Overheating extruder

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Elmwolf
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Joined: Wed Jun 20, 2012 1:36 pm

Overheating extruder

Post by Elmwolf »

So I got the printer up and running. It was making some beautiful stuff until i noticed it starting to fail to extrude after a point no matter how many times i tried to print things. If it was a very small model it would print but anything that took more then 1/2 an hour to print would end up failing with the extruder failing to push the filament.

I finally noticed a couple ugly little issues.
1. the overall cause of this was one of the wires on the cooling fan pointed at the barrel of the extruder had broken off the fan and so the fan would run until the extruder moved for the first time then it would lose connection and the entire extruder would start heating up.
2. as the extruder heated up the upper block and the barrel of the extruder the filament would fail to advance through the hot end.
3. once the hot end really started getting hot the plastic part that it's attached to started getting soft. This was actually what tipped me off to the problem. I was trying to get the printer to noodle (extrude into the air) when I witnessed the entire extruder shift from the pressure of the filament pushing on it. The plastic had gotten soft enough that the hot end was moving around as if it wasn't even attached.

So morale of the story I am on my way to pick up a new fan with hopefully a little higher airflow and if I the store has it I am going to get one that has LEDs in it to tip me off in case this happens again.

Questions for you Gulliume,
1. Is there a problem with too much air flow? I am considering getting a 40mm x 20mm fan block with an 8cfm airflow rating.
2. If I have problems with it again I am consdering designing a fan duct that would allow me to take a much larger (80mm or 120mm) fan and deliver the air to the top 1/2 of the extruder barrel. Is there any problem forseeable with that?
thanks.
Ed

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gfeliksdal
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Post by gfeliksdal »

Hi Ed,

Sorry to hear this happened. Strange that the wires of the fan pointed at the barrel broke off. How did you guide the cables and how do you think that happened? Would you mind showing a picture? Indeed if this breaks the complete hot-end will reach a high temp, probably higher than 60 degC, which is too hot for the extruder plastic parts because they will get soft. Is the extruder base still intact? Or do you need a new one? If so, let me know and I'll send you one.
Answers to your questions:
1. Too much airflow to some extent is not a problem. I used to put the fan on 12V, this worked but made a lot of noise, that's why it is now connected on 5V.
2. As long as the wires to the fan are not broken and the small fan keeps spinning it should not be necessary, at least not on my 5 production printers which are working day and night.

Kind regards,

Guillaume.

Elmwolf
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Joined: Wed Jun 20, 2012 1:36 pm

Post by Elmwolf »

i think it was the way i had them all coiled together in addition to the way the entire bundle of wires was routed around the handle on the top. In the end it was most likely an operator error. wether or not the plastic part is stable remains to be seen. in the process of extricating the hot end from the printer it had filament that was stuck between the drive wheel and the bearing, i somehow manged to destroy one wire of the thermistor. is there anything special about the thermistor i need to know about when i go to get another one? is there any better way to affix the thermistor into the hot end? i had to reset the thermistor a couple of times prior due to smacking the wire with my hand or pliers when removing the nozzel. my error checking and troubleshooting has had the extruder nozzel out several times in an attempt to figure this all out.

sorry to be a pest. i will try to take some pics before i head for the office this morning..

ed

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gfeliksdal
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Post by gfeliksdal »

Looking forward to the pictures.
The following thermistor I'm using EPCOS B57560G104F. I can send one to you if you like for a small refund, you will have it tomorrow or the day after.
I bundle the cable of the thermistor together with the heater cartridge with a cable tie. I do this approx 5 cm from the heater. This should give enough rigidity.

Kind regards,

Guillaume

Elmwolf
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Joined: Wed Jun 20, 2012 1:36 pm

Post by Elmwolf »

I will look it up and compare it to what we have here locally. I want to make sure if I need parts I can find them local in the event that i need something and your not available. Besides we have a couple pretty good electronics shops here in town. Thanks for the offer though. :c)

The rigidity wasn't the problem once everything gets in place it seems to be fine. If I rough up the hot end where the silicone sealant is going to be to glue the thermistor in place would that help it adhere to the metal of the hot end better? Or is it a case that I am just impatient and not giving the sealant enough time to set up before I try to put the machine back in use?

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gfeliksdal
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Post by gfeliksdal »

Ok no problem...

I guess roughening the surface will help. Officially it takes approx 8 hours to properly harden, but if you're careful you can afford to be impatient :)

Elmwolf
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Post by Elmwolf »

Ohhkay (big sarcastic sigh) i will try to be patient when i fix it tonight and wait till tomorrow before i fire it up. Patients or a lack there of is the one thing i freely admit as one of my faults and something i need to work on. Thanks again for the info.

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gfeliksdal
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Post by gfeliksdal »

:), please let me know if you got it working again.

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