Stage 2: Solid Modeling

Goal#

After this stage you can turn a fully constrained sketch into a three-dimensional product and refine it the way a real designer does: extrude and revolve the main shapes, round and bevel the edges, drill the holes, hollow the body into a thin-walled part, repeat features with patterns and mirrors, and place reference planes and axes wherever a feature needs them. You will also be able to predict what a feature will do before you click OK, and check it with the Measure tool afterward.

Why this matters for product design: almost every consumer product is a hollow, rounded body with holes, screw bosses and repeated features. A phone case, a speaker shell, a kettle, a mouse, a desk organizer: all of them are built from the small set of operations in this stage. The difference between a beginner and a competent designer is the order of operations and the habit of tying sizes to parameters, so changing a wall thickness or a hole count is a one-number edit.

Before you start#

• Finish Stage 1: Foundations. You should be able to draw a fully constrained sketch with named parameters without looking anything up.
• You should be comfortable with the timeline, with renaming browser items, and with Inspect > Measure.
• Same licence as before: the free personal-use licence is enough. Nothing in this stage needs an extension.
• Set aside roughly 12 to 16 hours. The practice exercises on these pages are longer than those in Stage 1 because they use real numbers; do them with a calculator beside you and predict each answer before measuring.

Learn#

Read the pages in this order. Each builds on the one before.

• Read Extrude - the workhorse feature. Focus on the Options reference (Start, Extent, Direction, Taper Angle, Operation) and on "Join, Cut and Intersect behaviors that surprise people".
• Read Revolve - for every round part: caps, bottles, knobs, cups. Focus on the axis choices and "Failure modes and fixes".
• Read Fillet and Chamfer - edge rounding and bevels. Focus on "Tips and pitfalls" and "Sizing fillets and chamfers with real numbers".
• Read Hole and Thread - simple, counterbore and countersink holes. Read the thread sections lightly now; you will use threads more in later stages.
• Read Shell, Draft and Scale - hollow bodies. Focus on Shell now and "Order of operations"; skim Draft and Scale.
• Read Mirror and Patterns - copy features instead of redrawing them. Focus on "Choosing a pattern type" and "Numbers for linear patterns".
• Read Construction Geometry - planes, axes and points you can sketch on or build from. Focus on "Choosing references that survive edits".
• Read Sweep - only the basic path-and-profile workflow, because the mug handle in the checkpoint project uses it.

Reading note: Extrude and Fillet pages are long. Read the Step by step and Options reference sections fully, then read the numbers sections with a pencil, rechecking at least one calculation.

Practice#

Do the exercise at the end of each page. They are intentionally demanding: each asks you to predict a number, measure it, and then deliberately break the feature to see the error.

• Do the practice exercise on Extrude (a drafted tray with a pocket, a boss that follows the rim, a thin-extruded U-channel).
• Do the practice exercise on Revolve (a wine glass, an O-ring groove on a shaft, an elbow, and an axis-crossing error).
• Do the practice exercise on Fillet and Chamfer (a shelled base with measured inside corner radius, a variable fillet, two chamfers).
• Do the practice exercise on Hole and Thread (a mounting plate with counterbored, tapped and countersunk holes).
• Do the practice exercise on Shell, Draft and Scale (a drafted, shelled cover; skip the Scale steps if short on time).
• Do the practice exercise on Mirror and Patterns (a vented plate and a bolt circle).
• Do the practice exercise on Construction Geometry (a bracket whose features hang off planes and an axis, then a stress test).

Then run these drills, 10 to 20 minutes each:

• Drill A, predict then measure (15 minutes). Extrude a 60 by 40 mm rectangle 25 mm. Without looking at the answer, predict the volume (60,000 mm^3) and then read it from the body's Properties. Add a 10 mm through hole at the center and predict the new volume: 60,000 minus the hole, pi x 5^2 x 25 = 1,963.5 mm^3, so about 58,036 mm^3. Compare. Write down the difference, if any.
• Drill B, order of operations (15 minutes). Make a 60 by 40 by 25 mm block. Version 1: fillet the four vertical edges at 4 mm, then shell inward 2 mm with the top face removed; measure the inside corner radius (expect 2 mm). Version 2: shell first, then fillet the outside vertical edges at 4 mm; observe the inside corner. Write one sentence on which order gives a uniform wall.
• Drill C, one number, many holes (15 minutes). Cut one 5 mm hole in a 100 by 60 by 8 mm plate and Circular Pattern it into a ring. Create a parameter n_holes, drive the Quantity from it, and change the value from 6 to 10 and back. Confirm the spacing updates.
• Drill D, reference planes (20 minutes). Build a 40 by 40 by 60 mm block, an Offset Plane at half the height, and a hole on that plane. Change the block height to 80 mm and check the plane and hole follow. If they do not, explain which reference you chose badly.

