Polymers vs Metals 3D Printing: Which Material Fits Your Part
This page compares high-performance polymers and metal alloys for additive manufacturing, with the numbers that matter on a shop floor. It is written for design engineers and buyers who need to pick a material before the print file is frozen. Read the table, run the four checks, and you will know which route to quote.
In this article
- 1
- 2
- 3
- 4
- 5
- 6
Polymers vs Metals 3D Printing: Quick Comparison
Typical ranges for engineering-grade additive parts. Your geometry and load path decide where you land.
| Factor | High-Performance Polymers | Metal Alloys |
|---|---|---|
| Tensile strength | 70–120 MPa (PEEK, PEI) | 300–1,100 MPa (Ti, Al, steel) |
| Density | 1.3–1.5 g/cm³ | 2.7 g/cm³ (Al), 4.4 g/cm³ (Ti) |
| Service temperature | 150–250 °C continuous | 300–600 °C depending on alloy |
| Achievable wall | 0.4–0.8 mm typical | 0.6–1.5 mm before distortion |
| Typical tolerance | ±0.1–0.3 mm (as-built) | ±0.05–0.2 mm on small features |
| Relative part cost | Low to medium | High, 3–10× the polymer route |
| Best-fit volumes | Prototypes up to a few thousand | Low tens to a few hundred |
| Lead time driver | Machine time dominates | Melt, stress relief and post-machining |
| Finishing need | Vapor smoothing, media blast | HIP, heat treat, support removal |
| Design freedom | Lattices, thin ribs, internal channels | Less flexible, support matters |
How High-Performance Polymers Behave in Additive Manufacturing
High-performance polymers are not one material. PEEK, PEI (Ultem), PPSU and PEKK each sit in a different corner of the temperature and chemical map. What ties them together is a semi-crystalline or amorphous backbone that keeps stiffness above 150 °C and resists fuels, hydraulic fluid and sterilization cycles. That is why polymers vs metals 3D printing decisions usually start with the service environment, not the load.
Printing these materials is a thermal job. PEEK needs a chamber near 200 °C and a nozzle around 400 °C, otherwise layers bond poorly and Z-strength drops. PEI runs cooler but is more brittle. When you see a polymer part split along layer lines, it is almost always a chamber temperature problem, not a material problem.
Geometry is where polymers win clearly. A 0.4 mm wall, a 0.3 mm lattice strut, a tortuous internal cooling channel: these print without support in most orientations. The same features in metal need support structures that must be cut away, and thin walls tend to warp during the melt. If your design has fine internal features, that alone can settle the choice.
The limit is load. A polymer part in a 2 kN static bracket may be fine. The same bracket under 2 kN of cyclic load at 120 °C will creep, and creep is silent. It does not crack, it just moves. Parts that must hold a dimension over thousands of cycles usually belong in metal.
- 1PEEKBest for chemical resistance, sterilization and 200 °C-plus service.
- 2PEI / UltemStiffer, cheaper, but brittle and sensitive to print orientation.
- 3PPSU and PEKKMiddle ground on temperature; good for fluid-handling parts.
- 4Carbon-filled gradesRaise stiffness 2–3× but cut elongation, so avoid snap fits.
What Metal 3D Printing Actually Delivers
Metal additive processes, mainly laser powder bed fusion, give you a part that behaves like wrought metal after the right heat treatment. Ti-6Al-4V, 316L stainless, AlSi10Mg and Inconel 718 are the workhorses. Tensile strength lands between 300 MPa and 1,100 MPa depending on alloy, and the part stays stable from -50 °C to well past 400 °C.
The catch is the process chain around the print. Supports must be removed, the part is usually stress-relieved, and critical faces are machined afterward. That is where tolerance comes from. A printed metal surface sits around Ra 10–15 μm and ±0.1–0.2 mm; a machined face can reach ±0.005 mm and Ra 0.2–0.8 μm. Treat the printer as a blank supplier, not a finishing machine.
Metal also wins on thermal conductivity and electrical grounding. If the part pulls heat away from electronics, or must carry a ground path, polymers cannot compete. Aluminium at roughly 150 W/m·K against PEEK at 0.25 W/m·K is not a close race.
Cost scales badly at volume for both processes, but metals start higher. Powder cost, inert atmosphere, support removal and heat treatment all add up. For a bracket the size of a hand, expect the metal route to cost several times the polymer route before you account for post-machining.
- 1Ti-6Al-4VHigh strength-to-weight, biocompatible, expensive powder.
- 2316L stainlessCorrosion resistance and ductility; good for fluid and food contact.
- 3AlSi10MgLight, good thermal path, lower strength than titanium.
- 4Inconel 718High-temperature and fatigue duty; hardest to finish.
Four Checks That Settle the Choice
Check one is temperature. Write down the highest continuous temperature the part sees, then add 30 °C for safety. Above 250 °C, polymers are out. Between 150 °C and 250 °C, PEEK or PEKK can work if loads are modest. Below 120 °C, most engineering polymers are comfortable.
Check two is load type. Static load is forgiving. Cyclic load, impact and anything with a safety factor requirement push you toward metal. A simple test: if a crack in the part would stop a machine or fail a certification, use metal even if polymer passes the static calculation.
Check three is feature size. Measure your smallest wall, strut or channel. Under 1 mm, polymer printing holds detail far better. Over 3 mm and mostly solid, metal becomes practical, because the support burden is manageable and the strength is real.
