README_ENG.md

makers prosthetic hand

Every year in France, 80 to 100 babies are born with a malformation. We call it agenesis. Prostheses are very costly: between 41.000€ and 82.000€ for an artificial hand ! And because children are growing fast, they would need to change it every 2 years. Therefore, a very few number a kids with agenesis have one. The ultimate paradox is that prostheses are not appropriate for hostile environments such as water or sand. Environments that kids love!

The association e-nable, a network of passionate volunteers, introduces kids to makers. The goal being to teach kids how to make their own opensource “raptor” prosthetic hand for less than 50€.

This bootcamp gave us the opportunity to make a test kit of the “raptor” prosthesis for a clinic while telling the story of an opensource object.

Video

Material

• Download the plastic hand pieces to 3D print on e-nable website
• Rubber strips
• Nylon threads
• Screws

You will also need:

• 1 flat-head screwdriver
• 1 flat tweezers
• 1 cutter

Step 1 - 3D print the hand

3D print the hand using these files.

Step 2 - Phalanges & fingers assembly

• You will have to assemble 5 phalanges 1, 5 phalanges 2 and 5 rivets.
• Sand each part to smooth the contact points/joints (fix 3D printing irregularities).
• To make a finger, take one part of each type :
  • Phalanx 1 = fingernail phalanx (distal phalanx)
  • Phalanx 2 = phalanx directly connected to the hand (proximal phalanx)
• The smooth part with the slot of phalanx 2 must be oriented towards the bottom. The horned element will be above the palm articulation. You need to plug the other side with phalanx 1 (side without the horn).
• Adjust the rivet by pressing the round side into the rectangular hole first. Once pressed all the way through, the rectangular shapes are plugged together and the rivet can not slip out.

Step 3 - Wrist & palm assembly

• Take off the wrist support and clean the articulation asperities.
• Put the back of the hand and the wrist on the table, palm towards the you.
• Adjust the wrist in the palm in order to align the holes.
• Adjust the rivet by pressing the round side into the rectangular hole first. Inside towards outside. Once pressed all the way through, the rectangular shapes are plugged together and the rivet can not slip out.
• With the tweezers, pinch the rivet outside end to reduce its diameter. Now you can insert the plastic nut. Take off the tweezers to let the nut smooth side touch the hand.

Step 4 - Mikado box

• Slide all the way the box from the back to the front of the wrist usign the rails: the round holes towards the back.
• Slide the "trident" rails at the back to lock the box.
• Take the 5 sticks and slide them into the box holes. The sitcks holes are oriented towards the outside like the picture.
• Using the flat-head screwdriver, screw each stick from the round side of the mikado box.
• Your 5 sticks are now in place.
• For the next steps, we will link only 3 sticks to nylon threads. The goal is to get a more synchronised finger move.

Step 5 - Hand fingers assembly

• Start with the little finger.
• Plug the little finger into the dedicated palm spot. Align the holes.
• Adjust the big rivet: plug the round side first in the rectangular hole. Stop mid-way, just before the ring finger. Once pressed all the way through, the rectangular shapes are plugged together and the rivet can not slip out.
• Repeat the operation for the index and the middle fingers.
• The 2 big rivets can have a printing default: you may need to recut the slot using the cutter.
• Finish with the thumb usign the smallest rivet.

Step 6 - Rubber strips pulling

• Start with the little finger. Put the elastic into the finger bottom hole. The wire passes through the phalanx 2 et goes out on the other side: the articulation. It goes on top of the phalanx 1 and then underneath.
• Make a reef knot to clip the elastic.
• Tighten the wire to get a good joints resistance.
• Take the other elastic end and slide it into the rail. The rail starts at the bottom of the palm (hole) and connects two fingers. Pull the thread on the back of the hand and repeat the same process for the ring finger.
• Do not forget to make a reef knot at the end of each finger.

Make sure the finger works well before putting the elastic on the other ones:

• Manually fold the fingers in the palm then release.
• The finger should go back to its original position automatically.
• If it doesn't work, first try to tighten the elastic. Then file the joint to give more space and allow the two different parts to slide.
• Make sure to keep some flexibility.
• Repeat the steps for the index finger and the middle finger with the second elastic.
• With the thrid elastic, repeat the steps for the thumb.

Step 7 - Nylon threads knotting

• Make a reef knot at the end of the inside phalanx 1, pass the elastic inside the phalanx 2. Then go through the palm and follow the elastic.
• Enter the tunnel, always following the elastic and make a reef knot on the associated stick hole.
• Repeat the same process for the other fingers. For the finishing touches, cut the elastic exceeding.

Step 8 - Velcro strap positioning

You will need six velcro straps.

• The bottom velcro straps for the wrist :
  cut the velcro straps into two pieces : one of 13cm and the other of 11cm.

• Pass them through the the wrist slots: the longer one will cover the other.

• The upper velcro straps for the palm :
  cut the velcro straps into two pieces : one of 9cm and the other of 5cm.

• Pierce the velcro straps and screw them to the hand.

• Cut little pieces of velcro strap and use them to hide the upper screws.

• Place the bottom velcro strap.

Step 9 - Finishing touches

• Put some hot glue on the nylon thread knots to protect them.
• Clean the prosthetic hand cutting off the exceeding wires.

Well done ! The prosthetic hand is finished.

Notes et références

• E-nable official website : https://e-nable.fr/
• Makers' lab official website : http://makerslab.em-lyon.com/