Pauses in 3D printing: inserts and color changes

When a user of a 3D FDM printer reaches average knowledge, he seeks to increase the complexity of his printed pieces, both in terms of functionality and finishing. Next, a series of tips for increasing the performance of a 3D printer are discussed thanks to the programmed stoppages and metal inserts.

Scheduled stoppage

The scheduled stoppage is a very simple action to perform and that many users are afraid to do. The first step to stop is to know exactly at what height (in millimeters) you want to stop printing for whatever reason. Depending on the lamination software used by the user, it can be found directly (X layer number) or indirectly (X mm). In the latter, you must look for the number of the layer where you want to stop and multiply it by the thickness of each layer to obtain the total height in millimeters.

Once the total height is known, for example 14 mm, there are two ways to program the stop: directly in the GCode or in the lamination software.

At the beginning of 3D printing, the GCode of a part was modified to program a stop at the desired height. For this the user must look for the layer height (Layer) and in the next line of the code enter the command M600. This command is the change of filament that brings predefined 3D printers that use Marlin or derivatives.

Image 1: GCode with M600 stop

Currently there is another method of stopping in a much simpler way. Lamination softwares like Cura3D have a plugin to perform different types of stoppages. Since this way it is very easy to perform this action, the following paragraphs explain the possible types of stoppages.

Filament change

The filament change stop is an ideal action when you want to make pieces in several colors with a single extruder, although the user must take into account when designing that this is only valid for color changes along the Z axis and at different layer heights. To program the change of filament with the Cura3D, go to "Extensions -> Postprocessing -> Modify GCode" and select "Change Filament", where you must select the layer height, the retraction length and insertion of the filament and the position where it is desired to move the HotEnd during the stop. This configuration can be repeated as many times as the user wishes.

Image 2: Change filament with 3D cure. Source: Cura 3D

Stop at the desired height

Performing a stop at a certain height is very useful to introduce some element into the part that is being printed, such as other printed parts, magnets or nuts. Incorporating nuts inside printed parts is a really interesting and productive action when manufacturing functional parts. For this, the design must be carried out taking into account the size of the nut (length between faces on the two axes), the necessary clearance of the housing and the position of placement of the nut itself. If the position of the nut leaves spaces without material, something common when the nut is not placed parallel to the printing base, it is recommended to print a piece to place it above the nut itself, which manages to occupy the free space until the layer height that has been stopped. The following image shows what was explained above; the purple part is the base piece, the ocher part is the nut and the blue part is the printed piece to occupy the unwanted gap.

Image 3: How to insert a nut in an inclined plane. Source: Markforged

This type of stop is programmed in Cura3D in the section: "Extensions -> Postprocessing -> Modify GCode" and select "Pause at height ". Both with this type of stop and with the "Filament Change", when the 3D printer reaches the selected height, it stops printing until the user resumes it again by pressing any of the buttons on the screen.

Metallic insert

An alternative to incorporating nuts in the middle of a print is to use metal inserts. Independently of the type of insert, the user must be clear about the two key factors of the inserts: resistance to extraction and resistance to rotation. The resistance to extraction is the opposition of the insert to leave its housing when the screw is tightened. This is a value that can be increased by increasing the length of the insert. The resistance to rotation is the opposition of the insert to turn on itself when tightening the screw. In this case the resistance increases with increasing hole diameter. Another aspect to be taken into account in a generic way is the diameter necessary for each type and size of insert, being necessary to consult the manufacturer's technical data sheet to obtain the recommended hole diameter.

With the above points clear, in 3D printing it is usual to use two types of inserts: heat threaded inserts and self-tapping threaded inserts.

Heat threaded inserts

These types of inserts are used with thermoplastic materials, which melt at low temperatures. The way of use is very simple and only requires having a heat welder or other heat source, which by hot contact the insert. The geometry of these components is designed so that when the plastic melts from the walls of the hole, a resistant union is formed, which prevents it from coming out or turning on itself.

Image 4: Introducing heat insert. Source: Markforged

These types of inserts are ideal for most parts and materials used in 3D FDM printing.

Self tapping threaded inserts type ensat

Certain materials used in 3D SLS and resin printing melt at higher temperatures or do not behave stably when heated. In these cases it is recommended to use self-tapping threaded inserts (Ensat bush).

This type of insert allows the union by screws with high load capacity and temperature. Its conical shape at the bottom end accompanied by a cutting groove, create the thread automatically in the hole. To insert them, you only need a screw with the inside diameter of the insert and two nuts to make locknut.

Image 5: Locknut system. Source: Norelem

For these two types of inserts there is also a special tool, recommended for users who perform this type of process as usual.

Conclusion

Following the advice mentioned above, any user of a 3D printer can increase its field of application thanks to increasing the functionality of its parts.