Homebrew PCBs

I agree that plotting is not a good solution, i think using a printer is  
the right way to do it.
Even if you attach a printhead to the cnc, which is a HUGE effort to  
control surely, it would be VERY slow because inkjet head speeds are  
really fast in a printer, that is if you succeeded at all.

About alignment, i think i may have worked that out some time ago.

What about converting the printer to a moving flatbed version, with some  
rigid, but light, plate moving in the paper direction? It would be driven  
directly by the printers rubber rollers, but also ride on some support  
rail to keep it horizontal. This table would activate the usually optical  
paper detector sensor. On this table one would stick some strip of PCB, at  
the leading edge, against which the PCB in print is pushed. This strip  
would also have a mark in the exact center of the page width (or wherever  
the center line ends up in a mirrored print). This mark is important,  
because it allows you to align the other side. So the PCB you want to  
print would need a mark also that is visible on both sides, for example a  
notch filed into one side.

Now if you align the PCB against the edge guide, and align the mark with  
the center mark on the table, you can print the bottom side. Then you turn  
the PCB over, and again align it against the edge guide, and the center  
mark as well, and you have it positioned in the exactly same place only  
turned over. Then you simply mirror the top layer artwork and print it out.


I hope the instructions were somewhat understandable, if not i'll try  
again or make sketches.


by the way the same edge guide and center mark could be used on your CNC  
table and you would have no trouble to align the PCB 100% accurate between  
printing and driling. with almost no effort at all.

Sure, it will require more modification to the printer than just making it  
pass pieces of PCB, but i think it will give you a much better system. I  
did such a modification to a HP deskjet back then when i still thought  
those would work on copper. I was stupid and modified it that way before  
actually trying to print on copper.

ST


On Sun, 16 Apr 2006 11:31:42 +0200, Volkan Sahin <vsahin@...>  
wrote:

> Hi Herbert,
>
>   Bingo.... I used LM18245 (motor driver)  and MSP430F123 (micro  
> controller)  for step control. I bought ballscrews and linear
> slides from ebay. Mechanics seem to be stable as far as for light load  
> but I don't thing that  it is possible to reach 3 mils (~ 75
>  micro meters) with plotter pen. May be you can say that who needs 3  
> mils. Mostly I am using 5-8 mils as a  minimum trace width.
> I think easiest one is to adapt inkjet head to cnc. But neither  to find  
> cheap piezo inkjet set head nor datasheet of Epson inkjet
> head is possible. Because of that I have decided to modify printer. I  
> completely agree this is the difficult path. It seems it
> will be very difficult to find a solution for alignment problem and up  
> to now I could not eliminate paper detection sensors of
> Epson C68  most probably they are embedded to head plastic or they are  
> using capacitive detection.