Updated 2026-10-14
To convert SLDASM to STEP, drop the .sldasm into the converter below and download one .step of the assembly with every component in place. The catch is worth knowing first: an assembly file references its parts rather than containing them, so one sent on its own often has no geometry to convert. If so, ask the sender for a STEP of the whole assembly. Assemblies of up to 5 parts need no account.
2 solid-geometry conversions a day with no account. No card, no install, no CAD licence.
On our servers. No account: deleted within 24 hours. Signed in: kept until you delete them. Never shared or used for training.
A closed STEP solid that Fusion 360, Inventor, Onshape, SOLIDWORKS, Creo and FreeCAD open directly and a machine shop can quote from. Radii measure and faces mate like modelled geometry. Where those surfaces cannot be read, or cannot be written out exactly, they are rebuilt from the display geometry, and failing that the body is faceted; every conversion says which of the three.
No feature history: you get the finished shape, not the steps that built it.
A SLDASM records which parts make up a product, where each one sits and how the mates constrain them. The shapes usually live in the separate .sldprt files it points to. A STEP of an assembly is the opposite: geometry, placed, and nothing about how it is held together.
So the shape and the arrangement come across, and the engineering behind them does not. Each component lands where the assembly put it. The mates, the parts' feature trees, configurations and exploded views stay behind. If someone needs to move the components again, they will be re-mating them in their own CAD system.
What the solid is made of varies: usually the components arrive on their own surfaces, so a hole stays a cylinder you can measure and machine. Where those surfaces cannot be read they are rebuilt from the display geometry, and failing that the body is faceted. The conversion says which of the three it gave you.
When the assembly arrived on its own and the converter finds no geometry in it, it says so rather than returning an empty file, and the attempt does not count against your free conversions. The fix takes the sender a minute: open the assembly in SOLIDWORKS and use Save As, STEP. If you need their native files instead, Pack and Go gathers the assembly and every part into one folder.
A SLDASM file is a SOLIDWORKS assembly: parts positioned by the mates that constrain them. Sent with its SLDPRT files, the whole product converts as one and component names are kept. An assembly that stores its components’ shapes converts on its own too, every component placed where it sits — as a mesh, or as a solid whose surfaces are rebuilt from those stored shapes.
Someone sent you a whole product and you need it in a neutral format your CAD system, renderer or printer takes.
STEP (ISO 10303) is the closest thing engineering has to a universal solid format. It stores exact B-rep geometry — a hole is a cylindrical face, not a ring of facets. Fusion 360, Inventor, Onshape, SOLIDWORKS, Creo, NX, CATIA and FreeCAD all read it; .step and .stp are the same format. AP242 supersedes AP203 and AP214.
What you send when the other side has to keep modelling, quote machining, or open the shape in a different CAD system.
Keep the part open: fill it with a lattice, check it with FEA, texture a surface, or slice it into cut-ready sheets. These workspaces are in early access — create an account, then apply from inside the app.
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