Comparison: Selecting a Metal vs Polymer AM Bureau
Selecting between a metal and polymer AM service bureau depends on part function, material performance, and production scale. Evaluate process compatibility, material certifications, and post-processing capabilities before committing to a single partner.
- Match the service bureau to the part function, not just the material.
- Metal bureaus handle higher thermal loads and structural loads but require tighter post-processing.
- Polymer bureaus offer faster turnaround and lower cost for functional prototypes and low-volume production.
- Verify material certifications and post-processing capabilities before committing to a single partner.
- Hybrid sourcing is common when a single bureau cannot cover all process and material needs.
Start with the part function, not the material
The first decision in selecting a service bureau is not the machine. It is the part. A bracket that holds a motor under vibration needs different material properties than a gear that meshes under load. A medical implant needs biocompatibility and surface finish. A drone frame needs stiffness-to-weight ratio. Before contacting any bureau, define the load, thermal, chemical, and surface requirements. Write them down. Send them with the first RFQ.
This step prevents the most common mistake in AM sourcing. Buyers send a STEP file and ask for a quote. The bureau returns a price based on a default material. The part fails in the field. The buyer blames the bureau. The real failure was in the specification.
Metal versus polymer service bureaus: core differences
Metal service bureaus typically run powder bed fusion, electron beam melting, or laser-based processes. They handle steel, titanium, aluminum, nickel, and cobalt alloys. The parts are dense, strong, and heat resistant. They also require more post-processing. Sintering, stress relief, heat treatment, machining, and surface finishing are standard steps. Lead times are longer. Costs are higher.
Polymer service bureaus run SLS, MJF, DLP, SLA, and FDM. Materials include nylon, carbon-filled nylon, glass-filled nylon, TPU, and engineering resins. Parts are lighter, cheaper, and faster to produce. Post-processing is simpler. Washing, curing, and sometimes surface coating. Lead times are shorter. Costs are lower.
The difference is not just in the material. It is in the entire service chain. A metal bureau must manage powder recovery, screen quality, heat treatment, and dimensional stability. A polymer bureau must manage resin quality, layer adhesion, shrinkage compensation, and surface texture.
Comparison of service bureau types
| Option | Best for | Limitations |
| Metal AM service bureau | Structural parts, high-heat applications, medical implants, aerospace components | Higher cost, longer lead times, complex post-processing, limited material palette |
| Polymer AM service bureau | Functional prototypes, low-volume production, lightweight parts, rapid iteration | Lower thermal resistance, lower stiffness, limited material certifications, surface roughness |
| Hybrid service bureau | Mixed material portfolios, simultaneous metal and polymer parts | Higher coordination cost, potential for communication gaps, less specialization per material |
| In-house AM with outsourced post-processing | High-volume production, IP control, rapid iteration | High capital cost, material certification burden, post-processing bottleneck |
| Multi-process polymer bureau | Design iteration, surface finish requirements, resin-specific applications | No metal capability, limited structural loads, resin shelf life management |
When to pick a metal service bureau
Choose a metal service bureau when the part must survive thermal cycling, high mechanical load, or corrosive environments. Titanium for surgical implants. Steel for automotive brackets. Aluminum for aerospace brackets. These materials have established property data. The bureau should be able to provide material certifications, heat treatment records, and dimensional inspection reports.
The service chain matters. Metal parts usually require stress relief. Without it, the part will warp in the field. The bureau should list the stress relief temperature and duration in the quote. If they do not, ask.
Metal bureaus also handle powder quality. They should screen powder regularly and test for contamination. A single contaminated batch can ruin an entire build. Ask how they track powder batches and how long they store it.
Do not choose a metal bureau for a low-volume prototype that does not need high strength. The cost and lead time will not justify the material. A polymer part may meet the function at a fraction of the cost and in half the time.
When to pick a polymer service bureau
Choose a polymer service bureau when the part is a functional prototype, a low-volume production part, or a lightweight component. Nylon, carbon-filled nylon, and glass-filled nylon handle moderate loads and good stiffness. TPU handles flex. Resins handle surface finish and detail.
The service chain is simpler but not trivial. SLS parts require washing and curing. Resin parts require washing and UV curing. Shrinkage compensation matters. If the bureau does not apply shrinkage compensation, the part will be out of tolerance. Ask for the tolerance spec before you send the file.
