Hi,

I have a -Prusa i3 hephestos- that covered with a box of 3mm perspex and for the last 5 months i printed with PLA without any problems.
recently i decided to print some parts with ABS.i went to the store where i bought the PLA and bought black ABS 1.75mm

I succeeded to print 3 parts on glass but with speicel pad/sticker of "Bq",but after that i didn't suceed to print at all so i decided to buy a new glass for ABS parts and glass for PLA parts.
I bought a 3mm mirror and start to print on it(i bought a hair spary and it stick very good) but after 30% or sometimes 80% the extruder getting stuck and filament don't get out so i need to stop the print and then clean the extruder with some needle.
All the prints with ABS i did with extruder's fan OFF.

I started to check what is going wrong:
1.I print from the computer with "Repetier",so i checked what if i print from the SD card-> didn't help.
2.I turn off the fan of the head>didn't help and even worse->stucking at 10%
3.Calibrate the plate over and over again-> didn't help.
4.Raise the temp of the exturder from 240 to 255 c->didn't help


Now i am thinking about 3 things:
1.My ABS is not pure ABS ??->I am thinking about this because when i tried to do ABS juice with acetone(for 1 week and a half) the ABS only get shiny and soft and the acetone stay clear.
2.The gasses of the hair spary cause some reacation ??
3. The mirror casue somthing and only clear glass is good?

Do u have any suggestions ? any ideas ?

Thank u

The blocked extruder/Hotend and the sticking problem are unrelated.
For ABS aPEI plate is imo the best way to achieve reliable adhesion to the print plate.
As for the stuck extrusion, your #1 is one option, but a fairly unlikely.
There are many reasons why a hotend can get blocked, what exact hotend do you have?

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Quote
mister pong
...and bought black ABS 1.75mm

How many times have we seen this in the past? Black filament is the industry's dumping ground for re-grinds, floor sweepings, fillers, and anything else that they can throw into the melting pot and turn into filament. If it will not dissolve in acetone and is jamming up your hotend, change filament vendors! It may cost a little bit more, but you have already thrown away the savings in failed print jobs and frustration. If a vendor does not provide a clear chain-of-custody saying that their filament comes from a major manufacturer and is 100% virgin plastic, they don't get my business.....