Introduction: Prosthetic Cap 3D Printer


In the world of sports, athletes with disabilities are overlooked with their performance needs. Many require specialized equipment to ensure comfort and peak performance while playing the sports they love. The local Paralympic basketball team, The Austin River City Rec'cers, has many team members who suffer with physical hardships, such as spinal cord injuries, amputations, muscular diseases, and strokes. Due to the lack of equipment made to help such an athlete, our team decided to focus on a specific amputee on the team who lost his hand. The player covered his surviving limb with duct-tape for protection, yet this solution is non-reusable, wasteful, and less effective then other solutions used my fellow amputees in the athletic world.


Our team was drawn to this problem as we have personal connections to the Austin River City Rec'cers and were passionate about helping an organization we fully support. One of our team members has a parent who plays for the team and she herself has been extremely influential with her volunteer work for the non-profit, setting up their website and running many of their tournament games. The players have become her family and through her involvement she witnessed a great problem that she was determined to solve with the resources provided during Cornerstone. After presenting the idea to her other team member and getting input from our maker-mentors, we completed a 6-3-5 workshop with our peers for ideas on how to improve our product and different resources we could use that we hadn't thought of yet. We then went on to complete a Research and Design packet to rate our proposed project's effectiveness in the following categories: Automation, Electrical, Mechanical, Structural, And Passion. Looking back on these resources and reflecting on the connection we had to the organization, we decided to go forward with our original idea for the athletes.

Our Solution

We formulated the idea of building a 3D printer that would print caps for athletes out of TPU filament, which is more flexible and durable then the commonly used PLA filament. Our goal was to program and construct a product where the printer would automatically print a protective sleeve that could be customized with varying sizes to fit the athlete perfectly. We aimed to program a microprocessor (Printerbot) which would control various motor systems and be regulated by end-stop sensors as a safety precaution during printing. Due to our limited spending and the ability to use parts from existing printers, our project stayed below the budget of $200-$300 and met the demands of our client by providing an effective and convenient solution that could be easily distributed throughout the Paralympic world.


Fasteners / Screws

M8 Nut- 100

M8 Washer- 100 (order 2)

M3x20 bolt- 50 (order 2)

M3 Nut- 50

M3x10 Bolt- 6 (link is a pack of 50)

M3x8 grub (aka set) screw- 2

#10 x 1" Flat Head Phillips Sheet Metal Screws- 4 (pack of 100)


608 Roller Skate Bearings- 3 to 4

LM8UU Linear Bearings- 10 to 11 (order 2)

Threaded Rods

370mm 8mm- 6

300mm 8mm- 4

450mm 8mm- 3

210mm 8mm- 2

50mm 8mm-1

Buy 5 meters and cut accordingly

Smooth Rods

350mm 8mm- 2 (order 2)

405mm 8mm- 2 (order 2 and cut 1mm)

420mm 8mm- 2 (cut 80 mm off)


840mm GT2 toothed belt- 1

900mm GT2 toothed belt- 1

16-tooth pulleys to fit GT2 belts- 2

Here is a link to a belt kit on amazon (cut accordingly)

3D Printer Files

Frame vertex with foot- 4

Frame vertex without foot- 2

Coupling- 4 (print twice)

X carriage- 1

X end idler- 1

X end motor- 1

Z motor mount- 2

Belt clamp- 4

Belt clamp nut holder- 2

Bar clamp- 8

Rod clamp- 2

Y motor bracket- 1

Y bushing- 4

Endstop holder-3


1.5cm vinyl tubing, 6.35mm OD 4.32mm ID (3cm total)- 2

225x225x6mm plywood- 1 (for heating bed)

MK1/MK2 Heating Bed- 1 (200x200mm recommended)

NEMA17 stepper motors- 5

4 inch Zip-ties- 50

Microprocessor and Code

Our team will update this document as we develop the code for our microprocessor

*the supply list above was recommended by rep rap but will be completely verified for this iteration once we finish our printer*

Step 1: Building the Frame

The first step to building the 3D printer is assembling its frame which consists of two smooth rod triangles which are connected by additional rods running vertically. Our group was lucky enough to find an already constructed frame on our campus, which we then modified to be an exact replica of the Prusa Mendel Iteration 2 by changing out the clamps which held together the bar perpendicular to the y-axis and the smooth rods used for the x-axis. For those building the frame themselves, please access the Rep Rap Website* which has a specific section giving detailed instructions on how to construct the frame structure so that it is perfect and the necessary materials for the build (included in our total calculations). Above are some photos featuring certain printed pieces of the frame and the construction, as well as our frame before it was modified to fit Rep Raps's version.

