3D printed parts are generally not used alone, they are generally mounted to an assembly. One of the methods used to mount the part is through inserts. There are many insert designs, each with their own strengths and uses. The right insert design for you will partly depend on your application. Recently Raise3D tested 6 commonly used brass insert designs in 3D printing using two different 3D printing materials, Nylon X and PLA.
In most 3D printing applications, a 3D printed part is not used alone. It is commonly used as part of an assembly, where it will be mounted to other parts within a system. Using a threaded brass insert can simplify the process of modeling parts, and help better guarantee thread consistency across multiple prints. Brass inserts also are better suited for repeated use and are less likely to degrade over time.
The difference between pressed inserts and heat set inserts is that one uses pressure to install the inserts while the other relies on heat.
A pressed insert is when an insert is aligned into a predetermined hole, and inserted using pressure and force. One example of how this can be done is by drilling a hole and using a hammer to lightly tap the insert into the hole.
A heat set insert is when an insert is aligned with a predetermined hole, and heat is applied to the insert. This causes the insert to heat up, melting the surrounding material. When pressure is gently applied, the insert will go down to the desired depth. One way to heat the insert is by placing a soldering iron to the insert.
We tested six common designs for installing inserts in a 3D printed part.
1. Horizontally Oriented Printed Parts using Brass Insert:
These parts are produced with the model-oriented so that the layer lines are perpendicular to the direction of the insert hole path through the part.
2. Vertically Oriented Printed Parts using Brass Insert:
This style uses the exact same design and model as the previous method, however, the part is oriented so that the layer lines are parallel with the path of the hole through the part.
3. Reverse Insert:
This design features an insert that is installed through the part to end up recessed under the outer surface. A gap, similar to an insert hole, runs through the entire part and the insert is driven through the part where the bolt will be used on the other side. This method is better suited for shallow parts.
4. Embedded Nut:
This design features a nut that is dropped into the part in the middle of the 3D printing process.
5. Slotted Nut:
This design features a slot in the back that the nut is dropped into.
6. Printed Thread:
The thread is modeled into the part’s geometry and printed as part of the piece itself.
Each of these designs has its own uses and benefits. Depending on the application, one design may be better suited than another.
To test the six different insert designs described above, Raise3D designed a carbon fiber nylon printed base at 90% infill which remained mounted to a frame. Then insertable core designs which only took 45 minutes to print, were inserted into the carbon fiber nylon base. The cores were designed in accordance with the 6 different insert designs in two different 3D printing materials, PLA and Nylon X.
For this design, the cores were printed and the inserts pressed in from above.
The PLA printed cores tend to break away at the back area in the direction of the force. However, the Nylon X cores almost slip out rather than breaking like the PLA printed cores.
Horizontally Oriented Printed Parts Using A Brass Insert
The cores so that the layer lines are parallel with the path of the hole through the part. The inserts were pressed in at the top.
The PLA printed core behaved more like the Nylon cores, in that the inserts slipped out. The Nylon X printed cores broke in the same way as the Horizontal printed holes.
Vertically Oriented Printed Parts using Brass Insert
In this design, inserts were placed backward through the parts. The nut catches on a lip, which embeds the nut further into the 3D printed parts.
The PLA printed core almost separated from the main block while the core insert almost stayed in the block entirely. However, it reached 100 pounds before breaking. The deeper the inserts are set in, the stronger the inserts will be. The Nylon cores reached up to 80 pounds before failing.
Reverse Insert
Front of the Reverse Insert
In this design, nuts were used as the inserts. During the printing process of the 3D printed cores, the printer is told to pause at a certain height directed in the Gcode. Only one pause was used to create these inserts, but this process can be repeated multiple times in a single print.
This means the cores will print up to a certain height and pause. When the printing is paused, a nut is dropped into the part, before printing continues, sealing the nut inside the cores.
For both PLA and Nylon cores, the tops of the cores tended to break off the upper layers of the core insert around the pause height instructions. However, the PLA printed cores reached up to 62 pounds of force before breaking off the top while Nylon X reached 58 pounds of force.
Embedded Nut
In this design, nuts were used as the inserts again. However, rather than dropping the nut in and continuing to print, the nut is slid into the 3D printed part afterwards.
Both PLA and Nylon cores broke in a similar fashion as the cores from the Embedded Nut design. However, PLA reached to 67 pounds of force before breaking, while Nylon X reached 80 pounds before breaking.
Slotted Nut
This design does not use any inserts or nuts. The thread pattern is already printed into the part.
PLA printed cores took about 67 pounds before they broke. The Nylon X cores reached 112 pounds before they broke.
Printed Thread
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