Week 12

Machine Design

The Minimalist CNC

A compact desktop CNC machine combining mechanical design,
electronics, software control, and digital fabrication

Individual Contributions

Andres Mamani — CAD & Electronics Lead

I contributed to the 3D modeling of the CNC machine in Autodesk Inventor and prepared all technical drawings. I supported the assembly process and contributed to the development of the control code using GRBL firmware. I also guided key decisions based on experience with the tools, materials, and machines used in the fabrication lab. My focus was on translating the design concept into precise digital models and ensuring electronic control systems worked seamlessly with the mechanical structure.

Micaela Cordova — Manufacturing & Documentation Lead

I contributed to the design of the parts and continuously adapted the models based on real component measurements. I supported the entire manufacturing and assembly process, especially in the fabrication of metal components and laser-cut acrylic parts. I performed extensive physical testing, ensured proper fitting of all components, and debugged assembly issues. I also prepared all presentation materials. My focus was on bridging the gap between digital design and physical reality.

Team photo

Project Timeline & Schedule

Week-long timeline from initial research through final testing and documentation.

Monday
Tuesday
Wednesday
Thursday
Friday
Research & Inspiration
Mon
Initial Sketch & Concept
Mon
CAD Modeling — Phase 1
Tue
CAD Modeling — Phase 2
Wed
DXF Export & CAM Prep
Wed
Metal Cutting (Kitamura)
Thu
Milling (LAGUN)
Thu
Laser Cutting (Acrylic)
Thu
Assembly & Alignment
Fri
Manual Testing
Fri
Digital Control Testing
Fri
Documentation
Fri

Color Legend: Research CAD Work Fabrication Assembly & Testing Documentation

Task Distribution

Andres Mamani

  • 3D Modeling in Inventor — Complete design of all CNC parts
  • Technical Drawings — 2D profiles and specs for fabrication
  • DXF Export — Laser cutting files for acrylic components
  • Assembly Coordination — Leading assembly and problem-solving
  • Control Code — GRBL firmware configuration and testing
  • Digital Testing — OpenBuilds CONTROL setup and calibration

Micaela Cordova

  • Design Adaptation — Adjusting models to real measurements
  • Metal Fabrication — CNC cutting, milling, and metalwork
  • Laser Cutting — Supervision of acrylic component fabrication
  • Component Assembly — Physical assembly and alignment
  • Testing & QC — Fit, alignment, and movement verification
  • Documentation — Photos, videos, slides, final docs

Project Idea & Inspiration

We decided to develop a minimalist CNC machine because it combines mechanical design, electronics, software control, and digital fabrication in one integrated system.

Our main inspiration came from small desktop CNC machines and from a YouTube playlist by Prof. Garcia (CNC Facil de hacer en Casa), which helped us understand the basic structure, movement system, assembly sequence, and workflow from design to G-code execution.

Inspiration References

Inspiration — small desktop CNC reference 1 Inspiration — small desktop CNC reference 2

Based on this research, we adapted the idea to the materials and components available in our lab — creating a compact 3-axis CNC machine using lead screws, linear bearings, stepper motors, an Arduino Uno with GRBL, and a CNC Shield with A4988 drivers.

The Design

Initial Sketch & Concept

Before modeling in Inventor, we started with a hand sketch to understand the general shape, position of the axes, and space required for each component. Below you can see the evolution from the hand sketch directly to the 3D digital model.

Hand sketch — initial CNC concept

Step 1 — Hand sketch with initial dimensions and layout

→
Inventor — full assembly isometric

Step 2 — Same structure translated into Autodesk Inventor 3D model

Individual Parts Modeling in Inventor

Each component was modeled separately: base, side supports, moving bed, motor supports, and plates for the X, Y, and Z axes.

Inventor — Y-axis bed frame base Inventor — bed with acrylic surface Inventor — full assembly side view Inventor — full assembly isometric

Complete Assembly Visualization

All parts were placed into an Inventor assembly file to visualize the complete CNC structure — identifying the position of motors, lead screws, shafts, couplings, bearings, acrylic plates, and aluminum profiles.

CAD Assembly — complete structure isometric CAD Assembly — front elevation CAD Assembly — XZ carriage detail

CAD vs. Physical Machine

After fabrication and assembly, the physical machine closely matched the digital design. The comparison below shows how the virtual model translated into the real built machine.

CAD model — digital design in Inventor

Digital Model — Autodesk Inventor

→
Physical machine — real built CNC

Physical Machine — Final Built Result

DXF Export for Laser Cutting

From the 3D model, we exported the flat faces of structural pieces as DXF files, which were then used to laser cut the acrylic components on the C4V Laser machine.

