Making horns.

[simonms]

Hi Everyone,

Just joined the forum in hope of some advice on machines that may suit my purpose.

I make loudspeakers and at present the mid range horns are commissioned, here is a picture of how they come in.

DSCN1737 by mearssimon, on Flickr

They are made from 18mm layers of ply, joined on dowels and glued then sanded back. The sanding takes some time to get the steps out before they are sufficiently smooth.

The top 2 123d make images are the horns that I am now looking to make (different shape). I have had quotes to have then done on a 5 axis machine (expensive) and also on 3 axis in 2 halves joined down the center and smoothed inside and out.

I want to cover all my options and may consider buying a machine, I have a budget of £7-8K.

Any advice would be most welcome,

Many Thanks,

Simon.

[simonms]

Sorry for the double post. Please feel free to remove the other one mods.

[EddyCurrent]

Is wood your best option ?
Also are they that shape for acoustic reasons or just for the looks ?

[Boyan Silyavski]

The inherent problems of acquiring 5 axis machine is: price and software, so i would forget about that.

It seems to me what you need is precise and sturdy machine, which is well within your budget. Size wise it will be good idea to make all loudspeaker parts with it.

So if you make the part from 2-3 pieces machined cleanly with ball nose bit and glue them together, you will be left with only minor finishing job.

Or once you know that the shape is right you can machine yourself molds and make the parts from epoxy for example, or whatever. There are many many things that come to my mind. MDB or wood and then epoxy impregnate and so on...


PS. Of course i would start doing it the way you have done it till now. Just use 3d paths and ballnose. So when all goes together it will need only minor sanding. If i am not mistaken looking at your photos, it was used 2.5D path not 3d. On your pictures it looks like a 2.5D path or 3d roughing pass, not 3d finishing pass which would leave all super smooth

.

[simonms]

Thanks for the replies, the horns are machined in wood as it offers the best sound and the profiles are specific for drivers used. The other loudspeaker parts are run through saws and veneered but it may be an option to consider as the biggest panel is 1000 x 520mm.

Sturdy, precise, that's what I am after as it will mainly be used for machining the horns, I have had a brief look through the site here and EXEL seem well though after. I am a novice with regards to CNC so is the consensus that it is possible to make these horns leaving say a 240 grit sand and finish or am I asking too much. Any advice on particular machines they may recommend for this purpose?

[EddyCurrent]

I'm not sure you would get away with 240 grit and here's why. If you think about the cutting tool, probable a ball mill where the end is rounded, and imagine it cutting tiny furrows in the material, then the amount of stepover you give it will determine how far it moves across to cut the next furrow. So if the furrows are very close together it will take a very long time to cut and at some point there is a trade off between time to cut and desired finish. There's not a great choice of UK made machines, Exel was the one I was going for before deciding to make one.