After a while, things wear out on your printer. One item that is often overlooked is the connection on either end of a Bowden tube. If the teeth that hold the tube in place aren’t doing their job correctly, the tube can move back and forth as the extruder extrudes and retracts filament. The result of this is that you can end up with zits and voids in your final print.
To fix this, replace the fittings on either end first. If it still happens, replace the tube too.
There are many reasons why your 3d print might end up with blobs and zits on the surface. I want to talk about one specific cause of this: power recovery.
While this may seem like a strange culprit to be responsible for the physical deformation on the surface of your part, it does happen. Here is why. The power recovery function frequently accesses the gcode files that are being read to create your print. If you are using a slow SD card or a slow processor, it can cause your printhead to dwell for just a moment. During this time it is still extruding. For this reason, I normally keep the power recovery function off.
If you do much 3d printing, you will eventually want to use a different spool of filament before your current one is finished. And, unless you live in a desert region, your filament will pick up moisture, leading to printing problems down the road. By the way, even if you do live in a desert, I would still argue that your filament will pick up moisture.
I’ve seen some people dry out their filament and then store it in vacuum bags, then remove it when they are ready to continue printing. My preference is to just store it as-is, then dehydrate it when I plan to use it again. I use a modified food dehydrator to do this. I just cut out the middle part of the racks so that the dehydrator closes around the spool. Other people use purpose built dehydrators or other homemade versions. Airtight Tupperware seems to be popular for storage and dehydration.
I relearned something important over the Christmas break that I had forgotten. The word “At.” All of your settings only apply at specific temperature, retract settings, etc.
I increased my temperature, but didn’t change anything else. I know better, but I did it anyway. Oh well. Sometimes it takes a few times to learn a lesson. My print started stringing like crazy. The science of what was happening is simple in hindsight. I had all of my retraction set up for a particular printing speed, specific extrusion values, temperatures, retraction settings, etc. When I increased the temperature, it created a situation where my filament became more molten so it was oozing out of the nozzle and stringing everywhere.
I needed to tune my printer to the new settings. Live and (re)learn.
After trying to print a QR code over the weekend, I decided to tune in my retraction settings. Step 1, I printed a retraction tower. I printed a tower with different levels, with retraction distance set at 0mm, 2mm, 4mm, 6mm, 8mm, and 10mm.
2mm of retraction was a clear winner for my machine, so I decided to dial it in more. I printed another tower at 1mm, 1.5mm, 2mm, 2.5mm, 3mm, and 3.5mm. 2mm was again the clear winner for my machine, so next I decided to play with the retraction speed settings. Most source recommend a retraction speed of 35-40mm/s. I printed a retraction tower with speeds of 30mm/s, 35mm/s, 40mm/s, 45mm/s, 50mm/s, 55mm/s. 40 and 45 both looked pretty good so I printed another one that ranged from 39mm/s – 44mm/s.
Judging from the towers that I printed, my optimal settings are 2mm at 42mm/s.
I switched filaments. I’ve been meaning to change my nozzle, so while I was in there I did that too. When I printed a test print to make sure everything was good my first layer had holes in it.
Here is what I had to do to fix it.
Sometimes, you just can’t get the part quality that you want. For whatever reason, your machine just is not capable. Whether it is because your overhangs cause you to have to use a lot of supports which leave ugly marks on the surface, or your machine just doesn’t have the resolution to leave a good finish. There are a few things you can do.
One side of print looks great, the other looks horrible.
A user recently posted this summary on a help forum. Temperature and cooling play a big role in part quality of 3d prints. The user had their PLA hotend temperature set too high. Additionally, they were underextruding and had their retraction settings incorrect.
Many 3d printing problems can be resolved by going to the basics. Calibrate X, Y, Z, and your extruder. Make sure your bed is level. Run a retraction tower and a temperature tower. Make sure your filament is dry.
I see a lot of people wondering why their 3d prints have little zits and voids in them. One of the potential reasons is because their filament has collected moisture. Filament is porous and collects moisture over time. Most filament manufacturers do a pretty good job of ensuring that filament is dry when it gets to you, but not always. Usually, moisture is absorbed when filament sits around in the house for a while.
When water is heated to 200 °C, like when you are printing with PLA, it turns to steam and then escapes, leaving little pockets on the surface of the project.
To ensure that you don’t have to worry about this, make sure that your filament is dry. You can do this by vacuum packing your filament if you aren’t going to use it for a while, using a filament dryer or food dehydrator to dry out filament before use, and keeping desiccant near the filament to absorb the moisture from your filament.
