Antonio Montes de Oca Gomez
Printing parameters for parts with high mechanical performance.
3D printed parts have a reputation for sometimes not being durable enough for tasks that involve some considerable amount of mechanical stress. This is partly true if, at the time of design and/or manufacturing adaptations or modifications, certain parameters are not taken into consideration to improve the durability of the parts. Like many things in engineering, 3D printer operators can make modifications to the manufacturing process so that parts perform correctly or as expected in the field.
Keeping up with the layout of previous blogs, here is a list of just some of the parameters (for printing by FDM method) that at Kenko Solutions we usually adapt to meet the needs of our customers:
Choosing a thermoplastic: One of the main unknowns to solve when manufacturing parts by 3D printing. The main factor that intervenes in our choice is what temperature the printed pieces will be exposed to.
Firstly, if the parts will not be exposed to sunny environments, we can choose to use PLA due to its ease of printing and availability in the market.
Secondly, when parts will be moderately exposed to sunlight, we recommend using PETG.
In third place, if your parts are going to be continually exposed to hot environments and UV sunlight, your best choice may be to use ASA.
As the printing temperature increases, the difficulty for parts to print successfully also increases. A numerical way to determine the thermoplastic to use can be by knowing the temperature of the environment beforehand. If the ambient temperature is less than 50ºC, use PLA; if it is less than 70ºC, PETG; and for less than 100ºC, ASA. For higher temperatures PEEK, ULTEM or PEI can be used.
Another characteristic that can influence the choice of thermoplastic is to look for different mechanical or commercial properties. A general guide would be the following:
PLA: Higher availability, low price, easy printing, higher force tolerated before failure, low stringing, lower ductility, low glass transition temperature.
PETG: Medium availability, ductile fracture, medium glass transition temperature, medium stringing.
ASA: Reduced availability, higher ductility, high glass transition temperature, high stringing, hygroscopic material.
Print orientation: One of the most important factors that will determine if the part fails or not. Parts that are printed with the axis that will carry the most mechanical stress parallel to the X or Y axis of the print bed (XY or horizontal orientation) will have a better chance of withstanding the stress without breaking. The following images show two scenarios for the same model, but with different print orientations. In the image on the bottom, the part would break easily, the image on the right would tolerate higher stress. The first image shows the intended use of the part with the red arrows symbolizing the axis that will have the greatest mechanical stress.
The number of perimeters: Beginners in the world of 3D printing commonly consider that modifying the infill percentage is the easiest and most direct way to improve the force that the parts can tolerate. However, the number of perimeters is the parameter that has the greatest impact to improve this property. To give an example, a part with 75% infill and 2 perimeters is 20% weaker than a part with 15% infill and 3 perimeters (by making a relationship between the force tolerated divided by the weight of the parts).
Printing temperatures and ventilation: Adjusting temperature and ventilation values to improve mechanical properties is less common. This could be used as one of the last resources to increase the stiffness of the parts. By printing the parts with higher temperature and lower filament cooling fan speeds, it allows the deposited filament to fuse better with lower layers of plastic. The tolerated force can be increased up to 60% just by changing these two parameters. However, not cooling the lower layers of plastic causes the new layers to be deposited on plastic that is not completely solid, so the upper layers will not be properly positioned. This will affect the surface aesthetics of the parts. The dimensions of the printed model will greatly deviate from the model intended to be printed and could even result in a complete failure of the print.
Change model design or mode of use: There will be situations in which it will be more convenient or totally necessary to re-model the part and add reinforcements in the most critical or failure-prone sections. One possible option is using generative design to optimize parts given a magnitude of force and direction.
These were some of the recommendations and factors that we take into consideration when manufacturing 3D printed parts. The 3D models that we receive sometimes need modifications in their design so that the parts meet the mechanical requirements that our customers want. It is important to know the environment where the pieces will work and how they will be used. If you want to know more bout how you can optimize your parts from the modeling check out our previous blog
At Kenko Solutions, we will make the necessary recommendations and make the necessary adjustments to your model so that you have the confidence that your parts will operate as expected.