Hardware — Specifications, BOM & Assembly

1. General Specifications

OpenArm features a small human-like physique with support pillars made of MiSUMi aluminum frames for easy dimension adjustment and attachment of cameras and sensors. The base plate features evenly spaced M6 taps for mounting to surfaces.

Each joint includes mechanical limits restricting motion range for safety purposes. These limits also protect internal wiring from over-rotation damage.

2. Motor Specifications

OpenArm incorporates the DAMIAO 43 series and DAMIAO 8009P motors, with different models selected for each joint to balance high payload capacity with a clean, compact appearance. Motors with cross-roller bearings are used in single-support sections for enhanced rigidity and precision.

Motor Assignment by Joint

Detailed Motor Specifications

3. Gripper Specifications

Custom End-Effector Integration

OpenArm supports custom end-effectors by replacing the J8_B interface part. When designing a custom attachment:

• Match original hole patterns and dimensions of J8_B
• Include mounting features compatible with your end-effector
• Maintain structural integrity and alignment
• Consider balanced mass distribution relative to the arm's axis
• Plan cable routing to avoid snags during full range of motion
• Design for 3D printing or CNC machining manufacturability

CAD files for the J8_B interface are available in the openarm_hardware repository.

4. Bill of Materials

All prices listed below are in Japanese Yen (¥), as the primary sourcing platform is MISUMI Japan. International buyers should check for regional MISUMI sites or alternative distributors.

Actuators (Total: ¥397,356)

Mechanical Components (Total: ¥478,518)

Electrical Components (Total: ¥84,564)

Electrical components include: 24 V / 15 A power supply, USB to CANFD converter, and emergency stop switch. PCBs and wiring harnesses are custom-designed with fabrication files provided in the repository.

Procuring Components

Off-the-Shelf Parts (MISUMI)

Most mechanical and fastener components are available as catalog items from MISUMI.

1. Visit the MISUMI website. Go to misumi.com and select your region.
2. Search by model number. Enter the part number (e.g., CBE4-8) in the search bar.
3. Confirm dimensions/specs. Verify the part matches the BOM specifications.
4. Add to cart and order. No drawings needed for catalog parts — model numbers are sufficient.

Manufactured Parts (MEVIY)

Some components require custom manufacturing via MEVIY, MISUMI's automated 3D machining service. Two ordering methods:

Method 1: Upload CAD File

1. Go to MEVIY. Visit the MEVIY website and create an account.
2. Upload STEP file. Download the STEP file from openarm_hardware and upload it.
3. Select material, finish, tolerances. Review the automated quote.
4. Place order. Confirm specifications and submit.

Method 2: Use Pre-registered Model Numbers (Recommended)

1. Visit MISUMI's search page.
2. Paste the BOM model number. Example: MVBLK-ASN-48S-4BGUX-L. MEVIY automatically identifies it as a custom part.
3. Specify quantity and order. No CAD upload required — the geometry is pre-validated.

Custom PCBs (JLCPCB)

1. Download files. Get the Gerber + BOM + CPL files from the project repository.
2. Upload to JLCPCB. Go to jlcpcb.com and upload the Gerber zip file to get a quote.
3. Configure options. Leave default settings unless you have specific requirements. Optionally choose Remove Mark in the Mark on PCB option.
4. Enable PCB Assembly. Scroll to the PCB Assembly tab and enable it, then click Next.
5. Upload BOM and CPL files. Click Process BOM & CPL and review the parts list.
6. Review 2D/3D models and proceed to place the order.

Custom Wires and Harnesses (LCSC)

1. Go to LCSC custom cable page.
2. Upload wiring drawings. Use drawings provided in the openarm_hardware repository.
3. Input desired quantity and click Confirm your cable plan.
4. Submit cable order. LCSC will send a quote for final ordering.

5. Assembly Guide

Step 0: Find CAD Files

The project makes all 3D models publicly available through GitHub to promote openness and customization.

What's included in the repository:

• STEP Files — For manufacturing and modification in any CAD tool
• STL Files — Ready for 3D printing of all printed components
• Attachments — Camera mounts, PCB hubs, and custom pieces
• Wiring Diagrams — For cable manufacturing reference

Repository: github.com/enactic/openarm_hardware

Motor ID Configuration

Before assembling, each DAMIAO motor must be assigned the correct CAN ID using the Damiao Debugging Tools software (Windows). Configuration is done over UART (serial), not CAN.

Motor ID Reference Table

Motor ID Configuration Steps

1. Download Damiao Debugging Tools. The Windows executable is available from Damiao. Allow through Windows Defender if blocked.
2. Connect via UART serial at 921600 bps. Use a USB-serial adapter — not a CAN adapter for this step.
3. Click "ReadParam" to retrieve current motor parameters and verify connection.
4. Select correct Sender and Master IDs from the reference table above.
5. Input values into the corresponding fields in the software.
6. Click "WriteParam" to save settings permanently to the motor.

Power Supply Requirements for Motor Configuration

6. Wiring & Casing

Cable Types

Five cable types are needed for the full bimanual assembly:

Casing Components

The casing requires CSPPNSB-STU-TP3-8 screws (quantity: 30) and consists of five distinct casing pieces with left/right distinction for certain components.

Hub Board Components

Required for hub board assembly:

• Cap screws
• T-slot nuts
• Custom PCBs (fabricated via JLCPCB)
• Chest covers