Goal#
After this stage you can build and judge the curved shapes that make a product feel designed: soft shoulders, grips that fit a hand, flowing transitions between faces. You will create surfaces and turn them into solids, tell G0, G1 and G2 joints apart using Zebra and Curvature Comb analyses, sculpt a T-spline body in the Form workspace, and clean up and convert a mesh. By the end you will have designed an ergonomic handheld grip for the capstone device.
This matters for product design because people touch products. A grip that is a plain rounded rectangle will hurt after ten minutes, and a glossy surface with a kink in the reflection reads as cheap. Solid modelling gets you function; surface and Form modelling gets you comfort and character.
Licensing: Surface tools and the Form workspace are used throughout this stage. The guide could not confirm in Autodesk's help whether Form is included in every licence tier (including Personal use), so check Autodesk's current licence comparison before you start. Convert Mesh with the Organic method is part of the Design Extension and appears only under "Optional (extension required)" below.
Before you start#
- Stages 1 to 5: constrained sketches, extrude, revolve, loft, sweep, shell, fillet, parameters, and the DFM habits of Stage 5. The grip you build here has to be moulded or printed, so keep wall thickness and draft in mind.
- You can use the Inspect menu (Measure, Section Analysis) and can read the browser's body icons (solid versus surface).
- Comfortable orbiting and selecting hidden geometry. Surface and Form work needs more precise selection than prismatic work.
Learn#
Read in this order. Surfaces first (they are the foundation and give you the analysis tools), then Form, then mesh.
- Read Surface Workspace Overview - surface bodies, normals, free edges and the surface-to-solid worked example. Do not skip the section on free edges, you will use it constantly.
- Read Extend - extending past a boundary before trimming makes joins reliable. Focus on Natural versus Tangent.
- Read Patch - filling holes with a tangent or curvature-matched surface.
- Read Stitch and Unstitch - the free-edge count in the dialog is your main diagnostic tool.
- Read Continuity G0 to G3 - what the four levels mean and when each is appropriate for a consumer product.
- Read Curvature Analysis - Zebra, Curvature Comb, Curvature Map and Isocurve. Focus on how to read each result.
- Read Thicken and Solid From Surface - how a surface becomes a manufacturable wall.
- Read Form Workspace Overview - the cage, display modes and why the smooth surface sits inside the cage.
- Read Edit Form and Selection - Soft Modification and selecting by loop. Focus on the tips at the bottom.
- Read Symmetry and Patterns - mirror symmetry halves your work and keeps a grip balanced.
- Read Finish Form and Converting Between Form and BRep - when you are done sculpting and how to repair a failed finish.
Later in the stage, read these when you reach the mesh challenge: Mesh Workspace and Importing STL, OBJ and 3MF, Mesh Repair, Reduce and Remesh, and Converting a Mesh to BRep.
Practice#
- Do the practice exercise on Surface Workspace Overview (sketch to manufacturable solid).
- Do the practice exercise on Stitch and Unstitch (six faces with a small gap, then read the free-edge count).
- Do the practice exercise on Continuity G0 to G3 (compare a G1 joint and a Patch with curvature continuity using Curvature Comb).
- Do the practice exercise on Form Workspace Overview (sphere, rows versus single vertices, Finish Form, Zebra).
- Do the petal exercise on Symmetry and Patterns (circular internal symmetry on a 5-face cylinder).
- Drill 1 (15 min): reading Zebra. Make a box with a 6 mm fillet on one edge and a 6 mm chamfer on another. Run Zebra Analysis in both stripe directions. Write one sentence on how a chamfer, a G1 fillet and a Patch with curvature continuity each look in the stripes.
- Drill 2 (15 min): cage density. Make a Form Box 60 x 40 x 20 mm with 3 x 3 x 2 faces. Pull the top face up by 6 mm. Then Subdivide that face and pull again. Compare the shape and note how the smooth surface relates to the cage in Control Frame display.
- Drill 3 (10 min): free edges. Stitch five faces of a box and read the free-edge count (it should be four). Add the sixth face and confirm zero free edges and a solid volume.
- Drill 4 (20 min): shrinkage check. Create a Form Box 50 mm wide. Finish it. Measure the solid width. Reopen the Form and scale the outer cage so the finished width is within 0.5 mm of 50 mm.
Checkpoint project#
Design an ergonomic handheld grip. Estimated time: 5 to 7 hours. There is no matching tutorial, so this is a full brief.
