How Much Load Can PSG High Torque Linear Stage Really Handle? – A Field Engineer’s Notes

1. Don’t Just Look at the “Max Payload” – List All Five Forces

In real operation, the stage sees much more than the part weight:

• Mass of workpiece (M₁)

• Mass of moving table (M₂)

• Inertia force during acceleration (F = m·a)

• External process resistance (cutting, pressing, etc.)

• Moment loads from off‑centre mounting

For example, a 30 kg fixture accelerated at 2 m/s² generates 60 N of inertial force. Add friction and cutting reaction, and the actual motor torque demand can be 40‑60 % higher than the static case.
My rule: write down every external force in a table, sum up the total driving force, and then back‑calculate the required screw lead and motor torque.

2. Where Does PSG’s High Thrust Come From? Match Screw and Motor Carefully

PSG stages use precision ball screws. The thrust depends on:

• Screw diameter (d₀) – larger gives better rigidity and bending resistance

• Lead (P) – smaller lead gives higher thrust for the same torque, but lower speed

• Motor rated torque (T) and its short‑term overload capacity

• Coupling and bearing support stiffness

We’ve measured on our test bench:
With the same motor, changing the lead from 10 mm to 5 mm doubles the thrust, but halves the maximum speed.
So the first design decision is: do you prioritise pushing force or cycle time? If your takt time allows, a smaller lead is often the safer bet.

3. Rail Rigidity Is the Hidden Ceiling

Many engineers focus on the screw but forget the linear guides. PSG uses high‑rigidity roller guides, but if you overhang the load more than 200 mm from the carriage centre, the side moment will significantly reduce the effective load capacity.

I use these rough derating rules in practice:

• Overhang < ½ guide span → capacity ≈ nameplate value

• Overhang > guide span → derate to 70‑80 %

• Vertical mounting → always add a brake, and use a safety factor of ≥ 2.0

4. Horizontal vs. Vertical – Night and Day

The same PSG‑120 unit can carry 80 kg horizontally at 1 m/s, but vertically I would never go above 40 kg without checking the hold‑brake and thermal behaviour.

In vertical lifts, the motor must continuously fight gravity, so the average torque is higher and heat builds up quickly. We logged a 50 kg vertical lift over 300 mm stroke at 30 cycles/min – the motor temperature rose 18 °C above the horizontal case. For long runs, you either need extra cooling or reduce the duty cycle.

5. My Three‑Step Selection Workflow

Here’s what I actually do before ordering a PSG stage:

Step 1 – Calculate the maximum driving force
Total thrust F = μ·m·g + m·a + F_ext
where μ is the guide friction coefficient (typically 0.01‑0.02 for roller guides), and F_ext is any external process force.

Step 2 – Back‑calculate the required motor torque from the screw lead
T = F × P / (2π × η)
with η = 0.85‑0.9 (ball screw efficiency).

Step 3 – Check screw life
Use the dynamic load rating Cₐ to estimate L₁₀ (million revolutions):
L₁₀ = (Cₐ / F)³ × 10⁶ (revolutions)
If the calculated life is less than 20 000 hours of continuous operation, I move up to the next frame size.

6. Three Hard‑Earned Lessons from the Shop Floor

• Lesson 1 – Micro‑stepping can be tricky
  In a vision inspection system, the load was only 15 kg, but the stage needed 0.1 mm step‑and‑settle movements. The standard stage oscillated badly due to screw backlash and inertia mismatch. We switched to the PSG high‑torque series and tuned the driver gains – problem solved.

• Lesson 2 – Cheaper upfront often costs more later
  On a horizontal transfer unit, we down‑sized to save money. After two years, screw wear caused a permanent drift in accuracy. The replacement parts and downtime cost more than the initial saving.

• Lesson 3 – Acceleration ramp matters
  A vertical application kept tripping the motor overload during start‑up. We lengthened the acceleration time from 0.1 s to 0.25 s, and the system ran smoothly without any hardware change.

7. When Do You Really Need the PSG High‑Torque Series?

I recommend the high‑torque variant when you have:

• Frequent accelerations above 1 g

• Significant overhung loads

• Long‑term repeatability requirements within ±0.01 mm

• Light cutting or pressing forces that act on the moving table

In these cases, a standard module might “just work” initially, but the high‑torque version gives you a much healthier rigidity margin. We have a dozen machines running PSG stages on our floor; the oldest has been in continuous service for three years without any screw replacement, and the guide wear is still well within tolerance.

Final Advice for Newcomers

Never order a stage based solely on the “max load” spec. Always send the supplier your acceleration profile, mounting orientation, and cycle frequency. Ask for the dynamic thrust curve, not just the static rating.

And if you have the chance, run a simple test with a load cell or monitor the motor current during actual motion – that will tell you more than any datasheet.

Selecting a linear stage isn’t a pure math problem; it’s an engineering trade‑off. The PSG high‑torque stage can carry a lot – but how much and how long depend entirely on how you apply it. Use the calculations, respect the derating, and you’ll get reliable, long‑life performance.