Apollo Construction Diary

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diyAudio Member
Joined 2004
Hey folks,

I'm waiting on about 90kgs worth of lead that will be used to damp the interior walls of the Apollo cabinets but in the meantime I've been busy creating lots of tool paths for the 3 baffles used in the One.10, 20 and 30 models.

They'll be machined out of 100mm PU high density modelling block and serve as the master from which a silicone rubber mould will be made. Why go to all this effort? Well it will allow for some pretty wild experimentation with casting materials. I'm going to start off with a high density PU resin mixed with aluminium trihydroxide filler for extra mass, using this combination its possible to create a composite with a density similar to corian(around 1700kg/m^3) but without the huge price tag and hassle of laminating many 12mm sheets to build up the final thickness. I'll see how that performs but really anything is possible including concrete and epoxy with a wide range of fillers or reinforcement. Really excited about that part.

Extending this technique to the cabinet portions and not just the baffles would be something I'd like to do eventually too. It'd allow for some creative ways of tackling internal reflections. Probably the biggest advantage of casting the enclosure would come from it being formed from a single block of material with no joints. A nice side effect is you can go to town on the styling too.

Anyway that's a ways off and I'm going to focus on the baffles first. Here's the first half of the mould created from the master.
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One very handy feature of an integrated CAD/CAM package is the ability to create a model of the CNC and this can be used to check for clearance and collisions with hold down parts such as clamps and screws. I wouldn't say its fool proof but the simulation does let you see problems before they happen for real.

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diyAudio Member
Joined 2004
Now that there's some hours on the CNC and things are bedding in I decided to spend the day stripping down and removing all the ballscrews and nuts carefully putting them back together getting everything as tight and aligned as possible. Result is there's virtually no bind anywhere now and it shows in the speeds and acceleration it can achieve. Those Leadshine AM882 are awesome! I could have gone past 16.5m/min but Mach was limited by my max 45k PP speed so I went and whacked the acceleration all the way up to 4000mm/sec^2 instead lol

Ps. I don't run at these speeds or accel as its overkill but its nice to see the effort from careful setup confirmed with a speed increase. For regular use I run at 10m rapids and 5m on the Z with relatively high acceleration. That's more than enough for me but its nice to know there's head room there because steppers do like some margin to avoid losing position.

Leadshine AM882 performance on CNC - YouTube
 
diyAudio Member
Joined 2004
Had another go at making a dust shoe and after picking up some cast acrylic this attempt came out much better. A week or so ago I did try to cut the same parts out of extruded acrylic and that stuff melted no matter what I did. Lesson learned - go with cast if the finish quality matters.

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Hey folks,

I'm waiting on about 90kgs worth of lead that will be used to damp the interior walls of the Apollo cabinets but in the meantime I've been busy creating lots of tool paths for the 3 baffles used in the One.10, 20 and 30 models.

They'll be machined out of 100mm PU high density modelling block and serve as the master from which a silicone rubber mould will be made. Why go to all this effort? Well it will allow for some pretty wild experimentation with casting materials. I'm going to start off with a high density PU resin mixed with aluminium trihydroxide filler for extra mass, using this combination its possible to create a composite with a density similar to corian(around 1700kg/m^3) but without the huge price tag and hassle of laminating many 12mm sheets to build up the final thickness. I'll see how that performs but really anything is possible including concrete and epoxy with a wide range of fillers or reinforcement. Really excited about that part.

Extending this technique to the cabinet portions and not just the baffles would be something I'd like to do eventually too. It'd allow for some creative ways of tackling internal reflections. Probably the biggest advantage of casting the enclosure would come from it being formed from a single block of material with no joints. A nice side effect is you can go to town on the styling too.

Anyway that's a ways off and I'm going to focus on the baffles first. Here's the first half of the mould created from the master.
attachment.php


One very handy feature of an integrated CAD/CAM package is the ability to create a model of the CNC and this can be used to check for clearance and collisions with hold down parts such as clamps and screws. I wouldn't say its fool proof but the simulation does let you see problems before they happen for real.

