Bob Puhakka on Bifilm theory

I used my smaller sprue cutter and a straight sided cutter to form a pouring basin away from the sprue on a ganged knob mold. I also tried to end the sprue feeding directly into a runner in the drag and choked at the gates in the cope. The first one poured out, but I shorted myself on the second and ran out of metal. The underside of the knobs show a lot of oxides and there was a little shrink as I missed the placement of the riser and am not sure it did any good at the end of the tapered runner. I poured hot and the surface finish suffered, but the riser looks like good round stock for other projects.
If I can get consistent results with a gate/ runner configuration this would lend itself to a matchplate with a premade pouring basin for a little additional height and a more distinct dam.






The center knob pulled slightly. The locating dowels were too tight and pulled from the cope, so a little touch up on them and the overall draft is in order.

 

Nice piece of work there, well done. Don't change a thing unless you have a problem....

We made literally tons of charge air cooler castings for turbo diesels


The longest was 40 inches or so. They were poured standing up just as shown

Nominal 1/4 wall in Aluminum perm mold

Gating was the same as the test bar mold

A long thin ribbon gate connected the riser to the part

I would guess that bumping temperature (within reason) could overcome mis runs and allow a longer pouring time (if there is a need)

If this is your design you could perhaps add more ribs to help feed thin sections?

Or eliminate the thin sections? Have you seen the new organic (bone shaped) designs that are coming out?

Great time to be in the trade, everything we knew is changing - I like it

 

Here is the second video.
This guy is a real character, but god bless him for taking the time do make these videos.
Beggars can't be choosers as they say, and any info at all is better than none.

 

OK hope everyone realizes what a big deal Bob doing these videos is, a singular honor for the hobby

For a Canuck its like Gretzky came over to take shots in your driveway

What is the football, real football, basketball, baseball, and aussie rules equivalent?

 

Thanks for your comments.

It is my design with an crucial criterion being light weight. So, increasing section thickness and increasing ribs would not be in line with the underlying reason for the existence of this design. "Everybody" makes very heavy straight edges but there are no comparable light and strong straight edges.

I am only tangentially aware of organic designs. Love the concept and realize that bone architecture is driven by reaction of bone growth to piezoelectric stimulus within the bone itself resulting in optimal structural "design." It would be nice to be able to emulate this on a practical level.

Denis

 

OK, if I understood him correctly Puhakka said he had a fair number of videos posted in his Linkedin account? I went through the gymnastics of joining Linkedin just to see the vids. But, being the luddite that I am I was unable to find them. Anybody have any clues as to how to see them?

Denis

 

It seems that John Campbell originated many/most/all? of the bifilm theories, and Bob was one of his mentors.
As I research the bifilm theory today, one thing that jumps out is that this appears to be a dynamic area of study, and there are very recent developments.

Apparently there is no one particular method, but actually several different new methods that are available now.

Most interesting material for sure.

.

 

I am Officially beating My head against My desk...Bob spent 15 minutes ( OK 12) explaining a complicated calculation for determining the angle of a sprue ( technically the top area and bottom area) and then told us not to worry about it on anything under 20 inches in height. I must have misheard MUST HAVE because my Maximum pouring height is currently 10 Inches with 3.5 being my most common. and someone can ask, but other then not being able to keep the sprue filled and creating a vortex, as far as the top of a sprue goes, the bigger the better... By the way I did out the Math on his example and using a round sprue cutter you would have a 1.12 inch bottom, and a 1.76 inch top or an 88.472 degree angle ... so 1.5 degree, not alot of taper.


V/r HT1

P.S. Please feel free to check My math, I'm 50 and have forgotten a few things

 

He likes to talk, and sort of beat his own drum, but any information is better than no information, at least from the standpoint of it starting a discussion about the math/commercial side of how things are done and the backyard folks and how they do things.

I ran across the "10 Rules for Good Castings", which I think comes from John Campbell, and there seems to be some good info there.

per John Campbell
1. Provide a good quality melt.
2. Avoid liquid front damage.
3. Avoid arrest of the liquid front.
4. Avoid bubble damage.
5. Avoid core blows.
6. Avoid shrinkage damage.
7. Avoid convection damage.
8. Plan segregation distribution.
9. Control residual stress.
10. Provide location points.

