This Instructable is about a linear actuator with a rotatable shaft. I made it to build a motion phantom (1) and could not find anything alike.
- Linear motion: 45 mm
- Rotation: 180 degrees
- Costs: less than $50, whereas most goes into the servo motors
The LnR-Actuator is made of parts you find in every hardware store. For 3D printing you can use PLA. The LnR-Actuator can be controlled by an Arduino (1) and its Servo library (3). If you want to control up to 8 LnR-Actuators (that’s 16 servos), you should have a look at the Adafruit Servo Shield (4).
To build it you need a standing drill machine and a metal drill 4.2 mm. M4 screw tap and die. To drill through the holes of the 3D prints, if necessary, you may need drills with diameters 1 mm, 1.5 mm, 3 mm, 3.3 mm, 5 mm, 6.2 mm and 6.5 mm.
Servos motors do not require additional encoders and can be easily controlled directly by software with a PWM signal. The described LnR-Actuator is using the servo arms that come with the servo motors MG946R and MG90S from TowerPro. I recommend using original servos and not clones; the clones I used produced a lot of noise on the 5V power line, they were less accurate, made more noise and stopped working after a couple of hours.
Step 1: Bill of Materials
1 x Standard Servo Tower Pro MG946R. Comes with servo arm, 4 M2 mounting screws and 4 d3 brass hulls
1 x Micro Servo Tower Pro MG90S. Comes with servo arm and 2 mounting screws
11 x M2 x l10 mm flat headed screw
4 x M4 washer
6 x M4 nut
2 x Snap ring d4 mm
1 x Paperclip d1 mm
1 x Wooden rod d6 x l120
2 x Steel or aluminum rod d4 x l166 with M4 x l15 thread at one end
1 x Steel or aluminum rod d4 x l14 with snap ring notches at a distance of 8 mm
1 x Steel or aluminum rod d4 x l12
1 x LnR-BaseLeft or LnR-BaseRight
1 x LnR-Hood
1 x LnR-SliderLeft or LnR-SliderRight
1 x LnR-SliderLeftTop or LnR-SliderRightTop
1 x LnR-ExtensionArm
1 x LnR-Flange
2 x LnR-ServoFixator
Legend: l:length in millimeters, d:diameter in millimeters, LnR: 3D printed part, see step below
Step 2: 3D Printing
You either need to print the left-sided or right-sided parts. The pictures in this Instructable show a left-sided LnR-Actuator (Looking from the front, the wooden rod is on the left side).
If you do not have a 3D printer, I recommend looking for a 3D printing service nearby.
Step 3: Slider Bearings
As bearings, the M4 nuts are used! For that, you drill out the (M4/3.3 mm) holes with the 4.2 mm metal drill. Press the drilled out M4 nuts into the openings in the slider.
Glue 2 M4 washers onto the slider and the slider top.
Step 4: Mirco Servo and Extension Arm
Mount the Micro Servo onto the slider. Press two drilled out M4 nuts into the extension arm.
Step 5: Slider and Rotateable Shaft
Assemble sider, extension arm and slider top.
The flange is attached to the Micro Servo arm and then mounted to the Micro Servo. Drill a 1.5 mm hole into the wooden rod (bottom right on the picture), otherwise the wood will break.
Step 6: Servo Joint
Drill a 4.2 mm hole into the Standard Servo arm. A M4 washer come to each side of the bearing (the M4 nut) of the extension arm. One snap ring will be below the servo arm, one at the very top. I hope you get the picture.
Step 7: Servo Mount
The Standard Servo is attached to the LnR-Base. The screws for the servo go into the messing hulls, through the LnR-Base and into the fixators which are put below the LnR-Base.
Step 8: Longitudinal Motion
Cut two M4 threads into the 3.3 mm holes of the back plane of the LnR-Base. The metal rods are then pushed through the 4.2 mm holes in the front plane, through the bearings of the slider and are fixated with the M4 threads in the back plane.
Step 9: Hood
That is the LnR Actuator!
To fix the Micro Servo cable, a part of a paper clip is used. Mount the hood onto the actuator and you are done.
Step 10: References
(1) Picture of the GRIS5A Motion Phantom with 5 LnR Actuators: https://github.com/mrstefangrimm/GRIS5A/blob/mast...
(2) Arduino: https://www.arduino.cc/
(3) Servo library: https://www.arduino.cc/en/reference/servo
(4) Adafruit ServoShield: https://www.adafruit.com/product/1411 and https://github.com/adafruit/Adafruit-PWM-Servo-Dri...