How Custom 3D Printed Parts Are Made: The 3D Modeling Process Explained

When it comes to 3D modeling, not all workflows are created equal. Making custom 3D printed parts for manufacturing, engineering, or functional use is very different from creating models for visual effects, games, or animation. While artistic modeling focuses on aesthetics and visual storytelling, custom part modeling is all about precision, functionality, and real-world application.

In this post, we'll outline the steps to model custom 3D parts and turn ideas into production-ready designs.

How Custom 3D Printed Parts Are Made?

Designing custom 3D printed parts—whether for a machine bracket, an electronics housing, or a fully functional mechanical component—requires a high level of accuracy, well-defined constraints, and a clear understanding of how the part will be used and manufactured. Every decision, from material selection to dimensional tolerance, plays a critical role in the success of the final product.

Here’s a step-by-step look at how custom 3D parts are modeled.

1. Defining Requirements for a Custom 3D Part

The process of 3D printing custom parts begins by establishing the purpose and function of the part within the larger system.

This step sets the direction for the entire design process.

Key considerations at this stage include:

• What function will the part serve?

• What is the shape and structure of the part?

• Will it move, bear loads, or interface with other components?

• What are its exact dimensions, tolerances, and material requirements?

• How will it integrate with other parts or assemblies?

It's also important to choose the right manufacturing method—whether it's 3D printing, CNC machining, or injection molding—since each one has its own design rules and limitations. Since this is a 3D printing-focused guide, the following steps will only cover mechanical parts and processes suitable for 3D printing.

The first phase often involves gathering sketches, engineering drawings, technical specifications, and input from clients or collaborators. Defining these details early helps make sure the design works as intended and can be manufactured without issues.

2. Creating 2D Sketches

Once the requirements are clear, the next step is to create 2D sketches of the part’s base profiles. These sketches form the foundation of the 3D model, as they will later be converted into 3D geometry.

To create a 2D sketch, precise dimensions and geometric constraints (such as perpendicularity or tangency) must be applied. The sketch should be fully defined to eliminate ambiguity and maintain control over the shape.

Parametric CAD software is typically used for designing these sketches, allowing them to be easily modified later. This flexibility adds efficiency to the design process.

3. Building 3D Geometry for Custom 3D Printed Parts

Once the 2D sketch is finalized, the designer moves on to building the 3D geometry, transforming the flat profiles into a three-dimensional part.

This step is done using feature-based tools in CAD software, which allow for the creation of solid geometry. These tools enable the designer to define the shape of the part based on the initial 2D sketches, creating the necessary volume and structure.

Additionally, material can be added or removed through specific features like cuts, holes, fillets, and chamfers, which refine the part’s design and make it more functional for its intended use. These features help shape the part for ease of assembly, fit, or strength, depending on the design goals.

One of the key benefits of parametric modeling is its ability to maintain design flexibility—once the 3D geometry is created, designers can easily adjust dimensions or features and regenerate the model without the need to start from scratch. This parametric approach ensures that any changes made to one aspect of the design are automatically reflected across the entire model, streamlining revisions and ensuring consistency.

4. Adding Functional Features

After the basic 3D geometry is established, the next step is to add functional features that make the part work as intended in its real-world application.

These details are specific to the part’s role and may include mounting holes, threads, or slots for fastening or assembly. Structural elements like ribs can be added to increase strength without significantly increasing material usage, while bosses provide raised surfaces for connections or fasteners.

Learn more: Ordering 3D Printed Parts Online: A Modern Manufacturing Solution

5. Applying Constraints and Parameters

To make the design more adaptable and intelligent, constraints and parameters are applied during this stage. These define relationships between dimensions and features so that the model behaves predictably when changes are made.

This is often referred to as capturing design intent—for example, if one dimension changes, related dimensions automatically update to maintain proportionality or alignment.

Designers can use equations, design tables, or configurations to create multiple versions of the same part, such as different sizes or variations for specific applications. This parametric approach not only speeds up the design process but also ensures consistency and reduces errors when updates are needed later.

6. Assembling with Other Parts (if Needed)

If the custom component is intended to operate within a larger system, the subsequent step involves integrating it into a complete assembly.

This process enables the designer to assess how the part interacts with adjacent components, ensuring appropriate clearances, precise alignment, and smooth movement where necessary. By utilizing mates and constraints, the part can be accurately positioned and linked to others, mirroring real-world mechanical connections.

This step is essential for detecting any interferences, misalignments, or collisions that might lead to issues during assembly or operation. Validating the component in context helps avoid costly mistakes and ensures all parts function together as planned.

7. Validating the Design of the 3D Part

Before transitioning to production, it's crucial to verify the design of the 3D part to ensure it functions as intended and can be manufactured without complications.

This includes conducting a tolerance analysis to ensure the part achieves the necessary dimensional precision and fits properly with other components. For more demanding applications, Finite Element Analysis (FEA) might be employed to simulate the part's behavior under real-world conditions—such as stress, strain, or thermal loads—to identify potential failure points.

Additionally, interference and motion studies within the assembly are conducted to ensure that moving parts operate smoothly and do not collide. These validation steps are vital for delivering a functional, reliable, and production-ready part.

