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Multi-Way Conventional loudspeakers with crossovers

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Old 11th January 2012, 09:01 PM   #111
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Well, if you ever run out of z travel it's usually pretty straight forward to build your own and bolt it on. Some mic-6 plate, drill some holes in it, get some THK rails surplus from ebay and a ball screw and thrust bearing block and you're good to go for a few hundred dollars. You could likely use your current router to cut the aluminum plate as well.

If you go to cnczone and search in the diy router section, there are a lot of discussions of cheaper cam packages. It's a pretty frequent topic. Vetric, OneCnc, Sprutcam, dolphin cam and bobcam are some others that come to mind. I'd definitely recommend getting demos of any package you are thinking about buying to see how you like it. I tried a few before I settled on visual mill. Vetric makes some packages that are very popular on cnczone with hobbyists, but it would not quite do what I wanted to with cutting 3d shapes.
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Old 11th January 2012, 09:31 PM   #112
sploo is offline sploo  United Kingdom
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Originally Posted by John Sheerin View Post
I've got a 3 phase 5hp water cooled spindle that I need to get mounted and try them in though.
Now that, for me, is porn

Porter Cable router in the existing setup? Yea, I'd be wary of 6" long bits in that. Run an 892 myself.


Quote:
Originally Posted by ShinOBIWAN View Post
The machine has 200mm of z travel and the maximum part depth I plan to machine is 84mm. Obviously I'll need a cutter length of slightly more than that and then factor the collet depth and work piece clearance. Its do-able but sometimes I wonder if I should have taken the 300mm option but the price keeps on going up...
And the cost of the tools gets very high too. I have spiral ball nose bits, but generally only <=1/4". In the UK it's slightly easier to get metric bits, but routers generally only do 1/4", 1/2" and 8mm.

Remember that you may get away with a shorter bit if you can always guarantee clearance when cutting (the router or collet won't clip other parts when cutting). I.e. you could cut a 100mm deep landscape model with a 25mm long endmill, if the gradients were always shallow enough to ensure clearance.

I have recently discovered SuperPID: www.SuperPID.com - Super-PID Closed-loop Router Speed Controller, which may be of interest to CNC guys. I note some Bosch routers claim constant speed control, which I guess may be using the same sort of tech. The issue with the routers is they're designed to give power at max rpm. At slower rpms they just voltage chop, which reduces the torque so badly you risk stalling them. Unless you're prepared to set up 3 phase and drop $$$ on a VFD and spindle.
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Old 11th January 2012, 10:24 PM   #113
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How noisy are those spindles you can get on ebay?

The biggest problem with my small DIY router is the cheapy router SCREAMS. It's insanely loud, and it takes me 4 hours to machine a fancy 3D baffle. But it is the only one with a 44mm collar, which makes it easy to bolt in.

I have found that 130mm travel is enough for anything I want to do - but you end up designing your parts to suit your travel. I can only cut 600x700ish single setup (but can move long parts through). So I designed my side panels to fit the table and broke them up with styling gaps.


That spindle speed controller looks very interesting, thanks Sploo. Running slower would help with the noise issue.


Movie of my Router cutting the tweeter speaker baffle here (TURN YOUR SPEAKERS DOWN!!):
http://dl.dropbox.com/u/1372034/Rout...r%20baffle.3gp

Last edited by Mark_A_W; 11th January 2012 at 10:43 PM.
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Old 11th January 2012, 10:47 PM   #114
sploo is offline sploo  United Kingdom
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Quote:
Originally Posted by Mark_A_W View Post
How noisy are those spindles you can get on ebay?

The biggest problem with my small DIY router is the cheapy router SCREAMS. It's insanely loud, and it takes me 4 hours to machine a fancy 3D baffle. But it is the only one with a 44mm collar, which makes it easy to bolt in...
Can't comment on ebay spindles (I expect there are many). In general, I understand a good spindle can be run at a much lower rpm, due to being controlled by a Variable Frequency Drive (VFD) and supplied with 3 phase power. I'm not an electronics/electrics guy, but a mate who is explained to me that dropping the frequency of a standard single phase supply to a router would just burn out the motor - hence the router speed controllers chop the AC wave, but lose torque as a result. The spindles maintain good torque at those low speeds, and are thus much quieter & don't stall.

