Introduction: 3D Printed PCB Substitute and Printing Skill Building
There are many ready made prototyping circuit boards. They come in various sizes and are relatively cheap. Check out ebay. The first photo shows an example board. Short of designing a board and either etching it myself or sending it out for fabrication, these boards are good for simple circuit designs. If there are a lot of components in the design, using these boards and "hard wiring" gets to be tedious.
Recently, I needed to add a relay to my CNC machine. I wanted to add the relay as a "module" so I could add or remove it without major disruption to CNC electronics.
The second photo shows the components to be used which are a relay, two screw connectors, and a diode. The problem I had is that the relay pinout does not match the "standard" prototyping board pad/hole spacing. A solution would be to "dead-bug" the relay on the board, I.e., mount it upside down. However, I wanted a little cleaner fix so I decided to design and fabricate a board using my 3D printer. As will be seen, no metal traces are used.
The last photo shows the completed board.
Step 1: What You Need
Admittedly, if you don't already have 3D printing capability, you probably wouldn't go out and buy it for this board design. But, 3D printing technology is rapidly becoming available to many more. In addition to actually solving a problem, designing and fabricating this simple board builds skills. What I have and used:
- TAZ 5 3D printer
- Simplify3D slicer software
- Fusion 360 design software
- HIPS 3D filament
- Vernier Calipers or a metric ruler
- Blu Tack adhesive (or any other adhesive or method to temporarily hold components)
- Felt-Tip Marker
Fusion 360 is an absolutely wonderful software application, "free" to hobbyists. It does have a steep learning curve, but, there are plenty of tutorials and answers to user questions online. Personally, I found that the best way to learn it was to design and print as much as possible.
Simplify3D is also a great program. It's not free, but works very well. There are free slicers out there, but, I've found that you too often get what you pay for. I'd rather pay for good software than spend a lot of time chasing bugs.
HIPS 3D filament is very similar to ABS so use either or chose virtually any filament you like to work with. I mostly print in ABS or HIPS.
Step 2: How to Design the Board
You can either design as you go in Fusion 360 or start with a "paper" design and move it into Fusion. A pair of venier calipers is very helpful and they are cheap as well. But, you can get by with just a metric ruler from the "Dollar" store. Generally, and like a lot of things, designing and fabrication are somewhat of a "trial and error" operation. Seldom do designs and fabs come out "perfectly" the first time. But, you get better over time!
Fusion 360 provides an easy way to modify an existing design without completely starting over. This project was small enough so that the 3D print time and filament used was minimal. I iterated the design several times printing at least 6 versions before finalizing it.
Types of design/fabrication errors I encountered:
- The measurements I made and entered into the Fusion were "close" but needed tweaking.
- I put a hole in the wrong place and the relay would not fit. Simple redesign to fix my error.
- The 3D printer didn't print the small holes, 1mm, at correct size. They were too small for the parts to be mounted. Simple redesign to use larger holes.
- I decided to "fillet" the corners to reduce board size and maybe make it look "nicer". It printed okay, but when I went back to make additional changes, Fusion didn't like how I had reference hole locations. The lessons learned were to not add the fillets until after the design is firm as well as to better reference features, like holes, properly. In the end, I just left the fillets out.
- Looking at the board wiring schematic, I decided to rotate the relay mounting 180 degrees to facilitate wiring. Again, a simple design change.
- The 2 mm thickness I chose for the printed board was too thick for the short component leads. I tried printing a 1 mm thick version but it seemed too flexible, possibly breaking too easily. I settled on 1.5 mm.
The photo shows the final board after printing.
Step 3: Assembling the Board
The first photo again shows the components installed on the top side of the board. Blu Tack, the second photo, adhesive was used to secure components until they were wired on the back. The third photo shows the underside of the finished board. Two large holes are used to mount the board in my CNC.
The board will "melt" if you sit on a pin too long so you may want to "pre-tin" parts and wires before trying to solder on the board. And then, when you solder, "get in and get out" as quickly as you can. I also used Blu Tack to hold down wires and parts during soldering.
As I soldered the parts on the board, I used a felt-tip marker to identify signals on the top side.
- For "simple" circuit designs, a 3D printed "board" can substitute for lack of a PCB or when parts won't fit on standard "off-the-shelf" prototyping boards.
- 3D design and fabrication is quick and builds skills needed to do successful 3D printing.
- Even a simple project like this helps understand 3D printer limitations. My TAZ 5 printer is a very good printer, but, I know from past experience that it wants to print holes undersize. Maybe I could adjust some printer parameter, but, mostly it's not a problem and I just live with it.
- The more I use my 3D printer, the more applications I find for it.