Unresolved Black Spots in the prints like burned plastic

Hi,
I am new to 3d printing and this is my first 3d printer. When ever I print something I see some black spots in the prints. It seems that the plastic is burned. They are completely random. It is not a deal breaker as mostly I will be printing robot parts for hobby but still want to know if it is broken or is it normal and if there is a solution.
Thanks guys

 

Every time before the printing actually starts and when the extruder is getting to its required temperature (210C, for PLA), the extruder starts to leak some melted plastic. this happens at around 180C. I keep on removing it with tweezers and after a couple of times it stops.

 

Does it leak filament out the top of the heater block?

 

leaking a small amount out of the tip during heat up is fine. check for other leaks.

 

So yea..I am having that trouble lately.. and I didn't used to. It's an ooze control problem. I get a little blob in crossing perimeters.. part of it rubs off on the perimeter and part sticks to the head.. then it cooks on the head. Eventually gets to a point where it builds up enough to drag off onto the model.
I never used to have this problem. Need to figure out why its happening. Good layers.. but.. blah.

Or it can be a leak from betwixt the heater and the hex.

 

It seems that the black plastic box around the hot end is melting. Pictures attached, you can see the melting. Now can any one tell me how to fix this. I am an absolute beginner in 3d printing.

 

That isnt plastic its silicone. Its not melting.
See all those strings all around... They get on the hot end and cook to black goo. Builds up and sloughs off.
It doesnt look like you have a leak. Its the strings wrapping i would guess. Lower temp... Probably adjust estep and lower extrusion.

I take that back... Looks like you do have a leak. See the blue coming out the heater wire hole? I bet you cant take that silicone boot off. Its plasticed on there. Easy to check. Let it cool. If its stuck. Youre leaking. Looks like some blue showing at the top too. It pools on the heater block ans seeps into the boot. Then onto your print.

 

yes it seems that there is a leak. I took off the small fan and saw a lot of blue plastic sticking on top of the silicon boot. But the strange thing is that the color of the plastic in top of the silicon boot is light blue. I only used that color for a very small time a few prints 2 or 3. Then I started using dark blue color.

Any suggestions on how to fix it.

 

Heat it up and carefully remove the silicone boot. Using a pair of tweezers remove as much excess plastic as you can.

Then heat it up to as hot as you can, 240 is fine, but more doesn't hurt anything.

There should have been a small 4.5mm wrench included with your printer. Use this to grip the flats on the heat break. Then with an adjustable wrench or 7mm grip the nozzle and tighten it down till it's snug.

This will prevent leaking

For reference:
http://i.imgur.com/0kHwHvQ.png
http://i.imgur.com/foXDPd1.png

 

Thanks Mike will try it today or tomorrow and posts the results.

 

Sealed it up with that is all. and cooking it can kill the color too. it might actually be that darker blue.

 

Well I got most of the blue stuff off. Unfortunately now it seems that the filament is stuck in the extruder. I can not get it out even if I try to pull it. Also I tried to set the temperature high, till 240 was fine but i tried 250 and i started seeing smoke from the hot end. something was definitely burning. Well any thoughts on how to get the filament out of the extruder.

 

CLip the filament and take out the hotend?
You have to take it off anyway. Maybe it will become clear whats going on.

Burned finger fun to ensue.

 

sure will try that and let you guys know what happened

 

Just checked a print.... Jammed. Mine was easy tho. Leak between ptfe tube and nozzle. ... Ir some junk fell in there. Sticking to pla till i get my new hotends.

 

I was able to remove the hot end and take the stuck plastic out. Its very difficult to clean the hot end completely and also it seems that the nozzle and the heat break are completely tight. Anyway Robo3d is sending me a replacement. Now another question is how did it became loose. Also At 250C I was seeing a lot of smoke, don't want to try that again.

 

You didn't need to clean the nozzle completely, just enough to gain access to the heat break wrench flats.

If it was completely tight it wouldn't have leaked. At least that's the case 99.9% of the time.

If you didn't grip the heat break with a wrench and tighten it down using another wrench then you can't be sure it was tight.

There's absolutely no reason it would smoke at 250C. That's a little hot for PLA to print at but it will still work up to like 300C.

The only possible reason it could have gotten hot enough for that is if the thermistor was not making contact with the heater block and it got extremely hot

Getting a replacement is a good option though.

 

yea.. the factory thermistor will have great difficulty getting back in its hole (or out of it) after a leak situation. Must mind that. Once the thermistor falls out, the machine will run away till it runs out of power and shuts off.

 

I got the thermistor back in as I was able to read current temperature.
Do I need to try to tight it while its hot. Even if I get a new one there is no harm in learning how to fix it