Reprapdiscount Ramps 1.4 Fire - Root Cause???

Hi, I purchased this Ramps 1.4 board stack from Reprapdiscount. It was used about 4 to 5 months, then caught fire. Is there a known defect in the Ramps 1.4 boards? The fire is on the Heat Bed Circuit, and a Prusa MK1 heat bed is used, that is in good shape with a good resistance.

Here are some pics: [www.flickr.com]

Any answers would be greatly appreciated. I just want to make sure it doesn't happen again.

Not sure it's the root cause, but one issue with RAMPS is that the PTC fuses get quite warm, and they're pretty much directly on top of the place where the Arduino's regulator is. Also nearby is the heated bed FET, which if it's the default FET, can generate quite a bit of heat as well.

That said, another thing that can happen is that the metal part of the USB socket (which is grounded) can touch tracks on the bottom of the RAMPS board if there is not enough height in the headers (which seems quite common as people put ordinary headers on them, instead of slightly longer ones). This could cause a direct short between 12V and Ground. I always put a few layers of tape on the USB socket "just in case" to avoid such issues. The PTC fuses are slow, and may not have kicked in fast enough to protect things, which is why I put in real fuses. Also of note, obviously the PSU doesn't seem to have reasonable over-current protection, or it would have cut out due to too much current, hopefully without such damage.

I had a very similar thing happen with the same equipment--though it looks like I might have caught it a little quicker. I strongly believe it was caused by loose heated bed wires on the terminal block.

Regards,
Brian

Based on the main char being around the heated bed connectors, they are the most likely source. You would need to do some cross sections to be sure. If that is the source of the fire there still are multiple possibilities. The same cross section process would help sort them out. Either the connectors were not tight enough, the wire was to small, or the connectors were defective.

I agree with uncle_bob on this. Based on the pictures, the problems occurred right at the point where the hot bed connects to the ramps. You're carrying a lot of current through that connection. Those screws need to be TIGHT. If the connection is at all compromised, you won't have good current flow and it will just get hotter and hotter. Another thing to consider here is, if you assembled your own ramps, the solder connections between the connector and the ramps. You should be generous with the solder here - or at least don't be frugal. A connection's ability to carry current is directly related to the cross section through which the current has to flow. If you have a solder joint that used a sparse amount of solder, the cross section will be minimized, and current flow will be impeded.

the problem is caused by a design defect in the RAMPS 1.4 PCB layout. it's clearly visible without even needing a magnifying glass. i have documented this flaw on the wiki page and created a video which describes it in more detail if it is not fully understood. [reprap.org]

the problem NEEDS to be fixed - urgently - in the PCB - and the person responsible for the RAMPS 1.4 repository NEEDS to be told to update to a new revision so that people stop manufacturing and selling such dangerous product. one company in canada has been banned already by the FCC from selling *any* product through their website after one of their customer's house burned down thanks to this design flaw.

if you have one of these incredibly dangerous products you can "fix" it by soldering heavy-duty copper wires onto the underside of the PCB to bolster the current-carrying capacity, which is currently limited to somewhere around 6 (six) Amps assuming that a 10 degree temperature rise is acceptable.

You cant even read a date stamp.... replying to threads 5 years old!


You have no idea what happened in this case. RRD redesigns boards.. so It is unknown if the flaw you like to harp on about is even present.



RAMPs is open source.. you want it fixed, you fix it!

Please stop whining about it everywhere and actually help.

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Dust
You have no idea what happened in this case. RRD redesigns boards.. so It is unknown if the flaw you like to harp on about is even present.

Gonna neco bump this again, sorry. I noticed that issue lkcl mentioned on all the ramps boards I have. Looking at the full size photo of the bottom of Beekeeper's ramps board, it appears to have the same tiny traces on the power pad's thermal isolation as the reference CAD design (can see it pretty well on the fuse pads and one of the bed power inputs). Cannot tell if it may have had any role in the failure as what remains of the terminal pads is obscured by soot.

This issue (if its even an issue) is not part of the design

These thermal isolations are added by the design software such as eagle, if you use something else they are not there.
eg [easyeda.com]

Others way smarter than I have done the maths and the thermal isolation is not an issue as there is such large amount of copper right next to them that heat cannot build up from that source.

The reason the boards catch on fire is on cheap boards the connectors are under rated for the 11+ amps current and user errors such as wire that is to thin, or soldering the ends of the wires or not tightening down the connectors properly

Edited 2 time(s). Last edit at 08/28/2018 08:06AM by Dust.

... most likely this sort of malfunction is caused by tin-plating of the wire ends - when pressing the wires into the screw terminals, it's first all OK ... but with time the tin gives way and the connection between pad/screw and wire surface starts reducing and oxidizing.

Given the amount of current, flowing through the connecting surface, it's only matter of time, when it starts fuming

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Viktor
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Call for the project "garbage-free seas" - [reprap.org]

In my opinion!
There is a basic flaw with any High Current component designs that do not allow for heat sinks on power components where heat and fire are known to occur.
In this practice of making money they also skimp on wire size, making them a distarous combination for trouble.

That is why I decided to add the Addition of heat sinks and fans to better protect my 3D Printer
Remember this is just my opinion!

I purchased a 3D Printer and the controller did not have heat sinks on the power mosfets, The hot-bed and Hot-end mosfets got so hot that you could not touch them without getting burned,
an at this time decided to add a simple heat sink of my own design with all the TO-3 packages.




OK so the design is a simple straight aluminum Bar. Ha; I also designed and added a Snap shut controller case and a cooling fan to the controller case.
Shortly after I released this design on the forums as open source, the company released the next version 3D Printers that included a separate metal controller case with fan.
Today the new controller has surface mount components an all the driver components have a dedicated heat sink affixed.



As you can see in the image the Heat sink design is simple yet it provided enough material to keep the mosfets from overheating.
It consisted of an aluminum bar long enough to span the distance of the mosfet footprint, Along with an insulating TO-3 packages for the four components.

Before installing this modification could not touch the mosfet without burning myself, an after could barely determine the mosfets were getting warm.
Have sense installed stick on heat sinks for all the stepper motor driver chips, not seen in the above image.

Edited 5 time(s). Last edit at 08/28/2018 12:40PM by Roberts_Clif.

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Computer Programmer / Electronics Technician

the ramps is actually designed to have an admittedly small heat sink on the bed mosfet

99.995% of china clones omit this

In the images that started this thread, you can see the heatsink.

Somehow missed the image above,.

Still with all the under rated components in my 3D Printer I would today still purchase the Two I own again.

Edited 1 time(s). Last edit at 08/28/2018 12:51PM by Roberts_Clif.

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Computer Programmer / Electronics Technician