HOW TO SUCCEED WHEN PRINTING IN PLA
Let's dive into the details of 3D printing with PLA filament. We will discuss what PLA is and how to make it work with your printer, how to find the right temperature and what surfaces to print on.
PLA is a wonderful material for 3D printing. It is a renewable, biodegradable resource. It is non-toxic and has a pleasant smell when printing. PLA filament comes in a wide range of colors and because of its thermal characteristics, is particularly easy to get great prints with.
Table of Contents
WHAT IS PLA
PLA or Polylactic acid is a thermoplastic polyester. It is commonly derived from renewable resources, such as corn starch, tapioca roots or sugarcane. One of the most attractive things about PLA is that it naturally degrades when exposed to the environment. For example, an item made of PLA in the ocean has a degradation time on the order of six months to two years. Compare this to conventional plastics, which take from 500 to 1,000 years to degrade. It is important to point out that although PLA will degrade in an exposed natural environment it is very robust when used in any normal application such as a printed toy or a critical piece of a printer. In that respect you can think of it as being similar to iron. If you were to expose it to continuous moisture or leave it outside, it would "rust" and become unusable in short order. But if you had it in your home you would expect it to last nearly indefinitely.
PLA is used in many industries from food packaging (like the pictured water bottles) to biodegradable medical implants such as sutures, tissue screws, and tacks. PLA comes in a number of grades; scientific, medical, food safe, and then to the type of PLA used in consumer 3D printing. PLA's natural melting temperature is around 80C but it is mixed with other plastics to make it suitable for 3D printing.
If you have printed with ABS, you will find PLA to be harder, wear more slowly, and be easier to get a nice flat part with. PLA is less thermally contractive and much easier to print big parts with. The thing to consider is that being stiffer and harder also means that it is more brittle. If the part you're printing will be used where it might receive a lot of banging or sharp collisions, PLA may not be the best material.
The other important consideration when printing parts in PLA is knowing what sorts of temperatures they will be subjected to. PLA becomes soft at 70c - 80c and will deform if used in environments that remain above those temperatures for any prolonged time. This is why you should use ABS or some other material near the extruder. At MatterHackers we generally use PLA for all our printer parts except those that are directly around the extruder (such as the x-carriage, mounting plate and extruder block) which we print in ABS.
GETTING THE FIRST LAYER RIGHT
The first layer is the most important part of any print. There are a few things you need to do to get the first layer to stick well.
You need the print bed (or print surface) to be level.
You need the extruder to be homed to the correct height from the bed.
You need a good base material for your PLA to adhere to.
PRINTING ON BLUE TAPE
Blue Tape, or Painters Tape, is one of the easiest and fastest ways to get a great print from PLA. Here is a quick checklist of things you want to make sure you are doing.
Check that the Blue Tape creates an even layer. Don't miss any spots. Don't overlap the edges.
Don't heat the bed when using Blue Tape, it will not stick well to your PLA
Replace any tape strips that get damage when removing parts.
Replace the tape after 5-10 prints or when parts stop sticking.
If your first layer is not sticking - make sure the print head is close enough to make a nice squished line of PLA. If that doesn't take care of your problem, you may want to increase the 'first layer temperature' 5 to 10 degrees (start with 5 and increase if necessary).
Blue Tape is not perfect but it is very easy to use and generally gives great results. However, sometimes your parts can pull the tape up off the glass during printing, and you will see some warping when that happens. To reduce the Blue Tape from pulling up, we have had great results putting Blue Tape on top of PET tape, but that's just crazy :).
NOTE: PLA will not stick well to Blue Tape when it is warm. You do not want to heat the bed if you plan to print on Blue Tape. Also, the surface of the Blue Tape will lose its ability to hold onto a part with use. You should replace the tape when you start to see the adhesion degrading (usually somewhere between 5-10 prints on the same spot).
PRINTING ON GLASS WITH A HEATED BED
When you have a temperature controlled bed, printing directly on glass can be a great option. The recommended bed temperature for PLA is 70C.
Having your bed level and extruder at the right height is extremely important when printing on glass. If your extruder is too far from the glass your PLA will not stick AT ALL, if it is too low the glass will completely block the extrusion of material and it will not stick AT ALL.
If your first layer is not sticking
1. Make sure the bed is level.
2. Make sure the print head is close enough to make a nice squished first layer.
3. Make sure you run the extruder enough before your print starts so there is filament going onto the bed during the entire first layer. In slic3r you can turn the number of loops up to 4 or 5 or more depending on the part.
4. Clean the glass with denatured alcohol
When you can get it working well, glass is the absolute best way to print PLA. It make a great shiny bottom layer and the heated bed ensures that parts stay nice and flat.
OTHER PRINTING SURFACES
Printing on Kapton Tape
Many people have had success printing on Kapton Tape. To print PLA on Kapton Tape you need to have a heated bed. We used to print on Kapton Tape on a heated bed, but after mastering printing on glass we no longer recommend printing on Kapton tape as a first option. The procedure for printing on Kapton tape is nearly identical to printing on glass but involves more setup and clean up. If you have advice on other benefits of Kapton Tape please let us know. We are always working to improve our process.
Printing on Polycarbonate
We have experimented briefly with Polycarbonate, oiling it slightly with vegetable oil. Polycarbonate did work, and the print came out fine. However the part was difficult to remove and the benefit was not readily apparent. We feel this method deserves more investigation and we'll update this section as we learn more. For now we recommend sticking with Blue Tape.
GETTING THE TEMPERATURE RIGHT
When working with a new roll of filament for the first time, we generally like to start out printing at about 200c and then adjusting the temperature up or down by 5 degree increments until we get the quality of the print, and the strength of the part, to be in good balance with each other.
