I first tried ABS onto double sided copper clad FR4 taped to a bed at 120°C. The ABS stuck well enough to extrude the first layer of a 20mm square, but when it cooled down it had no adhesion at all.
PLA at 55°C did exactly the same, but PLA at 130°C stuck very well, so well in fact that I can't get it off with my fingers (the blob was where I aborted the print after the first layer).
Maybe ABS would stick in the same way at an even higher temperature, but maybe not as it is less like glue than PLA. The 120°C / 55°C temperatures are what I use for Kapton, which is why I used them as the starting point.
An interesting aside: I had to measure the PCB to work out the z-height. It is only 1.4mm thick, whereas a standard PCB is 1.6mm. You can also see the grains in the FR4 showing through the copper. This means the board I bought in Maplin for home PCB use is actually the same stock material that they use for the first part of a commercial production process, but when they plate thorough the vias they increase the thickness of the copper all over to get the standard 1oz/inch2. I don't know if this is always the case, i.e, that all home made PCBs have less copper than a production one, or whether you can get bare board with 1oz on it already.Anyway a good result, assuming PLA will resist PCB etchant. Also, it seemed like a potential bed technique. I.e. do the first layer onto hot copper and then cool it to about 50°C for the rest of the object. I tried it with this butterfly: -
It worked perfectly. After the first layer I blew it with a fan to cool it down to 50°C. It took about four layers to get down to that temperature. Since I added the insulation under the bed it takes longer to cool it than it does to heat it.
After it had finished and cooled down to 40°C it was still firmly attached, so I removed it by flexing the PCB.
The base of the object is perfectly flat.
I think for PLA this might be a better technique than Kapton. I can't imagine the PCB wearing out. It could also be self heating with a serpentine track on the other side. I don't know that just taping it down would be strong enough for making large objects. I could solder fastenings on the back if not.
I don't know if there is anything special about copper and PLA, or whether other hot metals and plastic would work . I tried similar things with ABS on AL, but may not have had it hot enough.