Homebrew PCBs

Stefan Trethan wrote:
> On 6/21/07, Jim Hutchinson <jhutch17@...> wrote:
>   
>> If you are going to do a process several times, you will always spend
>> LESS total time if you take the time up front to build the proper tools
>> ... the steel I used was a mill "cut-off" so it had some ripples in it
>> ... if the steel had been cut when the steel was cool, the lapping would
>> be done in 30 to 90 minutes
>>     
>
>   
>> It takes about 10 minutes from room temp the first use ... I always
>> allow the temp to over-shoot by about 20 degrees then set the steel
>> block on a narrow strip of wood ... when the temp comes back down to the
>> target   i use it ... the thermocouple is on the top of the steel so
>> there is a temp gradient across the steel
>>     
>>> So for double sided you just flip the board over afterwards?
>>>
>>>       
>> I do one side at a time ... I spray paint side 2 .. image transfer and
>> etch side 1 ... then spray paint side 1 ... image transfer and etch side
>> 2 ... I do drill alignment holes for registration
>>     
>
> Aluminum might be a better choice it conducts heat much better.
> I find it amazing that you actually built a motor for the lapping and
> let it run for several days ;-)
>
> ST
>   
Hello ST ... I didn't build a motor ... I used an existing motor 
attached to a simple wooden frame ... The motor already had a 10 inch 
pulley ... the motor was a DC gear head motor so I could vary the speed 
... it took all of 30 minutes to build the fixture ... along with some 
"C" clamps and wood screws ... when I tried to lap by hand, It became 
clear that it was going to take more than an hour or so ... it was in 
the summertime and my garage is hot 100+ degrees ... so I made the 
fixture , turned it on and come in to the cool house and had a glass of 
iced tea ... ... the man at the metal shop gave me the 4x6x1 hunk metal 
... I later bought a larger 6x10 inch piece of steel for just a few 
dollars ... it was smoother and lapped in a couple of hours ... I rarely 
make more than two of anything and heating the steel clamping it down on 
the transfer stack is faster than a laminator or ironing and most 
important of all, I have control of all the important parameters and few 
limitations ...
I didn't use Aluminum because I thought strength (or resistance to 
distortion) was more important and the steel was free ...
Jim KI6MZ
>
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