For the past month, my partner and I have been focusing on completing our midterm assignment, in which we hope to create a Halloween-themed box by combining different mechanics.

We started the design of the box in Gate 1, a relatively easy process where we simply put the idea together and simulated the operation of the gear in the software used to create the gear drawings.

But starting with Gate 2, things start to get tricky.As we were about to start Gate 2, cutting the needed parts through cardboard and prototyping them, someone burned both laser cutting machines in workshop.

Failure to conduct initial testing via cardboard set the stage for subsequent poor Gate 3 work. This is  also the main reason that has led to a rocket-like rise in costs in the aftermath.

Starting with Gate 3, we went straight to my work by cutting

The first problem we encountered was “scale”. Files designed in Inkscape and Adobe Illustrator on personal computers have a different scale on OEDK computers, which results in some parts being too big/small.

So we got something like head big spiders and toe big gears at the first.

So the first fix we made was to put all the part designs in the same standard scale file. This ensures that all parts are in the same scale.

Then we got our parts in a much better size. (Still use spider and the same gear as example)

Then we can print out our all parts

And start assembly the mean mechanism.

We don’t want the gears and parts hold in a place permanently, because if the some of the gears not work we can still change it. So we use tape to fix the two sides of gears too make them not moving along the dowel but still works.

Something suprised us is most of our gears are working. There is only one mechanism we think due to the design flaw, still not working after few adjustment, we decide to remove the moving function of that part.

The next challenge we faced is to put the gears in the box. We find we accidentally opened the hole of the dowel in a wrong position. But to reprint the whole box will be a big waste of the wood, so we decide to put the sides of the box to where them been cut off from the original wood piece, and only recut the whole.

Like this.

In order to satisfied the requirement of metal piece, I used water jet to print the spider again. Water jet is much better for something small and precise. It also has some problem, the design of the spider is a spider with a hole in the center for the dowel, but when the water jet cut the spider shape out, the water will flush the spider away then not allow it to cut the hole inside. Because we almost have no time to figure out how to let the water jet cut the hole first then cut the spider shape, I find another solution, glue the metal spider with the pre cutted wood spider which with a hole there, then I can have the space to fix a dowel in it.

Spiders with no holes

Metal spider surface + wood spider base + dowel

Now we have all of our parts ready, here is some pictures of the mean mechanism gears.

 

Great! Time to do the final assembly

Because we still want to access the internal of the box in the case to fix or adjust the gears, so we only put 4 sides of the box and tape them temporarily.

Some parts need to glue on the box

Hard working and another side up

Make a handle for gear rotation

After all the assembly works done, we paint the box in black and red colour, we intend to make the colour of the box looks not that “perfect” in the case to mimic the vibe, a old and bloody box.

IT LOOKS EVIL

The last thing need to do is the name tag, when I was cutting it, a good idea popup from my brain.

Last piece for the box, and FINALLY IT IS DONE.

Cost Type	Cost	Price	Source	Quantity	Total
Materials	2×4 Board	$12.89 /board	Home Depot	3.5 board	$45
	Super Glue	8.49/ 5 tubes	Amazon	1 tube	$1.70
	Wood Glue	3.97/bottle	Home Depot	1/2	$2
	Dowel	1.88/dowel	Metaldepot	2 dowel	$3.76
	1×1 3/16” A36 steel plate	$23.78/sheet	Home Depot	1/6	$2.10
	Spray paint	$5.98/can	Home Depot	1/3	$2
Labor	Workshop Operator	$16/hr	Ziprecruiter	4hrs	$64
	Prototyping Engineer (You!)	$36/hr	Ziprecruiter	20hrs	$720
Overhead	Facility Cost (Machine Time)	$99/month	Ion	5hrs	$3
Design	Engineering and Development	$42/hr	Ziprecruiter	3hrs	$126.00
Iterations	Recuts	$12.89 /board	Home Depot	8 boards	$103.12
Total					$1072.68

The estimated cost of this assignment was calculated to be a staggering four figures. These costs are mainly due to labor and material costs, and the reason for the increase in these costs is as mentioned at the beginning of the blog, that production without protyping in Gate 2 leads to a large number of errors, which increases the labor and material costs by a factor of two or more in the process. If the process was optimized, the ideal cost for this assignment would be at least $100. In addition to the costs mentioned above, one potential cost worth noting is the cost of machine maintenance/repair. Someone accidentally burned the laser cutting machine during Gate 2, and it is clear that repairing the machine also added significantly to the cost.