Building a box—-not so challenging a task it seems.
Before starting to build the box, that was what I had in mind—-nothing more than putting 5 pieces of wood together. But clearly, I learned a lot more than just how to build a box.
The first step in engineering is always about planning. The more you consider, the less likely you get beaten up by failures. As I learned from my past experiences in ENGI120, DO NOT TRUST YOUR EYES!!! DO NOT TRUST YOUR EYES!!! DO NOT TRUST YOUR EYES!!! (Important stuff should be emphasized thrice.) Because materials are never perfect. In most cases, the edges of the material may not be perfectly straight and perpendicular to each other. And it was a pretty frustrating experience in my ENGI 120 project when I found the bottom edge of a square piece is actually shorter than the upper edge, and that the middle part of my piece was slimmer. You never know what did the last person do to the material, you can only trust on your cut. So this time, I left approximately 1/8 inch on each side of my panels to be later sanded down, drawing straight lines by placing dots first with measuring tape and connecting the dots with a ruler. Than I measured the pieces I need. And again from past experience, I left an extra 1/8 inch around my cuts for the saw blades.
So far so good. And I wondered if I could try some more complicated connection methods for my box. Inspired by the finger joint method, I thought of the following. (See Figure 1 & 2)
Figure 1. TinkerCAD model of the connection method I tried to build
Figure 2. 2-D outline on the MDF piece, the shaded parts were to be cut out
I am glad that Dr. Wettergreen found me first before I started to cut the MDF. He pointed out that this was something that I never tried before, and there was a very high chance of failure. So instead of directly cutting on the pieces I prepared, I tested first on scrap pieces to see if I could actually make such cuts and if the connection method was feasible. And here are the results:
Firgure 3. an attempt to cut down a corner. Because the cuts are to small, the saw blade is circular, and the saws are not designed for depth control, this was the best I could do.
Figure 4. Trial run for the connection method.
Glad that I tested it first, and obviously, the connection method failed. The MDF piece is too thin for the screw–it’s very easy to splinter. If I tested this directly on my piece, it would be a whole new story.
So I went back for the simplest method–directly aligning the pieces and drill them together. This time, I manged to consider more details before actually making irreversible actions. I prearranged the pieces, marked the and made the pilot holes, marked across the sides of the pieces to make sure when I put them back, they were arranged as the way they were when I drilled the holes. (Figure 5)
P.S. I drilled the pilot holes first because it might cause problems if I rounded the edges first.
Figure 5. The pilot holes and the marks
Then I rounded the edges with the router, and now every thing is ready for assembly. Screwing the pieces together is not so hard. But still I took extra caution, because this time, I was afraid of splintering the wood. Pro tip: let the screw to drive itself in, instead of pressing the drill forcefully against it.
I tried to screw the screws down in a little bit more to let the phillips head to be level with the MDF surface. I failed. The MDF surface prevented the phillips head to go down any further, and the drill just abraded the phillips head (Figure 6)
Figure 6. A normal screw, and an abraded screw.
Because it would make the connection less stable if I change the screws that are already done, I applied changes to the screws that connect the bottom to the walls. (See Figure 7)
Figure 7. a shallow round groove applied to the pilot holes on the bottom piece.
I used the drill press with a thicker drill bit, that matched the size of the phillips head screws. This allowed me to drive the screws a little bit deeper without damaging the screws.
A few problems arose when I used the drill press:
- The drill press seemed to be set in a reverse way. When you spin the handle, the drill rises, and when you release the handle, it drops down automatically. It is not intuitive at all. You have to rise the drill and hold the handle to take out your piece, and it’s harder to control the depth of the drilling. (See figure 8)
Figure 8. gif. of the confusing drill press - The laser does not accurately aim the spot of the drilling. As can be seen in the following figures, it is a little bit off, and it would be just better to aim directly with the drill bit. (See Figure 9 & 10)
Figure 9. The drill bit accurately rests on the pilot hole
Figure 10.But this is where the laser focuses when the drill bit is exactly above the pilot hole
After finishing the assembly, I sanded the entire box. First with the sanding machine to make all connections between the MDF pieces to be smooth and to roughly round the edges, then with chisel to round the corners, and finally with sandpaper to smoothen all surfaces. (Figure 11. 12. 13)
Figure 11. 12. 13. Sanding results
Further, as I just reinforced my skills for the laser cutter, I refined the box with some nice engravings, and this is how it looks now!!!(See Figure 14. 15.) Hoping to apply wood protection coating in the next few days when the weather is nice.
Figure 14&15. Owl, name and our Alma Mater: Rice’s Honor. YA!
One thing to notice, it’s pretty hard to have the engraving exactly at where you want. Always measure twice and run a quick test trial. (See Figure 16 & 17)
Figure 16. 3 cm long test samples with 25% speed & 45% power (left), same speed & power using a image with higher contrast(right)
Figure 17. trying to find where does the laser cuter start corresponding to the printing settings and where the image lies in the template file.
In summary. Things won’t go exactly as you imagined in your head. Designs all work in ideal situation but the reality is not ideal. Machines and measurements require calibration. Certain ideas may not work at all. Be ambitious but also rational and careful. Always run a test trial instead of wasting time on potential failures and figuring out what you should have considered. Tests are not limited to the final stage of prototyping.
