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This guide describes how to assemble the complete actuator module from the six sub-assemblies prepared in the previous steps.

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Overview

The actuator assembly process combines:
  • Motor stator and rotor
  • Motor shaft assembly (with pulley and codewheel)
  • Encoder
  • Center pulley and output pulley
  • Timing belts (150mm and 201mm)
  • Shell housing (base and cover)
  • Timing belt tensioner rollers
Final result: Fully assembled actuator module weighing approximately 160g (with 30cm wires).

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Prerequisites

Before starting, ensure you have completed:

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Required Components

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Sub-assemblies (6)

  1. Prepared motor stator with wiring
  2. Prepared motor rotor with modified bore
  3. Motor shaft assembly (shaft, pulley, codewheel)
  4. Prepared encoder with wiring and connector
  5. Center pulley assembly
  6. Output pulley assembly

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Additional Components

  • 1x Timing belt AT3 150mm length, 4mm width
  • 1x Timing belt AT3 201mm length, 6mm width
  • 4x M3x5 flat head screws (motor mounting)
  • 2x M3x16 flat head screws (encoder mounting)
  • 5x M2.5x6 socket head cap screws (shell connection)
  • 3x M2.5x8 socket head cap screws (shell connection)
  • 2x Timing belt tensioner roller assemblies
  • 1x Brass washer (from motor disassembly)

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Required Tools

  • 2mm hex driver
  • 1.5mm hex driver
  • Small flat head screwdriver
  • Pointed tool (optional, for shell closing)
Take Your Time Actuator assembly requires patience and careful attention to alignment. Rushing can result in:
  • Crossed timing belt teeth (belt will skip)
  • Misaligned bearings (causing binding)
  • Damaged codewheel (encoder failure)
Allow 60-90 minutes for your first assembly.

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Mounting the Stator

1

Route motor phase wires

Route the motor phase wires through the opening in the shell base. The wires should exit cleanly without pinching.
2

Position stator

Place the stator on the mounting surface inside the shell base. Align the mounting holes.
3

Position motor wires

Bend the motor phase wires upward and align them with the wire routing cutout in the shell.
4

Install mounting screws

Using a 2mm hex driver, install the four M3x5 flat head screws to secure the stator. Ensure:
  • The stator is fully seated against the mounting surface
  • The stator does not move when you try to wiggle it
  • Screw heads are flush with or slightly below the stator mounting flange
5

Route wires to interface

Route the phase wires through the opening behind the encoder mount area and exit through the mounting interface.

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Installing the Motor Shaft and Rotor

1

Prepare motor shaft assembly

Get the motor shaft assembly (shaft with bonded pulley and codewheel). Handle the codewheel carefully - avoid bending or scratching it.
The codewheel is delicate. Even small scratches or deformations can cause encoder errors.
2

Install brass spacer

Ensure the brass washer (from motor disassembly) is in place on the stator bearing.
3

Insert motor shaft

Carefully insert the motor shaft assembly into the stator bearing from below. The shaft should slide smoothly through both stator bearings.
4

Prepare rotor set screws

Turn the assembly over. Using a 1.5mm hex driver, install the two M3 set screws into the rotor approximately halfway.
5

Align set screws with flats

Line up the set screws on the rotor with the flats on the motor shaft. This ensures the screws will properly lock onto the shaft.
6

Install rotor

Carefully slide the rotor onto the motor shaft and push it all the way down until it’s fully seated.
7

Tighten set screws

Using a 1.5mm hex driver, tighten both set screws while pushing down on the rotor to maintain seating.
Tighten the screws evenly - alternate between them rather than fully tightening one first.
8

Verify rotor installation

  • Manually spin the rotor - it should rotate freely without binding
  • Pull on the rotor in the axial direction - there should be no play or only minimal play (less than 0.1mm)

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Installing the Timing Belt Transmission

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First Stage (Motor to Center Pulley)

1

Install 150mm belt on center pulley

Place the 150mm timing belt (4mm width) around the center pulley. Ensure the belt teeth fully engage with the pulley teeth.
2

Install belt on motor pulley

While keeping the belt on the center pulley, place the other end around the motor pulley and engage the teeth.
3

Install center pulley

Keep the timing belt under slight tension. Insert the center pulley into its bearing in the shell base. The pulley should seat fully.

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Second Stage (Center Pulley to Output Pulley)

1

Install 201mm belt on output pulley

Place the 201mm timing belt (6mm width) around the output pulley. Ensure the flange side of the output pulley faces upward.
Orientation matters: If the output pulley flange faces downward, the actuator will not assemble correctly and the belt may come off during operation.
2

Install belt on center pulley

Place the other end of the 201mm belt around the center pulley and engage the teeth. Keep the belt under tension.
3

Install output pulley

While maintaining belt tension, insert the output pulley into its bearing in the shell base.
4

Verify transmission operation

Rotate the output shaft back and forth. The transmission should move smoothly:
  • No binding or tight spots
  • Belt teeth remain engaged
  • Both belts track centered on their pulleys

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Installing the Encoder

1

Route encoder wires

Route the encoder wires through the opening in the mounting interface.
2

Position encoder

Carefully insert the encoder at an angle so that the codewheel passes through the gap in the encoder body. Lower the encoder onto its mounting surface.
Shortening and bending the encoder pins (as described in encoder preparation) makes this step much easier.
3

Install mounting screws

Using a 2mm hex driver, install the two M3x16 flat head screws to secure the encoder. Do not overtighten.
4

Verify codewheel position

Check that:
  • The codewheel is centered in the encoder gap
  • The codewheel does not touch the encoder body
  • There is approximately 0.5-1mm clearance on all sides
If the codewheel touches the encoder, the actuator will not function. Check motor shaft installation and codewheel bonding alignment.

