Two Processes for Different Production Problems
SLS and injection molding can both produce polymer parts, but they solve different production problems. SLS builds parts from powder without tooling, which makes it strong for prototypes, complex geometry, customization, and low-volume production. Injection molding uses a mold, which makes it powerful when thousands of identical parts are needed.
Two Processes for Different Production Problems
SLS and injection molding can both produce polymer parts, but they solve different production problems. SLS builds parts from powder without tooling, which makes it strong for prototypes, complex geometry, customization, and low-volume production. Injection molding uses a mold, which makes it powerful when thousands of identical parts are needed.
The best choice depends on quantity, geometry, material, surface finish, tolerance, lead time, and tooling budget. A fair comparison includes total cost and schedule, not only unit price.
Where SLS Wins
SLS wins when the design is changing, the quantity is low, the geometry is complex, or tooling would delay the project. It can produce nylon parts quickly, nest many parts in one build, and avoid conventional support marks.
It is especially useful for bridge production, replacement parts, functional prototypes, and products with many variants. If a company needs 50 or 500 parts before tooling is ready, SLS can keep the project moving.
Where Injection Molding Wins
Injection molding wins when demand is high and the design is stable. The mold is expensive and slower to create, but each molded part can become very inexpensive at scale. Surface finish, material options, and repeatability can also be excellent once tooling is dialed in.
Molding is usually the better long-term production process for simple plastic parts sold in high volume. The higher up-front tooling cost is spread across many parts.
Cost Crossover
The crossover point depends on part size, mold cost, material, finishing, labor, and order size. 3D printing often wins early because there is little or no tooling cost. Injection molding often wins later because per-part cost drops once the mold exists.
Formlabs and Protolabs both frame the decision around volume, lead time, tooling cost, and production requirements. For many businesses, the strongest path is SLS for prototypes and bridge production, then injection molding after the design and demand are proven.
Design Differences
SLS allows undercuts, internal geometry, part consolidation, and design changes without mold updates. Injection molding requires draft, gate planning, ejection, wall-thickness discipline, and moldability. A part designed for SLS is not automatically a good molded part.
If molding is the eventual goal, design with molding constraints early. Use SLS to test fit and function, but do not let additive-only geometry creep into a part that must later be molded.
Practical Decision Guide
Use SLS when speed, complexity, customization, or low quantity matters. Use injection molding when high volume, stable geometry, polished finish, and low per-unit cost matter. Use both when a product needs testing and early sales before full production tooling.
The smartest manufacturing plan often moves through stages: SLS prototype, SLS pilot batch, molded production. Each stage answers a different business question.
FAQ
Is SLS cheaper than injection molding?
SLS is often cheaper for prototypes and low volumes. Injection molding is usually cheaper per part at high volumes after tooling is paid for.
Can SLS replace injection molding?
For low-volume or complex parts, yes in some cases. For many high-volume products, injection molding remains better.
Can I use SLS before injection molding?
Yes. SLS is useful for testing fit, demand, and function before investing in tooling.
