How to prevent printing lines?  

Why are they appearing and how can I prevent them from occurring?

It's hard to tell from a photograph but I suspect your wall thickness needs tweaking. 

Please save your project as a .3mf file

Files > Save Project as

Zip the .3mf and post it here. It will contain both your part and your settings for us to diagnose.

Secondly, is there a way to avoid stringing? It occurs on every print I do (PLA).

Dry your filament.

Cheerio,

RE: How to prevent printing lines?

Thank you for your willingness to help. I have attached my zipped .3mf file: Christmas Tree.

I tried another print at 190 C and the print seemed to turn out better. Could it just be a temperature thing? I am looking into getting a filament dryer as a measure to reduce/prevent stringing.

First a general comment:  White and pastel filaments are always trickier to print because they contain so much pigment that their flow can become non-Newtonian.  Functional prints that require accuracy are often better printed in neutral, dark, or better, translucent colours.

This part has some interesting optimisations, is it a download file from two or three years ago?  It appears to be intended for a Classic perimeter generator; you have Arachne selected (often better but not this time) and, probably, a regular nozzle - you have HF selected.

I don't have a Core One to test it on but I would expect it to print OK with dry, dark filament and the Classic perimeter generator.

Print Settings > Layers and perimeters > Advanced > Perimeter generator

If problems persist it may print better if you slow the print by 15-20%

Be aware that as the 'cutting edge' is only a single perimeter thick it will be fragile and may not last long.

Cheerio,