Ball Hopper Monitor - Casting Project

[petertha]

I bought a 3D printer 2 weeks ago! (Bambu A1). Aside from the recent 'controversy' of Bambu Labs, I'm having fun learning this technology & prototyping my own stuff. Specific to some of the finishing discussion in this thread, I'm also intending to print male shapes to yield female molds, predominantly for small composites molds. I made a visit to an auto finishing supply store. I saw some familiar 1K spot putty brands I used in the past. I think they are generically similar but decided to get this one to try (and slightly lower cost/gram). Including some preliminary pics. The prints are 0.4mm nozzle using standard PLA. No special settings, I'm still a rank Novice.

The glazing putty behaved exactly how I remember these products working in the past. It is very creamy, easy & predictable to apply. Left is a single swipe of putty on what was the textured heated plate using a cardboard business card (not even a proper credit card haha). You can see it did a pretty nice job filling the valleys.. Next is a typical flat print 3DP pattern, single swipe of putty filling the print striations. The thickness is just me feathering & I think I gave it a couple rubs with 150# at this point trying to stop just short of the mountain tops. Next, the disc, I should have taken before picture. It was a rather uglier, heavier stair step striations around the conical surface because of print orientation & its shape. And it had a noticeable nozzle start/stop seam you can just make out. The white underneath was a spray of shelf inventory Tamiya rattle can primer used on plastic models, just messing around. The heavier coat of putty bonded to the primer fine. The primer was insufficient build thickness to fill striation valleys. It would have required several spray + sand coats. I'm confident after some light conformance sanding of this putty coat, it would be ready for primer with few blemishes or visible print, but I'll return to that soon.

The putty is non-catalyzed (1K) so there is a bit of dry time, but it also does not have a strong odor of typical 'Bondo'; polyester based filler (at least to my burned out nostrils). On some other samples I tried to scratch & peel it off the print. It can be done but it puts up a fight. So next stage after sanding (for composites molds) would be spray primer, sand, gloss paint & buff. But I would think for casting purposes one could get off the train a few stops earlier with just putty + primer + minimal sanding. Hope the visuals help, keep up the good work!

https://mail.carworx.net/shared_files/catalog/fichiers/kombifillereng.pdf

https://www.autobodytoolmart.com/product/usc-pronto-kombi-spot-putty-32046/auto-body-putty-glaze

 

[GreenTwin]

Looks like your skim coat is about the right thickness.
That is a pretty good filler method in my opinion.

I have not forgot about the BHM; the gas tank patterns are next to me on my desk.
I have had a very large work project come back alive again, and so that is taking up all of my time.
Deadlines and commitments; story of my life......

I really can't deal long term with the fumes of the auto fillers, and spray paints.
I can see where in some cases that would work out pretty well.
Watch out for the fumes though; they have some pretty ominous warnings on the label.

Spraying on the filler slurry was a good exercise to go through as far as learning how to use an airbrush, but in the end, it is not what I consider a very viable method.

I am going to stick with an initial cleanup of 3D prints using the slow speed sanding sponge, and then just build up coats of shellac.
The shellac has a pretty fast drying time, and so can be recoated more than once per day.

The weather has been bad lately, and so no way to do molding or foundry work at the moment anyway.
The gas tank pattern halves need a little sanding, and then they will be ready to be used to make permanent aluminum patterns.
.