Here’s a problem I found that my mini had and the problem and solution to fixing it. It’s A.I. written being as I had a chat with chatgtp about after I solved it and it recommended that I post this issue so I asked it to write up this post. If you don’t like AI posts, that’s fine, but here’s a problem and the solution.
I wanted to document an issue I ran into with a recently purchased A1 Mini + AMS Lite, because it took a lot of observation to diagnose and I suspect others may be hitting the same problem without realising why.
This is not a calibration or firmware issue — it’s a mechanical interaction problem.
Background / context
I own multiple A1 Minis (four total), three of which are paired with AMS Lite units.
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Two older A1 Minis came with longer grey Bowden tubes
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A newer A1 Mini (purchased recently – last few months) came with shorter white Bowden tubes
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Visually, the white tubes look neater and more compact
However, this newer machine was the only one that consistently failed bed levelling.
Symptoms
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Bed levelling would fail repeatedly
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Failure only occurred on the far left side of the bed (X-min)
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The printer would:
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Sit there hopping up and down
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Retry probing multiple times
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Eventually throw a bed levelling / probing error
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Bed levelling worked fine everywhere else
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Prints were otherwise normal if levelling succeeded
At first glance, it looked like:
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A bad bed
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A Z issue
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Or a probing sensor problem
But none of those were actually the cause.
Key observation (this took time to notice)
I sat and watched bed levelling run 20–30 times.
What finally clicked was this:
When the toolhead moved all the way to the far left, the short Bowden tubes were pulled tight because the AMS Lite was mounted on the right side of the printer.
At that point:
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The Bowden tubes were under tension
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That tension was pulling the toolhead slightly to the right
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This only happened at maximum left X travel
To test this:
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While the printer was “stuck” hopping during probing
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I physically slid the AMS Lite slightly left
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Bed levelling immediately continued and completed successfully
That confirmed the Bowden tubes were involved.
Root cause (technical explanation)
The A1 Mini uses force-based nozzle probing for bed levelling.
That system assumes:
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The toolhead is force-neutral in X and Y
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The only force detected during probing is vertical Z contact
With the short white Bowden tubes:
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At far left X position:
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The tubes straighten
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Elastic tension increases
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A lateral force is applied to the toolhead
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That lateral force:
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Biases the load cell
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Reduces or distorts the vertical force signal
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Causes the firmware to retry probing endlessly
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From the printer’s perspective, it looks like:
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Inconsistent Z contact
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Sensor noise
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Or mechanical instability
In reality, it’s Bowden-induced side load.
Why this only affects some setups
This problem depends on several things lining up:
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Shortened Bowden tubes (white version)
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AMS Lite mounted on the right side
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Full X-min probing location
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Force-based bed levelling
If the AMS is very close to the printer, or mounted differently, the issue may never appear — which is probably why this isn’t widely reported.
The fix (permanent)
I replaced the short white Bowden tubes with longer Bowden tubes, matching the length used on my older A1 Minis.
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Same routing
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Same AMS position
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Only difference: extra length / compliance
Result:
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Bed levelling has been 100% reliable
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No probing failures
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No hopping at X-min
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Issue has never returned
Yes, the longer tubes look a bit less “tidy” — but functionally they are far more forgiving.
Takeaway
If you have:
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A newer A1 Mini
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White, shorter Bowden tubes
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AMS Lite mounted on the right
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Bed levelling failures specifically on the left side
Check Bowden tube tension at full left X travel.
Anything that applies lateral force to the toolhead during force probing will corrupt Z measurements.
Hopefully this saves someone else a lot of head-scratching and repeated failed levelling cycles.
If others can confirm tube length differences or similar behaviour, it would be useful to compare notes.
