BOM, cost

[larsbrinkhoff]

Quote from Signature Plastics is $3123 initial cost, then $60.24 per keycap set.

CC @dabridgham

[dabridgham]

Is that initial cost just for one keyboard? If so, does the overlap help when adding the other keyboard or the Space Cadet keyboard? Also, is there flexibility in mounts or profile or would that invoke a whole new initial cost?

[dabridgham]

Here's an initial attempt at writing up a BOM for the whole keyboard. Lots of guesses in here but it's a start. Many items assume quantity 50 keyboards.

Item	Qty	Price	Extended	Notes
keycaps	73		$122	Using Lars' quote from above, amortizing initial cost over 50 keyboards.
keyswitches	73	$0.50	37	Cherry MX from NovelKeys
stabilizer set	1		20	Plate-mounted from NovelKeys
diodes	73	0.05	7
LEDs	3	1.00	3	No LEDs on either the SAIL or Knight TV keyboards but why not put space for them on the PCB anyway. They're optional.
Resistors	3	0.10	1	For the LEDs
Keyboard PCB	1		10	Double-sided, 350x110 mm, ENIG from PCBWay, qty 50
Interface	1		20	A Teensy is about $20, maybe double that (?) if we try to make out own.
plate	1		20	From BigBlueSaw qty 50, laser cut. Waterjet was more expensive but maybe cleaner cuts? Lasergist only had qty 1 price at $100 but worth asking about a quantity discount.
case	1		20	For the sandwich style of case, this is some number of laser-cut sheets of acrylic to build up the desired thickness. That $20 is a pure guess, just to fill in the table.
rubber feet	4	0.50	2
m3 screws and nut inserts	8	0.50	4	I didn't actually go look up prices for screws.

So it totals to $266, with those estimates.

[larsbrinkhoff]

Thanks! I was hoping under $200, but all things considered I think this reasonable considering the circumstances. Since the keycaps is the most expensive item, I'll ask around for more quotes.

@dfnr2, do you think the table above looks complete?

[larsbrinkhoff]

Is that initial cost just for one keyboard?

Zero keyboards really. I sent the spreadsheet and got quotes for qty 25, 50, 75, 100. I reverse-mathineered the numbers.

If so, does the overlap help when adding the other keyboard or the Space Cadet keyboard?

Presumably it would help the SAIL keyboard since 26 keycaps are exactly the same (except for color). Maybe not the space cadet because it has front symbols; also it generally move many things around from the SAIL/Knight layout.

Also, is there flexibility in mounts or profile or would that invoke a whole new initial cost?

They asked which switches I wanted, and I replied Cherry MX. Profile is SA row 3 throughout. So the quote is for that configuration.

[dfnr2]

1) A laser cut metal plate would be nice, but I have found that FR4, if appropriately fixed to the PCB, gives plenty of stability. FR4 can be made by the PCB manufacturer and is much cheaper in small quantities. Another option is to skip the plate altogether and screw a couple of stainless bars across the length of the PCB. I suspect that will be about $5 rather than 20, and since everything will be screwed down anyway, this should be every bit as stable.

2) The encoder can be included directly on the PCB. The firmware already supports an ATMEGA2560. If you want to use alternate firmware such as QMK or kaleidoscope, then the teensy might be a good option, but I think that even QMK and kaleidoscope will run on the 2560. This will save at least another $15

3) Stabilizers are only needed for the spacebar and maybe any 2u keys if the keyboard has them. They can be bought in bulk much more cheaply, about $1 for the spacebar, and probably none needed on the other keys. So you could subtract $19 from the estimate.

[dfnr2]

If you use the footprints in the unified keyboard project, you can use the classic layout as a starting point for both the PCB and aligner plate. You can use the footprints in the project to make a keyboard that takes both Cherry MX and Futaba keys, and also diode and resistor footprints that take either SMT or through-hole parts. Some folks don't like surface-mount parts on the retro hardware. However, I find that it's much cheaper and easier to have the PCB fabricator also assemble the surface mount components on to the board, so all you have to hand solder is the keys themselves, and maybe some connectors.

[dfnr2]

For the case, it would be worth quoting a bent metal case. I think if you make a PCB-based aligner board, then the cost of laser-cutting and bending a case would be about the same as your quote for the laser-cut aligner + acrylic case. Also, I bet the acrylic case, if laser cut, would actually be more than your estimate.