Understanding the Two Sides of CAD

If you’re developing a new product or preparing something for manufacturing, you’ll be asked whether you need 2D CAD, 3D CAD, or both. For many inventors, startups, and even experienced engineers, the difference isn’t always clear.

The truth is:
Both types of CAD serve very different purposes—yet most projects require a combination of the two.

In this guide, we'll explain the difference between 2D and 3D CAD, when each is used, and how to determine which one your project needs to move forward.

What Is 2D CAD?

2D CAD (Computer-Aided Drafting) creates flat, two-dimensional technical drawings that show length and width, but not depth. These are similar to traditional blueprints, but far more precise and flexible.

2D CAD drawings typically include:

• Dimensions

• Tolerances

• Notes and callouts

• GD&T annotations

• Section views

• Orthographic projections

• Flat patterns (for sheet metal)

• Hole tables and fastener lists

2D drawings communicate how a part should be made—they provide the instructions that machinists, fabricators, and manufacturers rely on.

Industries that rely heavily on 2D CAD:

• CNC machining

• Sheet metal fabrication

• Construction & architecture

• Patent documentation

• Mechanical engineering

• Manufacturing & quality control

2D CAD is essential because manufacturers cannot produce a part without clear, dimensioned information.

What Is 3D CAD?

3D CAD modeling creates digital, three-dimensional representations of parts, assemblies, products, or mechanical systems.

These models can be rotated, analyzed, tested, and modified in ways that 2D drawings cannot achieve.

3D CAD models allow you to:

• Visualize a part from all angles

• Check clearances and fitment

• Build assemblies

• Simulate motion

• Perform stress tests (optional)

• Prepare files for CNC or 3D printing

A 3D model becomes the “source of truth” for how your product exists in real space.

Common uses of 3D CAD:

• Prototyping

• Product design

• Mechanical assemblies

• 3D printing & additive manufacturing

• CNC machining toolpaths

• Injection molding design

• Industrial design

Once the 3D model is complete, it can be converted into a variety of manufacturing file formats (STEP, IGES, STL, etc.)

Key Differences Between 2D and 3D CAD

Both are important—but for different stages of development.

When Do You Need 2D CAD?

You need 2D CAD when precise, clear communication is required for manufacturing or quality inspection.

2D CAD is required when:

• A machinist is cutting your part

• A sheet metal fabricator needs a flat profile

• You’re creating patent drawings

• You need tolerance details

• You’re producing assembly instructions

2D CAD drawings provide the official documentation—the “rulebook”—for how a part is made.

Typical 2D deliverables include:

• Orthographic views

• Section and detail views

• Dimensioned drawings

• Material and finish notes

• GD&T frames

• Hole tables

Even if you have a perfect 3D model, manufacturers will often still request a 2D drawing.

When Do You Need 3D CAD?

A 3D model is essential when designing, prototyping, or manufacturing a new part or product.

You need 3D CAD when:

• You’re developing a new invention

• You’re ready for 3D printing

• You’re preparing a product for CNC machining

• You want to visualize your idea

• You need to test assembly fitment

• You’re creating an enclosure or mechanical system

Without 3D CAD, you can’t build a prototype or send a part to production.

Typical 3D deliverables include:

• STEP

• IGES

• STL

• SolidWorks files

• Fusion 360 files

3D CAD represents the actual shape, size, and form of the product.

Why Most Projects Need BOTH 2D and 3D CAD

Even though 2D and 3D CAD are different, they work together in product development.

3D CAD

→ Helps design the part, visualize it, refine it, and prepare for prototyping.

2D CAD

→ Tells the manufacturer exactly how to make it.

For example:

Step 1: A 3D model is created
Step 2: 2D drawings are generated from that 3D model
Step 3: Manufacturer uses both files to produce the part accurately

Together, they ensure what is built is exactly what was designed.

How Do You Know Which Type of CAD You Need?

Here’s a simple guide:

If you want to see your idea in 3D form:

→ You need 3D CAD

If you want to manufacture a part:

→ You need 2D drawings AND 3D CAD

If you're filing a patent:

→ You need 2D drawings

If you're 3D printing:

→ You need 3D CAD

If you're CNC machining:

→ You need 3D CAD + 2D drawings

If you're designing an assembly:

→ You need 3D CAD

If you want to revise or improve an existing design:

→ Either 2D or 3D CAD, depending on the level of detail

Common CAD Mistakes to Avoid

❌ Only providing a sketch to a manufacturer

Manufacturers cannot build from sketches.

❌ Assuming a 3D file is enough for CNC machining

Most machinists require a dimensioned 2D drawing.

❌ Using the wrong CAD format

Different industries require different file types.

❌ Skipping tolerances

Without tolerances, parts may not fit or function.

Avoiding these pitfalls saves time, money, and frustration during production.

How NPDCAD Helps You Choose the Right CAD

At NPDCAD, we provide:

• 2D CAD drafting

• 3D CAD modeling

• Manufacturing-ready drawings

• Patent drawings

• Assembly documentation

• Rapid prototyping support

We assess your project and help you determine exactly what you need—no guesswork, no confusion.

Whether you’re at the idea stage or ready for manufacturing, our team delivers fast, accurate CAD files tailored to your next step.

Ready to Get the Right CAD for Your Project?

Upload your sketch, drawing, or idea today and get professional CAD drafting designed for real-world manufacturing.

NPDCAD — Your partner in accurate, production-ready CAD.