Using Bondo to finish PLA prints.

[Dan Steele]

Bondo adheres quite well to PLA as well.  It's also close enough to the same density that it sands quite nicely together.  I've found bondo great thus far for filling in cracks and fixing seams.  It kicks at room temperature so you don't have to worry about it melting the PLA and primer sticks to it with the same easy consistency as to the PLA itself.

If you're new to Bondo a few quick tips:

  *Start with mixing small batches it kicks fairly rapidly (2 minutes ish)
  *Once it starts getting tacky stop touching it and wait for it to dry.
  *Apply multiple small coats instead of one big one, applying more is far easier than sanding.

Advantages:
  *Bondo is pretty cheap.
  *It cures fast.
  *It sands and takes prime well.
  *It's designed and made for filling small cracks.
  *It bonds really well to PLA (I haven't tried it with ABS).

Downsides:
  *It cures almost too fast (Pot life is about 2 minutes)
  *It stinks (Use it outside).
  *Once you've used it you will have to paint the whole thing to make it look nice.
  *There's a learning curve to using it correctly.

At any rate for the price (I think I paid 16$ for 1L) it's certainly worth trying out, so far it's the best material I've found for finishing PLA prints for casting.

Dan.

[broncosis]

have you tried the thinner bondo I used to call it icing or runny bondo it is thinner meant for top coats save a little sanding

Bondo uses mekp as a hardener so I am not surprised that it sticks good and being polyester based I should hold up good

I am sure I have some runny stuff I can Give you at the meeting if you want to try it out uses the same hardener

also 2 mins seams fast you can mix it slower and then warm it after to make it harden up quicker

I have worked with bondo and fiber glass lots
if I can help just ask

[Miststlkr]

"glazing and spot putty" might be an easier option for most.   It comes pre-mixed in a toothpaste tube and is also a Bondo brand product

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[broncosis]

glazing putty may not bond as well but I am sure I have off that as well though it may not be as useable but lots of good stuff to test

[Miststlkr]

once my printer is up I can try the putty on a print if nobody does before then.    I have a good bit of practice with 'glass and bondo so I was thinking along these lines already.

On Mon, Jul 8, 2013 at 11:51 AM, broncosis <bron...@gmail.com> wrote:

 glazing  putty  may  not  bond  as well  but I  am  sure I have  off  that  as well  though  it  may  not  be  as  useable  but  lots  of  good stuff  to  test

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[Dan Steele]

I won't be at a meeting for a bit so I'll just pick some of the thinner bondo up, sounds like it would definitely help.  I've started experimenting with using less hardening, I suspect the temp outside right now is a large part of why it's hardening up so quick on me.

A large part of what I'm doing now is experimenting with different techniques for applying the bondo to make it easier to finish in less steps.  Because I'm making master for molds finish time isn't super critical, but if I could cut a bit of sanding out of the process it would be nice.

Dan.

[Dan Steele]

For anyone who's going to try this out quick dry grey primer is worth it's weight in gold.  It dries in 10 minutes and if you apply a thin coat after sanding it highlights all the imperfections you've missed.

Dan.

[broncosis]

I wonder if high build primer would be enough

Dan high build primer might be harder to find but it is a primer with a light filling compound in it I wonder if a couple of coats of that would be enough hmm time to call my old paint supplier

Hmm my mind is going all my old custom fiber glass work skills being put to use

[Miststlkr]

High build is definitely worth a try, good thought.  Would we need an etching primer for PLA, you think?

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[Dan Steele]

Right now I'm using plain old Rust-o-leum quick dry and it adheres very well.  I've been meaning to try out an Enamel based primer as they are thicker, just haven't gotten around to it...Also want to be careful not to soften the sharp edges of the print too much, there's a balance there...of course they can always be re sharpened by sanding after the fact I suppose.

broncosis I'll take a look around for high build primer and if I can get my hands on some I'll give it a go.

Dan.

[Miststlkr]

Walmart sells high-build in the automotive section.   not the best price but if you just want one can to try it out that is likely the easiest place to try

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[broncosis]

one can will go a ways unless your doing huge prints