RAMPS Board caught on fire?

I finally setup my 3d printer which is a RepRap Prusa Mendel i2. I purchased my kit from mixshop.com. Yesterday, I finally got it finished and plugged it into the PC power supply and got the software working.

I was using Pronterface/Printrun and turn on the heat for the heatbed and hotend. Heatend to 185 degrees and Hotend to 60 degrees. Everything was fine when it was warming up and I was checking the temperatures. It finally got to about 192 and 40 degrees or so and I noticed a fire on my RAMPS board. I've included some photos of the area that was damaged.

I'm stumped on figuring out what is causing this and how I can fix it so it doesn't catch on fire. I ended up trying it a second time and at about 80 degrees on the hot end. I can tell the board was cooking (I smelt something burning) also saw a few sparks so I turned it off and haven't tried since.

Anyone know what is causing this problem and/or how to fix it?

Thanks in advance!

There is probably a short somewhere. I remember when I used to have my old ramps it almost started a fire on the main 12v connector. Its probably the bed because you said the hot end was at 192 and the bed was only at 40c

Check the resistance of your heatbed connection, it should be around 1 ohm, because you are probably drawing too much current. The part that us burnt is the 11A PTC "fuse". The PTC is supposed to limit current to the heatbed, but a known problem with these is that they overheat and catch fire instead.

You might need to replace the PTC now it has burned, but you also need to identify why too much current is drawn. I think it is most likely a bad heated bed,

Could it be a bad solder on the heatbed? What wires (? AWG) are suppose to be connected to the heatbed? What type of PTC is it? 11A PTC and I can just solder it onto the board?

Thanks for all the help. Been working on my printer for weeks to get my first print out but ran into this issue.

I'll post a picture of my soldering underneath my heatbed. My solder was over the red board and not just on the silver square. Is it suppose to remain only on the silver square and not touch the heatbed itself? The heatbed was pre-assembled with the resistor and I believe it's the standard resistor that comes with the heatbed.

Edited 1 time(s). Last edit at 08/26/2013 05:28PM by 3dcreatorlabs.

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Could it be a bad solder on the heatbed?

Then it would catch fire there, not on the RAMPS board.

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What wires (? AWG) are suppose to be connected to the heatbed?

The thicker, the better. It's said SIHF-J 3x2,5 is pretty good. Silicone insulated, three wires (2 would be sufficient), 2.5mm² each. 2.5mm² translates to AWG13.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

According to the wiki [reprap.org] the part is this one [www.digikey.ca]

You can solder it by hand no problem.

also best to use tinned wire. copper oxidizes, and when it does it generates more heat, untill the resistance from the oxide is high. then the connection will not work without cleaning. If you solder the wire ends that contact they likely will never get warm enough to melt when screwed into ramps connector. if any thing just make sure it is clean connection whatever you do.

Whether you fix it or replace it, definitely don't use mixshop. I had one of their ramps boards explode on me because they are only rated for 12 volts. The capacitors literally blew up when I tried a 24 volt PSU.

@aduy - I checked my solder and my cables and they look ok. I don't see any short anywhere. Could there be a short somewhere else that is causing this issue?

@bobc - There is a 1 ohm resistor soldered to the hotbed. Can I use a higher ohm resistor as a precaution or is that not recommended? If I can what kind of ohm resistor should I get?

Since the 11A PTC fuse are known to overheat and catch fire is there something I can do to prevent this from happening? Can I use a bigger fuse to prevent fires? I would like to be able to print and leave the house while it's printing. Is this not recommended?

Where is the best place you suggest to buy a new PTC? Where can I get a better heated bed as well? Do you have any suggestions?

@Traumflug - Would it be ok if I used a 10 AWG wire to be safe?

@bobc - Thanks for the links to the PTC fuse.

@jamesdanielv - Where would you suggest I get tinned copper wire? Could I get 10 AWG to be safe for both hot end and heat bed? Currently, I'm using copper wires.

@ohioplastics - Thanks for letting me know! It does feel dangerous using this board if it will catch on fire. Any particular reason why there boards are catching on fire? Are they knock offs or low quality boards? Where do you suggest I get a new RAMPS and Arduino Mega 2560 R3 board for great quality?

Question 1
This picture below. Both yellow's are coming from the 12V section. Because, I have both of these on the top and bottom, does this mean I am putting 12V and/or 24V into my RAMPS board. I'm a bit confused on this part.


My Heatbed Photos
Here's a picture of my heatbed soldered from the top view.


My Heatbed Setup from the bottom.


Edited 1 time(s). Last edit at 08/26/2013 09:29PM by 3dcreatorlabs.

Make sure the heatbed is measuring at >1 ohm. The solder mask should protect it, but the small gap around the pad and the untrimmed ends is suspect. If you do resolder it, solder it with the wire stuck straight through and trim it with diagonal cutters. That will at least let you see all the way around the pad and reduce the chance of soldering the solid copper flow.

@3dcreatorlabs:

tinned marine threaded copper strands 12 gauge should do it. 12gauge should handle up to 41amps. resistance is 1.588ohms per 1000feet

[www.ebay.com]

Edited 1 time(s). Last edit at 08/26/2013 10:21PM by jamesdanielv.

The RAMPS board is really two separate circuits

The 5 Amp circuit is for everything other than your heated build platform
The 11 Amp circuit if for just the heated build platform.

Both run at 12volt. (normally)


The Fuse that caught fire in on the 11 Amp side, ie the heated build platform.

I would say you Heated build platform is shorted. You need to check its resistance. Should be about 1.2 ohms

I have seen some cheap HBP from dx.com that are shorted straight from the factory.. (it is fixable, if this is the case)

@Dust - How do I check the resistance on the heated bed? How do I fix a shorted heated bed? Thanks!

As a few mentioned already, check the resistance across the leads going to the heatbed. It should be >1 ohm -- the few I've measured have been around 1.2-1.5 ohm. 0 ohm would indicate a short. On the other hand if you have more than say 3-5 ohm then it could also indicate a problem or bad heat bed.

@Nyarlathotep - To check the resistance from the heatbed. How would I actually do that? Sorry, I'm a newb? Do I use a multimeter and if so where do I actually connect it? Thanks!

Use a decent ohm meter or multimeter set to ohms

Some cheap ones cant read that low.

Just unplug your Heated build platform form the ramps and stick your meter probes on the wires. (while its all off of course!)

The ones from dx.com that where bad had no copper break around the wire solder points on the non element side.
So when you solder on your wires, you had a straight short threw the non element side.

The non element side is your top side picture.

The fix was to simply remove a bit of copper around one connector on the non element side. One person used a craft knife and cut a little triangle around the connector (this took a while) another person used a dremel type tool to remove the copper.

It is very important you do this on the non element side.

Edited 2 time(s). Last edit at 08/28/2013 05:11AM by Dust.