Understanding Load Capacity: Step Mode vs. Continuous Mode

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Introduction

When selecting a motorized turntable, load capacity is often the first specification users look at. However, ComXim programmable turntables feature two distinct load ratings – one for step mode and another for continuous mode – and understanding the difference is critical for both performance and product longevity.

Many users mistakenly assume that if a turntable is rated for 100 kg, they can place any 100 kg object on it and operate it in any mode. This is not the case. The way the turntable moves – whether it rotates continuously or starts and stops repeatedly – fundamentally changes the mechanical demands placed on the motor and drive system.

This guide explains:

• The difference between step-mode and continuous-mode load ratings
• Why two ratings exist
• How to calculate effective load when your object exceeds the platter diameter
• Best practices for safe and reliable operation

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Two Load Ratings, Two Different Demands

ComXim turntables are rated with two separate load capacities:

Rating	Definition	Typical Value Relationship
Step-Mode Maximum Load	The maximum weight the turntable can carry while maintaining positioning accuracy in step or pendulum modes	Lower of the two
Continuous-Mode Maximum Load	The maximum weight the turntable can carry during steady, uninterrupted rotation	Higher of the two

Why the Difference?

The reason for two ratings comes down to torque and inertia.

In continuous mode, the motor spins up to a constant speed and maintains it. The primary load on the motor is overcoming friction and maintaining momentum – a relatively steady demand.

In step mode, the turntable must:

1. Accelerate from a dead stop to the target speed
2. Decelerate to a complete stop
3. Hold position precisely during the pause
4. Repeat this cycle dozens or even hundreds of times

Each start-stop cycle requires significantly more torque than steady rotation. The motor must overcome static friction (which is always higher than dynamic friction) and manage the inertia of the load during acceleration and deceleration.

Additionally, step-mode accuracy depends on the motor’s ability to stop at an exact angular position. Excessive weight can cause overshoot or positional drift, compromising the precision that makes step mode valuable for photography and scanning applications.

Important: The step-mode rating is the true limiting factor for most users. If you plan to use step mode (and for 360° photography or 3D scanning, you almost certainly will), always reference the step-mode maximum load, not the continuous-mode rating.

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The 80% Rule

ComXim recommends operating at no more than 80% of the rated maximum load for both modes:

Mode	Recommended Operating Load
Step Mode	≤ 80% of step-mode rating
Continuous Mode	≤ 80% of continuous-mode rating

Why 80%?

Operating at 80% of the rated capacity provides a safety margin that:

• Extends motor life – Reduces wear on bearings, gears, and the motor itself
• Maintains accuracy – Ensures step positioning remains precise even with slight load variations
• Accommodates dynamic forces – Accounts for additional forces during acceleration and deceleration
• Provides headroom – Allows for unexpected load shifts or imbalances

Pro Tip: If you consistently operate near the rated limit, consider choosing the next size up. The small additional investment pays for itself through longer service life and more consistent performance.

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When the Object Exceeds the Platter Diameter

The load ratings assume the object’s maximum dimension does not exceed the turntable platter diameter. When you place an object larger than the platter, the effective load capacity decreases.

Why Size Matters

Think of the turntable platter as a lever arm. When an object extends beyond the platter edge, the center of mass moves outward, increasing the torque required to rotate it. This is a fundamental principle of physics – torque equals force times distance from the pivot point.

The larger the object relative to the platter, the greater the torque demand for the same weight.

The Torque Conservation Formula

When the rotating object’s maximum dimension (or modified platter) exceeds the original turntable diameter, the effective load capacity must be recalculated using the torque conservation principle:

For step mode:

D1 × SL1 × 80% = D2 × SL2

For continuous mode:

D1 × CL1 × 80% = D2 × CL2

Where:

• D1 = Original platter diameter (cm)
• SL1 = Original step-mode maximum load (kg)
• CL1 = Original continuous-mode maximum load (kg)
• D2 = Maximum dimension of the object or modified platter (cm)
• SL2 = Effective step-mode load capacity (kg)
• CL2 = Effective continuous-mode load capacity (kg)

Note: The 80% factor is already included in these formulas as a safety margin.

Worked Example

Scenario: You have a MT400RUWPSL100ProV6 turntable with:

• Platter diameter: 40 cm (D1)
• Step-mode rating: 100 kg (SL1)
• Continuous-mode rating: 225 kg (CL1)

You want to rotate an object with a 60 cm maximum dimension (D2).

Step-mode effective load (SL2):

40 × 100 × 80% = 60 × SL2
32 × 100 = 60 × SL2
3200 = 60 × SL2
SL2 = 53.3 kg

Continuous-mode effective load (CL2):

40 × 225 × 80% = 60 × CL2
32 × 225 = 60 × CL2
7200 = 60 × CL2
CL2 = 120 kg

Result: With a 60 cm object on a 40 cm platter, the effective step-mode capacity drops from 100 kg to 53.3 kg – nearly a 50% reduction.

Key Takeaway

Larger objects reduce effective load capacity significantly. If your object exceeds the platter diameter, always recalculate using the torque conservation formula before operation.

