Overview
This assignment tasked me with manufacturing and assembling a working clock/pencil holder using various manufacturing processes. Using a manual lathe, vertical mill, and various finishing techniques, I turned brass, steel, and aluminum stock into functional and polished components up to specifications.
Advice for future Mech 200B Students
This was my first real manufacturing project, moving me from rapid prototyping and intuition driven design, into industrial drawing driven production of quality controlled metal components. This learning curve taught me some valuable things about manufacturing.
- When cutting a critically sized feature, opt on the side of oversizing a feature if it’s going to be processed further. I had to completely redo my aluminum clock base from scratch because I cut it to the specified length and then sanded it out of tolerance during the finishing process.
- Budgeting time and considering how the shared space influenced machine availability.
- The time you take to ensure quality in each step will save more time in redoing or repairing a given feature. Attention to detail feels longer, but is actually much quicker.
Material Cost Estimate
$3.84 per unit
$9.05 per unit
(1.816 lbs, $4.98 per lb)
Total Material Cost Per Screwdriver
$12.89
Labor Cost Estimate
Machinist hourly rate:
$25.631/hr Nationally
$25.00/hr Locally
Knurling production time:
~0.75 hrs
Drop forging production time:
~0.25 hrs
Grinding and Finishing time:
~2 hrs
Hardening and Tempering production time:
~0.25 hrs
Total Machining Time
~3.25 hrs
Estimated labor cost
$81.25
Cost estimate
$94.14 Per clock
Efficiency improvement proposal
- To cut production time, instead of using a horizontal band saw to cut the stock to length, a CNC break will work all the same, saving time for each part and allowing us to upscale the production size.
- Instead of a manual lathe, the brass and steel components will be turned in a CNC lathe, reducing manufacturing time, labor costs, and ensuring high quality control and repeatability across parts. An operator must still be present to flip the components around between operations. Finishing can also be done on the CNC lathe, as the toolpath can be optimized to achieve a specified finish, eliminating sanding the cylindrical components altogether.
- The manual vertical mill will be replaced with a 3 axis cnc mill with an automatic toolchanger. This allows for multiple pieces to be produced in a single operation, saves time with measuring and toolchanging, and doesn’t require much to upscale as the stock can be held by its parallel walls. The part still needs to be flipped between the operations, and custom fixturing is still required for the clock face slot, but this allows features like the chamfer and any personalization to be looped in to one machine, saving time and manufacturing complexity
- The turret lathe used for the brass nut is still a very streamlined process and would gain little from automation.
- Finishing the clock can now be streamlined with the incorporation of a palm sander, which reduces manufacturing time to roughly 20 minutes for finishing the clock face to 600 grit
- Laser cutting the acrylic sheet can now be done in bulk, instead of one at a time, with multiple clock faces cut at the same time, reducing labor costs and manufacturing time.
- Chamfering and rounding the edges of the clock face is still fine using the scraper, as the only way to effectively streamline this process would be with a proprietary machine and an automated assembly line
- The assembly process should remain mainly identical, although configuring the assembly process into an assembly line could cut manufacturing time, although it might increase labor costs overall.
Mass Production Cost Estimate
Traditional Production Method
10,000 Units
$94.14 Per Unit
3.25 hrs Per Unit
32,500 Hrs Total
$941,400 Total
Optimized Production Method
10,000 Units
$44.14 Per Unit
1.25 hrs Per Unit
12,500 Hrs Total
$441,400 Total
