Arcane Game Lore

Never split the party!

3D Modeling – Pirate Corvette Mini

At work we just got in a 3D scanner and I’ve been testing it out since Monday.  (It’s a NextEngine scanner if you’re interested).  I’ll probably post about 3D scanning (it’s not as easy as you’d like) in a future post after I have some more time with the scanner but that got me thinking a bit about 3D printing again and I figured I should post about some more of my models.  So this week I’m going to talk a little bit about creating and printing Pirate Corvette model I made.

Modelling the Corvette

This was actually one of the simplest models in the set.  The total OpenSCADcode for the entire model is only 37 line including comments, white space and closing braces.

The Fuselage

I started with the fuselage.  This was actually the hardest part of the print.  The bottom half is just a pair of truncated cones (made via the cylinder() command in OpenSCAD).  The top half is one of the stretched cylinders that I used in the Assault Scout mini.  The difference here is that while the Assault Scout started out as a flat cylinder and tapered to a point, the Corvette has a narrow tail, tapers out to a wider waist, and then tapering to the point at the nose.  Another difference is that while the original Assault Scout mini has a slightly angular feel to it, the Corvette was all curves so I wouldn’t be losing any of the original look.

Getting the fuselage right was actually a bit harder than I thought it would be.  I probably printed 3-4 different models before I felt that it looked right.  I had measured that maximum width but the original set to that value just seemed a bit fat.  I made adjusting that diameter simple by using a variable in the OpenSCAD code for the width of the lower cylinder at it’s top, the diameter of the sphere, and the size and offset for the box that cuts off the bottom half of the sphere.  Then I could just change a single value and rebuild the model and everything adjusted properly.  Here’s the entire code for the fuselage:

$waist=2.3;
cylinder(r1=1.4,r2=1.6,h=1.5);
translate([0,0,1.5]) cylinder(r1=1.6,r2=$waist,h=13.5);
translate([0,0,15]) scale([1,1,10/$waist]) difference(){
    sphere(r=$waist);
    translate([0,0,-$waist]) cube(2*$waist,center=true);
}

Adding the little flare-outs in the nose was easy enough.  I just created a bunch of cones and positioned them properly.  Unfortunately, I had to position them by hand.  While I might have been able to figure a mathematical relation for how far off-axis they needed to be based on their height and the value of the $waist variable, it was easier just to move them by hand when I changed the size of the waist.

The Wings

Next up were the wings.  To get the shape just right, I actually traced the ship onto a piece of graph paper and then used a ruler to measure out the positions of all the corners in the wing shape.  In OpenSCAD this was modeled using a polygon().  I created all the vertices, and then connected them to make a 2D shape.  I then extruded this shape to be the proper thickness for the wings.

Once the shape was made I rotated it into the correct physical position (2D shapes are drawn in the XY plane and I needed the wings in the XZ plane) and duplicated it on the other side of the ship.

The Engines

The final piece was to add the engines on the wings.  Again, the shape here is simple.  It’s just a cylinder that has had the top and bottom sliced off at a 45° angle and then a spherical cavity carved out.

In OpenSCAD you do that with the difference() command.  You start with the cylinder.  Then you add the shapes you want removed, in this case two boxes to slice of the ends and two spheres to carve out the cavities.

I then put the engines inside the for() loop that made the two wings so they were duplicated as well.  The final model looks like this:

Image of the corvette model as described in the text

Printing

The next step was to print it.  As there was only a small point of contact with the build plate on the printer at the back of the fuselage and the points of the wings, this model definitely needed to have a raft under it to hold it in place.  Additionally, I needed to print supports to go under the engines and wings.

That part of the print was not an issue.  The trouble was that this print suffered from the same fuselage printing problem as the Assault Scout.  When printing the upper part of the fuselage, the print time is so small that the plastic from the last layer printed doesn’t have a chance to cool before the next layer is placed on top of it.  This results in the print being “smeared” and not looking very good.  I solved this the same way as the Assault Scout; I printed 4 at a time which gave the prints enough time to cool and they ended up looking much better.

Here is the final test print next to the original miniature I was using as a model (click for full resolution):

Printed model next to the original metal miniature

You can see the individual layers on the edges of the wings in the printed version.  Plus there is a little bit of residue that I haven’t quite cleaned off.  As with the Assault Scout, the model is missing some of the fine detail that the metal miniature has simply because it would never show up in the print anyway.  My conic pieces on the fuselage are a little fatter and shorter than on the original as well, something I might tweak in the future.

Painting

Like with the Nightwind, I made the main part of this model a simple silver to represent the reflective anti-laser coating.  I then painted the engines and the little pods on the fuselage red.  Finally I filled in the hollows in the engines with black.  Beyond that I haven’t don’t much with these ones.  Here’s a pair of them painted:

A pair of the covette miniatures painted as described in the text

 

Lessons Learned

My 4 year old likes to take these ones and fly them around the house and at this point, I’m not sure if any of the four I painted are actually still on my table where they belong.   In the future I should print extras.

The model for this one wasn’t very hard and all of the techniques used in building it I had at least tried out in the earlier models.  So there wasn’t much new or to learn from the modeling process.

Looking closely at the painted model, however, reminds me that the white plastic we print in hides a multitude of sins.  Once I got the silver coat on all the little ridges and rough surfaces on the wings really stood out even though you don’t really notice them on the unpainted plastic.  On future models, I think I’m going to want to do some sanding of the surfaces to make them a little smoother.  Of course, these surfaces are really small and that may be a bit of a trick.

Any thoughts, comments, or ideas?  Feel free to share them below.

 


Categorised as: 3D Modeling/Printing



Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>