Brief. The capstone device from Stage 5 (an electronics enclosure) needs a hand grip for one-handed use. The grip clips to the underside of the enclosure and must be comfortable for a range of hand sizes, easy to print, and symmetric for left and right-handed users.
Constraints. These are typical ergonomic starting values, not standards; if you can, check them on a real hand.
- Overall grip length 115 mm (room for a hand breadth of roughly 85 to 95 mm plus margin).
- Oval cross-section at mid-length about 38 mm wide by 30 mm deep (area of an ellipse = pi/4 x 38 x 30, about 895 mm squared, perimeter about 107 mm, which is in the comfortable range for a handle).
- Tapers to about 34 x 26 mm at the bottom end (bottom taper stops the grip slipping out of the palm) and 42 x 32 mm at the top where it meets the enclosure.
- Three shallow finger grooves on the front, about 2 mm deep, spaced about 22 mm apart, and a thumb rest on each side. No sharp edges: minimum radius 3 mm everywhere your hand touches.
- Top mounting face 66 x 46 mm, flat, to match the underside of the Stage 5 enclosure (or any enclosure you have; adapt the numbers).
- Hollow with a 2.5 mm wall, split into two halves along the mid-plane for printing, or one body with an access opening of your choosing.
- G1 or better between all visible surfaces, and no reflection kinks in Zebra.
Method hints (not step by step). Start in the Form workspace with a Box or Quadball, use mirror symmetry so left and right halves match, and shape by selecting loops of vertices rather than single points (see Edit Form and Selection). Add detail with Subdivide and Insert Edge only where you need it. Finish Form, verify with Zebra, then use solid tools for the mounting face, the clip features and the shell. Decide where you need the Form to stay editable.
Deliverables#
- A Fusion design with the grip as a solid body (or two halves), a clear timeline and named bodies.
- A Zebra Analysis in two stripe directions with no kinks, plus a Curvature Comb screenshot on one cross-section.
- Measurements: length, mid-section width and depth, top and bottom section sizes, groove depth, wall thickness, all in a table against the targets.
- A mounting face that lies flat to within 0.1 mm (checked with Measure or Section Analysis).
- A one-paragraph note on how you would print or mould it: orientation, split line and draft.
Challenges#
No step-by-step. Use the Learn pages. Dimensions in millimetres.
Challenge 1: Soft-shoulder knob#
Brief. A kitchen scale needs a rotary knob with a smooth, premium look: a dome that blends into a straight cylindrical skirt with no visible seam.
Constraints.
- Knob diameter 40 mm, overall height 25 mm, skirt 10 mm tall, dome 15 mm tall, built as separate surfaces and stitched.
- Shoulder joint between dome and skirt: G1 minimum, G2 target.
- Wall 2.0 mm, solid result, no open edges.
Deliverables.
- Surface construction with the skirt, dome and any Patch or blend visible in the timeline.
- Zebra and Curvature Comb results at the shoulder.
- A thickened solid.
Self-check.
- Stitch reports zero free edges.
- Zebra stripes cross the shoulder without a break or kink.
- The Curvature Comb teeth on both sides of the shoulder are close in length at the joint (G2), or at least the tangents match (G1).
- Overall height measures 25 mm and diameter 40 mm.
- Wall thickness reads 2.0 mm with Section Analysis.
- Changing the skirt height to 8 mm still rebuilds with zero free edges.
Stretch. Repeat with a ruled or lofted surface for the dome and compare which one gives smoother curvature. Hint: see Continuity G0 to G3.
Challenge 2: Computer mouse shell in Form#
Brief. A start-up wants a wireless mouse shape for right and left hands, sculpted in Form and ready for detailed design.
Constraints.
- Target envelope 110 long x 62 wide x 38 mm high after Finish Form.
- Mirror-symmetric about the long centre plane so it fits either hand in the base shape.
- Front is lower than the back (about 20 mm high at the front edge, 38 mm at the hump, which sits about 40 mm from the back).
- Hollow with a 2.0 mm wall.
Deliverables.
- Form body with internal mirror symmetry.
- Solid after Finish Form, shelled to 2.0 mm.
- Notes on your cage layout (faces long x wide x high).
Self-check.
- Bounding box within 1 mm of 110 x 62 x 38 after finishing.
- Editing one side of the cage changes the other side.
