3D Design Process
This section describes the standard mechanical design workflow used in ACLab for robotics, embedded systems, and electronic products. It covers the complete process from product requirements to manufacturing-ready files.
Workflow Overviewβ
| Step | Required | Description |
|---|---|---|
| Requirement Analysis | β | Define functional and mechanical requirements. |
| Concept Design | β | Create sketches, concept art, or rough layouts. |
| CAD Modeling | β | Build parametric 3D models of all components. |
| Assembly Verification | β | Verify fit, clearance, and assembly sequence. |
| Design for Manufacturing (DFM) | β | Optimize the design for the selected manufacturing process. |
| Simulation (FEA / Motion / Thermal) | Optional | Validate structural or thermal performance when necessary. |
| Prototype | Recommended | Produce and evaluate physical prototypes. |
| Production Release | β | Generate manufacturing files and documentation. |
Minimum workflow: Requirement β Concept β CAD β Assembly Verification β DFM β Manufacturing Files
Software Used in ACLab
| Software | Purpose | Status | Notes |
|---|---|---|---|
| Fusion 360 | CAD, Assembly, Drawing, CAM | β Primary | Standard CAD software used in ACLab |
| FreeCAD | Open-source CAD | Optional | Suitable for Linux users |
| SolidWorks | Mechanical CAD | Not Used | Commercial license required |
| Siemens NX | Enterprise CAD | Not Used | Powerful but intended for large-scale industrial projects |
| Onshape | Cloud CAD | Optional | Useful for online collaboration |
ACLab standardizes on Fusion 360 to simplify collaboration, file sharing, and training.
Design Inputs
Mechanical design usually starts from one or more of the following:
- Product specification
- Functional requirements
- PCB outline
- Electrical schematics
- Component datasheets
- Existing products
- Reference CAD models
- Concept art
- Hand sketches
- Customer requirements
- Industrial design requirements
Design Workflow
1. Requirement Analysisβ
Define:
- Product dimensions
- Functional requirements
- Mechanical constraints
- Manufacturing process
- Cost target
- Material selection
Input
- Product specification
- Customer requirements
Output
- Mechanical requirements
- Initial dimensions
- Design constraints
2. Concept Designβ
Develop the overall mechanical concept before creating CAD models.
Activities include:
- Hand sketches
- Concept art
- Block diagrams
- Internal component layout
Input
- Requirements
Output
- Concept sketch
- Layout proposal
3. CAD Modelingβ
Create parametric CAD models for every mechanical component.
Good practices:
- Fully constrain sketches
- Use parameters whenever possible
- Organize feature history
- Avoid duplicated dimensions
Input
- Concept design
Output
- Fusion 360 CAD files (.f3d)
4. Assembly Verificationβ
Assemble all parts and verify:
- Mechanical interference
- PCB clearance
- Cable routing
- Fastener accessibility
- Motion clearance
- Serviceability
Input
- Individual CAD parts
Output
- Complete assembly model
5. Design for Manufacturing (DFM)β
Optimize the design according to the manufacturing method.
Typical processes include:
- 3D Printing
- CNC Machining
- Injection Molding
- Sheet Metal Fabrication
Consider:
- Wall thickness
- Draft angles
- Tolerances
- Screw bosses
- Snap-fits
- Tool accessibility
Output
- Manufacturing-ready CAD model
6. Simulation (Optional)β
Simulation is performed only when required.
Examples:
- Static structural analysis (FEA)
- Thermal simulation
- Motion simulation
- Load analysis
Simulation helps identify potential issues before prototyping but is not mandatory for every project.
7. Prototypeβ
Prototype using:
- FDM 3D Printing
- SLA Printing
- CNC machining
- Laser cutting
Evaluate:
- Assembly
- Strength
- Ergonomics
- Manufacturability
8. Production Releaseβ
After validation, prepare all manufacturing documentation.
Typical deliverables:
- Manufacturing drawings
- Assembly drawings
- BOM
- CAD exchange files
Input / Output Summary
| Stage | Input | Output |
|---|---|---|
| Requirement Analysis | Product specification | Mechanical requirements |
| Concept Design | Requirements | Sketches / Concept art |
| CAD Modeling | Concept design | Fusion 360 models (.f3d) |
| Assembly Verification | CAD parts | Assembly model |
| Simulation (Optional) | Assembly | Simulation report |
| Prototype | STEP / STL | Physical prototype |
| Production Release | Verified CAD | Manufacturing files |
Manufacturing Outputs
Different manufacturing processes require different output formats.
