That little Craftsman CNC machine sure looks cool, but most of us are probably wanting "DIY" waveguids because $200 is too much for us to spend on a wave guide...jcx said:
What do you mean by expensive? I can buy can of epoxy at lowes that would probably be enough for one or two waveguides for a little over $10 - surely it must be cheaper if you buy it by the gallon from a wholesale supplier?MEH said:
What the prototype would be for, would be to make the mold. Once we have a mold, making the waveguides should be relatively easy and inexpensive?
Might take some persistance and ingenuity of course... If someone can provide the CAD file for us (say, Solidworks?), I might be able to get my uncle to let me use his CNC machine to make a mold. (And I know some members have mentioned that they have access to CNC machines at school, or at work)
In the meantime, I'll get some of those small waveguides that Zaph used for his WGTMM speakers, to play with for $8.50 ea.
I like the idea of cutting a scraper to the right shape from a printed template and using something like a pottery wheel (this idea another previous poster mentioned).
EDIT: As long as it costs more than $100 for a pair of 12" wave guides, I don't see it not being worth trying our hand at it, and seeing how clever we can be.
making waveguides
It's always amusing to hear how difficult and expensive it is to make precision waveguides.
I've been making precision microwave waveguides for decades often with sub micron tolerances.. Once a mandrel has been produced, one could electroform multiple copies out of copper, nickel, etc. for not alot of money, especially since in this case the mandrel can be re-used.
Or if a metal horn is undesirable, casting one up in a vacuum casting setup is certainly feasible using readily available resins. There are all sorts of advanced mfg. techniques available to reduce the cost of precision waveguides that are not readily apparent to those not skilled in the mfg. arts. They aren't necessarily found using Google, though.
the issue is where does the original mandrel come from. Hmmnn... maybe a casting of something? Sounds more like an attempt at protecting a trade secret to me.
John L.
It's always amusing to hear how difficult and expensive it is to make precision waveguides.
I've been making precision microwave waveguides for decades often with sub micron tolerances.. Once a mandrel has been produced, one could electroform multiple copies out of copper, nickel, etc. for not alot of money, especially since in this case the mandrel can be re-used.
Or if a metal horn is undesirable, casting one up in a vacuum casting setup is certainly feasible using readily available resins. There are all sorts of advanced mfg. techniques available to reduce the cost of precision waveguides that are not readily apparent to those not skilled in the mfg. arts. They aren't necessarily found using Google, though.
the issue is where does the original mandrel come from. Hmmnn... maybe a casting of something? Sounds more like an attempt at protecting a trade secret to me.
John L.
Attachments
driver integration
I have to get within a couple of inches of my dipoles b4 I can hear the individual drivers instead of the overall sound...
John L.
tinitus said:
I have to get within a couple of inches of my dipoles b4 I can hear the individual drivers instead of the overall sound...
An externally hosted image should be here but it was not working when we last tested it.
John L.
There are some other ways:
Aluminum spinning:
http://www.munciemetalspinning.com/custom.html
tooling can be expensive since you need a large steel form to spin the aluminum over.. basically a negative of the part. you also need a lot of secondary operations to get other non-spun features into the part.
Cast Urethanes. These are based off an SLA master pattern but you then make a rubber mold and cast a two part urethane material in it. You get about 90% of the quality of a molded part and the material properties are MUCH better than SLA.
http://www.quickparts.com/english_Quickparts_2.aspx?Page=/LowVolumePrototypes/CastUrethanes.aspx
In quantities up to about 100, a cast urethane part would probably run close to $100. Custom color and texture included. And you can mold it with even more crazy features than a typical injection mold since rubber molds can be pulled out of undercuts.
Lower up front cost and higher amoritized part cost keeps the producer from paying a lot of tooling charge for a "maybe product".
Aluminum spinning:
http://www.munciemetalspinning.com/custom.html
An externally hosted image should be here but it was not working when we last tested it.
tooling can be expensive since you need a large steel form to spin the aluminum over.. basically a negative of the part. you also need a lot of secondary operations to get other non-spun features into the part.
Cast Urethanes. These are based off an SLA master pattern but you then make a rubber mold and cast a two part urethane material in it. You get about 90% of the quality of a molded part and the material properties are MUCH better than SLA.
http://www.quickparts.com/english_Quickparts_2.aspx?Page=/LowVolumePrototypes/CastUrethanes.aspx
In quantities up to about 100, a cast urethane part would probably run close to $100. Custom color and texture included. And you can mold it with even more crazy features than a typical injection mold since rubber molds can be pulled out of undercuts.
Lower up front cost and higher amoritized part cost keeps the producer from paying a lot of tooling charge for a "maybe product".
Well I would need a CAD file to feed to a CNC machine.MEH said:
Also, I guess a block of aluminum large enough for a 12" wave guide might be expensive?
