Embedded Files
Original Shin Cuffs
Original Shin Cuffs
My first project at the NAU Bio-Mechatronics lab was in charge of updating the shin cuff design, due to its lack of torsional rigidity, and the whole carbon fiber manufacturing process in general. The picture to the left is the original carbon fiber shin cuff and its apparent that appearance was not a main focus in the early development of the ankle exoskeleton. once the design was somewhat settled, it then time to make it look better.
Carbon Fiber Goals
Carbon Fiber Goals
Improve rigidity of cuffs in torsion
Improve surface finish of parts
Streamline the manufacturing process
Improve mold cycle life
make overall process cheaper
Original Process
Original Process
Original Molds
Original Molds
When i started this project, we were using raw 3d printed molds. These molds worked, but they were extremely hard to separate from the part and the surface finish was not great.
Original Mold Treatment Supplies
Original Mold Treatment Supplies
The cuffs where hard to remove because we were using hair spray and car wax as a separation layer on a rough 3d printed surface. This led to chiseling out the part which ended up breaking the them after a few cycles.
Experimental Cuffs
Experimental Cuffs
This series of experimental cuffs were meant to improve the rigidity while reducing cost and weight. I looked at a few different solutions like foam core and lipped cuffs.
Foam Core Shin Cuff
Foam Core Shin Cuff
Meant to save weight, increase strength and save money on the design
Ultimately was unsuccessful
not a repeatable/consistent product
Did not add much strength
high temp foam is expensive
Lipped Shin Cuff
Lipped Shin Cuff
Meant to significantly increase strength and reduce weight
Successful Outcomes:
Significant increase in strength
Small reduction in weight
Repeatable manufacturing process
Problems:
Poor surface finish
Reason of Failure
Reason of Failure
The previous molds were missing the lip feature to support the feature during curing in autoclave
Mold treatment was good for a hobbyist but not for production
Outcome
Outcome
Lipped Calf Cuff
Lipped Calf Cuff
After learning from my mistakes on the earlier prototypes I came up with a Lipped cuff design that was 2x-3x more ridged in torsion then the original design, weighed slightly smaller then the original design, and the surface finish was sigifigantly improved.
Cuff Mold Improvements
Cuff Mold Improvements
The molds that are now used last much more cycles then the previous one and produce sigifigantly better finishes. overall it was a great success.
Current Cuff Molds
Current Cuff Molds
New molds are much easier to remove due to slick surface allowing them to last longer
Mold Chemicals
Mold Chemicals
New mold preparation chemicals sigifigantly increased the quality of finish.
New Process
New Process
With this new process of making carbon fiber parts, the lab saved a lot of money while also being able to achieve professional finishes on their parts.
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