Saturday, March 11, 2017

5 Easy Steps to Painting Your 3D Printed Model

By Tom Jeffrey

16935791_1217084228408902_1060952381_o.jpg 3D Printing opens up a whole new world of potential for scale modelers.  No longer do we have to wait around for some company to create a model of a vehicle for us to buy.  We can dream, design, and print our very own, bringing a whole new meaning to Revell of Germany’s slogan, “I Made That!”
For this project, I will be using a model of an Armored Personnel Carrier that I designed using 123D Design and inspiration from the Fallout game Series.  

The list of required tools may look to be quite extensive, but in reality, is quite simple.  If you are interested in modeling, a collection of paints, brushes, and glues can be gathered over time as you need them.  When used sparingly (as you will learn is a virtue in modeling), they can last for many projects.  

  • Your choice of hobby knives
  • Your choice of small-detail paint brushes.  These do not have to be fancy, just small!
  • Paint thinner.  This can help with thinning the paint if you so choose, for added effect (more on this later), or simply cleaning brushes.  A good multi-use supply.  
  • Your choice of model paints.  There are many brands, from the commonly found Testors to brands like Tamiya and Humbrol.  Generally speaking, cheaper paint has a shorter shelf life, and will produce less satisfactory results.  But remember, a little goes a long way!
  • A toothpick to stir those paints.  Shaking the paint is okay, but can cause issues like drying the cap shut and degrading the paint.  
  • A tissue or other painting rag.  You can wipe up excess paint, wipe off brushes, etc. A generally good item
  • Spray on primer
  • Super Glue or plastic modeling glue.  I find that super glue dries much faster and can be sanded just as easily as traditional model glue.  It is all up to personal preference.  
  • Masking tape
  • Sand Paper
  • Modeling clay.  Used to patch up mistakes in the print
  • Trash Bags. (Not Pictured) This is used for covering up surfaces that you do not want to get paint.
  • Model Stand.This is used to suspend your model in the air and make it easier to spray paint.  Optional, depending on the project.  
  • Proper Work Environment. (Definitely not pictured!)  Wherever you paint needs to be well ventilated.  This is mandatory.  These materials are not the non-toxic craft paints we all grew up with.  If breathed in in large volumes or daresay ingested, serious harm can be done.  Modeling is a fine hobby, but not without it’s risks.  However, if we take the proper precautions, there is nothing to worry about!

Step 1:Initial Printing and Setup

The first essential part of finishing your plastic model is to make sure that it is worth finishing to begin with.  Proper precautions need to be taken to ensure that the print is the right size for your display.  If it is too big or small, it will look awkward, and in either event, valuable material will have been wasted.  
Print in as fine detail as possible, to maximize the appearance of small pieces.  Also, make the judgment for what percentage infill you want for your model.  If printing say, a helicopter, it may be wise to increase the infill so as to increase the strength of thinner pieces that may come under stress later on.  
In summary, it is always worth it to take the extra time to make sure that what you are printing is actually what you want.  That is the key with model making: Take your time.  You will be surprised with the results you can get!

Step 2 : Post-Print Assessment of the Model

Using the blade of your choice (my preference is a thin, well sharpened blade with a medium length handle), scrape away the structural supports and “flash” on the model that can’t be gently broken off with your fingers.  Smaller pieces can even be slowly filed down, even with a regular nail file.  


This is also the time to repair any imperfections in the print with the modeler's clay.  This synthetic clay will not dry out, crack, and shrink over time, maintaining your desired appearance indefinitely.   Within my experience, if you only expect to handle your model lightly, and the patches are small enough, nothing more needs to be done to the clay.  It can be sanded, painted, and sanded again, and hold up quite well.  An optional step is to paint over the clay several layers of white glue, and then sand it all flush.

Step 3: Sanding

This is a relatively straightforward step.  Even if the print was set to fine detail, there are likely to be small lines that can be seen all over.  Lightly sand away at the plastic, being sure not to erase any small detail.  Sand as you see fit.
This is a far more simple alternative to the popular Acetone Vapor Bath, which is both considerably more effective and dangerous.  I will cover how to best use this method on ABS plastic in a future post.  

Step 4: Priming

In order to prime your model, set up your painting station either outside, or in a well ventilated room.  My own personal preference is inside the garage, with the door open.  Wash your model with hot soapy water to remove dust and oils.  
Set up your trash bags around wherever you expect to paint.  A floor covering and one wall covering is sufficient.  Place your model on your stand.  For this model, I used a miniscule amount of modeling clay to attach the model to the top of the stick.  This allows for maximum coverage.  I can simply turn the stand around to get at different sides of the model.
Specific to this model, I will be putting a communications antenna onto the back before I paint.  This is because the small hole that the wire goes into is likely to get filled with paint.  
Tips for painting: Go in long, thin coats.  Start spraying off to the side of the model, and quickly run the spray along the model.  In order to get the best finish, with no drips, try very thin layers.  In my experience, two layers creates a satisfactory base layer that does not eliminate detail.  
Optional: If you are planning on “weathering” your model, which means to put artificial wear and tear on the finish, try substituting your last layer of primer with a silver coat.  Later, you can scrape off the finish paint in select areas to get that worn paint look.  

Step 5: Finish Painting Your Model

This is by far my favorite part of the process, besides the initial design process itself!  This is where your creativity can really shine.  
I recommend by first setting up your painting station.  Again, set up in a well ventilated area that you do not mind getting dirty and or irreparably harmed (in this case, painted).  Do not paint on hardwood surfaces!  
Second, sand away any excess buildups of your priming coat.  This can be done after a lengthy drying period.  Within my experience, I like to let the model sit overnight.  
For this model, I will do a base coat of olive drab green, but will also touch up with black, mud, and rust, along with scraping away paint to reveal the silver underneath.  
I recommend using as little paint as possible.  Again, go for thin coats.  You can always put more paint on, but it can be hard to take paint off in a uniform fashion.  Detail on these models is very small, and it can be easy to cover it up with too much paint.
Finish off your model with a quick spray of clear coat and you’re good to go!
Optional: Dilute your paints using a small amount of paint thinner.  This can be used to “wash” over the base coat.  This can be used to effectively make your piece look rusty or dirty.  In reality, the possibilities are endless.  


One coat of olive green paint


Two coats of olive green paint


Black details


Use a hobby knife to scrape off paint, revealing the silver coat beneath.  Try along edges or raised portions, for example.  Go for small details as opposed to large scrapes, as I accidentally did here.  


Mix light brown and red to make a spectrum of rust colors.  Dot this where you see fit, if you desire a worn look.  

The last step is to let your model dry well, (24+ hours), and then give it a sealing clear coat to protect the paint.  

Supplemental links for further reading and tips:

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