Start with the movement, not a preferred kilowatt rating
For a rotary axis, state the load inertia, angle, move time and dwell. For a linear axis, provide mass, travel, speed, acceleration, orientation and the transmission. Add process forces, friction estimates and the number of cycles per minute. If the information is incomplete, explain what is known and which assumptions need checking.
Sizing a replacement may also involve the existing motor and gearbox codes. The old nameplate is a useful reference, but it does not prove the original equipment was correctly sized or reveal how the machine’s duty has changed.
Separate continuous duty from short peaks
Yaskawa’s sizing material identifies torque, speed and inertia as central inputs. A short acceleration peak and a long holding period affect the system differently. A simple average torque can conceal heating, while one maximum torque value says little about the repeated duty.
Use the RMS torque calculator to combine known torque-and-time segments. It produces a preliminary thermal comparison, not an automatically approved motor. Each operating point also needs checking against the relevant torque-speed curve, peak duration and installed thermal conditions.
Information that can change the answer
- A vertical load or externally applied force during a dwell.
- A changed gearbox ratio, screw lead or efficiency assumption.
- A narrow mounting envelope or a shaft that also carries external loads.
- A battery supply whose available voltage changes during use.
- Limited cooling, high ambient temperature or a sealed enclosure.
- A holding brake, external feedback or a preferred control network.
The complete servo selection guide covers the calculation sequence. The point of a sizing enquiry is to turn these requirements into a proposed configuration with explicit assumptions, rather than repeat a generic motor comparison.
Send a profile that another person can follow
A small table or sketch is often enough to start: move, accelerate, process, return and dwell, with time and load for each step. Identify simultaneous motions and whether quoted process forces occur at maximum speed. Do not add separate worst-case values together without explaining whether they actually coincide.
For quotation, include quantity, expected annual demand, deadline and the motor, drive or mechanics already selected. We can discuss Motion Control Products and other supply-network options where suitable. A final selection should be confirmed against manufacturer data and the machine design; any detailed engineering deliverables or commissioning support must be agreed for the enquiry.
Turn the requirement into an enquiry
Send the application, quantities and deadline, plus any existing model codes. We can discuss the original part, alternatives or a matched package. Compatibility, availability and supply arrangements are confirmed for the specific enquiry.
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