3D Printing vs. CNC Machining: Which One Is Best?

What Are 3D Printing and CNC Machining?

3D printing makes things by adding layers. It builds objects up one layer at a time.

CNC machining makes things by cutting material away. It starts with a big block and cuts parts off.

Let’s see what makes them different and when to use each one!

How 3D Printing Works

3D printing works like magic! It builds things layer by layer from the bottom up.

Types of 3D Printing:

• FDM – uses hot plastic string
• SLA – uses light to harden liquid
• SLS – uses lasers to melt powder

Good Things About 3D Printing:

• Can make weird shapes that CNC can’t make
• Cheap to make just a few items
• Not much waste

Not-So-Good Things:

• Parts are not as strong
• Only works with some materials
• Not as smooth as CNC parts

How CNC Machining Works

CNC machining cuts away parts from a big block of material. The machine follows a computer program to know what to cut.

Types of CNC Machining:

• 3-Axis cutting (moves in 3 directions)
• 5-Axis cutting (moves in 5 directions)
• Swiss Machining (for tiny parts)

Good Things About CNC Machining:

• Makes strong parts
• Very exact (up to ±0.025mm)
• Works with many materials (metal, wood, plastic)

Not-So-Good Things:

• Wastes a lot of material
• Costs more for small jobs
• Can’t make some complex shapes

3D Printing vs. CNC Machining: Side by Side

Let’s look at how they compare:

When to Use 3D Printing

Use 3D printing when:

1. You need just a few parts
2. You are making a test or model
3. You need complex shapes
4. You need it made fast
5. You are making plastic parts

Real Examples:

• Medical: Custom fit teeth models
• Airplane: Light parts with holes inside
• Art: Odd shapes that can’t be cut

GE Aviation used 3D printing for fuel parts and made them 25% lighter!

When to Use CNC Milling

Use CNC machining when:

1. You need lots of parts
2. You need strong parts
3. You need exact sizes (±0.025mm)
4. You need metal parts
5. You make more than 100 of the same part

Real Examples:

• Cars: Strong engine parts
• Medical: Super exact tools for surgery
• Planes: Parts that must not break

Aerospace brackets made with CNC are stronger (900+ MPa) than 3D printed ones (600 MPa).

Materials That Work Best

3D Printing Materials:

• Plastics: ABS, PLA, PEEK
• Resins: Clear, tough, flexible
• Some Metals: Steel, titanium (but not as strong)

CNC Machining Materials:

• Metals: Steel, aluminum, titanium, brass
• Plastics: All types
• Wood: All types
• Others: Glass, ceramic, composites

Fun fact: CNC can cut materials that are 5 times harder than what 3D printing can use!

Cost: What You Really Pay

3D Printing Costs:

• Machine: $200-$5,000 for basic ones
• Material: $20-$50 per kg
• Labor: Not much needed
• Hidden costs: Sanding, cleaning up support parts (1-3 hours of work)

CNC Machining Costs:

• Machine: $5,000-$500,000
• Material: More waste (up to 70%)
• Labor: Skilled workers cost more
• Setup: Takes time to set up (costs more)

For 10 parts:

• 3D printing: $200 total
• CNC machining: $1,200 total

But for 500 parts, CNC becomes much cheaper!

Speed: How Fast Can You Get Parts?

3D Printing Speed:

• Small part: 2-6 hours
• Medium part: 12-24 hours
• Complex part: 24-48 hours

CNC Machining Speed:

• Simple metal part: 4-8 hours
• Complex part: 1-5 days
• Setup time: 1-4 hours

A car part case study showed:

• CNC made it in 6 hours
• 3D printing took 18 hours

Precision: How Exact Are The Parts?

3D Printing Precision:

• FDM: ±0.5mm
• SLA: ±0.1mm
• Layer lines show up on parts

CNC Machining Precision:

• Standard: ±0.025mm
• High-end: ±0.01mm
• Smooth finish

Medical tool makers use CNC because it can be 40 times more exact than basic 3D printing!

Complex Shapes: What Can You Make?

3D Printing Can Make:

• Hollow parts with stuff inside
• Parts that look like nature (curves)
• Parts with thin walls

CNC Has Trouble With:

• Deep holes
• Inside corners
• Very complex shapes

Tip: If it looks like it grew in nature, 3D print it. If it looks like a block with holes, CNC it!

Hybrid Approach: Using Both

Smart companies use both methods:

1. 3D print a test part first
2. Make final parts with CNC
3. Use 3D printing for complex parts
4. Use CNC for strong parts

Example: A company makes drone parts. They 3D print the body (complex) and CNC machine the motor mounts (strong).

Industries Using These Tools

Aerospace:

• 3D printing: Air ducts, custom brackets
• CNC: Engine parts, wing components

Medical:

• 3D printing: Custom implants, models
• CNC machining: Surgical tools, implants

Automotive:

• 3D printing: Prototypes, custom dash parts
• CNC: Engine blocks, precision parts

Consumer Products:

• 3D printing: New product tests, toys
• CNC: Mass-produced parts, molds

Future Trends

3D Printing Future:

• Faster printing speeds
• More metal options
• Multi-color in one print

CNC Machining Future:

• Smart machines that fix mistakes
• Less waste
• Hybrid machines (3D print + CNC)

How To Decide Which Is Best For You

Ask these questions:

1. How many parts do you need?

• Just a few? → 3D printing
• Many? → CNC

1. What material do you need?

• Plastic? → Either works
• Metal? → CNC is better

1. How complex is your shape?

• Very complex? → 3D printing
• Simple? → CNC

1. How strong must it be?

• Super strong? → CNC
• Display only? → 3D printing

1. How exact must it be?

• Very exact? → CNC
• Close enough? → 3D printing

Quick Decision Guide

Choose 3D Printing when you need:

• Just a few parts
• Complex shapes
• Fast prototypes
• Less waste
• Low setup costs

Choose CNC Machining when you need:

• Lots of the same part
• Very exact sizes
• Strong parts
• Metal parts
• Smooth finish