Now that we have our first nixie tube clock built, it was time to step it up a little and make something a little more challenging. Nixie tubes, using a glow discharge instead of LCD or LED displays, have an old world charm to them, yet can be made to operate similar to a modern display. The plan here was to pair these tubes with a nice wooden clock case, made using the CNC machine. The end result is something that has a warm wooden feel to it, with a colorful numeric display which is both attractive and, when used with a GPS for accurate time setting, highly functional as well.
I purchased a Nixie Tube Clock Kit (Clock QTC with IN-8-2 Tubes) from PV Electronics. I also purchased a 12 volt power supply and their optional micro GPS receiver so I could set the clock with something more accurate than my cell phone. The kit arrived about a week later since it was shipped from the UK. The manual to construct the clock was available online, and was more than sufficient to allow me to solder the clock correctly the first time. You will need to rely on the silkscreen part numbers on the circuit board to understand where to place each component. I had one number that was difficult to read, but it was not too difficult to guess where the part went on the board.
I did have problems installing the male headers onto the main board, to which the tubes eventually plug into. The holes drilled in the board for these headers were drilled too small, and I really had to pound the headers to get them into the board. The manual indicates these holes were designed this way (yeah, right) to hold the headers in while soldering. It’s funny that none of the other header holes were drilled this small, and I had no trouble soldering everything else. However, after a few (real-time chat) exchanges with PV Electronics, they were very quick to help and noted that the holes should be larger on the next circuit board revision. I give them a lot of credit for helping and listening. I’d definitely buy from them again. Once the board was assembled, I tested the clock, which worked perfectly. Someone had done some nice programming with the microprocessor for this clock. The numeric display is very interesting to watch, with interesting scrolling and slot-machine style effects.
The first part of designing and making the wooden case was to select the CAD software that I would end up using with the CNC machine. I had previously tried Inventor Fusion for the Mac, but after spending two hours trying to position a hole in a simple three-dimensional object, I gave up. Eventually I stumbled across MoI 3D. This software is nothing short of phenomenal. Within an hour, and having never really learned a full CAD package, I had my entire clock design finished. I created a design based off of an art deco look, blending old school technology with a modern symmetrical style.
I spent some time tweaking the individual pieces in the design, and exported each component separately to MeshCAM to set the tool paths for the CNC software. MoI 3D is certainly worth every penny, and will be my default CAD software for this CNC machine going forward. It was a huge relief to find this software, since everything I had tried up until this point was either exceptionally expensive or impossible to learn. If you would like to download my MoI 3D clock case design, you can grab it here. I was not as impressed with MeshCAM, although it served its purpose. If I was to do this over again, I might consider something like Vetric’s Cut2d. Cut2d allows you to easily see how your piece will look once it has been cut.
After setting up the CNC machine, I thinned some stock wood to about 5 mm thickness, programmed the CNC machine, and let it run. I learned quite a bit during this process, and made quite a few mistakes. Online forums helped quite a bit, and answered most of my questions about how to set the machine up to cut correctly and how to eliminate problems before I started. There were times when cutting out multiple parts that my machine ran for an hour and twenty minutes. That’s fine with me, better the machine doing all the work than having to sand items by hand for hours on end! Eventually I learned to set my speeds correctly, and was able to machine parts in 5-15 minutes.
I was especially happy that the CNC machine took care of cutting all of the holes for the plugs, LEDs in the back, and tubes in the top. This was much more accurate than using a drill bit, and there was no chipping on the edges of the holes.
Along the way, I learned a few things about CNC machining that I wish I knew before I began to cut the wooden parts. For example, there are two ways to make filleted (rounded) edges on wood – parallel to the edge, or perpendicular to the edge. When using an endmill bit (think of a perfect cylinder flat on the end), cutting perpendicular to the edge gives a nicer corner. Parallel cutting leaves “topo” type steps on the corner. Also, endmill bits are not the best bits to use for making round corners. I should have used a rounded ball end bit. And finally, CNC machines are the reason there is so much dust on this planet. I alone am probably responsible for any dust you might find on your end table.
I think the best part about using a CNC machine for this project had to be the perfect hole drilling. After taking careful measurements and placing all of the holes correctly in the pieces using MoI 3D, the CNC machine made the holes without a second thought. It was much easier than using a drill press, and I didn’t have to worry about chipping the edges with a dull drill bit. Once I pulled the parts out of the CNC machine, they fit perfectly around all of the components.
After all of the wooden parts were cut out, and after many, many mistakes, I began to glue the wooden box together. The end pieces are removable, and I left the top cover over the tubes unglued. This will allow me to pull off the ends, lift up the top piece, and replace any nixie tubes that go bad over time. Thus, the “QTC” in the clock I ordered – “Quick Tube Change.” I finished the clock off with some Danish oil, one of my favorite ways of finishing natural wood to bring out the grain. I think the tube LEDs give the clock a nice glow on the white maple wood, don’t you?