Sunday, July 8, 2012

PVA coated print bed experiment

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

5 comments:

  1. Hi There

    Just wanted to ask if that is PLA or ABS. Most of the references to using PVA are for PLA. I can print PLA without any problems on my heated glass bed but I am still getting warping with ABS. My current method is ABS juice on mirror, that sticks well but objects that have ledges, such as the motor mount on gregs hinged extruder, will warp when the top cools but the bottom is still heated.

    Thanks
    3DIY Printing

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  2. Hi there, I was printing with PLA above. The PVA coating only helps PLA to stick. It doesn't work with ABS from what I read. I haven't printed in ABS yet. From what you describe it sounds like some further challenges are ahead for me!

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  3. Hi Guys,

    I just printed a big piece on a thinned PVA coating (50% water, 50% PVA). It worked perfectly. But now it is REALLY hard to tug away the piece from the glass. Is there a special technique? I tried spraying some water on the edges or scraping it off with a cutter's blade, but it isn't working very well. Any suggestions?

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  4. Were you printing to a heated surface? Has it cooled completely? Be sure it is cooled completely.
    If you were printing with a very low first layer and a 50:50 mix then it has probably sutck it too well. I diluted more than 5:50.
    How thick is your glass/mirror? There's a risk you may crack your galss as you try remove the print (be careful). How big's the print?
    If you can get a paint scraper under some corners it may begin to lift but I think now the concentrated solution and possibly low first layer and large area has stuck it well.
    My video above shows the type of force was applying. There's no special thechnique. Once compltely cold the parts snap off by hand.

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  5. Correction: Should say "I diluted more than 50:50" above.

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