3D Printed Hand Automatic Scaling Tool - 3D PHAST

INTRODUCTION

This excel generates the parts for a scaled 3D hand prosthesis to be attached by a bolt to the patient's arm socket.

This tool was created with several proposes:

• Adapt the prosthesis size to the user hand size, in order to reduce the visual impact of the prosthesis

• The prosthetic hand is joined by a standard bolt to the arm socket produced in FUNPROBO with the 3D print hand prosthesis. The arm socket manufactured by mold from the patient is strong, reliable and comfortable since is personalized for the user.

• Since hand and arm are independent can be easily replaced in case one of them is broken or should be replaced

The tool consist in a xlsm file with a MACRO, the fields in yellow should be filled in order and press the button to generate the files.

These excels generates Openscad files that modify the STL reference files and create the STL ready to print. To create the STL ready to print only need to double click the .bat file generated with the openscad files.

The 3D model will have the patient hand size and ready to be bolted to the arm socket

I created this tool during a voluntership in FUNPROBO. This NGO is located in La Paz and provide Free Prosthetics to bolivian amputees, For most of them FUNPROBO is the only chance to obtain anprosthetics to let them work again and obtain again independence. FUNPROBO manufactures locally in La Paz all kind of leg prosthetics and train the amputees with physical therapy for their correct use.

FUNPROBO is working thanks to an amazing staff and volunteers coming from all over the world. Please check the website to see the encouraging patients stories, also I recommend to like the FUNPROBO facebook site to be updated of the daily progress of this inspiring NGO.

If you like this initiative there are many ways to collaborate with them, check the website to learn how:

https://funprobo.com/

Or you can donate throught the Facebook website

https://www.facebook.com/ProstheticsforBolivia/

DEVELOPMENT HISTORY:

Looking for an affordable way to create hand prosthetics for arm amputees, we decided to create a 3D printed hand prosthesis to be bolted to the arm socket.

The arm socket is manufactured by FUNPROBO prosthetists technicians from patient arm mold, this arm socket fits perfectly to the patient arm and it is more stronger and quick to produce than the 3D printed solutions

The hand is based in a full palm version of Flexyhand, modified with new wiring tubes.

The Openscad files escalate the reference files and perform geometric modification to create support and the nut pocket, the files are executed by a .bat file producing STL ready to print

TOOL EXECUTION

Excel should be filed with the measurements of the patient indicated in the pictures and also some parameters can be modified for more personalization.

This tool generates the STL files of a hand prosthesis with the following features:

• The tool use the hand measures to create a 3d print with the same size of the other patient hand.
• The hand model includes a nut pocket to be fastened to the arm limb socket, the nut size can be selected
• Internal supports in the nut pocket are included in the STL to correct printing.

You should have excel and the MACROS allowed.

You should have Openscad installed before run the MACRO. Openscad is an open source program to generate and modify 3D models. You can download it here:

http://www.openscad.org/downloads.html

The Openscad files are text files with the commands to modify the STL located in the folder 00_references_models

The excel generates the Openscad files .scad and the executable .bat, once run the STL ready to print will be created.

The process to obtain the model is:

• Check that openscad installation path is right
• Check that 00_references_models path is right
• Input the measurements of the hand
• Input the nut size, better if you let the automatic size
• Run the MACRO
• Run the .bat file and wait for all STL to be created

The models generated are based in Flexyhand and Flexyhand2 by Gyrobot and full palm by
Adolph

PRINTING

Rigid material like PLA or ABS for Hand, Fingers, Nut cover and Thumb

Flexible material like TPU93 for Hinges

Some flexible materials are not rigid enough to move the fingers back after wire tension is released. TPU93 is rigid enough and reliable for this use

The big hinges between arm and first finger phalanx are curved, assemble them pointing outward to increase the springback. Check the correct position before assembly

The nut hole is created with supports inside, these supports should be removed to insert the nut. The use of self locking nuts is better but it can be tricky to tight the nut.

This tool is created by Juan de las Heras and you can contact with me in this email Jdelasheras83@gmail.com

You can follow my 3d print and maker account @3dprintsdiary on instagram

https://www.instagram.com/3dprintsdiary/?hl=en