3D Print to Metal Casting. Higher Level Lost PLA Casting Experiments.

[@FarmCraft101]

Hope you found the video entertaining and helpful! If you like it, please consider sharing the video on your social media feeds. Also like and comment. Trying to grow the channel, and your support means a lot! Thank you!!!

[@wantafastz28]

Check out Robinson foundry on KZbin. He has amazing detail out of his pla prints

[@jaffabeast]

I’ve seen great success with ceramic shell casting using fine wire as a kind of rebar. They wound it round after the second coat.

[@georgethompson8834]

Have you considered adding fly ash to your investment and ceramic shell casting that works for you best as it might help with improving the detail in your casting?

[@tedsykora1858]

As someone that has done many dental castings , here are some suggestions. 1. Wet the pattern with soapy water (we call that debubblizer)and then dry it to help the water based investment "wet" the pattern ( water does not want to wet plastic). The investment will flow onto the pattern better. 2. Vibrate the pattern as you paint the investment onto the debubblized pattern and then vibrate the casting ring as you fill it.

[@SwarmerBees]

Was going to suggest vibration after watching, but you beat me to it.

[@Adman234videos]

Good video! I've also spent some time experimenting with lost PLA and lost wax and here are my 2 cents. Let me know if you have any questions. 1. You learned by the end that the part orientation is very important. I don't think the horizontal orientation would work very well because the metal cannot fill properly as it will trap air bubbles and break apart... I was happy to see you got a good result with the vertical orientation at the end of the video and I think that was crucial. Always make sure you have your fill at the bottom and your vent at the very top. 2. Like you mentioned, a real crucible (not a tin can) helps a lot. I've found that stainless steel at least 1/16" thick is best as it doesn't oxidize and flake apart which can allow the plaster to move. Keeping the plaster contained will prevent it from cracking. 3. For larger castings, you can add boric acid to the investment to stiffen it. This will absolutely work and prevent it from cracking even with quite large castings, but the downside is that the demolding becomes a lot more tedious as the plaster hardens like a rock and is difficult to chip away from the part. You can find the ratio to use online. 4. It seems your 3D printer is underextruding a bit which is leaving that fragile pattern that the plaster fills into. You should run some calibration parts for this, usually single wall thickness works. You can also use an SLA printer with special wax-like resin for ultra detail, which I've used for jewelry. The machines are only about $200. 5. A bit of windex spray added to the plaster can act as a detergent (?) and prevent the bubbles from forming around the letters. I'm not sure how much it helps but it seems to reduce the tendency to form these bubbles. 6. I've tried pressure casting like you did but with steam and never had good results. You can instead pull a vaccuum on the bottom of the flask which is what I do. Using a sheet of graphite on top of high temp silicone on top of an aluminum manifold hooked up to my vaccum pump works well for me, without spending lots on a fancy casting table. 7. (EDIT): I also use a burnout kiln with a raspberry pi controller to precisely ramp the temp during drying/burnout to prevent cracking. This is very important.

[@kentklapstein9879]

Thank you for the tips! I am about to attempt a large investment cast, 10”x10”x5” flask, 1liter part volume. I am going to use vacuum during the pour. My biggest concern was cracking the plaster during the burnout. I put together a pid ramp controller, check out Andy’s Machines video and patreon. Would adding stainless steel needles, made for refractory, help to keep the mold from cracking? After seeing how these expensive investments behave on large scale I am considering plaster of Paris with boric acid and a touch of refractory, I don’t mind chipping it out of the part, I DO mind spending $$$ on crumbled investment….

[@arrgh406]

@@kentklapstein9879 Did it work?

[@kentklapstein9879]

@@arrgh406 It worked very well, I used SC20 investment from Randolph and Ransom. The investment was perfect, no cracks or leaks. I didn't add anything to the investment, just followed the instructions. The detail on the print was great. I'll be doing more soon. Smaller items this time.

