Sprayed-on 3D Printed Pattern Filler

[GreenTwin]

I was cementing the mold halves together, and had not had problems with the joint failing, and so I got over-confident and thought I did not need weights on top the mold.

The joint failed on this pour, but I still got a decent casting.

Unfortunately I got a large air bubble in the mold cavity, due to not venting the mold from the top.
I untimately ended up recasting this base, with good success with a weighted mold.

I was still using the boxy basin at the base of the sprue, which is a very bad method to use, but was what I had seen somewhere online.

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[wce4]

I was trying to use a brute-force method with very tall sprue, to basically force the iron into the very long runner and mold cavities.

This method did not work well at all, partly because I had not yet learned how to correctly tune an oil burner, and mainly because there was too much cooling effect down the very long path that the molten metal had to take.

At the time I made this mold, I did not have a working knowlege of how a correctly functioning sprue/runner/riser system worked, and so I just blindly stumbling along.

I got a few usable parts out of this method, but in general, this turned out to be a very bad/wasteful method in my opinion, with lots of partially filled mold cavities.

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[Steamchick]

Hi Green twin.
Your post #74 :
10 or more years ago, a friend was making Bronze castings (and brass) from sculptures he produced in Plaster. He found a foundry in Liverpool with the ability to take his sculptures, add srues, etc. and make castings, that he cleaned up and sold as works of art.
A 1kg. sculpture could cost £400~500 for a bronze casting, (>£250 for brass). - The brass ones sold for >£250 and Bronze for >£1000.... - But that is Artisan art pricing.
So value your castings as you think fit!
But my message is that there are foundries, if you can afford them! (you pay for metal plus expertise!).
K2

 

[GreenTwin]

Here was a second attempt using a large multi-pattern flask.

I minimized the sand usage with the addition of wood blocking inside the original wood flask.

This pour was also a failure.

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[GreenTwin]

While Martin (Olfoundryman) is a foundry metalurgist by trade, and worked many years in a foundry, and makes the most impressive imaginable cast aluminum carburetor bodies, I disagree completely about the use of a pouring basin.

With aluminum, you have a skin on the surface of the molten metal, and the idea is to never break that skin, because when you do, you have two skin surfaces that meet, which creates a small but critical cold joint defect (I think the term is called bifilms).

Pouring aluminum into a basin just churns tons of bifilms into the metal.
For a non-structural aluminum part, the bifilm contamination does not matter, but upon close inspection, they do show up in a part, and are known to cause failures in structural aluminum parts.

You are also churning a lot of air into the metal when you splash into a pour basin.
I am not sure why Martin is illustrating a pour basin, other than it works for some.
I think there is a far better method than using a pour basin like that.

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Edit:
Watching Martin's video at 17:30, I can see why his pouring basin works.
His basin is extremely small, unlike most that I see, and he is pouring as close as possible to the sprue opening.
I would really classified his basin more as a slight sprue extention, not a full blown pour basin as most backyard folks construct them.

Martins "basin" is really more for ease of pouring than anything, but you can also just as effectively pour straight down the sprue if you have good pour control.
I use a handle on the side of the pouring shank facing straight down, very close to the crucible, with a heat shield, to give very fine pour control.
Most don't hold the pouring shank very close to the crucible, and don't use a handle on the right hand, or use a handle that is horizontal, which is part of the reason you see so many folks pouring molten metal all over the top of the mold and onto the ground.

And his basin is small enough that he is really not getting a rolling churn, and no real waterfall effect either.

He fills the basin almost immediately, and keeps the spure full while the mold is filling, so in this instance, this is a very workable design, and basically is what I do but with some additional runner refinements.
I will post my latest pour arrangement.

Martin is one of the few individuals with long term commercial foundry experience, and his position as the metalurgist for the foundry where he worked meant that ultimately he was responsible for what was produced by the foundry.

I would trust Martin's recommendations over anyone on the internet, but with the understanding that Martin's methods are not necessarily the last word on how to do it, since there are methods used by Bob Puhakka that are very advanced and useful.

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[GreenTwin]

This is one of my more recent mold arrangements.

Some would say that this is a round pour basin, and I won't argue semantics.

This basin is directly over the sprue opening, and the path into the mold cavity is very short, since the top mold half is very thin.

And yes, I did spill some iron onto the ground, which generally happens when you get a bit anxious as the sprue becomes full, and you are keeping your eye on either the vents, or the riser, to be sure the mold filled completely.

And note that the concrete did not explode with molten iron spilled on it.
Concrete can explode if you spill enough metal on it, but from what I have seen in videos, it has to be something along the lines of an entire crucible of metal spilled suddenly on concrete.

What you can't see inside my typical mold is a smooth transition at the base of the spure into generally two runners, with no abrupt changes in direction or size from the size of the bottom of the spure.

My runners go past the mold cavity, and are contained in the drag only (drag being the bottom half of the mold).
The runners terminate in an offset circular spin trap (runner enters the round vertical trap on a tangent), which allows the flowing metal to spin around and trap debris, air, slag, sand, etc. as the spin trap is filling.

Once the entire runner system has filled with hot metal (you are preheating the runner when metal flows down to the spin traps), then the gates at the top of the runners begins to fill the mold cavity.
The gates are typically long and thin, such as 1/4" tall and 1" or more long.
The thinner the part, the longer and thinner the gates are, and often I use knife gates on thin parts.

Flow velocity is controlled by the gates only, and this prevents high velocity splashing inside the mold cavity as it fills.

The spin traps basically wash the sprue and runners out, getting rid of any lose sand, and preheating the runners.
Any air that is entrained in the molten metal as the sprue is initially filled gets washed down to the spin traps, and does not enter the mold cavity.

