The Raptor Reloaded Hand is a functional, 3D printed, prosthetic hand that amputees can use for assistance. This project, along with numerous other types of prosthetic hands, can be found on the e-Nable website. They have an amazing network of volunteers who work together to 3D print prosthetic hands for amputees. The CAD files for the 3D printed pieces are provided by e-Nable on Thingverse.com, and the Raptor Reloaded Design was created by Andreas Bastian, Ivan Owen, Peter Binkley, Frankie Flood, Skip Meetze, and John Simon. As a student at Irvington High School, I heard about this website through my engineering teacher, Ms. Berbawy, and quickly became interested in being certified for making prosthetic hands for those in need. Most of my time was spent planning out the process and dealing with the many print and assembly mishaps, but it was well worth the time. Everyone who has seen the finished product has been amused at how each piece moves and are amazed by the functionality as the fingers wrap around and pick up small objects.

I do wish that I scaled up the size to make a larger hand because the non-scaled version is actually smaller than I thought. Nonetheless, it was a worth while experience learning how to edit CAD files, slice them for 3D printing, operate the printer, and assemble a functional prosthetic hand.

Step 1: 3D Printing Raptor Reloaded Part Files

A 3D printer and slicer are necessary to fabricate the prints. Make sure that you are able to handle all aspects of a 3D printer. These include how to handle malfunctions, filament changing, and removing the parts from the build plate. Obtain the appropriate filament for your 3D prints in the color(s) you desire for your hand. I used the Ultimaker2+ as the 3D printer, Ultimaker Cura 2.3.1 as the slicer, and true black Polylite PLA as the filament.

Download the CAD files from thingverse. The files were uploaded by e-Nable on Dec 17, 2014. Remember to extract and unzip all the files. Place the following Raptor Reloaded files on a USB: finger tip, finger pin, thumb pin, proximal, right or left palm, gauntlet, tensioner pin, wrist pin cap, wrist pin, retention clip, tensioner, and knuckle pin. There are different types of palm and gauntlet files: with or without supports. I used the versions without the supports, since it allows the Ultimaker2+ to better accommodate for the overhang. The STL files can be linearly scaled, whereas the other types of files that are available on thingverse can be edited in Fusion 360 for more specific edits.

Open the files on the slicer; I used Cura 2.3.1. I had to print the pieces in groups since I was not able to fit all of the pieces onto a single print. The recommended printer settings are the following: PLA (or ABS, PET, nylon), 0.2 mm layers, 2 shells, 35% infill, and add supports when appropriate. The more detailed settings are in the pictures above; some of the settings are not available in other slicers. After the settings are completed, prepare and set the files on the SD card for the 3D printer. To do this for Ultimaker2+, click "prepare files" on Cura and then click "Save to removable drive." Choose the correct SD card to save to. Eject the SD card and the USB.

Insert the SD card back into the 3D printer and take the necessary procedures to safely print the pieces. For the Ultimaker2+, insert the SD card, wipe the surface with a disinfectant to remove all particles, ensure enough filament is available, click "print," select the desired file, and print.

When the 3D printer finishes printing, remove the pieces from the printer. With a cutting mat, X-Acto knife, and sand paper, remove the supports and smooth out the pieces.

Repeat these steps until all the necessary pieces are properly printed. The required 3D pieces of the Raptor Reloaded Hand are the following: 5 finger tips, 5 finger pins, 5 proximal, 2 knuckle pins, 1 thumb pin, 1 left or right palm, 2 wrist pins, 2 wrist pin caps, 1 gauntlet, 5 tensioner pins, 1 tensioner, and 1 retention clip. Other materials necessary can be purchased from the e-Nable assembly kit website or from a hardware store.

Step 2: Assembling the Fingers

Necessary Items: 5 finger tips, 5 proximal, and 5 finger pins

Attach 1 finger tip to 1 proximal via 1 finger pin. If all the supports are properly removed and the pieces are sanded smoothly, the pin should be able to easily fit through the corresponding holes where the fingertip and proximal meet. Push the pin until it is completely inserted and flush with the surface of the finger tip. The pieces should be able to move and rotate easily. Repeat for all 5 finger tips, 5 proximal, and 5 finger pins.

Total Pieces Used: 5 finger tips, 5 proximal, and 5 finger pins

End result: 5 fingers

Step 3: Attaching the Fingers

Necessary Items: 1 palm, 1 thumb pin, and 2 knuckle pins

Attach one of the fingers to the palm via 1 thumb pin. The thumb pin should be inserted from the top of the hole, through the palm and proximal, and out the bottom of the hole. Attach the rest of the fingers (4) to the palm via knuckle pins by placing the proximal in the 4 corresponding joints where the proximal meets the palm, and inserting 1 of the knuckles pins through the hole on the right and the other knuckle pin through the hole on the left.

