Hello this is 3DMeister Julius. Enjoy my project and forgive my english!
This is an experimental prototype, a Manual Controlled Mechanic Cable Driven 6-axis Robotic Arm. I named it 3DM6X. All 6 axis are connected with two pull cables wich are connected to one slide controller. 3 rotation axis and 3 hinge axis, driven by the closed loop cables with the fingers, can turn and lift at the same time.
The target of this experiment was to find out more about multi axis robot arm movements, possibilities and fun.
You are welcome try this at home, i hope to see enhancements, don't blame me, a lot can be done with the schematics, maybe start with only 2 axis.
Download and check the 3D model from Grabcad or Thingiverse.
Look at recent 6-axis tests, movements with this gadget:
Watch how i made this toy.
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Step 1: Describtion
The controls are on the base of the arm. This is where all cable loop. One point is connected to a slide knob. By operating the slide, the loop pulls the cable in one direction and therefor it lifts or rotates the axis on the arm.
All cables must go through the center of the arm and they must bend in the center with each axis. The rotation axis twists the cables so they must be sorted well for minimum friction in any position. The hinges can move between an 180 degree angle and all rotation axis can turn more than once.
I have a very good result in the first test with this multi axis arm, without noticeable interference between the cables in all possible positions of the arm.
The structure is made of plastic with very good sliding abilities. The cables are also made of plastic, a plump cord with few thick fibers wich can hold about 15kg .
The slide controllers hold there position and the tension on any cable after lifting and moving the axis. This happens with an anchor on the slide control knob. At the end of the arm on the last unit, there is another hole for the tools to activate by another cable going down the whole arm to the control box in the base.
Step 2: Movements, Tests, Possibilities
First try, doing things with the 6 axis arm; Its not easy and It takes a lot of patience.
Although all axis can be controlled at the same, its to heavy for six fingers moving it in different directions.
All axis are very easy to lift and turn one by one, two at the time works fine, also tree is doable.
This is not bad considering the cable going over multiple rounded corners, especially with angled axis.
More Videos about the movements and usability tests.
Step 3: Parts, Materials
Nearly all parts are made of plastic with very good sliding ability. The plastic parts can be made by hand, with the CNC machine and i am sure they can be 3D printed.
There is the base with the controller parts and only 2 different types of hinges on the Arm. The arm is constructed with 6 elements for each axis. Some plastic bolts are needed to redirect the cables and to make the hinges.
All hinges are connected with 2 plastic cables, they loop at the end where the controllers are connected, in the control box.
The cable is a plumb cord with wich can stand 15kg. Its a plastic wire with few and thick windings, and no fibers.
The control button has a slider and an anchor.
The anchors for the controls are made from aluminium on the CNC machine.
A spring activates the anchor on the slidable control knob.
The knob is screwed on the anchor through the control box, between is the slider wich is connected to the cables and the axis, wich get pulled when moving the knob.
A rubber band can be used to lift the hinges into center position. This minimizes the load on the pull cables.
The cables are threaded trough drilled and molten channels and than they are mounted with tooth picks.
Step 4: Tools and Machines
For this project you need a something to cut, drill and to turn the plastic into shape. I made them with my CNC machine. Get the 3D model for this finger gadget on Grabcad or Thingivers
The aluminium anchors on the controllers are CNC machined but maybe there is another solution for this. They hold the cable in position when the slider controls are not in use.
And some small tools for assembling are needed.
Silicon spray is perfect to eliminate most of the friction on the plastic cables and hinges.
A lighter and a steel wire to melt the cable channel.
Step 5: 2 Different Types of Joints
Two types of hinges are used in this six axis arm. The rotation and the leverage hinge.
The first on the bottom is rotating, driven by the first cable in the base wich is winded on the bolt from the first arm element. So when pulling one side, the element rotates in one direction. Pulling the other side, it turns back.
The second leverage hinge has its two pull cables on the round end of the element. The pull cables are coming from the lower element out of well positioned holes.
Step 6: Cable Connection
Starting from the bottom, the first rotation axis in the base, the cable is wrapped around the shaft of the first moving element, going with a loop trough a hole in the shaft, which prevents the cable from slipping trough. Than, the cable is guided through holes in the lower element, in this case the base, so that both cables pull, tangential of the axis shaft, towards each other.
Step 7: Cable Connection Second Hinge
The second type of hinge on this robotic arm is a pin joint with the drive cable pulling from the lower element.
The cable runs in a groove of the outside the axis center of the driven element and into a well positioned hole down to the bottom, the base.
A tooth pick is used to clamp the cable to the driven elements.
Step 8: Last Hinge
The same as the first and all rotating hinges, with the cable going through the center of the whole arm.
Step 9: Looped Cables
The loops for each axis are coming from the center of the arm going into the base. Two bolts redirect the cables in any direction and along the control slits for the slide controls.
Step 10: Controller
The control knobs slide along grooves, aligned with the cables.
The button with an anchor is pushed outwards with a spring therefor the slider works only while pressing the control knobs. This mechanism holds the arm in every rest position.
Step 11: Optimizing
I could minimize the weight by 1/3 drilling big holes into the structure.
Silikon spray for the cables and all mechanic parts made everything easier to move.
No edges for the cable holes in any direction to minimize friction.
Rubber band support for the pin joint hinges, they can pull up the weight of the arm and make it easier to control the multi axis robot arm.
Well sorted cables in Zero-Position.
Step 12: Next Step
3DM6X currently is a completed experimental prototype.
The experiment was a success, next step will be to make a Real Cable Driven Electric Powered Robot Arm.
Ideally with stepper in the base and encoder on the axis.
Different sizes for bottom an top joints.
Different lengths for the structure elements.
Ball bearings for the hinges and and the bending points of the strings.
Different material for the structure.