Beta 4.0.0 · Windows 10 / 11 · 64-bit · free
A lightweight 3D modeller for everyone on Windows: drop in shapes, type exact sizes
in any unit, cut and combine them, and export a watertight .stl ready to print.
No learning curve. No cloud. No account. No installer. Just one file that opens in a
second.
New in 4.0.0: the Library — thirty-one parts made to your numbers, from a box with a lid to a roof for a model house and the wheels behind a clock’s hands.
In loving memory of Windows 3D Builder. Rest in peace.
Nine primitives on a 10 mm grid, or a custom one with its segments and roundness chosen before it is made. Type the size you want — not drag it and hope. Subtract, Intersect and Merge run on Manifold, a geometry engine that does not tear, and every result is checked: if one would not be watertight it is refused, and your object is handed back untouched.
Point it at a model and it decides which way the mould comes apart — a ring gets pulled along its hole, not across it — cuts at the widest section, keys the halves together, and drills the pour hole at the high point, with vents where a flat pocket would trap air.
Brick, roof tiles, wall tiles, planks, wood grain and stripes — cut in or standing proud, on any flat face, including one that already has windows in it.
Any installed font, or the filled shapes of an SVG. Cut, raised, bevelled, and wrapped round a barrel or a ball — or bring the drawing in as a solid of its own.
Weld, cap holes, turn inside-out shells the right way. When that is not enough, Rebuild remakes the surface from scratch and Hollow turns a solid into a shell — with one side left open, if it needs one.
A tape that snaps to corners and edges, either end draggable. Fit check answers the question a render cannot: do these two parts actually meet, and by how much?
Cut a part too big for the plate and pin the halves, or pin two parts that already rest on each other. Pins go only where there is solid round them, spread out towards the edges, and pegs stand up out of the lower part — nothing hangs off an underside, and every one is marked on the cut before it is made. Or join them with brick studs, which hold by grip.
Turn a shape more the higher it goes, narrow it to a spire, or curve it over like a horn. Edges are broken up only where the curve needs them, so a twisted column stays light — and nothing is cut, so nothing can tear.
Studs on any flat face and the brick underside that goes over them, on the 8 mm grid — on a brick, a disc or a scan cut flat. A printable Fit test finds the tolerance your filament needs.
Extrude down cuts at a height you drag and carries the outline straight to the plate: a clean plinth under a scanned bust with a ragged neck, a body under a relief that is only a skin.
STL and OBJ in and out, and 3MF — 3D Builder's own format — with parts, names, colours and units kept. SVG drawings come in as solids. Drop a file on the window, or double-click one.
Watertightness is checked on every export, and every risky operation says plainly what it did — or refused to do, and why. A modelling tool for printable parts should be hard to leave broken quietly. That is the whole design brief.
A 1:87 house built entirely inside the app, by driving its own buttons — then checked by ray-testing the exported STLs against a list of points. 74 checks, all passing.
The ribbon is split by what a tool changes: Edit changes the thing itself, Align changes where it sits, and Tools is the work around it — measuring it, mending it, casting it, and building it into parts that fit together. Nothing is buried in a menu. And if all of it is more than you came for, Classic mode puts the ribbon back to the tools 3D Builder had, and Extended mode goes the other way and adds the specialised ones. Whichever you pick, every key still works and no tool’s own settings are hidden — only its button.
§ 03.1
Nine primitives, the Library in Extended mode, Custom for a shape with its size, segments and roundness chosen first, Fit test plates for finding the tolerance brick studs need, and the way in for anything made elsewhere. Every shape lands on the plate at a sensible size and takes its colour from a six-step cycle, so a scene stays legible without anyone painting anything. Import reads STL, OBJ and 3MF, SVG drawings as solids, and another 3DFastCraft project — which joins the plate rather than replacing it. Sketch draws your own outline on the plate — lines, arcs, curves, freehand, or an SVG loaded in — and extrudes or revolves it into a solid. Text now bends a line of lettering round a circle or round a cylinder as well as laying it flat, and Lithophane turns a photograph into a plate that only shows when it is lit from behind.
On the plate: one of nearly everything on the tab — the nine primitives, a gear and its partner, a ratchet and pawl, an M8 bolt and nut from Thread, brick-stud fit plates, and the app's own name from Text — with the hexagon selected and its move arrows on it.
§ 03.2
Everything that changes the selection, from a boolean down to a colour. Undo and redo, Copy, Cut and a Paste that lands exactly where the thing came from, duplication beside or in place, and delete.