Total Pieces Used: 5 finger tips, 5 proximal, 5 finger pins, 1 palm, 1 thumb pin, and 2 knuckle pins

End Result: assembled hand

Step 4: Installing the Elastics

Necessary Items: 1.5 m flexible elastic chord, 1 pair of tweezers and 1 pair of scissors

I highly recommend using a pair of tweezers to navigate the tight spaces of the hand. The goal of the elastics is to counter the force of gravity on the finger and to gently hold the fingers open. When setting the tension, the fingers should be able to snap back after being pressed down. At the same time, it should not require significant force to close the fingers.

For the "thumb" finger, thread one end of the elastic chord under the bar on the back side of the "thumb" finger until 30-35 mm of the chord is on the other side of the bar. Tie a clinch knot with the elastic chord around the bar. Trim the leftover 30-35 mm part of the chord and tuck the leftover chord under the 2nd bar on the back of the finger. Thread the elastic chord under the 2nd bar on the back of the finger. Pull the chord all the way through. Thread the elastic chord through the tunnel on the back side of the proximal. Pull the chord all the way through. It helps to use a needle to push the chord through or to trim the end of the elastic chord to prevent the fringed end from being caught half way through the tunnel. Thread the elastic chord up and through the "thumb" cable guide. Pull the chord all the way through. Thread the elastic chord around the cable guide and tie a clinch knot to secure the elastic cord to the cable guard. Use this knot to carefully set the appropriate tension on the "thumb" finger. Use a pair of scissors to cut off the extra elastic chord, but leave 5-8 mm of chord on the knot. Tuck the 5-8 mm of chord in the cable guide.

For the other "regular" fingers, the instructions are very similar to the instructions for installing the elastics on the thumb finger, except for the cable guide and cable guard section. After threading the chord between the proximal and palm to the front of the hand, guide the chord along the cable guide on the back of the palm and thread the chord through the cable guard. Pull the chord all the way through and maintain tension. Tie 2 hitch knots to secure the elastic chord to the cable guard. Use this knot to carefully set the appropriate tension. Use a pair of scissors to cut off the extra elastic chord, but leave 5-8 mm of chord on the knot. Tuck the 5-8 mm of chord in the cable guide. Repeat for all 4 "regular" fingers.

Total Pieces Used: 5 finger tips, 5 proximal, 5 finger pins, 1 palm, 1 thumb pin, and 2 knuckle pins

Total Materials Used: 1.5 m flexible elastic chord

Total Tools Used: 1 pair of tweezers and 1 pair of scissors

End Result: assembled hand with elastics

Step 5: Attaching the Gauntlet

Necessary Items: 2 wrist pins, 2 wrist pin caps, and 1 gauntlet

Push the wrist pin through the wrist hole in the gauntlet. Make sure the back of the pin is aligned with the head recess on the inner face of the gauntlet. Push the pin all the way until the back of the pin is flush with the inner face of the gauntlet. Slightly push the tips of the pin back and slide the palm into position so the wrist axis is aligned with the pin and the hole in the gauntlet. Press the wrist pin all the way through the palm's and gauntlet's wrist holes. The tip of the pin should stick out on the outside of the wrist and be properly seated. Snap the wrist pin cap over the pin. Repeat for the other side to complete the wrist.

Total Pieces Used: 5 finger tips, 5 proximal, 5 finger pins, 1 palm, 1 thumb pin, 2 knuckle pins, 2 wrist pins, 2 wrist pin caps, and 1 gauntlet

Total Materials Used: 1.5 m flexible elastic chord

Total Tools Used: 1 pair of tweezers and 1 pair of scissors

End Result: assembled hand and forearm with elastics

Step 6: Installing the Flexors

Necessary Items: 2.4 m non-elastic nylon chord (0.9-1.0 mm), 1 pair of tweezers, and 1 pair of scissors

I highly recommend using a pair of tweezers to navigate the tight spaces of the hand. The goal of the flexors is to create the mechanism that allows the fingers the ability to close when the wrist bends to create tension, which curls the fingers.

For the "thumb" finger, thread one end of the nylon chord under the tie bar on the underside of the "thumb" finger until 25-30 mm of chord is on the other side of the bar. Tie a clinch knot to secure the nylon chord to the bar. Thread the nylon chord through the tunnel on the underside of the proximal. Then, thread the nylon chord up through the proximal knuckle to the backside side of the hand. The proximal knuckle is where the proximal meets the palm. Do not wrap or twist the nylon chord and elastic chords together. Thread the nylon chord parallel to the elastic chord along the back of the palm and through the cable guide and the cable guard. Do not tangle the nylon and elastic chords. Leave about 15-18 cm of nylon chord, starting from the rear of the cable guard to the end of the chord. Use a pair of scissors to cut off the rest of the nylon chord.

