How to Avoid Blobs in 3D Printing?

3D printing, like any manufacturing process, has its advantages and disadvantages, and comes with its own set of constraints. Indeed, it’s not uncommon to encounter problems and obstacles when creating parts and structures of varying complexity. Examples include over-extrusion, warping and elephant’s foot. This time, we’d like to talk to you about the phenomenon of blobs and zits (generally smaller), which can appear on parts made using 3D printing. These are small spots or droplets of filament that can be seen on the surface of parts produced with FDM/FFF. They usually appear where the extruder has started to remove material and return after printing. Over time, this becomes visible as a defect on the surface of the part.

There are many reasons why blobs and zits appear during FDM 3D printing, for example shrinkage. During retraction, a small amount of filament is drawn back into the nozzle to avoid any subsequent problems with the filament. However, if too little or too much filament is shrunk, or if shrinking is too slow or too frequent, these defects can occur.

Blobs and zits appear as small droplets of filament on the surface of 3D-printed parts (photo credits: Chris Cecil).

The temperature and speed of the nozzle can also contribute to the formation of blobs. Too high a temperature increases the viscosity of the material and can cause large quantities of filament to exit the nozzle uncontrollably. A print speed that is too high or changes frequently can also lead to a reduction in surface quality. Finally, insufficient cooling of the various layers of material can also be at the root of these imperfections, as the material can slip and cause irregularities. Now that we know the causes, let’s look at possible solutions to this problem.