Hi All,

I am having a bit of a challenge that I hope one of you here may be able to help with - I'd appreciate your assistance

As it is I need to make a copper plate with a thickness of 1.5 mm COMPLETELY flat/level, i.e that the difference in thickness across the copper plate (~100mm x 100mm size) is no more than 1/100mm. Additionally, the copper plate is to be entirely level/flat - again differences of no more than 1/100mm from one end to the other. BTW although I'm aiming at 1/100 mm precision I'd actually prefer if it can be done even better ...

I've tried milling a 2mm copper plate on my CNC (which does ~5/1000 mm in an area of this size) down to 1.5 mm - fastening it with double adhesive tape and some "steering bolts" to prevent it from moving on the tape - but the copper "curves" or bends ever so slightly so that it is no longer flat.

I am now considering other solutions like e.g. a vacuum board but I reckon that even if the copper plate may be kept entirely flat during the milling process then the internal tensions inside the copper plate will make it go back to a non-level/flat condition as soon as the vacuum hold-down is released.

I am also considering sanding the copper plate with different grit size sand papers and a light weight so as to not bend the copper plate during the sanding process.

However, I was thinking that maybe one of you have already had a similar challenge - and might know how this is best done ... if this is so I'd appreciate your feedback.

Cheers & thanks for any inputs here

Jesper