The build platform is an essential part of any FDM 3D printer. To achieve the best part quality and avoid the risk of failure, it is essential to properly adjust and calibrate the build platform, as well as to check its regular condition.

The main symptoms of a problem related to the build platform are usually:

• Adhesion problems.

• Uneven height of the first layer.

• Lack of extrusion in the first layer.

In turn, these symptoms are a consequence of:

• Poor levelling of the platform.

• Poor flatness of the platform surface.

• Inadequate gap between the nozzle and the base.

• Problems of homogeneity of the heated surface.

• A bad condition of the adhesion surface.

Whenever a problem is detected that may be related to the printing base, these points should be checked and corrected if necessary.

1. LEVELLING OF THE PLATFORM

This is one of the most common maintenance tasks. How often it should be checked and adjusted depends largely on the quality and construction of the individual printer.

Image 1: Effect of base levelling on the height of the first layer. Source: Stemfie.org

The process of levelling the platform consists of adjusting the height of the platform in at least three points until the surface is parallel to the plane of movement in XY of the 3D printer head. There are multiple ways to adjust the platform level, although the most common is by means of 3 or 4 screws located at the corners. Some manufacturers include wizards in the printer software that facilitate the adjustment, but in other cases it must be done manually. To do this, the following steps must be followed:

1. Clean the surface of the printing base and make sure that there is no plastic or adhesive residue. Also clean the nozzle and check that there is not a drop of plastic on the tip.

2. Place a piece of paper or a 150 μm gauge at a point near the first adjustment screw.

3. Bring the head to that point and lower it to the 0 Z dimension.

4. Adjust the screw until the paper or gauge is trapped between the nozzle and the base but can be slid with slight friction.

5. Repeat the process at successive points.

6. When all screws have been tightened, they shall be rechecked and readjusted if necessary.

7. The platform is level when, after checking all the points, it is not necessary to readjust any of them.

Nowadays we are also starting to find 3D printers that do not allow manual levelling of the platform as they incorporate self-levelling or automatic levelling systems. In reality, these systems (BLTouch, SuperPINDA, etc.) are used to compensate for flatness defects in the platform, readjusting the height of the head in Z so that it maintains a constant separation at all points with respect to the surface of the platform. This system can also compensate for small levelling errors, however, except in printers with a solid construction, it is advisable to have both manual and automatic levelling.

It should also be noted that in printers without a self-levelling system or manual adjustment of the height of the end-of-travel Z-sensor, the gap between the nozzle and the base is determined by the thickness of the gauge or the paper used for levelling. In these cases it is recommended to use calibrated gauges with a thickness between 150 μm and 200 μm.

2. FLATNESS OF THE PLATFORM

Flatness should always be checked and adjusted (if possible) on a properly levelled platform.

Image 2: Effect of a base with poor flatness in the first layer. Source: Stemfie.org

The best way to check for flatness problems is to print a line pattern with a height of 1 layer on the base and check if in some areas the line is flattened or does not adhere. Three situations can occur when adjusting the flatness:

• Printers with a mechanical flatness adjustment: This is one of the least common cases. These 3D printers usually include aluminium platforms with a pattern of adjustable screws distributed along the platform. Tightening or loosening these screws causes small deformations that compensate for flatness errors. They are often complex to adjust and ineffective except for correcting simple keyways. They can usually be found on large format industrial 3D printers.

• Self-levelling printers: Printers with self-levelling sensors allow effective compensation for base flatness defects and small levelling errors. This is an increasingly common solution in FDM printers of all types and greatly reduces calibration work. There are various types of sensors, but the only universal sensors that are compatible with all types of bases are contact sensors, such as BLTouch, which is why they are becoming more and more common. In the case of optical, capacitive or inductive sensors, it must be taken into account that they are not compatible with all types of bases and that their accuracy depends to a large extent on the properties of the base used.

• Printers without a mechanical self-levelling system or flatness adjustment: Although it is becoming less common, many 3D printers in the lower price range do not have a self-levelling system. In these cases, it is advisable to use glass bases, as they have smaller flatness deviations. If significant flatness defects appear in these printers, the only effective way to compensate for them is to use balsa when printing.

Video 2: Raise3D contact self-levelling system. Source Raise3D

3. DISTANCE BETWEEN THE BASE AND THE NOZZLE

In addition to the correct level and flatness of the platform, the correct distance between the nozzle and the base must also be ensured.

Image 3: Correct distance between the printing base and the nozzle. Source: Stemfie.org

In general, when manually levelling the platform, the distance between the nozzle and the base is also adjusted. In some cases, on printers with a Z-sensor height adjustment system, a fine adjustment can be made to vary the height of the head, which is recommended when changing the nozzle to a nozzle of a different diameter. In systems with a self-levelling sensor, the distance from the nozzle to the base will depend on the activation height set in the firmware. Some 3D printers allow real-time adjustment of this distance, while on others it must be set correctly during the initial setup of the 3D printer. Although it is also possible to adjust the first layer height in the laminate setup, some laminating software automatically includes an extrusion compensation, i.e. if a first layer height of 150% is set, the extrusion factor will also be 150%. This is why it is recommended to have the distance between the nozzle and the base set correctly, regardless of whether you can make compensations in the software.

4. TEMPERATURE HOMOGENEITY AT THE BASE

In the case of many materials such as ABS or Nylon, a suitable base temperature is essential to ensure good adhesion. This is why problems of temperature uniformity on the surface of the base can lead to poor adhesion in colder or warmer areas.

Image 4: Thermographs of the base of different 3D printers. Source: Thomas Sanladerer

In the event that adhesion is not achieved on a base with a good and correctly calibrated surface, try placing the part in different positions on the base or slightly increasing the temperature. Due to the temperature tolerance of the materials, adhesion problems due to this cause are not common, although they can occur with materials that combine high cooling shrinkage and poor adhesion, as in the case of nylon.

5. CONDITION OF THE BONDING SURFACE

The adhesion of the first layer also depends to a large extent on the affinity between the printing material and the substrate material and condition of the substrate, which should always be kept clean and free of defects such as nicks or deep scratches. On substrates with textured coatings or plastics (Buildtak, PEI, etc.) that may be subject to wear, it is advisable to check the condition of the substrate before printing begins. In these cases, in order to extend the useful life of these components, it is recommended to vary the position of the parts in each print so that the wear is uniform. In the case of using adhesion solutions in liquid format (Magigoo, 3DLAC, etc.) it is important to clean the surface completely before a new application. If applied directly on top of the previous application, dust and dirt will be trapped and the performance of the product will be reduced.

Note: This guide discusses concepts in a general way and does not focus on a specific make or model, although they may be mentioned at some point. There may be important differences in calibration or adjustment procedures between different makes and models, so it is recommended that the manufacturer's manual be consulted before reading this guide.