CAD Basics | Tier-1 Engineer

The process excels at producing large, lightweight, thin-walled parts with good cosmetic quality on one side and relatively low tooling cost. Common applications include packaging trays, blister packs, appliance liners, refrigerator interiors, automotive interior panels, medical trays, and point-of-purchase displays. These parts are typically produced in the thousands to hundreds of thousands, where injection molding tooling cost or lead time cannot be justified.

Thermoforming equipment generally consists of a sheet clamping system, a heating station, a forming station using vacuum and or pressure, a cooling stage, and a trimming operation. Tooling is typically aluminum or composite rather than hardened steel, which keeps cost and lead time low but limits precision and durability.

Thermoforming performs best when it is selected intentionally and designed honestly. Most production issues trace back to designs that assume injection-molding behavior from a process that fundamentally does not behave that way.

COMPUTER-AIDED DESIGN BASICS

Computer-Aided Design, usually called CAD, is the foundation of modern engineering and product development. Nearly every manufactured object today begins as a digital model created inside CAD software before it ever reaches a machine, mold, or assembly line. Engineers, designers, machinists, architects, and hobbyists all rely on CAD tools to turn ideas into precise digital geometry that can be analyzed, refined, and ultimately manufactured.

For beginners, CAD can be a bit overwhelming and tedious at first. There are dozens of software packages, hundreds of commands, and an entire vocabulary of terms and conventions that you'll come across regularly.

The good news: most CAD systems share the same core concepts and modeling tools. Once you understand the fundamentals of sketches, features, constraints, and geometry, the differences between programs become much easier to navigate.

This page introduces the basic building blocks of CAD without drowning you in theory. The goal is to help you understand how CAD tools fit into the real design workflow, what the most common commands actually do, and how digital models move from the screen into real-world parts. Whether you’re an aspiring engineer, a maker learning design for the first time, or someone curious about how products are created, these fundamentals will give you a solid starting point.

TYPES OF CAD

SOFTWARE

Computer-Aided Design software comes in several different forms, each optimized for a specific type of design work. While all CAD programs allow you to create digital models of parts and assemblies, the way those models are built and edited can vary significantly between software categories. Many CAD programs have some or all of these modeling variations built into them by default, giving designers a large amount of capabilities.

For beginners, the most important distinction is between parametric modeling, direct modeling, surface modeling, and mesh modeling. Each approach handles geometry differently and tends to be used in different industries or workflows.

For most beginners interested in engineering, product design, or mechanical parts, parametric CAD is the best place to start. It provides the most control over dimensions, allows easy modifications, and integrates well with manufacturing workflows. Other modeling approaches become useful later when working with complex surfaces, scanned geometry, or specialized design tasks.

PARAMETRIC MODELING

Parametric CAD is the most common type of CAD software used in engineering and manufacturing. Parts are built using a sequence of features such as sketches, extrusions, cuts, and fillets. Each feature is defined by dimensions and parameters, allowing the model to update automatically when those values change.

This approach makes it easy to edit designs later in the development process. If a dimension changes, the rest of the model adjusts automatically while preserving the overall design intent.

Direct modeling allows geometry to be modified without relying on a structured feature history. Instead of editing sketches or parameters, designers can directly push, pull, or reshape surfaces and features. This approach can be very fast when making quick modifications, especially when working with imported models that do not contain editable feature histories. Most serious CAD programs have some form of direct modeling capabilities built into the software.

Direct modeling is often used for rapid concept changes, model cleanup, or editing third-party geometry.

DIRECT MODELING

SURFACE MODELING

Surface modeling focuses on creating complex, free-form shapes rather than solid mechanical parts. Instead of building geometry from simple sketches and extrusions, designers create surfaces that define the outer shape of an object.

This approach is commonly used in industries where aesthetic shape and aerodynamic performance are important, such as automotive design, consumer products, and industrial design.

Surface models are typically converted into solid parts later in the design process.

