Paint is but a corruption of the pure form…

MILLING HELL YEAH

Yes milling! Milling is very fun. It’s also very useful! In this assignment we will be using a CNC mill to carve out some parts! This is a three stage process. Design, machining, and post-processing.

 

DESIGN

Some people say there is no such thing as the perfect part. The superior shape. Those people have obviously never witnessed the magnificence of a gear. Practically the flagship shape of the mechanical world. Okay that aside, as one might have guessed, Ill be cutting a gear!

The design was extracted from the noun project. The SVG file looks like the image below:

I ported this onto easel, and added some other shapes to create different depths of cut, to give the shape some 3D-ness and create the final part geometry. The final shape, and render on easel looked like the image below:

 

MACHINING

This was very very uneventful actually! I kinda expected to have all sorts of trouble… but… I did not! The cut was 45 minutes long, and it went flawlessly both times, I only had to pause it once, because I needed to leave it unattended for 2 minutes. Both parts cut nicely, and I was pretty satisfied with the shape and size, all of the features were present, and the gears even meshed together quite well! The only downside was having to stay and babysit the machine for an hour and a half. That was a serious test of patience. Unfortunately my phone was charging back home, so I could not take any pictures or video of the process.

 

POST-PROCESING

This was a bit time consuming. Due to the somewhat intricate part geometry, the pieces had a lot of edges, and going through all of them smoothing them down and deburring with a cutter was a bit labour intensive. Nevertheless, it was done, and the gears looked pretty fresh after that! Unfortunately due to a hand spasm one of the gears lost part of a tooth.

After all the surface polishing and edge softening, came the coating. Now here’s the thing. One can probably tell from my waterjet diamonds, and midterm project, that I am a big fan of bare looks. I really like the look of bare wood and bare metal. I especially like them together, hence why none of the parts in my midterm project are stained/painted or otherwise coated. It’s not that I did not have time, or was too lazy to do it, but I actually designed it arround the bare wood on bare metal look. As a friend often says, “Its not a bug, its a feature”.

However, the gods of ENGI 210 demanded post-processing. And as beautiful as I thought the gears looked in their bare pine wood, I knew I had to stain them. I chose a light coloured stain, believing it would preserve the original colour better. Unfortunately, it worked just as intended. Staining the whole part in a white-cream tone. A layer of clearcoat after, and they were done, much to my dislike. It also seems like the moisture in the stain fluid made the wood swell a bit and roughened the edges. Oh well, what the gods want, the gods must have.

Here is a nice picture of the finished parts, this time, I did have my phone on me. Why I forgot to take a picture before coating them? That is a question for minds greater than mine.

 

Cost of Production

Material cost:

The material cost was only two 3.5×3.5in pieces of 0.75in thick pine wood. The amount of stain and clearcoat used were negligible, and amount to less than one cent.

Pine wood (0.01$/sqin) = 0.12$

Tool time cost:

Each gear took 45 minutes to cut on the mill. For a total of 1.5 hours.

Most eastimates place $/hr at around 40$/hr. Which for 1.5hrs, adds up to 60$

LabouR Hours cost:

The average pay for a workshop worker (similar conditions to the OEDK, not a factory) seems to be 25$/hr

Between setting up the cuts, the surface post-processing, and the finishing, I had to spend about 4.5 hours total working on the parts.

This brings labor cost to 112.50$

TOTAL:

Both gears together thus add to: 172.62$

To be perfectly honest, this is horrendously inefficient for two tiny wooden gears. That makes it 86.31$ for a single gear! Boy with that money I could have bought at least a few IRON gears at McMaster Carr! Although, with a bigger not-baybisittable CNC, a structured workflow, and cheaper factory type labour, I bet I could be chucking them out by the thousands for a fraction of that price. I mean, my material costs, aka my variable costs are only 0.07% of the total final price!! My whole budget is blown on fixed costs! Now, Im not very experienced in efficient mass production, but that sounds stupidly inefficient.

Although one could factor in the value gained in terms of useful experience and skills learned, which starts to balance the scale a bit.