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Old 11-04-2018, 10:32 PM
Alvin Barber Alvin Barber is offline
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3D Printed Blow Mold

I'm way over my head on this project (frankly all of my projects are like this). First, I have no experience working with glass so please forgive me if I get aspects of this wrong. I work with metal and wood. I've searched the archive and the forum to get a start and would like confirmation.

Specifically, I am attempting to make a blow mold for a bottle. I need some expert advice on the mold design and corking.

The mold will be cast in bronze using lost PLA casting. While I can CNC route wood, I'm assuming better dimensional accuracy can be had with metal. The bottle is a finned shape one with sharp edges. I will only need 1 or 2 dozen so the mold doesn't need to be long lived.

https://photos.smugmug.com/photos/i-...-5qcHV97-M.png

Is this shape possible in a blow mold?

Assuming it is possible, will a two part mold design work? The fins have a 1 degree draft on them to allow movement when separating the halves. I'm guessing that I'll need an actuated mold boy to ensure that the mold halves open squarely.

https://photos.smugmug.com/photos/i-...-PwTw5RM-M.png

I'll keep my questions on corking until I've confirmed its possible. Thanks for reading this far and double thanks on any advice that you can provide.
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Old 11-04-2018, 11:00 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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The short answer is no,- you cant make this hand made in a small series in a studio.
You cant get a nice surface on it in a mold that cant move.
It would be possible to make if you wanted tens of thousands, but the start up price would be very high
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Old 11-05-2018, 12:09 AM
Alvin Barber Alvin Barber is offline
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Thanks for the reply Michael. When you say "can't move", you mean the piece can't move as it would be spun in a paste mold?
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Old 11-05-2018, 01:59 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Paste molds work on the principle that a porous layer of charcoal is dipped in or sprayed with water, that when in contact with the hot glass forms a steam layer cushioning the glass against mold.
But the glass has to be in motion the whole time , either rotating or in some cases up and down, say a square vase.
If you were to hold it still you would first get a very hammered and pitted type surface and a few seconds later very possibly check marks.
Industrial made glassware are blown in highly polished very hot steel molds. The glass is also very short- meaning it “sets” very quickly, minimizing the time spent in the mold. If you were to try that in a studio, youd still have a lot of issues with those wings, youd have to have a very hot glory hole or torch to firepolish, youd have to make special tool to finish the top end neck and opening on and on...
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Old 11-05-2018, 04:30 PM
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and you would need air pressure much more substantial than your lungs. The glasses that would perform in a mold of this nature won't support commercial color.

It might be a good plan to try blowing a simple mold 100 times and see if you like doing that. Make it a paste, turning mold. See how much time is involved in finishing the thing once the mold work is done. It can be a wake up call.
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Old 11-05-2018, 06:14 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Pete- I run into this all the time, forgive me Alvin for speaking over your head, I dont think Alvin is a glass blower, he is probably a industrial designer, Id guess a student since he hasent researched it, or is starting here
There is a ton of designers that want to repeat the Absolute Vodka success, its all in the design of the bottle. Ive made several prototypes, but never heard of one in production
So even it this bottle looks cool, for whatever its for, its far to production
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Old 11-05-2018, 08:34 PM
Jordan Kube Jordan Kube is offline
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Alvin, go for it. You would not want to cork these molds unless the glass inside was being spun and your geometry precludes that. The only way I see this as a two part mold is if the halves come apart without rotation. No hinge on the side, just pull apart facing each other. You could make up a system on a linear rail or similar with one side stationary and the other one sliding straight in.

I like to use two of these for quick and dirty linear motion that ends up being pretty accurate. They run on cold rolled steels rails. You will need to fabricate the plate that holds them together according to your rail width: http://www.cncrouterparts.com/linear...ings-p-33.html
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Old 11-05-2018, 10:35 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Yes yes we all understand how to do the mold thing Jordan, are you stepping up to blow them for Alvin?
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Old 11-06-2018, 12:37 AM
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Quote:
Originally Posted by Alvin Barber View Post
So, Nuka Cola huh?

Is this a project sanctioned by Bethesda?
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Old 11-06-2018, 02:38 AM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Whats that Greg?
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Old 11-06-2018, 08:12 AM
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It's a video game called Fallout 4.

For what it's worth, I could only envision these being made in glass (successfully) in an industrial setting. I have a tendency to irritate people with my "can't do" attitude though. Just calling it like I see it.
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Old 11-06-2018, 08:27 AM
Alvin Barber Alvin Barber is offline
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Thanks Michael, the paste mold explanation helps clarify the need for corking or lack there of. And no need to apologize, I'm under no illusions that glass blowing is a pedestrian art. I'm fascinated by it but also find it slightly daunting getting started. The bottle project is one that I'd be interested in as a destination in the learning journey. The last project of this type took me 3 years to complete and taught me a variety of skills from electronics to metal casting. It also left me with a box of uranium glass, two kilns, and glass blowing on my bucket list.

