I dated a girl to count stars over the lake last night.She is so beautiful and a perfectionist to her fingertips.A few months ago,I followed her instagram account and found that she loves Pokemon toys very much.So I decided to make a Charizard with a 3D printer and gave her as a gift.She looked at this cute stuff carefully but soon she gave it back to me.I couldn’t think of any reason why she should do that .Did she want to break off our friendship or she like something else?NO way!The design of her mobile phone case is a Pokemon!Oh,Wait!What is this?It is a pesky blob right on the surface of my 3D printed toy.Damn the blob!I left a bad impression on her.

You must be disappointed when seeing blobs marring our 3D prints.,which is commonly called“zits” ,can occur due to the frequent start and stop of extruder as it moves around.These blobs on your model represent the position where the extruder began to print a part of the outer shell and then returned to the same position after printing the perimeter.Without leaving a mark, it’s hard to connect two pieces of plastic , but here we figure out two tips to keep the blobs from occuring on the surface of your print.

Tip 1:add a negative extra restart distance

Finding out where they are occurring is vital to reduce blobs.You should make sure if blobs happen at the beginning of the perimeter,or as the perimeter finishes printing.If it is the former, the extruder is most likely priming too much plastic.To solve this problem,you can attempt to adjust your retraction settings,add a negative extra restart distance. For example, if your retraction distance is 2.0mm, the extra restart distance decreases by 0.4mm, and each time the extruder stops, the filament will be retracted 2.0mm .But when it starts again, 1.6mm of the filament will be pushed back into the nozzle.You ought to keep tweaking this number until there are no blobs.

Tip 2:turn the “coasting” setting off 

If you find that the blob is happening as the extruder finishes printing a perimeter,it is posssible that the built-up pressure inside the extruder nozzle pushes out more plastic than expected. In this instance, the best solution is to turn off a setting called “coasting” just before the end of the perimeter ,which can relief some of the built-up pressure within the extruder.Try turning this feature on and increasing the value until the blobs stop appearing.

So that’s the solution to the blobs. Now I am printing a larger Pokemon toy.I can’t go wrong this time, for the sake of my beloved girl.

Source:　https://www.simplify3d.com/preventing-blobs-on-3d-print/