Homebrew PCBs

For those that CNC mill their own PC boards I know there is autolevelling software out there to control the engraving depth, but I was wondering if the spring loaded engraving bit holders work instead of going through the whole process of probing the board etc. I can imagine having the holder run over the swarf would cause problems with the height but if you keep everything very clean as you go, don't these devices work? Is there something else making their use undesirable?

Sage

Mark,

If the spacer is threaded it could just be given a slight turn to adjust the depth.  There could be either thread friction or a clamping collar to keep it from rotating.

Bertho

 

From: Mark

  I’ve been wondering how to make a spring loaded spindle with depth adjustment that can fit in that Morse tapered tool holder of my CNC machine since it doesn’t have a spring loaded motor/spindle.  

Making a spring loaded engraving bit holder is easy.  Making the depth spacer that’s easily adjusted is the problem!

 Cheers,

Mark

I finally found the Ad for the spring loaded engraving tool I was referring
to. Claims it can engrave curved and uneven surfaces. But I guess I was
wrong. By the looks of it there really isn't any depth control as such. Just
that it can generally follow a surface.

http://www.2linc.com/spring_loaded_engraving_tool.htm

 

This design could easily be improved for PCB milling by modifying it to
where the engraving bit has a fixed stickout from a ball shaped spring
loaded nose of the tool. The one shown in the link might even work if the
engraving bit can be set back in the collett to a few thou stick out. The
nose could then press down on the surface of the PCB material. Seems like it
should work except for the driving over the swarf problem. Maybe I should
design one.

 

Thoughts

 

Sage

Seems like what I described is available from the company I linked to in my
last post. I just didn't look far enough in the site. Great minds think
alike I guess.

So, has anyone tried one of these for milling PCB's?

 

http://www.2linc.com/engraving_depth_overview.htm

 

Sage

Seems like Highway robbery to me. 
$350 US for one piece is more than I am willing to pay for such a simple tool.

Jean-Paul
AC9GH

On Jun 28, 2014, at 8:52 AM, 'Dave Sage' davesage12@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> 
> Seems like what I described is available from the company I linked to in my last post. I just didn't look far enough in the site. Great minds think alike I guess.
> 
> So, has anyone tried one of these for milling PCB's?
> 
>  
> 
> http://www.2linc.com/engraving_depth_overview.htm
> 
>  
> 
> Sage
> 
> 
>

As for "Why bother" I wasn't looking for a smart ass answer. It was a simple
question if anyone had used one and their experiences with it.

But to answer that question. It would eliminate Z backlash issues that would
be a problem for accurate probing. It would eliminate issues with the board
changing it's shape once you start milling it (due to stress relief) and
eliminates the step of probing itself. All of which may not be problems at
all. Assuming running over swarf isn't a problem then it guarantees the
depth of cut regardless of what the board is doing. Sort like how a
thickness planer works so well on a piece of wood.

 

As for the price. I wouldn't by one for that price either but it would be a
simple enough item to make (for me).

 

I just thought it was an interesting approach. It  might have a whole bunch
of problems of it's own that I might like to hear about.

 

Sage

Thanks for the link.

Looks good but it appears in this design that the depth nosepiece rotates with the engraving tool.  It could get pretty hot from friction in a high speed spindle and melt, or simply wear away on the sharp edges of the tracks and the abrasive fibreglass swarf.  Maybe I'll try a similar design for ball bearings on the nose so it doesn't have to rotate.

I guess the one without the depth control relies on the cutting speed to limit the cut depth, especially as they are designed for very hard materials like glass and granite.

Cheers,
Mark

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Saturday, 28 June 2014 10:53 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: Spring loaded Engraving bit holders




Seems like what I described is available from the company I linked to in my last post. I just didn't look far enough in the site. Great minds think alike I guess.
So, has anyone tried one of these for milling PCB's?

http://www.2linc.com/engraving_depth_overview.htm

Sage