Homebrew PCBs

Hi Curt,

So the raster is scanned dot by dot no matter if cutting is needed, and  
with no regard to if the cutting is finished?
That is a good KISS approach, and if you go slow enough there should not  
be problems.
However in the future there would be speedup potential.
Also, i didn't mean to use the groundplanes for return, i thought when you  
have large copper areas you might just move over them fast and not need to  
scan it slowly if there is no cutting to be done.

I think the software should not be too hard to do, esp. if one uses a  
picture with the correct resolution already.

You know, if someone would find a good plotter pen or inkjet head i could  
even do the componet legend on this machine. Wouldn't it be great to do  
_all_ PCB work on the same machine? Now... a solderpaste dispenser and a  
pick and place head... okok i'll stop dreaming, those things are for later.

ST


On Wed, 29 Jun 2005 07:26:33 +0200, curt_rxr <cwrxr@...> wrote:

> Hi Stephen,
>
> I'll answer your questions from the Electronics 101 thread:
>
> ST wrote:
>
>> Yes, i have read rotating the electrode is good for edm.
>> I don't fully understand electrode erosion of different materials
>> tho.
>> Rigging a pump would not be a problem, i'm quite used to that sort of
>> thing with a watercooled PC by now..
>
>
> I used a combo dielectric duct and return ring around the electrode on
> a EDM machine based on an HP plotter.  The idea was to use gravity
> feed of distilled water ( the dielectric ) through a copper pipe
> around the elctrode which also provided the pulse return path.  The
> system had a spring to keep the duct in contact with the PCB and
> attached plastic rod to provide capacitive feedback for depth.  My
> hope was to speed up cutting the board by leaving a groundplane
> however the drag of the duct slowed things down too much.
>
>
>
> ST wrote:
>
>> I would like to PC control it like a normal cnc drill.
>
> You could do that with the A3967SLb s on a driver board and control
> software on a PC.  Maybe EMC?
>
>> How do you scan one line, at fixed speed or is it variable with
>> current?
>
> The gantry moves along the x axis in 0.001" increments.  The holding
> torque of the steppers and the "stiction" of the acme threads holds
> the gantry in place while the EDM head moves across the PCB and the
> pulser removes 1 mil "dots" where there are no traces.  At the end of
> the traverse the gantry advances another 0.001" and EDM head then
> "etches" another line.  As I develop the system I'll probably follow
> your suggestion and match the traverse speed to the pulse rate, but
> for now -- Keep It Simple Stupid is the rule.
>
>> You said you regulate height to have the right current? What happens
>> if
>> the electrode is "done" and is not moved, will it enlarge the cut or
>> just stop because the gap is too large?
>
>
> The gap ( height ) is regulated by measuring the gap breakdown voltage
> as outlined in the power supply reference.  The EDM head is moved by a
> stepper and the software puts out a pulse if copper is to be removed.
>   At the end of the traverse the gantry is moved another 0.001" and
> the  EDM head returns while cutting the next line.
>
>
>> I understand the going line be line, a fixed width thing. But i don't
>> yet understand fully how you move along the line, or depth, and how
>> you "lift" the cutting over the traces. Plase clarify again.
>
> You don't lift the EDM head, you turn on the pulser and "burn" ( or
> "etch" ) the away the copper you don't want.  The height or z axis
> position of the electrode is controlled by the gap voltage.
>
>
>> Also, i think making ground planes would ensure faster cutting of the
>> overall board?
>
> See my comments about the HP plotter.  Since you can raster scan any
> image and output lines in the resolution of your choice you can move
> in increments of that resolution along the x axis without having to
> worry about the pulse return path.
>
>
> ST wrote:
>
>> I would really like making boards that way, i think.
>> what do you think the resolution would be?
>
> If I could grind a fine enough point on the electrode my stepper and
> leadscrew combo could "etch" 0.0001 inch dots ;D
>
> Doing double sided boards with SMT is a pleasure since the number of
> holes to be drilled is minimized.  You avoid all the mess and hassle
> of TT.  No board scubbing.  No etching ( or mist or titrating ). No
> paper residue.  Fine line widths and best of all minimal hole
> drilling!!!
>
> Curt
>
>
>
>
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