Ok, so just 4 cylindrical dowels are good enough for pcb and stencil registration.
I'll try lasercutting acrylic sheet for this purpose, a lot cheaper than milled aluminum. To compensate for non-cylindrical lasercut holes, multiple lasercut sheets could be stacked. Still probably not as tight as machined aluminum, but maybe good enough.
--- In Homebrew_PCBs@yahoogroups.com, Mitch Davis <mjd@...> wrote:
>
> On Mon, Jun 3, 2013 at 9:54 PM, johannes_taelman
> <johannes.taelman@...> wrote:
> >
> > Single side works great, now I want to move on to double-sided pcb. One of the advantages of CNC-contour-laser-plotting is that the artwork-to-machine offset is perfectly reproduceable, so I was thinking to predrill 3mm mounting holes in my eurocard-size pcb stock using a drill template.
>
> Hello Johannes,
>
> Have a look at the Stencil8 system:
>
> http://www.hoektronics.com/2012/10/27/super-simple-smt-stencil8/
>
> The genius of the stencil8 system lies in the standardised 10mm pitch
> for the mounting holes. You could drill the bed of your bed on a 10mm
> grid and do stencil8 right there and then.
>
> Many of my PCB customers are using stencil8, and they and I really
> love it. When I do panelisation for them, they usually accept my
> offer to give them a stencil8-compatible tooling rail.
>
> For those of you who want to use stencil8 but don't have a mill, a
> customer of mine sells pre-drilled mounting blocks:
>
> https://www.tindie.com/products/arachnidlabs/pcb-fixture-block-for-solder-paste-stencilling/
>
> Johannes, you could make a similar block, which would let you take
> stuff from your CNC mill to the workbench for doing stenciling.
>
> Hope you like this idea!
>
> Mitch.
>