Some filament based investment casting success

Discussion in 'Lost PLA casting' started by measuretwice, Sep 1, 2022.

  1. measuretwice

    measuretwice Copper

    Lots going on in my casting trials, months of effort setting up and mastering (cleanly and with no odor) SLA printing. Still have some challenges with getting a decent print that will correctly burn out, not cost an arm and leg and will burn out a temp low enough that the investment can handle it, but I am close to success there (after many fails).

    Not PLA, but as its filament printed, seem the logical spot....while, I did the following casting from a filament print the other day. I've concluded the Print2Cast filament is just garbage. It burns out beautifully but it is impossible to achieve good bed adhesion and bottom inevitably peels up and warps. I had some success with a paper weight dog my son and I cast, but it wasn't a mechanical item so a slightly warped bottom didn't matter. If someone has the silver bullet for that material, I'm all ears

    What I found works fantastically is Polycast filament. Probably the easily and best filament I've printed with and it burns out prefect.

    The story in photos

    I tried everything with Print2Cast. With each I tried several times with different bed temps, enclosure/no enclosure etc (had to make the bloody enclosure of course)....this whole process was very frustrating. No matter what I tried, printers PEI heated bed (which which is excellent for most everything else), painters tape, PET tape, hair spray (even imported a special one someone recommended that was suppose to have the right combination of chemicals, what BS), FR4, another supposed miracle solution and glue stick. I even tried emery cloth thinking it might possibly form a mechanical bond. No matter what, it would peel and distort

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    Everytime, it lifts and gets distorted bottom surface like this...

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    Then I thought an enclosure might help....so I made one, and tried it all again. (hey, no comments on the looks, its "experimental" :) )

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    I'm afraid I have to admit defeat on this awful material. Grrrr.

    Then I tried Polycast by Polymaker, the storm clouds parted and golden rays of sunshine entered my basement. This stuff prints and burns out like a dream. The only issue with it is is that its extremely moisture sensitive. To the extent that it will pull moisture from the air and crack and pop as it goes through the hot extruder and the moisture boils. I avoid all issues by running a dehumidifier at its lowest setting (30%) with the door to the room closed. Polycast calls for 20% RH, but there was not issue with 30%.

    In addition, its surface can be smoothed with exposure to alcohol mist (IPA not Glenmorangie, its the Print2Cast material you need that kind of alcohol for). That holds potential but I didn't bother....their mister seems a bit silly and expensive, I may try to make one but but haven't got there yet)

    I get a great print from it

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    You need sticky wax (made in myself, rosin and beeswax) to get it stick to a wax sprue

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    and fills my largest flask!

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    investment mixed, poured and ready for vacuuming. I'm eliminating sources of error where ever possible; investment mixing carefully done, weight and temps.

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    My casting set up has a number of improvements since the initial cast last December. I made the vent system which temporarily fits in a window (you can't believe how the house stunk after a 3D wax print burnout with a vent). The pick up sits above the oven just the right amount (the goals being 1) get all the fumes coming out of the oven, 2) don't create a draw through the oven and 3) pull in enough room temp air that the vent stays cool)

    I also placed the oven on some pieces of small angle iron, it creates a heat break between it and the vent.

    I used a cheapo pid with a USB connection (thermomart). While the software and instructions are probably the worst mankind has ever seen, truly remarkable, its still about 1,000,000 times better than keying in segments 4 button key pad. The PID industry is, for some reason, stuck in the late 1970's electronics interface wise.

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    This isn't the actual flask, but the story would be a lunch bag let down without the obligatory red hot burnout shot.

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    After the pour (flask is in the vacuum caster which sucks the metal through out the cavity). Notice the cracks in the investment. This I think is my fault. You are suppose to to start the burn out cycle, about 16 hours, two hours after pouring the investment. Life got in the way and instead it sat for a week, a no-no.

    Casting was done with the AL at 735C and the mold at 400C


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    The moment of truth is nigh! The flask is allowed to cool for 15-20 minutes and will still over boiling temperature is plunged into water. The boiling break up the investment

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    ....and did it work? Mostly, fairly well. A few issues, but a workable part. It was a huge effort to make it this far, and while there is still room for improvement, it is quite a thrill to go from computer screen to cast metal part in one's basement. Its a part that would be extremely difficult to make other with investment (cores needed...and where would you part it) which adds to the fun; new possibilities

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    There is a lot porosity in one spot. Glad to hear causes and what might fix it. The AL was melted in one of cheapo electric melters.

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    and the investment cracks lead to some flash (that 3 minutes of fettling took care of)

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    And what the heck is it? A bracket to support table that will let me use the horizontal bandsaw as a vertical band saw

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  2. crazybillybob

    crazybillybob Silver Banner Member

    If you're going to do much printing with this type of filament you might want to check out something like this Spool Enclosure I picked one up for nylon it pulls moisture bad too on the recommendation of another 3d guy I know. I haven't printed any nylon since i picked up (moving) so I can't speak to firsthand experience. But I've had some good luck with a plastic box and desiccant packs. This is just a higher tech version of that. With the cost of these special casting filaments to not lose a print over moisture it might pay for it's self the first spool.

