Cylindrical/polar cnc mill for loudspeakers

Good evening good folks

My name is Daniel and I live in Copenhagen.

I have a background as an electrician and after a trip to university I now work as an engineer doing electro-acoustics.

I am thinking about building a mill to make loudspeaker horns. In their simplest form they are axi-symmetric, so a type of lathe might be well suited, but many are elliptical or have other shapes that are challenging to turn on a lathe.

As I am a newbie in this field of engineering I am looking for some guidance.

Materials
MDF, birch plywood, high density foams.

Construction
As much as possible out of alu profile, Bosch rexroth or similar. Special mounts, end plates etc. made to fit.

Control
My layout calls for a machine that works in cylindrical/polar coordinates, which I'm slowly realising might be quite difficult to realise as a DIY project. I have started to look into controllers and software and such, but it takes some time to dig through it all. Does this call for a 4 axis controller?

Motion
Are Clearpath servos any good, what about DMM. Then there are the Acorn boards. What type of SW do I need. There are a lot of questions that I am beginning to wrap my head around, but I'm far from done wrapping.

Performance
I would like to be able to have a make a horn in the order of 600mm diameter, 300mm depth. I realise that a solid block of wood that size will be quite heavy. So i'm planning to maybe stack rings of wood to create the rough shape and then do the finishing work on the machine.
How about accuracy? Well better than 1mm is acceptable, this is wood after all. I mean 1/10mm is even better, but anything less is a waste of time with wood IMO.

Design
I have a made a rough sketch of the layout here:
Attachment 29683

Slowly learning about FUSION360

This is a typical example of a mesh of a horn:
Attachment 29684

Recomendations
Is this coordinate system doomed to fail?
How much travel is possible for the spindle axis before it starts wobbling, should it be horizontal?


Thanks for your time, I realise that there is not much to go from, but any critique is welcome.

Daniel

I wouldn't worry about polar coordinates, I've designed and machined/had machined a number of horns from 3D models on normal 3 axis CNC without any problems; some (for tweeters) that needed quite fine and accurate details. Much quicker and easier to go with hardware that's easily available and let the CAM software do the work IMHO.

Quote:

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Originally Posted by Voicecoil

I wouldn't worry about polar coordinates, I've designed and machined/had machined a number of horns from 3D models on normal 3 axis CNC without any problems; some (for tweeters) that needed quite fine and accurate details. Much quicker and easier to go with hardware that's easily available and let the CAM software do the work IMHO.

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Yeah, I've sorta come to the same conclusion since I posted :)

Hi Copenhagen_41 - I'm an applications engineer with Teknic, the designer and manufacturer of the ClearPath motors you mentioned in your post.

While I'm not an Acorn CNC user, I have worked with several companies that have successfully used ClearPath motors (SDSK/SDHP family) with an Acorn CNC controller. If you decide on ClearPath motors, I'd recommend that you look at the SDSK family of motors (https://www.teknic.com/products/clea...r-replacement/).

There are many helpful videos regarding the integration of ClearPath with the Acorn CNC controller available on YouTube. I especially recommend you check out the SYIL4 mill servo upgrade project at Marty's CNC Garage (https://www.youtube.com/playlist?lis...QoORpYX59Nqy7J). There is also quite a bit of information available on Centroid's website.

If you need some assistance with picking a specific ClearPath motor, feel free to call us directly or leave us a message at https://www.teknic.com/contact/.

I hope this helps and we wish you the best of success with your project.

Best regards,
AbeA - Teknic Servo Systems Engineer

Quote:

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Originally Posted by Copenhagen_41

Good evening good folks

My name is Daniel and I live in Copenhagen.

I have a background as an electrician and after a trip to university I now work as an engineer doing electro-acoustics.

I am thinking about building a mill to make loudspeaker horns. In their simplest form they are axi-symmetric, so a type of lathe might be well suited, but many are elliptical or have other shapes that are challenging to turn on a lathe.

As I am a newbie in this field of engineering I am looking for some guidance.

Materials
MDF, birch plywood, high density foams.

Construction
As much as possible out of alu profile, Bosch rexroth or similar. Special mounts, end plates etc. made to fit.

Control
My layout calls for a machine that works in cylindrical/polar coordinates, which I'm slowly realising might be quite difficult to realise as a DIY project. I have started to look into controllers and software and such, but it takes some time to dig through it all. Does this call for a 4 axis controller?

Motion
Are Clearpath servos any good, what about DMM. Then there are the Acorn boards. What type of SW do I need. There are a lot of questions that I am beginning to wrap my head around, but I'm far from done wrapping.

Performance
I would like to be able to have a make a horn in the order of 600mm diameter, 300mm depth. I realise that a solid block of wood that size will be quite heavy. So i'm planning to maybe stack rings of wood to create the rough shape and then do the finishing work on the machine.
How about accuracy? Well better than 1mm is acceptable, this is wood after all. I mean 1/10mm is even better, but anything less is a waste of time with wood IMO.

Design
I have a made a rough sketch of the layout here:
Attachment 29683

Slowly learning about FUSION360

This is a typical example of a mesh of a horn:
Attachment 29684

Recomendations
Is this coordinate system doomed to fail?
How much travel is possible for the spindle axis before it starts wobbling, should it be horizontal?


Thanks for your time, I realise that there is not much to go from, but any critique is welcome.

Daniel

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