I really never need an excuse to 3d model and 3d print something. I would imagine if you asked most people who are in possession of a 3d printer they would probably say the same thing. However, being an educator gives me the opportunity to not only solve some problems for my students, but also demonstrate the practical application of the 3d printing technology.
This Instructable came about as a request from some colleagues who wondered if I would be able to fabricate a holder or stand for a student in my school so he would be able to look at his Chromebook during class. (Backstory: My school district now provides all students with Chromebooks as instructional tools.) Now this wouldn't normally be a complicated problem, but this particular student is confined to a wheelchair and is only capable of communicating with his eyes.
Now as a Technology & Engineering teacher I considered fabricating this holder / stand out of wood or other materials that we have in our wood lab, but since we have a few 3d printers in our department I figured they might be a nice light weight solution that allow me to model some complicated components quickly to try out in school on his chair.
Step 1: Mounting the Chromebook Holder to the Chair
I was very fortunate that this particular student already had a special mounting fixture that would attach to his chair to allow him to communicate using sight cards. This fixture is essentially a series of poles that attach to one another at various joints allowing for a variety of positions depending on the students needs. In short, I had to design a means of clamping my Chromebook holder to one of the horizontal poles so it be adjustable, but wouldn't rotate once locked in place. This would allow the aides who work with this student to adjust the Chromebook as necessary to the student.
Without this fixture already existing, my job was that much easier.
Step 2: The Parts of the Chromebook Holder
Ultimately I designed this Chromebook holder to clamp onto the metal bar that was part of the fixture that connected to the student's chair. If you look at the image at the top of this page I modeled about 80% of the Chromebook holder in one piece. This would allow me to adjust the shell layers and infill percentage to make it as strong as possible. The back portion of the the Chromebook holder with the hole in it has two places where 1/4" bolts can be passed through and squeezed to tightly grip the metal pole. When I modeled this part of the Chromebook holder, I made sure to make the hole about slightly bigger than the pole so I would be able to a material inside the clamping mechanism that would provide friction.
3d Printer Settings
I would say that for most of this project I used the following settings to make the print as strong as possible:
Shell Layer: 5
Infill Percentage 15% - 20%
The Bottom Feet
The bottom feet of the Chromebook holder snap into the moon shaped holes in the main structure of the Chromebook holder. They are ultimately glued in place with industrial adhesive and their primarily goal is to simply support the bottom of the Chromebook. Now I have designed this Chromebook holder to work with the Acer Chromebook R 11 in Pad mode (folded in half).
The Top Feet / Clamps
This part of the project was more complicated, because I had to figure out a way for the aides who work with the student to insert and remove the Chromebook while the student is traveling around the hallways. The design is similar to the bottom feet, but was essentially sliced into two parts to allow the front clamps to pivot out of the way when removing the Chromebook. Again, the base for the clamps snap into the moon shaped holes in the main structure of the Chromebook holder and are glued into place with industrial adhesive. The coolest part of this project was embedding a lock-nut into the base of the upper feet / clamps to allow the front clamp to pivot without loosening the bolt from the Chromebook. This prevents the upper clamps from coming loose at random after removing and placing the Chromebook from the holder.
I will talk more about this feature in the next part.
Mouse Padding / Padding
Fortunately, I have a surplus of extra mouse pads because of projects we complete with one of my classes. These mouse pad provided the perfect cushioning for the Chromebook so that it doesn't get damaged or slide around during use with the Chromebook holder. I also used small sliver of mouse pad to provide the necessary traction needed to prevent the clamp on the back of the Chromebook holder from rotating on the main pole that is part of the fixture that attaches to the student's chair.
Step 3: Embedding a Lock-Nut Into a 3d Printed Solid
This was the coolest part of this project because it allowed me to try something I haven't done with 3d printing before. One of the most important parts of this project is making this as safe as possible so it doesn't break and fall on the student. The primary problem I had to solve was how do I go about attaching a swiveling component to this project without it coming loose and the aides having to continuously re-tighten the hardware.
First off, the hardware I used for this particular project was an M4-07 Lock Nut (2) and an M4.7 x 25mm (2) machine screw (Though they look like bolts). You can buy either from any hardware store (Home Depot, Lowes).
In order to embed the lock nut into the 3d print I first had to create a hollowed out area within the upper foot model for the Chromebook holder that was slightly larger than the actual channel for the bolt and the lock-nut (see image above from AutoCAD). In AutoCAD I drew the shape of the bolt and the lock-nut and scaled them up by 1.07 %. this provided the perfect amount of space to easily place the locknut within the 3d print without it being too tight or loose.
Embedding the Lock-Nut
I am including a video to show you what I did for embedding the Lock-Nut while 3d printing so you can see exactly what I did and when I paused the printer. Essentially, I printed the model as normal, but when the print got to about 80% I paused the print, inserted the Lock-Nut, tapped it flush, and then un-paused the print to allow it finish the print normally. This process not only seals the lock-nut tightly into the plastic, but also aligns the holes for the metal screws / bolt perfectly.
When you watch the video you will notice that I 3d modeled small tree to the left of the print. The whole purpose of this tree is to indicate when its getting close to the 82% moment when I need to insert the Lock-Nut. The other purpose of this tree is to move the extruder out of the way of the printed component so I can place the Lock-Nut easier.
Step 4: Final Thoughts and Conclusions
Overall I am very happy with how this project turned out. Considering that this is a prototype, it has very few issues. Most importantly it works extremely well aside from some of its flaws. It doesn't rotate on the fixture and it holds the Chromebook at perfect eye level for the student. Its very easy to insert the Chromebook and remove it as well.
I would say that the main issue I have with it is that the design of the rear clamping mechanism is so well reinforced that even with two 1/4" bolts attempting to clamp it closed, it does close, but not as much as I would like to allow for more versatility. In the future I will have to redesign the clamping mechanism so that it is well supported but also allows the clamp around the fixture hole to close easier or more evenly.
Thank you for reading through this instructable, I always love sharing projects I am working on and welcome constructive criticism to help me improve.