Once my round basin is filled, it also acts as a riser to prevent shrinkage defects.
You can that the top of the metal in the round basin is convex, which means that molten metal was drawn into the casting as it was shrinking and solidifying.

I have had good luck with this sprue/runner/trap/gate arrangement with both gray iron and aluminum, and get consistent results with it without defects.

If you add 1 oz of 75% ferrosilicon per 65 lbs of iron, the castings will be easily machineable without tempering, even if the casting is thin.
Any amount of ferrosilicon in excess of this amount will cause excessive shrinkage and hot tears in the castings.

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[GreenTwin]

A buddy of mine posted a link to this video.

I still like my ceramic sponge method, but there would definitely be some applications where this method would work well.

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[GreenTwin]

Another method that I discovered that worked quite well was the radial method, where instead of fitting most or all of the patterns in one flask, you cast batches of the same part, or similar sized parts, in a radial configuration.

This is probably the way I would mass produce on a small scale engine parts, if I were going to do that.
A bit of a crude method, but it worked well.

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[GreenTwin]

Thank you GreenTwin for all the info. One more thing would you be willing to share your stl file of this flywheel ? me likes a lot

I found some STL files that apparently were used to print that multi-piece 3D printed Ball Hopper Monitor flywheel.

8 files total, which are 4 for each side.

Some flywheel patterns are symmetrical when mirrored, and so you only need the files for one side.

I can't recall if this flywheel can be mirrored, but perhaps not since I have 8 files for it.

And when I pull one of these files into the Prusa Slicer program, they are very small, and so I don't know if the scale factor is off or what.
These files can be scaled to any size in the Prusa Slicer program.

If these files are too large to upload, I may have to email them, or perhaps load them one at a time.

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[Bazzer]

Greentwin

That is a really useful set of info that you have posted.

I ran a foundry about 20 years ago and we exclusively used resin bound sand, it works great. What resin do you use and how do you mix it into the sane.

We used a phenolic resin and it was mixed with the sand in a long mixing tube.

 

[Jasonb]

Regarding the comment that STL files arn't easily be modified. All the files I export and send to other people to CNC or 3D print I do as STP step files which can ne inporte dinto slicer software and also into CAd and CAM where they are dead easy to alter, resize, etc. I've even sent a single STp of a whole engine assembly and people have been able to access the individual parts and work on those to suit their individual machining/castng methods.

STL are not ideal to share unless it is to 3D print.

Taking that flywheel as an example it would be easier to share a single STP or maybe one file for each half and then people can chop it up to suit the size of their printer

 

[GreenTwin]

Jason-

Can you list all the file types that can be transferred between random 3D programs?

I have never gotten a good concept of that.

When I get back to work monday, I will try to repost a combined file.

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[GreenTwin]

Greentwin

That is a really useful set of info that you have posted.

I ran a foundry about 20 years ago and we exclusively used resin bound sand, it works great. What resin do you use and how do you mix it into the sane.

We used a phenolic resin and it was mixed with the sand in a long mixing tube.

I use Lin-O-Cure, by Ask Chemical.

It is what the local art-iron folks use, and they love it they can post-set carve all sorts of shapes and patterns in it.

I use a Hobart commercial kitchen mixer to mix up the batches.

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[Bazzer]

I use Lin-O-Cure, by Ask Chemical.

It is what the local art-iron folks use, and they love it they can post-set carve all sorts of shapes and patterns in it.

I use a Hobart commercial kitchen mixer to mix up the batches.

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Thanks, very useful advise.

 

[wce4]

I found some STL files that apparently were used to print that multi-piece 3D printed Ball Hopper Monitor flywheel.

8 files total, which are 4 for each side.

Some flywheel patterns are symmetrical when mirrored, and so you only need the files for one side.

I can't recall if this flywheel can be mirrored, but perhaps not since I have 8 files for it.

And when I pull one of these files into the Prusa Slicer program, they are very small, and so I don't know if the scale factor is off or what.
These files can be scaled to any size in the Prusa Slicer program.

If these files are too large to upload, I may have to email them, or perhaps load them one at a time.

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GreenTwin Thank you for your files but when I try to open them in Prusa or Cura slicer is says Failed to load. The file could be corrupt, inaccessible or did not contain any models.
I know I am a pain, but if you don't mind can you send it to my email at [email protected] Thank you.

 

[Steamchick]

Thanks Guys for teaching "un-initiated" me about foundry work. I'll probably never do any foundry work, but it is a bit of a special expertise, and you probably never stop learning. My Great Grand-father's brother had an iron foundry and made over 160 steam (winching) engines in Victorian times for coal mines.18 inch bore, long stroke, double acting and 40 foot long bed! Apparently, one report in the press recorded the wear on the bore of "less than 1/2in." when stripped after more than 30 years in use, and praised the quality of the castings. A bit bigger than the castings you are making. I wish I had a time machine to see the whole process, but you are giving me an insight into the business.
Thanks!
K2

 

[Jasonb]

Files won't open in the programe they automatically open in but they do download. Opens OK in F360 but not Alibre

 

[GreenTwin]

I pulled one of them into the lastest version of Prusa slicer a minute ago, no problem except the scale is very small.

I will email them.

When I get back to work, I will make some files for the latest version of this flywheel that I made not too long ago.

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[krypto]

If it's small It's probably metric versus inches. Scale to 2540%.

 

[wce4]

I pulled one of them into the lastest version of Prusa slicer a minute ago, no problem except the scale is very small.

I will email them.

When I get back to work, I will make some files for the latest version of this flywheel that I made not too long ago.

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Thank you for the email the files in the email are a ok. The files on the site will down load, but as Jasonb reply "Files won't open in the program". I tried in both the lastest version of Prusa slicer and UltiMaker Cura v 5.5.0. and no joy. But the files you email open in both slicer with no problem. Thanks again.