HMS 1A00-1200-0002-0002: Rack Calibration Failed, Marker Feature Not Detected
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HMS 1A00-1200-0002-0002 means the camera worked but could not find the visual marker on the rack, and Bambu asks whether that marker is damaged or obscured by dirt. The marker is a physical reference the machine measures against, so anything covering it stops the calibration outright.
This is a narrower fault than it looks. One small surface is at issue, and you can see it.
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Find the marker and look at it
Power the machine down and inspect the reference pattern on the rack under good light. You are looking for filament dust across it, a smear from a finger, or a scuff that has taken part of the pattern away. A marker that is merely dirty cleans up; one that has been scraped does not.
Clean it the way you would clean a lens
A lint-free swab with isopropyl alcohol lifts dust without dragging it. Avoid paper towel, which leaves fibres across exactly the surface the camera is trying to read, and avoid anything abrasive, because the pattern is printed rather than engraved on most mechanisms of this kind.
Then check what the camera can see
A clean marker the camera still cannot find suggests the problem is at the other end. Dust on the camera window, or a bright light across the chamber, both reduce contrast to the point where a pattern stops registering. The abnormal-data version of this fault is HMS 1A00-1200-0002-0001, where the image could not be interpreted at all.
Why HMS 1A00-1200-0002-0002 matters more on a tool changer
On a single-hotend machine a bad calibration costs you a first layer. Here it costs you the accuracy with which a hotend is placed into a mount, and that failure mode is mechanical. The machine refusing to calibrate is cheaper than the machine calibrating wrongly.
Keeping it readable
Handle the rack by its frame rather than across the marker, and include the pattern in whatever cleaning routine you already run. The calibration sequence in general is in calibrating a 3D printer, and the machine itself is reviewed in the Bambu Lab H2D review.
HMS 1A00-1200-0002-0002 FAQ
Can the marker be replaced?
On most assemblies it is part of the rack, so a damaged one means a rack part rather than a sticker.
Will the machine print without calibrating?
It should not be asked to. Slot positions come from this measurement.
Does lighting really stop a pattern being found?
Yes. Glare across a printed pattern removes the contrast the detection depends on.
Is this the same as homing failure?
No. Homing finds zero mechanically; this finds the slots visually — see HMS 1A00-1100-0002-0002.
Mechanical faults in the rack report separately from visual ones. HMS 1A00-1200-0002-0008 means the tool lock rod is jammed, usually by a purge fragment in its channel.
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