Building an enclosure

No, one on each side to drive the overhead Carriage more evenly. Having one motor means that there could be a tiny amount of flex on the side that’s not driven. I know this isn’t a huge issue but in the future I’d like to

There are already two motors on the Y-axis, which are automatically counter-rotating — where else would you want to add one?

FWIW, I put a drive shaft on the Y-axis of my Shapeoko 1.

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Wait that?

The entire overhead carriage is driven by one motor in each side? I thought just one side was driven???

The Y-axis carriage plates are mirror images, each w/ a motor which are set up to counter-rotate:

What you’re doing there is very similar to what people try to do with home music studios. Basically there’s two aspects to dealing with sound,

  1. Managing reflection and reverberation to manage the sound within a space
  2. Absorbing or isolating the sound energy to reduce the leakage out of the space.

I can’t recommend this guy enough as a starting point to understand how this stuff works, he’s a real pro and talks sense not expensive products.

I’m a bit of an audio nerd so I’ve already got some strategically placed audio panels and bass traps to clean up the sound in my room. I’ve also done the measurement and fighting in a friends studio to try to position the monitor speakers properly to avoid the worst 1/4 and 1/2 wave resonances and level out the sound as much as possible before electronic EQ. If you put the noise making device in any of the ‘wrong’ places in a room it will just resonate and nothing you do will usefully damp that noise inside or outside the room compared to just altering the resonance modes.

As for construction materials… Wow, that a rabbit hole, if you go look at forums like gearslutz you’ll find an easy years worth of reading and argument on that topic.

In summary…

Mass is what stops sound, then isolation, but it really needs to work, sound leaks through tiny gaps. Rockwool is really not that effective because it doesn’t have enough mass to do much absorbtion in realistic thicknesses, stud walls are mostly transparent to sound because they transmit the sound through their rigid frames. floating floors and stud walls with separate frames for each side of the wall start to isolate the sound.

For a sound absorbing material, foams and egg-crates are just useless, regular rockwool isn’t much better. There are much heavier grades of rockwool which are used to make sound deadening panels, GIK acoustics sell both the panels and the materials. The panels I have are GIK. You can locate the heavy duty rockwool but not at your local building supplier.

There’s also a whole plethora of domestic sound absorbtion products which you might want to look at. These typicall work on a mixed heavy layer and spongy layer sandwich approach. This is what you could put under a ‘floating’ bench top for your machine.

I made a box to keep my shop vac in, but it has an outlet which let me put a 4" hose on the exhaust to go out a window, I also put a cyclone settler on the input to keep the worst of the dust out of the vac. It makes quite a lot of difference.

If you want to keep the noise inside the room I’d suggest using something heavy as the supports for the Shapeoko, even concrete paving slabs would be worth considering along with one of those floor isolating products and then use proper industrial grade vibration isolating mounts to isolate that frame from the floor. A few people here have used vibration absorber / isolator mounts between their machine and the table too, that’s a good double strategy if there is enough mass in the table.

HTH

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I’m surprise no one mentioned dynamat it’s super cheap and very very heavy. It’s basically a layer of very thick aluminum foil and an asphalt adhesive. The result is a very sticky and heavy surface and these can be easily layered up. A 50 Sq/ft foot box which I would need to for my enclosure at least would weigh about 40 pounds each.

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Dynamat may help with some aspects but be careful which type you use. Just adding mass to the system may not provide the results we want.

The popular Dynamat (and similar other vendor products) are designed as constrained layer damping materials to deal with vibration energy in relatively stiff metal panels. The idea is that the metal skin on the mat and the metal panel of the vehicle form the sandwich for the deformable layer of goop. The goop goes into a shear mode as the panels flex and converts the sound energy to heat. This is very effective, if you have a thin metal panel which is flexing sufficiently to move the goop into it’s shear mode where it converts stress to heat and out of it’s nominal elastic mode. It’s hard to get this right and using a material designed for thin metal panels in vehicles on a sheetrock, plywood, MDF etc. wall is unlikely to work.

The common ‘knockoff’ clones which are just a heavy rubbery or bitumen material generally only serve to reduce the resonant frequencies of panels they’re attached to by increasing the mass without increasing stiffness, thus their use inside speaker cabinets to move midrange resonances to less objectionable octaves.

