I looked into a couple of these but I believe they are for island milling. Converting the xy moves from the gerber to the G-code is the easy part the files are almost exactly the same syntax.
Its the aperture definitions that cause the problem. The origional photo plotters used an aperture wheel to project the correct spot size for the trace width and donut pads. But with the laser I will need to write macros to draw these from a single .001" dia spot. I took a look at Diptrace's Gerber output and currently they don't do anything exotic just x-y moves and apeture settings. For me to write and 8mill wide trace I will have to do the xy move 8 times with .001 offsets between writes. If this works out to be too slow I may have to increase the spot size somewhat. Would be nice to figure out how to have several different spot sizes. I guess one could use multiple laser diodes and just select the best one for the task at hand. It would be no problem selecting the correct diode in the G-code.
Craig
--- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@...> wrote:
>
> For your problem to convert to Gcode from gerber, there are three ways:
> -pcb-gcode (works ok but in Eagle)
> -export to DXF then into Cam package like LazyCAM with Mach3
> -some commerical package made to CNC mill out pcbs from gerbers (forget the
> name, was on pcb-gcode group)
>
> On Fri, Nov 13, 2009 at 11:21 AM, designer_craig <cs6061@...> wrote:
>
> >
> >
> > I had the same idea last spring and purchased a 405nm laser diode with
> > holder/lense and some Riston film off ebay. I added a heat sink to the
> > holder and have driven it up to 110ma. At that power level it will burn
> > through paper, so I have no doubts that it should harden the photo resist. I
> > did some initial crude calculations based on the Riston data and estimated
> > diode power that led me to believe it would be possible to write a .001" dia
> > spot at 80"/sec.
> >
> > My initial plan is not to raster scan the board but to vector draw the
> > pattern using my Bridgeport mill that is currently being converted to CNC. I
> > will need to write some code to convert the Gerber photo plot file to a
> > G-Code file to drive the mill. These files are very similar, the Gerber
> > format being an offshoot of the G-code format. Since I plann on using a
> > fixed spot size, wide traces will need multiple passes as will donuts etc.
> > This all has to be coded in the conversion program.
> >
> > Currently I am working on the mill's CNC conversion and have not done any
> > testing on the direct exposure part of the project. It will be a couple of
> > months before the mill is ready for PCB testing.
> >
> > Issues to be resolved:
> > 1.Is the exposure of photo resist linear ie. is high power UV for a short
> > time the same as low power UV for a longer time.
> >
> > 2.Code to make multiple passes for trace and shape widths from the point
> > gerber data.
> >
> > 3.How to get a .001" dia round spot. The laser diode output is not round.
> > How to measure the spot dia.
> >
> > 4.How long will it take to expose a 3'x5" board?
> >
> > Craig
> >
> >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>