Final Project Report (1)

Shane Derrick | McKenzie Horner | Colin Le | Quinn Walters ENSC 29

Final Project ReportENSC 29 – Child AFO


Project Overview

Improve the manufacturing process of child AFOs AFO: Ankle Foot Orthosis Current process involves fabrication of mold, vacuum heat

forming of solid polypropylene sheet 3D printing cuts time and cost


Purpose

Reduce time and cost of producing AFOs Materials research to help determine

optimal printing materials


Materials Testing

Materials to test PLA Polypropylene Carbon Fiber PLA PETG Nylon

MTS and Fatigue


Deliverables

Full scale AFO print (PLA and PETG) Materials research results Material recommendation Printing process overview


3D Scanner

Leg is first casted out of plaster Cast is 3D scanned Spectra Scanner

Resolution: 100 microns (100 μm)

CanFit software can modify model

Exports a 2D surface (.stl file type)


Meshmixer

Converts 2D surface in 3D space to 3D model

Extrudes surface normal to the surface

Designate the extrusion thickness

Objective: 3mm Export as an .stl


Simplify3D

3D AFO placed onto virtual print bed Print settings based on material

Nozzle and bed temperatures Raft and support material 100% Infill for solid walls Material Presets for ease of use


3D Printing

.gcode sent to printer Printer head and print bed heat up

to desired temperatures Monitor first layer and adjust z axis

offset for good bed adhesion Return ~16 hours for completed print


Testing Methods

MTS Machine Measures: Tensile Strength and

Young’s Modulus

Fatigue Tester Measures: Withstands cycles of

bending forces before failure


Polylactic Acid (PLA)

Pros: Printability costCons: Concerns about brittleness Biodegradability is a factor

Exposure to UV radiation, humidity over timeVerdict:Great for rapid prototyping and awesome repeatability, long-term viability may be a concern


Carbon Fiber PLA Overall results were inconclusive

Only one attempt was made Adjusting printer settings could yield a workable product

Pros: High strength Aesthetics Cons: Poor fatigue results Extreme brittleness

Possibility of shattering, causing patient harmVerdict:Complete print of AFO is feasible, but extreme brittleness makes it difficult to recommend


3DP Polypropylene

Pros: Properties closest to original material Very easy to load into printerCons: Does not stick to bed

Glass transition temperature is less than room temperature No printers currently use cooled beds Major warping, layers do not stick together Verdict:Until 3D printing technology advances, polypropylene not feasible for nonindustrial applications


Polyethylene Terephthalate Glycol (PETG)Pros: Highest average ranking Very printable, great repeatability Good compromise between strength and flexibility Relatively inexpensive Cons: High-tendency to split after long-term use "Eyeball flex test"Verdict:A great compromise between properties, great for rapid prototyping, long-term viability may not be possible


Nylon

Printed with PCTPE nylon 680 would have been preferred

Pros: Fairly repeatable printsCons: Extremely low modulus

Not enough support Requires baking before or after printing Absorbs moisture during long prints Most expensive (even more for 680) Verdict:While 680 nylon preferable, inferior properties may make it infeasible for AFOs; price and preparation time are also negatives


Testing Results


Materials Summary

Objectively PETG seems to be the best material

Average ranking do not take into account subjective categories Comfort Amount of support Aesthetics

Did find out a lot about what could work and what most likely will not

Interesting comparison of materials, importance of compromise


Recommendation

PLA: Very good for rapid prototyping, we would recommend it as a

material to test fits quickly before sending out for a finalized product

PETG: Much better than PLA, we would recommend for temporary use, or

possibly a final product with further testingNylon:

We didn't have time to comprehensively test every variation of nylon, there is a possibility one of them would work


Implementation Issues Materials:

We knew going into this project that we may not find a way of printing this product with a material that met our requirements

Testing:We also knew going in that we would not have a clear way of testing our full scale printed AFO, and we had limited resources and time (no 3-point-bend test or patient testing)

Software:We did not have any idea how much time would be spent looking for software to do the simple task of extruding our scan into a printable product

Printer issues:Due to prints run by the university, the printer was unusable for several days


Cost Analysis

Time Savings Current Process: 3D Scan sent to Portland-> Foam Positive Mold -> Rough

Cut AFO -> Ship back to Shriners Hospital -> Final Adjustments

Total Time: ~2 weeks 3D-Printed Process: 3D Scan -> Extruded in Meshmixer -> Print process

set-up in Simplify3D -> 3D print

Total Time: ~16 hours Additional Notes

Multiple prints can be made simultaneously for different fits


Cost Analysis cont.

Cost Savings Limited Information from Shriners regarding overall cost

(manufacturing, staffing, etc.) 3D printing only uses the required material. (~0.5 kg per AFO) 3D printing is not labor intensive. 3D printed materials are relatively cheap and will continue to

decrease in price with the growing interest in the technology. Cheap PLA 3D printed prototypes can be made to test fit with the patient

before using a more expensive material for the final product.


Project Conclusion

Is it possible to 3D print an AFO to scale? Yes

Will it save the hospital time and money over time? Yes

Will PLA/PETG meet patient needs? Insufficient data


Future Projects

Advancement of 3D-printing technology Blended materials Polypropylene-compatible printers

Innovative geometries Modifications to existing AFOs Varying thicknesses Combinations of materials

Optimized material testing 3-point bend test

Volunteer test subjects?

Final Project Report (1)

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