The multi-layer dense foams can work like the dense rockwool in terms of reducing transmission of noise, they’re also pretty good at reducing reflection of higher frequency noise.

Different frequency ranges;

Dealing with different frequency ranges requires different approaches and a combination of absorbtion and decoupling is generally required to get good performance across the audible range.

At mid to high frequency (router noise, spindle whine etc.) relatively thin sound absorbers such as the Dynamat foams on the inside of an enclosure can be very effective. Many folks have built enclosures for their Shapeoko with acrylic windows to view through and these still disrupt the high frequency elements quite effectively.

This is because short wavelength sounds are much easier to absorb and disrupt. That’s why when you close a door or go downstairs from the party you’re left with the thump thump thump, bass just wafts through most things due to longer wavelengths and reduced absorbtion efficiency. Bass sees wooden floors and joists as a propagation path, not a barrier.

Once we get to lower frequencies and longer wavelengths mechanical transmission becomes the issue. You could fill the enclosure with absorbing dense foams and the people downstairs would hear the axis moves and low frequency elements of the cutting noise perfectly because the sound is transmitted through the feet of the Shapeoko to the table, through the legs to the floor etc.

To deal with these lower frequency elements we need to find a way to stop the low frequency energy propagating from the machine to the walls, floor etc. There’s two parts to this, direct noise conduction through the frame and sound passing through walls etc.

Low frequency sound is normally mitigated by decoupling, which works best when a flexible coupling is carefully tuned between the two masses to not pass the problem frequency range.

We’re not really in a position to calculate this so what we need is something rubbery which will support the machine effectively but flex in the low frequency range rather than passing vibration to the floor. There are assorted anti-vibration feet and similar products out there, the key is flexible couplings between masses.

As for walls, there’s lots of stuff out there but fundamentally, the things that work in lower frequencies are decoupling, not absorbing, split stud is popular as it’s not much more space than a regular stud wall.

The key thing is to deal with the noise as close to source as possible so an enclosure around the Shapeoko, maybe double-skinned (without battens linking the skins across their faces to reduce transmission) and fill the cavity with Dynamat foam absorber etc. (not the aluminium constrained layer materials) would work for the higher frequency sounds. Next up, isolate the low frequency noise, vibration isolating feet under the shapeoko are an option but require some experimentation to not add lots of harmful vibration to the Shapeoko frame. Sound isolating feet between the table and the floor are likely the best option and I’d be tempted to use a few concrete paving slabs on the floor as the resting point for the vibration isolating feet.

You could also do a double table top with a small torsion box for the Shapeoko to sit on which itself sits on a layer of the foamy floor insulating Dynamat on top of the lower table top which is attached to the legs. Not sure how well this would work, depends on the effective tuning of the mass and the springiness of the foams but I’ve done this type of isolating for noisy air conditioning units to good effect.

HTH

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I should probably mention that I built speakers and I also have an 1100 page book on HIFI horn design so I completely understand everything you’re telling me about sound absorption and how lower frequencies tend to past and move through walls and higher frequencies act more like lasers are very direct and reflect a lot. I just made the table I could probably put some of that dynamat in between the top layer of wood that shapeoko sits on and the 2 x 4 frame that The table top is screwed onto. This should at least help dampen some of the vibrations. It’s sitting on a carpet floor so that definitely would help.

I already have a 1.5 kW water cooled spindle so I won’t have to deal with router noises the only problem is the cutting noises. What I’ll probably do is use three-quarter inch thick Baltic Birch or maple ply, add two layers of Dynamat, and then a 1” or 2” layer of rigid foam insulation. I think that that should pretty much cover the frequency spectrum and allow me to absorb most of the sounds. This entire contraption is all housed in a 7‘ x 7‘ walk-in closet so A lot of the sound won’t be leaving that room.

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first off, thank you for giving me such a detailed reply! ’

second, I think some of the things you’re mentioning are a little overkill. I can not get concrete paving slabs in my room and the table is in my closet, which is above the garage so noise below me isn’t a problem.

I just want a simple solution that will cover most of the frequency range. a “one size fits all panel”.

if you had to design a simple panel of layers/sandwiched materials (no split studs), how would you design it.

Im thinking two layers of 1/2" thick plywood with sound dampening glue in-between, a layer of dynamite, and some rigid foam spray painted white.

