Printer refuses to move

Sometimes my (reprappro)printer seems to refuse to move(its not mechanically stuck), or heat anything up. This happened before, i assumed it was related of overheating of the electronics somehow, which i fixed by making the end of the 12V power into the Melzi fit better, the issue disappeared then. But now it does the same without apparent heating up.

Turning off the power, waiting a (longish)while and restarting allows it move, shortly but then it doesnt anymore. It seems to be when turning on the hot end or bed. I think it should be patient to see if it actually happens that way. Resistance measure across those two seem okey. (2Ω,8Ω)

There sometimes seems to be a sort of a 'thunk' when it starts to refuse..

I think it is some electronics issue.

If the Mega has died, then you should see several issues:

1) Temperatures don't update
2) Computer does not connect to the board
3) Heaters don't turn on and off under computer (or LCD) command.

If you can do any of those things, the firmware is still up and running. If they all fail, your CPU may indeed have stopped running.

First step is normally to grab a volt meter and start checking voltages. See if you still have adequate power to the board. If your power supply is dropping to (say) 7V that would explain what you see.

Pretty sure the mega hasnt died I can connect to it, output in attachment. All axes move, i waited and the axes kept moving as they should. Then i turned on the bed, the bed light went on only shortly, and then nothing moved. (no thunk) Hmm i measure 4,2V on the top of the power inputs.. (when motors not moving)

Straight from the power supply I read 12.4V. Maybe it loses power or has some sort of short regarding the bed.. I cannot find a particularly hot spot too.. I think i should take out the wires for the hot bed and make sure nothings is wrong there.. Over the power supply i measure a resistance 40kΩ, more than enough.

Input wires to the Ramps should be around 12v, if not you have a problem in your PSU or the wires to the ramps

Measure this at the ramps when the motors are moving and when the heat bed is no, I,e on load

Measure the same terminals on the PSU, on load.


It sounds like a wiring fault, I.e loose connections, or broken wire etc.

> It sounds like a wiring fault, I.e loose connections, or broken wire etc.

Embarrassingly, looks like that was exactly what is was, one of the things terminal screws was loose some. At it was the one that was too fat to fit properly before too... I dont get how I missed that, sorry for that.(as an excuse i accidentally hit 'post message' before i was done thinking it through..)

I dont get how it appeared to go wrong right when you turn on the heated bed..

@Jasper1984

No worries.

I think we all post stuff that in hindsight is about an obvious problem that we've overlooked ;-)

Let's see, it's been .... ummm .... errrr.... 13 hours that I've been running without having a wire fall out like that...

The connectors on the boards are designed for a single piece of wire. The lazy Bob approach of stuffing multiple wires in there is not what they are intended to do. They also work a lot better with solid wire than with stranded. Again, we don't tend to use solid wire. There are fancier connectors with custom crimpers associated with the pins on them. They cost more / are larger. They also have their issues ...

Perhaps we should be soldering the power wires onto the Ramps board.

My heat bed wires are so thick I had trouble squeezing them into the connector.

I need to tidy up my wiring and mount the 12v PSU properly, so I think I will solder the power input wires to the ramps, to save problems later

Yes we could solder the wires on. Let's see 20 hours since they fell out of the connector. It's been about 5 hours since a solder joint broke on the heated bed ....

The only way I know that's really better are swaged lugs on all the wires. Put screw terminals on each end of every connection. One terminal per connection. It works, it's worked for a long time. If you ever look at how they wire a battleship, that's the approach. We're after something a bit lighter and don't have quite as much money (or space or "free labor") as they did. We're also doing a lot of this on the fly. What we have is a very normal design, it works ok, most of the time, if done carefully.