Tapsterbot 2.0 is Jason Huggins' open-source delta-bot. It will help test mobile applications on phone/tablet platforms, by manipulating a capacitative stylus which will touch the screen.

In this Instructable, we will give step-by-step instructions for putting the robot's Arms together

Step 1: Parts for the Arms

The robot has 6 "Forearms", which attach from the Servo-Arms to the Stylus Holder. You will need the following parts to complete this phase of construction (see BOM for details about hardware):

24 rod magnets
6 ball bearings
3 Servo Arms
12 Couplers
1 Stylus Holder
6 threaded rod segments

The ball bearings are only used to give the magnets a recessed, snug fit, and are not permanently attached during this step.

Step 2: Insert the Rod Magnets Into the Servo-Arms

Note about polarity: the Couplers each hold a rod magnet, which will connect to either the Servo-Arm or the Stylus Holder. It is recommended that you ensure the magnets "attract" between the connecting components. More detail will be shed on this in the specific steps.

Ensuring that the rod magnets have the same polarity facing in the same direction, stick the magnets to one side of a desk-mounted vise
Holding one Servo-Arm in your hand, line the rod magnets up with the holes
With your other hand, begin to tighten the vise, ensuring the magnets are sliding in the Servo-Arm holes
Do not over-tighten! Clamp the magnets in until they are flush with the plastic, but stop there
Open the vise up enough for a ball bearing to be placed over each magnet
Slowly clamp the ball bearings down on the magnets, stopping with the ball bearings sit just snugly in the plastic

This last step will cause a slight recess in the magnet holes, which allows the ball bearing to fit snugly in place while still allowing it to operate effectively as a joint

Now perform the same set of steps for the 2 remaining Servo-Arms

Step 3: Insert the Rod Magnets Into the Couplers

Note about polarity: Make sure that the end of the magnet that will attach to the Servo-Arm is the correct polarity, i.e. that it will attract to the Servo-Arm, not repel

Similar to how we inserted the magnets into the Servo-Arms, attach the rod magnet (with the correct polarity) to the vise
Line up the magnet with the larger hole on the Coupler, which you will hold in place with your fingers
Slowly tighten the vise, ensuring that the magnet slots smoothly into the hole
Do not over-tighten! Clamp the magnet in until it is flush with the plastic, but stop there
Open the vise up enough for a ball bearing to be placed over the magnet
Slowly clamp the ball bearing down on the magnet, stopping when the ball bearing sits just snugly in the plastic

This last step will cause a slight recess in the magnet holes, which allows the ball bearing to fit snugly in place while still allowing it to operate effectively as a joint

Now perform the same steps with the remaining 11 Couplers. As the picture indicates, you can likely do multiple Couplers at a time, as your vise size permits

Step 4: Insert the Rod Magnets Into the Stylus Holder

Note about polarity: Make sure that the end of the magnet that will attach to the Stylus Holder is the correct polarity, i.e. that it will attract to the Coupler, not repel

Similar to how we inserted the magnets in previous steps, attach 2 rod magnets (with the correct polarity) to the vise
Line the magnets up with 2 of the holes in the Stylus Holder (as shown in the picture), which you will hold in place with your fingers
Slowly tighten the vise, ensuring that the magnets slot smoothly into the holes
Do not over-tighten! Clamp the magnets in until they are flush with the plastic, but stop there
Open the vise up enough for a ball bearing to be placed over each magnet
Slowly clamp the ball bearings down on the magnets, stopping when the ball bearing sits just snugly in the plastic

This last step will cause a slight recess in the magnet holes, which allows the ball bearings to fit snugly in place while still allowing them to operate effectively as a joint

Now perform the same steps with the remaining holes in the Stylus Holder

Step 5: Construct the "Forearms"

This step will see the completed Forearm pieces, which will be used to connect the Servo-Arms to the Stylus holder in the "delta" configuration that is our robot's signature

Note: For this step, Gentle Jaws are recommended. If none are available, you can probably get the desired effect by double-wrapping (with paper towels) the portion of threaded rod that makes contact with the vise jaws.

Place the threaded rod in the vise (see note above) and tighten until it is immobile
Thread one Coupler onto each end, being careful to screw each Coupler a roughly even amount. If you tighten one end much more than the other, the rod will start to push the magnet out of the other side
Continue to tighten the Couplers until the entire Forearm is 145mm long

Ensure that the threaded rod has not pushed either magnet out of its Coupler! The magnet needs to be slightly recessed in order for the joint to function properly

Step 6: Your Parts Should Look Like This

Now that you've completed the steps, you should have the following:

3 Servo-Arms with recessed rod magnets (with the same polarity!) in each hole
1 Stylus Holder with 6 recessed rod magnets (ditto polarity)
6 Forearms, each with 2 Couplers
Each Coupler should have its recessed rod magnet, which should attract the Servo-Arms and Stylus Holder

Revel in your accomplishment. It's time to attach the Servo-Arms to the Servos!