*Our group felt like this resource gave better information on the frame's construction then we could as we hadn't constructed this aspect of the printer ourselves. We are deeply sorry we could not add our own personal perspective on this step, yet we feel like we would be limiting builders and hurting them with potential inaccurate information provided by us. This site can be deeply trusted and was a great reference throughout our building endeavors.

Step 2: Building the X-Axis


Printed X end Idler

Printed X end Motor

2 420mm smooth rods

3 M3x10 bolts

1 608 bearing

2 M8x30 fender/mudguard washers

1 50mm M8 threaded rod

2 M8 nuts

3 M8 washers

3 LM8UU Linear Bearings


- Drill out the center hole of the x-end-idler and x-end-motor parts to 8mm and drill out the 4 holes where the smooth rods will be inserted (file if needed to make sure they can fit snuggly into the hole)

- Place the x-end motor on the left and the x-end idler to the right with their "hexagonal sections" facing each other. Slide the smooth rods into the idler.

-Now look at the bottom of your x carriage and see which side has slots for two linear bearings and which one only has one slot. Keeping this is mind, determine which side will be the front and which will be the back, and slide the correct amount of linear bearings onto each rod (1 for one, 2 for the other) according to your preference.

-Attach the x-end motor to your rod set-up and make sure the rods go as far back as necessary (option to drill completely through so that adjustment and attachment are easier, just need additional nuts to secure)

The photos above show the two printed pieces for this assembly and our team's current progress on the x-axis. Although our group did not yet reach this point, the x-axis is not completely assembled until the 50 mm threaded rod is placed onto the x-end idler and the bearing is attached for the extruder belt. Use the rep rap source linked at the bottom for further information, and we plan to continue updating the building process once we have access to the resources.

Step 3: Building the Heating Bed


225x225x6mm plywood- 1 (for heating bed)

MK1/MK2 Heating Bed- 1 (200x200mm recommended)

#10 x 1" Flat Head Phillips Sheet Metal Screws- 4

Printed Y Bushings- 4


- Place the Y-bushings (facing upwards) on the piece of plywood and make sure the two sets on each side measure 140mm from one another (measure from the exact middle) and that their distances from the left and right sides are equal

-All the bushings and their rod channels will be running/facing the same way so that the plate can run smoothly along the y-axis rods

-Clamp down plywood and carefully use screws* to attach the y-bushings, placing them as close to the front and back sides as possible without the wood cracking as then they won't interfere with the heating bed.

-If screws protrude upwards from plywood, you can use a handsaw with a rotating blade to cut the excess metal as it can be dangerous and limit the printer's functions

- Repeated Important Information for the bushings: they all must be facing the same way, and their distance from the front and back sides of the plywood don't matter just the left and right ones and the distance between the bushings (also running left to right)

-Measure your heating bed into thirds on two opposite edges of the bed (either left and right or front and back)and drill two 8mm holes at the lines (if using recommended 200x200mm, would drill about 7 cm from each side and as close to the edge as possible)- as shown in one of the photos above

-Subtract the difference of lengths of the heating bed to the plywood, divided it by two, and measure from each side of the plywood with that number so that your heating bed is perfectly in the middle of the wood. (marking using that methods can also be seen in one of the photos above

-Clamp the bed and wood together while also securing it to a sold surface, and screw using the 4 Flathead Phillips Sheet Metal Screws

*Our team does not know the specific size and type of screw which was used to secure the y-bushings to the plywood, yet as soon as we are back in the maker space and have access to the printer, we will figure out the type of screw and update the page. Thank you so much for your understanding

Step 4: Building the Y-Axis


Assembled heating bed (from last step)

Assembled frame

Printed Belt Clamps-2

840mm×5mm T5 pitch timing belt

NEMA17 stepper motors-1

16-tooth pulleys to fit GT2 belts- 1

4 inch Zip-ties- 4


-Gather your assembled heating bed, a belt clamp, and 2 screws that would fit into the belt clamps holes*. Flip the heating bed over and using a ruler, measure and place the belt clamp in the middle on the front side/edge of the plywood (place it as close to the edge as possible). Now slide one edge of the 840mm belt into the belt slot with the teeth facing up. Secure the belt with screws.