Boolean arithmetic on Manifold with the app's own BSP engine behind it — Subtract, Intersect and Merge. Any of it can be stopped part-way and leaves the model as it was; if a result would not be watertight it is refused and the objects are handed back untouched. Split takes a plane you can slide, tilt by dragging a ring, or set to a face you click. While you aim it the half that would be thrown away is faded, so you see what you are keeping before you commit — and the cut goes through the triangles rather than through the boolean, so a 200,000-triangle scan splits in a twenty-fifth of a second with both halves closed.
Set pivot puts the point a part is measured and turned about wherever you click, instead of the middle of its bounding box — a gear turns on its shaft, not on the outline of its teeth. Then Round, Twist, Taper and Bend to reshape it, Simplify and Smooth for a dense import, and Hollow to save material.
On the plate: a plain cylinder twisted into a vase, 50 × 50 × 80 mm and watertight, with the resize handles on it and the whole tab behind — undo through to colour in one row.
§ 03.3
Where a thing sits, without changing the thing. Drop to the plate, lay a part on a face you pick — every face it can rest on is marked — mirror it, line a selection up on any axis — flush either side, centred, or spread evenly. Align to centres one object on another.
On the plate: four M8 bolts spread evenly along Y, the whole selection moved as one — the status line says what it did.
§ 03.4
The work around a model rather than its shape. Measure and Fit check answer a question and leave both parts alone — how long, or how far two of them overlap. Repair and Rebuild mend a model that will not print, the second by remaking the surface from scratch when the first cannot. Mould makes a block to cast silicone in, cut so the casting comes out, with registration keys and a pour hole.
Voronoi cuts a solid into a web of struts — a shell that follows the surface for a lamp or a vase, or a lattice through the whole volume to take weight out of a part that still has to be stiff. Hull wraps a selection in one skin, Emboss and Engrave put lettering, a drawing or brickwork on a face you pick, Repeat copies a part along a line or round a circle, and Extrude down puts a flat base under a scan. Split with connectors cuts a part too big for the plate into halves that pin back together — separate pins, pegs or brick studs, square to the cut, vertical or horizontal — and Connect objects does the same for two parts that already rest on each other. If there is no room for a pin, it says how thick the wall would have to be rather than cutting one through the side.
On the plate: a scanned head between the two halves of the silicone mould made for it, and Measure along an edge of one half, snapped to its corners: 135.09 mm.
§ 03.5
New, open, recent, save, and named versions kept inside the project file so you can go back to one. Export asks what to write before it writes it: everything or the selection, binary STL, ASCII STL, OBJ or 3MF, and whether to drop the result to the plate. Blueprint draws the model as an engineering drawing — front, top and right views and an isometric, hidden lines dashed, the overall dimensions and a title block — to print, or to save as a PDF.
On the screen: Export asking what to write — everything on the plate or just the selection, and which of the four formats — with the totals it is about to produce: 11 objects, 29,334 triangles, 326.6 cm³.
§ 03.6
Six axis views and isometric, wireframe, x-ray to see a part buried inside another, Overhangs to show in red what will need support, and the build plate at your printer's width, depth and height. Scale 1: changes no geometry at all — it tells you what a millimetre means, so a model reads in metres as well.
On the plate: the 1:87 house with its parts lifted apart, the units switched to feet and the scale list open — sixteen standard scales from full size down to 1:220, with 1:87 picked, so the floor slab reads 0.509 × 0.361 ft.
Windows 3D Builder was a beautiful thing: fast modelling for professionals and for people who had never modelled anything, with almost nothing to learn before the first part was on the plate. Microsoft retired it. This app exists to take its place: a free Microsoft 3D Builder alternative that works the same way — the same short path from a shape on the plate to a printable part. These are the thirty tools it adds on top.
.3dfc project itself, and a way back to any of them.New in 4.0.0: parts made to your numbers. Pick one from the catalogue on the Insert tab (Extended mode), set its sizes with the preview standing on the plate, and insert it. The part remembers how it was made — select it later and Edit settings makes it again where it stands. Walls and fits start from your printer’s nozzle, layer and clearance, and every setting either makes a sound, watertight part or says plainly, in red, why it cannot. Thirty-one generators in seven groups.
Beta
3DFastCraft 4.0.0 betaOne self-contained file. No installer, no .NET runtime, no account. Download it, double-click it.
It is a beta: new, and still being proved out. Check what it gives you before you print it. The stable version is 3.3.0, on the main page — the two run side by side.
Windows SmartScreen will object the first time — the executable is not code-signed. More info → Run anyway.
SHA-256published with the beta