OPENHAND Solidworks source files README

last updated: February 25, 2012
author: Raymond Ma

--About--
Summary of how the Solidworks files were set up and generated, with respect to variable system parameters, configurations, and design suggestions. This is not meant to restrict how users manipulate or modify our provided source files. However, steps were taken to greatly simplify making modifications to basic system parameters and features.

--Overview--
Extensive use of linked variables and configurations were used in the creation of these files. There is an independent file called "params.sldprt" that contains a sketch with basic system parameters linked to an internal configuration. This was used in lieu of text-based global variable files in the interest of speed. 

As of SW2012, there is still considerable lag in rebuilding if utilizing external global variable files. To the authors' knowledge, this has been a persistent software bug with no available solution. 

Unfortunately, use of a reference part for system parameters means that this part file should be open in order to resolve the equations in other part files. The authors hope this minor inconvenience does not hinder development or use.

--System Parameters Overview--
The primary system parameters cover the basic system parameters for underactuated fingers, as well as basic manufacturing parameters. System parameters may be changed directly in the default configuration or children configurations (under Configurations tab in SW, please consult online SW documentation for more details)

--Finger/Hand Parameters--
K1/K2 - thicknesses of flexures
stiffness ratio - ratio of the joint stiffnesses approximated by basic beam stiffness relations
R1/R2 - joint transmission radii. Approximately the normal distance between the tendon routing holes and the center of the flexure
transmission ratio - usually kept to 1, but the relation between the joint transmission values
finger length - total length of the finger
L1/L2 - link lengths for the separate phalanges
linkage ratio - ratio between the finger linkages (human phalanx ratio is approximately 0.67)
T1/T2 (degrees) - initial offset angle for each finger relative to base 
LB - determines amount of separation between opposing finger bases


--Manufacturing Parameters--

width destroy - thickness of shell material that constrain the flexure mold and will be removed after printing
width keep - minimal thickness of RP material that will resist bending (3mm for Stratasys)
pulley diameter - diameter of nylon pulleys used in transmission
pulley thickness - thickness of pulley for slots. Slots should be dimensioned such that pulleys spin freely but do not allow slipped tendons to get caught in cracks
flexure anchor - extrusions for preventing peal-out of the flexure bases
finger depth - should be at least (pulley thickness+2*width keep)
finger height - should be greater than chosen flexure size
finger pad thickness - thickness of fingerpad material cavity
base diameter - should be minimal but large enough to accommodate footprint of fingers
pin diameter - diameter of steel pins used as tendon anchors and bearing surfaces

--CAD practices--
Steps were taken to ensure that all components were fully defined in the SW context. Each feature is named appropriately and divided such that there were as few confusing or redundant features as possible. Arbitrary numerical values were avoided as much as possible. Each dimensioned value should be tied to a system parameter and/or a pre-existing part feature wherever possible.

--CAD limitations--
It should go without saying that while arbitrary configurations may be added/selected, the authors cannot guarantee that the mechanism can be built (either physically or in CAD) with your desired system parameters. If a significant use case arises which cannot be fulfilled by the current framework, please contact the authors with as much detail and specification as possible, and we will do our best to make appropriate modifications before the next release.



