Basic parameters of lamination.

When preparing a file for printing, it is very important to know the basic parameters and how they work. The number of parameters available in today's laminating software is increasing, however, unless you have an in-depth knowledge of the software and the technology, it is advisable to start by modifying only the basic ones.

Three groups of parameters can be distinguished: those that depend on the material, those that define the print profile and those that define the hardware. Depending on the software, they may appear in different categories or mixed together.

Parameters defining the hardware

They are usually related to the nozzle of the printer and need to be modified when changing to a nozzle of a different diameter.

• Nozzle diameter: This is the actual diameter of the nozzle used. If a 0.4 nozzle is used, 0.4 mm should be selected.

• Extrusion width: This is the actual width of the extruded line, it depends on the layer height used and is usually larger than the nozzle diameter. To know the real value it is necessary to print a cube in cup mode and measure the real wall thickness. For a layer height equal to 50% of the nozzle diameter, the extrusion width is usually 20% larger. That is, if a 0.4 mm nozzle and a layer height of 0.2 mm are used, the extrusion width will be 0.48 mm.

Material parameters

The material parameters are those that are directly dependent on each material and therefore have to be changed when changing materials. The most important ones are:

• Printing temperature: Defines the temperature of the nozzle during printing. This is a data provided by the manufacturers, but it is recommended to calibrate it for each printer.
• Base temperature: Like the printing temperature, the manufacturer's information should be consulted for each material. Defines the temperature of the base during printing.
• Chamber temperature: Only available in printers with heated chamber. Defines the temperature of the chamber during printing. A temperature slightly lower than the Tg of the material is usually used.
• Flux: This is a compensation factor of the relative extrusion speed to the printing speed. A value less than 1 (or 100%) will result in less extrusion while values above 1 (or 100%) will result in over extrusion. Although generally the correct value is 1, some materials such as PLA or PETg may require lower values (0.9-0.95) while others require higher values, such as TPE and TPU (1.05-1.15).
• Shrinkage rate: Together with the shrinkage distance, they define the shrinkage values of the material. This parameter is also highly dependent on the type of printer used. It must be set correctly for each media-printer combination. It is generally in the range of 20 - 40 mm/s.
• Retraction distance: This is the distance the filament is retracted before each displacement. Like the retraction speed, it must be set correctly for each material-printer combination.
• Cooling fan speed: defines the speed of the layer fan and thus the cooling of the part during printing. Consult the manufacturer's information to find out whether or not the material requires this function. With ABS it is usually always switched off, while with PLA it is used at maximum speed at all times. Other materials such as PETg or ASA may require the use of the coating fan at low speed (20-50%). Generally laminating software allows different speeds to be selected at different heights, as in any case the fan must be switched off in the first layers to ensure good adhesion to the platform.

Parameters defining the print profile

These are parameters that will define the quality, finish and resistance of the final piece. They do not depend directly on the material, so it is not necessary to adjust them for each material. They can be classified into various categories depending on the element they affect.

Layer parameters

• Layer height: Defines the thickness of each layer. The sweet spot usually coincides with half of the nozzle diameter. For example, for a 0.4 mm nozzle it will be 0.2 mm, while for a 0.6 mm nozzle it will be 0.3 mm. Layer heights greater than 75% of the nozzle diameter should never be used.

• First layer height: Defines the height of the first layer, which is in contact with the base. It can be set to a value slightly lower than the layer height, in order to improve the adhesion to the base.
• No. of bottom solid layers: Defines the number of dense layers to be printed on the bottom of the part. The number of lower solid layers multiplied by the layer height defines the wall thickness of the part at the bottom of the part. It is recommended to use a sufficient number of layers to obtain thicknesses greater than 1mm.
• Number of upper solid layers: Defines the number of dense layers to be printed on the upper part of the part. The number of upper solid layers multiplied by the layer height defines the wall thickness of the part at the top. It is recommended to use a sufficient number of layers to obtain thicknesses greater than 1mm.

Perimeter parameters:

• Number of perimeters: Defines the number of perimeters the part will have. The wall thickness of the part will be the number of perimeters multiplied by the extrusion width. It is recommended to use a minimum number that allows to obtain a wall thickness of at least 1 mm.

• Cup mode: This is a function present in most software. When activated, only one perimeter will be printed continuously throughout the part.

Image 1: Piece printed in cup mode. Source: Prusaprinters

Filling parameters:

• Filling density: This is the proportion of filling inside the part. It is defined as the volume occupied by material with respect to the empty volume, so that with a filling density of 50%, half of the internal volume of the part will be empty. It is usual to use values between 10 and 30%.

• Fill pattern: Defines the geometry of the fill pattern. Not all software has the same, but they can be classified in three categories:

• Two-dimensional or planar: These are the most common, such as rectilinear, grid or triangular. They are usually the fastest, but generally produce a high anisotropy of the part.

• Three-dimensional: Such as the gyroid or cubic. They provide lower part anisotropy, but usually involve longer printing times.

• Concentric: These are suitable for maximum flexibility in flexible parts. In rigid parts they usually provide better finishes, as there is no overlap with the perimeters, but the mechanical properties of the part will be minimal. They can be suitable for visual models and mock-ups.

Image 2: Different infill patterns. Source: Prusaprinters.org

• Fill overlap: This is the distance that the fill lines overlap on the perimeters. A high value will improve the strength of the part, but the fill pattern may become visible on the surface of the part.

• Combine fill: This is a very useful function to reduce printing times when very low layer heights are used. For example when printing with a layer height of 0.1 and a nozzle of 0.4, it is possible to combine infill every third layer, so that the walls will be printed with a layer height of 0.1 mm and the infill with a layer height of 0.3 mm, drastically reducing the printing time without affecting the surface finish of the part.

These basic parameters, together with the correct speed settings, additions to the base and correct media settings, allow for complete and efficient print profiles.