Casting horns from resin

[Lee in Montreal]

Well, I started this thread in order to keep another one clean :D

When I have an original horn that I want to replicate from resin. What are the different types of molds that can be done. Obviously, we are not talking injection molding here. I am familiar with rotomolding, but I don't think t will be cost effective to CNC an aluminum mold for such a project.

So, Rich, share your experience ;)

[richluvsound]

Lee,

Nah , your a smart arse ! I was merely sharing your views on time consumption when finishing MDF CNC'd parts .... , but since you asked ..... do a search ! I'm sure my experience is well documented here
for anyone wanting the information . Any information not here is deliberate , for copy right reasons and the preservation of my lively-hood . The process is not a hack kinda thing . Weekend warriors should hire a pro to do it ... resin is expensive , but once you have the mould its easy !


http://www.audioheritage.org/vbulletin/showthread.php?29232-Homage-to-Northridge&highlight=richluvsound+H9800

[macaroonie]

Now Rich you know probably that I am sending you down some ' unique ' drivers to play with so all it needs now is for Lee to post you over a couple of bits of his MDF and well ..... who knows.
Could be something to while away the winter in front of your new woodburner.
Resin has to be the way to go for this task althoughI see the imense value of CNC for accurate shaping to generate a mold.

[Lee in Montreal]

I wouldn't mind making a master of an Iwata horn, to be replicated in plastic for those who don't dig wood ;) It's all about the challenge. BTW I shall get the final SolidWork file of the Iwata early next week.

[kartsmart]

look over this web site it has some good info.
http://www.aeromarineproducts.com/

[kartsmart]

this page might be helpful
http://www.aeromarineproducts.com/videos/index.htm

[Allanvh5150]

Well you can always CNC them out of plastic....

Allan.

[Lee in Montreal]

Well you can always CNC them out of plastic....


Ah, ah, ah. The purpose of casting horns and using a plastic is to avoid machining except perhaps for the original mold :D

[Allanvh5150]

Yea I know. Tooling plate is damned expensive though, plus the machining. If you plan to make lots of em......

Allan.

[loach71]

How about using laser lithography / liquid resin to make the halves of your molds or the plugs for making molds from epoxy-glass?

[Lee in Montreal]

How about using laser lithography / liquid resin to make the halves of your molds or the plugs for making molds from epoxy-glass?

Are you talking about 3-D printing? This revolutionnary process would be an alternative. All that is needed is a SolidWorks file, and you get a perfect prototype that you can handle and use as a master.

http://news.discovery.com/autos/printing-in-3d.html

[richluvsound]

First you need a pattern , 3-D copying , hand made , CNC ... makes no difference really . Then make your mould . Vinamould is the cheapest and you wont get many out of it before it starts to fail , Silicone is expensive and more durable , but still you will only get about 10 castings before you need to make a new one . Fibre glass .... most durable and easy to repair .

Your filler is the most important . Pure resin generates too much heat . Thats a lot of mass curing and can combust with out help ... Need to cast in two parts , no under cuts and low heat . Shrinkage is a huge concern . The mix needs to be very accurate or the two halves will be different sizes .

Risers are important . I would suggest using a vacumn bag to remove the air .

This is not a first timers casting project . Practice making something easy .

Widget has far more experience than me with casting horns ! Guido is doing some clever stuff too . CNC with a polyurethene sheet material .

Got for it ..... maybe take a casting course at your college . The mould is hours of work and the materials are expensive . you can spend 60 hours and a thousand bucks and not get anything useful .

I can do it if the order is there .. money honey ! if you want to have a whip round for the materials I'll post the process start to finish . Still don't think anyone here will get it right first time . I wasted a lot of money learning the process . Its one of those things you learn by experience !

Get widget to build you a mould . not cheap ,but you'll have a mould you can use !

Rich

[Mr. Widget]

I use a high grade silicone for my molds... it costs well over $1000 for a five gallon pale. The benefits are that it holds excellent detail, is very stable, and lasts much longer than less costly mold materials including other silicones. There are urethane mold materials that also work very well and are significantly less costly... though extra care in application of a release agent are necessary if your horn is cast from a urethane material.

