How to tell when to change your nozzle

I have been puzzled about when to change my nozzle. I think the answer is that both the nozzle and the throat need to be changed, but when?

I have been religious about doing a "load filament" after every print and pulling the filament out during the "load filament", breaking off a few inches and then reloading the filament. When the nozzle and throat are working well I get an extrusion of more than .0.7mm. Last night I was lazy and did not replace the hot end when I got an extrusion diameter of 0.6mm. My print failed about 2 hours in. This morning I replace the hotend, got a nice 0.8mm diameter flow and my print had no problems.

So now I know when to replace the hotend, but are the components bad?

I am positing that once some plastic plates the walls of the throat or nozzle I can not get enough flow. I have ordered some ethyl acetate from Amazon. My plan is to disassemble the bad hotends then heat the nozzles and throats and clean them. I will then dump them in a glass container with the ethyl acetate ( the only thing I can find that will dissolve PLA ). After a week I plan to reassemble the hotends and see if the problem is solved. I use hardened steel nozzles and the throats are hardened stainless.so I can not believe that they have worn out.

I will get back with the results.

 

Using the nylon cold pull method to clean a nozzle of previous material and debris might be an easier method than disassembly and chemical attack. My Sigma R16 printer has the temperature sequence built into the operation menu, which eliminates the need for me to remember temperatures.

Effectively, one removes the old filament. Increase the temperature to that appropriate for nylon. The hot end must be an all metal hot end or the temperature must not exceed the point at which a PTFE liner is damaged by the heat. Once the nylon temperature is reached, the filament is forced through the nozzle. Even hydrated nylon (useless for printing) can be used as the bubbles in the filament cause no problems.

Once sufficient filament is pushed through to provide clear results (use natural, non-pigmented nylon), the temperature is reduced until the nylon will not move further through the nozzle. According to the MatterHackers web site, that is room temperature, consistent with the process for my printer.

Increase the nozzle temperature to 115 °C and monitor the progress of the increase. When the temperature reaches 90 °C, pull firmly to remove the nylon filament. It will collect the debris and remove it from the nozzle.

Repeat this until the filament is pulled and contains no debris.

I have had a nozzle clog so severely that I could not push nylon through it, but when I continued the process, the blocking matter was removed and repeated the process until it was clean. That one took seven cycles!

 

I would like to know if the diameter of the extruded filament during "filament load" was just as large in diameter as a new hotend. I have cleared clogs, but if the extruded diameter during filament load is not large enough I will get a low quality print or a print fail.