purely mechanical arm

overview :

this project is a fully functional mechanical arm that just uses bearings and friction to rotate its joints, instead of using any electronics.

this project is has function as a (sort of) helping hand for holding small things or electronics or whatever with a geared grabbing mechanism and entirely moveable joints. it also looks cool if you want to keep it as a showpiece or something :)

why a mechanical arm? :

modelling a mechanical arm let me research some more into kinematics and joint motion under different degrees of freedom (e.g. each of my joints only use 1 DOF, since i'm using ball bearings - but it adds to 4 DOF overall).    

function & how to use :

the function of the mechanical arm is similar to how a helping hand works, where a component or circuit board or whatever you want can be clamped down with a grabbing mechanism, the only difference being the position of the mechanical arm being able to be moved to wherever needed.

the arm is very straightforward to use, just rotate each arm and the grabber mechanism around their respective axis, then (since the grabber is gear-driven) you can open one side of the grabber and both sides will open - with the same thing happening when clamping an object to the hand.  

overall dimensions :

the overall dimensions of the model are as follows (dimensions in mm).

404.00 x 100.00 x 389.00 

note: this is NOT print in place, so each individual part will fit in a 256mm^3 build volume, but the entire build IS bigger than 256mm^3 :)

model build requirements :

• 1 x static platform

• 1 x twisting platform

• 2 x bottom arm half

• 2 x top arm half

• 2 x grabber chassis half

• 1 x grabber top

• 1 x grabber bottom

• 5 x 608zz bearings

• 3 x m8x1.25 nut

• 2 x m3x0.5 nut

• 1 x m3x1.25x60 bolt

• 2 x m3x1.25x35 bolt

• 2 x m3x0.5x20 bolt

model build instructions :

glue both halves of the bottom arm together

glue both halves of the top arm together

glue both halves of the grabber chassis together

glue the outside of a bearing to the inside of the static platform

glue the inside of the bearing to the pin of the twisting platform

glue a bearing to each side of the twisting platform

glue a bearing in the top circular slot of the bottom arm

glue a bearing in the bottom circular slot of the grabber chassis

thread the m8x60 bolt through the twisting platform's bearings and the bottom arm, then secure with an m8 nut

thread an m8x35 bolt through one side of the top arm and the bearing side of the bottom arm, then secure with an m8 nut

align the gears in both grabber arms together and align with the holes in the grabber chassis, then thread the m3 bolts through and secure with the m3 nuts

thread the final m8x35 bolt through the top end of the top arm and the hole of the grabber chassis, then secure with the final m8 nut.