Filament sticks to nozzle

Hi people!

I have just built my 3d printer prusa i3 Steel.

I have got some issues about the sticking filament on the bed. When the printing starts the filament doesn't sticks to the bed but it sticks to the nozzle clogging it.
On the other hand, I've got another problem with the filament. When the hotend is heating up it leaks a little bit of filament before the start of the printing.

What can I do to get the filament adhered on the heating bed?
How can I avoid the leaking filament before the printing?

I use an aluminium heating bed mk3 at 110 ºC, E3D v6 extruder and ABS plastic.

Thank you

Edited 1 time(s). Last edit at 09/10/2017 01:25PM by mateu calafat.

The first layer in 3D printing is the most important, and can take some time to get right, but is well worth the effort in the end. Now to why its not sticking.

First thing to check is that the bed is level with the nozzle, this means that the nozzle is the same distance from the bed in all corners and the centre. Sadly most 3D printers are designed with 4 point levelling that will just warp the bed, 3 is best, anyway Im getting off track. Use a single sheet of paper and place it between the bed and nozzle, at Z=0 you should feel some grip by the nozzle when removing the paper. Adjust the levelling points so the grip is the same at all points. Or if you want go to an Auto store and get some feeler gauges, so much easier.

Next thing to check is first layer height. You don't want it too high or you will get curls or it can stick to the nozzle, too low and the filament wont feed. Some printers have a Z adjust for the Z endstop, but due to "Auto levelling" this has been removed. You can use software to correct, most slicers have a Z offset / adjust

Finally the build surface, this needs to be clean and ready for the filament to stick, oils from your hand can remain on the heatbed, so always clean your bed before you set the print and try not to touch it, isopropyl is what I use. The the question that has been with the community from the start, what is the best surface. Most people use glass but this was more to give a flat surface as the old PCB heatbeds would warp. Others like tap, blue painters tape was standard for a while, then kapton and now PEI. Or you could buy something like BuildTack that some people have good success with. At the end of the day if you have a flat bed, at the fight height as is clean you shouldn't need tape or anything else for it to stick.

As for your other question, the leaking nozzle is normal. Due to the design of the extruder there is no real way around this. Just add a perimeter to the start of your prints or some slicers have a wipe function to remove this and you wont have any issues, or have a set of tweezers on hand at the start of your print.

Thank you scottybfg for the help.

I have configurated Z offset in Slicer with the height of a sheet of paper: 0,1 mm.

Then I have cleaned the heating bed with pharmaceutical alcohol and I have stick a piece of kapton.

And surprise! The first layer has been correctly adhered.

Hi;
ABS is much harder to work with than PLA. You may be better or at first to learn with PLA.