Let's analyze the problem:
- We have a 5.5 mm total thickness.
- We want to (semi)permanently affix the two layers together mechanically.
- The clips shall not be higher than about 0.2 mm to allow the nozzle to pass over them.
(non)Solution attempt zero:
Let's look at the problem objectively... we can print something, can we? Well... 0.2 mm or below of PLA means 0.2mm of PLA that need to withstand the stress of trying to push the glass to the bed. PLA, just like any plastic, isn't super strong in thin layers, especially when heated to 60°C to get a good bed adhesion. And then you might want to print something like ABS, which demands an 80°C or higher bed temperature. The result will not be pretty: either the clip breaks after a very short time or it starts to bend. The result: no clip, bed slipping free.
Solution attempt one:
Let's look at old picture frames that consist of just a glass sheet and a paper/wood backing. A "Frameless Picture Frame" like this one1. These clips do need some kind of mounting on the underside.
Using this design as a base, you might either get these clips or make similar ones yourself. But how to mount them?
Well, here comes the nice part: we got some options.
- Glue or solder the clips to the underside of the bed. Removing the sheet gets a PITA, but is still possible
- Cutting mounting slots for the clips. The sheet can be removed by removing the clips now. But the bed heating might not like us cutting slots into the aluminium.
- Adding a mounting point. Again, we can use glue or solder to add some kind of framework that we mount the clips to. Like a piece of aluminium U-profile with the opening to the centre of the bed, giving us mounting points for the clips.
1 - This was just the first one that I found that had the right setup. I am not affiliated with them and don't get money for this.
Solution attempt two:
Take this idea up a notch and look for this same principle applied.
There is the "Swiss Made Glass Retaining Clip" Perplexed Dipole mentioned. Good idea, and instead of having to cut a notch into the aluminium bed, a simple, small hole would be sufficient. About the same price than a frameless picture frame but less construction work!
And then there is, of course, the option to look at the Ultimaker and its Build Plate Clamps like 0scar mentioned. If you can get them (also in the same price range as the other options) you even might have an easy installation: they are supposed to be mounted in the corners of the build plate by being held by the springs. For the A8, you'll have to possibly adjust the mounting point some, maybe even give them a little nub to pivot around to secure them in place, but this clearly is a solution too.