AAMA and ASTM DXF Files: How to Prepare Patterns for a Clean 3D Sample

Most “the 3D sample looks wrong” problems start before anyone opens the 3D software. They come from the DXF export. To get a clean first 3D sample from existing patterns, export in AAMA or ASTM format rather than plain DXF. Know whether your grading travels inside the DXF or in a separate RUL file, and keep units, base size and seam allowance consistent with the 3D project. Clean up curves and outlines at the source. Then check the imported pieces against your spec before anyone judges the fit.

This article covers the file side of that handoff, whichever CAD system you export from: what AAMA and ASTM DXF files carry, what to fix before export, and what to check after import. It doesn’t repeat the software steps. For the click-by-click import, sewing and simulation walkthrough in Style3D Studio, follow our 2D to 3D pattern workflow guide, and use this checklist before and after it.

What a DXF pattern file actually contains

DXF is a general drawing-exchange format created by Autodesk for AutoCAD. On its own, a DXF is just lines and points. AAMA and ASTM are conventions that tell pattern software how to read those lines as apparel pattern pieces.

ASTM D6673, the ASTM practice for sewn-product pattern data interchange, uses one DXF block per pattern piece. It puts each kind of information on a numbered layer. For example:

Layer 1: piece boundary (the outline)
Layers 2 and 3: turn points and curve points
Layer 4: notches, with additional notch types such as T-, castle-, check- and U-notches on layers 80–83
Layer 5: grade reference lines
Layer 7: grain line
Layer 8: internal lines
Layer 13: drill holes
Layer 14: sew lines
Layer 15: annotation text

Grade rule tables travel as a separate ASCII text file.

Two details matter for 3D. First, ASTM D6673 was withdrawn by ASTM in 2019, but “ASTM” remains a common export option in pattern CAD, so you’ll still see and use it. Second, the standard explicitly does not describe relationships between pattern pieces or how 2D pieces correspond to 3D geometry. Your DXF tells the 3D software what each piece looks like. It does not say which edges sew together. Sewing is always defined on the 3D side.

AAMA vs ASTM DXF: which should you export?

Both formats use DXF as the container and share the same basic layer logic. The practical differences are in how strictly they’re defined and how grading is packaged.

	AAMA DXF	ASTM DXF
Status	The most widely used pattern DXF format	The successor to AAMA, more tightly standardized
Grading	Typically base-size outlines in the DXF, with grade rules in a separate .RUL file	Can carry grading in a rule file, or export all sizes inside the DXF
Notches and text	Basic notch types	Adds more notch types and supports descriptive text
Watch-outs	Not defined equally clearly on every point, so different CAD systems can interpret the same file differently	Not offered by every CAD system

The German pattern CAD vendor Grafis describes this in its own export documentation. It also notes a subtle grading risk: when a CAD system exports a base size plus grade rules, the receiving system rebuilds the other sizes with its own math. Those sizes, especially the extremes, can differ slightly from the original.

The practical rule is to use whichever of the two your source CAD writes most reliably and your 3D tool reads. Then test with one style before converting a whole library. Style3D Studio supports DXF in AAMA and ASTM formats. Its help center notes that only ASTM/AAMA exports are supported for import, and that the DXF format chosen at import must match the format the file was saved in.

Before you export: a source-side checklist

Fixing a problem in the pattern CAD takes minutes. Finding it later on a 3D avatar can cost a review round. Before exporting, check the following.

Units and scale. Know which unit the file was written in (mm, cm or inches) and set the same unit on import. A wrong unit produces a garment that’s ten times too large or too small. Worse, a mixed-up imperial/metric setting can produce one that’s only slightly off and looks plausible.

Closed outlines and standard layers. Every piece boundary should be a closed shape on the expected layer. Style3D’s first-project guide lists missing segments as a common import problem caused by unrecognized layers. Its fix is to check layer naming and make sure patterns are closed.

Curves. Some CAD exports write curves as splines, and some older CAD systems export only corner points. Style3D’s guide recommends converting spline curves to polylines before export if outlines come in distorted. Its DXF import options include settings for optimizing curve points and for reducing turn points on older corner-point exports.

Seam allowance convention. Decide whether the cut line or the sew line is your master outline, and write it down. If pieces arrive with seam allowance you didn’t expect, the fix is usually an import setting (Style3D has an “Import Seam Allowance” option) rather than redrawing.

Notches, grain lines and internal lines. These are what the 3D team will use to align and sew. Missing notches make sewing slower and less accurate. A flipped grain line changes how a fabric hangs in simulation. Style3D’s import options include reversing the grain line and copying cutting notches to the sewing line.

