🔧Micromanipulator
This page documents our build of an open source micromanipulator that can be used for both the lithography stepper and the 2D crystal stack robot.
Summary
This is a replica of version 4 of this open source project: https://github.com/0x23/MicroManipulatorStepper. Almost all resources for assembly can be found here.
BOM
Below is a list of materials used that worked for this particular build. Parts of the table are copied from the original repository.
Mechanical
Neodymium Cylinder Magnet
51
Ø3 mm, h = 5 mm
Diametrically (through diameter) or Axially Magnetized (through thickness) magnets.
Electronics
1N5819 Diode (TH or SMD)
1
If you want to keep the RPI and motor power source separate, don’t solder on the diode.
3d Printed
Motor Horn
3
0.4 mm+ nozzle may require post-processing
RubberBandCollet
12
0.4 mm nozzle, 0.1mm Layer height + may require post-processing
BallJointMount
6
0.4 mm nozzle, 0.1mm Layer height + may require post-processing
Motor Mount
3
End Effector
1
Base Block
1
Tools
Super glue
Wire stripper + crimper
Soldering Iron
3D Printer
Calipers
Hammer
Blade
Drill
CAD
Same cad files were used as in the repo aside from the base of the stage.
PCB
Version 4 requires 2 PCBs: the control board and the ball joint plate PCB. We hand soldered the SPI board but it would be a lot easier to just order the SPI board too.
The PCBs can be found in the same repository.
Assembly
For general assembly guidance, please refer to the two videos from the original creator:
Version 3: An Open Source Motorized XYZ Micro-Manipulator - Affordable sub µm Motion Control
Version 4 Additions: Better Ball Joints - For the Open Micro-Manipulator
We would also like to provide some more tips from our experience of putting together a version 4 micromanipulator.
Motor Horns
Each motor horn should be able to fit 17 cylinder magnets like the image below. We used super glue for this step to glue the magnets to the motor horn. A trick is to apply super glue from the top of the magnets and allow it to pool into the cracks for a strong and stable connection.
When assembling the motor horn, remember to put in the metal dowel pin for homing in the middle (highlighted in the red circle). The insertion of the pin should satisfy the following:
The pin should stop the motor horn when hitting the 2 ends of the groove (highlighted in orange underneath)
The pin should not be touching the back wall of the groove otherwise there will be extra friction during rotation.
Rods
Sanding
The first step of creating the rods is to sand them down so they are of equal length. Here we printed out the 2 rod sanding jigs from the repository. Initially, use coarser grained sanding paper just to get the length down. Then, switch over to finer grained sandpaper and add some water. Try to get the surface to be as smooth against the jig as possible. There should be no noticeable height differences between the two when we touch it.
Jig 1
Jig 2
Sharpening
We sharpen both tips of the rods such that they leave 1mm in diameter at each tip. This step can be quite tedious purely due to the fact that we need to ensure all rods maintain equal lengths. The MicroManipulatorStepper repository provides special CAD jigs that we use to sharpen the rods.
Print the blade carrier and rod guide from this link and collect some materials
Follow the video “Better Ball Joints” for assembly steps, which includes adding the blade to the blade carrier and positioning the rod for sharpening. imgs: source
Screw them together
Driller carries rod, insert rod into sharpening hole
Drill until the tip is 1mm wide
Tips
1) If you’re drilling and the tip is jutting inwards near the center (outer area is taller than inner), then you're likely drilling in the wrong direction
2) To get precise sharpening (not loose equal length for all rods), count how many seconds it took to sharpen the first successful one, then use that as a measure for how long you sharpen for next time
3) Patience is key. Trust the process. And most important of all, be safe.
Denting
One might consider this step to be one that tempts your patience the most. Although seemingly simple of a step, it is one that requires not only determination, but also attention to small details. For the magnetic balls to connect to the rods and ball alignment disc PCBs, we must form a 0.2mm radius dent at both tips of each rod.
Source: https://www.youtube.com/watch?v=NM2KXvRGmpg
To complete this step, first print out the necessary jigs to complete this step. Next, find a caliper to use, as it’ll become your source of measurement verification (not really, but we’ll explain this later).
Print Jigs:
Steps:
Fit caliper clamps into the teeth of the caliper, this may require some brute force.
Then screw them on tightly.
Drill hole into collets to ensure rod fits into it, then assemble them with the PCBs, and superglue the balls on after
Put Rod in Rod Guide, attach assembled collets to both ends of the rod. Then fit them to caliper, and attach the rubber band
Set your caliper to 0. Use a hammer to bang one side against your “table” like so. Hammar until it reaches 0.2mm in delta
Tips
if your dents are bad, many reasons:
Not hitting caliper and jig hard enough (going past 0.2mm is fine)
Rod collet not assembled well (3D print is fine, but breaks easily)
Human error
For us, instead of hitting the dent on both sides at time, denting 1 side at a time worked well, we just replaced one collet with a modified collet that doesn’t have the hole.
Rubber band collets
The next step is to push the rubber band collets onto the finished rods. Remember to orient the rounded side of the collet towards the two ends. For our build, it was oriented incorrectly and when we were trying to hook up the rubber bands, they would keep slipping off easily. Aside from this initial difficulty to assemble the stage, the error did not affect functionality so we did not fix it.
Since the holes on the collets are very small, we’ve found that using the rod as a drill tip and drilling it through the rubber band collet helps with sliding it on. It's also important to place the collets at the same distance from the edge for each rod.
Here is a picture of the rods with the rubber band collets on the wrong way :
This is the correct way: source
Electrical Assembly
Connections
The path: Encoder - SPI board - control board should be as short as possible. Keep the wire length to be less than 25 cm if possible. This is because SPI protocol does not do well with off chip connections and so we must try to keep this connection short for the communication to remain stable.
The encoders require JST 1.25mm pitch connectors. Since JST connectors are harder to disconnect, we convert it to a dupont connection which we can then easily plug/unplug. Below is an image of the connection:
Note: for the SPI board connections, refer to the PCB schematic in the original repository.
Last updated