[@jorgenava1726]

El yedo fraguado contiene una cantidad minima de agua,la cual se debe sacar pues el agua al gasificar sumenta 900 veces de volumen,es preciso poner un calentamiento r bajito,para prevenir la fractura del molde. Una proporcion de 70,por ciento de agua combinado con un 30 de glicerina,obtiene moldes capaz de grabar una huella digital.A,esta mezcla se la añade unas gotas de jugo de limón el cual retarda el fraguado del yeso. Un molde hecho de hule comun de vulcanizar,se imprime una figura y despues del vulcanizado se ahoga en petroleo,el molde se incha y crece un 500 por ciento,despues con parafina liquida obtenemos una copia 500 veces más grande a un costo infimo.

[@Nderak]

once again killing it with the tshirt game

[@alexrex20]

i have absolutely zero desire to get into this type of hobby but i LOVE watching your vids. keep it up.

[@poguedil]

I think you need to spray some water and soap mixture on your mold to reduce the surface tension before you put your plaster in. By doing this your plaster will flow better against your mold producing a better detail molds.

[@Mikewgoogle537]

Polymaker is made for investment casting . Leaves no ash .

[@zedchannel]

I found adding sand into the plaster mix reduces the cracking of the plaster a lot. I usually add twice the amount of sand as I do plaster. Plaster is unstable during the burnout but sand is completely inert. It makes the mix more porous which allows the steam to escape the plaster mix as it heats without cracking your mould. I just use regular play sand. It doesn't effect the detail of the casting either.

[@sierraecho884]

I think what you could do is, use just a small amount of plaster to cover the top surface details and then mix 1:1 ratio sand with plaster to fill in the rest. You should also probably burn out the plaster for longer to absolutely make sure there is no water trapped.

[@ZPositive]

CitriCal! Blast from the past. Paul Harvey used to advertise for CitriCal. I can still hear his voice saying the word.

[@Zpajro]

always a pleasure when you upload a video

[@mrquicky]

This was an excellent sequel. I like the investigation into the internal of the mold after loss casting. The most entertaining part of the video, was watching the vacuum chamber happening before the mold pour. I'm thinking it should occur after the mold is poured, not before.

[@FarmCraft101]

I've tried that several times and not had good luck. I think air sucks out of the PLA pattern and by that time the plaster is more firm, causing problems.

[@mrquicky]

@@FarmCraft101 Having ruminated on this a bit, I think the fill pattern should be changed. www.instructables.com/3D-Printing-Make-Water-Tight-and-Air-Tight-Contain/

[@Dsdcain]

I really enjoyed this quite a bit. I did learn one major thing. You sir are extremely patient to keep at this. Talented as well. Thanks for sharing these videos. 😎

[@seanktb.]

some stuff i've seen help in the past with the printing pattern in the plaster is sanding the print itself before casting

[@timothylongblacksmithing6743]

That t-shirt is great

[@andrewlarsen9700]

One thing you might try to get rid of the 3-D print layers. Is to put them in an acetone vapor chamber. This will smooth over most of the print lines.

[@andrewlarsen9700]

DIY perks did a nice video on it

[@kentklapstein9879]

Does acetone work on PLA? I didn’t think it behaves the same way ABS does….. I am going to try smoothing / sealing the PLA with wax.

[@eccentrickiwicreative2962]

Hi, a number of people use chopped fiberglass strands to reinforce the plaster. Personally I find it a bit of a pain. I had some luck by getting ceramic fiber paper, adding water, then blending and then adding the resulting mush to the plaster mix. The fibres seem effeive in reinfcing the plaster.

[@archangel20031]

At Master Carr you can buy raw material and you can get thick walled pipe in short sections, sold by the foot, just drill out your holes and weld on end cap which was the two crossbars.

[@Henrik.Yngvesson]

Just want to share my experience from a bit different application that you might want to try. I did some differential hardening of Japanese style blades many years ago and had many issues with the clay cracking and falling off the blades when heated. Then I added a little borax to the clay mix and that made all the difference. I preheated it in the kitchen oven to dry it through before heating it in the forge. And after the preheat it got a slight glassy feel to it like if the borax where melting into the clay and made it more ductile while hot.

[@honthirty_]

Ok, file this idea away for BlackSmithing.

