Two Parts with the Same Volume Can Cost Very Different

One of the most common assumptions in custom manufacturing is that parts using the same amount of material should cost roughly the same. At first glance, this seems reasonable: if both parts occupy the same volume, shouldn't they require the same resources to produce?

In reality, material cost is often only one factor in the final quote. Two parts with identical volumes can have dramatically different prices because manufacturing cost is largely determined by the time, complexity, and processes required to produce them. Whether you're using 3D printing, CNC machining, or another manufacturing method, design decisions can significantly influence production efficiency.

Image Copyright © 3DSPRO. All rights reserved.

Material Cost Is Only One Piece of the Quote

While raw material is an important cost factor, it rarely represents the majority of the manufacturing price, especially for custom or low-volume production.

A typical manufacturing quote includes several cost components, such as material consumption, machine operating time, machine setup and programming, labor, post-processing, and inspection and quality control.

For example, two aluminum CNC parts may each require the same amount of stock material. However, if one part takes twice as long to machine because of its geometry, its overall manufacturing cost will be considerably higher.

The same applies to 3D printing. The amount of resin, nylon powder, or metal powder used is only part of the equation. Printing time, machine occupancy, support removal, and finishing operations often contribute more to the final price than the material itself.

Complex Geometry Takes Longer to Manufacture

The complexity of a part is one of the biggest factors affecting manufacturing cost.

Even if two parts have the same volume, one may contain numerous design features that require additional production time. Examples include thin walls, deep pockets, internal channels, small holes, engraved text or logos, organic or freeform surfaces, and numerous ribs or reinforcing features.

For CNC machining, complex geometry often means more toolpaths, additional tool changes, and longer machining cycles. Each of these increases machine time, which directly impacts cost.

For 3D printing, complex features may increase slicing complexity and print duration. Fine details also require more careful post-processing to preserve dimensional accuracy and surface quality.

In many cases, simplifying non-critical design features can significantly reduce manufacturing costs without affecting the part's functionality.

Orientation and Support Requirements Can Change the Cost

For 3D printing, the way a part is oriented during printing can greatly influence both production time and post-processing effort.

Two parts with identical volumes may require completely different amounts of support material depending on their geometry and build orientation.

For example, consider two identical brackets:

• One is positioned flat on the build platform with minimal overhangs.

• The other is printed vertically, creating large unsupported areas that require extensive support structures.

Although both parts contain the same amount of material, the second version may require more support material, longer print time, additional labor for support removal, and extra surface finishing after support removal.

Build height also plays an important role. A taller part generally increases printing time because more layers must be completed, even when the total material volume remains unchanged.

Experienced manufacturing engineers often optimize build orientation to balance dimensional accuracy, surface quality, support usage, and production efficiency, which reduces costs without requiring any changes to the CAD model itself.

Tight Tolerances Increase Manufacturing Time

Precision comes at a cost.

Many engineers specify very tight tolerances throughout an entire design, even though only a few dimensions actually require that level of accuracy.

For example, producing a feature within ±0.10 mm is generally much easier than holding a tolerance of ±0.01 mm.

Achieving tighter tolerances may require additional machining passes, slower cutting speeds, more precise machine calibration, secondary machining after 3D printing, additional dimensional inspection, and higher rejection rates if parts fall outside specification.

These extra steps increase production time and labor, leading to higher manufacturing costs.

A better approach is to apply tight tolerances only where they are functionally necessary, such as mating surfaces, bearing seats, or precision assemblies. Allowing more generous tolerances for non-critical features often reduces manufacturing costs while maintaining product performance.

Surface Finish Requirements Add Additional Cost

Surface finishing is another major factor that influences manufacturing pricing.

Imagine two identical parts that leave the machine with the same dimensions. The first part is shipped in its standard as-machined or as-printed condition. The second part requires sanding or polishing, vapor smoothing, spray painting, anodizing, electroplating, or powder coating. Although the base part is identical, every finishing operation adds time, labor, equipment usage, and quality inspections.

Certain finishes also require masking specific areas, multiple coating stages, curing time, or additional cleaning processes. Decorative finishes often involve more manual work than functional finishes, further increasing production costs.

For many industrial components, an as-manufactured finish is perfectly acceptable. Reserving premium finishing processes for customer-facing products or functional requirements can help control overall project costs.

Quantity Can Change the Cost of the Same Part

Production quantity has a significant impact on unit pricing, even when the part design remains exactly the same.

For low-volume orders, setup costs are distributed across only a few parts, resulting in a higher unit price.

As quantities increase, manufacturers can improve efficiency in several ways:

• Machine setup is performed only once.

• CNC fixtures can be reused.

• Multiple parts can be nested within a single 3D printing build.

• Programming and inspection costs are spread across more units.

• Production scheduling becomes more efficient.

For example, a single custom part may require extensive setup before production even begins. Producing 100 identical parts allows those fixed costs to be shared across the entire batch, reducing the cost per part considerably.

This is why manufacturers often provide volume discounts. The reduction reflects genuine improvements in production efficiency.

Material volume alone does not determine manufacturing cost. Two parts with exactly the same volume can receive very different quotes because manufacturers are pricing the total production effort, not just the raw material.

Factors such as design complexity, machine time, support requirements, tolerances, surface finishing, and production quantity all contribute to the final cost. Understanding these variables helps engineers make informed design decisions that balance performance, manufacturability, and budget.