Checklist: Choosing a Resin Service Bureau
This audit checklist helps buyers evaluate a resin service bureau by reviewing material specifications, post-processing capabilities, quality control, and documentation. Use it to compare providers on objective criteria before sending production data.
- Verify the specific resin material grade and supplier before approving a quote, not just the generic material name.
- Confirm post-processing steps, including washing, curing, and finishing, are included in the scope and lead time.
- Request sample documentation such as material test reports and inspection reports for the first production run.
- Check the dispute process and warranty terms for dimensional or material defects in the agreement.
- Compare total landed cost, including tooling, post-processing, and logistics, against the per-part price.
Why a Generic Quote Is Not Enough
A quote showing a per-part price for a resin print misses most of the real cost. The final part depends on the exact resin grade, the washing and curing method, the post-processing, and the inspection report.
A resin service bureau may offer ten different resins under the same material family. Each grade has a different flexibility, heat resistance, and surface finish. Without the grade name, the quote is vague.
This checklist covers the main items to verify. It is not a contract. It is a working audit list for the first conversation with a potential provider.
1. Material Grade and Specification
The first section of the checklist covers the resin itself. A service bureau should name the resin by its commercial name or material code. A generic label like “tough resin” or “engineering resin” is not enough for a production part.
Ask for the data sheet or the supplier specification. The document should list the tensile strength, flexural modulus, heat deflection temperature, and chemical resistance. These numbers vary by grade and by the cure cycle.
Check the shelf life of the resin stock. Resin is a chemical mixture. It changes after opening. A provider that mixes small batches frequently may have older material on the shelf. Ask how they track batch numbers and how long the material stays on the shelf before use.
2. Machine and Process Details
The machine type affects the final part. A resin machine with a different light source, layer height, or build volume can produce different surface textures and mechanical properties.
Ask the provider to identify the machine model and the build volume. If the part is large, confirm the machine can hold it without splitting the model. Splitting the model and bonding the halves adds a visible seam and a mechanical weakness.
Ask about the layer height used for the part. A thicker layer is faster and cheaper. It is also rougher. A thinner layer is smoother and stronger, but it takes more time. The quote should state the layer height or the expected surface finish.
3. Post-Processing and Finishing
Resin printing is a green process. The part comes off the build plate soft, sticky, and unsuitable for assembly. Post-processing is a separate step. It is where the real cost and risk live.
The standard steps for resin are washing, drying, and UV curing. The washing solvent changes by resin type. Some resins use isopropyl alcohol. Others use a dedicated detergent. Ask which solvent is used and how the part is dried.
Ask about curing. Some providers cure the part in a UV oven for a set number of hours. Others cure it in a controlled chamber. Ask for the cure time and the light intensity if available. The cure cycle affects the final hardness and chemical resistance.
If the part needs a finish, ask how it is done. Sanding is common. Polishing is more expensive. Coating is another option. Ask if the finish is included in the quote or billed separately.
4. Quality Control and Inspection
A service bureau should have a documented quality control process. This is not optional. The process should cover incoming material, machine calibration, and outgoing part inspection.
Ask for the inspection report. It should include the part number, the material grade, the machine ID, the post-processing steps, and the inspection date. It should also include the measured dimensions of critical features.
Ask how they measure. Calipers are standard for simple parts. A coordinate measuring machine is better for complex geometry. A CMM is expensive. Most bureaus rent one or use it on a shared basis. Ask if the CMM is owned or rented and how often it is calibrated.
Ask about the first article inspection. This is the inspection of the first part after setup. If the first part fails, the provider should stop the run and investigate. Ask what their stop rule is and who decides when to stop.
5. Documentation and Traceability
Traceability is the ability to find the history of a part. If a part fails in the field, you need to know the material batch, the machine, the cure cycle, and the inspector.
Ask for the material batch number on the inspection report. Ask for the machine ID. Ask for the cure log. These documents are simple to produce and hard to fake.
Ask about the data retention period. How long do they keep the inspection reports and the machine logs? Some bureaus keep them for two years. Others keep them for seven years. The period depends on the industry and the customer requirement.
6. Lead Time and Capacity
The lead time includes more than print time. It includes design review, file preparation, washing, curing, inspection, and shipping. A provider that quotes five days for a small part may be underestimating the post-processing time.
Ask for a breakdown of the lead time. Ask how many parts they print per day. Ask what happens if a part fails during inspection. A provider with a clear backup plan will tell you. A provider that guesses will not.
Ask about capacity. If you need 500 parts per month, ask if they can handle it. Ask if they have a second machine or a second shift. Ask what their maximum order size is.
7. Pricing and Total Cost of Ownership
The per-part price is not the total cost. The total cost includes the design review, the post-processing, the inspection, the shipping, and the risk of failure.
Ask for a detailed quote. It should list the print cost, the post-processing cost, the inspection cost, and the shipping cost. Ask if there is a minimum order size. Ask if there is a setup fee.
Ask about the cost of a failed part. If a part fails, do you pay for the material? Do you pay for the post-processing? Do you get a credit? The answer varies by provider.
Red Flags to Watch For
The following items are red flags. They do not guarantee a bad provider, but they warrant more scrutiny.
- The provider will not name the resin grade. They will only say “engineering resin.”
- The quote does not include post-processing or inspection.
- The provider does not have a written dispute process.
- The inspection report does not include the material batch number.
- The lead time is too short for the post-processing steps.
- The provider does not have a second machine or a second shift.
- The provider does not keep machine logs or cure logs.
Comparison Table
Use this table to compare two or three providers side by side. Fill in the answers after the first conversation.
| Criteria | Provider A | Provider B |
|---|---|---|
| Resin grade name | ||
| Layer height | ||
| Post-processing included | ||
| Inspection method | ||
| Lead time breakdown | ||
| Material batch tracking | ||
| Dispute process |
Final Step: Request a Sample
The checklist is a conversation tool. It is not a guarantee. The final step is to request a sample. Send a small part with one or two critical dimensions. Ask the provider to print it, post-process it, and send an inspection report.
Compare the sample to the part you need. Check the surface finish. Check the dimensions. Check the material properties if you have a test method.
If the sample passes, move to a small production run. If the sample fails, ask the provider for a corrective action. Do not send the full production data until the sample is approved.
Frequently asked questions
Do I need a CMM for every part?
No. Calipers are sufficient for simple parts. A CMM is useful for complex geometry or for parts with tight tolerances. The inspection method should match the part criticality.
How long should a provider keep machine logs?
There is no single rule. Many providers keep logs for two to seven years. Ask for the retention period in writing. The period should match your industry requirement.
Can I use my own resin?
Some providers allow it. Most do not. Using your own resin shifts the material risk to you. Ask about the policy before sending data.
What is the most common cause of a resin print failure?
Inadequate washing or curing is the most common cause. The part is soft, sticky, or dimensionally unstable. Ask the provider for the cure cycle and the wash solvent.
Should I include post-processing in the quote?
Yes. A quote that excludes post-processing is incomplete. The final price should include washing, curing, and finishing. Ask for a detailed breakdown.