For the other "regular" fingers, the instructions are very similar to the instructions for installing the flexors on the thumb finger. Thread the nylon chord under the bar on the underside of the "regular" finger until 25-30mm of chord is on the other side of the bar. Tie a clinch knot to secure the nylon chord to the bar. Thread the nylon chord through the tunnel on the underside of the proximal. Thread the nylon chord up and through the proximal knuckle to the back side of the hand. Do not wrap or twist the nylon chord and elastic chords together. Thread the nylon chord parallel to the elastic chord along the back of the palm and through the cable guide and the cable guard. Do not tangle the nylon and elastic chords. Leave about 15-18 cm of nylon chord, starting from the rear of the cable guard to the end. Use a pair of scissors to cut off the rest of the nylon chord.

Total Pieces Used: 5 finger tips, 5 proximal, 5 finger pins, 1 palm, 1 thumb pin, 2 knuckle pins, 2 wrist pins, 2 wrist pin caps, and 1 gauntlet

Total Materials Used: 1.5 m flexible elastic chord and 2.4 m non-elastic nylon chord (0.9-1.0 mm)

Total Tools Used: 1 pair of tweezers and 1 pair of scissors

End Result: assembled hand and forearm with elastics and flexors

Step 7: Installing the Tensioner

Necessary Items: 1 tensioner, 5 tensioner pins, 5 tensioner screws, 1 retention clip, 1 object (about height of gauntlet), 1 screwdriver, 1 pair of tweezers, and 1 pair of scissors

The size of the tensioner screws will vary with the scaling of the hand. Slide the tensioner into the dove tail of the gauntlet and all the way to the front. Insert the tensioner pins into the holes of the tensioner. Make sure the holes at the end of the tensioner pins are facing upwards. Screw the tensioner screws about half way in, which will allow the tension of the hand to be adjustable by tightening or loosening the screws. The tensioner pins should be able to slide forward and backward in the tensioner.

Place an object under the finger of the hand to tilt the palm backwards slightly. The object should be about the same height as the gauntlet to maintain the appropriate tensioner. Using a pair of tweezers helps maintain the tension on the nylon chord while tying the knots. Push the tensioner to the front of the dovetail and all the tensioner pins to the front of the tensioner. Thread the end of the first nylon chord through the hole at the end of the corresponding tensioner pin. Maintain tension on the nylon chord while the fingers rest of the object with the palm tilted backward the entire time. Loop the loose end of the nylon chord around the tense nylon chord and thread it back through the hole of the tensioner pin. This is the beginning of a half hitch knot running through a cow hitch knot. Loop the loose end of the nylon chord back through the knot. Maintain tension on the chord, but leave the knot still loose for the next step. Immediately follow the cow hitch know with a running half hitch through the previous cow hitch knot. Maintain tension on the nylon chord while the fingers rest of the object with the palm tiled backward the entire time. Tighten the knot. Then, tie a 2nd half hitch knot around the flexor line and tighten the knots securely. Make sure the tension is constantly maintained throughout the process and contains the appropriate amount of tension after the knots are tied. Repeat for the all 5 flexor lines and tensioner pins.

Use a pair of scissors to trim the tails of the nylon chords and add the retention clip by clicking it into the back of the dovetail to prevent the tensioner from falling out.

Total Pieces Used: 5 finger tips, 5 proximal, 5 finger pins, 1 palm, 1 thumb pin, 2 knuckle pins, 2 wrist pins, 2 wrist pin caps, 1 gauntlet, 1 tensioner, 5 tensioner pins, 5 tensioner screws, and 1 retention clip

Total Materials Used: 1.5 m flexible elastic chord and 2.4 m non-elastic nylon chord (0.9-1.0 mm)

Total Tools Used: 1 pair of tweezers, 1 pair of scissors, 1 screwdriver, and 1 object (about height of gauntlet)

End Result: functional and assembled hand and forearm with elastics and flexors

Step 8: Applying the Padding

Necessary Items: 30 cm by 15 cm firm foam padding, 1 pair of scissors, 1 pen, 1 X-Acto knife and sandpaper

Place the palm and gauntlet part of the hand on the foam padding to measure and mark appropriate amount of padding required. This is only a rough estimate. Keep the excess padding for any necessary touch ups. Use a pair of scissors to cut out the marked foam padding.

For the palm, cut out a section from the marked foam padding that roughly match the palm. From this section, measure, mark and cut out 1 squarish piece for the majority of palm and 1 long rectangular piece for the front curve on the inside of the palm. For the gauntlet, cut out a section from the rest of the marked foam padding that roughly matches the inside of the gauntlet. Place the padding on the inside of the gauntlet and trace the edge of the gauntlet onto foam for a clean fit.

