How to prevent jams when shuting down or starting up printer

I have my Prusa/Mendel working now and starting to produce decent prints, BUT, I spend far too much time clearing filament jams in my extruder and hotend. Once cleaned out and restarted the print is usually OK, but at the end of the day or between prints it is necessary to shut down and on restart I will have a jam more often than not.

My current method is to have my fan cooling the area above the heat module, and turn off the heat. My startup is
to turn on heat and wait for it to reach temperature, then manuall command it to extrude. This is my go/nogo point
and often there is no filament flow and there is a jam or blockage somewhere. I then dig out the tools to begin another stripdown - I am getting good at this part...

What is the best way shut down and startup our printers to prevent filament jams?

There must be some best practices out there, I can't believe people have as many jams as I so as I do. I spend more time getting filament to flow than I do in printing!

I am using a Wades extruder and when confident in my prints I will print a Gregs Wades hinged extruder.

I am printing with 1.75mm PLA, have a fan to cool the PTFE tube, use a Wades extruder and a basic hotend.

Any suggestions will be appreciated.

Bob

What Hotend are you using?

I run a fan on the thermal break all the time, and just let it cool down before killing the power. Recently I've been using Repetiers extruder fan control that runs the fan both when heating the extruder and anytime the thermistor reads over 50C, but prior to that I just connected the fan directly to 12V.
Before I started experimenting with a new Hotend I hadn't had a jam in months.

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My blog [3dprinterhell.blogspot.com]

I was plauged with jam after jam when using a MG hotend but after switching to a J-head the non user cuased jams are all but gone. Almost all jams i have now are caused by running the first layer to low to the bed. I can leave my hotend on at printing temp almost indefinately without a fan blowing and still prime and print without any problems.

Heres a few things to check. 1. The teeth on your hobbed bolt are cut to shallow which quickly clogs the teeth with filament and causes jams. 2. Your first layer height is to low. 3. You are printing at to low of temperature or are printing to fast for the filament to melt fast enough in the hotend. 4. Your filament retract speed is set to high which will sometimes strip the filament on the hobbed bolt. 5. Your pressure on the extruder idler bearing isnt tight enough to squish the filament into the hobbed bolt teeth properly.

Hi Polygonhell,

It is a pretty basic hot end, no name, came with kit. Consists of heater block, nozzle, threaded brass brass tube with hole for 1.75mm PLA, 15mm diam PTFE barrel with hole for PLA and the threaded brass rod. It is held in the extruder body by 4 screws applying a "pressure grip".

I have since modified this to take 2 bolts drilled through the PTFE instead of the pressure grip.

Bob