Polylactic acid has been around longer than 3D printing itself but it’s never been as popular as it is today. PLA, as it is known by the majority of people, is a thermoplastic polyester which is most commonly made of renewable resources. PLA was discovered in the 1920s by the same guy that invented nylon, Wallace Carothers. Although back then PLA was a costly material nowadays it has become the most affordable 3D printing filament.
When & Why It’s Used
This eco-friendly printing filament is used to make items that won’t be exposed to hot temperatures and moisture. PLA filament is a strong plastic that can be used by both experienced printers and beginners since it’s easy to print with. This material also wears out more slowly and it is less thermally contractive than ABS. 3D PLA filament is great for post print finishing such as cutting, drilling and sanding. All these advantages make it suitable for use in industries such as food packaging and the automotive industry as well household appliances and biodegradable medical implants.
Printing With PLA
Getting The Temperature Right
PLA filament is usually printed at temperatures between 185°C and 205°C. If you are using a 1.75 mm filament you’ll use it at a temperature closest to the lower end of the spectrum whilst thicker (2.85 mm and 3.00 mm) filaments will need a higher temperature. While printing temperatures vary from one filament thickness to another you should start at 180°C and set the temperature depending on the quality of the base layer. Make sure when you change the printing temperature, you do so in 5°C increments until the issue is resolved. This is a process of trial and error and once you find the ideal temperature you’re good to go.
Printing your first layer of PLA plastic filament can be done on glass with a heated bed or blue tape. We’ll go over with the latter first as it’s both easier and faster. When blue (painters) tape make sure that the tape provides an even layer without overlapping the edges of the bed. Do not heat the bed as it will prevent the filament from sticking to the tape. Always replace the tape after 5 to 10 prints or whenever you notice the filament stops sticking to it. If your first layer of PLA doesn’t stick to the surface make sure the print head is close enough to it. If that doesn’t help the filament stick to the tape, then start changing the temperature in 5°C increments. Although painters tape is a great way for beginners to start printing with PLA it can make the parts warp which is not the case with a heated bed.
When printing 3D PLA filament on a heated bed with glass, it is recommended that the temperature of the bed is at 70°C. It’s also important to have the extruder at the right height and the bed levelled, otherwise the filament won’t stick. To prevent the filament cooling off too quickly you can set the temperature of the first layer 5°C or 10 °C higher. After every printout make sure you clean the glass with denatured alcohol.
Changing & Storing Filament
When you want to change to a different coloured filament you must set the printing temperature at 80°C with the extruder cooled down. Once the temperature reaches 80°C remove the filament either by backing it out using your hand or reversing the extruder. If that is not possible at 80°C, increase the temperature to 100°C and give it a go. Then, increase the heat and load the new filament and run it through the extruder until you see the new coloured filter coming out of it. If you are going from a dark to a light coloured PLA plastic filament you’ll need to run the extruder longer in order to prevent dark contamination.
Make sure to clean the extruder gear and remove left over particles from the opening. To prevent your item from getting spots of the previous colour in it, print something that’s not that important to you beforehand or just run the extruder for several minutes. PLA naturally absorbs water over time which is why you should keep it away in a dry place. The best storage place is inside a metallic sealable bag together with some desiccants.
If your printer isn’t able to put out material check if the hot end is getting hotter. If that’s not the case you may need to get your printer serviced by a professional. But in case the hot end is heating up then clean the drive gear and adjust tension against the filament. A small particle may be blocking the extruder from putting out materials so it’s recommended to check for some in the extruder and remove it. When tall portions of your printout are squished or melted you may need to turn on the cooling on your printer. If your printer doesn’t have a cooling system then acquire a small fan to help you bridge the top layers of your printout.
When the outside edges of your part have small bumps you need to check if the printer has enough space to send out commands. Try printing from an SD card to give your prints more data to work with as otherwise the printout will start pausing and generate the bumps again. This can also be an issue with the filament itself, if it is on the cheap side, but it shouldn’t be the first thing you check.