If you look these steps up and read about how to implement them, it is very concrete and useful information, and perhaps more generally applicable than sprue/riser/gate calculations for small castings.

http://www.atlasfdry.com/10rules.htm

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well Im certainly Glad I dont Have to Calculate Hyperbola, since 5 Minutes of looking at the equations and I'm getting my first grey hairs, and a horrible headache, at least the Math as presented so Far I can Follow . and his notation thet the lower cross sectional area remains the same throughout the runner , while contradicting my formal training corresponds with my own personal experience. I'm waiting patiently to see what comes next

V/r HT1

 

I have an idea that this is where he is headed, or something using these techniques.

https://www.sfsa.org/doc/2018-4.11 Highland - Marquardt.pdf


I can't get this one to download in pdf, but it can be read on the screen.
The graphics take a minute to load, so be patient.
https://www.researchgate.net/publication/326214920_Optimized_Gating_System_for_Steel_Castings


Some mind-blowing techniques, especially for HT1 who I think was trained old-school.
This is way way outside his box (no offense intended), and pretty far outside my box too to be honest, I am a bit old-school myself, but the concepts are worth a look.
Luckily my mind is already blown, so there is no danger there.
Times/techniques, they are a changin (as they use to say in the old days).

Edit:
Welcome to the 21st Century.
Make the leap over, or stay on the "flat-earth" side?


.

 

OK so this is the bleeding edge of foundry research, maybe around 20 years old versus the 4,000 year old lore we are used to

And it is only of use for highly stressed engineering castings

You can pour aluminum down an anthill and get a shape

For most of what we are doing as a hobby this is maximum overkill

As something to study for self study improvement/ continuing education this is great stuff - I live for this

But don't any one let this math get in the way of git er done....just do what you like it will be great

I see there is a condensed version of Campbells 700 pager...I will order tomorrow and let you know if it simplifies this

 

Was wondering how they were going to slow the metal down....that vortex riser makes so much sense.

It's not really much math at all...a simple spread sheet would make it easy as pie.

Al

 

The first paper (Continuing the Conversation Naturally Pressurized Fill System) is dated November 12, 2018.
It does not get much more bleeding edge than this, unless I missed something.

The second paper (Optimizing the Gating System for Steel Castings) is dated April 13, 2018.


John Campbell's book "Complete Casting Handbook, 2nd Edition was published August 25, 2015.
https://www.elsevier.com/books/complete-casting-handbook/9780444635099

There was a piece of John Campbell's book posted online, and it is highly technical, and the parts I saw were not something that could be readily used/applied to what we do.
The other parts may apply, but I have not seen those.

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QUOTE="PatJ, post: 12932, member: 17"]It seems that John Campbell originated many/most/all? of the bifilm theories, and Bob was one of his mentors..[/QUOTE]

Minor correction here

Dr Campbell is indeed the originator and faced an uphill and still ongoing battle in the industry to put these concepts across to industrial practitioners - look up the Cosworth process

Bob took hold of these concepts and implemented them with a vengeance in real world castings (mentee, not mentor)

There is tremendous inertia and resistance to change in the foundry industry (in fact everywhere in all people), thus Bobs edginess and frustration, he has delivered the goods, but we foundrymen don't listen....

Likely will take 50 years to become accepted foundry practice, same as that other science fact we are arguing about that we won't bring up here

 

Here is a reference I found.
http://www.industrialmetalcastings.com/casting_cosworth_process.html

I have read stories in books about guys who worked in foundries, and they seemed to indicate that there was a great deal of secrecy in how things were actually done, with the old guys adding handfuls of "mystery" ingredients, and nobody knew exactly what it was or what it did.
Job security for sure if you are the only one who knows how it all works.
I have seen this in the electrical controls business too.

So I would imagine a much higher level of secrecy between foundries, with all sorts of trade secrets that would never get shared or published.
Very much a black magic affair for sure I guess.

I read that during the war (the big one), the different manufacturers in Germany did not share information, and often multiple firms would be working independently on solving the same technical problems, even with the outcome of the war at stake. They were all competing for funding.

So I would expect a hyper-secrecy in today's foundry world, and for good reason, but that would really hamper research and collaboration.

And I know first hand how resistant corporate types are to the "C" word (change).
That is why I went into business for myself. Committee of one.

.

 

Yep, that is what I meant, but not what I said.
Bob mentions that in one of his videos, either the sauna one or the camping one.

.

 

More info here, for those who like reading.

http://cminovacast.com/paper4.shtml