Something to consider in casting horns with negative draft, is that you need to design the mold so that the undercut areas can be released... one method is to make a two part horn, but a single horn casting is better if it is possible. Using a two part mold incorporating a slide will usually make a single part horn possible. It may also be possible to release an undercut if you use a soft silicone or other mold material, but this requires proper support of that material.

As for the idea of using a 3-D printing process, the material is costly and a fair amount of surface finishing is required.


Widget

[lgvenable]

Laminated Object Manufacturing
http://en.wikipedia.org/wiki/Laminated_object_manufacturing
"LOM"
I worked on development of the coated papers for this, it easy to form 3D parts this way. After forming the part, its possible to create a negative and a positive mold, and then mold your part. The finish of the part has to be done carefully not to show the 0.005" steps of each paper sheet as they were laminated. Thats done by sanding and finishing the laminated object to a perfect surface.This process creates a perfect 3D part of exactly what you can design via auto-cad, and then laser cut after each 0.005" step.

I saw the doors from the 1st generation Viper designed this way. The car industry (ok at least Chrysler/Dodge where I SAW it in use) used to use this and now uses UV stereolithography and selective laser sintering to do this; but this was the process used in the late 90's. Still available out there.
Larry;)

Laminated Object Manufacturing is a Rapid Prototyping and Manufacturing process that uses a carbon-dioxide laser to create successive cross-sections of a three-dimensional object from layers of paper with a polyethylene coating on the backside. The first step is to create a base on which the paper can attach itself to. This is done by placing a special tape down onto the platform. A sheet of paper is feed through with the aid of small rollers. As the paper is feed through, steam is used to heat the coating on the paper so that each new layer will adhere to the previous layer.
The carbon-dioxide laser then traces, or etches, the outline of the cross-sectional pattern into the top layer of paper. Once the laser is done etching the pattern, it burns a border into the paper that contains the etched pattern. This enables the part to stay intact as each new layer is created. Once the border has been traced, the laser then proceeds to create hatch marks, or cubes that surround the pattern within the border. The cubes behave as supports for the part to ensure that no shifting or movement takes place during the entire build.

When the build is completed, the part, attached to the platform, needs to be removed from the LOM. Depending on the size of the part, the block to be removed may weigh a great amount. Thus, it may take more than one person to remove the build from the LOM. After the part has been successfully removed from the LOM, it must then be removed for the actual platform. Again this may take the work of more than one individual. A wire is used and placed between the part and the platform to "cut" the part away from the metal platform. In a similar fashion to sawing wood from a tree, then wire is moved back and forth between the part and platform. This continues until the part is completely removed.

The border, or frame of the part is then removed. The next step involves decubing. or removing the supports. Often times the supports can be removed from simple shaking the part; other times it is necessary to use a chisel to pry the cubes away from the part. When all of the cubes have been removed, the unfinished part is sanded down and a lacquer is used to seal the part. Being that LOM parts are made from paper, humidity and temperature affect the structure and composure of the part if it is not coated; hence, the lacquer serves as a protective measure. The LOM is very useful in manufacturing large parts quickly.

[Mr. Widget]

The finish of the part has to be done carefully not to show the 0.005" steps of each paper sheet as they were laminated. Thats done by sanding and finishing the laminated object to a perfect surface.This process creates a perfect 3D part of exactly what you can design via auto-cad, and then laser cut after each 0.005" step.There are perhaps a dozen or more "rapid" prototyping processes currently in use. They all have their benefits and all require a fair amount of hand work and care to create a "finished" part... be it a positive or negative.

I have literally spent thousands of hours over several years finishing SLA, SLS, and FDM parts...

These glasses were a prototype I did. The model in the picture is a translucent urethane resin casting made of a hand finished SLA model. It just takes a little patience. ;)


Widget

[jcrobso]

http://www.youtube.com/watch?v=jQ-aWFYT_SU&feature=related

Watch the link, just scan your horn into the PC and print!:eek:

[Eaulive]

http://www.youtube.com/watch?v=jQ-aWFYT_SU&feature=related

Watch the link, just scan your horn into the PC and print!:eek:

I got to get me one of these!!! :bouncy::bouncy::bouncy:

Man, technology is really amazing :applaud:

[Allanvh5150]

That stuff is rather old now. You will not like it so much when you see the price

Allan.

