Design and development of the portable build platform and heated travel envelope for the Multi3D manufacturing system
The final product functionality of parts produced by Additive Manufacturing (AM) can, in part, be improved by the inclusion of multi-material capabilities. The “Multi3D system” that is under development at The University of Texas at El Paso uses material extrusion printing (or fused deposition modeling), solid conductor wire embedding, direct-write, component placement, and micromaching to enable multi-material fabrication. The Multi3D was designed to transport a workpiece between manufacturing stations via a six-axis robot, portable build platform (PBP), and a controlled temperature environment or chamber that travels to each manufacturing station. The heated travel envelope (HTE) was included to mitigate thermal shrinkage (and eventually warping) that occurs when a thermoplastic is subjected to a decrease in temperature within a short time frame. An end-effector was also designed to allow the six-axis robot to interact and handle the PBP and HTE. Discussed in this work is the design and construction of the HTE as well as its performance in terms of maintaining a stable temperature while considering the imposed weight and dimensional constraints. The HTE design includes a compressible high temperature bellow “door” which allows it slide over builds and increases the height of builds (~22 cm) which can be produced in the Multi3D system. The HTE is capable of maintaining a 150 ± 8°C environment with its convective heating system, which is the baseline set for building parts with polycarbonate, specifically 145°C. The temperature change (drop) of parts is reduced by 71% with the inclusion of HTE in the transportation process. The quantified temperature drop without the HTE during transportation was approximately 21 °C in comparison to 6 °C with the HTE. The construction and performance (e.g., locating accuracy) of the PBP are also discussed. The PBP was designed around the “Platen” build platform to replicate its abilities but in a form that allows it to be portable. The PBP is able to receive vacuum (-42.3 ±8.5 KPa) supply for restraining sacrificial build sheets in two forms, from the station of the Multi3D system it is placed in and from the end-effector. The PBP locates accurately into the FDM system, in a form that maintains the FDM’s achievable accuracy of ±38 ?m, via the use of three locating pins and its vacuum fitting. The locating accuracy of the PBP was determined by printing “stair step” parts which were analyzed for layer shifting. These results were compared to stair steps printed in an unmodified FDM system as a control. The layer shifting was measured to be +50.8 to -38.1?m for non-paused builds and +63.5 to -50.8 ?m for paused builds on both machines (modified and control). This gave indication that the modifications done to the FDM machine and the portable build platform had no direct effect on the achievable accuracy in parts with this specific geometry and these processing conditions. Ultimately, the Multi3D system will be utilized for Aerospace applications to manufacture components for Unmanned Aerial Vehicles (UAVs) and satellites, but other applications where disparate materials are required can be envisioned. This can be accomplished with these components or subsystems which were developed for material handling within the system.
Ambriz, Steven Daniel, "Design and development of the portable build platform and heated travel envelope for the Multi3D manufacturing system" (2015). ETD Collection for University of Texas, El Paso. AAI10000784.