Selective Laser Sintering: Good and Bad Things

What is SLS?

SLS is a way to make things. A laser hits powder. The powder gets hot and sticks together. This makes a 3D part.
SLS makes parts for planes, cars, and doctor tools. It is good for some things but not all things.

7 Good Things About SLS

1. Makes Hard Shapes With No Help

SLS can make hard shapes that other ways can’t.

• Make funny shapes
• Make holes inside
• Make parts in parts

BMW uses SLS to make car parts with cooling holes inside. That is very cool!

2. Faster Making With Lots of Parts

You can put many parts in the SLS box at one time.

• Make 20 parts at once
• Make parts in 1-3 days
• Faster than old ways

SLS makes things 48 mm each hour. NASA makes space parts 40% faster with SLS than old ways.

3. Many Types of Stuff to Use

You can use many materials in SLS:

• PA 12 (like strong plastic)
• TPU (like rubber)
• PEEK (for hot places)

Airbus uses SLS with carbon plastic for plane parts. It costs 30% less than metal parts!

4. Uses Left-Over Powder Again

SLS is nice to Earth. You can use 70-80% of the left-over powder again.
One company saves $12,000 each year by using old powder again.
Let’s look at how FDM makes more trash than SLS.

5. Makes Parts You Can Really Use

SLS makes strong parts that work like real parts.

• As strong as shot-in-mold parts
• Good for testing
• Good for using

6. No Wait Time After Making

When SLS parts cool down, they are ready to use.
Other ways like SLA need more steps after making. SLS does not.

7. Faster Than Old Ways

SLS is faster than traditional machining.

• Make big parts in 1-3 days
• Make small parts in hours
• Change plans fast

5 Bad Things About SLS

1. Rough Parts Need Fixing

SLS parts have bumpy skin.

• Feel like sand paper
• Need smoothing after
• Not as nice as 5 axis machining

SLS parts have a Ra 10–15 μm feel. That’s not smooth!

2. Not Many Material Choices

You can’t use all materials with SLS.

• Mostly plastics
• Need other machines for metals
• Cost more than CNC milling

Metal SLS costs $200K+ for the machine.

3. Costs Lots of Money and Power

SLS is not cheap.

• Machines cost $200,000+
• Uses 15-25 kWh per kg
• More power than other ways

The Fraunhofer Institute says SLS makes 30% more CO2 than old ways for small jobs.

4. Powder Gets Stuck Inside

If you make hollow parts, the powder gets stuck inside.

• Need drain holes
• Can’t make all shapes
• Need good design rules

5. Not the Same Strength All Ways

SLS parts are weaker in the up-down way.

• Less strong up and down
• Not as exact as CNC
• Can be off by ±0.3mm

What to Think About Before Using SLS

Design Rules for SLS

• Walls must be 1mm+ thick
• Make holes to let powder out
• Know the limits

When Does Cost Make Sense?

SLS is good for:

• 1-100 parts
• Hard shapes
• When time matters

SLS is bad for:

• 1000+ parts
• Big parts
• Simple shapes

Which Material is Best?

Pick the right stuff:

• PA 12 for strong parts
• TPU for bendy parts
• PEEK for hot places

SLS vs. Other Ways

Real Uses for SLS

Doctor Tools

Stryker makes bone parts with SLS. Their parts are 20% lighter than metal and help people get better 25% faster.

Plane Parts

Lockheed Martin uses SLS for fuel tubes in space things. They can take 250°C heat and are 60% lighter than metal.

Car Parts

BMW uses SLS to make tools for making cars. They save time and money.

Should You Use SLS?

Use SLS when:

• You need hard shapes
• You need working parts
• You need 1-100 parts fast

Don’t use SLS when:

• You need very smooth parts
• You have a small money bag
• You need lots and lots of parts

Questions People Ask

What’s Next for SLS?

New cheaper SLS machines like Sinterit are coming. They will make SLS less expensive and more people can use it.
SLS is not perfect but it’s very good for making hard shapes fast. It sits between prototype CNC machining and making lots of parts with molds.
Think about what you need before picking SLS!