Ultimater 2 extruding to early

[cor3ys 28]

Hi Guys

My first time with a 3d printer so please be patient with me...

I have setup my umtimaker 2, had a few bad prints but i now have it set up good, apart from one issue where it is extruding filliment to early.

I am using the pre installed files on the sd card..

I select the job and the machine waits while it heats up, once this is done and it all fires into action the exruder starts extruding as soon as the heat bed starts to move up, so once the bed is at its right level and the print head gets in postiion i have already extruded filiment and end upp with a striningy mess before print.. but the actuall print is spot on...

Why is it extruding before heat bed is in place and print head is in posttion ?

 

[illuminarti 18]

It's priming the print head, to make sure that it's ready to start the print. The nozzle can tend to ooze if it's sat hot, leaving the chamber with less plastic in it than it should have - so that when the print starts, nothing comes out at first, as the plastic is just refilling the head, instead of coming out of the nozzle.

So, when the print starts, it pumps a little plastic through first to make sure the head is full. It also helps flush out any 'cooked' plastic that might have sat hot for a while, and degraded a bit.

Just take a pair of tweezers, and pull the excess string off, before the print proper starts.