Test with preprinted support for PETG models with overhang

I needed to print mechanical parts of PETG with an overhang. I was not satisfied about the standard support option. The printed support of PETG is difficult to remove and resulted in a sagged 'roof' and surfaces that needed too much grinding.

So I tested succesfully the use of preprinted-support (PLA and PETG). The trick is to use spacers and glue.

Print instructions

-Print the support with 1 mm less height of PLA or PETG.
-Print some extra spacers. For this test I needed the 0.8 mm spacer. Use the Height Range Modifier in Prusa slicer to tune the layer height to fit the height of the spacers. (For example I print with a standard layer height of 0.3 mm and a first layer height of 0.2 mm. To get a height of 0.7 mm, I change the layer height to 0.2 mm from a height of 0.5 mm till 0.7 mm).
-Put glue on the top of the pre-printed support, so the PETG will stick on it. I used two layers with drying in between.
-Set the settings for the PETG print with Support Material/ Contact Z Distance on 0 (soluble).
-Use Support Blockers or Support-from-build-plate-only so no support is printed under the overhang.
-Print the PETG model with overhang with a stop (color change) at the first layer of the overhang.
-Optional: Use the Height Range Modifier in Prusa slicer to tune the layer height near the 'inner surfaces' to fit the height of your design. (For example I print with a standard layer height of 0.3 mm and a first layer height of 0.2 mm. To get a height of 10 mm, I change the layer height to 0.2 mm from a height of 9.8 mm till 10.0 mm).
-Optional: set the print speed of the 'overhang layer' to 20 mm/s and set the layer height the same as the 'first layer height'.
-Use the pauze/stop to insert the spacers and the preprinted PLA support. Play with spacers height untill the top of the PETG and the preprinted support is leveled/flush. Use preprinted spacers and pieces of paper.
-(Wish for prusa slicer: can a option be added to park the extruder behind the print? And can the Y axis be blocked during a pauze of the print?)
-Secure the preprinted support with tape.
-continue the print.
-place the finished print in water to resolve the glue. Leave it quit a few hours to let the glue get soaked.

My test print was a succes.

The benefits are:

1. The quality of all the surfaces is smooth.
2. The height between the overhang is closer to the designed height and at least not less, so:
3. no more grinding needed, so less work, but also less change for heat-deformation during grinding.
4. Pre printed support can be re-used. So this saves support material and time to print supports in case of a series. But when PLA is soaked in water, needed to resolve the glue, it will deform.
5. No PVA-HT needed, so no duo-nozzle-printer needed.

See this discussion on the forum too:
https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/insert-a-pla-printed-part-during-the-print-to-function-as-support-material-for-petg/#post-254284