When sizing a motor for an application, it is crucial to distinguish between horizontal and vertical motion axes, as each involves different load considerations and system dynamics. Here’s how you should approach each:

Before diving into horizontal vs. vertical, the core factors in motor sizing include:

• Load inertia (moment of inertia)
• Required torque and speed
• Acceleration and deceleration profiles
• Duty cycle and thermal limits
• Friction and external forces
• Mechanical losses

Horizontal Motion Axis

Characteristics:

• Movement occurs parallel to the ground
• Gravitational forces are perpendicular to motion, so they don’t influence drive torque directly

Key Considerations:

1. Inertia Matching
   Ensure that the motor inertia matches the reflected load inertia to avoid overshooting or instability.
2. Friction and Rolling Resistance
   Include all frictional components—linear guides, belt tension, and bearing drag.
3. Acceleration Torque
   Based purely on the moving mass and desired acceleration: T=J⋅αT = J \cdot \alphaT=J⋅α Where JJJ is the moment of inertia and α\alphaα is angular acceleration.
4. Load Variations
   Account for payload variations along the axis (e.g., in pick-and-place systems).
5. Backlash and Compliance
   Important if the application demands precise positioning.

Vertical Motion Axis

Characteristics:

• Movement is against gravity, so the motor must counteract gravitational force in addition to driving torque.

Key Considerations:

1. Holding Torque Requirement
   The motor must provide torque even at standstill to hold the load in position (or use a brake).
2. Gravity Compensation
   Total torque includes gravitational load:
   • Ttotal=Taccel+Tgravity
     • Where: Tgravity=r⋅m⋅g
       • r: pulley or gear radius,
         m: mass,
         g: gravitational acceleration
3. Brake Integration
   Often, an electromechanical brake is needed to hold position when power is off.
4. Motor Overload Capacity
   Sizing often includes safety factors >1.5–2x, especially for hoisting or lifting loads.
5. Failure Mode Safety
   In lifting systems, a motor or gearbox failure can lead to falling loads—safety mechanisms like anti-fall brakes or redundant systems may be needed.

Summary Table