No Heat

I haven't been home much lately and was finally excited to have a night where I could be around to print out a kewl little project. I heated up filament and unloaded it and put the new color in. I turned off the machine then inserted my sd card with the print project.

I turned machine on and it would not heat up. What the?!? It was just working seconds before. It looks like the thermistor and resistor are still connected ...any ideas?

Average........ I know your pain.

On mine I cooked the heating resistor, due to running it at 19V and an air pocket in some thermal paste.

Here is what I would do (sublime may have better idea's however):

1. Get a magic smoke meter (aka multimeter) with the machine off measure the resistance of the heater resistor on its legs (see attached). If it is open then it is dead. Should be around 5.6 or 6.8 ohms depending on what resistor you have. If sublime supplied your kit he will be able to tell you what it should be.

2. If resistance is good, then with machine on, attempt to heat the head up and carefully measure the voltage drop across the resistor. Voltage should be approximately your supply voltage. If not then most likely you have a loose connection/controller/supply issue. Check the connections between the controller and the heating resistor, most likely this.

2. No access to magic smoke meter. Does LED 4 come on in the lower right hand corner of the ramps board when you try to heat up the hot end? This will tell you at least the controller is trying to heat the head up. Probably now you need to find a mate with a multimeter and bride them to help you out. Beers work well. I once walked into a factory off the street with a dozen beers and drove out with a forklift, no questions asked........

Hi WWP,

The red LED 4 on the board lights up when I try to heat the hotend. Unfortunately, according to the LED display panel the hot end is not heating up past room temperature so the fan won't turn on.

Unfortunately I do not have access to a multimeter ...or even the first clue about how to use one if I had one.

Maybe I will buy a multimeter and see if I can figure it out.

Edited 1 time(s). Last edit at 10/27/2012 05:17AM by Lisa M.

Multimeters are really easy to use don't be put off by there scary industrial yellow color. It's like a clip board for electrical engineers, no one will question you if you have a multimeter.......
Heaps of simple tutorials on line as well, google as always is your friend: [www.sparkfun.com]

Just be careful with the probes they tend to slip then short things out then the magic smoke gets out. Stick to under 24V systems as well to avoid electric shock if you are new to the magic smoke game.

Anyhow some other pointers:

1. Check the connections of the heating resistor and thermistor. Sometimes you can wiggle connections and things will work again. Then you know you have an issue, and connections need replacing/fixing.

2. Does the LCD read room temp? If you can somehow gently heat the brass hot end with out damaging plastic bits and the LCD read out goes up then you know that the thermistor is OK and it will be something to do with the heating resistor or circuit. Best way is probably put your machine in a warm room for a while, check temp. Then in a cold room/place for a while, check temp etc. Don't be tempted to use a lighter as these leave soot everywhere.

Thanks again WWP.

I like the industrial yellow color. I had tonka trucks as a kid and a few tools be DeWalt. Yellow plastic makes me feel manly.

I will see if I can get my hands on a multimeter and check out some online tutorials.

Since it reads room temp the thermistor is still good. If the thermistor is dead or removed/disconnected you will get a really high reading like 357c.

If the red light on the board comes on then the board and software are working.

This leaves the heating resistor or wires as the possible problem. To test you will need a multimeter or a test light should also work. For the multimeter you would do as WWFP said and with the test light you would connect its ground to the ground terminal on the power input of the RAMPS board and touch the positive of the test light to the one then the other of the heaters terminals (D10 +/-) while trying to heat the hotend. The light should be bright on the + terminal and not as bright on the - terminal since the current would be going through the resistor.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Okay, I managed to find a multi-meter but even after look at the tutorial I have no idea how I would apply it in this case or what exactly it is that I'm testing.

I think I'm going to just swap out the resistor and keep my fingers crossed that my issue will be solved.

Pretty sure it didn't look like this when I installed it.



...blurry cuz I took photo with iPhone. Is it normal for it to turn white in the middle?

I am concerned about this issue because I've actually gotten very little use out of the machine (I haven't even completed 10 prints on this thing). It seems to me that's a little soon for a resistor to be dying. Maybe I just got a bad one?

Edited 1 time(s). Last edit at 11/27/2012 06:33PM by Lisa M.

Although about 80% of RepRaps use Resistors as heaters they were never really designed for it. So when they make a resistor they do not care about the outside shape of it. This causes us a problem when we use them as heaters because we need the outer surface to make contact with the heater block and if it does not the resistor ends up burning out as yours did. This is not that common of a problem and it only happens maybe once in every 200. This is why you need to wrap the center of the resistor in tin foil when it is peanut shaped or loose fitting.

The other option is to use a heater cartridge but they are not as easily available and cost a lot more.

Out of 7 machines I have I have only replaced one resistor. I have even re-used old ones when I was making my own hotends, I would remove it from one and install it in another.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Back in business. Swapped out the resistor. The replacement resistor was definitely peanut shaped so I wrapped it in foil. Hopefully it'll do the trick. I have to admit when I first built this think I didn't understand that the purpose of the resistor was to generate heat (I'd always understood that they resisted current ...not that I have any electronics background other than the little I learned in science 10). I didn't really think about the fact that a byproduct of slowing down current would be heat ...which is really kewl.

When I installed the original resistor I didn't think it was peanut shaped or loose ...but not knowing what it is supposed to look like, I guess I was wrong.

Anyway, keeping my fingers crossed. I've just started a really big print where I've spliced filament together. The splice points are definitely rough. Hope the splices make it through the extruder ...this time if I break it I can't really blame the parts.

Glad to hear it is back up and running. Next will be to switch to Kisslicer which makes printing much easier (more on that soon).

The splice will make it through the extruder unless there happens to be a bunch of retracts right when the filament is in the extruder. The next problem is if you are using the smaller bowden tube supplied with your kit is will the splice fit through it. The last place where it could be a problem is right where the filament enters the hotend.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

LOL... well my splice didn't even make it into the bowden tube ...thought it was smoother than it was. I'm contemplating what would happen if I bought some 3mm diameter metal tubing and put both ends of filament inside and heated up said tubing. would that create a nice smooth splice.. or would the metal just get stuck to the splice point. Hmm....

Restarted with a smaller print as bed time approaches and I don't want to be up all night listening to Tantillus' monologue. The little guy has lots to say.

With my lack of knowledge on electronics it really is amazing that I've made it this far. It speaks volumes for how helpful and patient Sublime and other folks are here. Still learning lots.

Thanks again.