SO I’ve been working with AutoDesk’s Fusion360 for a while now, and have found it to be an exceptional tool for diving into CAD. If you’ve considered CAD before, but have been scared off by the learning curve, I recommend checking it out. One of the important functions of a truly parametric CAD program is the need to reference objects to other objects, and to reference measurements to variables or other object measurements. I knew Fusion360 could handle parametric work, but hadn’t been able to figure out a solution to my particular problem, so, here’s a video on how I did it. Not sure if this is an accepted method conventionally, but it worked for me!
The problem I had was how to set up a reflection line, which was dependent on 2 inputs, the angle of an input source, and the reflection angle of a mirrored surface. I wanted to be able to drive these 2 input values, and have either of them affect the resulting reflection line. Here’s how it worked out.
SO I had a project where I needed a specific size of beamsplitter and I needed it quickly. Unfortunately, the type I needed wasn’t available from the usual sources, at least, not without a few days of lead time. What to do? It turns out, crazier people than me have been using CNC machines to cut glass!
So, I made a jig from acrylic, and cooked up a hold down method, and voila, after a few attempts and figuring out how to hold the part, I was able to cut both sides of 2 of these small beamsplitters successfully! Unlike the linked example, I simply used water as a coolant, and submerged the workpiece in a recessed channel in order to provide cooling during the cut. I used a dremel diamond engraving bit, likely not the best choice, but it’s what I had avaailable. Feed speeds were @ 0.61 IPM with an RPM on the spindle @ 2600. Finish was a bit rough, but definitely useable! I figure the difference between my work and the example above is the end mill selection. Anwyay – If you ever find yourself in a similar pickle, and have access to a CNC, it might be worth a shot.
Last month a friend gave me two old pairs of field glasses. One set was US Navy issue, which has the old-school build quality of a tank, and produces a bright, sharp image. The second pair was cheap and damaged. I’ve considered what to do with it for a while, and finally decided to tear it apart, and use the optical elements inside for educational, research and entertainment purposes. To that end I needed an adjustable optical platform, and while I have plans to make an optical table, for now I wanted to make a simple stack. Here’s how I did it.
Base with two optical elements attached
The base – I had an old aluminum base plate used on Sutter’s “LS” lamp series. We sometimes discard these bases during installs, so I managed to save this base from the scrap heap. I also snagged one of the support rods. This gave me a post with which to mount optics.
Next I needed something to hold the optics in place. I considered using band clamps, or other methods, but settled on making custom-cut holes that could accept the elements. If you want to do a similar project, you could use drill bits, a scroll saw, or even files to shape out the holes. I was itching to use my DIY CNC machine for something useful, so I employed it to cut the holes for me. I made a set of square blanks, and drilled a single alignment hole in each square. By using this hole as a center, I was able to make each different lens holder have a coaxial alignment, so that the lenses would stack up correctly.
Finished hole cut – note the alignment hole in the upper left side.
I’ve cut MDF (always wear a respirator when cutting MDF!) before, but have never had a good end mill for the job, so I finally made one by cutting one of my routing bits in half and sharpening the endpoints. The new bit chewed through the MDF with ease. To be extra careful I stepped my cuts at 0.050″ per route at a speed of 2ipm. This is a gentle/slow setup, but I wanted to make sure the parts came out well, and I didn’t want to push the machine for no reason. Finally, because I was cutting down nearly through the material, I set things up to leave a 0.010″ thick layer at the base of each cut. This way when the operation was done, I could simply push out the disk, and not risk cutting up my table on the machine. This process worked really well. Below is a video showing how easy it is to pop out the last layer.
With the holes all cut, I enlarged the alignment holes in each plate so that the plates would slip over the vertical rod I had. They fit snugly and allowed me to adjust the focus of each element as needed.
After spending a few minutes playing with the system I was able to set up optic trains providing magnification ranges from 10x to about 40x. The higher mag configurations didn’t look great, but here are some images I acquired using my iphone through the setup.
example configuration of lens elements
This was a fun project that only took about two hours to complete. Once I settle on an optimal configuration for these elements, I’ll post on it!