[felixx]

That stuff is rather old now. You will not like it so much when you see the price

Allan.


How much do you think will cost?

Here are a 3D cutted horn but this time on plywood and have the same topology....and not cheap at all:(:
http://gtsound.web.infoseek.co.jp/english/gt_horn01_e.html
http://gtsound.web.infoseek.co.jp/english/gt_products_e.html

[Lee in Montreal]

A short BBC clip on how to reproduce... by machine.

http://news.bbc.co.uk/2/hi/programmes/click_online/9550469.stm

[Mr. Widget]

How much do you think will cost?To create an entire horn? Depending on horn size it could be a few grand... and the material isn't going to be sonically as good as sonoglass or some other very dense resin.


Widget

[escultor]

Well, I started this thread in order to keep another one clean :D

When I have an original horn that I want to replicate from resin. What are the different types of molds that can be done. Obviously, we are not talking injection molding here. I am familiar with rotomolding, but I don't think t will be cost effective to CNC an aluminum mold for such a project.

So, Rich, share your experience ;)

Well a simple two halves plaster mold will do it for a couple of copy´s
One step higher will be a resin mold with a solid wall

[richluvsound]

My experience of plaster is of extreme shrinkage ,not to mention the fragility . I would not waste my time. If you tare the release it pulls away the surface of the plaster . The release I use is water based and spray applied . Washing the release off to to re-aply is fraught with danger . If you use a wax based release , patching would be impossible .... You would need to remove all the wax to ensure a good finish . All these variables considered , you would be better off making them individually in wood if you only want 2 pairs ;)

another 2 cents worth .

[escultor]

My experience of plaster is of extreme shrinkage ,not to mention the fragility . I would not waste my time. If you tare the release it pulls away the surface of the plaster . The release I use is water based and spray applied . Washing the release off to to re-aply is fraught with danger . If you use a wax based release , patching would be impossible .... You would need to remove all the wax to ensure a good finish . All these variables considered , you would be better off making them individually in wood if you only want 2 pairs ;)

another 2 cents worth .

You are rigth, I usually pour wax on them and forgot the release coat needed for the resin :banghead:
I will try a acrilc spray coat on the plaster surface of the mold ( spray it to the point the plaster wont suck more ) followed with wet sanding..then the spray coat
You can deal with the shrinkage using medical plaster bands in thin layers, but require practice
the same with the spray and sanding..multiple coats on black and grey automotive paint and a lot
of wet sand to grain 1500 wil produce a perfect ( is very easy to notice defects just locking at
the mirror image ) surface for a mold.
For a "production mold" I will follow the same procedure on the original and then do a mold
in resine 50% and fine grain quartz 50...dont try to do a one piece molde.
Just got TAD 4002 drivers and hopefully will try to build some horns

[rlsound]

There was a link to a company that produces JBL's horns. Anyone have that URL? I forgot to bookmark it!

[pos]

here is the thread:
http://www.audioheritage.org/vbulletin/showthread.php?31106-JBL-horn-supplier

[Guido]

Did one of you contact these guys?

[Mr. Widget]

Did one of you contact these guys?I talked to them at the SF AES conference... what do you want to know?


Widget

[lbstyling]

Im a DT school teacher by trade, and forgive me but all these processes seam overkill for what you want.

Just vacuum/pressure form it.

Get a large sheet of vac form plastic (HIPS) in the thickest gauge you can get your hands on (3mm?)

heat it up till it goes floppy,
place it on a flat board (kept warm)
place your horn on the top, mouth down, with a 'bung' in the top that acts as an adapter for a vacuum cleaner,
suck all the air out,
leave for 1 min.
pull the mould off.

voila!

It will take you at least 2 attempts to get the temp right. As long as the horns throat continuously increases in size from the entrance to the exit your alright.