MESH MODELING

Mesh modeling works with geometry made up of thousands or millions of small triangles or polygons rather than mathematically defined surfaces. This type of modeling is most often associated with 3D scanning, sculpting, and additive manufacturing workflows.

Mesh models are commonly used for 3D printing, scanned geometry, organic shapes, and digital sculpting.

Because mesh geometry is not dimension-driven, it can be more difficult to edit precisely compared to parametric CAD models.

2D MODELING

2D modeling focuses on creating flat technical drawings rather than full 3D models. Instead of building parts as solid objects, designers create geometry using lines, arcs, circles, and annotations that represent the shape and dimensions of a part or structure.

Historically, this was the digital replacement for hand drafting. Today, 2D CAD is still widely used in industries where detailed drawings, layouts, or schematics are more important than 3D models.

Because the geometry exists only in two dimensions, 2D CAD programs are generally simpler to learn and faster to use.

SOFTWARE

COMPARISON

While the fundamentals of CAD modeling are similar across most programs, different software packages are designed for different types of users and industries. Some tools focus on accessibility and ease of learning, while others are built for extremely complex engineering programs involving thousands of parts and advanced manufacturing workflows.

For beginners and makers, the most important differences usually come down to cost, ease of use, performance, and overall capability. The programs below represent the most widely used CAD platforms across hobbyist, professional, and enterprise design environments.

If you are just getting started with CAD, tools like Fusion 360 or Onshape are usually the easiest entry points because they are accessible, affordable, and widely supported by tutorials and community resources.

As designs become more complex or move into large-scale engineering environments, more advanced platforms such as SolidWorks, NX, or CATIA are commonly used in industry.

Fusion is one of the most accessible CAD platforms for beginners and independent designers. It combines parametric modeling, simulation, CAM, and basic electronics design into a single integrated environment. Because it runs largely through cloud services, it is easy to install and collaborate with others.

Fusion is commonly used by makers, startups, small engineering teams, and hobbyists, and it is often the first professional CAD system that new designers learn.

AUTODESK FUSION

NATIVE FILE TYPE: .F3D

Very beginner friendly

Integrated CAD, CAM, FEA tools

Affordable, free hobby license

Hit and miss performance

Relies on cloud services

Lacks power in complex tasks

FreeCAD is an open-source parametric CAD program that aims to provide many of the capabilities of professional engineering software without the licensing costs. Because it is developed by an open community, it includes many powerful tools but can feel less polished than commercial alternatives.

FreeCAD is attractive for students, hobbyists, and engineers who want a free parametric modeling tool, though the workflow and interface can sometimes feel less streamlined than commercial software.

FREECAD

NATIVE FILE TYPE: .FCStd

Free and open-source

Complex parametric modeling

Highly customizable

Unintuitive interface

Intermittent performance issues

Can be finnicky

SolidWorks is one of the most widely used parametric CAD systems in mechanical engineering and product design. It offers a mature modeling environment with strong tools for assemblies, simulation, and manufacturing preparation.

Because of its balance between capability and usability, SolidWorks is often used by mid-sized engineering teams, product designers, and manufacturing companies. Many universities also teach SolidWorks as an introduction to professional CAD workflows.

SOLIDWORKS

NATIVE FILE TYPE: .SLDPRT / .SLDASM

Extremely popular in industry

Good assembly and drawing tools

Large user community

Expensive licensing and upkeep

Poor large model performance

Windows-only

NX is a high-end engineering platform used in industries where products are extremely complex and precision is critical. It combines advanced parametric modeling, surfacing, simulation, manufacturing programming, and product lifecycle management tools in one environment.

NX is commonly used in aerospace, automotive, defense, and advanced manufacturing, where engineering teams manage very large assemblies and sophisticated production workflows.

SIEMENS NX

NATIVE FILE TYPE: .PRT

Extremely powerful overall

Integrated CAD, CAM, FEA tools

Excellent performance

Extremely expensive

Steep learning curve

Overkill for simple design work

CATIA is a powerful CAD system widely used in aerospace and automotive design, particularly for complex surface modeling and large-scale product development. It is known for its advanced surfacing tools and ability to manage extremely complex assemblies.

