In this tutorial, we’ll continue with part 2 of our tutorial on how to make a custom LED backlit sign.
Geometry
Now that we’ve gone through part one and the most complicated part is over, we’re gonna start to create the geometry, starting with the base of the outer shell. Considering how we are gonna print these parts, we figured we could split the base in half, creating connections between the bases in the middle of the part, and joining them. So we’re gonna start by going to Solid > Create > Extrude (or pressing “e”, the default shortcut for extrude) and selecting all the profiles for the first letter, in our case, the “g”. We are gonna select everything for the letter other than the profiles that are part of the 2 outer-most layers that were created in the previous steps. We are gonna extrude the base to 1.6mm.
Now we have our first body and the sketch was hidden away:
On the upper-left corner of our document structure, we need to reveal the “sketches” dropdown and click on the little “eye” icon to make the sketch visible again.
Now we can start extruding the profiles that are gonna make up the outer walls and that will connect with the base of the outer shell. Select Solid > Create > Extrude, and change the distance to the depth that you want your letter to have, in our case it will be 50mm. It’s also important to change “operation” from “new body” to “join” so that both parts are joined into only one body.
Press ok and now we are gonna extrude up the inner wall that will act as a standoff for the diffuser and create space for the LED strip. The 5050 LED Strip we are gonna use has a width of 10mm.
So we are gonna create this wall with 15.5mm, making up some wiggle room to glue the LED strip to the inner wall. Since the letters are small, it will be very tight to access and glue the LED strip to the inner wall, especially on the corners. Remember to change this operation to “join”.
Then we are gonna create the base for the diffuser. We select the inner profiles for the “g” leaving out what coincides with the outer wall and the ones we created for tolerance. It’s gonna look something like this:
We want to extrude those profiles to 1.6mm, since we plan on printing this part with 0.32mm layer height. That will add up to 5 layers as a solid base for our diffuser, but not too thick that it will waste filament or block the light too much.
Now let’s move on and extrude up the walls of the diffuser. Select the profiles that make up the outer wall of the base, change “Start” from “Profile Plane” to “Object”, and select the base of the diffuser as the start object. Change “Extent Type” to “To Object” and select the upper face of the shell part, making sure to change “Operation” to “Join”. We want this part to become one with the base of the diffuser.
And like that, we have finished our first letter.
Now we need to go to the upper left corner and hide the two bodies that we’ve just created. We need to do that so we don’t join the letter bodies by mistake. Later we are gonna join the letters that we want to keep together, so don’t worry.
Now we move on and repeat the steps for all the profiles of all the other letters.
Note that for the next letters we need to create the inner wall for the overlap between the letter to the left, even though there is no outer wall where the current letter overlaps with the prior letter.
Remember the diffuser wall will be up against the overlap of the previous letter too.
After repeating the same steps for all the remaining letters, you should have something that looks like this, where every outer shell and diffuser is a separate body.
Then for the diffuser parts, we need to go to Solid > Modify > Chamfer and add a small chamfer of 0.5mm in the back edge, so it’s easier to fit them into the shell parts.
Now we are gonna start combining the outer shells of the letters that are gonna be printed as one. Use the Measure tool in Solid > Inspect > Measure in order to check the dimensions between points of the outer shells to determine how many outer shells you’re gonna join so that they can be printed as one single part. We determined that we can print two letters at once because the bed of the printer we are gonna use is 235x235mm. If you have access to a belt printer you can combine all the outer shells and print them as a single piece.
After checking and determining which shells can be printed together, we use the Combine tool in Solid > Modify > Combine to join the parts. In our case, “ge” and “ek” will be joined, as shown below.
After printing them, we plan on gluing the two outer shells together with anchor points, so we go to Solid > Modify > Offset Face and create an offset of -0.2mm on one of the letters that will connect with the two other outer shells.
So now we have some space between the letters and that will make it easier for the two parts to be connected.
Then we have to create some simple geometry to connect the two outer shells. Go to Solid > Construct > Offset Plane and create a plane close to where both outer shells connect.
We are creating two small squares that measure half a centimeter on the sides of each end of the letters. We’ll create them above the base of the outer shell, so it has to have a distance of at least 1.6mm from the back of the letter.