Perhaps I would want to make the rough shape out of clay, or plaster or such, then use that as a mold for molten aluminum, then use the CNC machine to precision grind it?
When I was a high school kid in the mid/late 1980's I remember one high school near where I lived they had a setup where you could shape sand with some oil in it into a mold then pour molten aluminum into it. The aluminum was so cheap that students could make things for free. I stuck my hand in the sand and made an aluminum hand, I still have it.
If an aluminum block 12" square (or cylinder, perhaps) by however many inches high cost more than $100 or so, then maybe I would be collecting cans on campus Saturday and Sunday mornings for a couple weeks, I could easily get enough aluminum for free that way... I wonder what I'd have to do to melt it at home?
I wonder which types of plastics could be melted and reused, I could probably find that info on the Internet too...
critofur said:
Melt/reuse -> thermoplastic such as polystyrene, polypropylene,
pvc, etc.
http://en.wikipedia.org/wiki/Thermoplastic
Set/nonmelt -> thermoset such as Bakelite, vulvanized rubber, etc
I have access to some reclaimed aluminum alloy ingots that probably wouldn't be very expensive. I could check if you're interested. I'm ~ 2 hrs. SE of Columbus.
You might also consider ZAMAC, pot metal, zinc diecast, etc.
http://www.gizmology.net/stovetop.htm
John L.
tinitus said:Why bother with such "cheap" materials instead of the ultimate, hand layered glass fiber reinforced with balsa or devinycell or honeycomb
Man, I know a turners workshop
He makes wooden art bowls, maybe I should have a talk with himallthough my goal was a squared super elliptical shape
The "cheap" materials would just be for the mold. I would probably then: spray the mold with "release", then "gel coat" then lay down fiberglass/epoxy.
Then behind the fiberglass? Oh, maybe concrete, or, maybe poured epoxy with a high percentage of filler, or even homade MDF made from sawdust and glue? Something "dead" that's both strong and non-resonant.
The reason not to use fiberglass / epoxy for the MOLD would be that I would want some material appropriate for machining with a CNC machine. ZAMAC would fit that bill and be cheap?
Thinking about this way to make a "mold"
Its kind of chinese
A long stick is mounted in the centre of the baseplate(mouth) and the other end of the stick is throath
All the other "plates" have a hole in the centre to match over the stick
In this way its possible to dissmantle to work on the "plates" individually
Eventually its all glued together and finished with filling plaster
Its kind of chinese
A long stick is mounted in the centre of the baseplate(mouth) and the other end of the stick is throath
All the other "plates" have a hole in the centre to match over the stick
In this way its possible to dissmantle to work on the "plates" individually
Eventually its all glued together and finished with filling plaster
Attachments
I don't know how to PM you Ed but there's a typo in your post about Josh's spreadsheet.
You meant to say enter "C10" after the equals sign. I'm no excel guru and I'm definitely not qualified to say whether the output of this spreadsheet is "correct" or not but I thought some people might not notice that was a typo.
You meant to say enter "C10" after the equals sign. I'm no excel guru and I'm definitely not qualified to say whether the output of this spreadsheet is "correct" or not but I thought some people might not notice that was a typo.
What price is acceptable?
I have found a local manufacturer, who is able to make glass or carbon laminate horns from single units to small series, in larger series he would be able to use acryl - the same way bathtubs are made. To get a quote on price, he would need exact dimension/profile and mechanical demands. If there would be enough interest, I could ask him. One problem is, that shipping to US would take a considerable part of the price.
I have found a local manufacturer, who is able to make glass or carbon laminate horns from single units to small series, in larger series he would be able to use acryl - the same way bathtubs are made. To get a quote on price, he would need exact dimension/profile and mechanical demands. If there would be enough interest, I could ask him. One problem is, that shipping to US would take a considerable part of the price.
I've been building horns and waveguides for about 15yrs now. In the first post my method was referenced, which I documented at htguide.com.
If you have the patience, I believe the method outlined here yields superior results:
http://www.diyaudio.com/forums/showthread.php?threadid=117537&pagenumber=5
Keep in mind, it's a lot more work to make the mold out of wood than out of paper.
If you're in a hurry, the paper mold method outlined at htguide yields a usable waveguide mold, and can be done in a single day. The wood mold used for my Unity took easily 30-40 hours to finish. And I've done at least 20-30 waveguides, I'm not a pro but I'm not completely new at this
If you have the patience, I believe the method outlined here yields superior results:
http://www.diyaudio.com/forums/showthread.php?threadid=117537&pagenumber=5
Keep in mind, it's a lot more work to make the mold out of wood than out of paper.
If you're in a hurry, the paper mold method outlined at htguide yields a usable waveguide mold, and can be done in a single day. The wood mold used for my Unity took easily 30-40 hours to finish. And I've done at least 20-30 waveguides, I'm not a pro but I'm not completely new at this
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