[@Bear049]

Maybe it was not crosshatching from the print but rather brush strokes from the brush you used while the casting material was wet. The brush brings small air bubbles and the hair left voids? Just a thought

[@aaronrose186]

I use a 50/50 mix of ordinary plaster of paris and sand, pore into a metal can and turn upside down to burn out the pla so it drips out on its own before burning off......heat slowly in the kiln to avoid cracks

[@johnnybagofdoughnuts4193]

This is a very fun series

[@walterchamberlain9052]

Just spitballing a couple of thoughts (I've never done this type of casting with these types of materials): Thicker walls on the flasks might help; the investment material and the plastic and the metal and the flask all have different rates of expansion and contraction - you might be able to find an investment material that is more conducive to these things; have you tried burning out at a slightly lower temperature for a longer time? Possibly this would counter-act the rapid expansion/contraction and (possibly) help with the cracking problem. As I said, I'm not an expert at all, it's just some thoughts that came to me. Great video!

[@elizotte]

So what might help with PLA is rather than doing a conventional burnout to have the mold be upside down and only bring it up to 450 at first, letting the pla go soft enough to drain out somewhat. The plaster already has its final shape at this point and staying below 500 for the beginning doesn't cause the chemical change to the plaster of breaking the water molecules off. Then after you've gotten a bit of the pla out, you can take it up to full burn out temp. Or possibly try casting it, as the metal should burn the remaining thin layer of pla off and if you have good vents it might work

[@FarmCraft101]

Good thoughts. I do heat it up slowly to 400 over several hours and hold it to allow the plastic to drip out before going to higher temps.

[@elizotte]

@@FarmCraft101 you can get it to 250 fast, let it sit an hour and bring it up to 450ish as fast as you want after that. Figure that 400f is only 204 c so that might be a little low as well to get good flow outward

[@sinformant]

My father worked at an investment casting company. I used to have the name of the investment casting ceramic they used. I know there they would use molds to cast the parts out of a casting wax that they later burned out. The shells were several layers of ceramic slurry dusted with silica sand after each wet coat. You may be better off printing a 2 part mold of the item you want to make and then making wax copies to put in the plaster that you burn out.

[@brendonhowe2158]

Hey dude do you happen to have the investment casting ceramic slurry that he used? I have been looking to source some to NZ but no luck without crazy shipping costs! Any advice would be appreciated. Thank you

[@sinformant]

@@brendonhowe2158 ill have to ask him

[@brendonhowe2158]

@@sinformant If you could that would be awesome thank you. Or is there a DIY option since NZ sucks in general when it comes to specialist items. I don't want a slurry which needs to be stirred 24/7 as that seems impossible for a DIYer like myself.

[@benjaminsteakley]

So leave slits for air flow in objects like the d and Os, cast it on its side like you did for more aluminum pressure. The sprue placement must have helped with air flow leaving as metal comes in. you could do the bottom fill and the vent at the too method. I liked the rectangle housing. try vibrating before setting process. Let your metal cool before putting into water. make the details potrude from the face more.

[@dannyberne]

If you think that the print is expanding too much, try printing with the coin rotated in the x or y axis by 45 degrees... It's not a magic number or anything, but I think the problem is that you are printing flat on the bed when it comes to it being too solid. There would be a lot of support material with it rotated, but you probably have 1 or 2 non-solid infill layers as it is. Printing with it wonkey will just leave you with almost all walls, and little solid layers. I have noticed printing in that orientation will increase your surface details and reduce stringing on the surface. Maybe hit it with clear coat to seal it. And yes, it does take forever to find out if it's good or not If that is the same color change pla I use, excellent choice. That stuff is good beyond it changing color

[@jasonflt]

Welcome back

[@joshuahuman1]

One thing you could try if the pla expanding is causing the cracking you could try dissolving it instead like abs and acetone or polymaker makes a filament called polysmooth that dissolves in alcohol maybe even pva it might hold up in the moisture long enough for the plaster to set

[@johnnykirk1501]

I got dap plaster of paris, hopinf it works well cuz its more like that ultracal that you use, its super hard so rubbing fingers on it doesnt destroy the small details, but i have yet to put it in the smelter to fire it, i dont have any other way of melting the wax out, but i was gonna do it without an extra container, glad i watched this first cuz id have probably had an accident and spilled the metal.