Check four is quantity and budget. Polymer printing stays economical from one part to a few thousand. Metal printing is usually a low-volume play: tens to a few hundred parts. Past that, both routes lose to CNC machining or injection molding, and that is the honest answer.
- 1Above 250 °CMetal only, unless the load is negligible.
- 2Safety-criticalMetal, or a machined part instead of printed.
- 3Sub-1 mm featuresPolymer wins on detail and cost.
- 4Over 500 partsCompare against CNC and molding before printing.
Where Each Material Wins, and Where It Does Not
Choose high-performance polymers for ducting, brackets under light load, jigs and fixtures, electrical housings, and medical instruments that go through autoclave cycles. They also win for anything with internal channels or lattice structure, because support removal is not a cost line.
Choose metal for load-bearing brackets, heat sinks, impellers, valve bodies and parts with a certified fatigue requirement. Titanium suits medical implants and aerospace hardware where weight matters. Stainless suits fluid and food-contact parts. Aluminium suits housings that need to dump heat.
Neither process is right for large flat panels, tight-tolerance mating features, or high-volume runs. Those go to sheet metal fabrication or CNC machining. A printed part that needs a ±0.02 mm bore is really a machined part with a printed blank, and it should be quoted that way.
One practical note on hybrids. Printing a near-net metal shape and then machining only the critical faces often costs less than machining from solid, especially for titanium and Inconel. It also cuts the lead time on hard alloys. Ask for both quotes before you commit.
- 1Polymer fitDucts, housings, fixtures, lattice parts, sub-1 mm features.
- 2Metal fitBrackets, heat paths, impellers, fatigue-rated hardware.
- 3NeitherFlat panels, tight bores, runs past a few hundred parts.
- 4HybridPrint near-net, then machine only the critical faces.
Cost, Lead Time and the Post-Processing Nobody Budgets For
Machine time drives polymer cost. A PEEK part with a 200 °C chamber prints slowly, and the chamber must cool in a controlled way or the part warps. You pay for that time, not for the material. Small brackets often land in the same range as a machined aluminium part, which surprises people.
Metal cost is dominated by powder, atmosphere and the post-print chain. Support removal on a complex part can take hours by hand. Heat treatment is a separate step. If the part needs a machined interface, add a second setup and a second inspection.
Both routes share one hidden cost: inspection. Printed parts have internal features you cannot see, so dimensional checks focus on the outside and on witness coupons. If your quality plan needs full dimensional reports, say so before quoting, because it changes the sampling plan.
Lead time is closer than most people expect. Polymer prints can ship in a few days. Metal prints need build time plus heat treat plus finishing, so allow extra days. When a project is schedule-driven, polymer is often chosen for the first article and metal for the production revision.
- 1Polymer cost driverChamber time and controlled cooling.
- 2Metal cost driverPowder, supports, heat treat, post-machining.
- 3Shared costInspection and any required dimensional report.
- 4Schedule playPolymer for first article, metal for the released revision.
The Short Answer
If the part runs below 150 °C, has fine internal features and ships in low volumes, choose high-performance polymers. If it carries cyclic load, moves heat, or sees above 250 °C, choose metal and plan for post-machining. When quantity climbs past a few hundred, quote CNC machining before you quote either.
Frequently Asked Questions
Can a PEEK part replace a machined aluminium bracket?
Sometimes, but only if the load is light and the temperature stays below about 150 °C. PEEK has roughly one third the tensile strength of 6061-T6 and creeps under sustained load.
The weight saving is real, since PEEK is about half the density of aluminium. Test the design under the real load profile before you commit a production run.
How much does metal 3D printing cost compared with polymers?
For a hand-sized bracket, the metal route typically runs several times the polymer route once you include support removal, heat treatment and any post-machining on critical faces.
The gap narrows at higher quantities for metal only if the geometry is hard to machine. For simple shapes, CNC from bar stock usually wins on price.
Which material holds tighter tolerances after printing?
As-built, both are loose: around ±0.1–0.3 mm for polymers and ±0.05–0.2 mm for metal on small features.
If you need ±0.005 mm, the part must be machined after printing regardless of material. Quote it as a printed blank plus a machining operation.
Are high-performance polymer parts safe for medical use?
PEEK and PEI both tolerate repeated steam sterilization and common disinfectants, which is why they appear in surgical instruments and fixtures.
Material choice alone does not make a part compliant. Cleaning validation, biocompatibility testing and process documentation are separate steps.
What is the largest polymer or metal part you can print?
Build envelopes vary by machine, and part size is often limited more by warping risk than by the envelope itself.
For large parts, send the 3D file and we will review orientation, support strategy and whether the part should be split and bonded.
When should we skip 3D printing entirely?
Skip it for flat panels, simple turned parts, tight bores, and any run past a few hundred units where the geometry suits machining or molding.
Printing earns its place on complex internal geometry, lattices, and low-volume parts that would otherwise need expensive tooling.
Send the File, Get a Material Recommendation
Upload your 3D model and we will tell you which route is cheaper for your geometry, quantity and temperature range, with a quotation and free DFM analysis within 12 hours.
Quotation in 12 hoursNo minimum order quantity100% inspection before shipment
More From GreatLight
We publish setup notes, tooling trials and inspection data from the factory floor.