| File | Purpose |
|---|---|
| .f3d | Native Fusion 360 project |
| .step | CAD exchange format for further editing in most CAD software |
| .stl | Mesh model for 3D printing |
| .3mf | Modern 3D printing format with material and printer settings |
| .dxf | 2D profile for laser cutting or CNC machining |
| Engineering drawings | |
| .csv | Bill of Materials (BOM) export |
Design Review Checklist
Before releasing a design, verify the following:
- CAD sketches are fully constrained
- No assembly interference
- PCB dimensions are verified
- Cable routing is feasible
- Screw locations are accessible
- Correct fasteners are selected
- Manufacturing tolerances are reasonable
- Material selection is appropriate
- Design supports assembly and maintenance
- Manufacturing files have been exported successfully
References
Recommended topics for further study:
- Parametric CAD Design
- Design for Manufacturing (DFM)
- Design for Assembly (DFA)
- GD&T (Geometric Dimensioning & Tolerancing)
- Injection Molding Design
- CNC Machining Design
- 3D Printing Design Guidelines
Store CAD projects, manufacturing drawings, design reviews, and revision history in this section.
Common Design Mistakesβ
The following issues are frequently encountered in mechanical design projects. Most of them can be avoided by following the complete workflow and performing a final design review.
Skipping Design for Manufacturing (DFM)
Designing only for appearance or functionality often leads to expensive manufacturing problems.
- Wall thickness outside manufacturer limits.
- Draft angles missing for injection molding.
- Internal corners impossible to machine with CNC.
- Tolerances beyond manufacturing capability.
- Features smaller than the selected process allows.
Result
- Higher manufacturing cost.
- Multiple redesign iterations.
- Production delays.
Choosing the Wrong Manufacturing Process
Each manufacturing process has different design constraints.
Examples:
- Designing an injection-molded enclosure then producing it with FDM printing.
- CNC parts containing impossible internal sharp corners.
- Sheet metal parts without bend allowance.
- Plastic parts designed with metal design rules.
Always decide the manufacturing process before detailed CAD modeling.
Ignoring 3D Printing Constraints
A printable model is not always an easy-to-print model.
Common issues include:
- Poor print orientation.
- Excessive support material.
- Large flat surfaces causing warping.
- Thin walls below printer capability.
- Parts exceeding build volume.
Large models should often be split into multiple printable pieces.
Not Splitting Large Parts
Very large components are difficult to manufacture.
Splitting the model can:
- Reduce print failures.
- Improve surface quality.
- Reduce support material.
- Simplify maintenance.
- Allow damaged sections to be replaced individually.
Design alignment pins, screw joints, or snap-fits before splitting the model.
Incorrect Units
Unit mistakes are surprisingly common.
Typical examples:
- Exporting inches instead of millimeters.
- Importing STEP files with incorrect scale.
- Mixing mm and cm in one project.
Always verify document units before exporting.
Not Verifying Exported Files
Never send files directly to a manufacturer without checking them.
Verify:
- Geometry is complete.
- No missing bodies.
- Correct orientation.
- Correct dimensions.
- Correct coordinate system.
Always open exported STEP or STL files using another CAD viewer.
Sharp Edges Everywhere
Leaving every edge perfectly sharp creates unnecessary problems.
Potential issues:
- Difficult assembly.
- Unsafe handling.
- Stress concentration.
- Poor product appearance.
Add chamfers or fillets whenever function allows.
Unrealistic Tolerances
Tighter tolerance does not always mean better quality.
Examples:
- Β±0.01 mm on plastic enclosures.
- Precision machining where clearance is acceptable.
Choose tolerances according to:
- Manufacturing capability.
- Functional requirements.
- Project budget.
Insufficient Assembly Clearance
A CAD assembly may look correct but still fail during real assembly.
Typical mistakes:
- USB connector cannot be inserted.
- Cable bend radius ignored.
- Fan blocked by nearby components.
- Screwdriver cannot access screws.
- PCB touches enclosure wall.
Always leave clearance for installation and maintenance.
Ignoring Standard Components
Avoid designing custom hardware unless absolutely necessary.
Prefer:
- Standard ISO screws.
- Standard bearings.
- Standard threaded inserts.
- Commercially available fasteners.
Standard components reduce both manufacturing and maintenance costs.
Poor Version Control
Production problems often come from file management rather than CAD.
Good practices:
- Use revision numbers.
- Archive released versions.
- Keep a change log.
- Never overwrite production files.
Before sending files to a manufacturer, verify:
- CAD model is fully constrained.
- Assembly has no interference.
- DFM review is complete.
- Material and manufacturing process are confirmed.
- STEP/STL files have been verified.
- Engineering drawings are complete.
- BOM and revision numbers are up to date.
A 15-minute review can prevent weeks of redesign.
A successful mechanical design is not only correct in CAD, but also:
- Easy to manufacture.
- Easy to assemble.
- Easy to maintain.
- Cost-effective.
- Compatible with the selected production process.
Design with the entire product lifecycle in mind.