Upgrading from Smoothie to Duet 3: Facing heavy M400 sync latency
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ORIS ORIS
Jul 19, 2026, 7:49:49 PM (2 days ago) Jul 19
to OpenPnP
Hello everyone,
I have 5 years of experience with OpenPNP running flawlessly on an old Smoothieboard v1. Recently, I upgraded my high-speed machine to a Duet 3 MB6HC (RRF 3.6.3) with external Panasonic Minas A6 AC servos.
The issue is that Duet introduces a painful 50-60ms fixed latency/overhead every time M400 is called to sync the queue. On my old Smoothie, the identical move and sync block (G1 + M400 + M114) took exactly 232ms (pure physical travel time). On the Duet 3, this exact same test sequence takes 280ms, causing visible stuttering and chopping on every single stop.
Has anyone successfully optimized Duet 3 / RRF for high-speed OpenPNP? Is there a known way to reduce or get rid of this fixed M400 delay on RepRapFirmware?
Any help from someone who moved from Smoothie to Duet would be highly appreciated.
Thank you!
I have 5 years of experience with OpenPNP running flawlessly on an old Smoothieboard v1. Recently, I upgraded my high-speed machine to a Duet 3 MB6HC (RRF 3.6.3) with external Panasonic Minas A6 AC servos.
The issue is that Duet introduces a painful 50-60ms fixed latency/overhead every time M400 is called to sync the queue. On my old Smoothie, the identical move and sync block (G1 + M400 + M114) took exactly 232ms (pure physical travel time). On the Duet 3, this exact same test sequence takes 280ms, causing visible stuttering and chopping on every single stop.
Has anyone successfully optimized Duet 3 / RRF for high-speed OpenPNP? Is there a known way to reduce or get rid of this fixed M400 delay on RepRapFirmware?
Any help from someone who moved from Smoothie to Duet would be highly appreciated.
Thank you!
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