8. Generating Technical Drawings

With the 3D model finalized and validated, the next step is to create detailed 2D technical drawings for manufacturing. These drawings communicate all the critical information needed for production, including dimensions, multiple orthographic views, tolerances, and specific callouts for features like holes or threads.

Additional notes are often included to specify material type, surface finish, or any special requirements for fabrication. These drawings serve as the official documentation for manufacturers, quality inspectors, or collaborators. Once complete, they are typically exported in widely used formats such as DWG or PDF for easy sharing and printing.

9. Exporting for Manufacturing

Finally, the digital model must be exported in the appropriate file format based on the chosen manufacturing method.

For 3D printing, the standard format is STL, which represents the part’s surface geometry as a mesh. If the part is intended for CNC machining or needs to be shared across different CAD platforms, formats like STEP or IGES are commonly used due to their compatibility and precision. For in-house editing or future modifications, the model may also be saved in its native CAD format.

Selecting the correct export format ensures a smooth transition from design to production, avoiding issues related to file conversion or data loss.

10. Manufacturing and Production of a Custom 3D Printed Part

Once the 3D design file is ready, the production process begins—this is where digital design turns into a physical object. The first step is preparing the file for printing.

For 3D printing, the design (usually saved as an STL file) is opened in slicing software. This software converts the model into thin, horizontal layers and generates instructions the printer can follow. These layers are the foundation of how the object will be printed, one slice at a time.

The slicing software also lets you adjust key print settings, such as:

• Print speed – how fast the printer moves

• Layer height – the thickness of each layer, which affects detail

• Infill density – how solid or hollow the part will be inside

Support structures can also be added at this stage. These temporary features help stabilize overhanging or complex parts of the design during printing and are removed afterward.

Once all settings are dialed in, the software creates a sliced file formatted for the specific 3D printer. This file is then transferred to the printer, and the print begins.

The printer builds the object layer by layer, depositing material (like plastic, resin, or metal) according to the instructions. Each new layer sticks to the one before it, gradually forming the final shape.

It’s important to monitor the print closely. Errors or misalignments can lead to defects and may require changes to the settings.

This layer-by-layer process allows for detailed, complex shapes and speeds up prototyping and production—one of the biggest benefits of 3D printing over traditional methods.

11. 3D Printing Post Processing

After the 3D printing process is complete, custom 3D printed parts often require post-processing to achieve the desired surface finish, functionality, and aesthetics.

Common post-processing techniques include sanding and smoothing, where layer lines and imperfections are removed to create a smooth, uniform surface. Painting and coating are often applied to enhance the part’s appearance and provide protection, particularly for consumer products that need to be visually appealing and durable.

In cases where the custom part consists of multiple components, assembly may be necessary, which can involve methods like gluing, welding, or mechanical fastening to bring all the pieces together into a functional unit. These post-processing steps ensure that the final part meets both visual and functional requirements before it is put to use.

Please note that Perfecttio does not currently provide post-processing services. Parts are delivered exactly as they are produced by the 3D printer, without additional finishing.

3D Printing Technologies

There are several 3D printing technologies available, each suited for different applications and materials. Here are some of the most commonly used methods:

• Fused Deposition Modeling (FDM) is one of the most popular 3D printing methods. It works by extruding thermoplastic filament through a heated nozzle, layer by layer, to create the desired shape. This method is cost-effective and suitable for a variety of applications.

• Stereolithography (SLA) utilizes a UV laser to cure liquid resin into solid parts. This method provides high precision and is ideal for creating detailed and complex geometries.

• Selective Laser Sintering (SLS) uses a laser to sinter powdered material, binding it together to form a solid structure. This method is particularly effective for producing durable parts and is often used in engineering applications.

Material Selection: Best Material for 3D Printing

The best material for custom 3D printed parts depends on their use, with some materials being particularly strong or heat-resistant.

Polycarbonate is very strong and heat-resistant, making it suitable for load-bearing parts, protective gear, and high-performance components, but it requires a high-temperature printer. Nylon is great for tough, flexible parts like gears, hinges, and drone components due to its resistance to wear and ability to handle stress. For parts that need to be strong yet lightweight, carbon-fiber-reinforced composites are ideal, offering stiffness and stability for robotics, automotive, and aerospace applications.

For maximum strength and heat resistance, metal 3D printing with materials like stainless steel, titanium, or Inconel is best, but it is costly and needs specialized equipment. PETG is a good option for functional parts that require weather resistance and durability, such as outdoor mounts or containers, and it is easier to print than nylon or polycarbonate. For beginners or for non-functional items like prototypes and models, PLA is a popular choice because it is easy to use and produces good print quality, although it is not very strong or heat-resistant.

In summary, for serious mechanical applications, materials like polycarbonate, nylon, carbon-fiber composites, and metal provide the best performance, while PETG and PLA are more suitable for general or simpler needs.

Learn more: How Strong Are 3D Printed Parts?

Your company doesn’t have to handle 3D printing in-house. Order custom 3D printed parts online from us and take advantage of our professional 3D printing services. Contact us to learn more!