Very interesting! Im thinking of doing the same on my next speaker project! Where do you plan to get all the moulding material? And also the aluminium trihydroxide, im having a really hard time finding it! The only site that sells it dosen't seem to have it in stock.. I think i will order this kit: Silicone Mould Resin Casting Starter Kit with Fast Cast Polyurethane Resin - Easy Composites
To start experimenting a little bit! What do you think about maybe putting a layer of gelcoat before the resin to get a high gloss surface?

/Sebastian
 
Had another go at making a dust shoe and after picking up some cast acrylic this attempt came out much better. A week or so ago I did try to cut the same parts out of extruded acrylic and that stuff melted no matter what I did. Lesson learned - go with cast if the finish quality matters.

Watch your static build-up with that Ant. When I first set up something like that I noticed it was arcing small sparks to the router body after a while!

Now I have a cable connected to the metal wire in the hose, which is then earthed.
 
diyAudio Member
Joined 2004
Very interesting! Im thinking of doing the same on my next speaker project! Where do you plan to get all the moulding material? And also the aluminium trihydroxide, im having a really hard time finding it! The only site that sells it dosen't seem to have it in stock.. I think i will order this kit: Silicone Mould Resin Casting Starter Kit with Fast Cast Polyurethane Resin - Easy Composites
To start experimenting a little bit! What do you think about maybe putting a layer of gelcoat before the resin to get a high gloss surface?

/Sebastian

I've used these so far and have been happy with the service from each. Easy composites are particularly good. Gave them a call, explained what I wanted to do and they gave lots of helpful advice.

Carbon Fibre Cloth, Epoxy Resin, Kevlar, Diolen, Equipment and Supplies for Advanced Composites - Easy Composites

Mould Making and Casting Supplies from Bentley Advanced Materials

TOMPS : Mould Making Supplies : Casting Supplies : Plasterers Supplies

For the gel coat I'm not bothering as the cast will be sprayed anyway but if your looking for the best finish straight out the mould then that would give a high gloss and hard durable surface.

Aluminium Trihydroxide is also known as Trihydrate or ATH. Some info here:

Aluminium Trihydrate - Alumina Hydrate, Aluminium Hydroxide, Aluminium Trihydroxide from aluminahydrate.com

Try using those to widen your search but I know these sell it and had it in stock a month or so ago:

ATH - ALUMINIUM TRIHYDRATE
 
diyAudio Member
Joined 2004
Not normally worth posting about replacing the bed but I picked up a sheet of Trespa Athlon from a friend and have to say this is makes a great bed. Plenty of mass(about twice as heavy as MDF on a like for like basis), well damped against vibration, dimensionally stable, tough and still easy to drill and set up fixtures. The construction is a fibre reinforced resin with a laminated finish. I've had a quick go with an offcut made when sizing the sheet to fit the bed and it machines really nicely.

Aside from making a good bed all this has got me thinking it'd be ideal for speaker construction. I got this sheet for nothing and I'm not sure on pricing but I'll find out.

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My modelling board arrived today. Weighs a ton! The masters for the baffles will be coming out of this soon.

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My modelling board arrived today. Weighs a ton! The masters for the baffles will be coming out of this soon.

If that modelling board is the same material I got hold of (offcuts from a CNC company near where I used to work) you'll love machining it. It cuts like butter, creates chips not dust, and you get incredibly sharp, clean edges that require little or no finishing. It will dent, so needs handling with a bit of care, but is great for prototypes and mold making.
 
diyAudio Member
Joined 2004
This was a cool challenge not least because there was over £300 worth of stock material at risk if I nobbed it up!

A couple of days worth of planning, many iterations of tool paths and simulations and a day spent building and testing the double sided jig. This made a really nice change of pace from the usually slap a sheet of 4x4ft on the bed and press go. I've only had practical hands on experience with the cnc for the past few weeks and only done a handful of jobs so at time I thought I'd bitten off more than I could chew with this but it came good in the end. The two sides lined up virtually perfect and I couldn't be happier with the results. I learnt a lot from this, not least that long cutters (105mm from the collet) are whole other ball game and first hand experience of the superiority of carbide vs hss when cutting highly abrasive materials as well as the folly of using too many flutes and incorrect chip load. Burned two cutters up because of that just on this one job.

