extruder hits print after some time printing  

Re: extruder hits print after some time printing

What material are you printing with? Are the edges of your print lifting off the bed by any chance?

Re: extruder hits print after some time printing

At which z-height does it occur?

You could just print something that will not warp, to determine definitively if there is something wrong with your z-axis.

In OpenScad you can create a cylinder, then export as .stl file, then use Slic3r to make a .gcode file and then print it.

OpenScad text:
$fn=70;
cylinder(h=50,r1=15,r2=3);

I find it most useful to watch live and close up what happens, it really helps to figure out what goes wrong, but uses much time.

Re: extruder hits print after some time printing

Three possible solutions:

1. Slow down the print - this will allow more cooling time and prevent warping.
2. Slice with Z-Lift - the nozzle will be lifted on all non-printing moves
3. Print with a brim - this will help to prevent the part lifting.

But all this depends on your model and slicer settings.

Peter

Re: extruder hits print after some time printing

I noticed this problem with the Plattform Jack four times in a row always around the same height.
It is likely that some parts are detaching for this model but once i heard the knocking, stopped the print and was not able to see any part being tilted, detached or higher than the others.

Adding a rim did not help but I tried the same print with two solid layers raft beneath it and it finally worked.

Maybe it is really just warping and I need to be extra careful about it. The big dragon that is always depicted on the prusa mk2 printed without any problems. I will print more things and watch closely before I start modifying the z axis of the printer.

I am printing PLA with 210°C extruder and 55-60°C heatbed temp.

Re: extruder hits print after some time printing

Several tests later i am convinced that all my problems are related to warping. If one of the edges lifts a millimeter the consequences can be severe!
A little bit of play on the Z axis is not a real problem.

Thanks for the help!

I am still not sure which kind of prints are most likely to warp but there should be a lot on the internet about this topic.

Re: extruder hits print after some time printing

Three possible solutions:

1. Slow down the print - this will allow more cooling time and prevent warping.
...
...

Why does it reduce warping when you print more slowly?

And how does that relate to bed and air temperature?

Re: extruder hits print after some time printing

All these things depend on the model.

Printing slower, allows more cool-down time for each layer. It is hot-on-hot which can generate warping of prints with PLA and some models.

Just one more thing to try...

Peter