Robotics design
6-DOF robotic arm design for precise pick-and-place motion, case study.
A 6-DOF robotic arm program where joint packaging, link stiffness, and serviceability all had to stay credible at prototype scale. Yantrix delivered the full mechanical design — kinematic chain, joint stack, gearbox sizing, link FEA — in 14 weeks.
By Yantrix Engineering · Robotics Studio2 min readIndustrial automation
Overview
Why this study matters
Mechanical design of a 6-DOF compact robotic arm with cycloidal gearboxes hitting ±0.1 mm repeatability at 5 kg payload — from kinematic chain to manufactured prototype.
Client: An Indian automation startup building machine-tending robots
Project Type: Mechanical Design + Robotics
Industry: Industrial automation
Service Used: Robotic Arm Design + FEA + DFM
Results in numbers
What the engagement actually shipped.
- ±0.1 mm
- Repeatability at full reach
- 5 kg
- Payload at 920 mm reach
- ₹6.8 L
- BOM per arm (small batch)
- 14 wk
- Concept to manufactured prototype
Objectives
What the project needed to achieve
- Design a 6-DOF kinematic chain with 920 mm reach and 5 kg payload
- Hit ±0.1 mm repeatability at full reach under nominal payload
- Keep BOM under ₹7 lakh using Indian-vendor-friendly components
- Make the arm serviceable — every joint must be re-openable without arm-wide disassembly
Challenge
Engineering constraint
The system needed enough reach (920 mm) and payload (5 kg) for machine-tending tasks while keeping the arm rigid, compact, and realistic to fabricate at prototype scale. Off-the-shelf arms at this spec cost ₹12–18 lakh each; the client wanted a sub-₹7 lakh BOM with comparable repeatability.
Approach
How Yantrix approached the work
- 01Built the arm architecture around joint packaging first — sized the cycloidal gearbox, brushless servo motor, and absolute encoder stack per joint before iterating link geometry.
- 02Ran FEA on each link under worst-case dynamic loads (full reach + 5 kg + max acceleration) to verify stiffness; held tip deflection under 0.4 mm.
- 03Designed bracket structure and cable routing for assembly and serviceability — every joint cover removable with four M4 fasteners, cables in protected channels with service loops.
- 04Coordinated CNC and sheet-metal fabrication through Indian vendors with full GD&T production drawings and a DFM review pass per part.
Outcomes
What improved by the end
- ±0.1 mm repeatability at full reach under 5 kg payload
- 920 mm reach achieved with 18 kg arm mass
- BOM landed at ₹6.8 lakh per arm at small-batch quantity
- Joint package serviceable in under 12 minutes without arm-wide disassembly
Deliverables
What the client receives
- Full mechanical CAD (SolidWorks) with parametric tree for variant exploration
- Production drawings with GD&T for every machined and sheet-metal part
- Link-stiffness FEA report under worst-case dynamic load
- URDF + MoveIt configuration validated in Gazebo simulation
- BOM with Indian-vendor part numbers and lead times
- Assembly manual with torque specs and service procedure
Tools used
Stack and tooling
- SolidWorks (full parametric CAD)
- ANSYS Mechanical (link stiffness FEA)
- MoveIt 2 (URDF + kinematic validation in Gazebo)
- KiCad for the joint-controller PCB
- Indian-sourced cycloidal gearboxes (Newall, Sumitomo alternatives)
Impact
Business-level effect
- Client landed a production-ready arm at ~40% of off-the-shelf cost
- Indian-vendor component sourcing built supply-chain independence from imports
- Designed-for-service joint package reduced field-repair time by 5×
Conclusion
Custom robotic arms in India are viable when joint packaging is treated as the first design decision — not the last. The mechanical envelope determines what control and AI can possibly achieve downstream.
Next step
Building a robotic arm program in India and torn between off-the-shelf and custom? Send us your application requirements; we’ll model the buy-vs-build math.
Tagged
- Robotic Arm
- 6-DOF
- Cycloidal Gearbox
- FEA
- MoveIt
- DFM
Visual results
Key views and intermediate artefacts
Link stiffness FEA
Frequently asked questions
Answers from the engagement itself.
What repeatability is achievable on a custom robotic arm in India?
±0.1 mm is realistic at prototype scale with cycloidal or harmonic-drive gearboxes and properly-sized servo motors. ±0.05 mm starts to require harmonic drives, premium encoders, and rigid links — costs jump 50–80%.
Buy off-the-shelf or design custom?
Off-the-shelf wins under 5 units a year, or when the application matches a UR / Doosan / AUBO envelope. Custom wins above ~5 units and when the application has specific reach, payload, or environment constraints. Our buy-vs-build deck makes the math explicit per program.
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