← Robot list · Learn the basics
All three joints slide in a straight line. Move a slider, or type a value in a number box.
Each square is a sliding joint (prismatic), and the grey bar is its full travel. The orange line is the path from the base to the tool: first along q1, then q2, then q3. Axes: x red, y green, z blue. ⊙ points at you, ⊗ points away. Change the View to see the machine from the front, from above or from the side.
Frame i is attached to the axis of joint i+1.
Each row is: Ai = Rz(θ) · Tz(d) · Tx(a) · Rx(α).
For a sliding joint, d is the variable. Orange numbers are the current values.
Frame i is attached to the axis of joint i.
Each row is: Ai = Rx(αi−1) · Tx(ai−1) · Rz(θ) · Tz(d).
The last column is the position of the tool in the base frame {0}.
x0 = q3 + 0.15 (x0 points DOWN) y0 = q2 (across the machine) z0 = q1 (along the long rails)
This is the simplest kinematics of all robots: each joint is directly one coordinate. That is why gantries are so easy to program and so precise. The frame {0} is placed so that its z axis points along the first rail, which is why z0 = q1.
3D printers, CNC routers and milling machines, laser cutters, plotters, laboratory pipetting robots, palletizing, warehouse storage and retrieval, gluing and dispensing, and inspection machines. The work area can be as big as you want: just make the rails longer.
Strengths: very precise and rigid, a large workspace, and the simplest maths. Weaknesses: the machine is big compared to the area it works on, it is slower than a SCARA or a delta, and the tool can't tilt or rotate unless you add extra axes.
Yes, a pinch gripper (pince) works, like the one in the 3D model. It always points straight down. If the part must be turned, add a rotating axis to the tool. Other tools: