What It Does, When You Need It, and What to Expect
A braking resistor is an optional accessory used to reduce the spindle’s spin-down time when the VFD commands the motor to stop.
Under normal operation, a spindle takes time to coast to a stop. During deceleration, the motor effectively becomes a generator, sending energy back into the VFD. If that energy cannot be safely dissipated, the VFD will protect itself by triggering an over-voltage fault.
The braking resistor provides a controlled path for that excess energy, allowing the spindle to slow down more quickly without triggering errors.
What Our Braking Resistor Is Designed For
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Rating: 300W, 250Ω
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Purpose: Safely dissipate regenerated energy during deceleration
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Primary benefit: Shorter, more controlled spindle stop times
By default, our spindle systems are configured with a 6-second deceleration time, which is a safe and reliable value for most machines and applications.
Adding a braking resistor allows you to reduce the deceleration time, typically down to around 3 seconds, without over-voltage errors.
What a Braking Resistor Does Not Do
It’s important to set expectations clearly:
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It does not increase spindle power
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It does not improve cutting performance
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It does not fix long spin-down times caused by controller-specific behavior
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It does not guarantee identical stop times on every machine
Results will vary depending on spindle size, inertia, wiring, controller timing, and electrical conditions.
Compatibility Notes
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A V5 VFD is required for the appropriate braking resistor connector
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Customers with earlier VFD revisions will need a VFD upgrade package, which can be purchased separately
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This braking resistor does not resolve the long spin-down behavior seen with certain Buildbotics-based controllers, where spindles may coast for 20+ seconds due to controller-side logic
Recommended Deceleration Settings
With a braking resistor installed:
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Default deceleration: 6.0 seconds
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Typical achievable minimum: 3.0 seconds
While it is technically possible to set values lower than 3.0 seconds, doing so often results in ERR06 (Over-voltage at deceleration). For this reason, we recommend not going below 3.0 seconds.
The 3-second value is not a guaranteed stop time, but rather the lowest setting we’ve consistently achieved in testing without faults.
What to Do If You See ERR06
If you encounter ERR06 after installing a braking resistor, the first thing to do is:
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Increase the deceleration time to 003.0 seconds or higher
In most cases, this resolves the issue immediately without further troubleshooting.
How to Adjust the Deceleration Time
To change the deceleration setting on the VFD:
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Press the MODE button
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Navigate to parameter P0.0.12 using the up/down arrows
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Use the right arrow to move between digits
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Adjust the value
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Default:
006.0 -
With braking resistor:
003.0(recommended minimum)
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Save and exit
Always test changes with the spindle unloaded before running a job.
Is a Braking Resistor Required?
For most users, no.
A braking resistor is only recommended if:
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You want faster spindle stop times
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Your workflow benefits from quicker tool changes or pauses
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You understand and accept the trade-offs involved
The default configuration is intentionally conservative to maximize reliability and component lifespan.
Summary
A braking resistor is a helpful tool for reducing spindle stop time, but it is not required for normal operation.
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Default deceleration is safe and reliable
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A braking resistor allows shorter deceleration without faults
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3 seconds is typically the practical lower limit
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Overly aggressive settings can cause ERR06
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Stability and reliability should always take priority over speed
If you’re unsure whether a braking resistor makes sense for your setup, feel free to reach out to support before making changes.
