Sunday, May 15, 2016

3D Printing in Copper, Model Railroad details

This is the first of several posts that will be about 3D printing using Copper infused PLA.  This is PLA (Polylactic Acid) plastic filament with fine copper infused in the plastic, so it prints in copper.  Because it is real copper, it can be chemically weathered to add patina.  

First, I generally print using ABS (Acrylonitrile Butadiene Styrene).  ABS melts at a higher temperature (240 degrees celsius and more) than PLA and it requires a heated bed on the printer to keep the print from warping.  ABS is stronger, more flexible, and will not degrade over time.  It is also solvent weldable to Acrylic, and polystyrene, so it is great for modeling.  (for more on ABS versus PLA).  ABS prints clean, with very little stringing, more on that later.

PLA melts a lot lower temperature, 180-200 degrees celsius.  If you leave an PLA print in your car in the summer, it can sage, warp and get sticky.  PLA is sticky, and tend to string between items.  It, therefore, take more clean up than ABS.  It is brittle, when compared to ABS, and it is biodegradable, even compostable.  According to most sources, it will degrade over time if left outside.  PLA is cheaper.

I bought my roll of Copper infused PLA from Afinia, since I have two of their printers.  FYI, that is wood infused PLA next to the copper.  Yes, I can print in wood too, but that will be a later post.

One of the first items I printed in copper is a roofing ridge cap.  

I test fit the cap on the roof, before I weathered it.

One of the cool things about copper is that it can be chemically weather to give it a natural patina.  That will probably not get covered much until the second post, as it was quite an experiment. 

Here is a large tub I printed, this would be about the size of a bath tub in HO scale.

To get the copper to oxidize, you fume it in an atmosphere of ammonia and salt.  I threw some salt in a container with a tight let, put in a little ammonia, then used some 3D printed angles to hold the ridge up above the liquid.  I put the lid on and waited a day.

It came out with a nice patina to it. 

It is a fairly new looking roof, so not a lot of patina was required.  If you leave it in the fuming chamber longer, it will oxidize more, and, therefore, have more patina.  MUCH more on that in the next post.
 I also printed a small section of copper roofing,  

In my opinion, PLA does not hold as sharpe of lines at the ABS, so the details are not as clear.  In this case, the roof ridges are just not as clean as with ABS, but then, they don't make ABS infused copper!

Remember the tub in the picture earlier, it had one little string of plastic coming off of it, formed when the print was done and the printer head moved away.  Check out the print above.  I printed the tub with two chimney caps, and note all the stringing and globs of plastic between the models.

These tubs are only about 1/4" in diameter, and you can see all the clean up needed.

They can be cleaned up, but it take a little work.  Much easier than cleaning up a metal casting, since it is plastic.   Here is whole bunch of items I did some tests on.  I wanted to see how long items needed to fume in the ammonia and salt air to get a given patina.  More on that in my next post.  

I also made some skylight frames using the copper, for more on that, click on this link, skylights-copper-3d-printed-frame.

I am also looking at getting a rock tumbler to polish the copper.  If I can make it look old, it would also be nice to make it look new.

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