[@johnnykirk1501]

Also should probably invest in a mask, i had been being careful to not breath around the powder but who knows how effective that actually is.

[@kevinmartin7760]

Pressurizing while the plaster sets shrinks the bubbles by a factor proportional to the absolute pressure. Thus if you pressurize at 20PSI which is 20PSI "gauge", or 20PSI above atmospheric, or 35PSI absolute, the bubbles will shrink to 15/35 or about 43% of their original size which is not really much of a reduction at all. Also, unless the pressurized air can diffuse out of the mould before or during firing, it acts as an force trying to expand and crack the plaster. Applying, then releasing, vacuum before the plaster sets causes the existing air bubbles to either expand and break off completely, or to be replaced by bubbles of water vapour, which condense to essentially nothing when the vacuum is released. I'm not sure how the air trapped in the 3D print's infill affects all the vacuum/pressure. It may depend on whether the skin of the 3D print leaks. It is almost certain to have a few leaks, but it may also be the case the the entire skin is leaky all over.

[@bigstackD]

Always interesting to watch my friend👊🏻😁🍻 that double cylindrical mould at the end is pretty cool .

[@FarmCraft101]

Thanks bigstack!

[@Gideon_gains]

Tshirt is right up my street 👍

[@xyzero1682]

Yeah that CSC seemed the way to go. Great videos!

[@mmo5042]

also, since you recycle metal the way you do for the casts, could impurities/hidden reactions have influenced the quality of the casts?

[@jerrywhidby.]

I feel like I saw a video where a surfactant like Dawn was sprayed on the surface before pouring the plaster. I believe it helped the bubbles release from the surface.

[@lazydragonslayer]

I've known about and loved your channel for years. Didn't realize I wasn't subscribed. My mistake.

[@benbencom]

The cracking makes sense to me. If your mold is about 125mm across, 68um/m/K expansion of PLA means your mold goes from room temp to glass transition temp and gets about 0.5mm bigger inside a fully rigid plaster mold. Only above the glass transition temp can the PLA start to flow and "get out of its own way" and even then it won't be molten until it expands even more. I wonder if large items would work better printed out of a soluble material (PVA in water, or ABS in acetone) so you could remove most of the material before the burnout

[@JJW]

Hallo! Could a single plaster of Paris mould be used to cast aluminium multiple times..I want to use a single mould to make something in large numbers

[@davidbarnes5953]

could you use: Resin 3D Printers 3D printing in extremely high-detail is what the 3D printers in this collection were made for. Whether it is for dental applications, castable jewelry designs, prototype 3D printing and more, this group of 3D printers is capable of incredibly detailed 3D prints. With resolutions of only 25x50x50 microns, 3D prints come out looking lifelike without the need for post-processing. Using various resins, 3D prints can be firm, flexible, soft or incredibly tough for almost any application under the sun.

[@beefan1596]

You can - they even make special burnout resins that are meant to make it easier to melt it all out. The channel Vogman has more lost resin videos. Both resin and PLA casting have their upsides and downsides, of course.

[@159asmos]

try reducing the infill. maybe have no infill, make it hollow, and use the support material function. this should let it collapse inward when expanding.

[@mynameismynameis666]

vacuuming is one part, the other is vibrating the mold before it settles to mitigate the movement of bubbles from suspension

[@uncoolsticcboi]

i use drywall joint compound onto very thin walled pla printed models and i dont even have to burn the plastic out, i never have cracking issues my main issue in my 2 small tests so far was simply that my brass cooled too quickly to completely fill my mold. i didnt have any gates or sprues or vents etc. i literally just coated my part and then mae a hole in the coating to pour into. my next test i will use slightly higher melt temp + a riser because i could see on my test part where the detail was better towards the bottom and i tihnk its just the weight of the molten metal.

[@michaelhenderson7739]

I’ve been thinking about using printed parts to cast and have a dumb question. What’s wrong with just using the part/object you print and pouring the molten metal directly onto it? Does the PLA not melt or not melt completely?

[@wvcruffler123]

What’s up doc! Looks like a lot of fun. I’m going to order a roll of the machinable wax for my projects (casting flintlock lock parts). Great info on the different investment plasters that you used. Cheers.