Piece names and text encoding. Use clear, consistent piece names. If names contain non-Latin characters, make sure the encoding is right on import. Style3D offers UTF-8, GBK and BIG5 options.

One style per file. Keep pieces from different styles out of the same export, unless you mean to load them into the same project.

Grading and size mapping: the step most teams skip

Grading is where a DXF that “imported fine” can still go wrong.

Know where your grading lives. If your CAD wrote an AAMA DXF plus a .RUL file, keep the pair together with matching file names. If the grading is embedded in the DXF, you only need the one file. Style3D’s import dialog lets you choose DXF or RUL as the grading rule source.

Match the size count. Style3D’s DXF documentation says a graded DXF must have the same number of sizes as the 3D project.

Understand base-size alignment. When the size names differ between the DXF and the 3D project, sizes are aligned on the base size. Style3D’s help center gives a clear example:

The project sizes are 160, 165, 170 (base) and 175.
The DXF sizes are S, M (base), L and XL.
M aligns to 170, so S, M and L map to 165, 170 and 175.
XL has no matching project size and isn’t imported.
Size 160 is filled from the nearest imported size, S.

If you don’t plan for this, you can end up reviewing a “size 160” that is really an S, or lose your largest size without noticing.

Decide whether the first sample needs grading at all. For a first fit check, many teams import the base size only, get it right, and bring in the full size run once the base is approved.

After import: what to check before anyone reviews fit

Run these checks on the imported pieces, before sewing and simulation:

Piece count. Every piece on the marker or cut list is present, including small ones like facings, pocket bags and loops.
One known measurement. Measure a dimension you know from the spec, such as the center back length or a waist seam, and compare it to the spec. This catches unit and scale errors immediately.
Seam lengths between joining edges. Compare the lengths of edges that will be sewn together. Unexpected differences point to export or curve problems, not fit problems.
Notches and grain lines. Confirm they’re present and pointing the right way on every piece.
Sizes. If you imported a size run, confirm which source size landed on which project size.
Seam allowance. Confirm it’s present or absent according to your convention.

Only then move on to arranging, sewing and simulating; the step-by-step 2D to 3D workflow covers those stages in Style3D Studio. Style3D’s first-project guide suggests a coarse simulation first (particle spacing around 15–20 mm) for a quick preview. Refine to 5–10 mm with precise simulation once the garment is sewn correctly. Judging fit on a coarse preview, or on pieces that failed the checks above, is how teams lose trust in 3D early.

Plan the round trip back to the pattern room

A 3D sample often leads to pattern changes. Decide up front where those changes are made:

Changes made in the 2D CAD keep the pattern maker’s system as the master. You re-export and re-import for the next 3D round.
Changes made in 3D need to come back out. Style3D Studio can export DXF, with options such as exporting the current size only, including seam allowance and choosing the format and encoding. Agree with the pattern room on the format and settings they need before the first export.

Whichever way you choose, write it into the workflow, so nobody ends up correcting two versions of the same pattern.

For a wider view of preparing CAD patterns for drape, including seam pairing and grain direction, see 3D draping from 2D CAD patterns. If your patterns come from open-source software, the Valentina DXF import guide covers that route specifically.

FAQ

What is an AAMA DXF file?

An AAMA DXF is a DXF drawing file that follows the AAMA convention for apparel patterns, with outlines, notches, grain lines and other details on defined layers. The base size is usually in the DXF, with grade rules in a separate .RUL file.

Is ASTM DXF better than AAMA DXF?

Neither is better in every case; ASTM is more tightly standardized and supports more notch types, but not every CAD system offers it. Use the format your source CAD exports most reliably, and test one style in your 3D tool before converting a library.

Do I need the RUL file?

You need it if your DXF holds only the base size and the grading was exported to a separate rule file. Without it, you’ll get the base size but not the graded sizes. If your export embeds all sizes in the DXF, there’s no separate RUL to bring along.

Why does my imported pattern have the wrong size or scale?

It’s almost always a unit mismatch between the export and the import settings. Check the unit the file was written in, set the same unit on import, and confirm by measuring one known dimension against the spec.

Can a DXF tell the 3D software how pieces sew together?

No. AAMA and ASTM DXF files describe each pattern piece, but the ASTM practice explicitly doesn’t define how pieces relate to each other or to 3D geometry. Sewing is set up in the 3D software, using notches and matching edge lengths as guides.

References

Style3D Team