There was a recent suggestion on the forum from Enlightx that a coating of diluted PVA (50:50), painted on to the print bed would aid adhesion of the printed object, preventing warping or even breakaway. The suggestion was echoed and tried by Rich on his blog. I gave it a go, diluting to a ratio of 1:8. At this point I've been using it for over a week, printing each evening. Here's some feedback on the experiment.
It brushes on easily and dries to a foggy finish. I left it overnight, then put it back on the printer. You could probably paint it directly while on your printer and dry it with your heated bed.
I printed my first few pieces to this newly coated surface with what I now think was too low a layer height, causing it to bond too well to the surface. As the week went on I got more brave and raised the first layer height until it was just a light touch to the surface. Here's a short video that shows how well the printed piece adheres to the newly coated surface. Even when cold I had to apply some significant force to remove the piece.
You can see the fogged mirror surface in this photo below, and an object that printed without budging. I printed many objects for the week, large and small, and there was no warping what so ever.
The underside shows no ill effects from the PVA (photo below). The first layer infill seems to loop slightly short of the perimeter in the photo. It looks fine in solid layers further up the print. I may have set the first layer too high in this case, preventing the first layer squeezing out to the perimeter.
Conclusion: The dilute PVA coating has a positive effect on print bonding to the print bed. I'd recommend starting with a more dilute solution, perhaps 1:20, and add more coats if that doesn't improve bonding.
If you have been in the habit of running a very low first layer then you can certainly back that off. Too low a first layer will result in the piece being very difficult to remove from the print bed (as in my short video).
Be careful when tugging pieces from the glass as the glass could crack rather than the piece give way.
The shadow of previously printed pieces remains in the PVA coating. It will be interesting to see if this impacts on the finish surface of subsequent prints.
Finally, it will be interesting to see if the adhesion benefit will diminish significantly over time. If it does then it seems that a fresh coat of dilute PVA would be cheap and easy to re-apply.
Thanks for viewing!
NumberSix
