While this version is 3d printed, it could also be made using traditional hand methods.
Step 1: How It Works
I was experimenting with various ways of 3d printing self-assembling hinges for future use in robot arms and legs. Making some hinges that can lock in place seemed like a good way to test the strength of the structures.
The helping hand has six configurable, lock in place, arms with interchangeable grippers. While this version was 3d printed, a similar jig could be made using acrylic or other plastic sheet material. It could even be made out of thin plywood. Three layers could be laminated together to make the arms.
Step 1 pic shows it set up for soldering with flashlight and magnifier. Pic 2 shows it folded up.
Step 2: Tools and Materials
100% silicone caulk and corn starch to make Oogoo. Details on making Oogoo can be found here:
24 4-40 x 1" round head screws and nuts
6 4-40 x 3/4" round head screws and nuts
2 1/2" diameter x 3/8" long neodymium magnets
Step 3: Making the Arms
Each arm is printed as one self assembled piece (arm.stl). The conical pins hold the hinges together even without the screws.
All 3d printed pieces were printed using a Makerbot Replicator 2 with the following settings:
Standard resolution with a raft
.2mm layers-standard resolution
If a space of .01" or larger is left between movable parts, all kinds of movable mechanisms can be 3d printed including hinges, shafts, and bearings.
Print the Knobs
The knobs (knobs4-40.stl)are designed to fit a 4-40 size screw tightly. Do not over screw and strip the hole.
Step 4: Making the Interchangeable Grippers
Pic 2 shows the two halves of a gripper and the silicone donut.
Pic 3 shows how the silicone donut was cast using 3d printed form: donut.stl. Oogoo works well to cast the donut. A 3 silicone Caulk to 1 corn starch by volume produces a silicone that will set up in two or three hours. More details on using Oogoo to make rubber bands can be found here: https://www.instructables.com/id/7-Things-To-Fix-Or-Do-With-Oogoo/
Most of the rubber donuts were made using Dragon Skin 20 silicone which pours real nicely and is available from Smooth-On.com.
Step 5: Making the Magnetic Grippers
You can print out maggrip.stl and then glue in 1/2" diameter magnets. Or you can make your own magnetic grippers in a shape that suits your needs.
Step 6: Making the Base
The bottom of the base has been hollowed out to allow for a piece of sheet metal to be glued in with silicone caulk. The thicker the sheet metal, the better it will attract the magnetic grippers.
A 1/16" thick silicone pad can be cast using Oogoo and the mold: hexmold.stl. It can then be glued on to the base using silicone caulk. This provides a grippy surface so components can be easily held in place.
Step 7: Soldering
Pic 2 shows how the magnetic grippers can be used to hold wires and small components to solder them. The silicone pad on the base can handle the heat of the soldering without melting.
See also the step 1 pic for a full soldering setup.
Step 8: Painting and Photography
Pic 2 -The jig can also be used to hold objects or a camera as an aid in macro-photography.
Step 9: Other Possibilities
Pic 2 shows an experimental arm that uses a ball joint for the gripper. It was all printed as one piece. While it worked, it had problems. When the screw was tightened, it tended to permanently dent the ball. So a much larger joint would have to be used that squeezes uniformly around the plastic ball.
Pic 3 shows a puzzle box design with hidden conical hinges. The box is printed in one piece.
Pic 4 shows the printed box closed.