Polymer bureaus also manage material certifications. For medical or automotive use, the resin or powder must have traceability. Ask for the material data sheet and the certificate of analysis. For high-volume production, ask about lot-to-lot consistency.
Do not choose a polymer bureau for a part that must withstand sustained high heat. The material will creep. The part will fail. If the operating temperature exceeds the heat deflection temperature of the polymer, move to metal.
Process selection and material choice
The process determines the part orientation, surface finish, and mechanical properties. Laser powder bed fusion for metal produces isotropic properties in the build direction. Electron beam melting can handle reactive materials. SLS for nylon produces good isotropy and high surface area. MJF produces faster build times and better surface finish. DLP and SLA produce high detail but limited layer height.
Material choice is constrained by the process. Metal powder is process-specific. Aluminum powder for metal AM is not the same as aluminum powder for injection molding. Nylon powder for SLS is not the same as nylon powder for FDM. The bureau must specify the exact material grade and the process used.
Ask for the part number of the material. Ask for the supplier. Ask for the heat treatment if applicable. These details separate a serious bureau from a reseller.
Post-processing and inspection
Post-processing is where the part becomes reliable. Metal parts need stress relief, machining, and surface finishing. Polymer parts need washing, curing, and sometimes coating. The bureau should list these steps in the quote. If they do not, assume they are not included.
Inspection matters. Ask for the inspection method. CT scan, dimensional metrology, or visual inspection. For critical parts, ask for a first article inspection report. For production, ask for in-process checks.
The service bureau should have a quality system. They should track builds, powders, resins, and post-processing steps. They should be able to provide a traceability report. Without traceability, a field failure is a mystery. With traceability, it is a data point.
Cost, lead time, and hybrid sourcing
Metal AM costs more than polymer AM. Lead times are longer. A metal part may take two to four weeks. A polymer part may take one to two weeks. The cost difference is driven by material, machine time, post-processing, and quality control.
Many buyers use a hybrid approach. They source prototypes and low-volume parts from a polymer bureau. They source production and high-load parts from a metal bureau. This keeps costs low and lead times short. The coordination cost is real. One buyer must manage two suppliers. The communication load is higher. But the benefit is flexibility.
Do not force all parts through one bureau. If the bureau is strong in metal but weak in polymer, or vice versa, the fit is poor. A hybrid approach is common in mature AM programs.
Verification checklist for service bureaus
Before signing, run the following checks.
- Ask for the material data sheet and the certificate of analysis.
- Ask for the post-processing steps and the heat treatment details if applicable.
- Ask for the tolerance spec and the inspection method.
- Ask for the traceability report.
- Ask for the quality system and the audit report.
- Ask for the lead time and the cost breakdown.
- Ask for references from similar applications.
These checks take time. They prevent field failures. They save money. They build a reliable supply chain.
Final selection criteria
The correct service bureau is the one that matches the part function, the material performance, and the production scale. A metal bureau is the right partner for high-load, high-heat, and critical parts. A polymer bureau is the right partner for prototypes, low-volume production, and lightweight parts. A hybrid approach is the right partner for mixed portfolios.
The buyer must define the requirements first. The bureau must match those requirements. The specification is the contract. The part is the result. The service bureau is the tool. Choose the tool for the job.
Frequently asked questions
Can I use the same service bureau for both metal and polymer parts?
Some bureaus offer both. Many specialize in one. If you need both, verify that the bureau has separate quality systems and material traceability for each.
What is the main difference in post-processing between metal and polymer AM?
Metal parts require stress relief, machining, and surface finishing. Polymer parts require washing, curing, and sometimes coating. The metal chain is longer and more costly.
How do I know if a polymer part will fail in the field?
Check the operating temperature against the heat deflection temperature of the material. Check the load against the tensile and fatigue data. Check the surface finish against the wear requirement.
What should I ask a metal service bureau about powder quality?
Ask how they screen powder, how often they test for contamination, and how they store powder batches. Ask for the powder supplier and the lot number.
Is in-house AM always better than outsourced AM for production?
No. In-house AM is better for IP control, rapid iteration, and high-volume production. Outsourced AM is better for low-volume, multi-process, or capital-constrained programs.