The only problem is that your finished product will be smaller than the original by the thickness of its wall (think russian dolls). What you would need to do to correct for this is to make a negative mould of the original first, then vac form over this instead, making a positive of the negative= original.

The finished product will be stiff'ish' but you will probably want it stiffer, so just wack some fiberglass on the outside while its resting on the male mould (keeps its shape propperly while the fiberglass dries)

[richluvsound]

Dear DT teacher ,

You wont get the detail with this method . You need sharp corners . To achieve this the plastic would need to be almost molten. Have a look at some horns . They do indeed flare both ways . BTW, please explain how you get polyester or epoxy to bond structurally to acrylic or perspex ?

Rich

[Mr. Widget]

I agree with Rich, I have done a fair amount of Vacuum forming and even with an elaborate vacuum forming rig, you really won't get the detail... and besides, you will end up with a plastic horn that needs to be dampened. The 60lbs. resin horns I have cast and the injection molded sonoglass horns JBL uses are quite inert as well as massive, with very thick wall sections.


Widget

[lbstyling]

You wont get the detail with this method . You need sharp corners . To achieve this the plastic would need to be almost molten. Have a look at some horns . They do indeed flare both ways . BTW, please explain how you get polyester or epoxy to bond structurally to acrylic or perspex ?

Ahh yes, I was thinking os and jmlc style horns which this approach could work for. It would be less successful with a square horn as the material would/could fold on the corners. but you could still drill holes allowing vacuum points to attach to any problem areas. And yes you would need a substrate that allows bonding to the two dissimilar materials. I have made much more complicated shapes than this using vacuum forming, you just increase the vauume points to improve tight spots as you go. Hell, if I can vac form a 1/4 scale porsche 911 shell thats almost indistiguishable from the original and Im no pro, I really cant see why it isnt worth a look.
Ill take your word that horns flare both ways, and Im unsure what details you would be thinking of on a horn? I have vac formed over mdf with tippex on it and you can see the marks in the plastic, so it can show detail.
To be honest, im surprised this is seen in such a negative light.

http://www.youtube.com/watch?v=yhajk_IDTUo

hears a hot tub being vac formed.
http://www.youtube.com/watch?v=vrCqbuli78c

[Mr. Widget]

Hell, if I can vac form a 1/4 scale porsche 911 shell thats almost indistiguishable from the original and Im no pro, I really cant see why it isnt worth a look....and you can do that with a .25" or thicker substrate? ;)


Widget

[lbstyling]

...and you can do that with a .25" or thicker substrate? ;)


Widget

not to a sharp edge, but you dont need to use a thick substrate if your reinforcing it do you.;)

The approach will lean towards smoothing edges slightly regardless of the thickness of corse, but is that the end of the world?? considering the compromises that could be made using other methods?

Just for your interest a subtrate being added to acrlyic (also vac formable)
http://www.youtube.com/watch?v=TR1m8IkxVtc&feature=related

[Guido]

I talked to them at the SF AES conference... what do you want to know?
Widget

Widget, what a question...

I think they won't sell H9800's but one could ask.
Otherwise they write that one can use their standard molds and modify it slightly. So what comes to mind?
E.g.: I want to use your standard H9800 mold and need a modified throat to accept Radian 951PB drivers (or whatever one can modify). I order xx pairs. What would be the price?
Group buy?
Any other ideas?

[Allanvh5150]

...and you can do that with a .25" or thicker substrate? ;)


Widget

I have a customer that vacuum forms thicker than 1/4". His vacuum press is huge and vacuum forming this thickness is a real pain in the butt. Sometimes the rejection rate is 60%. You also have the issue of shrinkage when the plastic cools. I would think vacuum forming is not accurate enough.

Allan.

[Mr. Widget]

I would think vacuum forming is not accurate enough.Exactly!

That was the point Rich and I were trying to make.



I think they won't sell H9800's but one could ask.Let's see... piss off one of their best customers to make a couple of hundred bucks? What do you think? Not to mention I would hope Harman is smart enough to have a contract that would protect their IP and anything close to your suggestions would then be blatantly illegal.


