![]() I use these to smooth out any coarse artifacts on the model. I have a couple of different tips in different shapes which I use like hot spatulas. I use a little PLA filament as “solder” if I need to add material. Generally I manipulate the PLA using soldering irons which work great when small parts of the model need to be repaired, fused, remove or added. Once all the parts are printed I glue them together, usually using a small amount of superglue first to keep them in a fixed position and then I seal the seam using a soldering iron. Colored PLA (even that “white” variety) has additional additives which do not burn out well. I almost always choose clear PLA, because it burns out the cleanest. A thicker skin will be easier to keep watertight. This will later lead to ingress of plaster-slurry which can end up being embedded in the glass (see section below). Furthermore a thin skin is more likely to have a small hole that might go undetected. Especially during solvent smoothing the model can collapse or distort if it does not have sufficient internal support. In post processing, especially smoothing, I found having a thin skin to be problematic. Even though the print is just a throwaway positive I actually print it with a relatively thick skin and a reasonably large amount of fill density. I then print each part on a typical PLA extrusion printer. In some cases I use 3 or 4 cut planes, especially when the models get large, here I have to work carefully to take in account the printing volume and balance number of pieces vs printability and overhang avoidance. ![]() Choosing the cut plane is critical to minimize the number of overhangs during printing, which usually yield worse surface quality and waste support material. Since macromolecules don’t have a flat surface I almost always cut the model into two parts, creating a large surface for each half to be printed on. Somehow this scale worked well for what I was doing and so it has become my standard. The mixing of metric and imperial units is a bit funny, but it came from when I was making hand-formed copper models where my raw materials were in imperial units but the units of molecular modeling are Angstrom or nanometers. First I have to decide on a scale, though in practice all my current work is at the same scale of 4 Angstrom/inch. In many cases I will make changes at this stage. These raw models I then load into Blender for further editing. Finally I calculate a solvent accessible area and save the coordinates and faces as an. There I can manipulate the torsion angles to change the overall shape in a way that makes sense. For multipart pieces I also assess the fit and do other artistic edits in terms of choosing a conformation for flexible molecules (such as the carbohydrate in the lysozyme piece) which isn’t rigidly determined. It’s good to have some sort of idea even this early of how it’s going to work, even though in practice I often change my mind later as I get to know the piece. Somehow a flat surface is needed or some sort of cradle. At this stage I think about the final presentation and mounting. Once I’ve chosen a candidate I build an initial model using a molecular editor such as RasMol or PyMol. Does it have structural features that make it unrealistically difficult ?.Is its size prohibitive in terms of equipment I have and time expenditure.Is it feasible to cast, process, mount etc. ![]() Does it have a particularly striking shape when rendered volumetrically or through ribbons ?.Is there symmetry in quaternary structure, or a regularity to its fold?.Does it have historical significance in terms of its discovery ?.Does it have an important function that is readily explainable and accessible?.I often get asked how I choose my models. I begin the process of casting a molecular sculpture by reviewing different possible macromolecules for their potential. Specifically I use this technique to make sculptures of protein molecules rendered as their solvent accessible surface, which are created from their scientifically precise chrystallographic coordinates. ![]() 3D printing glass and bronze: Lost-PLA castingįor a few years now I have been experimenting with casting glass and occasionally bronze from 3D printed positive models. ![]()
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