The cost of the project will constantly be changing as parts themselves fluctuate, must be replaced due to obsolescence etc. This has happened many times over the time since 2018 when I started on this project. The below estimate can provide a rough estimate using 2023 prices. Not included is the cost of the PCBs, currently I get about 50 duplicates for 200USD, these would be nearly free at large quantities. They are not included below as they distort the QTY 1 in an unreasonable way as they are more reasonable thought of as a fixed cost at this quantity.
This table represents the cost for the electronic components. They are price both when purchasing for 1 finished ring and for 100 finished rings.
|Component||Qty||Price (QTY 1)||Price (QTY 100)||Line Cost (1 QTY)||Line Cost (100 QTY)|
|7 Seg LEDs||28||0.258||0.09||7.224||2.52|
|LED Resistor 4||1||0.16||0.097||0.16||0.097|
|LED Resistor 2||1||0.13||0.039||0.13||0.039|
|Harvest In Caps||2||0.11||0.041||0.22||0.082|
The inner core is made of precious metal. Below is an estimate of the cost of the core. This is assuming zero waste, recycling sprues etc. This shows that silver is a reasonable price while being a metal popularly understood to be “Jewellery Grade”. Versions made from gold should be no more difficult to construct, though the cost is significant. Most of the metals can be mixed with second hand material from previous runs at a maximum rate of about 50% new : 50% old. For efficient reuse of sprue material it would be important to have the final product take > 50% of the volume of the casting tree. (difficult with such thin inner cores). I would need about 10cc of metal to fill sprues etc, which is a significant cost if using gold.
|Metal||Density g/cc||grams needed||Price $/g||Cost $|
The labour involved in producing this ring is likely the biggest factor in its viability. Unlike most electronics project, even at medium scale it must be made by hand, even PCB pick and place is unlikely to be viable to automate. Below is a very rough estimate of the time taken for each process. Note that the metal casting steps can produce multiple rings in parallel with little extra effort, all other processes are done per ring. Attaching a dollar value to this time is difficult. I personally do this as a hobby, which is fine while making one or two, and I have all the skills and experience to produce the ring in one place, employing such a person is not normally free! You can see that the time taken is about 1 working day per ring, feel free to estimate this cost as you feel is appropriate. Perhaps with pipelining, process improvements, we could estimate 2 rings per day per worker is possible when producing > 500 rings a year.
|Operation||Man Hours||Rings Produced||Per Ring Time|
|Fixture PCB, Stencil||0.25||1||0.25|
|Place Rear Parts||0.75||1||0.75|
|Manual Paste Top||0.25||1||0.25|
|Place Top parts||0.75||1||0.75|
|QC Circuit Function||0.5||1||0.5|
|Solder Prog Pins||0.1||1||0.1|
|Print Casting Tree||0.25||6||0.0416|
|Print Clean Up||0.5||6||0.0833|
|Pour and Cleanup||0.75||6||0.125|
|Metal Core Total||3.5||6||0.583|
|Setup Epoxy Cast||0.5||1||0.5|
|Ring Production Total||7.433|
It is difficult to appropriately assign the cost of equipment to the project when working on a hobby basis. In general the equipment I use is of modest quality, appropriate for non-professional use. This set of hobby-level equipment costs in the region of $2000, if I was making >100 rings per year, more appropriate equipment would represent an outlay of ~$10,000. Estimating other fixed costs will be left as an exercise for the reader, > 100 rings per year would be a small business, and have the associate miscellaneous costs (Workshop space, Legal, HR, Accounting etc).
Cost Of Goods Sold
Adding in some extra lines without too much justification we can estimate the COGS (Cost of Goods Sold).
|Line Item||Cost Per Ring (Silver, QTY 1)||Cost Per Ring (Silver, QTY 100)||Cost Per Ring (Gold 18k, QTY 1)||Cost Per Ring (Gold 18k, QTY 100)|
|Metal Core (Silver)||2.66||2.66||267.69||267.69|
Price To Market
(This is all hypothetical, currently I have no intention to sell these rings)
The final sale price of such a ring would depend on the goals of the business. If this is a cottage industry/hobby, perhaps the margins are capably of being thinner, essentially operating as a justification for getting nice tools. However for a product to be viable it should be sold for at least 2x of the COGS price. This is to account for the supply chain, advertising, returns, damage, waste etc. Ideally a high risk product like this would have a multiplier of >3. Failure of the electronics, gold wasted into broken product (recycling is more difficult with epoxy casted/electronics laden gold), returns based on customer taste or incorrect sizing are all factors that would increase risk over a typical electronics project.
Therefore it is hard to imagine that the current design could be sold for much less than about $1000 USD, or more for a gold version. Reduction of the labour price is the lowest hanging fruit, perhaps pipelining operations into many simpler jobs would allow the use of less skilled people. Though this would always be a luxury product, as such craftsmanship and attention to detail are a must, so retaining any employees would be critical to developing all the skills necessary to reach the target quality.