best way to purge/clean out hotend?

hi guys

just started trying out clear and glow in dark PLA but having trouble fully clearing out my j-head hotend.

when 1st put in clear stuff i just run the extruder untill red turned to clear.

not i find when i print randomly i will get 1 layer of red as if it comes from now were lol

any ideas on how i can fully clear it out?

I heat my j-head to 80C, then let it soak for a minute or two. Then I turn off the motors in Pronterface and by hand gently rotate the big gear to pull it out. Everything up to the nozzle in the chamber will come out in a solid chunk. After priming the new filament, you shouldn't see the old color at all.

I worked in commercial molding, and the extruders that normally extruded PVC, HDPE, or PP were purged with LDPE then left to cool. When they're heated the next day, the LDPE plugs are easily purged themselves, by fresh PVC or whatever.

pokey9000 Wrote:
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> I heat my j-head to 80C, then let it soak for a
> minute or two. Then I turn off the motors in
> Pronterface and by hand gently rotate the big gear
> to pull it out. Everything up to the nozzle in
> the chamber will come out in a solid chunk. After
> priming the new filament, you shouldn't see the
> old color at all.

This method works very well, although I just push the new colour through until it comes through

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Experimenting in 3D in New Zealand

just wanted to bring this backup

having the same problem agian weekend just gone.

have been printing in red PLA for around 2 weeks.

then put in some clear with blue tint PLA i did the 80C thing ect to remove.

put in the clear blue and run extruder and red comes out so i keep exctruding untill i get clear.

give it another 15mm just to make sure

start print and seems okay then 20% up random 1 layer of red ! then back to clear blue again.

then 80% again 1 random layer of red !

also noticed at times while my hotend is oozing it will all off a sudden ozz out liquid pla like water ?

any ideas whats going on? i had this now with my old .5 jhead IVB and also my new .35 IVB j-head

think i may have found why i was having a problem.

bit of red plastic stuck in the hobbed bolt

i have given the hobbed bolt a clean out and no red lines yet so fingers crossed that was the problem