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Overview

Back in 2014, this project began as a reverse engineering effort of a miniature palletizing robot arm, eventually evolving into the open-source Lite Arm i2 — an affordable, DIY robotic arm you can 3D print yourself.

Assembled Dimensions

Height: ~12 inches (highest position)
Total Length: 19.5 inches (arm fully outstretched)
Arm Length: 13.25 inches (fully outstretched)
Width: 6.5 inches with MG995 servos
Base: 4" x 4"

⚠️ Do not over-tighten parts — this may cause damage and prevent proper operation.

Build Steps

1Gather All 3D Printed Parts & Hardware

Verify you have all 39 3D printed parts from the Lite Arm i2 parts manifest. Servos needed: • 3x Tower Pro MG995 or MG996 (base rotation x1, arm movement x2) • 1x Tower Pro SG92R (optional, fits in head) Hardware needed: • #6M machine screws with nuts and lock nuts (various lengths) • #6M flat washers • 3x 1.5" deck or drywall screws • 6–7" #6M threaded rod ⚠️ 4 of the base servo's small spacers may require sanding depending on servo used.

💡 Tip: Lay all parts out and check against the parts manifest before starting — missing a part mid-assembly is frustrating!

⚠️ Warning: Do NOT over-tighten any parts during assembly. This may cause damage to the uArm and prevent proper operation.

2Assembly Step 1 – Base Nuts & Ring

Press the #6 nuts into the grooves on the base using a pair of pliers. This keeps them from free-spinning when assembling the sides later. Attach the ring to the base as shown.

💡 Tip: Press nuts in firmly so they are flush and locked in place — they shouldn't rotate when you tighten screws into them.

3Assembly Step 2 – Base Servo Installation

Insert spacers into the uArm base. Spacers may need to be sanded for fit depending on the servo used. Install the MG995 or compatible servo on top of the spacers and secure with 1/2" #6 machine screws.

💡 Tip: Sand spacers gradually — test the fit after each pass to avoid removing too much material.

⚠️ Warning: Do not over-tighten the servo mounting screws.

4Assembly Step 3 – Base Stand

Assemble the base stand with the spacer and servo horn mount using 3x 1" #6 machine screws. Attach the servo horn with screws through the servo horn mount.

💡 Tip: Ensure the servo horn is centered before tightening — this affects the arm's range of motion.

5Assembly Step 4 – Attach Base to Stand

Attach the uArm base to the base stand from the previous step using the servo horn machine screw as shown.

💡 Tip: The base should rotate freely around the servo horn screw — don't over-tighten.

6Assembly Step 5 – Small Shoulder Servo

Use the smaller shoulder in this assembly. Attach the MG995 or compatible servo through the small shoulder with the servo body facing outwards, using 4x 1/2" #6 machine screws.

💡 Tip: Double-check which shoulder is the 'small' one before attaching — they look similar but are different sizes.

7Assembly Step 6 – Linkage Connector

Attach one of the printed linkage connectors to the servo horn using screws. Next, attach the linkage connector assembly to the servo using the servo's machine screw.

💡 Tip: Make sure the linkage connector is aligned straight on the servo horn before tightening.

8Assembly Step 7 – Large Shoulder Servo

Use the larger shoulder for this portion. Attach the MG995 or compatible servo through the large shoulder with the servo body facing outwards, using 4x 1/2" #6 machine screws.

💡 Tip: Keep the servo wires accessible for routing later — don't trap them inside the assembly.

9Assembly Step 8 – Lower Arm

Assemble the lower arm using the parts shown, along with: • 4x 2" #6 machine screws • 2x 1/2" wood screws Do not fully tighten the 2x 2" #6 machine screws in the arm that hold the round cross supports — this makes the following steps easier.

💡 Tip: Leave those cross support screws loose for now — you'll tighten everything once the full arm is assembled.

10Assembly Step 9 – Upper Arm

Assemble the upper arm using the parts shown, along with: • 5x 2" #6 machine screws • 1x 3" #6 machine screw Use the two longer screws to attach the linkage to the head.

💡 Tip: The 3" screw goes at the head linkage pivot — make sure it's in the right place before tightening.

11Assembly Step 10 – Kinematic Linkage

Assemble the two kinematic linkage parts with 1/2" #6 machine screws as shown.

💡 Tip: The linkage should pivot freely — if it binds, loosen the screws slightly.

12Assembly Step 11 – Join Upper & Lower Arm

Attach the upper and lower arm assemblies: • The shorter linkage part attaches to the back of the upper arm • Use 1x 3" #6 machine screw at the pivot point of upper and lower arm • Use 1x 2" #6 machine screw for the linkage

💡 Tip: Check that both arms move through their full range without binding before continuing.

13Assembly Step 12 – Large Shoulder to Arm

Attach the large shoulder assembly to the arm assembly using the servo machine screw. Attach the arm's linkage rod to the large shoulder as shown.

💡 Tip: The linkage rod connection is critical for proper arm movement — make sure it's secure.

14Assembly Step 13 – Attach Arm to Base

Attach the large shoulder / arm assembly to the base assembly. The large shoulder assembly attaches via 2x 1.5" #6 machine screws threaded through the 2 nuts in the side of the base assembly.

💡 Tip: These screws go into the nuts you pressed in during Step 1 — this is why that step matters!

15Assembly Step 14 – Small Shoulder Assembly

Attach the small shoulder assembly to the arm and base: • Attach via 2x 1.5" #6 machine screws through the 2 nuts in the side of the base • Attach upper arm linkage to the small shoulder linkage horn with a small spacer between linkage and horn • Use 1x 2" #6 machine screw with a large spacer on the outside as a stop, secured with a nylon lock nut

💡 Tip: The nylon lock nut should be snug but still allow the joint to pivot freely.

16Assembly Step 15 – Tie Shoulders with Threaded Rod

A length of threaded rod is used to tie the two shoulders together and tighten the entire arm chassis. Tighten the rod to pull the gaps out of the parts between the two servo horns.

💡 Tip: Tighten gradually and check movement after each turn — the arm should feel solid but servos should still move freely.

⚠️ Warning: ⚠️ Do NOT over-tighten this bolt — servo damage will occur!

17Assembly Step 16 – Arduino Mounting Platform

Assemble the Arduino mounting platform: • Both supports attach to corresponding holes in each shoulder • The platform mounts on top of the supports • Screw holes with risers are built into the platform for the Arduino This platform was designed for an Arduino UNO, but an Arduino Duemilanove will also fit.

💡 Tip: Route your servo wires neatly before mounting the Arduino so they don't get pinched.

18Complete & Test

Your UArm Miniature Palletizing Robot Arm is now fully assembled! Connect servos to the Arduino and upload test code to verify each joint moves correctly. Test the full range of motion for each axis before running any automated routines.

💡 Tip: Test one servo at a time before running all together — this makes it easier to diagnose any wiring issues.

⚠️ Warning: Always power down before adjusting any wiring connections.

UArm Miniature Palletizing Robot Arm for Arduino

What you'll learn

Overview

Assembled Dimensions

Materials

Build Steps

Reflection Questions