Re: Auto-Level a PCB ????
toggle quoted messageShow quoted text
>> My experience tells me that not all PCB material is of consistent thickness.
I have seen this mentioned several times so this morning I sat down with a micrometer and several different scraps of PCB material from cheap stuff to expensive Rogers HF board. Most of it is newer stuff but I do have some stock that was 20-year-old coated PCB stock that I dissolved the coating off so I could use it for mechanical etching (so it sat in a slight caustic cleaner for 24 hours or so.)
I made several measurements on each board and found less than 0.001” variance on every piece of PCB stock. I have never seen any PCB stock vary more than this. Then I wondered how much this 0.001” difference would really make to the width of the cut. Given a 60-degree V bit with a 0.005” tip and cutting 0.004” deep the DOC would be 0.0096”. A DOC of 0.003” would yield a DOC of 0.0085”. If you are using a shallower angle bit the difference would be less.
My point is not to pick a fight but to point out that unless you are getting the worst quality PCB stock in the world I don’t see how PCB thickness is making any real world difference. The three biggest problems I find when talking to folks are: 1) machine set up, 2) PCB stock hold down, 3) bit run out/poor quality bits. All of these things will still interfere with making good PCBs even if you use something like the auto-leveler software. I’m not making an argument against using auto-leveling software rather I’m saying it is the last in a line of things you should look at.
To give you an example. When I started engraving the end panels on my control boxes I would on occasion have one where the engraving depth would vary noticeably. The end panels are pre-punched to shape and I have a special fixture to hold the stock flat. This puzzled me for a while as I was certain the thickness of the material was consistent over the 4”x10” stock size. What I finally discovered was that while I was deburring the bottom edges of the stock the rounded corners, which looked fine, had small burrs that would lift the edge of the stock very slightly. Now I deburr all four corners and the engraving comes out fine.
Maybe this will be of some help?
From: pcb-gcode@... [mailto:pcb-gcode@...]
Sent: Sunday, December 13, 2015 9:55 AM
Subject: Re: [pcb-gcode] Auto-Level a PCB ????