Overview#
Cutting a slot or logo that crosses a bend is impossible to model directly on the formed part. Unfold flattens selected bends in the timeline; you add sketches and cut features on the flat geometry; Refold returns the bends to their formed state. The cuts are carried round the bend correctly, because the work was done on the flat.
This is different from Create Flat Pattern, which produces a separate manufacturing view. Unfold/Refold is a modelling aid in the same body and timeline; the flat pattern is the deliverable.
Where to find it#
- Design > Sheet Metal > Modify > Unfold. Unfold mode activates, and Refold is on the Sheet Metal tab while the mode is active (Autodesk's help: "On the Sheet Metal tab, click Refold").
- Unfold is a mode: after OK the Unfold feature is added to the timeline and unfold mode stays active until you Refold, and the component returns to its folded state when you do.
Step by step#
- Select Unfold.
- Click a Stationary face, the face that stays put while the others flatten.
- Click the highlighted bends you want to unfold, or tick Select all bends to unfold every bend.
- Click OK. The model flattens; the timeline now has an Unfold feature, and unfold mode stays active.
- Create a sketch on the flat face. Draw the slot or text that will cross the bend lines.
- Use Extrude with the Cut operation through the thickness.
- Click Refold on the Sheet Metal tab. The component returns to its folded state and you leave unfold mode.
- Check that the cut wraps around the bends.
Options reference#
| Option | What it does | Notes/default |
|---|---|---|
| Stationary face | The face that does not move | Becomes the base of the flat |
| Bends to unfold | All or selected bends | Unfold only what you need for faster rebuilds |
| Select all bends | Unfolds every bend at once | Optional checkbox |
| Refold | Returns the component to the folded state | Features made while unfolded are kept |
| Timeline | Unfold feature, your features, then Refold | Do not insert unrelated features between them |
Tips and pitfalls#
Tip: Only unfold the bends you need. Fewer bends mean fewer chances of collision and faster recomputes.
Warning: Cuts that cross a bend stretch or compress the metal in reality. A pattern made by cutting across a bend on the flat will not be perfectly straight after bending; allow tolerance.
Warning: Do not forget Refold. If the timeline ends in an unfolded state, your downstream features, joints and the flat pattern may not behave as you expect.
Tip: Holes within about 2.5 times the thickness plus the bend radius from a bend distort when formed. Keep holes away from bends or add a relief slot.
Tip: If you only need a manufacturing view, skip Unfold and go straight to Create Flat Pattern.
Unfold versus Create Flat Pattern#
These two commands are often confused, and Autodesk's help is explicit that Unfold is not Flat pattern. The difference:
| Aspect | Unfold / Refold | Create Flat Pattern |
|---|---|---|
| Purpose | Modelling aid so you can add features across bends | Manufacturing deliverable |
| Location | Same body, same timeline; features are recorded between Unfold and Refold | A Flat Pattern node in the browser; a separate view |
| Reliefs | Kept consistent with the folded body so Refold works | Cut-ready geometry |
| Output | Nothing exported | DXF for the shop, drawings |
| Number allowed | Any number of Unfold/Refold pairs | One flat pattern per component |
Use Unfold when a feature must exist in the 3D model: a slot or logo cut across a bend, vent holes on both a flat and a flange, or holes near a bend that you want to locate on the flat. Use Create Flat Pattern when you only need a cutting file.
Which bends to unfold#
You are not obliged to unfold everything. Select only the bends between the stationary face and the faces you will edit. A U-channel with a 100 mm base and two 30 mm walls, where you want a slot across the base and one wall, needs only one bend unfolded, which keeps the model light and avoids collisions on the far wall. If a feature touches both walls, unfold both. Unfolding fewer bends also matters for rebuild speed on parts with many bends.
Choosing the stationary face#
The stationary face is the face that stays put. Choose the face that your sketch will lie on or a large flat face; the unfolded body extends from it. A poor choice, such as a small flange, is not wrong but places the sketch plane in an awkward orientation. The unfolded geometry is identical either way, only the position differs.
Worked example: a slot across a bend#
A 1.5 mm steel U-channel: 40 mm base, two 25 mm walls, 100 mm long, 1.5 mm inside radius, K-factor 0.35. You want a 6 mm wide slot starting 10 mm from the bend on the base and ending 10 mm up the wall, running along the length of the channel.
- Unfold only the bend between the base and the wall of interest.
- Calculate the flat distance from the bend line. The developed length of one 90 degree bend is 1.5708 x (1.5 + 0.35 x 1.5) = 1.5708 x 2.025, about 3.18 mm. Fusion does this for you, but knowing it lets you sanity-check.
- Sketch the slot as a 6 mm wide rectangle crossing the bend zone on the unfolded face. The slot extends 10 mm onto the base side and 10 mm onto the wall side of the bend; the flat distance is therefore 10 + 3.18 + 10 = 23.18 mm.
- Cut it with Extrude (Cut) through the thickness (all through, 1.5 mm).
- Click Refold.
When formed, the slot wraps around the bend, but the part of the slot in the bend zone distorts slightly: the slot width at the inside of the radius may differ by a few tenths of a millimetre. If the slot is a functional fit, add tolerance or avoid putting critical edges in the bend zone.
Dealing with timeline and rebuild issues#
- Do not leave the model unfolded. Check the timeline ends with Refold. If you see a feature after Unfold with no matching Refold, later features may be computed on the flat body.
- Features between the pair can be edited. Double-click your sketch or cut inside the pair to change it; the Refold updates.
- Parametric changes upstream. If you change a flange height upstream of the Unfold, the sketch plane may move; check the sketch is still correctly constrained to a face or origin plane. Constrain sketches to the stationary face's edges rather than to bend edges where possible.
- Several pairs. You can have more than one Unfold and Refold pair in a timeline, for example one for each side of a part.
Common failures and fixes#
| Symptom | Cause | Fix |
|---|---|---|
| Unfold fails | A bend or relief collides when flattened | Unfold fewer bends, or fix the corner relief |
| The slot is misaligned after Refold | Sketch constrained to bend geometry that moved | Constrain to flat faces or origin planes |
| Refold button is not visible | Not in unfold mode | Unfold again, or check the timeline |
| Flat pattern fails afterwards | Timeline ended in an unfolded state | Add Refold |
| Holes near the bend are elongated after forming | Hole too close to the bend | Keep holes at least 2.5 x thickness + radius away (about 5.25 mm for 1.5 mm material with a 1.5 mm radius) |
| Cuts are not through the whole thickness | Extrude extent too short | Use All or Through-all |
Editing and troubleshooting inside the unfolded state#
While unfold mode is active you can add anything that makes sense on a flat plate: holes, slots, extruded cuts, text. Autodesk's help notes that adding holes and extruded slots while the body is unfolded can make the part easier to manufacture, because the cut is dimensioned on flat metal. Two cautions apply. First, new features should not add flanges or bends while unfolded, because Refold expects the same bend set it unfolded. Second, a cut that crosses a bend zone is drawn on the flat but formed on a curved surface, so a rectangular cut becomes slightly wider or narrower at the inside of the bend. For a 90 degree bend in 1.5 mm material with a 1.5 mm radius, the inside surface is about 5 percent shorter than the neutral axis and the outside about 5 percent longer, which is where the few-tenths-of-a-millimetre distortion comes from.
A useful habit is to dimension unfolded sketches to the edges of the stationary face or to origin geometry, and never to the bend lines themselves. Bend lines move if you later change the radius, K-factor or thickness, and a sketch attached to them follows and may no longer fit the part. If a sketch appears to float after a rule change, the cause is almost always a dependency on a bend edge.
When Unfold itself fails, work through three checks. Does the model have an overlapping flange, such as two walls that touch in the folded state but would collide when flattened? Does a corner relief or miter gap give the flattened material somewhere to go? Is there a bend whose angle is greater than 180 degrees, as in a hem? Fix the first two with reliefs or a rip; for a hem, unfold only the bends you need and leave the hem folded.
Practice exercise#
Cut a slot across a bend and compare with the flat pattern.
- Make a U-channel with a contour flange: 40 mm base, two 25 mm walls, 100 mm long, 1.5 mm steel, 1.5 mm inside radius.
- Click Modify > Unfold. Pick the base as the stationary face and unfold only one bend (click it, do not tick Select all bends). Click OK.
- Sketch a 6 mm wide, 23 mm long rectangle across the bend line on the unfolded face, starting 10 mm before the bend line, and cut it through the thickness.
- Click Refold and confirm that the slot follows the bend.
- Edit the slot sketch: change the length to 30 mm, and confirm the model updates.
- Run Create Flat Pattern on the part, and compare the slot in the flat with the slot you sketched. Measure its length.
- Repeat with Select all bends unfolded and note the rebuild time difference on a more complex part if you have one.
Expected result: a slot that wraps around the bend, flat-pattern geometry that matches the unfolded sketch, and a clear understanding that Unfold is a modelling aid while the flat pattern is the manufacturing output.