Concept 3D CAD, built.
Also called: Concept model · Master model · Massing model · First 3D build
The first proper 3D model of the chosen concept, built on clean datums with parametric intent, enough to check form and assembly.
Build the concept in 3D on three clean datum planes, with dimensions driven by intent rather than dragged by eye. Model enough to check form, fit and assembly. Hold detail back: this model feeds every later stage, so it has to stay easy to change.
What concept 3D CAD is
Concept 3D CAD is the first time the chosen concept becomes solid geometry rather than sketches and intent. You set up datums, you build the major bodies, and you check that the parts actually fit together in three dimensions. It is the model everything downstream is cut from, so the discipline is in how it is built, not how finished it looks.
The temptation is to chase realism: fillets, threads, screw bosses, a textured surface that renders well. Resist it. At concept stage the model exists to answer two questions. Does the form work, and does the assembly close? A clean model that answers those in an afternoon is worth more than a beautiful one that takes a week and breaks the moment you change a wall thickness.
Datums and parametric intent
Start with three datum planes and an origin you will never move. Every later feature references back to those, so when a dimension changes the model updates instead of collapsing. Drive the geometry with named dimensions that carry meaning, a wall thickness, a lid clearance, a cavity depth, not numbers typed in by eye. In my experience this is the single thing that separates a model you can edit from one you quietly rebuild three weeks later.
Level of detail
Model the major bodies and the interfaces between them. Leave the cosmetic detail, the production fillets, the fastener features for the detailed-design stages that follow. Over-detailing early is the most common way a concept model becomes a liability: it gets slow, brittle, and so expensive to change that the team stops changing it even when the form is wrong.
One model, five honest answers. Notice none of them is cosmetic. The concept model earns its place by checking form and fit, not by looking like the finished object.
How it fits the bigger picture
Concept 3D CAD opens Stage 07 Engineer. The concept model it produces is what basic 2D drafting (06.20.02) draws from next, turning the 3D bodies into dimensioned views that the workshop and the suppliers can actually read.
What it can do
Turn a chosen concept into solid geometry you can rotate, section and measure. Catch a clash, a form that does not work, or a cavity that is too shallow now, in CAD, instead of in a first ceramic sample weeks later. Give every downstream activity a single source of truth for the geometry.
What it can’t do
It can’t make the part manufacturable on its own; that is what the detailed-design and design-for-manufacture activities later in Engineer do. And a concept model built without clean datums can’t carry that work, it has to be rebuilt, which is exactly the cost this activity exists to avoid.
See the full 10-stage process →
Try it yourself
Open a clean part. Set three datum planes and a fixed origin before you draw anything. Build only the major bodies of your concept, and drive every key dimension with a named parameter, not a typed number. Then change one of those parameters and watch what happens. If the model survives the change, your intent is sound. If it collapses, your tree is built on geometry instead of datums, and it is cheaper to fix now. Start the Free Sprint →
- Production fillets and chamfers on every edge.
- Screw bosses and fastener features modelled in full.
- Dimensions dragged by eye, no named parameters.
- A heavy, brittle tree nobody dares to change.
- Three datum planes off a fixed origin.
- Major bodies only, interfaces checked.
- Key dimensions driven by named parameters.
- Light, editable, ready to feed downstream.
Your concept-CAD checklist
Project notes: the model that took the wall change
▸ From the notebook · optional reading
Building the proofing box concept model in Stockport, and the half-day that proved the datums were worth setting up first.
3 min read · click to open
Dan wanted to see the £149 box in 3D the moment the concept was chosen, and so did I. The discipline was agreeing what not to model. We worked from three datum planes off a fixed origin at the base, and built only the four major bodies: the double-wall ceramic shell, the lift-off lid, the wood band, and the internal cavity for the element and PCB.
What we drove parametrically
Wall thickness, cavity depth and lid clearance were all named dimensions, not numbers I had dragged into place. I asked Dan to treat the model as a question, not a picture: every body had to earn its place by checking a fit, and nothing got a fillet.
Where it paid off
The Stoke-on-Trent ceramic enquiry came back: the double wall needed to be thicker than our first guess to fire reliably without cracking. On a model dragged by eye, that is a half-day rebuild. On ours, I changed one wall-thickness parameter and the cavity, the lid clearance and the element pocket all updated together. The two 1kg dough balls still cleared the inner wall. The whole change took about ten minutes, and most of that was double-checking it had not broken anything.
What we deliberately left out
- No production fillets or chamfers, those waited for detailed design.
- No screw bosses, the cavity was a single block envelope.
- The rotary and OLED were plain blocks, placed but not detailed.
The concept model fed basic 2D drafting and the wall-section studies without a single rebuild, and it carried the BS EN 61010 clearance work later in Engineer. Setting the datums up first cost twenty minutes. It saved a great deal more than that before the project was out of Design.
— Engineer stage, project notes, 2026
— Next in Design → Basic 2D drafti