Cut out and apply the foam pieces. Use the X-Acto knife to help trim the foam parts that are hanging pass the edges and use the sandpaper to help even out the edges of the foam with the edge of the hand.

Total Materials Used: 1.5 m flexible elastic chord and 2.4 m non-elastic nylon chord (0.9-1.0 mm), and 30 cm by 15 cm firm foam padding

Total Tools Used: 1 pair of tweezers, 1 pair of scissors, 1 screwdriver, 1 object (about height of gauntlet), 1 pen, 1 X-Acto knife, and sandpaper

End Result: padded functional and assembled hand and forearm with elastics and flexors

Step 9: Attaching the Straps

Necessary Items: 1.2 m double side velcro (5 cm wide), 4 palm velcro attachment flathead screws, 1 screwdriver, 1 pair of scissors, 1 hot glue gun, and glue sticks

For the palm, use a pair of scissors to cut a strip of velcro that is about 2.5 cm wider than the width of the palm. Use a pair of tweezers to create the "mounting" holes on the velcro strips to help the flathead screw through both the velcro and the tapped holes on the side of the palm. Using the tapped holes on the side of the palm, 2 holes on each side, use a screwdriver to attach strip of velcro via the 2 of the 4 flat heads screw to secure one side of the velcro to the inside of the palm. Repeat for the other 2 holes on the other side of the palm.

For the gauntlet, slide one end of the leftover velcro through the bottom slot of the gauntlet on the "thumb" side of the gauntlet. Leave about 1.3 cm of velcro sticking out on the inside of the palm. Slide the other end of the velcro strap through the top slot. Use hot glue to attach the 1.3 cm lower strip to the gauntlet and to the back of the upper velcro strap. After the 1.3 cm strip is glued, slide the long end of the velcro through the top slot on the other side of the gauntlet. Fold over the long end of the velcro back on itself and glue it down. When folding the velcro over and toward the gauntlet, the strap should be long enough to reach the far end of the gauntlet. It needs an appropriate amount of unfolded velcro to allow the strap to be adjustable. Use a pair of scissors to cut of any excess velcro.

Total Materials Used: 1.5 m flexible elastic chord and 2.4 m non-elastic nylon chord (0.9-1.0 mm), 30 cm by 15 cm firm foam padding, 1.2 m double side velcro (5 cm wide), and 4 palm velcro attachment flathead screws

Total Tools Used: 1 pair of tweezers, 1 pair of scissors, 1 screwdriver, 1 object (about height of gauntlet), 1 pen, 1 X-Acto knife, sandpaper, 1 hot glue gun and glue sticks

End Result: padded and strapped functional and assembled hand and forearm with elastics and flexors

Step 10: Adding the Final Touches

Necessary Items: superglue and 5 Lee Tippi micro gel finger tips

Add superglue to the flexor knots at all 5 finger tips and all 5 tensioner pins. This will prevent the knots from slipping in the future.

Add the 5 Lee Tippi micro gel finger tips to the 5 fingers. This will give the fingers a better grip. As a side note, the original scaling of the raptor reloaded files are a bit small for the Lee Tippi micro gel finger tips. I would recommend scaling the files to a larger size during the fabrication of the pieces.

Total Materials Used: 1.5 m flexible elastic chord and 2.4 m non-elastic nylon chord (0.9-1.0 mm), 30 cm by 15 cm firm foam padding, 1.2 m double side velcro (5 cm wide), 4 palm velcro attachment flathead screws, superglue, and 5 Lee Tippi micro gel finger tips

Total Tools Used: 1 pair of tweezers, 1 pair of scissors, 1 screwdriver, 1 object (about height of gauntlet), 1 pen, 1 X-Acto knife, sandpaper, 1 hot glue gun and glue sticks

End Result: completed padded and strapped functional and assembled hand and forearm with elastics and flexors

Step 11: All Done!

Congratulations, you have completed the Raptor Reloaded Hand. For future reference, the different parts of the hand can be easily replaced at any time when necessary, since some material may not be able to last for a long period of time. For example, the chords may experience wear and tear, which can be easily replaced. Another easy fix is the amount of tension on the hand, which can be adjusted by tightening or loosening the screws. To add on, replacing the velcro with leather straps is an option to upgrade the comfort of the hand. There are many little tweaks that could be changed to accommodate for the user.

As a next step, I would definitely recommend checking out the e-Nable website. It is a wonderful network of volunteers who are also interested in lending a hand or simply creating prosthetic hands, and it has numerous other hand designs available. Good luck with your future projects!