Checkpoint project#

Project: the coffee mug, then a variation. First do Tutorial: Coffee Mug (Revolve and Render) through Part E (revolve the body, sweep the handle, fillet the edges). You can skip the optional liquid body, appearance and render parts (F to H) for now; rendering is covered in a later stage. Estimated time: 60 to 90 minutes for the tutorial, then 45 to 60 minutes for the variation.

Keep the tutorial's dimensions: 90 mm overall height, 3.5 mm wall, 6 mm base, 1.5 mm rim fillet. These are the numbers you will vary.

Variation brief: an espresso cup. A cafe wants a smaller cup in the same style. Without redoing the tutorial from scratch, create a copy of your mug and turn it into an espresso cup, preserving the profile sketch and changing it by editing dimensions.

Constraints. 60 mm overall height. 50 mm outer diameter at the base, 60 mm at the rim. 3 mm wall (typical for porcelain). 5 mm base thickness, so the inside depth is 55 mm (60 - 5). Handle attachment points 30 mm apart and the handle reaching 18 mm out from the wall. Rim fillet 1 mm. All major sizes should be named parameters.

Deliverables.

• The completed mug (saved as Mug) with its revolve, sweep and fillet features all green in the timeline.
• A copy saved as Espresso-Cup with the new dimensions.
• A cross-section view of the cup (Inspect > Section Analysis) showing the wall.

Checks.

• Overall height measures 60 mm and the rim outer diameter 60 mm.
• Wall thickness reads 3 mm at the section, and the rim fillet is 1 mm.
• Changing the height parameter to 70 mm updates the cup without any error in the timeline.
• The handle remains attached at both ends after the edit. If it detaches, note which reference moved and why.

Challenges#

Open design briefs. Each mixes this stage's tools with Stage 1's sketching habits. No steps are given: choose the features, the order and the references yourself, and justify your order of operations in a one-line note in the design description.

Challenge 1: Pencil cup#

Brief. A desk-accessory brand wants a simple pencil holder as a revolved body, made from a printed material. The client may later ask for a taller or wider version.

Constraints. Overall height 80 mm, outer diameter 70 mm, wall 3 mm (typical for a rigid printed part), base 4 mm thick. A 3 mm fillet on the outer bottom edge and a 1 mm fillet on the top rim. Height and outer diameter are named parameters. Work from a single revolve profile, not a shell.

Deliverables.

• A fully constrained revolve profile and the solid body.
• Both fillets applied.
• The parameters cup_h and cup_d.

Self-check.

• The inside diameter measures 64 mm (70 - 2 x 3) and the inside depth 76 mm (80 - 4).
• The inside volume reads roughly 244,000 mm^3 (pi x 32^2 x 76), about 244 ml, before the fillets reduce it slightly.
• Section Analysis through the center shows a constant 3 mm wall.
• Changing cup_d to 80 mm gives an inside diameter of 74 mm with no timeline error.

Stretch. Redo the same cup using Extrude plus Shell instead of Revolve and compare the two timelines. Which one is easier to edit, and why?

Hint: see Revolve and Shell, Draft and Scale.

Challenge 2: Enclosure base with screw bosses#

Brief. An electronics startup needs the bottom half of a small enclosure with four screw bosses inside. Another team will design the lid later, so the base must be clean and parametric.

Constraints. Outer size 90 mm by 60 mm by 30 mm, open at the top. Vertical outer edges rounded 4 mm. Wall and floor 2 mm (typical for a small molded or printed part). Four round bosses, 6 mm outer diameter and 8 mm tall above the floor, centered 8 mm in from the outer walls (so 74 mm apart along the length and 44 mm apart across the width). Each boss gets a 2.5 mm diameter pilot hole, 6 mm deep (typical for an M3 self-tapping screw in plastic). The wall thickness must be a named parameter.

Deliverables.

• The shelled body with rounded corners.
• One boss with its hole, patterned or mirrored to four.
• A parameter called wall.

Self-check.

• The inside dimension reads 86 mm by 56 mm (90 - 2 x 2 and 60 - 2 x 2) and the inside depth 28 mm (30 - 2).
• The inside corner radius measures 2 mm (4 - 2).
• Boss centers are 74 mm and 44 mm apart. Each boss clears the wall by 3 mm (inside face at 43 mm from center, boss edge at 40 mm).
• Changing wall to 2.5 mm updates the shell and the corner radius becomes 1.5 mm.

