SCARA diploma project / completed 2026
A low-cost educational robot built across every layer: bearings and printed links at the bottom, motion firmware in the middle, and an industrial communication contract with a Siemens PLC at the top.
Project brief
Industrial training robots are capable and reliable, and almost always out of reach for a student. This project asks whether the same architectural ideas can be learned on a machine that is affordable, open and repairable.
The answer is a three-axis SCARA manipulator with a motorized gripper. The PLC owns process intent; the ESP32 owns kinematics and motion. Modbus TCP is the explicit contract between them. The machine can also operate independently through its embedded web interface.
The goal was never to imitate industrial certification. It was to leave the whole chain exposed, from bearing preload to PLC register, so every decision can be inspected and argued with.
Design evolution
UMX v0.1 proved the educational idea. The diploma became a complete redesign: different structure, transmissions, Z-axis, gripper, electronics and control architecture.
Generation 01 · UMX concept
Planetary and belt drives, a rack-and-pinion Z-axis and Wi-Fi control established the concept. They also exposed the structural play, the serviceability problems and the motion-control ceiling that the redesign had to fix.
Generation 02 · Diploma
New geometry drawn in Fusion 360, steel bearing arrangements, an ACME Z-axis, four stepper drives, ESP32 firmware, a web UI and a Siemens-oriented Modbus TCP architecture.
Control architecture
The system is deliberately split at the point where industrial sequencing and real-time motion have different needs.
Control architecture / diploma diagram Commissioning boundary
Bidirectional Modbus TCP register exchange between the Siemens PLC and ESP32 was tested successfully. The robot’s complete physical pick-and-place cycle was demonstrated under ESP32 control. The final PLC-supervised cycle was not end-to-end commissioned before the defence.
System build
A ground-up redesign in Fusion 360 using printable, replaceable structural parts, heat-set inserts, steel bearings and geared stepper drives, with load cases on the critical parts checked in SolidWorks. The links measure 150 mm and 120 mm, giving a calculated 270 mm outer reach.
An ESP32-S3 executes forward and inverse kinematics, coordinated step generation, homing, software limits and TMC2209 driver configuration. It can run the complete pick-and-place cycle independently.
A Siemens S7-1200 acts as the intended supervisory layer. Bidirectional register changes over Modbus TCP were verified; the final end-to-end PLC-controlled cycle was not commissioned before the defence.
Project validation
Results are separated into observed behavior, demonstrated load and calculated design targets. No analytical value is presented as laboratory certification.
Observed · 25 cycles
≈ 1–2 mmCaliper-based endpoint-return test with an approximately 100 g payload. Useful as a preliminary engineering check, but not a metrology-grade repeatability measurement.
Demonstrated in lab
≈ 230 gThe highest conveniently available laboratory load was lifted without difficulty. XY deviation was not measured at this maximum tested load.
Design analysis
≈ 500 gDerived from Z-axis force analysis with an engineering safety factor. This remains a design value until a controlled payload test is completed.
Failure → diagnosis → fix
One early test produced a roughly 12 mm outlier after a gear slip. The current and control behavior were corrected in firmware, then the robot completed another multi-cycle run without the fault recurring. Mechanical backlash remains the next accuracy constraint.
Test campaign in progress
A structured run at 0 g, 100 g and 230 g is underway: maximum deviation and cycle time per load, over a fixed cycle count. The numbers land here when the campaign closes. Nothing is estimated in the meantime.
Engineering record
Planned improvements
The prototype proves the architecture. The next version should make position observable rather than assumed.
Project repository
The CAD, the ESP32 firmware and the S7-1200 program are being cleaned up for public release, so everything on this page can be reproduced rather than taken on trust. The repository below is the working one; the full diploma document stays private until the academic embargo lifts.