[@TheKickassK]

Same. I need to cast left handed parts

[@clarkstevens2711]

You could try putting some sand in the plaster what should help with the cracking

[@yanceyalsup7682]

You could try to smooth the print with an isopropyl alcohol vapor chamber to cut down on the print lines.

[@1992jamo]

You put the mixture in a vacuum which is cool, but could the mould itself fit in the vacuum chamber after you've poured the plaster? I'd be surprised if pouring doesn't trap air EDIT: Ignore me, I got to 10:15 now where you've tried exactly that.

[@jonathanbrocklehurst6724]

Could putting the casting on a lazy Susan and spinning it help. Centrifugal force is quite potent

[@James-W6WOF]

Thanks for sharing. I had a question about your robinair vacuum. Will it pull down to -30 or better? Thanks.

[@H4zuZazu]

Maybe: 3D print into Silicone molding -> then Casting Wax and then that into Plaster

[@Boosted98gsx]

Yea, this is the typical method. Make a master parent "negative" that you can then pour investment wax into for part replication.

[@farmerboy916]

It seems like you might lose significant definition that way, and be open to introducing errors? But of course can replicate it much easier

[@H4zuZazu]

@@farmerboy916 But you can correct the Wax template easier than the PLA one

[@W4TRI_Ronny]

3:50 What value do you vac this to? I have a pressure kettle I plan on using and I want to get the right vac pump. Thanks!

[@FarmCraft101]

Very close to full vacuum.

[@Mike-mm6jp]

i wonder if no infil and use the function "ironing" in the slicer to smooth out the skin would help

[@noviceartisan]

Some kind of vacuum when pouring might help too?

[@Phil_Fras]

Is it possible to dissolve the pla in acid instad of burning it out?

[@spud4ever290]

Moroso makes a ceramic block sealer (to seal cracks in auto engine blocks -) which (when fired to hi-temp -) should be ideal for sealing cracks in your investment molds .

[@kentklapstein9879]

I believe this sealer is “water glass”, sodium silicate, also used as a binder for sand casting, this would certainly be an appropriate material to use, not sure how it could seal up cracks in a mold after firing out the PLA without changing the shape of what is being cast.

[@nigelolympia]

Is it ash from the pla that is causing the fill in the letters? Blow out with air maybe?

[@DoRC]

I'm guessing The reason you're seeing much taller ridges on the inside of the mold is that the plaster is soaking into the cracks in the PLA

[@SmithDrewSmith]

Do you remember the burnout cycle you used? That has a significant impact on the durability of the prestige oro

[@WDZaphod]

Whats about printing the item with low to zero infill, as few outer shell layers a possible, and then burning it out with the molten metal? When the molt goes in from the bottom, and there is an air vent on top, it might smoke like hell, but evaporate all the PLA?

[@thomasesr]

Wax also expands when heating, that's why they use wax in wax linear motors. It produces a lot of force.

[@sinformant]

They make wax specifically for investment casting that doesnt expand and also burns out clean.

[@FarmCraft101]

True, but I am guessing that wax is easier on the mold than PLA. As the wax heats, it will soften, and since it has a place to exit, it shouldn't build lots of pressure. PLA would do the same, but wouldn't soften until the temp is higher. This is just a guess on my part. I may be wrong.

[@bryancunningham1095]

Not sure how much time you allow for the phosphor copper reaction because of your editing but when you had an image of the bag with the phosphor copper shot I though it said leave it in a minute or so, I counted much less time than that on your first pour for the video.

[@Opinaca]

Hi, I really love your videos. Don't know if it can help you, but just watched another guy video who uses Ultra-vest investment...but he also mentioned to pour hollow mold instead of solid ones.

[@richardgracews6]

Thanks for great content!

[@Watchyn_Yarwood]

Many books have been written about what I don't know about metal casting! I did stumble across a channel by the Veg Oil Guy who seems to have this process down pretty good. Might give him a watch or two.

[@sierraecho884]

I don´t understand what is the pressure pot supposed to do ? Usually you do that to get rid of bubbles but you already have vacuume degased your plaster so wjhat´s the point ? Also you ddin´t seem to have any problems with bubbles anyway.

