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Thanks to Those That Went Before

I’m starting by thanking Matt Berggren for his excellent post on how an experienced miller approaches and uses the Othermill.  His post made me feel like I was his apprentice.

While I am at it, as I wrote this post I went through support responses provided by Simone at Othermill.  Simone provided exceptional support.  She really knows the details of using an Othermill and is blessed with the ability of exceptional communication skills and understanding.  Thank you.

Updates on Techniques

Pumped up with my previous success milling a pH BoB, I boldly moved on to milling an EC BoB.

After a day of getting to Gerbers and the Othermill carving away for hours on end, I FAILED to make a usable board.  

EC BoB from Othermill

I attribute the reason to the failure to not vacuuming up the remnants of previous runs.  This caused the FR1 not to be as securely taped to the base plate as it should be.  Also, it is much more difficult to get a good track when all copper is removed from around the track.  So what is a better way?  I went back to an excellent post on milling on the Othermill done by Matt Berggren.

These are the “tips and tricks” I have been learning through more time using the Othermill.

Set the Trace Clearance to Larger than the Default

Up until now, my experience using BoBs I made with the Othermill favored setting the trace clearance at a large value (e.g.: 2 in) so that all the extra copper is removed.  I discussed increasing the trace clearance  in this post.  Search for bit breaker 🙂 .  When I used the default trace clearance, I was getting copper traces connected that shouldn’t be.  Then I reread Matt’s post and am finding better luck setting a trace clearance of 0.055in.  The BoB looks more like what Matt did:

MattsPCBOthermill

 

 Put Less on a BoB

Another challenge I have is due to my (lack of) skill level.  I was having a low level of success milling chips that had spacing of 10 mils – the smallest spacing recommended.  Either the copper was torn, or I could not reflow the chip successfully on what was chiseled out.  I plan to get better at this, but for now I broke up the prototype such that some of the chips – and all that have 10 mill spacing between pads – are broken out onto SMT -> DIP adapters.

MosfetDIP

 I had bought a bunch of different sizes when I first started using this technique in order to use the same chip I use on the PCB to prototype on a breadboard.

Constantly Check if Mill bit is Broken

A big cost of using an Othermill is constantly feeding it mill bits.  I find it all too easy to break mill bits up to 1/8”.  The other challenge is being able to look at a 1/100” drill bit and seeing that it is broken.  Even under magnification there are times when I just can’t tell.  I bet this is due to my skill level.  Thus I assume my ability to see that the 1/100” mill bit is broken will become more obvious.

Have a Supply of Mill Bits on Hand

I wanted to try mill bits other than those offered on the Othermill web site.  I decided to by 1/32” 1/100” and 1/8” from 
Think & Tinker, LTD (see Pricebits.com

I ended up buying three each of:

  • EM3E8-0100-15V
  • MN208-0313-006F
  • MN208-1250-019F
I haven’t received these yet.  If I was to order again, I would go with Matt’s recommendation and instead of buying 1/8” – which I was using to remove all unused copper – I would have bought a 1/64” with the trace clearance set at .055”.

Always vacuum Out the Dust

The FR1 sheet needs to be as fitted as possible.  The first picture shows the results when I didn’t vacuum out before starting a run.

 

 

That’s it for now.  I wanted to document additions to my list of Othermill “what works for me”.  Perhaps these tips will be useful for you.

 

 

Thanks for reading this far.  Please find many things to smile about.

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