How to Prepare Part Files for AM Service Bureaus

What Makes Files Print-Ready

Service bureaus receive hundreds of CAD files each week. Most come with hidden issues that slow quoting and production. The files may open correctly on a desktop, but they lack the structural data that metal or polymer printers require.

AM file preparation is the bridge between a designer’s intent and a machine-ready model. It turns a raw CAD file into a set of documents that answer three questions. What process fits this part? What tolerances must hold? What post-processing is needed?

When files are incomplete, the bureau must guess. Guessing creates quote variance and delays. A clean file removes that uncertainty.

Prerequisites Before You Start

Check these items before opening your CAD software.

• Confirm the design intent. Are the part’s critical dimensions marked?
• Identify the target material. Is it a specific alloy or a polymer grade?
• Note the intended use. Is the part a tool, a fixture, or a production part?
• Gather any previous test data. Do you have photos or reports from earlier iterations?
• Confirm the quantity. Even a small batch changes the economics.

These items form the baseline for every file you send. Without them, the bureau must ask questions. Each question adds days to the lead time.

Step One: Clean Geometry and Remove Artifacts

Open the CAD file and inspect the model. Delete sketch lines, construction geometry, and unused bodies. Merge duplicate faces. Remove tiny gaps and self-intersections.

Why this matters. Print software reads surfaces, not sketches. A hidden sketch line can confuse the slicer. A self-intersecting face can cause the printer to skip a region.

Use the CAD program’s repair tools first. If the software cannot fix the model, export it and use a mesh repair tool. Check the model at multiple zoom levels. Look for thin walls that may be below the process limit.

Step Two: Define Tolerances and Critical Features

Mark every dimension that must hold. Use your CAD software’s tolerance annotation feature. If the software does not support it, create a separate drawing with notes.

Why this matters. AM processes have inherent tolerances. A metal part may vary by a few hundredths of a millimeter. If your design expects tighter control, the bureau must know.

List the critical features. Include holes, threads, flat surfaces, and mating interfaces. State the tolerance for each. If a feature can be post-processed, say so. If it cannot, flag it.

Step Three: Select the Right Process

Match the part to a process. Choose between powder bed fusion, direct energy deposition, stereolithography, or other methods. Consider the material, the geometry, and the quantity.

Why this matters. Different processes have different strengths. A complex lattice works well in powder bed fusion. A small, high-detail part may need stereolithography. A large structural part may need direct energy deposition.

If you are unsure, state the design intent clearly. The bureau can recommend a process. But you must provide enough context to make that recommendation.

Step Four: Specify Material and Finish

Name the material exactly. Do not just say “aluminum.” Specify the alloy or polymer grade if you have one. If you do not, state the desired properties.

Why this matters. Material choice affects strength, finish, and cost. A 7075 aluminum part behaves differently from a 6061 part. A nylon part with glass filler has different stiffness than pure nylon.

Also specify the finish. Do you need as-printed, sandblasted, or machined? State the surface finish requirements. This affects post-processing and lead time.

Step Five: Add Design Intent Notes

Write a short note that explains the part’s function. Describe how it fits into the assembly. Note any stress points or thermal zones.

Why this matters. A file is not just geometry. It is also context. A note that says “this bracket holds a motor” gives the bureau a reference point. It helps them anticipate failure modes and suggest design changes.

Keep the note short. Three to five sentences are enough. Avoid marketing language. State the facts.

Step Six: Prepare the AM Submission Checklist

Use a checklist to verify your files before sending. This AM submission checklist covers the items above and a few more.

Item	Status
Geometry cleaned and repaired
Tolerances defined on critical features
Process selected and justified
Material specified by grade or property
Finish and post-processing noted
Quantity and lead time stated
Design intent summary written

A blank checklist is a weak file. A filled checklist is a strong file. The bureau can see that you have thought through the key issues.

Step Seven: Run a Quick Simulation or Check

If your CAD software supports it, run a basic simulation. Check for weak points, thin sections, or unsupported geometry. If you do not have simulation tools, use the bureau’s design review service.

Why this matters. A quick check can catch issues that a visual inspection misses. For example, a thin wall may be below the minimum thickness for the chosen process. A simulation can reveal that.

Do not over-engineer this step. A full simulation is not needed for every file. A basic check is enough.

Step Eight: Package and Send the Files

Create a single folder for the part. Include the CAD file, the drawing with tolerances, the checklist, and the design intent note. Compress the folder. Name it clearly.

Why this matters. A clear package makes it easy for the bureau to find what they need. A file named “final_v3_really_final.dwg” creates confusion. A file named “bracket_7075_final.step” is clear.

Send the files with a short email. State the part name, the quantity, and your target lead time. Ask for a quote within a specific timeframe.

Common Mistakes That Slow Down Quotes

• Sending a file without material specifications. The bureau must guess the alloy.
• Leaving tolerances undefined. The bureau must use default values.
• Forgetting to state the quantity. A single part and a batch of ten have different prices.
• Sending multiple versions of the same file. The bureau does not know which is final.
• Not marking critical features. The bureau may miss a tolerance requirement.
• Omitting post-processing needs. The bureau may quote a base price that is too low.

Each mistake adds a round of questions. Each round takes time.

Final Verification Step

Before you send the files, do a final check. Open the CAD file one more time. Confirm that the geometry is clean. Confirm that the tolerances are marked. Confirm that the material is specified.

Read the design intent note. Does it explain the part’s function? Does it mention any critical features?

Check the AM submission checklist. Is every item filled? If an item is blank, fix it before sending.

A final verification step takes five minutes. It prevents a two-week delay.

How Clear Files Affect Lead Time

Clear files do not just save time. They change the lead time itself. When the bureau has all the information it needs, it can quote quickly. A quick quote means a quick start. A quick start means a shorter lead time.

This is especially true for complex metal parts. A complex part may have many design questions. If the file is clear, those questions are answered before the bureau starts. If the file is unclear, the bureau must stop and ask. Each stop costs time.

What to Expect After Submission

After you send the files, the bureau will review them. They may ask questions. They will provide a quote. The quote will include the process, the material, the finish, and the lead time.

If the quote does not match your expectations, review the assumptions. Check the process selection. Check the material grade. Check the finish. Adjust the file or the notes and resubmit.

A clear AM file preparation process makes this iteration faster. You know exactly what was wrong. You fix it. You resubmit. The cycle repeats.

When to Use a Bureau Design Review

If your part is new or complex, use a bureau design review service. The bureau will check the file for printability and suggest changes. They may flag thin walls, unsupported geometry, or tight tolerances.

This service costs money, but it saves more. A design review caught early prevents a failed print. A failed print costs time, money, and lead time.

Use the design review for parts that are critical. Do not use it for simple parts that have been printed before.

How to Handle Revisions

If the bureau requests changes, make them quickly. Send the updated file within one business day. State the changes in the email. Update the checklist.

Do not send multiple versions without explanation. Each version should be clearly labeled. The bureau should know exactly what changed.

Revisions are normal. They are part of the process. A clear file makes revisions easier.

Final Thoughts

AM file preparation is not a one-time task. It is a habit. Build it into your design process. Check your files before you send them. Use a checklist. Keep your notes short and specific.

A print-ready file is not just a CAD file. It is a package of information that answers the bureau’s questions. It includes geometry, tolerances, material, process, and intent.

When you send a complete file, the bureau can quote quickly. A quick quote means a faster lead time. A faster lead time means a shorter path to your finished part.