I'm definately not a glass blower. I do wish I was closer to my student days though. I'm a 50 year old engineer who works for a software company. As far as research, I've read the Schmid books. They clearly were meant for a glass blower and will likely be more meaningful when I've actually tried blowing glass. I've been collecting old patent memos on mold designs and reviewing SHA.org. I've talked to my local glass studio about lessons. I wanted to cast the bronze molds before I jump in. Although it looks like cast iron may be more appropriate.

Thanks Pete, not sure I'm up for a hundred of anything these days but I'll see how many I can muster on a simple mold from ebay. The bottle design is clear glass. Correct me if I'm wrong but the color support shouldn't matter.

Thanks for the reply Jordan. I understand the use of corking now. I was thinking a two part mold and linear rails. After Pete's comments on air pressure, not sure the fin details would turn out though. A multi-part mold that supports pressed fin details may work better like this video. https://www.youtube.com/watch?v=6Z3cEjQRoE4 Small world on the link to cnc router parts. I've got a 4x4 router table from them. Nice folks to work with.

Yes Nuka Cola , its a bottle from a video game called Fallout 4 made by Bethesda Studios. No, not sanctioned by Bethesda. My interest is small scale reproductions mostly for personal use or a short run for fans of the series. Its a grey area that is overlooked as long as it doesn't rise to commercial levels. I participate on a forum for prop makers called the RPF. The bottle replicas have been done in resin but not in glass.

Thanks again for the advice and comments everyone. I very much appreciate the help.
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Old 11-06-2018, 09:38 AM
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well, glass has a life and in molds, it's a short one. The glass itself needs to be engineered to have a life rather specifically tailored to the project. Coke bottle production would not go well using Sys96. So you would need the specific glass to be not only engineered but also produced by some one.

Big glass companies don't ever combine laminated color to clear glass for very good reasons regarding mismatch. So it's good it's only clear. But that clear will not match any other clear most likely and I don't quite know where you would find it. It's a bottle glass kind of glass and they usually are lacking in luster given their structure.
Finally, a word about undercuts. It's hard to tell if your design has them but they make mold blowing a hard job. I used to blow in artichoke molds and they had undercuts. Not fun.
With a design as detailed as what you have, filling the areas in the mold with discernible detail will mean you need a really runny glass and a skilled blower handling it to make the mold impression. My best guess is that a corked mold in that environment won't hold detail very long.

Now Michael knows molds, listen to Michael.
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Old 11-06-2018, 04:27 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Alvin ok that explains some, thanks. Let me try to explain the difficulty of blowing the fins, lets say the area of the fin is 3/8 x 11/2” at the fuselage- as the hot glass touches the inside of the mold only the glass in front of the fin opening gets blown out into the fin, very little of the glass around the opening slips in to the void. That glass expanding into the fin very quickly gets very thin trying to cover the whole surface of the rest of the fin , so now you have an amount of glass that has to cover ten times the original area of the fin opening. as it gets thin it cools instantly and it would be very hard to get the fin filled. Even if you heat the mold to 600C glass does not flow at that temp. If one actually managed to fill it then the angles and corners would be thinnest of all and would break just looking at it. If you opted to make the fins solid, then it would take high pressure to fill the fin shape, and it would take so much glass that the bottle would hardly be hollow below fin height

Last edited by Pete VanderLaan; 11-06-2018 at 05:20 PM. Reason: chamged spelling on angels to angles. I like angels better though. ( he's right however!!)
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Old 11-06-2018, 04:37 PM
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I honestly think I would approach this a different way.

I believe I would pressure press the fins and a flat plate like they would and pressed ashtray. Have a mold made that would let you slot the now pressed fins and flat plate holding them at the bottom. Gather up and blow into it and let the presses glass fins and glass plate be the completion of the mold. The hot glass would seal to the first piece and make the connection pretty as close to seamless as you could get.

Might be more effort than it is worth but it is honestly the only way I think you could do it on the cheap. Also rife with failure and tool marks I would suspect.



Maybe a bronze cased mold the would pull apart where you could hot drop glass inside, pressure press into the fins, then close and blow into it like a normal mold. I am also not going to apply for this position.

Last edited by Scott Novota; 11-06-2018 at 04:40 PM.
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Old 11-06-2018, 05:22 PM
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Quote:
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I am also not going to apply for this position.
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Old 11-06-2018, 08:51 PM
Alvin Barber Alvin Barber is offline
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Originally Posted by Pete VanderLaan View Post
...The glass itself needs to be engineered to have a life rather specifically tailored to the project....a word about undercuts. It's hard to tell if your design has them but they make mold blowing a hard job....My best guess is that a corked mold in that environment won't hold detail very long...Now Michael knows molds, listen to Michael.
Thanks Pete, I am and will. The engineering on the glass itself give me another research angle. I'm also concerned about undercuts. I've designed in a 1 degree draft for the two part but will likely need to rethink that if I'm going to try a press and blow combination. I'm going to cast a series of molds to try different approaches. None will likely work but they will be informative. I understand on the corking - only for turn molds.