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Installing the Timing Belt Tensioner Rollers

1

Prepare shell cover

Get the shell cover and the two timing belt tensioner roller assemblies.
2

Verify washer installation

Confirm that the modified M2.5 washers are installed on each tensioner roller screw.
3

Install tensioner rollers

Using a 2mm hex driver, install both timing belt tensioner rollers into their mounting positions in the shell cover. Do not fully tighten yet.
4

Verify roller rotation

Rotate each tensioner roller to ensure they spin freely without binding.

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Closing the Shell

This is the most challenging part of the assembly and may require several attempts.
1

Position shell cover

Place the shell cover on the shell base at a slight angle. Partially insert the output pulley bearing into the cover bearing seat as shown in the reference images.
2

Apply pressure to center

Apply moderate, even pressure to the center of the assembly. Maintain this pressure throughout the following steps.
Use appropriate force: Too little pressure and the cover won’t close. Too much pressure can crack the 3D printed shell.
3

Clear first side of second stage belt

The 201mm timing belt must clear the tensioner rollers as the cover closes. Using a small flat head screwdriver, push the timing belt inward on one side while continuing to apply pressure to the cover.
You should feel the cover move downward slightly when the belt clears the first roller.
4

Turn assembly over

Keeping moderate pressure on the assembly, carefully turn it over to access the other side.
5

Clear second side of belt

Using the screwdriver, push the timing belt inward on the opposite side. The cover should move down further as the belt clears the second roller.
6

Seat center pulley bearing

The center pulley now needs to engage with the bearing in the cover. While gently pushing down on the cover:
  • Grab the rotor (you can turn it from outside the shell)
  • Rotate the rotor back and forth several times
  • The center pulley should find the bearing and engage
This usually takes 3-5 full rotations in each direction. Be patient and maintain gentle downward pressure.
7

Alternative method for center pulley

If the center pulley doesn’t engage after several rotations:
  1. Insert a pointed tool through the hole in the center pulley (from the motor side)
  2. Use the tool to push the center pulley toward the motor while rotating the rotor
  3. This helps guide the pulley into the bearing
8

Verify shell is fully closed

The shell halves should be completely flush around the entire perimeter. If there are gaps:
  • Check that timing belts have cleared the tensioner rollers
  • Verify center pulley has engaged its bearing
  • Check for any obstructions (wires, etc.)
9

Verify motor rotates

Before installing fasteners, verify that you can manually rotate the motor rotor smoothly. If there’s binding, open the shell and check for:
  • Timing belt teeth not fully engaged
  • Bearings not fully seated
  • Codewheel touching encoder

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Installing Shell Fasteners

1

Identify screw locations

The shell requires 8 screws total:
  • 5x M2.5x6 socket head cap screws
  • 3x M2.5x8 socket head cap screws
Refer to the fastener diagram for specific locations.
2

Install all fasteners

Using a 2mm hex driver, install all eight connecting screws. Start each screw by hand to ensure proper thread engagement.
3

Tighten in star pattern

Tighten the screws in a star pattern (opposing screws) with moderate torque. This ensures even clamping force and prevents shell distortion.
Do not overtighten. The threads are in 3D printed plastic and can strip. Tighten until snug plus approximately 1/4 turn.

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Final Wiring

If you haven’t already installed connectors on the motor phase wires and encoder wires, do so now:
1

Solder motor phase connectors

Follow the instructions in Motor Preparation - Soldering the Motor Phase Connectors.
2

Crimp encoder connector

Follow the instructions in Encoder Preparation - Crimping Hirose Connector.

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Quality Check

Before proceeding to testing, verify:

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Mechanical

  • Motor rotor rotates smoothly by hand
  • Output shaft rotates smoothly
  • No unusual noise or grinding
  • Shell is fully closed with no gaps
  • All fasteners are secure
  • Timing belts are properly tensioned and tracking centered

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Electrical

  • Motor phase connectors are properly soldered and insulated
  • Encoder connector is properly crimped
  • No exposed wire conductors
  • Wires are routed cleanly without pinching

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Codewheel/Encoder

  • Codewheel does not touch encoder body
  • Codewheel rotates without wobbling
  • Encoder is securely mounted

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Assembly Complete

The actuator module is now fully assembled and ready for testing. The next step is to test the module and determine the correct motor phase sequence. Weight: Fully assembled actuator module with 30cm wires: approximately 160g

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Troubleshooting

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Shell Won’t Close

  • Timing belt not clearing tensioners: Push belt inward more firmly
  • Center pulley not engaging: Rotate rotor more, or use pointed tool to guide pulley
  • Output pulley misaligned: Disassemble and check pulley orientation

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Motor Binding

  • Rotor rubbing: Check rotor set screws, verify proper bore sizing
  • Bearings misaligned: Disassemble and check bearing seats
  • Codewheel hitting encoder: Check codewheel bonding alignment and encoder mounting

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Belt Issues

  • Belt teeth not engaged: Disassemble and carefully re-install belt
  • Belt too loose: Use larger diameter tensioner rollers
  • Belt tracking off-center: Check pulley alignment

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