The 3D Printing Process

This Instructable is intended to give an overview of the 3D printing process, using a holder for toothbrush heads that I designed and printed as an example. The process is a little bit complex these days (it should get simpler in the future), but this Instructable should give you a good overview of how it works.

The first step, even before you design the object, is to measure everything. I use a measuring device called a micrometer caliper, the metal tool shown in the photo. You can get an inexpensive one from Harbor Freight for $15-$20, or spend hundreds of dollars for a high-accuracy one. I got mine a decade ago for about $30. It makes measurements simple that would be almost impossible with a normal ruler, so if you are designing, I recommend you get one.

These days, everything in 3D printing is geared toward metric, in millimeters. A millimeter is roughly 3/64 of an inch. Once you get used to using millimeters, you'll find it's much more convenient than counting fractions of an inch. My advice: just go with it.

Once you've made your measurements, you need to create a 3D model of the object. In the future, I expect manufacturers will provide 3D models of accessories on their website, but we are not there yet. Today, you need to design your own.

I used a commercial program from Alibre to create the model, but there are a number of free programs. The one from Autodesk, called 123D, has a rich feature set. Blender is open-source, and some like it, but it was really designed for creating objects to be used in 3D animation. There is even a simple modeling program that runs in your browser called 3D Tin. None of the ones I've used is as intuitive to use as I think it should be, but they are getting better.

The Alibre modeling program has some nice machinist features, like being able to extrude a shape and put rounded corners (fillets) on any edge, even a curved one.

Once you have created your 3D model, export it to a file in the standard STL format.

The 3D printer is not smart enough to print an object directly from the model, despite what you see people doing in TV shows. It needs a "choreography" that specifies each movement, and when to start and stop pumping out molten plastic, and at what rate to do so. You use a separate program to generate the tool path from the model, which is usually specified in a standard language for CNC machine tools called GCode.

I used Makerware, a free program from Makerbot that is only intended to create tool paths for Makerbot 3D printers. If you are using another brand of printer, you can use the open-source program ReplicatorG. It allows you to do things like moving the part so it is not floating up in the air (which will have a guaranteed failed build) and centering it on the build platform, or scaling it to make it larger or smaller. The output of this program is another file.

Once you have the GCode output file, you need to get it into the printer. Some people have a USB cable going directly from a computer into their printer, but I use an SD memory card to transfer the tool path to the printer. The Makerbot Replicator 2X I use has a small LCD display and buttons that allow me to choose various options, and does not need to have a computer connected.

If you do 3D printing for any length of time, you'll make a few, or even more than a few of these. The holder I was printing came unstuck from the building platform during the build, and as a result was carried around by the extruder head as a rat's nest of plastic strands was output.

After this happened, I looked on the Internet to remind me of what I could do. There were two suggestions. First I increased the temperature of the heated build platform from 110 degrees to 120 degrees, and next I was reminded never to open the door during a build. Cold air currents can cause the object to separate.

I print with ABS plastic. ABS is more error-prone during printing, but once the object is printed, it is more durable and less temperature sensitive than the other material often used in 3D printing, PLA.

You will likely go through several prototypes before you end up with a final design. My final design was the third one I printed, and is the one on the right in the photo. I originally made the pins too short, and the toothbrush heads were not stable on the holder.

Caution: when you get the final version, and actually put it to use, you will be inordinately proud of it. Don't worry; there's nothing wrong with you. It happens to all of us.