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Originally Posted by Michael Ahlefeldt-Laurvig View Post
Let me try to explain the difficulty of blowing the fins, lets say the area of the fin is 3/8 x 11/2 at the fuselage- ... If you opted to make the fins solid, then it would take high pressure to fill the fin shape, and it would take so much glass that the bottle would hardly be hollow below fin height
Michael, thank you - That makes it very clear. I think that I understand the concept as its the same when hydroforming metal over a sharp corner or protrusion. Eventually the metal tears or splits. On the idea of solid fins, that may be the only way to get close to a successful result.

Quote:
Originally Posted by Scott Novota View Post
I honestly think I would approach this a different way.

I believe I would pressure press the fins and a flat plate like they would and pressed ashtray....Maybe a bronze cased mold the would pull apart where you could hot drop glass inside, pressure press into the fins, then close and blow into it like a normal mold. I am also not going to apply for this position.
Thanks Scott, I'm onside with this idea. At least, I can make the mechanics work. As a starting point, I can try blowing the main body section to see how that works and press the fins separately. If that works, I'll proceed with a 3 part mold with a plan to press and blow or vice versa. I'll redesign the molds and get to casting.

Thanks again to all for taking the time explain and provide suggestions and advice. I'll post pics as I get them.
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Old 11-06-2018, 09:11 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Thanks for the edit Pete- funny!
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Old 11-06-2018, 09:45 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Scott yes, it could be made. But Alvin is this just a hobby engineering problem for you? The end result does not stand in relation to the cost and effort. A video game coke bottle?
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Old 11-06-2018, 11:49 PM
Alvin Barber Alvin Barber is offline
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Scott yes, it could be made. But Alvin is this just a hobby engineering problem for you? The end result does not stand in relation to the cost and effort. A video game coke bottle?
Yes just hobby engineering but not a problem - more like a puzzle that has to be solved. My motivation is learning new techniques. Its the act of making something that I've never done before - using new tools and new skills - that lights up my brain. The closest I can explain it is creative OCD - Adam Savage did a TED talk that probably explains it better. https://www.ted.com/talks/adam_savage_s_obsessions#t-914935 (I'm nowhere near as good as Adam Savage but its the same frenetic itch)

Last edited by Alvin Barber; 11-06-2018 at 11:52 PM.
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Old 11-07-2018, 12:42 AM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Well I didn't mean it as a problem in a negative sense, I meant more as in challenge. Thats probably what some of us are doing on this board- looking to solve a challenge, and at the same time solve some of the secrets that have always surrounded glass. Pete has been a light in the dark for more than 30 years for me. This board is an incredible wealth of information, that didn't used to exist
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Old 11-07-2018, 01:40 AM
Max Epstein Max Epstein is offline
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One thought that comes to mind is you could make a mold for the basic shape without the fins so you can cork and have a very nice bottle. I'm not sure about how you would accomplish the indentation, maybe you could make a stamp from the cad file. Hit the side with a blow torch and imprint.

You could add the fins by hand and let the artist shape them. With some practice they'd probably look pretty good, but it will never be perfect and each piece will be a unique piece of art while still looking recognizable. This may not be the Bathesda-esqe goal of post-apocalyptic machine perfection you are going for. Just some thoughts.
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Old 11-07-2018, 08:02 AM
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Materials are funny. Somethings can make sense made in some materials, many make little sense. When I see the repetitive term "Glass Artist", I pause since I never see the term "Bronze artist", or "acrylic paint artist."

Glass is a medium worth exploring for reasons involving how it handles light. As Banksy said , "you take years to learn your craft and then this. "

That is one of the most honest things I've ever heard describing the arts.
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Old 11-07-2018, 10:37 AM
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I know of a company or 2 that could make this item., Like Scott said, it would have a pressed bottom and a blown top and would then be assembled together. I would think that adhering them together much as they do some of the stemware in China would be the easiest way to go, but it could also be done hot if a bit of trial and error was performed. I think that the pressed bottom portion should be made from cast iron and then machined and the top could possibly be made from a graphite mold. either way, the 3 -D printing of the positive would not be the most efficient way to go. Old school machining and patterns would probably be the best.
In production, this item would probably require a 4-6 or more man "shop" to accomplish this production. People that are used to working with iron molds and doing numerous tasks after the initial blowing would be advantageous. Finishing the top would require another necking tool and several people or setups with polishing torches would be ideal.
All this said, it will not be inexpensive and will require making quite a few mistakes to ultimately see a desirable outcome I don't think people realize how many unacceptable pieces are made even in factory production before they get the "rhythm" and finally get production on a piece and sometimes it never happens and it requires a complete new mold entirely.
These are just my humble views of how this might be achieved.
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Old 11-07-2018, 09:11 PM
Jordan Kube Jordan Kube is offline
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Alvin, think about 3 or 5 degree drafts. Not much more visually but a lot better insurance I've found.
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