CATIA is commonly used by companies such as Airbus, Boeing, and major automotive manufacturers where complex geometry and integrated engineering environments are critical.

CATIA

NATIVE FILE TYPE: .CATPART / .CATPRODUCT

Excellent surface modeling tools

Best for very large assemblies

Good integration into PLM/ERP

Very expensive licensing

Excessively steep learning curve

Very unintuitive user interface

Onshape is a modern CAD platform that runs entirely in a web browser. Instead of storing files locally, designs are managed through a cloud-based system that allows multiple engineers to collaborate on the same model simultaneously.

This approach makes Onshape particularly appealing for distributed teams, education environments, and startups that prioritize collaboration and accessibility.

ONSHAPE

NATIVE FILE TYPE: N/A - CLOUD BASED

Web browser based

Real-time collaboration features

Accessible across devices

Internet connection required

Subscription based

Internet-driven performance

Inventor is Autodesk’s traditional mechanical engineering CAD platform. It focuses on parametric modeling, assemblies, and engineering drawings for mechanical systems and manufacturing.

Inventor is commonly used in industrial design, mechanical equipment development, and manufacturing companies, particularly those already using Autodesk’s broader software ecosystem.

AUTODESK INVENTOR

Good parametric modeler

Easy learning curve

Intuitive user interface

Fairly expensive

Less common in industry

Windows-only

NATIVE FILE TYPE: .IPT / .IAM

PROGRAM COMPARISON

PROGRAM

COST

LEARNING CURVE

PERFORMANCE

CAPABILITY

TYPICAL USERS

FUSION

LOW/

FREE

GENTLE

MODERATE

MAKERS, START-UPS

FREECAD

FREE

MODERATE

HOBBYISTS,

MAKERS

SOLIDWORKS

HIGH

MODERATE

HIGH

ENGINEERING

COMPANIES

VERY

HIGH

STEEP

VERY HIGH

AEROSPACE,

AUTOMOTIVE

CATIA

VERY

HIGH

VERY

STEEP

VERY HIGH

AEROSPACE,

AUTOMOTIVE

ONSHAPE

LOW

GENTLE

HIGH

MECHANICAL

DESIGN FIRMS

INVENTOR

HIGH

GENTLE

HIGH

START-UPS,

EDUCATION

COMMANDS

AND FEATURES

As designs become more complex or move into large-scale engineering environments, more advanced platforms such as SolidWorks, NX, or CATIA are commonly used in industry.

*Autodesk Fusion 360 has a majority share in the hobbyist and entry level spheres. Accordingly, the commands below are derived from Fusion 360, with command names for other CAD programs listed for reference.

SKETCH

WHAT IT IS:

A two-dimensional drawing made from lines, arcs, circles, and other shapes that defines the profile of a feature.

WHEN TO USE IT:

Sketches are the foundation of most CAD models. Designers create profiles on reference planes, apply dimensions and constraints to control the geometry, and then use those sketches to generate three-dimensional features like extrusions or revolutions.

SKETCH

EXTRUDE

A feature that creates a three-dimensional shape by extending a 2D sketch profile in a straight direction.

WHAT IT IS:

Extrude is one of the most commonly used CAD features. It is used to create prismatic shapes such as plates, blocks, bosses, and pockets by pushing a sketch profile into or out of a solid body.

WHEN TO USE IT:

PAD

EXTRUDED BOSS

EXTRUDE

PAD

EXTRUDE

EXTRUSION

REVOLVE

A feature that creates a 3D shape by rotating a sketch profile around a central axis.

WHAT IT IS:

Revolve is commonly used to create cylindrical or rotational parts like shafts, knobs, pulleys, and containers. By spinning a sketch around an axis, designers can quickly generate symmetrical geometry.

