FDM Layer Bonding: Which Stage Directly Creates Adhesion Between Layers?
In Fused Deposition Modeling (FDM), a new filament strand is deposited while it is molten, and it bonds to the previous layer primarily because the molten material wets and fuses with the underlying layer, followed by cooling that solidifies the fused interface. This corresponds most directly to the stage Solidification and Bonding rather than to liquefaction or extrusion alone, and certainly not to G-code interpretation (which is the instruction-to-motion stage).
A useful way to map your options to the physical process is:
- Liquefaction: makes filament molten, but does not by itself create the bonded interface.
- Extrusion: deposits material, but the bond locks in when the interface solidifies.
- Solidification and Bonding: directly responsible for the newly deposited layer adhering to the previous one.
- G-Code Interpretation: controls motion, not the chemistry/physics of layer adhesion.
Therefore, the correct choice is: (iii) Solidification and Bonding.
FDM (Fused Deposition Modeling) Explained: How 3D Printing Works
Physical picture of layer adhesion in FDM
When the nozzle deposits a new bead, the filament is molten due to Liquefaction. The bead is then placed via Extrusion. However, the bond becomes a structural connection only after the molten-to-molten contact at the interface cools and becomes solid—this is the essence of Solidification and Bonding.
A simplified flow is:
How bonding happens from deposition to a locked interface
- 1Step 1
The filament reaches a molten state in the hotend so it can flow and wet surfaces.
- 2Step 2
The printer drives the nozzle so molten material contacts the top surface of the existing layer.
- 3Step 3
As temperature drops, the polymer at the contact region solidifies, forming a mechanical/entangled fused joint between layers.
- 4Step 4
The new layer is physically attached to the previous layer because the interface solidified after fusion.
Key idea
In FDM, extrusion places molten polymer; solidification/bonding creates the durable adhesion.
Why the other options are not the “direct” bonding stage
Liquefaction makes polymer molten, but bonding is not complete until the interface solidifies. Extrusion shapes/deposits material, but the structural lock occurs during solidification at the interface.
Mapping FDM stages to the bonding outcome
Liquefaction
Stage 1Polymer becomes molten and ready to flow."
Extrusion
Stage 2Nozzle deposits the molten bead onto the prior layer."
Solidification and Bonding
Stage 3Interface cools and fuses into a solid joint (layer adhesion)."
G-Code Interpretation
Parallel/controlControls movement/timing but does not itself fuse polymer at the layer interface."
Option-to-role fit for inter-layer bonding in FDM
Highest direct contribution to bonding a new layer to the previous layer.
Quick FAQ on the question
Knowledge Check
Which stage in the Fused Deposition Modeling (FDM) process is directly responsible for bonding a newly deposited layer to the previous layer?