Should I be concerned about this...?

Bought an Anet A8 used for $60 locally from someone that couldn’t quite put it together right. Thought I’d either bring it to life or salvage it for parts. For the most part, this thing is pretty much new. The time on the printer reads less than 5 hours total.

I finally got to fiddling with it tonight when I stumbled upon this goonery:

My first instinct is to shrug it off, lose the damn screw (WTF?) and solder it like a normal person, but then I thought it might be wise to seek the wisdom of those who know better than me.

What do you think? Scrap and buy a new one? Or solder and proceed? I don’t know enough about these beds to know if that sort of thing would potentially cause a fire. Someone make me feel better about this.


Lose the screw, test the resistance, and if it’s within spec, solder the wire.
A heat bed is the nextg closest thing to a short across your PSU as it is, so there’s not much that you can do to it that’s going to make it inherently more dangerous. I’d be more worried about it warping the print bed, but it appears from your photo that this isn’t really an issue.

I would, however take a good hard look at the rest of the electronics. If that person did that, what else did he do when wiring it up?

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Soldiering those pads is really tough. The bed just sinks all the heat immediately, so it is hard to get the solder pad up to temp enough to get a good solder joint. Heating up the whole bed first helps, but it was stressful when I had to do that last.

I still have no idea why they would put a screw in there though.

Truth be told, if it was me, I would leave it as is. Like Jeff said soldering onto that hotbed is a pain, the damage to it has already been done. And in reality a conductor is a conductor. An Aluminum screw will offer less resistance than the steel. But I have used steel bolts as battery contacts in a lot of projects without issue so it should be fine… unless you are actually having some sort of performance issue that is.

They probably didn’t have a good enough solder station that could provide enough power to solder directly on the bed (I’m guessing a cheap HF single temp model)

Well at least it is soldered and does not have the famous connector that catches homes on fire. If it were me I would solder properly, but I have the tools. Being an A8, be sure to read up on safety and firmware upgrades. The original A8 came with a 1280 board with firmware than has no thermal runaway protection. Most A8 owners upgrade to Marlin to enable runaway protection. Also watch the bed fet… another common upgrade is an external bed fet.

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The two things that worry me the most are:

  • It’s got lots of stickout and is a shorting hazard.
  • The contact between the screw and the heated bed is very small. The whole board isn’t the conductor, just the pcb layer on top, touching the edges of the screw.

Nope, I would fix it. But honestly, they aren’t expensive either.

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Its your machine, but I’d lose the screw, solder, and proceed. I found using plenty of flux and tinning the wire first worked pretty well.

On my Prusa clone I’d be losing significant print area with a screw sticking out the bottom like that!

The screw was gonna get tossed regardless of whether or not I decided to keep the bed or get a new one. I decided to solder it proper. It heated right up just fine afterward. I suppose my concern was relative to the fact that the previous owner seems to have drilled and tapped a GD screw in the solder pad.

Thank you for your input, everyone. I’ll let y’all know if I end up burning my house down. :slight_smile: