HMS 0300-0A00-0001-0004: external disturbance on heatbed force sensor 1
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HMS 0300-0A00-0001-0004 means force sensor 1 saw a push that did not come from the nozzle. The machine is weighing a very light touch, so anything resting on the bed, leaning against it or still stuck to it becomes part of the measurement. This is a measurement being spoiled rather than a component failing.
Affected machines: X1 series. Levelling here works by touching the plate and weighing the contact through three sensors under the bed. That makes it precise and it also makes it sensitive to anything else pressing on the same structure.
Where to buy
What usually leans on a bed
A print still attached. The most common by far. A part left on the plate from the last job, especially one near an edge, carries force into the bed when the nozzle touches nearby.
A cable. A filament tube, a camera lead or a cable tidy that has slipped and now rests on the moving bed. It weighs almost nothing and it is still enough.
A hand. Levelling runs at the start of a print, and people lean on the machine to watch. If the code appeared while you were standing over it, try again without touching anything.
The bench. A wobbly table transmits every movement in the room into the measurement, which is why this code and the vibration homing fault often appear together.
Levelling aborts and the printer reports an external disturbance on a force sensor
A print left on the plate, a cable resting on the bed, contact during the run, or a wobbly bench
- Clear everything from the build plate, including small pieces near the edges.
- Look underneath the plate and around the bed for a cable or tube that has fallen against it.
- Check that the filament path does not pull on the machine as the toolhead moves.
- Make sure the printer sits on a solid, level surface that does not flex when you lean on it.
- Start levelling again and step away from the machine while it runs.
- If it still reports a disturbance on an empty, clear bed with nobody touching it, run it with the door closed to rule out air movement.
Do not repeat the run while adjusting things mid-cycle. Each attempt has to be clean to mean anything, and half the reported cases of this code are somebody holding the machine steady while it measures.
The related readings are low force sensor sensitivity and homing failed from vibration. Our page on bed levelling explains what the measurement is for, and the troubleshooting index covers the rest.
HMS 0300-0A00-0001-0004 FAQ
Is a sensor broken?
No. It detected a real force that should not have been there, which is the sensor working correctly.
Can I lean on the printer while it levels?
No, and that is a surprisingly common cause. Step back and let it run.
Does a wobbly table cause this?
It can. The measurement is light enough that bench flex shows up in it.
Why does it name sensor 1 specifically?
Because that is the sensor that saw the disturbance, which tells you roughly where on the bed to look.
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