Hot end failures

Hi,

I have problems with my hot end. Filament melts before reaching the nozzle and the hot end become clogged at around the middle. I ordered a new one and waiting for it.
I want to ask a general question about hot ends.

What are the causes of hot end failures? and What solutions can be employed?
Alternative question: What are the ideal properties of an ideal hot end?

Please share your experiences. (may write down or give links)

What hotend are you using?

Are you actively cooling the top part of the hotend with a fan?

If using an all metal or some other types they require a fan to cool the upper portion of the hotend. Some companies use heatsyncs to address this issue.

What temperature are you running at?

ShadowRam Wrote:
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> What hotend are you using?
>
> Are you actively cooling the top part of the
> hotend with a fan?


I attached the picture of my hotend. Picture is taken from nextday reprap. But I didn't buy it from them.

MultipleMonomials Wrote:
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> What temperature are you running at?


I run at 195 degree Celcius for pla. I tried some higher temperature up to 225. However the problem is pla melts before the nozzle and hot end become clogged at around the middles.

Are you cooling the thermal break with a fan? That is usually required with PLA.

NewPerfection Wrote:
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> Are you cooling the thermal break with a fan?
> That is usually required with PLA.


No. I don't use a fan. In fact, I don't think it will work. Because in this model, a brass tube is threaded inside PEEK. So fan can not cool down inner parts. PEEK provides insulation.

You can still cool the PEEK.

The J-Head is PEEK, and requires cooling.

You mind as well try it, what do you have to lose?

Small PC fan and some zip ties.

Plato Wrote:
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> PEEK provides insulation.

The PEEK needs to be kept cool for PLA, otherwise the PLA bulges before getting into the brass heated area and jams.

I'm using a Prusa i3 with the Magma hot end (all metal). Despite setting up the fan to be always on, it doesn't seem to cool the top (cold) part enough for PLA. I get jams about 30 minutes into a print run when using PLA.

I'm going to try adding a heat sink in addition to the fan.

I have found some interesting things taking thermocouple and infrared thermometer readings in various places. I've only gotten started but had some interesting findings on the heated bed (effective temperature on the glass was 30C less than reported by the thermocouple, wide variance between center and edges of heated bed).

I'd like to take some readings on the Magma upper parts over a print run and see where it's overheating...