I'll post some of the pics later but for now here's a video:

CNC Cutting Loudspeaker Baffles - YouTube
 
This was a cool challenge not least because there was over £300 worth of stock material at risk if I nobbed it up!

A couple of days worth of planning, many iterations of tool paths and simulations and a day spent building and testing the double sided jig. This made a really nice change of pace from the usually slap a sheet of 4x4ft on the bed and press go. I've only had practical hands on experience with the cnc for the past few weeks and only done a handful of jobs so at time I thought I'd bitten off more than I could chew with this but it came good in the end. The two sides lined up virtually perfect and I couldn't be happier with the results. I learnt a lot from this, not least that long cutters (105mm from the collet) are whole other ball game and first hand experience of the superiority of carbide vs hss when cutting highly abrasive materials as well as the folly of using too many flutes and incorrect chip load. Burned two cutters up because of that just on this one job.

I'll post some of the pics later but for now here's a video:

CNC Cutting Loudspeaker Baffles - YouTube

Wow! Will you then pour silicone on that to make the moulds? Thanks for the links btw! I will receive my "kit" tomorrow hopefully, then i will start to experiment with fillers, marble powder and metal powders! I't would be pretty badass to have a brass like baffle!
 
This was a cool challenge not least because there was over £300 worth of stock material at risk if I nobbed it up!

A couple of days worth of planning, many iterations of tool paths and simulations and a day spent building and testing the double sided jig. This made a really nice change of pace from the usually slap a sheet of 4x4ft on the bed and press go. I've only had practical hands on experience with the cnc for the past few weeks and only done a handful of jobs so at time I thought I'd bitten off more than I could chew with this but it came good in the end. The two sides lined up virtually perfect and I couldn't be happier with the results. I learnt a lot from this, not least that long cutters (105mm from the collet) are whole other ball game and first hand experience of the superiority of carbide vs hss when cutting highly abrasive materials as well as the folly of using too many flutes and incorrect chip load. Burned two cutters up because of that just on this one job.

I'll post some of the pics later but for now here's a video:

CNC Cutting Loudspeaker Baffles - YouTube

Ant - superb work. Though there are some movements (e.g. around the 30-40s mark) that look a little slow for the cutting rpm and would risk heat problems.

That 105mm cutter is a monster. I'll bet the deflection problems were interesting.

Like the idea of having a couple of baffles along the length of the machine so the chips are kept on the table, rather than falling onto the rails.

BTW Scare me - how long did that whole job take?
 
Its a bunch of clever macro's and a matching screenset for Mach3 and two touch probes - one mobile for setting the initial work piece zero and a fixed plate for measuring tool length between changes. Dead easy to use and I have no issues with changing up to 7 bits in one job. The only inconvenience is have to change your bit but unless you get a megabucks auto changer and mega-mega bucks ATC spindle then this is as good as gets.

Link to the screenset:

The CNC Woodworker - Mach3 2010

Its about £13 but the best money I've spent on the CNC by far.

Here's a nice video that shows how it all works:

Mach3 2010 Screenset Tool Change - YouTube

Hi Shin,

Sorry if it's OT but I just want to ask you the software version of your Mach3, are you using 3.43.66? or 3.43.62?
 
I'll post some of the pics later but for now here's a video:

CNC Cutting Loudspeaker Baffles - YouTube

Nice! :cool:

'tis a lot of dust though, no? :D

I still think the better idea is a continuous stream(s) of compressed air at the bit/work area scattering the debris to the edges of the work surface (..with a vacuum pick-up from there). And though speculative, I'd still imagine that compressed air streams would cool the bit (a "bit") and prolong bit-life. (..again, similar to what heavy industry machines use with liquid for metal milling.)
 
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