Stretch. Add 2 mm by 2 mm ribs of 6 mm height on the floor between bosses and the nearest wall.

Hint: see Fillet and Chamfer for the fillet-before-shell order, and Mirror and Patterns.

Challenge 3: Control knob with scalloped grip#

Brief. A hobby synth maker needs a rotary knob that is easy to grip with a wet or gloved finger.

Constraints. Revolved knob 40 mm diameter and 20 mm tall. A blind hole in the underside for a 6 mm shaft: use 6.2 mm diameter (typical clearance for a 6 mm shaft) and 12 mm deep. A 1 mm chamfer on the top edge. Eight scallops evenly spaced around the side: each a cut made with a 4 mm circle centered on the 40 mm outer circle, running the full height.

Deliverables.

• The revolved knob with hole and chamfer.
• One scallop cut and a Circular Pattern of eight.
• Parameters for the number of scallops and the shaft diameter.

Self-check.

• The adjacent scallop centers are 15.3 mm apart (2 x 20 x sin 22.5 degrees).
• The hole measures 6.2 mm across and 12 mm deep, leaving 8 mm of material above it.
• Setting the scallop count to 12 keeps the pattern evenly spaced (30 degrees).
• Section Analysis shows the hole is centered on the axis.

Stretch. Add a 1.5 mm wide, 1 mm tall pointer ridge on top running from the center to the edge, and explain why a Circular Pattern is the wrong tool for it.

Hint: see Mirror and Patterns, "Numbers for circular patterns", and Hole and Thread.

Challenge 4: Vented lid#

Brief. A small power adapter box needs a vented lid. The vents must be adjustable, because testing might show the box runs warm.

Constraints. Lid 100 mm by 60 mm, 3 mm thick, with 5 mm corner fillets. Four 3.4 mm through holes centered on the corner fillet centers (5 mm from both edges, so 90 mm apart along the length and 50 mm apart across the width). Five vent slots, each 3 mm wide and 30 mm long, running across the width, at an 8 mm pitch, centered on the lid.

Deliverables.

• The lid outline with the corner holes.
• One slot patterned to five.
• Parameters for slot pitch and slot count.

Self-check.

• The five slots span 35 mm overall (4 x 8 + 3), and the first and last slot centers are 32 mm apart.
• The gap between neighboring slots is 5 mm (8 - 3).
• Hole centers measure 90 mm by 50 mm and are concentric with the corner fillets.
• Changing the slot count to 7 keeps the pattern centered (check that the first and last slots are at equal distance from the lid center).

Stretch. Give the lid a 1 mm raised border on its underside that locates it inside the box, 2 mm inside the outer edge.

Hint: see Mirror and Patterns, "Numbers for linear patterns", and Extrude.

Challenge 5: Phone stand#

Brief. A phone stand for a desk. The phone leans back so the screen is readable from a sitting position.

Constraints. Base 80 mm wide, 70 mm deep, 6 mm thick. A back support 80 mm wide, 5 mm thick and 60 mm long, leaning back 15 degrees from vertical, so the angle between its front face and the top of the base is 75 degrees. A front lip 8 mm tall and 4 mm thick at the front edge of the base. Fillets of 3 mm on the top edges of the back support and lip. The lean angle is a named parameter.

Deliverables.

• A base, a leaned back support and a front lip, joined into one body.
• A construction plane or axis you used to define the lean.
• A parameter named lean.

Self-check.

• The angle between the back support's front face and the base's top face measures 75 degrees.
• The base measures 80 by 70 by 6 mm and the lip stands 8 mm above the base's top face.
• Changing lean to 20 degrees updates the support with no errors.
• No fillet fails, and the timeline shows no warnings.

Stretch. Add a 10 mm wide cable slot in the lip, centered, and a rounded 3 mm radius notch below it.

Hint: see Construction Geometry, "Plane at Angle numbers".

You have finished this stage when#

• I can extrude a profile with a chosen start, extent and direction, and I can pick Join, Cut, New Body or Intersect deliberately.
• I can revolve a profile around a sketch line and fix the common axis errors.
• I can apply fillets and chamfers in an order that does not fail, and I can read the radius of an inside corner after a shell.
• I can place counterbored and countersunk holes, and I know how to size them for a screw.
• I can hollow a body with Shell, and I can explain why the order of fillet and shell matters.
• I can pattern a feature and drive the count and spacing from parameters.
• I can build a construction plane or axis and confirm that features on it survive a dimension change.
• I finished the mug, produced the espresso-cup variation, and completed at least three of the five challenges.

Next stage#

Continue with Stage 3: Parametric Design.