: take the dimensions with a grain of salt and consider that the actual part is made out of sheetmetal and may have a wide dimensional variance.
I modified the hopper at UVA’s Lacy Hall Student Experiential Center, which houses UVA’s student design competition teams (SAE Baja, UAV, battle bots, and robot mining, to name a few) and also has a waterjet, CNC mill and lathe, and everything else you’d need to build something. I waterjet cut the ramp flat pattern and then bent it on a box break. I chopped the top, cut down the hinge I bought from McMaster-Carr, and added a pair of holes underneath the ramp so the battery pack and switch for the motors could be mounted to the outside of the hopper. I attached the hinge with VHB tape rather than adding more holes for time’s sake, and added grommets to the access holes to protect the wires that pass through. With research and homework deadlines looming I didn’t worry too much about being perfect or keeping the paint nice, but I am happy with the result.
*Note: Not shown is the 3x AAA battery holder w/ on/off switch that powers the motors and is attached to the side of the hopper with a strip of hook and loop tape
Results:
The modifications have worked! We are able to keep more pellets at the barrel opening to the screw without waste and without manually pushing the pellets towards the barrel. The vibrating motors make a visible difference, as shown below, and the hinged door made it really easy for me to remove the pellets left over from an incomplete test run when I wanted to switch out the input material. The design is far from being the perfect hopper but it is a much needed improvement to our process. This was a simple design project, but it was a great way to wade into the pool of resources available here at UVA. My next project is designing a test stand for the extruder and a module to mount our fiber winding motor and control. My bill of materials for this project is included below for anyone else who wants to make this modification.
Bill of Materials
Noztek “vertical” hopper as included on Noztek Pro and Noztek Pro HT models (as of this writing)
5052 Aluminum Sheet - 0.050” Thick - At least 6” square
1x Steel Piano Hinge - McMaster Carr P/N: 1608A42
2x Neodymium Magnet - 0.06” x 0.50” w/ adhesive on South pole - McMaster Carr P/N: 7048T16
2x Rubber Push-in Grommet - for 0.50” ID and 0.063” material thickness - McMaster Carr P/N: 9600K32
2x Vibrating Mini Motor Disc - Adafruit P/N: 1201
1x Three AAA Battery Holder w/ On/Off Switch and 2-Pin JST - Adafruit P/N: 727
1x JST PH 2-Pin Cable - Male Header 200mm - Adafruit P/N: 3814
3M VHB Tape 4929
Acknowledgements:
This project was supported by the U.S. Department of Energy (DOE), Vehicle Technologies Office under the contract number of DE-EE0008195.