Lost 3D print Resins?

[creast]

Hi all,
I have been doing lost PLA casting for a few years now and have found the standard PLA has proved quite adequate for my needs and have not needed to move to special 'castable' filament.
I am now embarking on a new adventure into 3D resin printing and considering lost resin casting as the end result and as you may guess am horrified by the prices for 'castable' resins.
To save some time doing trials I was hoping someone may have tried the basic resins in this manner and how successful were their results.
Can anybody help?
Cheers
Rich

 

[GreenTwin]

Are you burning out the PLA, and then casting, or pouring molten metal on top of PLA ?

.

 

[creast]

Hey Pat,
Thought you would know me by now.
Always burn out PLA in proper investment plaster.
Rich

 

[GreenTwin]

Hey Rich, sorry about that.
I follow basically everybody in the world that does backyard casting work, and so it gets all jumbled.

I have not paid too much attention (yet) to resin printing, and so I am not familiar with the differences between something like PLA and whatever the resin is.

I was also told that the special clean-burnout filament was needed for lost filament, but then somebody made some really nice castings with lost PLA, and so I think you may be correct about not needing something special for lost resin.

However, there is a guy who does a lot of lost foam on ytube in aluminum with pretty good results, and so another guy decided to try lost foam with gray iron, and it turned into a huge bubbly blob of metal.

So after all that, I can't answer your question, but am interested in your new process.

Can you add some links to your casting stuff in your signature?

.

 

[GreenTwin]

Gear pump on grabcad.
Now I remember.

And some great work shown here:

https://www.homemodelenginemachinist.com/threads/question-about-lost-pla-casting.35014/
.

 

[creast]

Gear pump on grabcad.
Now I remember.

And some great work shown here:

https://www.homemodelenginemachinist.com/threads/question-about-lost-pla-casting.35014/
.

We had quite a lengthy conversation during my 1/8 Rider Ericsson casting project too

 

[GreenTwin]

My memory is like the Energizer Bunny.............going, going, going.............
Old age is heck, as they say.....

What did you say your name was..... (just kidding).

.
Edit:
Its all coming back now, but the question is "How long will it stay?".

 

[GreenTwin]

This video is cool, and I don't recall even seeing it.

That is the good thing about losing your memory, you can be entertained over and over again by exactly the same videos.

.

 

[GreenTwin]

This is a nice pressure nozzle setup.
I vaguely recall this one.
Diesel is a very good option for backyard casting in my opinion.

 

[GreenTwin]

This casting turned out well.
Nice Myford in the background.

 

[creast]

Ha ha. I know what you mean about the memory issue
No worries.

 

[jirvin_4505]

Have not done it yet
Lots of YouTube’s available when you start searching wax like resins

I think it’s Vogman that did a ring with details of a bubble bee. Absolutely stunning presentation

I was keen on lost pla but after seeing what detail the 3D resin people are getting I’m in awe



Cheers Jeff

 

[GreenTwin]

A lot seems to hinge on how smooth you can 3D print something.

With a very smooth finish, there are several ways to get a good casting, depending on what you want to set up for.

The investment casting method seems to lend itself to multi-part tree assemblies, and parts that are on the smaller side.

I have seem some folks make some large investment castings, and they seem to struggle a bit with investment cracking during the process, but create some impressive large castings, with "large" being perhaps 12"-24" long.

And the investment method also lends itself to very irregular shapes that can't be easily withdrawn from a typical sand mold.

It will be interesting to see where the lost PLA/resin thing goes.
I am trying to look forward to what the possibilities in the end may be, but that picture is not clear yet.

In the end, I guess it boils down to dollars per pound of metal cast, and if the results are of the quality you want/need.

From a bound sand perspective, sodium silicate is much cheaper as a binder than resin, but resin binder is more controllable in my opinion with the set time being controlled by catalyst.

Since I am not set up for the investment process, I am interested in the recent lost PLA method where the PLA is burned out of a bound mold, perhaps at a low temperature (am I remembering that correctly?).

.

 

[ddmckee54]

Foketry seems to get reasonable results with his Lost PLA plaster/sand mix process that he uses in his "18 Cylinders Isotta Fraschini (straight six-cylinder x3 )" thread in the Work in Progress forum.
He starts casting at about Post #120-ish, and uses that process to cast the crankcase and several other parts.

 

[GreenTwin]

18 Cylinders Isotta Fraschini (straight six-cylinder x3 )​

Link is here.
I know I saw this because I commented on it, but sadly I have no recall of seeing it.
So I get to read it like it was a new thread, so that is the plus side.

https://www.homemodelenginemachinis...aschini-straight-six-cylinder-x3.34220/page-6
Edit:
A very noble casting effort in aluminum and bronze.
The bronze looks pretty good.

There are things he could do to improve his aluminum castings a lot.

.

 

[ddmckee54]

There are things he could do to improve his aluminum castings a lot.

Agreed, but as you say, a noble effort.

I believe that the "ceramic" he uses for the initial coating is actually a casting plaster that is not intended for a burnout cycle. I'm just starting to get things set up to where I can cast small parts. Working on a burnout oven now, so I'm still just arm-chair quarterbacking. Eventually I'd like to try modifying his procedure by using investment plaster for the initial coating to see if that would help the surface finish on lost PLA.

 

[GreenTwin]

A few mistakes that I have made in the past that I suspect are some of his issues are overheating the aluminum melt, and letting it sit while at pour temperature.
This causes all sorts of gas problems and gas bubbles.

I pour immediately at 1350F, and I don't really need to degas, since I don't let the melt sit at pour temperature and absorb whatever.

I see what looks like bifilm defects.
The stream of aluminum into the mold should be smooth and laminar, since the molten metal front creates a skin on its outsides as it flows into the mold.
If the metal stream is full of abrupt directional changes, and high velocity, then the skin gets churned into the metal, and creates those large bubble-like features.

You have to control the metal velocity at all places and at all times.

Surface finish depends on the sand that you use, and on the pour temperature.
Pouring aluminum at over 1350 F can give a rough surface finish.

If anyone wants to learn foundry work, you have to get in there and pour some metal (aluminum is good to start with), and get a feel for it.
My first casting was pretty rough, but that is how one starts the learning process.
I still have that first pathetic little casting, and I have saved it because it was a huge milestone event for me at the time, and a resounding success because that was the first metal I had ever melted and poured.

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