Servo-Controlled Extruder Synchronization for Consistent Bead Size
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Solution Overview
Problem
In 3D printing, the constant extrusion rate of material extruders results in inconsistent bead sizes due to varying heat energy generation from the screw rotation, leading to inconsistent flow rates and bead sizes as the CNC machine moves at different speeds.
Innovation Solution
A servo-controlled system that synchronizes the speed of the extruder and pump, adjusting based on pressure and nozzle translation rates to maintain a consistent flow rate and bead size, using a polymer pump and servo signal coordination to ensure simultaneous and proportional speed changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the extruder operates at a constant steady rate to produce homogeneous melted plastic, then the material flow consistency is improved, but the bead size becomes inconsistent due to varying CNC machine speeds
Solution Approach 1:
The extruder screw speed is changed from constant to dynamically adjustable, allowing it to vary in response to CNC machine speed changes. The servo-controlled system adjusts the screw rotation speed in real-time to maintain consistent bead deposition despite varying traverse rates, resolving the contradiction between material flow stability and bead size consistency.
Solution Approach 2:
A feedback control system is implemented where the CNC machine's traverse rate is monitored and used to adjust the extruder screw speed. The controller receives information about the current printing speed and automatically modifies the screw rotation accordingly, ensuring that bead size remains consistent even when the printing speed varies throughout the build process.
2Speed
If the screw rotation speed is increased to match faster CNC traverse rates, then the material delivery speed is improved, but the heat energy generation varies causing flow rate inconsistency
Solution Approach 1:
The system replaces the traditional mechanical friction-based heating mechanism with an independent heating system. Heating elements directly heat the barrel and molten material without relying on screw rotation friction, allowing the screw speed to be adjusted for material delivery while maintaining stable material properties through controlled thermal processing.
Solution Approach 2:
The heating method is changed from friction-generated heat to externally controlled thermal heating. This parameter change allows independent control of material temperature and delivery speed, enabling the screw to rotate faster to match CNC traverse rates while maintaining consistent material viscosity and flow characteristics through precise temperature control.
3Manufacturing precision
If the extruder speed is reduced to maintain bead size at slower CNC speeds, then the bead size consistency is improved, but the productivity decreases
Solution Approach 1:
The extruder screw speed is made dynamically adjustable rather than fixed, allowing it to match the CNC machine's varying traverse rates in real-time. During high-speed printing passes, the screw rotates faster to deliver more material, while during low-speed passes, it rotates slower to maintain bead size consistency, thus preserving both productivity and manufacturing precision throughout the printing process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures a consistent and stable flow rate of molten material, resulting in uniformly sized beads and improved print quality by maintaining constant input pressure and adjusting for speed and temperature variations.
Implementation Method 1
Friction from the rotating screw, combined with heat from the barrel softens the plastic
Implementation Method 2
heat from the barrel softens the plastic
Implementation Method 3
a process of melting a very thin layer of a flowable material
Implementation Method 4
passing a continuous thin filament of thermoplastic material through a heated nozzle, which melts the thermoplastic material
Implementation Method 5
sensing a pressure of the flowable material, and adjusting at least one of a speed of the extruder and a speed of the pump
Data Source
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AI summary
An additive manufacturing method for delivering a flowable material from a nozzle of a programmable computer numeric control (CNC) machine, the nozzle being configured to translate along a first axis, a second axis perpendicular to the first axis, and a third axis orthogonal to the first and second axes. In one embodiment, the method includes actuating an extruder to form a flowable material, delivering the flowable material to a pump, sensing a pressure of the flowable material, and adjusting at least one of a speed of the extruder and a speed of the pump based on at least one of the sensed pressure and a rate of translation of the nozzle along one or more of the first, second, and third axes.