Homebrew PCBs

Huh...
I quickly does one measurment.
I just measure blank sheet, it was 296.5mm
I put it in printer and make test print.
I measure sheet again and it is 295.5 !
Temperature in ambient is 23 degres C and 55% relative humidity.
Aprox 10 minutes later I make another measurment and sheet is 297.0 mm 
long ?!?

Ok I can expect that on paper but plastic transparency shouldn't be 
sensitive to humidity?
I just run out of them to check that on transparency too...

On 09/16/2013 11:14 PM, ctech wrote:
>
>
> Slavlo: regarding your print dimensions,..
> I had a very simliar problem, printed copper and solder mask, etched 
> the board and and then the solder mask did not line up anymore, had up 
> to 3mm on 200mm deviations. And it turned out to be the humidity, 
> makes the paper shrink and expand. Anywho a quick test you can do is 
> draw/print marks on the paper heat it up in the oven for 10 minutes 
> ~80C and measure again
> So what I do now is dry the paper in an oven then print the mask and 
> dry it again every time I use them. BTW humidity is generally over  
> 80% here all the time
>
>
> On Mon, Sep 16, 2013 at 2:15 PM, Slavko Kocjancic <eslavko@... 
> <mailto:eslavko@...>> wrote:
>
>     ...so to clean up the problem, and not to argue...
>
>     I can make small board with toner transfer metod. Fine traces aren't
>     problem.
>     I can make small board with sensitived board and printed
>     transparency on
>     laser Fine traces aren't problem.
>
>     ... But I have problem with accuarcy. If I draw rectangle 200mm x
>     200mm
>     and then print that and then measure that, the dimennsion is not
>     right.
>     With few prints made with same settings I measure the side from
>     199.5mm
>     up to 201.3mm. I tested 3 printers I own, and LaserJet 1018 and 1020
>     works identicaly. The Brother HL2030 is little better (from 200mm
>     to 201.1)
>
>     So If I pick some big SOIC or TQFP with side of 20mm the error is
>     aprox
>     aprox 0.1mm. It's bare visible with naked eye. So no problem with
>     that.
>
>     Then I pick some chip in DIL40. The last pin is aprox 0.4mm off the
>     hole. If holes are drilled oversized then package should fit, else
>     wil NOT.
>
>     Now I have terminal blocks on the edge of board. I have 20 pins
>     stacked
>     (200 mils) and in last pin the difference can be 1mm and it's not
>     possible to fit that component.
>
>     And other thing is that I drill with CNC. And of course if one
>     side of
>     board is ok the other is not.
>
>     Why the print's isnt consistent I don't know.
>     For toner transfer (printing on paper) It can be humidity, but when
>     printing on plastic transparency I think the humidity can't be
>     problem.
>     As image is more distorted in height I assume that it's printer
>     mechanics problem.
>
>     As I know that my CNC is way under 0.1mm precission It's logical
>     for me
>     to try to use it as photoploter.
>     The process is slower but got accuracy. So If I need accuracy (large
>     board) I should go with photoploter style, for small board's the
>     toner
>     transfer is better choice...
>
>     I know that my english isn't perfect, but think that majority of
>     people
>     will understand me. ...ker ne govorim kitajsko.
>
>     Slavko.
>
>
>
>
>