[@bullzebub]

is it possible to do a extremely low infill and skip the burnout process?

[@abdeljalilpr2033]

Can you do experiments to see the flux effects on castings?

[@Behr-hammer]

Why did you VC it before pouring? I always pulled my vacuum after pouring and it's the way to go I think

[@Sam-y5o6j]

Great video

[@فاروقحجام]

Do you heat gypsum before pouring?

[@WalterBurton]

Fired it up! Thanks, man. Great videos. 🌲🌳🌲

[@carlduey390]

This is good but have you thought of standing the cions straight up ?

[@mmo5042]

have you tried casting a wax from the print and then metal from the wax?

[@jerrywhidby.]

Have you tried to let them set longer to push out all of the moisture?

[@bulletproofpepper2]

Thanks for sharing!!!

[@VeezyLife]

thanks for the tips! btw, theres no link where you pointed to and said would be a link lol u maybe forgot? just letting you know

[@matthewklumper1248]

I can't tell, but are you baking your plaster molds before firing them? You need to remove the moisture before firing it to a high temp.

[@charitybrown4274]

Great Video!! 👍

[@kiiiisu]

this stuff is really interesting!

[@nerdsmith_uk]

Thanks for trying to use pressure, I get the impression that 60psi is a good starting point for epoxy applications. I wonder if the prestige oro is plaster of paris based, as that goes the same way (delicate and friable) when you heat it. The ultracal looks like it properly cures, but also expands as well which is why it cracks like that - something I don't think plaster of paris does as badly

[@FarmCraft101]

I like the idea of pressure, but I think for 3d prints, 60PSI will crush your pattern.

[@nerdsmith_uk]

@@FarmCraft101 yeah, I'm wondering if you can somehow perforate the model to allow pressure in to balance it - it only needs to form the cavity for the investment so the infill could be non-sealing (gyroid?) With bleed holes where the spout and the two halves join

[@andrewbaker234]

I love your vids Thanks!!

[@ronnybe7994]

Very interesting Somewhat chaotic

[@sidneyking11]

I need a aluminum bracket made. Are you in US and can you cast a bracket for me?

[@matt_1984_]

what's the life of a crucible? IE how many pours, and is there a way or even a reason to get all the slag off/out of the crucible?

[@FarmCraft101]

Properly cared for the crucibles last a long time. At least 20-30 pours. I try to clean the crucibles out some, but there is always more slag.

[@gonsolop2429]

I got a tip for farmcraft101: Mix into the plaster the red shavings they use to clean concrete floors. The stuff they sprinkle on a concrete floor & sweep by hand using a push broom. Your molds won't crack & they'll last a long time. ( In between college classes I had looked up an art professor to ask him how to make strong, durable molds to cast lead & pewter. Looking back, I didn't know to ask him two part mold or onetime mold. I was thinking like a top mold half & bottom mold half, strength, & durability. Anyway he gave me this tip & I had no cell phone back then. Once online I could not find this industrial cleaner. Amazon & Etsy were not around back then. Sometime later some smartypsnts latchkey kid slipped into my home & stole all 2 lbs of my lead & pewter bits & nearly cleaned out my kits into ruin. I really hope he/ she rots in a cell some day. 🤬 ) Anyway, I will never be able to use this great tip from a master ring maker. Best regards.

[@alext8828]

At around 6:30, you made pour with no vent. Is that the way it's done?

[@FarmCraft101]

It had a vent. Not very obvious with all the cracks in that mold. With sandcasting vents can be optional, but they are necessary with investment plaster.

[@alext8828]

@@FarmCraft101 Sorry. It was 5:41. I guess it was out of the shot.

[@dragonpug1452]

ive only recently gotten into metal casting, i havent been able to properly cast things yet, (waiting on shipping) so take what im about to say with a teaspoon of salt, i think sandcasting might be the move for this stuff, and im curious as to why you arent doing that instead, but again thats just from what ive seen other people do online, and maybe im incredibly wrong.