What to Look for:
If the temperature is too high
You will see more strings between the separate parts of your print and you may notice that the extruder leaks out a lot of plastic while moving between separate areas of the print. If this happens you should try to incrementally lower the temperature by 5 degrees until the extruder is not leaking so much material.
Sometimes you will have a material that is simply less viscous than other PLA and will leak more even at lower temperatures. We recommend you increase the retraction a few millimeters (3-4 seems like a good number for most every PLA we have tried).
If the temperature is too cold
You will either see that the filament is not sticking to the previous layer and you are getting a rough surface (like the picture below), or you will get a part that is not strong and can be pulled apart easily. In either case, you should increase the temperature by 5 degrees and try again until you get good line segments on every layer and have a strong part when done printing.
Extruded Filament Not Hot Enough
When switching PLA colors:
While the extruder is cold set the heat to 80c and wait for it to heat up.
When you reach 80c remove the current filament from the extruder. You may be able to back it out by hand or you may need to reverse the extruder.
If you are having trouble removing the filament, increase the temperature to 100c and try again.
Increase the heat and load the new filament normally.
Run the new color through the extruder until it runs clean and the new color is all that is coming out of the extruder. If you are switching from a dark color (such as black) to a light color (like white or natural) run a while longer to be sure you don't have any dark contamination:
Clean the extruder gear and blow out any particles from the extruder entrance.
Print something that you don't care if it has bits of the previous color in it, or run the extruder for several minutes. It may take as much as 10 to 15 minutes of extrusion before you can have confidence that there won't be dark material mixed with lighter material.
Note: We recommended removing the filament when soft rather than when fully melted so that there is less possibility of depositing melted material onto the extruder drive gear or leaving meterial high up the melt chamber entrance. Both of which can cause jamming and are hard to clean out. Soft removal also helps ensure that you get everything out of the extruder tip.
PRINTING WITH A MAKERBOT REPLICATOR
The Makerbot Replicators extruder is not quite as powerful as some of the RepRap geared extruders so here are some extra tips that can really help get great results.
Make sure your bed is absolutely flawlessly leveled.
Measure the filament with calipers. Take 5 measurments, throw out the bottom and top values and average the remaining 3. Put this number in for the filament diameter.
Clean the extruder. If you been having problems you probably need to do this.
Clean the teeth of the drive gear.
AND THE BIGGIE! Use a tiny drop of canola oil on the end of the filament during the filament change. We got this tip from a customer and it has been AMAZING, not a single filament jam since!
IMAGINE THAT 3D PLA TEMPERATURE QUICK REFERENCE
Color Recommended Temperture Recommended Range
Black 195c 190-210c
Glow-in-the-Dark 190c 185-205c
All Other Colors 210c 205-220c
Note: You may need to experiment with the temperature that will print the best on your printer. Ambient temperature, humidity and the calibration and uniqueness of your printer all play a part in how your prints will turn out.
WHAT TO DO WHEN THINGS GO WRONG
There are a few key things to check when your prints aren't working. But before we look at solutions we need to have a brief description of your symptoms.
"I can't get the first layer to stick."
Make sure the extruder is at the right height. Adjust the limit switch or extruder 0 height
Make sure the print bed is level. Level the bed
"The part has bad internal layers and top surfaces."
Check the extrusion temperature (you may need to increase it by 5 degree bumps)
Check the filament tension.
Clean the filament drive gear
"The outside edges of my parts have lots of little bumps on them."
Make sure your printer is getting enough data. If printing from a computer, ensure that the computer is not too busy to feed the printer commands. If the printer is pausing it is usually due to the printer being too busy.
Print from SD card. On some printers you can try and print from SD card. This often helps the printer have enough data to run more smoothly.
Source better PLA. We have found that the quality of your print material can have a big impact on the quality of your part. Getting better PLA can help you get better parts. However, don't be too quick to assume the problem is in your PLA. With the right settings and patience hobbyists have succeeded in printing all sorts of materials many of which have very low viscosity and inconsistency. You should be able to get at least usable parts even with some lower quality filament.
"Tall sections of my prints look melted or squished together."
Turn on "Cooling". If your printer has a fan you should enable "cooling" in the print settings.
Get a small fan. If your printer does not have an integrated fan you should look into getting a small desk fan. This can help dramatically with tall sections of your print or when "bridging" (printing top layers that span gaps).
"My printer will not put out any material."
Make sure your hot end is getting hot. Check that the hot end is heating at all. If it is not you need to have your printer serviced. It is likely that you have a loose connection or your electronics have been fried (assuming the printer is still connected and responding to your host software :).
Clean the drive gear and adjust tension. The first thing we are going to do is clean the filament touching drive gear and ensure that we have proper tension against the filament. Usually improper tension or a clogged drive gear will make the print look more like the picture we have for low temperature filament, but it sometimes does prevent extrusion all together. Clean the pinch wheel with a wire brush, and make sure your tension is good and solid (too much can also prevent extrusion and is more common with direct drives [the motor is directly connected to the drive gear] but less common with geared drives).
Remove the current filament. It may be that you have a small particle in your extruder tip jamming the plastic. Use the change filament technique described above to pull out any particles that are in the extruder tip.
Check for and remove jams between the extruder and hot end. This is the most extreme type of problem because now it is time to take things apart. Sometimes heat can creep up the filament in the extruder and cause a bulge that then cools and prevents any further extrusion. This is usually at the junction between the extruder and hot end. Take off the extruder and remove all the PLA you can (you may need the hot end hot (80c-100c) to get all the material out. If you can't get out all the filament by pulling it out you may need to try and drive it down through the hot end. We usually use a small allen wrench. If this fails you can try and drill out the extruder or hot end but you may need to replace parts. Be sure to take precautions against being shocked or burned. If you are not qualified to do this work find someone who is, rather than risk injury.