    (I don't work for amazon or the mfg of the product in the link. I don't get any kind of kickback, etc. Just sharing the knowledge. )
     
  3. Rocketman

    Rocketman Silver

    That's a good looking casting, well done. What kind of investment are you using? I would very much like to try investing 3d prints but I don't know what kind of investment to use nor do I have a kiln.

    Also of note, on the first filament you tried - the picture you posted shows a very poor "squish" on the first layer. The nozzle is too high off the bed. This will cause a lot of adhesion issues. Is that is something you played with during your testing?
     
  4. Ted Brown

    Ted Brown Copper

    I also tried the print2cast filament and feel like it was interesting, but does not give a nice object like polycast. I was going to do lost PLA (polycast), but had to get an oven, etc. I am trying my hand at lost foam, but I still like the looks of my polycast printed stuff.
     
  5. measuretwice

    measuretwice Copper

    Thanks, 15 year old R&R Ultravest. I know they claim its got a one year shelf, but I was told if kept dry its fine. I think the 12 month is from the sales not engineering :) It seems to work well. I did try some brand new R&R plasticast to solve a resin casting problem, but it made no difference. The dog below my son and I cast last year using the identical process and aged investment and it perfectly replicated the pattern with no porosity

    Two things I did wrong on the bracket above, letting the mold sit for week and the other thing I'm pretty sure I did wrong, was I left the vacuum running for quite a while after pouring. I wonder if its vibration caused the porosity/nodular appearance shown in the close up above?

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    I did not, it would be worth doing a test on.

    Were you able to get good bed adhesion? do tell! :)
     
    Last edited: Sep 14, 2022
  6. ddmckee54

    ddmckee54 Silver

    Plus 1 for getting the nozzle closer to the bed on the first layer like rocketman1 said. In addition to that, I normally over-extrude on the first layer - anywhere from 105% to 110%. You'll know when things are printing right because the top of the filament that print head is laying down will be flattened, not rounded.

    If I'm having problems with bed adhesion, the first thing I do is clean the print bed with isopropyl alcohol. If that doesn't do the trick, then I get out the Elmer's glue stick and hit the areas where I'm having trouble... Then I usually have problems getting the print OFF the print bed.

    Don't be afraid to abort the print if the first layer doesn't look right. If that first layer isn't
    good then the rest of the print won't be either.

    Don
     
    Tops likes this.
  7. Billy Elmore

    Billy Elmore Silver

    I have had similar issue when filament gets opened and not used within a week or so. I had to go well above temp rating on bed to get it to stop curling up on the ends like that and to stay on build plate. Bed temp range was 80 to 90 but got warpage...went to 105 and couldnt get it off the build plate without a lot of effort and no curling or warping. I try to use 30% speed on first layer at 75% to 90% layer height and 150% to 200% layer width. I have some things I have had to go up to 115F on bed temp to make it stick and not curl...usually thin points. I would play around with first layer and bed temps on some small objects until you find the sweet spot. Try long thin parts to maximize the warp or curling effect on the part.
     
  8. measuretwice

    measuretwice Copper

    Interesting....and that was the Print2cast filament?
     
  9. Billy Elmore

    Billy Elmore Silver

    That has been my experience with virtually every filament I have used except for one oddball that I found actually curled away from the heat and turning the heat down on the bed to just about ambient temp was best. try small long pieces to save time and play with cranking the bed heat up.
     
  10. ddmckee54

    ddmckee54 Silver

    Billy:

    The bed temperatures you listed earlier; those are all in degrees F, and not degrees C - correct?

    Don
     
  11. Billy Elmore

    Billy Elmore Silver

    Nope...totally missed that...they would be Celcius...sorry!
     
  12. measuretwice

    measuretwice Copper

    Its worth a try, but my issue is with Print2cast, miserable awful stuff, not 3D printing in general. I've lost a lot of motivation to bother anymore that filament and consider it basically garbage after using the Polycast material as shown above. It was just so easy and worked perfectly.
     
  13. Billy Elmore

    Billy Elmore Silver

    Some of it is just bad right out of the bag. I use ColorFabb HTC for our gating here and it usually prints nicely but have had one or two rolls that would break constantly (too brittle) or warp horribly straight out of the bag. I bought some of the dryer boxes to help extend the filament life but have not really seen that much improvement since using them. I am currently struggling with a dual print job where one roll is a week older than the other and the older one will warp off of the build plate while the other is perfect. Little frustrating that the older one has barely been used and is already giving me a fit. I slowed the first layer down to 15% speed and increased the layer width to 200% from 150% and increased the temp by 5 degrees Celsius. Hopefully it will stay on this time. They like to warp up and pop off the build plate while I am on lunch or working on something different.LOL
     
  14. Billy Elmore

    Billy Elmore Silver

    Forgot to mention that location on the build plate can cause warpage as well depending on how the build plate is made. The one I use definitely is hotter near the elements so if I get warp on one piece and not the rest it can sometimes just need to be moved to a new location away from the heater elements. Turning off or slowing down the cooling fan will also help with warpage. The two parts I am printing are at the moment behaving and showing no warpage after the changes I made. I am watching it though...it usually only misbehaves when Im not looking.LOL
     

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