Blob on corners - Retraction setting?

[martin1454]

Hi there!

- So I just built my first homemade machine - It runs a duet wifi, bondtech BMG and an E3D chimera setup.

Im trying to calibrate it currently, but got an issue.

When i try to print an cube, the corners gets small blobs.

The blobs orcurs when the nozzle jumps from inner wall to outer perimeter.

The problem:

The settings:

and the gcode where you can see the retraction problem[
attachment=2]s3d1.png[/attachment]

[KeyboardWarrior]

I would try lowering the temperature 10 degrees, and maybe increasing your retraction distance by 1 mm. If the plastic is too hot, it's going too ooze right out, and not be easily controllable when the printer does a retraction of filament.

[xXsaberstrikeXx]

It looks like you are having more than a retractions issue. Looking at your first picture (of you holding the green cube) your first layer is not right. There shouldn't be any gaps.

You should calibrate your extruder's e-steps first to make sure the correct amount of filament is actually coming out of your nozzle.

https://mattshub.com/2017/04/19/extruder-calibration/

If you still get the blobs after adjusting your e-steps, then increase your retraction a bit, and increase your retraction speed.

[wirlybird]

Change the start point to be all at the same location and see if the blobs on the corners move to just one corner.
This has been a nemesis of S3D forever!
You can add a little negative restart to help reduce but be warned that it can have an effect on other parts of the print where you may have small detail and very short extrusions.

I think you'll find that the blob issue won't be too much of a problem on most prints.

[martin1454]

It looks like you are having more than a retractions issue. Looking at your first picture (of you holding the green cube) your first layer is not right. There shouldn't be any gaps.

You should calibrate your extruder's e-steps first to make sure the correct amount of filament is actually coming out of your nozzle.

https://mattshub.com/2017/04/19/extruder-calibration/

If you still get the blobs after adjusting your e-steps, then increase your retraction a bit, and increase your retraction speed.

Yeah, my first layer is not correct there - its a new setup, and im still playing a bit with my IR distance sensor height.

I have measured that my extruder extrude 100mm when I ask for 100mm, but I haven't got around to measure the multiplier, so I need to measure my wall thickness vs extrusion width, - My infill is a bit weak, and there is a little bit of gap between lines in solid infill.

But I tried to switch to another filament, and the retraction is a bit better, so the green one is garbage.

I also tried to print one of those "retraction test" with 2 towers - my retraction with 2mm retraction + 80mm/s have no issues with stringing between the 2 towers - it is only on layer change I get the blobs.

Change the start point to be all at the same location and see if the blobs on the corners move to just one corner.
This has been a nemesis of S3D forever!
You can add a little negative restart to help reduce but be warned that it can have an effect on other parts of the print where you may have small detail and very short extrusions.

I think you'll find that the blob issue won't be too much of a problem on most prints.

Yeah I tried negative restart value, but it starts underextruding quickly on smaller parts.
I also tried to make the start of the layer be on the same corner, and the blobs is all on the same corner now.

[wirlybird]

Change the start point to be all at the same location and see if the blobs on the corners move to just one corner.
This has been a nemesis of S3D forever!
You can add a little negative restart to help reduce but be warned that it can have an effect on other parts of the print where you may have small detail and very short extrusions.

I think you'll find that the blob issue won't be too much of a problem on most prints.


Yeah I tried negative restart value, but it starts underextruding quickly on smaller parts.
I also tried to make the start of the layer be on the same corner, and the blobs is all on the same corner now.

Well, you found out what I suspected and you already have seen the adverse effect of the negative restart on small areas.
It's a give and take with 3d printing and the settings sometimes. One gain in one areas is a negative for another!
With the blobs all moving to one corner when you changed the setting you now know it is the start point that is causing it.

You may be able to reduce the blob a bit with a little coasting and maybe wipe but I battled this for a long time and finally gave up since it didn't really affect most prints.