- After making sure the two smooth rods are 140mm apart from one another (as shown in the image above), flip the heating bed to its right side and snap the y-bushings of the heated bed onto the rods.

-If there is any problem with attachment because of differing distances in the rods, you can adjust their placement by loosening the nuts and shifting the bar clamps on the threaded rods to which the y-axis rods are attached to.

- Once the heating bed can slide smoothly along the rods, flip the printer to its side. Then on each bushing, run a zip-tie through the small passageway on each printed bushing and around the rod its attached to, then pull until tight

- Now that your bed is secured, we can flip the printer to its normal position and temporarily secure the y-axis stepper motor (this is the farthest our team got in this specific step). Slide the stepper motor into the y motor bracket and attach the 16 tooth belt pulley-tighten as needed.

- Now once you have made sure your belt bearings for the y-axis are perfectly lined up, wrap the belt attached to the heating bed around both the first bearing and the pulley attached to the motor. Then pull it tightly under the heating bed and wrap it around the second bearing, making sure that on both bearings the belt's toothed side is touching the bearing and that the teeth fit perfectly into the motor's pulley.

- For convenience, slide the bed all the way to the motor end of the belt system. Now same as you did before, measure and place the belt clamp in the middle on the back side of the plywood with it as close to the edge as possible. Pull on the belt's edge tightly and secure it in place (cut off any excess if needed). Now the bed should slide with little force yet also well fastened.

*Our team does not know the specific size and type of screw which was used to secure the belt clamps to the plywood, yet as soon as we are back in the maker space and have access to the printer, we will figure out the type of screw and update the page. Thank you so much for your understanding

Step 5: Going Forward...

Our building process was cut short due to the recent pandemic, yet as soon as we have access to our project and materials, we plan on completing the printer and giving it to the Austin River City Rec'cers. That being said, we still have lots to complete before achieving our goal, so below is a list of what is still needed to be done.

-Attach vertical frame pieces to the motor holders and to each end of the rod running perpendicular to the y-axis (use bar clamps)

-Finish Assembling the X-axis: we plan on securing the bearing for the extruder belt, then we must attach the stepper motor and the extruder provided to us by one of our maker mentors (optional: include extruder fan for filament)

-Figure out way to secure filament in safe way (options: design and print wheel that could either tension fit into or stick out from frame)

-Complete Z-axis: we need to attach the 210mm threaded rods to the two z-axis motors with the couplings and vinyl tubing

- Attach end stop holders/ end stops to every axis (1 each)

- Secure printerbot microprocessor with zip ties to one face of the frame

-Programming: connect all end stops, stepper motors, and the heater bed to printerbot microprocessor. Find existing code for prusa iteration 2 (use rep rap as source) and modify if necessary

We are sorry for the inconvenience of our unfinished project, yet we hope to continue working on it over the summer months and promise to update this site as we improve/ complete our printer.

Step 6: Sources

Our team followed the building process and materials list provided by the Rep Rap Website. They feature detailed instructions on every aspect of this iteration of the Prusa Printer and their site is extremely easy to follow. That being said, below are the links to the main page of the site but also the key pages for information on assembly, supplies, etc.

3D Printer Files (we used the files under the metric-prusa tab)

Rep Rap "Bill of Materials"

Rep Rap Printer Assembly

Our team would also like to include a link to the Austin River City Rec'cers website (the organization we aimed at helping with our product) to learn more about the team's purpose and players. You can also donate here to help the team with their yearly expenses as any contribution is both greatly needed and appreciated.