C4V Laser cutting machine Laser cutting parameters — speed 10mm/s, power 30% Precision-cut acrylic components result

Mechanical Fabrication Process

After completing the 3D model, we started mechanical fabrication: measurement, CAD verification, CAM preparation, CNC metal cutting, milling, laser cutting, and 3D printing.

Measurement & Marking of Aluminum Profiles

We measured and marked the aluminum profiles to match the Inventor model dimensions precisely.

Team measuring and marking aluminum profiles in the workshop

CAD Verification in Inventor

Before machining, we reviewed the part geometry in Inventor to verify shapes, dimensions, and hole positions.

Autodesk Inventor — reviewing part geometry before machining

CAM Preparation — EdgeCAM

We used EdgeCAM to prepare cutting paths, verify toolpaths, and generate G-code for the CNC metal-cutting machine.

EdgeCAM software — L-shaped part toolpath preparation G-code file loaded — drilling and milling operations listed CAM software — 3D drill preview toolpath simulation

CNC Metal Cutting — Kitamura Mycenter-3XG

The CNC Kitamura Mycenter-3XG machining center reads the G-code from EdgeCAM and mills metal parts with high precision.

CNC cutting machine — large aluminum sheets on table CNC Kitamura Mycenter-3XG control panel — operator setting up Cut metal parts — precision L-shaped aluminum brackets result

Milling — LAGUN Machine

The LAGUN milling machine was used to drill precision holes for motor mounting, shaft supports, and fasteners.

LAGUN milling machine — precision drilling for mounting holes Motor alignment test — NEMA motor on drilled metal plate

Metal Cutting with Router / Saw

Structural aluminum beams were cut to exact lengths using a precision metal saw.

Precision metal saw cutting aluminum profile to exact length

Machines Used in Fabrication

Five different machines available in Fablab Ulima, each serving a specific purpose in the manufacturing workflow.

CNC Kitamura Mycenter-3XG

CNC Kitamura Mycenter-3XG

Metal milling and cutting of structural aluminum plates

C4V Laser Cutter

C4V Laser Cutter

Cutting acrylic structural plates from DXF files

Bambu Lab X1-Carbon AMS

Bambu Lab X1-Carbon AMS

3D printing of motor mounts and support parts

Precision Metal Saw

Precision Metal Saw

Cutting aluminum profiles and beams to exact lengths

3D Printing — Bambu Lab X1-Carbon AMS

Support components and motor mounts were fabricated on the Bambu Lab X1-Carbon AMS printer, allowing rapid iteration before committing to permanent metal solutions.

Bambu Lab X1-Carbon AMS 3D printer 3D-printed motor support parts — ready for assembly

From Virtual to Physical: Solving Real-World Problems

Digital design and physical reality don't always align perfectly. Here we document the specific problems encountered and how we solved each one.

Problem 1 — Motor Mounting Dimension Errors

THE PROBLEM

Our Inventor model specified certain distances between mounting holes for the NEMA stepper motors. When the actual motors arrived, the holes in our fabricated metal plates did not align — the original design showed incorrect hole spacing (Ancho 23.30 mm, Largo 17.72 mm).

THE SOLUTION

We redesigned the motor mounting plates with corrected dimensions (43.5 mm and 22 mm spacing), re-cutting in transparent acrylic instead of the originally planned metal.

BEFORE — original design with incorrect hole spacing

BEFORE — Incorrect dimensions in CAD

→
AFTER — corrected dimensions matching real motor holes

AFTER — Corrected dimensions matching real motor

Problem 2 — Coupling and Lead Screw Alignment

THE PROBLEM

The flexible couplings connecting stepper motors to lead screws required precise spacing. Our initial design did not account for the exact thickness of the couplings, resulting in misalignment.

THE SOLUTION

We manually drilled and adjusted holes in mounting plates. Acrylic proved more flexible for iterative corrections than metal. We tested alignment repeatedly until the couplings rotated concentrically with the lead screws.

Adjusted acrylic components — hands-on alignment validation
Problem 3 — Bearing Support Positioning

THE PROBLEM

The linear ball bearings required exact positioning. After assembly, some bearings were slightly misaligned, causing binding when moving the axes manually.

THE SOLUTION

We used shims and spacers to adjust bearing positions and manually opened existing holes where needed. All corrections were fed back into the digital model.

Key Lessons from the Virtual-to-Physical Transition

  • Always Measure Real Components First — Don't assume catalog dimensions are exact.
  • Prototype and Test Early — Test with actual components before mass-fabricating.
  • Choose Flexible Materials — Acrylic proved superior to metal for rapid iteration.
  • Document All Corrections — Records make the next iteration more accurate.
  • Tolerances Accumulate — +/- 0.5 mm across multiple parts causes assembly problems.

Original Plan vs. Reality

Key differences between what we originally designed and what we had to change once working with physical components.