Widget

[Guido]

Let's see... piss off one of their best customers to make a couple of hundred bucks? What do you think?
Widget

OK this forum got rude these days.

All CD horns or Biradials are more or less based on the same principle. So all companys copy more or less each others designs. You can modify a given Horn to your needs and as long as you don't sell it as JBL Hxyz clone nothing is wrong.
A member modified the Everest 2 horn for better linearity. I tried it and it works. It still looks like a EV2 horn but is it still one?

[Mr. Widget]

OK this forum got rude these days.I assume you are saying that I said something rude? I am surprised by that comment, but I'll assume it is directed towards my post as it was quoted. I certainly had no intention of being rude. I suppose my tone was being a bit sarcastic, but I was surprised at your suggestion. I apologize if I offended you.



All CD horns or Biradials are more or less based on the same principle. So all companys copy more or less each others designs. You can modify a given Horn to your needs and as long as you don't sell it as JBL Hxyz clone nothing is wrong.In manufacturing, a tool (the mold) is usually owned by the client. In this case that would be JBL/Harman. You can't use someone else's tool. If you wanted to send your own geometry to this company and your geometry happened to be very similar to JBL's I doubt they would have a problem with that. I am not sure if the resin that JBL has trademarked as SonoGlass is a proprietary formula, if it is I am sure you could have them use something similar. The point is that you can have these people make horns for you. I doubt they would have any problem making you your own tool with your own geometry, especially an "improved" horn, but you will be spending thousands on the tooling before you ever get a single horn. For a large horn you are going to be buying a very expensive tool.


Widget

[Lee in Montreal]

Guido, if one of my suppliers was using my drafts to sell components on which I have spent years of expertise and tons of money to develop, I wouldn't be too happy about that and a law suit will most likely follow. Even if all brakes are round and made from the same material, every race brake company has their own "tricks"... :D

Therefore, the supplier for JBL's H9800 will be more than happy to apply the same expertise on your own expen$ive molds as they did with JBL's molds. But I think it is where it will end.

[Guido]

Widget, Lee

YOU ARE RIGHT!

All this is clear for me. I developed a special mold for plastic containers years ago. I know the process. I DON'T want to buy JBL clones and I DON'T want to copy JBL Designs. I use my own H9800 type horn which only cosmetically looks like a H9800 any longer. I'm happy with CNC'ing and there will even be a 2" type.

I was just refering to that quote of the AES report (http://www.positive-feedback.com/Issue52/aes.htm): (http://www.positive-feedback.com/Issue52/aes.htm%29:)
Quote start
They had a wide variety of custom injected horn designs on display that they'd made for customers. Incidentally this stuff is also machineable so you can take a standard design and alter it for prototyping purposes
Quote end
In my understanding this means that I can use a given mold and modify details.


Maybe I misunderstood this? :o:

[Guido]

I assume you are saying that I said something rude? I am surprised by that comment, but I'll assume it is directed towards my post as it was quoted. I certainly had no intention of being rude. I suppose my tone was being a bit sarcastic, but I was surprised at your suggestion. I apologize if I offended you.
Widget

Forgiven :)
I've gotten sensitive to Forums these days.

[Mr. Widget]

I was just refering to that quote of the AES report (http://www.positive-feedback.com/Issue52/aes.htm): (http://www.positive-feedback.com/Issue52/aes.htm%29:)
Quote start
[/FONT]They had a wide variety of custom injected horn designs on display that they'd made for customers. Incidentally this stuff is also machineable so you can take a standard design and alter it for prototyping purposes
Quote end
In my understanding this means that I can use a given mold and modify details.


Yeah, they had horns for several manufacturers on display... most were el cheapo looking basic plastic horns... the JBL horns were using much thicker cross sections and a different material... at least for the more expensive ones.

As for machining, I am sure post processing is possible, but that tends to add a fair amount to the cost of an item. Typically you want it to pop out of the mold and be as close to finished as possible, though that isn't always the case.


Forgiven :)
I've gotten sensitive to Forums these days.:bouncy:

Now, I'll sleep better. :)


Widget