WHEN TO USE IT:

REVOLUTION

REVOLVED BOSS

REVOLVE

SHAFT/ GROOVE

REVOLVE

CUT

A feature that removes material from an existing solid body using a sketch or defined shape.

WHAT IT IS:

Cut operations are used to create internal geometry such as pockets, slots, and cavities. They work similarly to extrusion features but subtract material rather than adding it.

WHEN TO USE IT:

POCKET

EXTRUDED CUT

SUBTRACT

POCKET

REMOVE

EXTRUDE CUT

HOLE

A specialized feature used to create holes with defined diameter, depth, and placement.

WHAT IT IS:

Hole tools simplify the creation of drilled, tapped, or counterbored holes. Instead of modeling holes manually, designers can quickly apply standard hole types commonly used for fasteners and mechanical assemblies.

WHEN TO USE IT:

HOLE

HOLE WIZARD

HOLE

COMBINE

A feature that merges two or more solid bodies into a single body.

WHAT IT IS:

Unite operations are used when a part is built from multiple bodies that eventually need to behave as one solid object. This is common in multi-body modeling workflows where features are created separately and combined later.

WHEN TO USE IT:

BOOLEAN

COMBINE

UNITE

ADD

UNION

COMBINE

FILLET

A rounded transition between two intersecting edges or surfaces.

WHAT IT IS:

Fillets remove sharp corners and create smoother transitions between surfaces. They are used to improve part strength, reduce stress concentrations, and create geometry that is easier to manufacture.

WHEN TO USE IT:

FILLET

EDGE BLEND

EDGE FILLET

FILLET

CHAMFER

A beveled edge that replaces a sharp corner between two surfaces.

WHAT IT IS:

Chamfers are often applied to remove sharp edges, guide parts during assembly, or prepare edges for manufacturing processes such as machining. They are commonly used around holes and mating edges.

WHEN TO USE IT:

CHAMFER

SHELL

A feature that hollows out a solid body while maintaining a uniform wall thickness.

WHAT IT IS:

Shell operations are commonly used when designing enclosures, housings, and molded parts. The feature removes internal material while leaving a consistent outer wall thickness.

WHEN TO USE IT:

THICKNESS

SHELL

DRAFT

A taper applied to vertical faces of a part.

WHAT IT IS:

Draft angles are required in manufacturing processes such as injection molding and die casting. The taper allows parts to release from molds without sticking or damaging the tooling.

WHEN TO USE IT:

DRAFT

DRAFT ANGLE

DRAFT

FACE DRAFT

PATTERN

A feature that duplicates geometry in a repeating arrangement.

WHAT IT IS:

Patterns allow designers to replicate features such as holes, ribs, or bosses across a part. They can be arranged in linear, circular, or more complex patterns, making it faster than recreating each feature individually.

WHEN TO USE IT:

PATTERN

PLANE

A reference plane that provides a location for sketches or features that do not align with existing surfaces.

WHAT IT IS:

Datum planes allow designers to build geometry at specific positions and angles in a model. They are commonly used when creating complex parts where features must be placed away from existing faces.

WHEN TO USE IT:

DATUM PLANE

REFERENCE PLANE

DATUM PLANE

PLANE

WORK PLANE

MIRROR

A feature that copies geometry symmetrically across a reference plane.

WHAT IT IS:

Mirror tools are used when a part contains symmetrical geometry. Designers create one side of the model and then mirror the features across a plane, saving time and ensuring both sides remain identical.

WHEN TO USE IT:

MIRROR

MIRROR FEATURE

SYMMETRY

MIRROR

COMMON

FILE TYPES

Modern product design workflows involve many different file formats, each created for a specific purpose in the design, manufacturing, or documentation pipeline. Some formats store fully editable parametric models, while others are neutral exchange formats used to move geometry between different CAD programs.

Understanding the difference between these file types is important because not every format preserves the same information. Some files maintain feature history, sketches, and constraints, while others only contain the final geometric shape of the part.

