Re: [CAD_CAM_EDM_DRO] milling circuit boards

Yes, it does have limitations, no questions on that. But doing simple
boards in-house, even for small production prototype runs is
reasonable. And for the hobbiest, it has a high 'geek factor'
associated with a 'do it all' solution.

No, I did nto consider lots of the other combo assembly/pcb house
options. Also you can get boards done offshore (china) for cheap, but
it takes longer (think 2 weeks rather than 2 day turnaround), but from
what I have seen you get more boards for the extra time. Again,
tradeoffs. There are shops in Mexico and China/Tiawan (and the ilk)
where they can do some enviromentally nasty things that keep their
cost down, but is it worth it? ... Those places will also do the
component acquisition, assembly and testing. ... For prototyping, if
you can get a good high-school tech and pay $20/hr to have them roll
it together all in-house, I think many small companies would be better
off at least for the prototype stage.

Oh well, I need to get some work done too! ... Later... Jack

Quoting Dennis Schmitz <denschmitz@...>:

> Good analysis. Leaves out option of a combo assembly/pcb house and
> that boards from them come with soldier mask and silkscreen. Beyond a
> certain complexity, you'd want their pick/place machines to assemble.
> And you can only make 2 layer boards, so it's difficult to do anything
> with a microcontroller.
>
> But it could pay back for small projects.
>
> On 10/6/06, Jack Coats <jack@...> wrote:
>> Dennis, (sorry this is so long)
>>
>> My take is,
>> 1. environmentally friendly - a good tree-hugger answer
>> 2. no chemicals - I don't like to keep things that others could get into
>> around the house.
>> 3. on-demand prototyping - it is hard to build a board 'yesterday', but
>> at
>> least you can have it 'today'.
>> 4. incremental costs,
>> 4a.for the home shop person, is minimal. In a hobby, part of the fun is
>> in the process even more than the product.
>> 4b.For business use (prototype or production) the purpose is the product,
>> not the process of getting to the product.
>>
>> Incremental costs for a business are more, because time is the same as $$.
>> Costs of preparation are close to the same. If the time value is worth
>> more than the cost of production in small quantities, then it can be worth
>> milling your own boards.
>>
>> If you have a tech that you pay $20/hr (fully burdened), and it takes
>> 2 to 4 hours to mill the prototype board, you have paid for a service
>> bureau to do the boards. The only really difference then is the
>> turnaround time. What is that worth?
>>
>> Ok, you give the same circuit to a tech (paid the same), how long does
>> it take to get a debugged breadboarded circuit back from the tech?
>>
>> If the $$ are the same or less then it makes no sense to do it with a
>> machine.
>> If you will be doing the layout and you would spend 2 hours using
>> Eagle, and 0 or your hours using a tech, and your fully burdened
>> expense is about $50/hour, then it could be cheaper to have a tech do
>> it from schematics/drawings.
>>
>> A machine allows the flexability of a small production run, and
>> 'easily' reproducable wiring, in case you need several of the same
>> circuit. But the economics should guide a business decision.
>>
>> I like to think of things using tables for comparison.
>>
>> Scenario 1: you design, layout, service bureau used, tech builds
>> Scenario 2: you design, layout, tech uses machine, tech builds
>> Scenario 3: you design, tech breadboards from schematic
>> Scenario 4: you design, tech does layout and uses machine and builds
>>
>> Scenario 1 2 3 4
>>
>> Your time $50/hr
>> design time 4 hr=$200 4 hr=$200 4 hr=$200 4 hr=$200
>> layout time 2 hr=$100 2 hr=$100 0 hr=$0 0 hr=$0
>> wait time (non-billable - but lost opertunity cost)
>> wait on tech 3 hr 3 hr 4 hr 5 hr
>> wait on
>> service 16hr (assume 48 wall clock hour delivery)
>> bureau
>>
>> Service bureau cost
>> guess? $60 $0 $0 $0
>>
>> Tech time @20/hr
>> layout time 0 hr=$0 0 hr=$0 0=$0 2 hr=$40
>> run cnc machine 0 hr=$0 1 hr=$20 0=$0 1 hr=$20
>> build and check
>> one board 2 hr=$40 2 hr=$40 4=$80 2 hr=$40
>> -------------------------------------------------------------------
>> Total $400 $360 $280 $300
>> Wall clock time 25 hours 9 hours 8 hours 9 hours
>>
>> Second to N boards per board:
>> $100/board $60/board $80/board $60/board
>>
>> 10 board total: $1300 $900 $1080 $840
>>
>> Scenario 2 and 4 the 'machine' is a small prototyping CNC mill.
>> Now do you use it enough to have that payout?
>> Is the convenience of a mill worth it?
>> Do you have a 'lost opertunity cost' in the wait time?
>>
>> On the payout, assume you use it just for small runs, saving $40 per
>> run, and it cost $4K, then you must go through 100 runs to break even.
>> If you do 1 per week, this is a 2 year ROI (return on investment).
>> Most companies would bite on that. One company I worked for required
>> a 18 month ROI.
>>
>> If you find a 'magic bullet' answer, we would all like to know!
>>
>> ... Thanks, I enjoyed the mental gymnastics. ... Jack
>>
>>
>>
>>
>> Quoting Dennis Schmitz <denschmitz@...>:
>>
>> > Sorry, this isn't an answer, but another question. I think I've read
>> > posts from 2 or 3 people milling circuit boards, or trying to. What's
>> > the cost breakdown? Is it really and truly cheaper to make these
>> > boards after you factor in your time and amortize your equipment?
>> >
>> > You can get some pretty good prototype quantity boards from internet
>> > outfits like PCB123 now for very cheap, and if you're running
>> > production, there are plenty of board shops out there all undercutting
>> > each other. Check out the back section of any of the EE mags for a
>> > long list of them.
>> >
>> > Even 10 years ago "breadboard" meant giving a hand-drawn circuit to a
>> > tech to solder together with perfboard. Today it means doing a quickie
>> > in Eagle and sending it out to an overnight proto house. It's cheaper
>> > than paying the tech.
>> >
>> > So where's the upside? Why bother building a machine for it? (serious
>> > question, not sniping)
>> >
>> > This is probably off topic, so feel free to email me directly.
>> >
>> > TIP: you always pay for one panel, so lay-up several different ones in
>> > the gerbers. If you have space, there are a bunch of free patterns for
>> > proto-boards available to fill it in.
>> >
>> > On 10/5/06, wdavis364 <wdavis@...> wrote:
>> >> Shopping around for a router, Some router have 1/4 collets and some
>> >> have 1/4 collets and 1/8 collets. Not knowing much about this, what
>> >> size collet will I would most likely to be using in milling circuit
>> >> boards. Will 1/4 collets handle the very small size drill bits(1/32)?
>> >> Thanks for any advice on this.
>> >> bill
>> >>
>> >>
>> >>
>> >>
>> >>
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>> you have trouble.
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>> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
>> sister site to the CCED group, as many of the same members are there, for OT
>> subjects, that are not allowed on the CCED list.
>>
>> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
>> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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> Addresses:
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> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
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> wanliker@..., timg@...
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> davemucha@... [Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to
> reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to
> be a sister site to the CCED group, as many of the same members are
> there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING
> THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
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"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
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"Any sufficiently advanced technology is indistinguishable from magic."
-- Arthur C. Clarke (1917 - ), "Profiles of The Future", 1961 (Clarke's
third law)