My First 3D Design/Print Projects for Ham Radio
A few weeks ago I attended our annual Smart 25 a symposium here on the east coast of Canada for VE1, VE9 & VY2 ops. Lots of great topics and presenters including a session by Bruce VE9QR on using 3D printers for ham radio projects. Bruce’s presentation had multiple examples of solving problems with custom design and printing of parts. I’ve had a printer for over a year, printed a few things from STL file downloads, but have never designed any parts. I decided I better rectify that. As an aside, don’t introduce friends and family to the 3D file search function at printables.com or instructables.com unless you’re prepared to print parts for them! I’ve printed more things for my wife than myself the first year and still regularly get requests.
Printer Settings
I had a couple of design/print ideas for pieces that were meant for outdoors. Most of my print experience was with PLA filament which is not considered suitable for outdoor (not UV resistant) or high temperatures (it can start to soften and warp at temperatures around 50-60°C). There are several suitable alternatives, but PETG filament material is the most practical for me. Unfortunately, my few attempts at PETG printing resulted in a mess of strings and/or bed adhesion issues. My Ender 3 S1 Pro printer is on the “cheap and cheerful” end of the quality/price printer market feature set choices. Lots of features and “hackability”, but good prints out of the box is not its strong suit. However, with the help of some Cura slicer test print files for evaluating build temps, bed temps and retraction settings, I was able to find settings that mostly worked. Still see some very light strings which clean up easily.
Design Software
Bruce had suggested a couple of “free for personal use” 3D design program options: TinkerCAD for ease of use and Onshape for 3D feature set. However, despite being warned that it could be buggy and had a steep learning curve, I spent some time with the open source FreeCAD CAD program and have done all my designs with it so far. CAD (Computer Assisted Design) software has come a long way since my 2D CAD experience 30 years ago. “Constraints” and “parametric modelling” are new concepts to me. I estimate that I invested 10-20 hours of a loop of checking out tutorials, trying something, getting stuck, googling my issue; before I could design a simple part efficiently.
But, with that out of the way I was ready for my first design/print projects.
Project 1: J-pole Antenna to Top Rail Mast Adapter
A few years ago I mounted a 144/440 Ed Fong J-Pole on top of two 3.3m lengths of Home Depot fence top rail. I used two hose clamps to attach the 20mm PVC pipe (OD 27 mm) of the antenna to the swaged end of the top rail (OD 28 mm). This was never very satisfactory as the antenna would never stay vertical mostly because the end cap on the antenna added another 5 mm. What I needed was a spacer between the rail and antenna. In FreeCAD this was a three step process:
Step 1: Draw a Suitable 2D Profile
Using the FreeCAD “Sketcher” tools to create a closed 2D shape. 
Step 2: Extrude the 2D Profile Into a 3D Shape
FreeCAD call this a “Pad” but this operation extends the 2D profile a configurable “height”. In my case this was 45 mm.
Step 3: Smooth the Edges
This is optional but easy to do in FreeCAD. You have a choice of “chamfer” (convert 90° corners to two 45°) or “fillet” using a configurable radius. I decided to go with a 1.5 mm fillet.
Printing and Installation
In FreeCAD I exported the file in the 3mf format suitable for “slicing” using my modified Cura slicer configuration. I now had a file ready for printing and use.
It fits! 
..and the antenna stays straight. 
Project 2: Mounting Pieces for an Antenna Mast based on Army Surplus Tent Poles
A local store has been clearing out army surplus tent poles. They are fiberglass, about 40 mm in diameter in 1200 mm sections and look like they might make a good 6-7m antenna support. I thought I’d like to mount one attached to a wood walkway/steps for testing. This would require:
- A base mount to hold the bottom section and attach it to a 90mm square post.
- Another mount further up the post to support the mast.
- A mount to support an antenna at the top of the mast.
- A guy ring if guy ropes are required.
I designed and printed these parts including one designed to clamp around the support post 
and successfully used them to install a temporary 7m mast. A few pictures below but no guy ring/guys installed yet. Note that a couple of the pieces were an iteration of design idea, create drawing, print, and then discover something I had overlooked in design. Having a printer gives you the ability to do this rapidly (albeit with a 4 hour print time for some of my parts).
So far I’m happy with acquiring the skill and plan to do more design/print solutions soon.