Prints Charming

In previous posts, I’ve integrated other materials pretty easily into my prints just because of the nature of their design. However, as we go deeper into co-processing, I would like to bring up another scenario. We have dealt with smaller parts that can be printed with or without involving co-processing; the bolt for the impossible bolt can still be printed by itself, although it would no longer be that impossible. Likewise, the sunglasses can be printed as just frames, with no lenses. What kinds of parts would need co-processing to print well?

Because of the nature of FDM printers, the filament at any layer needs to be supported by something. Some FDM printers, like the MakerBot Replicator 2, can print overhangs that extend about 60 degrees from the vertical without collapsing or compromising print quality, and they can print arches and vertical holes fairly easily. Either prints need to be designed to incorporate these features if an overhang is necessary, or, we can use co-processing to add in other parts and modify our print.

For this post I’ve created a small charm for my keychain by co-processing a quarter. The Thingiverse files are available here. All of the files are blank templates, so you can edit the faces that sandwich the coin however you want. This part cannot be printed on its own. However, the quarter fills the space needed to support the upper part of the structure, meaning that when the quarter is placed in at a precise time, It can serve as support for the printer to lay down filament on top of. The only challenge is putting the quarter in at exactly the right time, so that the extruder head doesn’t hit the rim of the coin!

The gap in the center of this cross section of the part is where the coin will go during the print.
The gap in the center of this cross section of the part is where the coin will go during the print.

By creating these “supports” through co-processing, we can not only make new and interesting pieces by placing pre-fabricated objects into prints as they are being made, but we can also place pre-made shapes and structures underneath prints as they are printing to generate printed geometries that were impossible or difficult to make with support material.

The finished piece, with a quarter sandwiched between my initials.
The finished piece, with a quarter sandwiched between my initials.

In order to accomplish co-processing in this way, much thought needs to be put into tolerancing your print. There is some chance that the printer head will be too far away from the co-processed part, in which case the filament will not adhere to the part. On the other hand, if the part is added to soon or is too big for its designated “hole”, the extruder head will ram up against it. Although co-processing can sometimes be very difficult to deal with, there are many possibilities and potential places for it to go. If you have any ideas about it, let me know!

Alex

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