How to choose between precision machining and metal 3D printing for your next project.
If you're weighing up CNC vs. DMLS for your next component, you're not alone. Engineers and designers often face this decision when prototyping or producing complex metal parts. Each process comes with strengths and limitations. This guide breaks down the differences, from materials and surface finishes to cost, speed, and complexity, so you can choose the method that best fits your needs.
What Is CNC Machining?
CNC (computer numerical control) machining is a subtractive manufacturing process that removes material from a solid block using cutting tools. It includes milling, turning, and drilling. Each operation is programmed for precise movements and repeatable outcomes.
CNC is known for its fast lead times, accuracy, repeatability, and the ability to create complex geometries from a wide range of metals and plastics. It's ideal for both rapid prototyping and mid-volume production, especially when tight tolerances and smooth finishes are required.
What Is DMLS?
Direct Metal Laser Sintering (DMLS) is an additive manufacturing process that builds parts layer by layer from fine metal powder, using a high-powered laser to fuse the particles together.
DMLS excels at producing geometrically complex or lightweight structures, including internal channels or lattices that would be impossible to achieve with traditional manufacturing. It's also tooling-free, which means engineers can iterate faster during early design phases.
Things to Consider When Selecting a Manufacturing Method
Choosing the right manufacturing method goes beyond just geometry or cost. You also need to account for material requirements, surface finish expectations, design complexity, and how quickly you need the part in hand. Here are a few quick directional cues to get you started:
- Need material variety → CNC machining offers plastics and a wide range of metals
- Need complex internal features → DMLS works for intricate, organic geometries
- Need ultra-smooth finishes or tight tolerances → CNC machining excels here
- Need to eliminate assembly steps → DMLS supports part consolidation
CNC vs. DMLS at a Glance
|
Feature |
CNC Machining |
DMLS |
|
Process type |
Subtractive |
Additive |
|
Material types |
Metals & plastics |
Metals only |
|
Best for |
Precision, surface finish, repeatability |
Complex geometries, low-volume metal prototyping |
|
Lead time |
Shorter (for most parts) |
Longer (due to printing + post-processing) |
|
Cost efficiency |
Better at volume |
Better for complexity and part consolidation |
DMLS Aero Auto
Material Capabilities
Material selection impacts performance, cost, and process compatibility. CNC machining supports a broad material palette including aluminium, stainless steel, copper and brass, titanium, and a range of plastics like ABS, nylon, POM, and PTFE. This flexibility allows engineers to select materials based on strength, thermal properties, and machinability.
DMLS is limited to metal powders but includes advanced alloys such as aluminium, Inconel 718, stainless steel 316L, titanium, and cobalt chrome. These materials are great for high-performance applications where strength-to-weight ratio, corrosion resistance, or heat resistance is required.
Surface Finishes and Tolerances
Surface quality and dimensional accuracy are fundamental for proper function and fit. While both CNC machining and DMLS can deliver high-quality results, the processes are considerably different.
CNC parts are usually very smooth right off the machine, with Ra values as low as 0.8 μm. You can also add finishes like anodising, bead blasting, or powder coating depending on the material and application. Tolerances can go down to ±0.025mm, which makes CNC a solid option for tight-fitting components.
DMLS parts come out of the printer with a rougher texture at around 10–15 μm Ra. But you can smooth things out using machining, polishing, tumbling, or chemical finishing. Standard tolerances are around ±0.1mm, but can also be tightened up with secondary machining on critical features. Just keep in mind that extra finishing steps can add time and cost.
Advantages
Each technology has its strengths depending on your design goals, material requirements, and complexity.
CNC machining
- High precision and tight tolerances
- Excellent surface finishes and wide post-processing options
- Supports metals and plastics
- Shorter lead times for simpler geometries
DMLS
- Ideal for highly complex or organic shapes
- No tooling needed
- Generates less waste since it builds parts additively
- Good for lightweight or consolidated parts
Disadvantages
Every process has its trade-offs depending on part design and production needs.
CNC machining
- Less suitable for complex internal features
- Produces more waste due to the subtractive process
DMLS
- Limited to specific metal powders
- Surface finish requires post-processing
Production Volume and Lead Times
Production speed and scale can influence which method is right for your project. CNC machining is often preferred for rapid prototyping through mid-volume production due to shorter setup times and predictable lead times. Protolabs’ CNC parts can ship from one business day.
DMLS is better for one-off prototypes or low-volume production of geometrically complex parts. However, lead times tend to be longer due to the layering process, powder handling, and required post-processing.
CNC vs. DMLS: Lead Times and Volumes
|
|
CNC Machining |
DMLS |
|
Typical lead time |
1–3 business days |
5–7 business days |
|
Volume sweet spot |
1–10,000 parts |
1–50 parts |
Cost Comparison
Money matters, and each technology hits your budget differently depending on how you use it. CNC machining generally becomes more economical at scale because setup costs are spread across more parts, and machines can run efficiently for repeat jobs. However, costs can increase with part complexity, tight tolerances, or high-end materials.
DMLS often has higher per-part costs, largely due to metal powder pricing, print time, and post-processing. That said, it can be more cost-effective in applications that benefit from part consolidation, weight reduction, or complex design features that would otherwise require multiple steps.
Use Cases and Industry Fit
Both CNC and DMLS serve a wide range of industries.
CNC is often the go-to for aerospace and automotive brackets, enclosures, medical housings, gears, and jigs—where tolerances, finishes, and durability are the top priorities. It’s also used frequently in industries like energy, consumer electronics, and industrial machinery when material durability and repeatability are important.
DMLS is ideal for parts like heat exchangers, lightweight structural components, and conformal cooling channels because it can build complex internal features—such as lattices and embedded flow paths—directly into a single printed part, without tooling or assembly. These advanced designs are commonly used in aerospace, robotics, and high-performance automotive applications, where weight reduction and part consolidation are critical.
Here's a quick comparison to show where each process excels:
|
CNC Machining |
DMLS |
|
|
Structural brackets, housings, and flight-certified components requiring tight tolerances and strength |
Lightweight lattice structures, heat exchangers, and consolidated parts with internal cooling channels |
|
|
Surgical tools, implant housings, and enclosures with smooth finishes and biocompatibility |
Patient-specific implants, porous bone scaffolds, and complex anatomical shapes |
|
|
Drivetrain parts, engine prototypes, and brackets for repeatable and durable performance |
Custom mounts, lightweight or heat-resistant parts for motorsport and EV applications |
|
|
End-effectors, housings, and fixtures where strength and precision are key |
Topology-optimised joints, sensor housings, and integrated geometries that reduce part count |
FAQs: CNC vs. DMLS
What is the difference between CNC machining and DMLS?
expand_less expand_moreCNC is a subtractive process using cutting tools on solid material, while DMLS is additive, building parts layer by layer from metal powder.
Which process is more precise?
expand_less expand_moreCNC machining typically offers tighter tolerances and smoother finishes, especially for critical surfaces.
Can DMLS replace CNC?
expand_less expand_moreNot entirely. DMLS excels at complex geometries but can benefit from hybrid approaches that finish certain surfaces with CNC.
Is DMLS better for prototyping?
expand_less expand_moreFor complex metal prototypes, yes. But for simpler designs or plastic parts, CNC is usually faster and cheaper.
Which is better for aerospace parts?
expand_less expand_moreBoth are used widely. CNC is preferred for load-bearing or high-tolerance parts. DMLS shines in lightweight or consolidated designs.
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Need more help deciding between CNC machining and DMLS? Upload your CAD model for a quick, interactive quote. |
