So today our ramps 1.4 heated build plate terminal exploded on our Prusa i3. I did some googling around and apparently this is a fairly common problem caused by movement in the heater wire gradually degrading the connection at the screw terminal until the resistance increases enough to pop the terminal.
This is the second time since I’ve started playing with 3d printing that I’ve run into a major (almost dangerous) hardware failure due to parts being selected that are inappropriate for use purely to save a few bucks. This could have been avoided with a proper socket designed for moving connections or some other design.
I’m hoping the rest of the board is ok and can replace it with an A98105-ND from digikey. I think I’ll probably take thick wires off the terminal block to an external terminal block that i’ll let loosely tie to the frame, that should let it take up the movement. Either that or get some proper high ampage connectors.
The problem is you were allowing movement in that socket. Those are not meant for that kind of thing. Movement on any connector without strain relief is a big no no - this is not “hardware failure due to parts being selected that are inappropriate for use purely to save a few bucks.” this is user error.
Well, the connector is absolutely adequate for the task it’s supposed to do (at least for the hotend). The real problem behind this (and i see this a lot on other 3D printers) is that people don’t use proper strain relief and wire guides. Having wiring move right at the connector or at any other sharp bending point is a guarantee for failure either way.
Well this is very true, but when you sell this setup as a kit and don’t even include any advice on what to do with wires this sort of thing will happen a lot.
Its easily solved with an appropriate connector, or with appropriate advice in the rest of the kit to secure the wires going into the terminal. However on a standard prusa i3 frame there is nowhere to secure the wires short of taping them to the frame (liable to fail) or getting massive cable ties. Really though even with cable ties these wires will move and this failure will still occur.
Those type of screw terminals are usually only rated for 8-10A. A decent heated bed will draw around the 10A mark (eg: PCB Mk II, 200x200mmm), and speccing a connector that is “just barely capable” is a problem.
IMO RAMPS (as default) has a number of basic flaws (some tracks not thick enough, PTC fuses, very sub-par spec FETs, etc), but because it hasn’t had a revision in ages, all the cheap places are simply churning them out, with a lot of sub-standard parts (like connectors). I’ve even seen one place replace the FETs with a sub-standard part (handles less current and has a higher RDS(on) value @ 5V) because they couldn’t get the original anymore and obviously thought “Oh well, that’ll do”, without actually looking at what newer designs were using.
There’s a similar problem at the other end of the heated bed wire. There’s a significant stress point where the wire is soldered to the bed, any advice on how to solve that one? Can’t exactly secure the cable for that end.
@Stuart_Young very interesting. So you’re saying these boards have substandard connectors on? Perhaps that would explain the blow out more than movement breaking it since honestly we’ve only had about 10hrs of printing on the Prusa so far.
What board are people recommending now? I’ve been eyeing up the Azteeg X3 for a while…
@Charles_Reiche Haha…easier said than done now that the board has exploded. Once again the problem with RepRap…all solutions to fixing a 3d printer require a 3d printer!
The heated bed wiring and heated bed thermistor can both be zip-tied to the MDF frame easily - drill two holes, run a small zip-tie through them, then zip-tie down the wire to act as strain relief at the front of the bed. That’s what I do on that side.
As to your comment about “the problem with RepRap” being that “all solutions to fixing a 3d printer require a 3d printer”:
2a) You’ve got it easy. At least there are people with 3D printers around who can help you out. When I built my Mendel (right after it was released), all there were were a handful of RepRap Darwin people out there, some Makerbot Cupcakes (maybe 300 of them at most scattered around the world), and $50,000 machines that noone had access to.
2b) You have a self-replicating 3D printer! Granted it shouldn’t have failed for you after 10 hours (something seems wrong there), but in general, printing a second printer provides a great way to keep both going! Originally it was said that after printing your minimug (and before printing two sets of printers for friends for no more than the cost of a case of beer), one of the first things you print was supposed to be a complete set of spare parts that you put in a shoe box, which you put in the closet. If the printer ever breaks, you fix it, immediately, print a replacement spare part, and put them back in the closet. That’s a bit outdated now because newer models mean not always having to print out the exact same machine, so instead of a box of spare parts, I have a second printer that can print as many spare parts as I need.
RAMPS 1.4 is a great board. Haven’t had any problems with mine, nor with my RAMBo. They’re way better than the modified Makerbot electronics we all used to have to make in the beginning.
@ThantiK That connector you linked is definitely rated for 15A (and a good choice as a replacement), but the ones on the board, while similar, may not be the same connector. Similar, yes, but not necessarily the same. I see lots of connectors of the same type that are only rated for 8-10A, and some of the cheap makers of boards tend to cut corners, thinking “it looks close enuff”. The other problem is that a dodgy manufacturer can skimp slightly on the type of metal or the thickness of plating and it alters the specs of the connector quite a bit.
It is good practice to crimp all wires with ferrules before putting them into screw terminals. Saves you a lot of trouble. If you lack the tools for that, you can also infuse them with a bit of solder to make them much more stable.
@Stuart_Young agree with that. The terminal we have there is clearly not the one linked on digikey.
@Robert_Koppl that’s great advise. Definitely should get some ferrules before I hook this up again.
@Jeff_Keegan unfortunately we have the aluminium frame which is a bit less easy to alter but I see your point.
We definitely should not have had this failure so early. We have been trying to print all the replacement parts but haven’t yet got a full set out of it due to suffering lots of jamming issues in the j-head and Greg’s wade extruder. Its first on the list though!
Sorry you’re going through problems… Hang in there! On the bright side, this is one of those problems where you KNOW what’s wrong! So at least you’ve got that going for you… …which is nice.
@Jeff_Keegan very true. This is far easier to solve than most issues.
Just got a little frustrated with yet another failure. Our first printer was a replicator 1 dual. This worked for about a month then the board blew for a common fault and MakerBot have basically given up on fixing it and just ran the support request out till we got bored of waiting for them to help us fix it. Really not having much luck with 3d printing thus far!
I’m determined though so we will get there this time!
So at least you’ve got that going for you… …which is nice.