- Zebra has no kinks on the top surface.
- Wall measures 2.0 mm in section.
- Reopening the Form feature and moving a row of vertices updates the shell.
Stretch. Add a scroll-wheel notch with Insert Edge and a crease, keeping the symmetry. Hint: see Creases, Insert Edge and Topology Tools.
Challenge 3: Remote control back shell from surfaces#
Brief. Model the curved back shell of a TV remote: gently arched side to side, with a lower curve toward the thumb end, as a thin-wall part.
Constraints.
- Outer envelope 160 x 45 x 18 mm; arch rise across the width 6 mm.
- 1.8 mm wall, 1 degree draft on the parting edges (general guidance for ABS).
- Open face on the front, with a stepped flat parting edge 2 mm wide.
- Corner radius in plan at least 8 mm.
Deliverables.
- Surfaces for the outer shape (loft or sweep), trimmed to the envelope.
- Thickened shell with the parting edge.
- Section views through the thickest and thinnest points.
Self-check.
- Thicken direction is correct (the outer envelope stays 160 x 45 x 18).
- Wall measures 1.8 mm in Section Analysis at three places.
- No Thicken failure at tight inside curves: if one occurred, you reduced the curve or the thickness.
- Zebra on the outer face is smooth.
- Changing the width to 48 mm rebuilds without errors.
Stretch. Add a battery door opening 45 x 25 mm that sits flush with the surface. Hint: see Thicken and Solid From Surface.
Challenge 4: Reverse-engineer a grip from a mesh#
Brief. A client provides a scanned clay model of a handle as an STL and asks for a clean model they can modify.
Constraints.
- Use any STL of a handle-like object you have, or download one that is free to use. If the unit is unknown, set it to millimetres and scale to about 115 mm long.
- Target a mesh of at most 20,000 faces for working.
- The result must be a closed solid body, not just a mesh.
Deliverables.
- A repaired and reduced mesh.
- A solid BRep (faceted, prismatic or by rebuilding with sections and Form).
- A comparison between source and result in a section view.
Self-check.
- The Mesh repair report shows a closed, oriented mesh with positive volume.
- Reduced face count is 20,000 or less.
- Final body reports a volume in Properties (it is a solid).
- Section views show the solid within about 0.5 mm of the mesh at three stations.
- You can state which method you used and why.
Optional (extension required). Convert Mesh with Method Organic and Operation Base Feature to get a T-spline Form, then tidy it in Form and Finish Form. Hint: see Converting a Mesh to BRep.
Stretch. Rebuild the grip with section sketches taken from the mesh and compare the quality of the two surfaces with Zebra.
Challenge 5: Form body with machined features#
Brief. A handheld scanner body has an organic outer shape but needs a precise USB-C cutout and battery hatch.
Constraints.
- Form body about 130 x 55 x 35 mm after Finish Form.
- Battery hatch 40 x 25 mm, 6 mm from the end, flat bottom.
- USB-C cutout 9 x 3.5 mm (typical connector opening plus clearance), centred on the end wall.
- Wall 2.0 mm.
Deliverables.
- A Form body finished to a solid.
- Prismatic features cut with sketches on construction planes.
- A short note on the order of operations that kept the model stable.
Self-check.
- Hatch opening measures 40 x 25 mm and cutout 9 x 3.5 mm.
- Reopening the Form feature and nudging a vertex does not break the hatch or cutout, or you can explain why it did.
- The timeline shows no warning icons after the edit.
- Wall thickness at the hatch edge is at least 2.0 mm.
Stretch. Add a mating lid, referencing construction planes rather than form faces. Hint: see Finish Form and Converting Between Form and BRep.
You have finished this stage when#
- I can build a surface from sketches, trim, extend and patch it, and stitch it to a solid with zero free edges.
- I can choose between G0, G1 and G2 for a joint and verify the result with Zebra and Curvature Comb.
- I can sculpt a symmetric T-spline body by editing loops and know why the surface sits inside the cage.
- I can finish a Form, fix a failed finish and compensate for shrinkage to hit a target size.
- I can turn a surface or Form into a shelled, manufacturable wall.
- I can import, repair and reduce a mesh, and say which conversion method suits it.
- I can combine freeform bodies with prismatic features without breaking the timeline.
- I have a comfortable, printable grip design for the capstone.
Next stage#
Continue with Stage 7: Communicate Your Design.