From the figures I hear from the guys running industrial CNC set ups, the DIY guys (like me) are running way too high rpm and way too low feed rates. The problem is that an aluminium machine won't handle high linear speeds, but you can't lower your rpm to compensate as your router will stall. You'll find spindles are often lower hp, because it's about torque not rpm (hp rises linearly with rpm, given constant torque).

I get decent results at ~17,000rpm with a 2.25hp Porter Cable 892, cutting at 120ipm (2 inches/sec) with a 1/4" carbide upcut spiral bit with 1/4" Depth Of Cut (DOC) in MDF. I'll lower the DOC for larger bits or harder material.

I recall talking to a guy who was doing 3/4" DOC at ~7 inches/sec with a 1/2" diameter bit in MDF. 7hp spindle .
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Old 11th January 2012, 11:21 PM   #115
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I'm cutting at 500mm to 4000mm per minute.

I take reasonably small cuts as my router is belt drive for X and Y, 3mm depth max. About half what you are doing, but my router is cobbled together.


One issue I have is I can't run slowly that well due to the ebay stepper card starting to pulse - remember with belt drive my steppers are not geared down like a leadscrew. So I stay fast.

Anyway, it WORKS, and it cost me bugger all as I scrounged all the parts. Noise is the only real issue.


I can't think in inches....120 ipm is 3000mm/min....isn't the UK metric?
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Old 12th January 2012, 09:08 AM   #116
sploo is offline sploo  United Kingdom
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Quote:
Originally Posted by Mark_A_W View Post
I'm cutting at 500mm to 4000mm per minute.

I take reasonably small cuts as my router is belt drive for X and Y, 3mm depth max. About half what you are doing, but my router is cobbled together.

One issue I have is I can't run slowly that well due to the ebay stepper card starting to pulse - remember with belt drive my steppers are not geared down like a leadscrew. So I stay fast.

Anyway, it WORKS, and it cost me bugger all as I scrounged all the parts. Noise is the only real issue.

I can't think in inches....120 ipm is 3000mm/min....isn't the UK metric?
Having a distinct "I've hijacked Ant's thread" feeling . Perhaps we should start a "CNC for loudspeaker building" thread.

Yes, 120ipm is 3000mm/min. UK is schizophrenic, depending on your age. We drive in miles, fill the car in litres, buy beer in pints, milk in litres & inflate tyres in psi. My machine is from the US, so while I work in metric, a lot of my original understanding of the machine comes in imperial. My cutting bits are 6.35mm and 12.7mm and 3.175mm and 2.38125mm, and MDF is 19.05mm thick (3/4") etc. etc. Gets a bit tedious.

Yea, steppers do cause issues. I'm running servos, but they're much more pricey. If I built a machine myself, I'd probably go with chunky steppers and maybe rack and pinion drives for the X & Y to make an 8x4' (2.4x1.2m) machine. Just lacking the space, or the time, or the cash
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Old 12th January 2012, 09:33 AM   #117
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Yup, hijack.

But the possibilities opened up by owning a CNC machine for loudspeaker building are endless
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Old 12th January 2012, 11:13 AM   #118
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Quote:
Originally Posted by sploo View Post
buy beer in pints
"Could I have 568ml of your finest ale!" Doesn't have the same ring about it does it.
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Old 12th January 2012, 11:21 AM   #119
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Quote:
Originally Posted by sploo View Post
Having a distinct "I've hijacked Ant's thread" feeling .
Nah no way. Its very interesting and great as a beginner.

I have some questions but I'm a little afraid they're too dumb to ask.
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Old 12th January 2012, 11:57 AM   #120
sploo is offline sploo  United Kingdom
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Quote:
Originally Posted by ShinOBIWAN View Post
I have some questions but I'm a little afraid they're too dumb to ask.
There are no dumb questions. Only dumb answers... grasshopper. etc.

Fire away. I had loads of "well how on Earth is that gonna work?" questions when I started CNC. Plus the fact that experience is usually accompanied by a loud noise, smoke, and big bill...
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