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Real-World Application Examples

Example 1: E-Commerce Product Photography

Setup: MT320RUWPSL40ProV3 (32 cm platter, 40 kg step-mode rating)

Object: A handbag measuring 35 cm × 25 cm, weighing 8 kg

Analysis:

• The object’s maximum dimension (35 cm) exceeds the platter diameter (32 cm)
• Effective step-mode capacity: 32 × 40 × 80% = 35 × SL2 → SL2 = 29.3 kg
• Object weight (8 kg) is well within 29.3 kg → Safe to operate

Example 2: 3D Scanning of a Mannequin Torso

Setup: MT500RUWSL100ProV6 (50 cm platter, 100 kg step-mode rating)

Object: A mannequin torso measuring 55 cm across, weighing 45 kg

Analysis:

• Object dimension (55 cm) exceeds platter (50 cm)
• Effective step-mode capacity: 50 × 100 × 80% = 55 × SL2 → SL2 = 72.7 kg
• Object weight (45 kg) is within 72.7 kg → Safe to operate

Example 3: Industrial Component Inspection

Setup: MT400RUL100ProV6 (40 cm platter, 100 kg step-mode rating)

Object: A cast metal part measuring 38 cm × 38 cm, weighing 95 kg

Analysis:

• Object dimension (38 cm) is within platter diameter (40 cm) → No reduction needed
• Object weight (95 kg) exceeds 80% of rating (80 kg) → Not recommended
• Solution: Choose a higher-capacity model or reduce the load

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Comparison Table: Step Mode vs. Continuous Mode Load

Aspect	Step Mode	Continuous Mode
Load Rating	Lower (accuracy-critical)	Higher (steady motion)
Primary Demand	Acceleration/deceleration torque	Friction management
Accuracy Impact	High – excess load causes positional drift	Low – slight speed variation acceptable
Wear Pattern	Start-stop cycles stress motor and gears	Steady wear on bearings
Recommended Operating Load	≤ 80% of step-mode rating	≤ 80% of continuous-mode rating
Best For	Photography, scanning, positioning	Video, display, preview

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Best Practices for Load Management

1. Always Reference the Step-Mode Rating

If you plan to use step mode for photography or scanning, the step-mode rating is your primary constraint. The continuous-mode rating is not a substitute.

2. Apply the 80% Rule

Operate at no more than 80% of the rated capacity for both modes. This extends product life and maintains accuracy.

3. Recalculate for Oversized Objects

If your object’s maximum dimension exceeds the platter diameter, use the torque conservation formula to determine effective capacity.

4. Consider Dynamic Forces

Objects with uneven weight distribution or high centers of gravity create additional torque demands. Reduce load further for unstable objects.

5. Monitor for Warning Signs

If you notice:

• Unusual motor noise
• Slower than expected rotation
• Positional drift in step mode
• Overheating

…immediately reduce the load or stop operation. These are signs the turntable is being overloaded.

6. Choose the Right Size from the Start

When in doubt, select a turntable with a larger diameter and higher load capacity than your current needs. The flexibility is worth the investment.

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Frequently Asked Questions

Q: Can I use the continuous-mode rating for step-mode operation?
A: No. Step mode requires significantly more torque due to repeated start-stop cycles. Always use the step-mode rating for step-mode operation.

Q: What happens if I exceed the step-mode load rating?
A: Exceeding the rating can cause positional inaccuracy, motor strain, premature wear, and potentially permanent damage to the drive system.

Q: How do I know if my object exceeds the platter diameter?
A: Measure the maximum dimension of your object (width, depth, or diagonal). If any dimension exceeds the platter diameter, the object is considered oversized.

Q: The formula uses 80% – is that already included or do I add it?
A: The 80% factor is already included in the formula as a safety margin. The result (SL2 or CL2) is the recommended maximum operating load.

Q: Does the shape of the object matter?
A: Yes. The formula uses the maximum dimension, but objects with irregular shapes or off-center weight distribution may require additional reduction.

Q: How does load affect shutter synchronization?
A: Excessive load can cause positional drift in step mode, which may affect the timing of shutter triggers. For consistent results, stay well within the step-mode rating.

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Summary

Key Point	Takeaway
Two ratings exist	Step-mode (accuracy-critical) and continuous-mode (steady rotation)
Step-mode is the limiting factor	Always reference step-mode rating if using step mode
80% rule	Operate at ≤ 80% of rated capacity for longevity
Oversized objects	Recalculate effective load using torque conservation formula
Larger object = lower capacity	A 60 cm object on a 40 cm platter reduces capacity by ~50%

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Conclusion

Understanding the difference between step-mode and continuous-mode load ratings is essential for getting the most out of your ComXim programmable turntable. The two ratings exist because the mechanical demands of start-stop motion are fundamentally different from steady rotation.

The golden rules:

1. Always reference the step-mode rating if you plan to use step mode
2. Operate at ≤ 80% of the rated capacity
3. Recalculate when your object exceeds the platter diameter
4. When in doubt, choose the next size up

Following these guidelines ensures your turntable delivers accurate, reliable performance for years to come – whether you are shooting 360° product photography, scanning 3D objects, or running industrial inspection routines.

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Additional Resources

Resource	Link
Official Website	comxim.com
User Manual & Documentation	comxim.com/user-guide
Product Selection Guide	comxim.com/selection-guide
Developer Tools	comxim.com/development-kit
Video Tutorials	comxim.com/application-video-tutorial