Component Original Plan What We Changed Reason
Motor mounting platesMetal, 23.3 mm x 17.72 mmAcrylic, 43.5 mm x 22 mmReal motor dimensions differed from CAD
Mounting materialSteel / aluminum plateTransparent acrylicEasier to re-drill and adjust during iteration
Coupling alignmentDirect CAD measurementManual adjustment with shimsPhysical coupling thickness not accounted for
Bearing positionsEstimated from InventorAdjusted with spacers on-siteSlight misalignment caused binding on axes
Y-axis supportMetal component3D-printed partFaster to fabricate and test first
Power supply voltage12V battery24V for wood engraving12V insufficient torque for milling bit on wood

Results of Our Corrections

Smooth Axis MovementAll three axes moved without binding
Proper Motor MountingMotors firmly secured with correct alignment
Accurate Lead Screw MotionConcentric rotation with motor shafts
Improved PrecisionMachine ready for digital control testing

Mechanism

Mechanism diagram — X/Z carriage, Y-axis bed, manual and digital control workflow

The CNC machine combines three coordinated motions: the X/Z tool carriage, the Y-axis moving bed, and a control workflow tested manually then digitally.

1. The X and Z Carriage

The central carriage holds the tool. The X-axis moves it left to right; the Z-axis moves the tool up and down to approach or separate from the work surface.

2. The Y-Axis Bed

The lower bed moves the material forward and backward. We manually tested this axis by rotating the rods through the couplings to verify smooth movement before powering the system.

3. Digital Control Testing — OpenBuilds CONTROL

After manual verification, the machine was controlled via OpenBuilds CONTROL. From the laptop we jogged the axes, moved the bed, and established the work origin before running a G-code job.

Main Components & Inventory

Complete inventory — lead screws, shafts, linear bearings, couplings

Mechanical Components

ComponentDescription
Flexible shaft couplings x3 (8 mm)Connect stepper motor shafts to lead screws.
Lead screws x3 (8 mm, ~40 cm)Convert rotational motion into linear X/Y/Z movement.
Lead screw nuts x3Travel along screws, transferring motion to moving parts.
Linear ball bearings x12 (8 mm)Smooth guided linear movement along steel shafts.
Hardened steel shafts x5 (8 mm, ~40 cm)Guide the movement of carriage and bed.
Shaft supports x2 (8 mm)Hold and align guide shafts for structural stability.
Standard bearings x3 (8 mm)Support rotating parts and reduce friction.
Laser-cut acrylic platesMachine bed, structural supports, and mounting surfaces.
Aluminum profiles (V-slot)Main structural frame of the CNC machine.
3D-printed support partsSpecific holders and mechanical adaptations.
Tool holder / spindle holderHolds the engraving, drawing, or cutting tool.
Fasteners (M3 screws, nuts, spacers)Assemble and secure all mechanical parts.

Electronic Components

ComponentDescription
Arduino Uno + GRBL firmwareMain controller — interprets G-code commands.
CNC ShieldDistributes STEP/DIR signals to each motor driver.
A4988 stepper motor drivers x3Control current and movement of each stepper motor.
Stepper motors x3 (NEMA)Generate movement for X, Y, and Z axes.
24V power supply (main system)Powers CNC Shield, A4988 drivers, and stepper motors.
12V power supply (spindle)Powers the spindle / engraving motor only.
USB cableConnects laptop to Arduino Uno — transmits G-code.
Spindle / engraving motorRotary tool for cutting or engraving.
Wires and connectorsConnect all motors, drivers, shield, and power supplies.

Software

ToolPurpose
Autodesk Inventor3D modeling and mechanical design of all CNC parts.
EdgeCAM / LibellulaCAM — metal cutting toolpath generation and G-code export.
AspireVector design, machining toolpaths, and G-code export.
GRBL firmwareInstalled on Arduino Uno — converts G-code to motion commands.
OpenBuilds CONTROLMachine control: jogs axes, sets origin, runs G-code.
Bambu StudioSlicing software for 3D-printed support parts.
InkscapeVector editing for 2D design files.
Arduino IDEUsed to flash GRBL firmware onto the Arduino Uno.

Electrical System

The electrical system connects the software control layer to the physical stepper motors through a chain of signal and power components.

The Minimalist CNC — full system diagram

System Connection Diagram

The diagram below shows exactly how each electronic component is connected — from the laptop sending G-code, through the Arduino and CNC Shield, to each individual stepper motor and the separate spindle power circuit.

