Which end mill to level my acrylic bed?

[HankMcSpank]

Hank,
if you cover the postage costs I'll have a look at it for free. Its always good to have a favour in reserve:naughty:

Ian

Hi Ian,

That's very gracious of you ...when it went bang, I went to change the fuse but my lathe's fuse holder disintegrated (so I can't even try it since the large bang) ...let me at least order a replacement 32mm chassis fuse holder up & fit it, dry the control box out (very damp in my workshop) , visually inspect the pcb (it's too parky to go up in my loft & do all this right now!), if still no go, then I'll gladly pay the P&P for you to look at the board....many thanks.


Meanwhile, back to my "getting some FR4 copper board to mill evenly will be the death of me" saga ......so after spending SEVENTEEN QUID on a fly cutter, turning it down to fit in my CNC spindle, then setting it off on a bed levelling exercise...imagine my excitement/anticipationat mill my first 'bed levelled' pcb .....sigh, EPIC FAIL!

I have the V cutter cut depth (final depth) set to about 0.2mm ....I saw perfect isolation as the cutter did it's thing on the left hand side of the board...then alas as the spindle traversed slowly 80mm over to the right...I saw the tell tale sign of the isolation route getting thinner & thinner....then the track disappeared altogether! Of course what this means is that my machine's bed (thankfully acrylic atop of the ali bed & therefore expendable) is about 0.3mm lower on the right hand side of the bed vs the left hand side.

So then the penny dropped (I think)....if my fly cutter is only cutting on one side of it's travel 9the right hand side) ....then I need to take the cutter all the way past my bed's left hand extremity ...and then some, to ensure the fly cutter cuts it ....my bed levelling g-code obviously assumes that the cutter cuts evenly around its full rotation.

So now I have an unlevel bed - the only way I can think to rescue this situation is to use something like 6mm endmill & run that on a levelling routine ....at least the Z plane being out of tram shouldn't impact that too much....once my bed is level with the 6mm endmill, then the fly cutter back on to try & get my Z plane into tram....sound like a plan? (if so, can anyone lend me a 6mm endmill?!!!)

re pcb milling, thankfully, I now have a USB-CNC hardware card on its way to me, which will at last (hopefully) allow me to mill even pcbs with an uneven bed, this just in from the program's author (who I pestered to death to get this implemented).....

http://www.youtube.com/watch?v=0jGY92S8bxM (thankfully, my bed isn't as warped as his demo!)