Casting horns from resin

[Lee in Montreal]

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

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/vbullet...luvsound+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

[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/Laminat..._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