Heatbed Connection screw burns PCB away be warned....OR2

It is unfortunate that this happened, but I cannot believe the design...
The contact point on the left side of the heatbed got so hot that it "burnt" the PCB to a crisp and melted the solder smoking allot !
I measure the bed, the resistance was spot on 1.2/1.3Ohms... no shorts.... yet the screw melted everything in its path
I see on the new design this was changed to a contact spade lug.....
It did not help tightening the screw as it only progressed deeper into the PCB

Yes the thermistor is working, the config file set to 4k7, since the bed stops heating at 56degrees as indicated... I also find this bed design poor as there are holes drilled, presumably VIAS, where the screw terminates... this is poor design as the current that flows there now have to zigzag through the holes... the new one seems much better...

Anyway I added a 3mm washer to spread the load across the remaining track .... however now the LEDs are dead as the track from the pole is now burnt to a crisp

I will at some stage solder a wire in to repair, but for now the bed heats to 56 for PLA.... wonder if it would get 110 for ABS ???

Yup
There are a few threads about this.
[forums.reprap.org]
[forums.reprap.org]

Contact support (Ian) and they'll take care of you.

Hi There
Yip I saw that, but the problem is to get it replaced if you are not in the UK, I`m in South Africa... RS electronics are TOPs but do not keep stock of parts like the HEAT BED...
Designing my own seems to be a good alternative and pretty simple but pricey...

*Hope fully IAN will ship free of charge
Tx Ben

Edited 1 time(s). Last edit at 05/30/2015 06:42AM by BenBB.

BenBB

I replied on the other thread as well... We'll replace this under warranty. This is the text we normally send out to customers who have this problem:

Sorry you've had problems with your heated bed. We've had a number of reports of failure of this style of heated bed. Usually, it's due to poor connections overheating. Unfortunately, it's not always obvious what causes the problem; it can be the brass screw was not soldered sufficiently, the nuts holding the wiring loom were loose, the crimp on the end of the wire was not well-connected, or the wiring was not secure, and allowed to 'hinge' at the connection, so loosening it or fatiguing the wires. The outcome, however, is clear; that a poor connection of the heated loom to the bed creates heat, and burns out the connection. This is not a short circuit; the connection fails. This should mean that it fails 'safe', and the voltage is disconnected, though it is often accompanied by some burning.

This has led us to produce a new version, with soldered-on tabs; see the '528.4 onwards' tab, here: [reprappro.com]
This is a much simpler and more robust connection, though it meant redesigning the heated bed. This heated bed PCB is a direct replacement, but requires a new MDF insulator and heated bed loom. I am happy to send these parts to you, under warranty.

Alternatively, if the solder pads on the heated bed PCB are still okay, and if you have the facilities and skill, probably the quickest fix/alternative mounting is to solder the ends of the bed loom onto the PCB, like we do with the Mendel: [reprappro.com]

Send me an email, to support@reprappro.com , with a brief description of the problem, and perhaps a link to this thread. Please send me your invoice number if you ordered your kit direct from us, or if you ordered from RS Components or other distributor, as we don't have access to their customer database, please send me your full name and address, and a copy of your invoice (pdf is fine) as proof of purchase.

Ian
RepRapPro tech support

Edited 1 time(s). Last edit at 05/30/2015 01:21PM by droftarts.

And yes, warranty replacement are include postage. If you want to order any other parts, we'll send them with the warranty order, with free shipping.

Ian
RepRapPro tech support