Insulation milling – tips and tricks

The design of electronic circuits up to the finished circuit board is also feasible for the hobby electronics technician today.
Then why isolating milling ??
Looking back on my first attempts as a teenager, I always remember the holes and stains in my clothes, the tedious creation of foils, my mother’s beating about the dirty stove, …….
And why not simply hire a service provider so that the designed circuit board is in the mailbox a few days later?

Good questions, to which I would like to give one or the other answer. And:
this is MY way and far from no rejection of the other possible procedures.

Insulation milling is the ideal solution for me because the results meet professional requirements and can be implemented right up to SMD techniques.
And the whole thing promptly, flexibly with quick correction options.

In addition to the actual board layout, drilling the necessary holes is also a challenge.
Ever tried to drill a 0.6mm hole exactly?

Or have you overlooked something in the layout and need to correct errors? Off to service and have the next board made, wait, hope that everything will fit in the second or third attempt?
To date, I have not succeeded in producing an error-free circuit and circuit board the first time, honestly !!

So when it comes to precision, CNC technology is also a very good alternative for hobbyists in general.

These are my arguments in favor of insulation milling.

And now for practical implementation to get flawless results:

1 a milling machine running absolutely flat on all levels
Here, of course, the mechanical structure plays an important role and was and is the reason why I got a trapezoidal spindle mill
I switched to one with ball screws.

1. 

   A dial gauge clamped in the tool holder is helpful to check the flatness of the X and Y axes.
   

   

   The maximum height difference for my milling machine was 0.01mm – so it was really good.
   2. a vacuum table that is “scheduled”
   Vacuum plates that are operated on a “normal” vacuum cleaner are extremely helpful, since the circuit board is fixed in place without using double-sided adhesive tape or clamping aids.
   

   

   But:
   Many vacuum tables / plates have to be milled flat again after the first clamping, because – especially with POM – the surface is not flat due to the manufacturing process.
   With a 3-tooth cutter of 6mm diameter and 30% coverage, this is quickly done.
   Then check again with the dial gauge.
   
   3. a adopting device for Europlatinen
   This is the trick with which I can finally get the insulation milling to reasonable results!
   With this clamping element, the vacuum table is practically extended in height.
   For this I took a 12mm piece of POM in the outer dimensions 200 x 150mm, and continued the grid of the vacuum table holes (10mm grid) 1: 1.
   In addition, 4 dowel pins are provided to always position the holder in the same place on the vacuum table.

2. 

   The decisive step is then to make a deepened bed of exactly 160 x 100mm with a 6mm face mill of approx. 3mm depth.
   Important: slightly extend the corners to be able to insert the board securely.
   After positioning this milled unit, the board can
   – always be stored the same (really on the 1 / 10mm)
   – can be used and milled on both sides by turning
   It is impressive with what precision the work parts come out of the holder !!
   

   

3. the correct milling tool:
   

   the actual insulation milling works best with an engraving tool of 30 degrees cutting edge and 0.1mm D. (LGS.30 from Sorotec).
   the feed should not be more than 600mm / min, then there are no burrs.
   Free milling – e.g. for high voltage technologies – takes place with 0.5 to 2.0 mm incisions. Here too, full speed and approx. 700mm / min. Feed.

   I am happy to provide the CAD data or the milling data. Then please send an email !!

   After years of experimenting with this technique, I have finally mastered insulation milling!