3D Printing Basics: Levelling the Print Bed

The fact that a level printing bed is an important part of being able to get good 3D prints sounds pretty obvious. Unfortunately, even if a print bed looks pretty level, you can still end up with print issues in the first layer that spell disaster for the rest of your print. If your print bed is level, you should see a consistent print quality over your first layer. Some signs that your print bed needs levelling are:

• The filament not sticking to the print bed evenly
• The filament not leaving the print head in some places
• The height and width of the filament varying across the print bed
• Variations in the gap between lines of filament on the print bed

Preparation

Before you start the process of levelling, it’s a good idea to perform some basic preparation. First of all, it’s a great idea to check that your print head is clean, especially if you’ve already tried to print something before noticing that the bed needs levelling. Not only will excess plastic potentially interfere with your next print, but it can also interfere with the levelling process. To clean the print nozzle, heat it to the temperature the last used material was printed at and then wipe it off with a dry cotton cloth.

Tip: It is highly recommended that you use a set of heat resistant gloves when dealing with the print nozzle as it can get extremely hot. Typical temperatures are in the 210-260°C (410-500°F) range so heat resistant gloves are a must.

If the cloth doesn’t work, try gently using a brass brush. Be careful not to damage the nozzle with the hard brass bristles.

It’s also important to have a clean print bed as this can cause local height variations. Scrape off any large pieces of residue with a spatula. A knife or razer blade can also work on hard surfaces like glass but don’t use them on soft surfaces that could be easily damaged such as PEI. Once you’ve removed larger debris you can wash the print bed with soap in lukewarm water, if it can be removed. For non-removable print beds, isopropyl alcohol on a paper towel or cloth can work too, although it’s recommended that you check that the build surface can handle it before applying it, and that you dry it with a soft cloth afterwards.

Tip: Once you’ve cleaned the print bed, try to avoid touching the surface with your bare hands. The oils from your skin can grease the surface, adversely affecting the ability of prints to stick to it.

Levelling

Some, more advanced models of 3D printers include an automatic levelling system, it’s even possible to build your own. Typically, these function with a switch or proximity sensor that probes the print bed in various areas. The information from these sensors is fed back to the printer firmware and used to dynamically adjust the print height rather than to actually adjust the levelling of the print bed though. This can be much quicker than performing manual levelling, can allow for slightly uneven surfaces, and is generally very helpful, especially for newcomers to 3D printing.

Note: Some materials require printing on a heated print bed, as materials expand when heated it can be a good idea to perform the levelling process with the bed heated to the temperature you’ll use when printing. Depending on the heat you need to set this too, you may need thermal protection which can complicate the somewhat delicate task of making levelling adjustments. While you can heat the bed, and it may provide slightly better results, especially if you’re printing with high bed temperatures, it isn’t necessary to do so, levelling can be performed cold.

If you don’t have an automatic levelling system, you will have to level the bed manually. Even if you do have an automatic levelling system, it’s a good idea to manually level the bed occasionally, to minimise the allowances that need to be made. The first step of manually levelling is to home the print head using whatever option your printer control software provides to do so. This moves the print head to the 0, 0, 0 position, that’s 0 in the x, y, and most importantly, z dimensions. 0 in the z dimension is the height at which your printer will print the first layer. Next you need to unlock or disable the stepper motors so that you can freely move the print head in the x and y dimensions. Your printer control software should also offer an option to do this.

The print head should be very close to touching the print bed, the typical method used to get this right is to slide a sheet of paper between the two. The paper should be able to move with only a small amount of resistance. If the paper moves freely, there’s too much of a gap, if it doesn’t fit, can’t move or has more than minimal resistance, there’s not enough gap. It’s recommended that you test the levelling in each corner of the build plate and then in the centre. For particularly large build plates you may want to use more test points, although this will take more time.

Most build plates have their levelling adjusted through the use of levelling screws under each corner. The type of screw used can vary, some models may offer thumb screws while others may require tools like an Allen/hex key or a screwdriver to adjust.

Test each corner, one at a time with the paper, adjusting the respective screw as you go so the paper can move with only minimal resistance. Once you’ve adjusted the corners, check the centre of the plate too as this can help you diagnose a warped print bed. After you’ve completed a first pass, check each point again if you made adjustments after the first corner. Making adjustments to one corner can affect the levelling in the other corners, so double, and triple check and continue adjusting until each point is correctly levelled.

Tip: Be careful not to lean on the print bed as you’re levelling it as this can affect your measurements and your levelling result.

Once you’ve completed the levelling process, it’s a good idea to verify that everything now works as expected. To do so, print just the first layer of a model, or of a test print. If the levelling process was successful, the first layer should look almost perfectly uniform. If this isn’t the case, you may need to repeat the process again. If the first layer you printed looks good though, your print bed is levelled and you’re good to go.