Product Design: Allen Key Holder (Part 1)

Isometric view of the finished product in Solidworks.

For my first real design project I was given a problem, solve an issue by creating a simple design with mechanical properties. I chose to design an allen key holder because allen keys are always getting lost, and they're a pain to hold when you're working. At first I had a very basic design, but the project proved to be more challenging than I originally expected. I started with a flat oval shaped 2-D holder, I slowly made changes and improvements from there.

The first real change, oval shaped to rectangle.

The first change I made was going from an oval shaped holder, to a rectangle. I felt the change was necessary, an oval is an obscure shape and harder to build off of than a rectangle.

Frontal view of the first 3-D model.

Inside view of the first 3-D model.

The next change I made was to go from a 2-D model to a 3-D model. At first I assumed the allen keys would be able to hang in place, so a 2-D model seemed reasonable. I realized my ideas worked better on paper and that it was time to improve. At first I only made the holder 3-D, but doing this still didn't solve my issue of the allen keys falling out.

Frontal view after changing from the large bulky rectangular box.

After making the holder 3-D, I decided it was too bulky and wasn't optimal in working conditions, so I reverted back to original flat 2-D holder. Rather than making the holder bulky, all I needed was a small frame and a door to hold the allen keys in place. This is also the point where I started designing the hinges, as you can see I started out with just scraps of paper.

After adding the latch and hinges. (closed)

I was originally going to make the hinges resemble door hinges, but I realized there would be no way to assemble it. The way a door hinge is made, is by sliding a long cylinder in between tubes, and then flattening the end so it won't slide out. There would be no way to flatten it with  my design, so I switched to watch pins which are meant to clip in.

Frontal view of the holder after the belt clip was attached.

As you can see in the pictures above, the latch was simple. I attempted using other locking mechanisms but this one worked the best. One other thing that is very noticeable in the image above, is the durability of the materials. At this stage of design, the cardboard was starting to separate and tear. However, there was benefits to this, it showed me what areas of the holder were the weakest, and that might break even on a model of stronger material. This is when I decided to cut off the handle. The handle I'm referring to is the thin piece at the very top of the design with copper wire bent around it.

After cutting off the handle.

From this point I did most of my design in Solidworks. The physical model was only missing the clip for attaching it to a belt, but it was starting to fall apart where it was glued. The belt clip was simple to make, I started by making a rectangle and cutting a slot out of it for the belt. Then I just rounded out the edges, so it wouldn't cut anyone when made out of harder material. From here I made small improvements on the design.

Before rounding the hinges.

After rounding the hinges.

Working in Solidworks I was able to make improvements that were near impossible when working with cardboard. For example, I made the hinges lie flush with the door, and rounded them out so the door wouldn't clip them.

I've been asked a lot of questions while designing this so I thought it would be appropriate to compile a general Q & A section.

Q: Was the physical model hard to make?

Left side view of the handle bending.

A: No, the physical model was easy to make once I had a design in mind. I ran through a few ideas before I decided to stick with the one I have now. However an issue that I constantly struggled with was the durability of the materials. I used cardboard and copper wire to make the physical model and the cardboard didn't always hold up so well. The copper wire snapped easily and would sometimes destroy the cardboard being that it is a harder material. In the photo above you can see how the handle was tearing and bending.

Q: What made you want to design an allen key holder?

Original hinge concept design, drawn by Mr. Grosinger.

A: Well, I wanted to keep the project reasonably simple, and having experience in electrical work, I remembered how annoying it was to hold small allen keys as you climb up a ladder, especially if you need other tools. I was also told this would be a great first project by my teacher Mr. Grosinger.

Q: How different was your first model from the final design?

A: My first model was immensely different from my last. The first model was an oval shaped holder, with no way to secure the allen keys in place. It was a flat piece of cardboard and the allen keys basically just hung in place, and would easily fall out. Slowly, I started adding on bits and pieces until I got to the model you see now.

Q: So, What made you change your original design?

A: I started by sketching out my idea on paper. While I was trying to convert it into a physical model, it became apparent that the idea seemed to work on paper. On paper the design worked well, the allen keys stayed in place and it clipped onto a belt with no problem, all in a compact design I might add. In reality, the allen keys get pushed out of the holder just from walking, and this model was too flimsy.

Q: Okay, so the cardboard model revealed some flaws.  What changes did you make to correct this?

A: The first change I realized I had to make was, going from a 2-D to 3-D model, a flat piece of material wasn't going to cut it. Secondly, I needed something to hold the allen keys in place, without securing them they would fall out no matter what else I changed. Later on I made improvements, but these were really the only things that I changed.

Q: How did you secure the allen keys?

A: My first attempt at securing the allen keys was by adding clips on the back of the holder. I believed the short end of the allen keys would clip in and stay firmly in place, but the clips were extremely difficult to make out of cardboard. With the clips not working mechanically how I pictured them, I decided it was time to try a new design. This is when I started to design the door and latch, which ended up working exactly how I wanted it to. It left enough space so that it didn't put too much pressure and break the holder when the allen keys moved, but enough strength to hold them in place.

Q: What was you biggest challenge?

A failed attempt at 3-D printing the door.

A: My biggest challenge was 3-D printing the model I created in Solidworks. Part of the problem was design flaws like the hinges, but most of the issues came from the printer itself. As you can see above, the printer isn't perfect. In this case, the holder became snagged on the nozzle, it started to get dragged around with the nozzle, which ended up burning a hole through it.

Q: What other problems did you encounter while working with the 3-D printer?

Printing without a raft.

A: Another issue I had was detaching the actual piece, which is the red plastic section, from the raft, which is the white layer underneath. The raft was a necessary step in the design, without it the plastic wouldn't stay in place, it would move with the nozzle and could never properly form the correct shape. What you see above is what happened only seconds after I started trying to print it without the raft.

A third attempt at printing the door piece.

Better example of the piece bending.

The raft may have been a necessary piece but it was also causing complications. The piece I was attempting to print was a thin piece, which made it hard to detach from the raft without breaking or bending it. In the first picture above, the problem of the piece being dragged is very apparent, you can see how it was pushed during the printing process causing it to fail. . The second picture illustrates  how the part was bending when trying to detach it from the raft. I was able to detach a small piece in the upper left corner, but the rest was stuck together and proved too difficult to detach without breaking the part.


Q: Once you make a 3-D plastic printed prototype, how do you plan to test it in a real world scenario?

A: I plan to take my 3-D printed model with me to work over the summer. I will be working in the electrical field again, over this two month period I will see how my design holds up.

To be continued...