The lamp shades were a part of this project I agonized over. In the end it was a fun engineering challenge.
Challenge #1 Color
The first challenge was to figure out what color to make the shades. I printed out a few sample shades that I tested out with a simple rig on a breadboard that would run through a series of animations on a small NeoPixel stick from Adafruit. This allowed me to see how each of those sample shades would look as the colors on the strip changed.
First I tried Village Plastics and PolyLite White PLA — it was not bad but seemed to look like a warmer color (See photo below) which while not bad was not the look I wanted.
Next I tried PolyLite PLA Translucent Blue (the same as the the bridge superstructure) but I felt that color skewed everything blue. (Left side of image below)
Next up I tried nGen clear filament — which prints a lot slower than PLA but also is more resistant to heat — and I really liked the results. The colors were clearly transmitted through that material and could be seen from the sides. For me this lamp is not really used for downlighting, it’s more of a novelty to been seen from all angles so I thought this was the best solution.
NOTE: My friend and co-worker Chris also printed out test shades in PolyLite Translucent Red, Yellow and T-Glase Red — and much like my experiments seemed to skew the colors too much to look like whatever color the filament was.
I had the demo rig below on my desk for a few weeks and solicited feedback from friends and we all seemed to land on the clear nGen
Challenge #2 Glare and Drooping
In the original LED Bridge Lamp (Universal Segment) by my friend Janis Jakaitis (Opossums) I noticed in one of the photos the LED strip was sagging a bit (See below). This is a common problem as the adhesive on the back of these LED strips is not all that good or strong and doesn’t stick well to plastic. If you go with a more aggressive glue it makes it harder to repair/move/replace anything that fails in the future.
After working with my test rig I also found that these LEDs can cause glare and be rough on the eyes if you look directly at them so I figured some sort of diffuser would be a worthwhile addition.
I spent some time trying to come up with an elegant solution — maybe printing each shade vertically and creating a channel for the LED strips — but I felt that orientation would weaken the shades and likely result in rougher prints. Other ideas were too complex — such as screwing on diffusers etc.
In the end I came up with a solution I am happy with — I modified the light channels to be deep enough to enclose the LED light strips and created a dovetailed channel that would capture a flat printed thin diffusers. (See photo below)
3D Printing Tips
I printed these light channels WITHOUT any sorts of brim as the object is flat with a lot of surface area and didn’t require any real cleanup.
I printed my lamp shades with 20% infill.
You’ll want to make sure your printer is really dialed in and well calibrated. If you find the diffuser cover is too tight, I provided a ‘loose’ cover LightChannelDiffuserCoverLoose.stl which is the same diffuser cover but 2% narrower. I believe this is what I used as the basis of the covers included in the curved shade sections — so those already include a loose diffuser cover. If after printing you find yours are still too tight you can break up any of the diffuser sets and scale the diffuser cover another percent or two narrower.
When trying to slide the diffuser covers into the diffuser I found it was sometimes easier to slide in if I spread the diffuser a bit in my hands as I slid in the cover.
Make sure the diffuser cover is oriented the right way (the same way it was printed)– with the tapered side down before trying to insert it into the diffuser channel.
For the curved sections of bridge lamp there are two sections — an ‘A’ and a ‘B’ section each with a diffuser channel and a cover. All parts print with a letter in/on them. The ‘A’ in the cover should be oriented the same as the ‘A’ in the diffuser channel. The same logic applies to the B section. Section A and B are not identical mirror images, just like the original channels.
After removing the lamp shade prints from the printer I would assemble the lamp shade section (slide in the cover) and file the ends flat with a flat mill file. They didn’t need much filing but I wanted nice smooth mating surfaces. I would have an assembled super structure assembly in hand and could use that to test and make sure the ends were co-planer with the ends of the bridge superstructure section.
I would assemble the 3 blue superstructure sections using the nice glue up jig provided by Janis’ original model. I didn’t bother to modify the jig to fit the lamp shade diffusers — as my shades have a deeper channel. Instead I would take the assembled (and dried) superstructure, line the edges with a small bead of LocTite 401 CA glue and then slide in the shade (Above the glue lip and then slide it down into place to not disturb the glue and more than needed. This allowed me to squish/twist the superstructure if needed to really square up the now fully assembled section. You’ll want to take extra care to make sure the channels of one section really line up well with the next one.
For curved sections I’d glue the A and B sections to each other (make sure to file and test fit that A and B mate cleanly). With an assembled A and B section I’d then follow the process described in the paragraph above to glue it into a completed curved superstructure assembly.
In the image above you can see how the A and B sections are mated in a curved section of the completed bridge lamp.
My bridge lamp is broken up into 3 assembled sections — 90 degrees of the arc, 2 straight sections to support the billboard and another 90s degrees of arc. I built my lamp in a modular fashion so it would be easier to change if I have a different job or workspace in the future and don’t want to rebuild this lamp from scratch.
With a completed section of bridge (superstructure + lamp shade/diffuser) in hand I would test fit it with the next piece of the bridge. This meant testing to make sure the tabs locked well into each other — usually filing meant flattening any edges/corners that were rounded and likely squaring up the clips a bit to fit tightly. Squaring up the clips meant filing out a bit of the underside the tab which was triangular in profile to better mate with the square edge of the adjoining piece of superstructure.
With all the individual bridge sections completed I would glue each of the fitted sections of bridge to the other to add additional rigidity to the lamp. (If you don’t do this each of the sections can twist a bit which makes it even harder to fish the LED strip through the diffuser channels.)
The photo below shows one of the 90 degree assembled sections. In order to fish the LED strip through the channel I soldered a long piece of wire (longer than the assembled section) to one of the pads on the LED strip and then used electrical tape to further secure the wire to the LED strip and protect the pad — as they are really easy to pull off — and likely after this you’ll want to sacrifice/cut off that first LED. I then pushed the wire through the channel. Now for the dancing….
Getting the LED strip through the channels was a time consuming and sometimes quite frustrating ordeal. I would push the strip in from one side and GENTLY pull the wire from the other side. This is where the pains taken to keep things aligned will hopefully pay off for you. Keep feeling where things get stuck (usually an LED on a junction between sections). Usually I could press the thin diffuser cover a bit and push or pull to get it past that catch point and keep feeding the LED strip into the assembled section. This dance will take a fair amount of time and patience — but the result is worth the trouble.
NOTE: Wire Cutouts
If you plan to make sure bridge lamp in modular sections as I did you’ll want to use the diffuser section ‘A’ with wire cutouts (shown below) for any place where you want to mate two sections of lamp. These sections have a place for wires to get out of the channel and allow for modular wire connectors — I used JST connectors — to be placed inside of the bridge superstructure.
In the post on electronics I’ll talk about the JST connections etc.
You can navigate back to the Enhanced LED Bridge Lamp Summary here.