[@Jkauppa]

try constrained freedom electroplating molding, with like copper source in copper sulphate

[@Jkauppa]

its very low temperature metal structure, maybe light weight, porous, mass growth, incremental

[@Jkauppa]

similar to casting, but no high temp needed, just electricity in a suitable bath, fitting with the source metal, just have a seed, like wood that can be burned away, also wood mold casting

[@Jkauppa]

burned wood carbon mold infill plating

[@Jkauppa]

etch the details, electro-etching, reverse of the electro-plating

[@Jkauppa]

carbonized paper electro-plating, controlled low oxygen environment, for graphenesuper cap electrodes

[@honthirty_]

At 12:44 on back side of the Doge, the center of the D fell off. That would be "lost Detail".

[@nicktohzyu]

what does the phosphor do in the alloy?

[@FarmCraft101]

Deoxidizes, prevents porosity, and makes the metal more fluid, so it fills molds better.

[@moretimethanmoney8611]

I'm surprised your investments aren't firing out any better than plain old plaster. Are you firing your molds the same day that you pour them? Try waiting longer. If you allow your form to equalize to atmospheric moisture and temperature and bring it up to temp slowly, you may see a lot less cracking. The drawback is it takes forever. Also, if you limit the burnout heat to just what is needed to burn out the PLA, the bonding constituent in the plaster may not be cooked to its pre bonding state (similar to the lyme cycle). Lastly, the heat expansion rate of the PLA is greater than that of the investment, so you'll always get cracking on larger molds no matter what you do. They don't have that issue with lost wax (that many investments are designed for) because wax gets to melting right away without much expansion. They do make a wax PLA filament for this reason. A fine sand casting would suit best with that two sided shape.

[@holden_hh]

Technically the plaster is hard, not tough. The harder something is the more brittle and shatter prone it is, like diamond or hardened steel, the tougher something is the more malleable it, an it won’t crack or shatter like. A good example would be a glass cup and a plastic bottle, the glass is hard and the plastic is tough.

[@ddd-pq4vs]

I dont understand: Why did you create a lost form and not forms with 2 halfs for the coins?

[@nedyah151]

It’s not air bubbles it’s residue from pla not burning out completely. Ash or plastic stuck a the bottom

[@luther99flame]

I'm only halfway through the video... I was going to say that if you are losing definition between the print and the cast you could try pre-wetting the print before pouring the cast material on it (theory being that the liquid can get in all the gaps and not trap air first and then its easier for the cast material to wick in to the gaps). The cracks in the mould after you pull them out of the firing are alarming to me, there must be information on the net as to how to solve this issue - maybe the firing profile is wrong, or maybe you'd need to do a two stage fire. The use of the expensive casting material could be overcome in the same way they do it with the sand or silicone moulding, by using one to capture the detail and then an outer layer of a space filler (expensive material where it counts and bulk it out with something cheap).

[@luther99flame]

and now I'm watching the Ceramic Shell Casting video and that seem like a much better method (only 3 minutes in). Where you cured the ceramic by heating it up slowly in the furnace to allow the plastic to room to expand, was that the same way you did it on this video (I don't think you covered that detail here)?

[@FarmCraft101]

Yes, I fired them the same way. Forgot to mention it in the video.

[@cbecht]

Commenting for the algorithm.

[@DC_DC_DC_DC]

Hey question, why don't you ever pour in a pre heated mould?

[@FarmCraft101]

Actually I almost always pour into preheated mold. I guess my fault for not explaining it well. I set the cameras up to catch the pour, and don't both to film taking the molds out of the kiln.

[@DC_DC_DC_DC]

@@FarmCraft101 ah okay! I guess it's also not possible to see with these. But with the ceramic ones I didn't notice a glow

[@pm9939]

Your plaster cracks because too much water in your mix and too thick of a pour. Make the first part like a paste and press it in, then you can make a thinner batch to pour around the first and to fill up your mold.

[@mrbumcraic5046]

Less water in your plaster will lessen the cracking, as little water as possible to get your detail

[@hazlox]

Did you ever try adding sand to the plaster? To keep it from cracking?

[@FarmCraft101]

I did. Didn't help me.

[@hazlox]

@@FarmCraft101 weird. I’m a potter/maker with a clay studio. Have you tried the ceramic shell casting yet? I want to try it with my 3D printer too. Love your channel!