newbie Q: mini not extruding enough material

The Mini is great. after several days of usage, my mini started to not extruding enough (or barely any) material (PLA). When I remove the filament, it looks like the extrusion mechanism has grinded into the filament. (See attached photo). I am wonder if I need to adjust the tension of idler screws? Or something else?

Also – after scraping the very thin materials left on the bed, the bed seems not completely clean – what should I use to clean the bed?

Thanks for helping out a newbie!
P.K.

That looks like an issue with excessive retractions in a short area. I’ve had that happen before and needed to adjust my slicer settings. Is the problem happening with anything you attempt to print, or just a recent one you’ve tried to get to working?

Interesting. It did started happening with one particular file. Of course, I loaded a small test file and that printed, then I switched over to the original one and it failed again. Maybe it IS this particular file. I am using blockscad which outputs to openscad. It has text subtraced out of a block (trying to make a name tag).

How can I check the file?

Thanks,
P.K.

Have a link to the file your trying to print?

This is the binary STL: https://dl.dropboxusercontent.com/u/627774/gab_name_tag_1.stl

and this is the generate openscad program:

//!OpenSCAD


module main() {
  difference(){
    cube([60, 16, 6], center=false);
    translate([4, 4, (depth - font_depth)]){
      // size is multiplied by 0.75 because openScad fonts size is in points, not pixels
      linear_extrude( height=font_depth, twist=0, center=false){
        text("Gabriel Shiu", font = "Roboto", size = 10*0.75);
      }

    }
  }
}
module ring() {
  difference(){
    cylinder(r1=8, r2=8, h=depth, center=false);
    cylinder(r1=4, r2=4, h=depth, center=false);
  }
}


depth = 6;
font_depth = 4;
union(){
  translate([0, -16, 0]){
    main();
  }
  ring();
}

I also made a slightly thicker version with the bottom “plate” 4 mm instead of 2mm, and the model seems to be printing ok now. I still do not understand what is the actual issue though. surely I can print a 2mm thick “plate” on its own?

Okay, yeah, so it doesn’t seem like that file has a ton of retractions or anything weird on the first few layers to cause that problem. At least, that I can tell.

Looking closely at your picture again, it looks like you’re printing a skirt. It looks awfully strange though - very wide and obviously not a nice continuous stream of material. I wonder if that’s because the hotend is too close to the bed for layer 1? What are your layer height settings, initial and overall? And your line width(s)?

I am using the standard PLA(esun) profile. Cura always print a skirt, and you are right, for almost all the prints the initial line(s) are always not very good (not enough materials). I think I need to print more things to get to a better understanding before adjusting the print settings. Thanks for your help @luckyj !

Your hot end is way too close. If you’re using standard quickprint settings, then your skirt should be 0.425mm thick (I only use HIPS and ABS so if it’s different for PLA, someone please correct me). Go up to “Machine” in the toolbar and select “Machine Settings”. Look for the row that says “Z offset” and put in 0.2.

Print a new part with a skirt. When finished, remove the skirt, and using a pair of calipers, measure the thickness. If the thickness of the printed skirt measures, say, 0.22mm, and you know the initial layer thickness should be 0.425mm, then the difference is 0.425- 0.22mm - = 0.205mm.

Now go back to the Z offset and add 0.205 to your previous offset of 0.2, so Z offset should now be 0.405. Print a new part, measure the skirt…if it’s not really really close to 0.425, repeat the previous steps until you hone in on it. Then you should be able to leave that setting alone for the most part for the foreseeable future, unless you have problems with parts sticking to the bed etc. But that’s another issue you don’t need to worry about quite yet.

-Jim

What I do to avoid that issue is delete the lines in the startup code that tell the printer to retract and push back in the filament before the print starts. It’s especially important to do that for 1.75mm filament.

Thanks Michael. I saw that discussed in a different thread here also. I think I have two separate problems but this definitely will help the initial skirt+sometimes first few lines not getting enough materials. Thanks!