Summary

We replaced downlights recently with a smaller version. This could have meant plastering, painting and redrilling, but these spacers fill the larger hole and actually look quite classy in white on a white ceiling by adding another small dimension to the lights.

Instructions

The hole in the ceiling is 76mm, but these down lights only have a 80mm surround.
Therefore, I overlapped the surround by an extra 10mm and formed a recess in the surface for the surround to sit back into and retain a flush look.

This is the only tricky point, because to form this 3mm step facing downwards, I cut some thick cardboard and stuck a layer of the platform tape on one side of it.
I let the printer start the print off, and then just prior to the head about to move further into the centre, I paused the printer with the extruder out of the way and inserted my artificial support into the centre. Then I unpaused and let the build complete.
While waiting for the point to pause the printer, I left the cardboard disk on the suface of the platform out of the way with the tape down so that it also heated up. Then when paused, I flip the disk over so the hot tape side is upwards. As long as this spacer is close to being 3mm, it prints okay. It actually doesn't matter if the extrusion goes off a little the first time around, because once it does its first layer of fill, it solidifies it all up and if rough in appearance doesn't matter because its not seen anyway.

I used only 10% fill, extruder temp of 230C, and platform temp of 110C on my Replicator.

I admit I had a concern about heat. However, after running the lights fully on for two days, there has been no problems - no smell of warm ABS and no melting. Cool to touch. Its one reason I decided to print at 10% fill - so that there were large airpockets and reduced heat transfer.

Downlight spacer