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Opinion: FDM Printers Are Still Very Useful for Modeling


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I just realized this new 3D printing section was here and I thought it might be helpful to share a bit about the ways that I use it in my work. 

 

I recently got back into model making (~2017) after not having done it since childhood. My focus is scratch building science fiction subject matter. 

 

I have a resin printer and a FDM style printer, both relatively inexpensive, that have become an important part of my work flow. 

 

Here's my souped-up Tevo Tarantula:

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 FDM ( fused deposition modeling) style printers seem to be going out of favor with the recent arrival of cheap, high resolution resin printers. But don’t write them off yet. I get a ton of use out of mine. If you’re unfamiliar, FDM printers use a heated nozzle to extrude plastic filament to draw your part a layer at a time (sort of a high tech hot glue gun). I bought mine as a kit directly from China for $190 US. I chose this particular printer because it was cheap, well liked, upgradeable, and had an active user community. But above all, because it could extrude polystyrene filament. The importance of this point can not be overstated... it can print styrene. This means the resultant parts are strong and lightweight, sand easily and can be glued using common modeling cements (Tamiya extra thin, in my case). 

 

Polystyrene filament is sold under the name HIPS (high impact polystyrene). It’s sold as a support material because it can be dissolved using a special solvent*. 

 

What most folks don’t seem to realize is HIPS is a great material to print with on its own. In my experience, HIPS filament prints beautifully. And it's cheap and goes a long way; I'm still using the $20 spool I bought almost 4 years ago.

 

FDM printers aren’t great for small details. The parts also will exhibit noticeable layer lines or striations. There are games you can play to reduce this, but I just except it as a limitation of the technology. A light sanding removes the highs and filler takes care of any voids. The main way I utilize this printer is to create large forms that would be difficult to make in other ways and then add detail using kit parts. Here are a few examples of how I’ve been using the FDM printer with styrene filament:

 

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For my Airship, I needed to created the segmented insectoid, bulbous shape seen in this photo of the finished model. I designed the part to be printed in three pieces, letting the locations of the segments define where the part was split. The assembled parts were registered by a 1/2 inch aluminum rod to keep them concentric. Here you can see one of the segments being printed. Note the honeycomb pattern on the interior of the part. This saves on material use without sacrificing much strength. You can also see the central hole for the aluminum rod.

 

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Sandpaper and auto body putty were use to achieve a smooth surface. The part was primed with automotive primer from a spraycan and wet-sanded. The pile of elliptical rings on the left was also printed in styrene.

 

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Once the surface was acceptably smooth, I feathered back the primer with 600 grit paper where the rings needed to go and bonded them with Tamiya cement. Then the part was detailed with kit parts. Here’s the final result in primer:

 

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The next example is from my model of the Nostromo Airlock from the movie, Alien.

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The walls had some tricky angled sections. I decided to print an underlying structure to make assembly easier. Here is the printed support. They’re about 6.5 mm thick. The holes in the upper and lower areas are for a styrene tube to align and strengthen the two supports. I could have cut these by hand, but these are very accurate and I was downstairs reading a book while they were printing. Multi-tasking.

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The supports were then clad with sheet styrene for the walls.

 

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Another more novel use for my FDM printer that I’m still exploring, is printing forms to vacuum-form over. Here’s another example from the Nostromo Airlock model. To make the recessed dents in the airlock doors, I printed the positive shapes in styrene. These were glued to some thin plasticard to lift them slightly off the bed of the vacuum former.

 

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The resultant “dents” were then cut out and glued to the rear of the doors. Here’s the result.

 

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I'm still figuring things out and coming up with ways to put this machine to work. Please let me know if you have any questions. 

-Peter

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*There are printers that have dual extruders and the idea is you print your part in ABS and support any overhanging geometry with HIPS (these are printed at the same time). Then you put your part in a vat of solvent and dissolve away the styrene leaving just your ABS print. 

Edited by Photon
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Nice to see an explanation of your work with the FDM printer. Great results you get with it.

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