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Thread: Evaluation of PolyMaker PolyCast(SP801C): A3D printer filament for investment casting

  1. #1

    Evaluation of PolyMaker PolyCast(SP801C): A3D printer filament for investment casting

    This is a reformatted version of my post on reddit

    TL;DR Album

    I recently got a roll of Polycast SP801C, which is a variant of the polysmooth resin(PVB), but it is tailored for investment casting metal parts. The special thing about this filament is it prints as easy as PLA, burns out clean(testing soon), and most of all, it can be smoothed/ dissolved with alcohol. I have also noticed that it cuts and sands like ABS, which is a nice change from PLA.

    I have been printing and smoothing the SP801C with good results so far.

    The diameter measured 1.75mm exact and is very circular(better than can be measured with calipers)
    The printing characteristics are great, nearly identical to PLA with very minor stringing, but excellent bridging, and support structure breaks away perfectly.
    I had some trouble with bed adhesion on glass coated with Mod Podge (PVA glue) at 45C but increasing the temperature to 60C with a 10mm brim, or 75C without a brim solved it for me. I've been running the hotend at 215C for the first layer and 205C for the print. My printer has a large 0.8mm e3D V6 nozzle because I typically print big and fast for functional parts, where layer lines aren't important; for the fine stuff, I switch back to the 0.4mm nozzle.

    I have tried smoothing the Polycast by putting the parts in a ziplock bag with a couple ml of isopropyl alcohol(IPA). I Inflate and seal the bag, then shake for about 10 minutes, until the parts look smooth. I let the parts dry on a piece of wire mesh for easy removal once hardened. This approach is a bit ham handed and Iv'e had IPA leak in to the model through an eroded gap and cause a temporary squishy spot. To be fair, my method probably erodes the model more than the official "polysher" would.

    On beefy 0.4mm layers it significantly reduces the layer lines, but they are still present as very shallow and gradual undulations. The surface has a nice high gloss, and scraping my fingernail over the layers does not produce the typical "zipp" noise of a normal print. Although it is not completely aesthetically smooth, this partial smoothing should be beneficial for the casting process, removing all of the sharp creases that normal layer lines have, which should reduce damage to the investment material, reducing inclusions in the castings.

    On normal 0.2mm layers the smoothing works completely, the layers merge into a smooth glossy surface.

    Benchy Smoothed print defects still show, but the surface is smooth

    3D scan bust smoothed

    Sprue tree smoothed

    Sprue tree closeup

    One additional benefit of the SP801C is being able to use IPA to solvent bond custom 3D printed sprues to the models. I printed some custom sprues that position the model accurately within the confined space available in the investment flask, and also form the pouring funnel after the plastic is burned out of the investment. Being able to print the sprues separately from the models allows each to be printed in their best orientation, sometimes eliminating the need for support.

    Benchy Sprue

    Sprue tree assembly

    I am hoping to Invest the parts this week, and burn-out then cast this weekend. I will provide another update after casting.

    Sprue tree and 3D scan next to flasks

  2. #2
    Moderator DavidF's Avatar
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    Ill be looking forward to seeing the casts.
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  3. #3
    Me too.

    This casting session will be the first time using:
    *Actual R&R Plasticast vs. 33:66 Plaster sand mix
    *Actual electric burnout furnace vs gently blasting it in the propane fired melting furnace for an hour till it stops flaming
    *Using a vacuum plate vs gravity feed

    David, your process and results have been a huge inspiration. Thanks!

  4. #4
    Moderator DavidF's Avatar
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    Thanks
    ....
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  5. #5
    Very nice evaluation!
    Can't wait to see the cast!
    I'm investigating 3d printing and ceramic shell casting, will definitely look into this PolySmooth (hadn't heard of it till now...) next to the moldlay filament (have you tried it before ?)

  6. #6
    I haven't tried moldlay, but I've been curious.
    I tried print2cast wax filament, but it was giving me trouble and I didn't get much time with it.
    As far as printing quality, so far polycast has been superb, but we'll see how well it burns out.

    I might get a roll of polysmooth(sister product) when it's released, just for printing, that's how nice this stuff prints.

    I don't have any XP with ceramic shell, but the Polymaker's demo video shows Polycast being used for ceramic shell casting stainless steel.

    Best of luck, I know some day I will go down the ceramic shell rabbit hole, especially since I have an electric furnace now.

  7. #7
    Can't wait to see your casts! Hope it burns out nicely!

  8. #8

    Wink Casting was a Succcess

    The castings where a success.

    Invested them using a vacuum chamber and a rickety drill press belted to the highest speed for vibration. Although, I did not have or use a debubbler, small surface bubbles where a problem. Next time I'll wash them in 5-15% antifreeze, which should approximate the SDS of some commercial recipes.
    All Invested low res.jpg

    Burn out could have went better. I followed the 8 hr R&R plasticast schedule, but I discovered that my furnace control was dead, and it just ran 100% on. I discovered this on the 300F water bake out, when I checked the temp and it was 520F. So for the rest of the burn out I manually turned it on an off to hit temps. luckily my furnace is slow to cool so it wasn't too bad.

    The plastic started to stink and char at ~600-700F
    700F Burnout starts low res.jpg

    At about ~800-900F it started to combust with a sooty acetylene like smoke.
    Burn out low Res.jpg
    At the end of the burn out there was some white wispy ash under the flasks that was easy to blow away. The surface of the sprue was bone white.

    For melting I used a #1 Crucible (PMC on Amazon) which is small enough to fit in a basic stacked IFB furnace (6 bricks) which melted my brass fittings in no time.
    fittings melt low res.jpg

    For casting I used a basic vacuum table for my solid wall flasks.
    Casting low res.jpg

    The castings came out great (for me). There were some black areas on some, so I think I will hold the burn out at 1350F longer next time. On the tree, the two rows closest to the pouring cup where short, but I think that was due to my tree layout(need a longer trunk) and vacuum limitations.
    as cast Tree Defects low res.jpg
    As Cast shake out low Res.jpg
    As Cast Benchy close up low res.jpg
    As Cast benchy and tree low res.jpg
    As Cast All mid res.jpg

    I buffed the boat and a couple coins.
    Polished Benchy Side low res.jpg
    Polished Benchy Back low Res.jpg
    polished coins low res.jpg

    Does any one have recommendations for getting these to look cleaner? (black buffing residue, residual investment and oxides in the hard to get areas)


    I am supper happy with the results. i think the next batch will be much improved.


    -Corey

  9. #9
    Quote Originally Posted by cmooney View Post
    Does any one have recommendations for getting these to look cleaner? (black buffing residue, residual investment and oxides in the hard to get areas)
    A combination of ph down (sodium bisulfate) and hydrogen peroxide has worked for me. It will etch your metal so don't leave it in too long.

  10. #10
    Moderator DavidF's Avatar
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    It looks like there was some residual ash in the molds still. If you light a bit of this filament on fire does it produce black smoke??
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

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