3D Printing of Viscous Materials
3D Printing of Viscous Materials
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Problem: Design and manufacture a FDM printing hotend that can extrude chocolate structures
Problem: Design and manufacture a FDM printing hotend that can extrude chocolate structures
System Description
System Description
Our system was investigating a potential design of a low-cost interchangeable extruder attachment for standard FDM printers that can melt viscous material such as chocolate. The goal was to come up with a design that could realistically be used by bakeries to make custom chocolate 3D structures. The design we settled on used a heated syringe chamber that keeps the chamber of chocolate in a molten state. The design involved parts that can be manufactured using the FDM printer and components found in standard FDM printer hotend. We thoroughly tested the design to decide on the necessary modifications to turn most standard PLA prints into chocolate prints.
Process
Process
To be able to have the system fully operational my team had to perform tasks that can be broken down into three main categories
Design and Modeling
Design and Modeling
Analysis
Analysis
Implementation
Implementation
design and modeling
design and modeling
We started the design process by brainstorming methods to extrude chocolate reliably. The main constraint on the design was to make a system that is both low-cost and easy for a novice to manufacture. This meant that we had to scrap ideas including pneumatics or more intensive electrical wiring. To simplify the design further, we re-used components from a standard FDM printer hotend and all other parts could be printed from the FDM printer itself. This meant that the user wouldn't have to do any wiring and only require a few prints prior to assembly. To keep the system food-safe, we made sure that the only components touching the chocolate were standard cookware.
Analysis
Analysis
Once we settled on a design, we needed to be able to characterize the system's behavior. Two questions in particular were of most importance to us. The first was the required force to extrude the chocolate. This was important as we didn't want to complicate the design with a gearing system, but we had to verify that the hotend stepper motor was strong enough to direct drive the system. To do this, we set up a physical experiment where we used a scale to find the required extruding for for multiple different chocolate brands. This allowed us to verify that we can safely direct drive the system. The second question was whether a single heating element could keep the chocolate in a molten state. To answer this, we ran a simple thermal FEA to estimate the steady state temperature of the chocolate. We eventually verified this answer after assembling the system.
Implementation
Implementation
After assembling the system on the 3D printer, we had to find the optimal conditions to be able to print the chocolate structures. The first issue we had to tackle was what printing what were the ideal printing temperatures and extrusion speeds. We started with a baseline temperature and a slow speed. From there, we kept increasing the speed until we came up with a set of reliable printing conditions for multiple chocolate brands. The second issue was that a standard slicer was not meant for our application. To this end, we modified a standard cura slicer to change the beginning and end Gcode. This allowed for easy setup and reliable printing.
End Products
End Products
The end result of the entire project yielded the following products:
A hotend attachment that can print chocolate structures.
Modifications to the beginning and end Gcode to allow for reliable printing.
A library of printing conditions for different chocolate brands.
A user manual detailing the proper use and maintenance of the device.
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