Now we extrude from the part to create a half-centimeter cube that we will use to align both parts. Make sure to have it extruding out of the outer shell by selecting a face of the outer shell as the “start” of the extrusion.
Repeat the extrusion for the square on the other side of the outer shell.
Now we go to Solid > Modify > Combine and use the outer shell with the two squares as a “Tool Body”, and select the other outer shell to create the holes for the geometry that we just created so that they can both fit together. Make sure to mark “Keep Tools” this time.
Then go to Solid > Modify > Offset Face and select all the walls of the holes we created to add an offset of -0.2mm, so we can have a press-fit between the two outer shells and glue them together perfectly in place.
Now that we are pretty much done with the letters, we need to create a space for the connector we are going to use to power the LED strips. We bought a female P4 connector and searched for its dimensions online:
The information we need is the depth and diameter of the body, and we’ll use that to create a hole to insert the connector and glue it in place with epoxy glue. We are not gonna use the nut because it’s all so tight and the letters are too small to insert our fingers and try to screw the nut in.
We decided to add the connector to the end of the “K”, the last letter. We start by creating a plane on the outer face of the “k” letter since we don’t have a straight face available. We create a plane between two lines by going to Solid > Construct > Plane Through Two Edges and selecting the two lines perpendicular to the face of the “k” where we are gonna add our connector.
After creating this plane, create a sketch on it, add the geometry of the connector and add around 0.4mm in diameter so we can solder and glue it in.
Use the extrude command to make the hole:
And extend the hole to support the outer wall of the connector:
Now create a sketch on top of the base of the outer shell to create a geometry to make cuts between the letters for the LED strip to pass through. Keeping in mind the thickness of the LED strip, we are gonna create rectangles of at least 10mm in height to pass the LED strip through. It’s gonna look something like this:
Now select the profiles we created and use the Extrude tool to cut them out of the outer shells, 13.5mm from the base of the outer shell.
After that, everything is finished on the CAD side of things and all we gotta do is export all the parts to print. For that, go to the project browser, right-click each body and select Export > Save As Mesh. Remember to change “refinement” to “high”, press “ok” and save the parts as .stl files. This Fusion 360 project is available here for you to check out.
Then slice the files in an FDM slicer and you are ready to print your parts.
Assembly
After slicing, we print all the outer shell parts with an opaque filament (black ABS), and the diffuser in a white milky filament (natural colored ABS) that is not opaque. This is especially important if you plan on using an RGB strip instead of a plain-colored one like we did. Here are the printed parts:
After printing, we just needed to remove some small supports so we can start connecting and gluing the outer shells together. Since we printed these parts in ABS, we have used cyanoacrylate glue to join the outer shells.
Now we have the outer shell glued and we can start assembling the electronics.
We start by routing the LED strip around the inner wall of the outer shell. Here we are using some clothespins to hold the bends on the strip before gluing. It’s also a good idea to already cut the strips to size and solder the wires to the leads. It’s easier to solder everything up if you tin the leads of the wires beforehand. It’s important to solder the wires to the strips before gluing them, otherwise, it will be very difficult to solder having the strips already attached to the sign.
After that, we power it up by touching the wires to the power supply connector to test if the LED strips are working:
After routing the LED strip, we start gluing it to the inner wall of the outer shell with cyanoacrylate glue. We are using CA glue because the sign is too small and the bends are too sharp for the double-sided adhesive that came on the back of the LED strips.
After gluing the LED strips in place, we need to connect the negative and positive traces with small insulated wires. We solder them and add another negative and positive lead to solder the P4 female connector before gluing. Make sure to keep the wires short enough to not interfere with fitment but long enough to clear the hole for the connector for easy soldering. Go back to the connector scheme to check where the wire should be soldered on the connector.
After soldering the female connector, glue the connector into its hole, using CA glue yet again:
After letting the glue set, we can insert the diffuser parts into the outer shell to complete our sign:
Already looks cool, right? Let’s plug it in.
And we’re done! Thank you for reading our tutorial on modeling, 3d printing, and assembling a cool-looking LED backlit sign. We hope that you found it helpful and that you were able to successfully create your own sign. If you have any questions or comments, please feel free to leave them in the comments section below. Happy creating!
