plans to fabricate a robotic arm or APC for a desktop homemade CNC mill

Hi,

Does anyone have, or know where to find plans to fabricate a robotic
arm or automatic pallet changer (APC) for a homemade CNC mill? What I
hope to do is this:
1. desktop CNC mill engrave on wood
2. robotic arm unload wood or APC1 move out to make way for APC2
3. robotic arm load new wood or APC2 move into desktop CNC mill
4. desktop CNC mill engrave on new workpiece
5. process 1-4 repeated.

If this is too difficult to fabricate, where can one purchase them?

Thanks

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