Electrical system diagram — laptop, Arduino GRBL, CNC Shield, A4988 drivers, stepper motors, power supplies

Signal & Power Flow

Control & Data Path

LaptopOpenBuilds CONTROL
──USB──▶
Arduino UnoGRBL firmware
──▶
CNC ShieldSignal distributor
──STEP/DIR──▶
A4988 DriversX, Y, Z
──▶
Stepper MotorsX, Y, Z axes

Power Rails

+24V (main) — Powers CNC Shield, A4988 Drivers & Stepper Motors
+12V (spindle) — Powers Spindle / Engraving Motor only
GND — Common ground across the entire system

How It Works — Step by Step

1

G-code: Laptop to Arduino via USB

OpenBuilds CONTROL sends G-code to the Arduino Uno running GRBL firmware, which interprets it and converts it into motion-control instructions.

2

Arduino to CNC Shield (STEP & DIR signals)

The Arduino sends 5V logic signals (STEP, DIR) to the CNC Shield — not directly to motors. These signals indicate when and which direction each motor should move.

3

CNC Shield to A4988 Motor Drivers

The CNC Shield distributes STEP and DIR signals to the corresponding A4988 driver for each axis (X, Y, Z).

4

A4988 Drivers + 24V Power to Stepper Motors

The A4988 drivers use the 5V logic signals to switch the external 24V power supply, regulating the current delivered to each stepper motor for precise step-by-step movement.

5

Spindle Motor — Separate 12V Circuit

The spindle is powered by a separate 12V supply, keeping the high-current spindle circuit isolated from the stepper motor logic to reduce electrical noise.

Wiring Summary

FromToSignal / Power
Laptop (USB)Arduino UnoG-code data (serial, 5V logic)
Arduino UnoCNC ShieldSTEP + DIR per axis (5V logic)
CNC ShieldA4988 Driver X/Y/ZSTEP-X/Y/Z, DIR-X/Y/Z
24V Power SupplyCNC Shield (V-motor)+24V, GND
A4988 Driver X/Y/ZStepper Motor X/Y/ZCoil pairs (A1,A2,B1,B2)
12V Power SupplySpindle Motor+12V, GND (isolated circuit)

CNC Workflow

A digital workflow connecting design, G-code generation, machine control software, electronics, and physical movement — showing how a digital design becomes a physical result.

CNC Workflow diagram — Design in Aspire, .ngc file, OpenBuilds CONTROL, Arduino GRBL, CNC Shield A4988, CNC Machine
1

Design in Aspire

We created the vector design (text "UP"), set machining toolpaths, and exported the project as a G-code .ngc file.

2

Load G-code in OpenBuilds CONTROL

The .ngc file was opened in OpenBuilds CONTROL to connect the laptop, load the file, jog axes, and set the work origin (X0, Y0, Z0).

3

G-code Transmission via USB

OpenBuilds CONTROL sends G-code to the Arduino Uno through USB. GRBL firmware interprets it and converts to motion commands.

4

Signal Processing — STEP & DIR

Arduino sends 5V STEP and DIR signals through the CNC Shield to the A4988 drivers for each axis.

5

Motor Driver + 24V Power

A4988 drivers use the 5V logic signals to switch 24V external power, delivering precise current to each stepper motor.

6

Physical Execution

The CNC machine executes the programmed movements — engraving, drawing, or drilling the material as defined in the G-code.

Operate It Manually

Before integrating stepper motors, we manually rotated the lead screws through the flexible couplings to verify that all mechanical components aligned properly and axes moved smoothly without binding.

Manual testing confirmed the mechanical design was sound and the machine was ready for electronic integration.

Results

Result: Drilling Holes & Drawing Lines

The CNC machine successfully drilled multiple holes and drew precise lines, demonstrating that the basic mechanical movement and control system were functioning correctly.

Early assembled CNC machine — first build stage Final CNC machine assembled — front view with spindle mounted

Key Achievements

Smooth Mechanical MovementAll three axes moved without binding
Precise Tool PositioningAccurate 3D tool positioning
Consistent OperationStable, reproducible results
Versatile ApplicationsDrilling, drawing, and engraving
Electronic IntegrationGRBL and Arduino worked seamlessly

Future Improvements

Future improvements diagram

Interchangeable Tool Heads

Customizable heads for painting, cutting, and engraving — making the machine more versatile for different operations.

Better Workpiece Fixing

A clamping system inside the acrylic box to hold material securely, reducing movement and misalignment during operation.

Stronger Y-Axis Support

Replace the 3D-printed Y-axis support with a metal component for improved rigidity and straighter motion.

Automatic Origin Detection

Distance sensors or a camera to detect the material surface automatically and calculate the work origin.

Presentation

The Minimalist CNC — project poster Fab Academy 2026
Download Poster (JPG)

Project Presentation Video

Complete project summary — design process, fabrication methods, assembly, and final testing results.

Download Resources

Pieces & Models

Download Pieces (ZIP)

Inventor Final Assembly

Download Assembly (IAM)

© Fablab Ulima 2026 | Design: Tooplate