In practice, engineers often move between several file types during a project. A designer may create a part in a native CAD format, export a neutral file to share with another company, and generate additional formats for drawings, visualization, or manufacturing.

The formats below represent the most common file types encountered in everyday engineering and product development. In most production workflows, engineers typically send STEP or Parasolid files when sharing 3D models with suppliers or manufacturers. These formats reliably preserve solid geometry without locking the file to a specific CAD program. Mesh formats like STL or OBJ are usually reserved for visualization, scanning, or additive manufacturing rather than traditional machining or fabrication.

STEP

.STEP

.STP

STEP (Standard for the Exchange of Product Data) is a widely used neutral file format designed to transfer 3D models between different CAD programs.

WHAT IT IS:

STEP files are commonly used when sharing geometry between companies or software systems. They preserve the overall solid geometry of the part but typically remove feature history and parametric information.

WHEN TO USE IT:

IGES

.IGES

.IGS

IGES (Initial Graphics Exchange Specification) is an older neutral format used to transfer geometry between CAD systems.

WHAT IT IS:

IGES files are still used in some legacy workflows, especially when exchanging surface geometry. However, many modern engineers prefer STEP because it typically produces more reliable solid models.

WHEN TO USE IT:

PARASOLID

.X_T

.X_B

Parasolid is a geometric modeling format based on the Parasolid CAD kernel developed by Siemens. Many modern CAD systems use this kernel internally for their solid modeling engine.

WHAT IT IS:

Parasolid files are commonly used to exchange solid models between compatible CAD systems. Because many programs share the same modeling kernel, Parasolid files often import more cleanly than other neutral formats.

WHEN TO USE IT:

.JT

JT is a lightweight 3D data format developed by Siemens that is designed for visualization, collaboration, and product lifecycle management workflows.

WHAT IT IS:

JT files are commonly used to share product geometry without distributing the full CAD model. The format allows teams to view data, measure geometry, and perform design reviews while keeping the original models secure.

WHEN TO USE IT:

STL

.STL

STL (Stereolithography) is a mesh-based file format that represents a 3D shape using a network of triangles.

WHAT IT IS:

STL files are widely used for 3D printing and rapid prototyping. Because the geometry is converted into a triangular mesh, these files cannot easily be edited like normal CAD models.

WHEN TO USE IT:

OBJ

.OBJ

OBJ is a mesh-based 3D file format that represents geometry using vertices, edges, and polygon faces rather than solid CAD geometry.

WHAT IT IS:

OBJ files are used for visualization, rendering, 3D scanning, and some additive manufacturing workflows. Because the geometry is stored as a polygon mesh, the model behaves more like a graphical object than an editable CAD part.

WHEN TO USE IT:

3MF

.3MF

3MF (3D Manufacturing Format) is a modern 3D printing file format developed by the 3MF Consortium to store complete additive manufacturing data in a single file.

WHAT IT IS:

3MF files are used in 3D printing workflows to store mesh geometry along with additional information such as color, materials, units, and print settings. Compared to STL, 3MF preserves more information regarding printing.

WHEN TO USE IT:

DXF

.DXF

DXF (Drawing Exchange Format) is a 2D vector format originally developed by Autodesk.

WHAT IT IS:

DXF files are commonly used for laser cutting, waterjet cutting, CNC plasma cutting, and other manufacturing processes that require flat 2D profiles.

WHEN TO USE IT:

DWG

.DWG

DWG is the native drawing format used by AutoCAD and many drafting programs.

WHAT IT IS:

DWG files store detailed technical drawings, layouts, and schematics. They are commonly used for documentation and architectural drafting.

WHEN TO USE IT:

PDF

.PDF

PDF files are commonly used to share engineering drawings in a format that can be viewed without CAD software.

WHAT IT IS:

PDF drawings are used for documentation, supplier communication, and manufacturing instructions. While they are easy to share and read, they cannot be edited as CAD models.

WHEN TO USE IT:

FILE TYPE