Lets start with an explanation of what a goniometer actually is. I'm sure that many of you are familiar with pan and tilt mounts, the kind used with cameras and telescopes, among other things. Well a goniometer is a similar device except that instead of a clamp that you open, swing to the approximate position then lock, a goniometer uses a lead screw or a drive to bring you to a precise angle.
Goniometers come in 1, 2,or 3 axis designs, I chose 2 axis: pan and tilt, I never felt roll was a big advantage though it would be easy to repeat the middle section of my design, rotate it 90 degrees and there you have roll, your 3rd axis.
Step 1: The Design
I created the solid model in Fusion 360. I have used several CAD software packages in the past but this one was new to me.
As I said previously I had decided on a 2 axis design.
Both axis are controlled using a lead screw dedicated to that axis.
The rotation runs the lead screw around a full 360 degree spur gear, this will allow the top carriage to rotate on continuous circles without limit.
The tilt section pivots around an axle and a half gear this won't quite allow for a full 180 rotation but it will be close.
The lead screw was created using the 'Add Thread' tool, this was extended only part was as the lead screw remains laterally in place while rotating, so only a small section of the thread is in contact with the gear.
The for the gear a cylindrical component was made and then placed close to the threads on the leas screw, the combine tools allowed me to cut away a perfect negative of the thread. The thread at the center was kept and the others filled back in. I then selected all features of this new gear tooth and used the pattern tool to form a full spur gear.
I used this tutorial from Youtube to learn this technique.
I have made some small 3D prints in the past but never with moving parts. I allowed .2mm around all moving parts to prevent binding. I also didn't want to use any glue so I designed little dovetail joints to slide and hold parts together. There may be a tool in Fusion to do this but as I said I'm not that familiar with it.
I also included a threaded hole (again using the add thread tool) in the center of the top carrier, this will allow me to mount an instrument (for me this will be my SLR).
In retrospect, I should have added the same at the bottom to allow securing of the device to a table top or tripod. I will have to drill and bolt on a mount for this.
I have included the stl files for the components.
Step 2: 3D Printing
I don't actually own a 3D printer but a generous friend loaded me his UP2! 3D.
I would really like to win one in the 3D printing contest so if you like this please vote!
The UP2! uses ABS as the print media, this is perfect for my use as it is very tough, a requirement with faces that wear against each other such as pivots and the faces of the lead screw and gear.
I wanted the finished product to be fairly solid so I used the most dense 45 degree infill.
Also as there are threads on the lead screw (worm gear) and the teeth on the spur gear I opted for the finest .15mm layer thickness.
Due to the size of my print versus the printing envelope of the UP2!, I required 3 printing sessions to complete the entire job, all in it took just over 24 hours and consumed just under 200g of print material.
I have included an image of one of my component placements to demonstrate the importance and sometimes unusual placements and orientations that give the best print time/material use/number of prints balance.
Nearly all 3D prints require the printer to add support material, this will hold up an overhanging parts later in the print, this is usually very sparsely laid out and does not use up a whole lot of material but it does take time to lay down. Sometimes this is a fair trade for reducing the number of print jobs required to finish a project. In my image, the base component is on edge, this increased the number of layers in this component from 105 to 513 but the print time went down by nearly 1 hour due to the smaller printing profile and without laying out this way I would have had to make a 4th print run.
Play with orientations, positions and combinations of components, use the print preview to compare the time and quantity of print material to be used, you may be surprised by the result.
Step 3: Cleaning Up
When the components were printed I found that I had made an error in placing each part too close to the bed, this left all parts printed directly onto the raft with no support material, this made the clean up difficult. You will see in the next set that I actually damaged (delaminated) part of the top section while removing the raft.
Before assembly, I did some small touch up jobs, mainly on the pivot points, worm and spur gears. For this I used a set of needle files and rubbed lightly. I did not want any burrs left over from the support material causing a bind or a jittery movement, after all, this is designed to allow precision movement so it needs to be as smooth as possible.
The dovetails were also a little too snug a fit so I had to rub them down to fit tightly but not break the support.
Step 4: Assembly
The sequence of images attached here walks through the assembly of the unit.
The lead screw was inserted into the slots in the base and secured with the retainers.
The center carrier was then added (this needed a bolt from the bottom to stop it lifting when turning the lead screw in the end.
The tilt lead screw was added, then the top table placed on and retained with the top retainers.
You can see the damage to the top table in the last 2 images.
Step 5: Mount, Swivel and Tilt
I mounted my SLR on the top table using a small piece of M6 threaded bar.
I was then able to slowly rotate and tilt the lens to the exact angle I required.
Step 6: Final Thoughts
This is the first 3D print I have done in a long time and the very fiest with this type of printer (older ones I used laid down PLA build material and wax as a support, support material was then moved by heating the model in an oven)
I place all parts too close to the perf base, this meant a longer, more difficult and ultimately damaging clean up.
I did not give enough thought to the retention of the center section when rotating.
I feel I should have used different colored ABS for each component to make them stand out from each other a little better.