Mechanical assemblies
QuantCAD builds multi-part mechanical designs from a description of the parts and how they connect. In Build manual mode you create the assembly part by part and confirm each step. In auto mode QuantCAD plans and builds the whole assembly in one pass. Every part is a B-rep solid, and the assembly exports to STEP.
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How should you describe an assembly?
Name the parts, say how they interface, and give the dimensions that matter. Treat the first result as a baseline, then refine clearances and features with small changes.
Two-piece clamp assembly
Create a two-piece clamp assembly for a 25mm diameter tube. Part A: a base half with a flat mounting foot (60mm x 25mm x 6mm) and two M6 clearance holes spaced 40mm apart. Part B: a matching top half. The clamp bore should be 25.4mm diameter to allow clearance. Add two M6 through-bolts locations with 6.6mm clearance holes and hex nut pockets on the base part. Add 2mm fillets on external edges.Why build assemblies as solids instead of meshes?
An assembly works only if its parts meet where they should. Solids keep every bore, hole pattern and mating face exact, so you can check a clearance and change it. A mesh gets each surface close, and the small deviations show up at every interface. See text-to-CAD vs text-to-mesh for the full comparison.
What to specify
- Part list, and which part mates to which.
- Critical interface dimensions (bores, hole patterns, slot widths).
- Clearance targets, for example 0.2 to 0.5 mm depending on the process.
- Fastener intent (through holes, countersinks, nut pockets).
- Edge treatments (fillets and chamfers) and minimum thickness.
Frequently asked questions
Can QuantCAD generate multi-part designs?
Yes. Describe the design as a set of parts and how they connect. In Build manual mode you create the assembly part by part and confirm each step. In auto mode QuantCAD plans the parts, builds the whole assembly in one pass and verifies the result.
Can I export an assembly to STEP?
Yes. QuantCAD exports the assembly as a STEP file (AP242, millimetres) with every part as a B-rep solid, ready for final detailing, drawings and manufacturing preparation in your CAD tool.
How do I get clean interfaces between parts?
Be explicit about reference geometry and constraints: hole sizes, bolt patterns, clearances, alignment pins, and where faces should be flush or offset. Iterating on one interface at a time is usually the fastest way to dial in the fit.
Should I use a mesh generator for an assembly I want to manufacture?
No. A mesh approximates each surface with triangles, so the fit between parts is close rather than exact, and there are no real faces or edges to dimension or tolerance. For an assembly with tight fits or a manufacturing handoff, start from B-rep solids.