We cannot stress it enough. The first layer of your print is CRITICAL. It serves as the foundation for the rest of your print and getting it right will drastically increase the probability that your print will turn out the way you want. The overall goal for your first layer should be to create a strong bond between the filament and the print bed. There are a tons of parameters you can tweak while printing but we will focus on a few variables have most impact on the success of you first layer:
- Bed Levelness
- Nozzle Height
- First Layer Height
- First Layer Width
- First Layer Speed
- Nozzle and Bed Temperature
- Skirts, Brims, and Rafts
First and foremost, you must make sure that your print bed is level. As you more experienced printer aficionados know, a majority of failures will happen in the first few layers, and the cause is usually a non-level print bed. So how can you tell that your bed is level? The better question is “what are the indicators for a non level print bed?”. Here are a few indicators that you may need to re-level the build platform.
- The initial layer is not sticking to the bed or it is leaving gaps between the filament.
- The initial layer isn’t complete; parts won’t lay down on the print bed
- The nozzle scrapes the build platform at some locations.
- Plastic gathers around the head during printing of the first or second layer.
- When printing the second layer the print head is picking up the first layer.
While these symptoms can also be caused by other problems, leveling your print bed is the simplest and most effective place to start. There are different ways to go about leveling your print bed, but it is a little too long for this article so check out our post on bed leveling to see how it is done.
Setting Nozzle Height
Once your bed is leveled, the next step is make sure that your nozzle is the correct height from the print bed. The nozzle should be close enough to press the first layer onto the bed and create a strong bond while keeping enough distance between the two so the nozzle can extrude the filament. If the nozzle is too far, you will see a thin first layer that struggles to stick to the bed and often leaves gaps between the filament. On the other hand, when the nozzle is too close to the bed you will find extruder will struggle to push out the necessary filament and may clog up your nozzle. In the image below you can see the first layer with the nozzle at the correct height, too far away, and too close.
Finding the optimal distance is accomplished with a little fine tuning of the z-stop bolt on your printer. The z-stop bolt is the part that hits the z axis microswitch when the printer moves to the nozzle to the home location. Using an allen wrench, adjust the height using ¼ turns until you dial in the perfect height. The first layer should look something like this:
For those who have a set of calipers and and want more precision, can use the scratch paper method. Without any filament in your extruder, heat up your nozzle and print bed to the temperature that you will use while printing (this accounts for the thermal expansion of the nozzle). But be careful not to burn yourself, the nozzle and build platform will be extremely hot.
Then, using a piece of scratch paper, place it under the nozzle Set your Z axis position to the home location (0 mm) and try to pull the paper out from underneath it. The nozzle should barely resist the movement of the paper underneath it. Adjust the z stop until you reach this point of slight resistance. After you have done this, take some calipers and measure the thickness of the scratch paper. Remember this number, you will use it later. Then go into your slicer settings and find the z offset field. If you use slic3r, it will look like this:
Input the thickness of the paper into the z offset field. What is the Z offset you say? It is the parameter that tells your printer how from from the print bed it is starting at. The default offset for the printer is 0mm which means your printer expects the nozzle to be right on the print bed. When you enter a value in this field your printer takes this value into account when it moves to build the first layer. So lets say I want my first layer height to be .3mm, If I set the z offset to .1mm my extruder will only rise up .2mm to start the first layer.
Now that you have your bed leveled and your nozzle height dialed in, you can begin to focus on the finer points of building that perfect foundation. All of adjustments you will find below will be done in the slicing programs.
It is beneficial to have a thick first layer, even if you plan on printing a high resolution part on the around 0.1mm per layer for the rest of the print. A thicker layer provides more material flowing onto the bed which helps with bonding and gives you a little wiggle room if your print bed isn’t completely level. Most slicing programs allow you to specify a first layer thickness and then also set the layer thickness for the rest of the print. A rule of thumb is that the layer height should always be below 80% of the nozzle diameter. So if you have a 0.5mm nozzle, and you plan on printing a 0.2mm/layer part, a good starting place would in the neighborhood of 0.3 to 0.35 mm initial layer height, but not above 0.4mm. When determining the first layer height, you should also take into account the width of your first layer.
In our experience, we have found it very beneficial to have an extrusion width that is wider than the nozzle on the first layer. The thought is that this in addition to encouraging strong print flow, it creates a wider filament profile that will have more surface area to bond to the bed.
A 2:1 width to height profile is generally sufficient to create that strong bond with the build platform. Slicing programs generally allow you to designate the width as a percentage of the layer height. So if have a 0.5mm nozzle and plan on using a 2:1 extrusion profile, your first layer height should be at least 0.25mm.
Slowing down the printing speed on the first layer provides forgiveness if any other parameters aren’t fully dialed in. Slowing down the extrusion rate reduces the forces pulling on filament as it is extruded and bonded to the build plate. This feature is especially critical for any prints with sharp corners or small curves. Setting the first layer print speed to 30-50% the standard print speed will be sufficient. Slow and steady my friends.
Nozzle and Bed Temperature
Increasing the nozzle and bed temperature 5-10 degrees during the first layer reduces the viscosity of the plastic and allows it to settle onto the print bed.
Skirts are a very useful printing feature that initiates the filament flow by tracing an outline a set distance from the part before moving onto the actual print. Usually 3 loops around the part are enough to establish a strong smooth flow but generally we use 5 just to be sure.
The brim is a very cool feature that keeps your print bonded to the print bed. It outlines the part, just like the skirt, except that it is actually connected to the print and creates more surface area for your print to bond to the plate. This feature is especially useful for long, thin parts as they are most prone to warping, especially when using ABS. A few millimeter thick brim should keep your prints grounded.
A raft is essentially a printed platform that your printer then uses as the base for your part. This feature is useful for many reasons. First, it offers some forgiveness if your bed is not completely level and creates a level platform that your part will then be printed on. Also, it creates a stronger foundation because your part will be bonded to itself instead of the build platform. Another reason why the raft is very useful is that dampens any uneven heating or cooling from the build plate that can lead to curling.
Keep these parameters in mind the next time you print and you be very happy with your results.
The team at 3D ProtoTech