ProtoJoint Open the editor

Parametric CAD · in your browser · with AI

Describe a part in one sentence and Eleph, the built-in AI design assistant, models it, in sketches, features and named dimensions you can check and edit. Under it is a full parametric CAD in a browser tab: constrained sketches, assemblies with joints, STEP, STL and DXF, on Linux, a Chromebook, a Mac or Windows.

Open the editorWatch a gearbox build itself
  • Free to model
  • No sign-up to model
  • Eleph on the paid plans
The finished motor mount: a blue L-bracket on a 2020 aluminium extrusion, a NEMA 17 motor bolted to its slotted plate and a GT2 pulley on the motor shaft.

A NEMA 17 motor mount that bolts to a 2020 aluminium extrusion, with slotted holes to tension the belt.

  1. Read the model · a new document
  2. List the templates · none for this, so from scratch
  3. Insert a standard part · NEMA 17, M3 holes at ±15.5
  4. New sketch · 2020 profile, 251.2 mm²
  5. Extrude · 120 mm, centred
  6. Constrain and dimension · the L-section, 0 DOF
  7. Extrude · 60 mm: the motor and ±3 mm of travel
  8. Move bodies · the motor up 3 mm
  9. Draw in a sketch · four M3 slots and one for the boss
  10. Extrude · the slots cut through the plate
  11. Extrude · two alignment keys, +1044 mm³
  12. Draw in a sketch · four M5 holes, 40 mm apart
  13. Extrude · the M5 holes cut, 309 mm³ a pair
  14. Round edges · R4 on six corners
  15. Round edges · R1.5 in the inside corner
  16. Insert a standard part · a GT2 20T pulley on the shaft
  17. Check for clashes · 12 bodies, none
  18. Move bodies · at +3 mm of travel: still clear
  19. Look at the model · a section at X = 20

I've built the NEMA 17 mount: an L-bracket, 60 × 25 × 67 mm, that bolts into the extrusion's T-slots on two faces. One parameter, travel, sets all five slots for ±3 mm of belt travel. No clashes between the 12 bodies.

One sentence. A part you can print. A real run, sped up: Eleph, on Opus 5.5 with the Max plan, took 39 steps and under six minutes, placed a library motor and pulley, drew and dimensioned the bracket around them, checked its own sums and found no clashes. It works from marks drawn on the view, or a photo of a sketch on paper, as well. Eleph needs an account and comes with the paid plans.

AThe CAD under it

A gearbox you can open.

Eleph works the way you do, in sketches, features and named dimensions, and this is what they add up to: an 11 : 1 cycloidal reducer modelled in ProtoJoint one feature at a time, 87 solids down to the last bearing ball. Cut it open across the disc or along the shaft, drag it round, and watch two discs roll on twelve ring pins while the output turns once for every eleven turns in.

See it modelled, step by step
The cycloidal reducer cut open across its first disc: the disc's eleven lobes against the twelve ring pins, the balls of the cam bearing in its bore, the six output pins in their sleeves.

14Keys4 × 4 × 22 and 6 × 6 × 16

BWhat comes in the tab

Everything a part needs, already there.

Not a toy and not a viewer: sketches, features, parameters, assemblies and the files that leave with you.

DETAIL A

Sketches that stay put

Snaps become constraints, typed numbers become dimensions. The sketch shows what is still free, and turns down a constraint that would fight the others.

DETAIL B

A timeline you can rewind

Extrude, revolve, sweep, loft, shell, draft, pattern, thread, coil. Roll back to any step, change it, and everything after it follows.

DETAIL C

Every number has a name

Type Width + 2*Wall into any field. Change one parameter and the whole model resizes around it.

DETAIL D

Rounds that come out right

Three rounded edges meeting at one corner, a pocket rounded at its rim and its floor in one go, a radius that changes along an edge: each comes out as one watertight solid, ready to print or machine.

DETAIL E

Assemblies that move

Rigid, revolute, slider, cylindrical, pin-slot, planar and ball joints, motion links, limits, interference checks, mass from the exact solids.

DETAIL F

Opens .sldprt and .sldasm

Yes, those. Parts and assemblies saved since 2015, each with its material, opened without the program that made them. STEP and Parasolid too.

DETAIL G

Files the next machine wants

STEP for other CAD, 3MF, STL or OBJ for the printer at the refinement you choose, DXF and SVG for the laser and the router.

DETAIL H

T-slot frames, checked

Lay out an aluminium extrusion frame, get every cut length with its mass and price, and check stress, deflection and buckling on a beam model.

CTwo jobs, all the way to the file

From the model to the machine.

ROS 2 and LeRobot builders

Your assembly is already a robot description.

A six-axis desk arm: a base clamped to the desk, six servos on their axes, the upper arm, the forearm, the wrist and a two-finger gripper.

Parts become links, joints become joints, and every link’s inertia comes from its exact solid and material. Drag the joints to check it, then export URDF, MJCF or SDF, or a whole ROS 2 package with a launch file.

Robot export

Laser cutters and CNC routers

Boxes that know how thick your plywood is.

A box side with finger joints along all four edges; the slot depth equals the material thickness t t thickness = 3 mm slot depth = thickness

Material thickness is a parameter: change 3 mm to 6 mm and every finger joint follows. Living hinges, kerf added at export, and SVG or DXF in the colour layers your laser software reads.

Laser and CNC

DWhere it runs

Anywhere a browser does.

Any current Chrome or Edge will do, on whatever the computer runs. The first visit loads about 13 MB; after that the browser keeps it and ProtoJoint opens at once.

LinuxUbuntu, Fedora, Arch: any desktop with a current browser
ChromeOSThe school or team Chromebook, as it is
macOSSafari, Chrome or Edge on a Mac
WindowsNo installer, no administrator rights

EYour move

Your next part starts in a tab.

Sketch it, extrude it, export it. If anything gets in the way, tell us and it goes on the drawing board.

Open the editorTell us what you need
Drag the trunk: it turns on its joint. Drag the forehead: the fillet follows, and the eye, its centre, with it.One stroke and one fillet: the eye is the fillet's centre.