As you might be aware BambuLab issued a recall for the BambuLab A1 3d-printer. In particular, the issue is the mains-voltage (230V AC) heat bed cable.
As a resolution, they offer two solutions:
- Ship the entire printer back to them and receive a replacement printer.
- They mail a new cable and you install it.
What BambuLab doesn’t mention at all is the test according to EN 50678 (Verification of the effectiveness of protective measures of electrical equipment after repair). Unless you can perform this test I would recommend choosing the printer replacement.
How so? There are a number of other printers that also use mains voltage to heat the bed without issue. As your bed size and thickness grows, running stepped down DC makes less and less sense.
Unless the heated bed is UL listed, I wouldn’t trust a live high voltage heater in my house. And I might not touch it unless the printer is unplugged.
They already undersized the wires to save money. Not a great start to gaining trust for a high voltage device.
The Voron printers are a good example of conservative design philosophy. Trident and v2.4 both use AC mains because the bed is relatively stationary. Voron V0 uses DC because it is a small bed. Voron Switchwire uses DC because it is a bed slinger design and moves around so much.
Bingo!
With lower voltage DC you can only set the house on fire. With high voltage AC you can set the house on fire and electrocute people. In a safety oriented company you’d try to limit the parts of the device carrying 230V (or, more generally: if your device has dangerous bits, you try to keep those bits in as few places as possible, as that limits teh amount of places you need to keep safe). Now obviously this has limits - like the mentioned bed size - but I don’t think we’re yet at a point where this should overrule safe design principles.
I haven’t seen a bambu printer myself yet - but given that the cable is undersized and not protected against side effects from bed movement I’d bet they also skimped on on making everything carrying 230V safe - in which case this is a cheaper design. I’m reasonably confident that a safe 230V heating design for a printer that size would not give you noticeably cost savings over a DC design, if at all.
I’m certainly not trying to vouch for the safety of Bambu’s designs and am only coming at this from owning/building a 350mm^3 Voron 2.4 that uses mains voltage to heat its 8 pound 355mm x 355mm x 8mm bed. Granted, my 2.4 has a fixed bed and the A1 doesn’t.