Dual-drive synchronized gantries
"Two synchronized axes controlling Y" is a classic gantry request, and the right answer is a topology, not a bigger motor. Here's how the engine builds and sizes it.
What dual-drive means
A bridge wide enough to rack under a single-sided drive gets two actuators, one on each side, driven in sync: XX′Y in the engine's naming (two X actuators carrying a Y bridge), or its mirror for a dual-Y. The two motors must share a command and, ideally, a controller axis pair that enforces synchronization — the BLC-4T and BLC-4TC controllers support paired axes for exactly this.
How it's sized
The moving mass on the dual axis is the payload plus the bridge actuator plus any Z actuator riding on it — the engine computes those from catalog mass formulas (an SBA45 Y at 500 mm with a 3:1 gearhead is about 2.5 kg; an LSA45 Z about 1 kg). Each of the two motors is sized for half that total. For 3.5 kg of payload on an SBA45 gantry the per-motor share is roughly 3.3 kg, which an N17-1 stepper with a 3:1 gearbox carries at several hundred percent torque margin.
H-bot and CoreXY
An H-bot moves a single carriage with two stationary motors through one belt loop; it's lighter but couples the axes and loads the belt diagonally. The engine's gantries are Cartesian dual-drive, which keeps each axis independent and makes the controller's job simple. If you have a true H-bot requirement, say so — it is quoted as an engineered system.
Spacing and rail gauge
The X–X′ spacing follows the selected Y actuator's overall length minus a mount margin (for a 500 mm SBA45 Y, 580 mm), not the requested travel. The engine derives it and prints the arithmetic in the assumptions panel so the spacing on the drawing matches the spacing in the quote.
Size it yourself in about a minute
Type the task — payload, travel, speed — and the Engineering Decision Engine returns a validated, priced 3D system with the torque margins, inertia check, and cycle-time math shown. Free to design and quote.
Frequently asked
Do I need a special controller for two motors on one axis?
You need a controller that can drive a paired axis in lockstep. The BLC-4T (stepper) and BLC-4TC (servo) 4-axis controllers support this; the engine adds the right one to the BOM.
Can a dual-drive axis use one motor with a cross shaft?
Mechanically yes, but a cross shaft adds inertia and compliance over long spans. Two synchronized motors are the standard for gantries above ~500 mm bridge width.
How is the moving mass split?
Each motor is sized for half the total moving mass (payload plus bridge and Z actuators), and the result is shown per motor in the sizing block.