This blog is coming a little later than I would have liked, but this week has been super busy. As mentioned in the first blog, I am currently writing up a paper for publication, as well as completing the material property testing for same.
The 3D printer that I have access to for my project is the Connex 500. This printer can print two materials at the same time (in different combinations to vary properties, or printing one material within another). The printer is shown in the first image below. The print tray, where components are actually printed is under the top panel. The two material cartridges are inside the door on the right and the two support material cartridges are inside the door on the left. This is clearer in the image on the right, with all panels and doors fully opened.
The build tray is shown below. The print head location is circled but as they are all downward facing they cannot be seen in full detail.
This printer uses Polyjet technology and uses liquid ink. There are two print heads per material, each has ~100 openings to allow droplets to be deposited to build up each layer. A layer of the liquid is immediately cured by UV lamps and becomes solid. This layer then acts as a foundation for subsequent layers. Printing a solid block is easy, as the first layer is deposited and cured on the print tray, the second layer printed on the first, third layer printed on the second, and so on.. But, in cases where the object is not a completely solid shape (for example, the hand skeleton below), support material is needed to create the same solid foundation for the next layers. This material is waxy in texture and is washed off as part of the post-processing. The hand was printed from the bottom up, in the same orientation as in the photo below. In this particular print, there would have been four or five times more support material used than the material that the hand is made from.
The image on the left below shows the hand being printed. The black material is the bone, white-ish material is the soft tissue and the dark grey is the support material. The second image shows the hand with support material removed.
This 3D printer was one of the more expensive printers on the market when it was released in 2014, selling for $250,000! The Connex’s main selling point is that it can print multi-material parts. It has very thin layers (as thin as 0.16mm, but more commonly we use 0.32mm) which give very good print resolution. One of Stratasys’ materials is a transparent, biocompatible ink (MED610) for medical and dental use; another major factor when the research group were deciding to get this particular printer.
The size and cost of the machine might lead you to believe that it is complicated to operate, but in fact it is quite straightforward. The software is very user friendly and the printer itself is easy to operate. I have been working on the machine for a few months now and I feel like I have learned how to do most tasks in relation to printing and general maintenance.
I am now able to get the printer back to perfect working conditions after taking it apart (to do test prints with the material I am developing as part of my research project). At the start it was quite intimidating to mess with such an expensive piece of equipment, but after a few successful attempts of putting it all back together I am getting more confident. This week was my first time ‘hacking the printer’ on my own. Even though the print quality was not as good as I would have liked (the print heads blocked up significantly), I learned an awful lot working by myself. Second time ‘hacking the printer’ on my own should give better results!