3D Model To 3D Part

Five months ago I started spending time building projects in Google SketchUp. I Also enjoy model railroading and they tend to compete with one another for my time off. Building in a virtual digital world and building in a scaled-down plastic world. Now here we are crossing over into the gateway that connects to two together.

3D Printing

The first thing you learn about 3D printing is that the bridge that makes them connect is full of bumps, and the pathway has not been cleared to be a super highway yet… Here is the short of it: so you want to take a structure you have built in SketchUp, and have it on your model train layout.

First, add an extension in SketchUp to be able to export it in the correct file format.

Sorry, forgot to tell you about “Tight as a Bathtub.” What!? Is the part sealed? To create a good part… Wait a minute! Part? You mean I can’t print the whole structure all at one time?

As you see it’s a bit more complex than I first thought. Let’s go back to when you first open a model kit, and it contains all the halves of boxes or flat single sides of walls. You have to break the object down just like they did. You need to plan and understand the assembly process. You might say reverse engineer it.

Planning that you are going to 3D print an object as you draw it, makes a big difference in the speed of preparing the parts. I would call them artifacts or lines and fills left behind in the drawing process that is hidden, but to the printer, it sees them and fails to build the part.

sketchboxSay a rectangle is drawn and pulled up to make a box. Now Group that object and look at the Entity Info pallet. It will say Solid Group. If you look inside you would find no extra fills or lines. This would export and print perfectly. Now, what is going to happen to all that void space inside the part? Good question. Let’s learn more first.

The only thing we need to define for this example is the outside edge of the skin. The number of facets can be made of thousands of points and faces. As long as the whole object is Solid Group you are good to export. I will go deeper in the preparation of objects in a full tutorial later.

The file export extension only gets you half way there to make this block on a printer. The file that it makes is called an STL file or Stereolithography file. A standard format developed in the 80’s to define an object in 3D space. Learn more on WIKI here.
What we have defined from SketchUp is a solid box. It does not have a wall thickness or the information of what to do with all that interior space. What the printer is looking for is a path or the x,y and z location to where to put the plastic.

Screenshot from inside of Cura

This is where the slicing program comes in and saves the day. There are paid versions and free ones out there. I will break the choices down another day. I am using a free version called Cura. You do not draw in this program. You lay out your parts on a virtual print area called the bed. It is very quick to learn how to move, rotate and add a specification to the part. There is a cool scrollbar that you move up and down to show each layer that will be printed.

Now that we know the speed of the build plastic we can calculate the build time. Breath, it going to be OK. Now calmly read the time… 3 HOUR, 45 MIN. What!! For that little part.

Well, it used to take longer, and we are at the cutting edge of printers that are as much as 100 times faster. Imagine a 3D printer that pulls the part out of liquid plastic into a solid part. This technology was demonstrated on stage live on TED Talk.

After adjusting the details of the infill and part quality, you make your next file format. This one is called G-code, sometimes stored on a memory card and inserted into the printer’s control box or uploaded with a USB cable. G-Code is the standard format for 3D printers to read and build parts from. It is NOT interchangeable between printers because the slicing program takes into account the specifications for the plastic you are using and the “tune-in” setting for the way your printer heats and performs.

Is it worth all of the trouble? Some Do It Yourself experimenters have spent months just tuning their machines.

Then you see the magic moment when 100’s of parts move in harmony, spinning and humming, heating and rolling a thin string of thread to knit together something that before never existed. Yes, I believe it is worth it.

Join me as I try to design, build and test my own 3D printer in the coming months.



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