I read an article about different 3D formats and it occurred to me, can I take a simple project I created for learning KiCAD and print the PCB on a 3D printer. This exercise was interesting enough that I thought I’d share. Hopefully this will provide a clear enough roadmap for anyone else trying to figure these things out.
Step 1: Schematic
This is a simple schematic for a 50% duty cycle astable multivibrator. I wanted the simplest circuit for exploring SPICE modeling in KiCAD. Q1 represents SPICE parametric device modeling, and U1 for more complex SPICE subcircuit modeling of the 555 timer.
Step 2: PCB
I initially did this layout by hand which is very easy for a circuit this size. But I ripped it up to try FreeRouting, an auto-router for KiCAD. The results were marginal, but this circuit is simple enough that I was able to clean it up and complete it by hand. I guess it was impressive that the auto-router worked at all. I was looking for an auto-router with a performance level similar to Eagle’s auto-router. FreeRouting isn’t there yet, but promising enough to deserve support. I was hoping to auto-route a single sided board for a milled PCB.
Step 3: Export PCB to VRML
I wanted to use STEP for this format step. My 3D printer won’t read STEP files, it needs the much simpler STL format. FreeCAD will import both STEP and older VRML formatted files. Windows 10 “Print 3D” can read VRML, but not STEP. For now VRML is more useful, but STEP is the future. I also exported a STEP file for archival and testing import to FreeCAD. Notice the plated through holes and topside copper information contained in the VRML file.
Step 4: Import 3D VRML model to FreeCAD
This step looked and behaved the same using either STEP or VRML source files. Both were missing top side copper image and labeling. Like I said, what made the decision for me was Windows 10 Print 3D ability to render VRML. This step is necessary to convert either VRML or STEP intermediate files to STL for 3D printing.
Step 5: FreeCAD export 3D model to STL
Notice we’re now missing color information. STL is a “geometry only” 3D format. it isn’t capable of providing color. That’s okay because most of today’s 3D printers also don’t print in color. If you need color, use STEP or the older VRML format.
Step 6: Print STL on 3D printer
The smaller print is a 1:1 scale. The problem with this size is the printer can’t print really fine detail, like vertical 1-pin test points. Some of the parts broke off just with gentle handling (notice the TO-220 transistor is missing). This print took 33 minutes.
So I tried printing at 300% size. This might be too big and next time I’ll try 200% scale. This print took over 6 hours.