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That might have the opposite effect from what you’re looking for.
:wink:

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Hey, you wouldn’t hear the router spindle :wink:

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NP, there’s lots of stuff there, more a sort of menu of what could be done so you could see which bits might work in the space you have.

Let me have a proper think about this tomorrow.

I know there’s a bunch of people on the forum here have made enclosures for their machines and will have practical experience of how much sound they contained.

I watched a bunch of YT vidoes whilst waiting for mine to arrive to see what people said about noise with and without their enclosure. Winston built one, those where you get to hear the machine are helpful.

It seems that a lot of the higher frequency noise is damped out by just being in an enclosure, my garage vacuum for dust extraction made more noise than my Shapeoko until I put that in a box to reduce the noise.

BTW,

Are you the same person who asked about making horn speakers before the forum server had it’s issue?

Yes I am the same person to ask that question about the speaker horns. And yeah my CNC will be in a walk-in closet one of the walls faces the outside of the house the other wall Face is in the closet in the other room so the sound should be pretty well contained just because of where the CNC is located.

Ah great, building speakers is an excellent pasttime, I wholeheartedly support it.

So, you’re after an XXL to go in the closet and cut plywoods and hardwoods?

What options do you have to ventilate the closet to outside for heat / dust extraction exhaust?

Do you have access to a track saw or table saw for making long straight cuts to build things like a torsion box?

Does the closet have a wood or slab floor?

I have a circular saw and some rails and clamps to cut them reasonably straight.

I have an 1100 page book on hifi horn design that I’m going through with a mentor of mine. It uses lots of differential equations as well as lots of calculus. I’ve only taken up to calc 1 and I’m gonna be taking Calc to Calc three and differential equations in the coming years for my degree. Right now I’m just focused on getting the enclosure made all the water pump accessories for my spindle (1500 watt water cooled) and a dust extraction system going.

I just made the table I could probably put some of that dynamat in between the top layer of wood that shapeoko sits on and the 2 x 4 frame that The table top is screwed onto.

I’m not an expert but as far as I know when it comes to vibrations, rather than use a large pad to cover the entire area, you want to minimize contact with the surface below in order to decouple the two surfaces.

For my Nomad, I did this with long strips of a specialty foam that held my enclosure ~10mm away from the bench underneath.

It’s a long time since my maths was good enough to engage the maths for horns, that’s quite serious stuff, well suited to computational modelling.

Another excellent read on sound recording, reproduction and how humans actually perceive sound, all backed up with real science is Floyd Toole’s book.

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So, as promised, here’s some thoughts on how you might put together a reasonably non-housemate aggravating Shapeoko XXL. I’ve been thinking about how I’ve quietened machines and rooms in the past and how those tricks might be adapted.

So, first off, an XXL in a 7 foot by 7 foot room;

In terms of approach, I’d suggest that we try to absorb the noise at source or stop it propagating out into the room, it’s almost always best to do this when you can isolate the noise source. I think this will also be helpful in sawdust containment, one guaranteed thing about milling lots of plywood and hardwood is that you’re going to make a lot of sawdust, not all of it will be captured by the extraction system and an enclosure will help keep the mess inside.

The first thing is a solid base for the Shapeoko to sit on, I’m in the process of bolting mine down to the torsion box bench to stiffen up the wasteboard and frame as advised by others here (sorry, can’t remember who). I built my torsion box way deeper than it needed to be, here’s a rough shot at a more suitably sized unit;

It’s a simple torsion box top and bottom panels held apart by braces, built with MDF or Ply these are stiff and tend to be quite dimensionally stable.

This isn’t isolated from the machine at all, it’s just a rigid support for the machine so you can tram it, level the wasteboard etc. from a flat consistent baseline.

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Next up is to support the box on some sort of table, not much to say about this, you might want to use it for storage, put shelves in, it’s a table;

The table has some compliant material on top of it for the torsion box to sit on, the purpose of this is to decouple the Shapeoko and the torsion box from the table, legs and floor to avoid direct mechanical transmission of noise.

As @Moded1952 pointed out, it’s frequently best to use a smaller pad area of the isolation material. Others on the forum here have also suggested other materials, exercise mats etc.

I’ve had pretty good decoupling from blocks of closed cell foam (open cell tends to just collapse), the best decoupling I found was bubble wrap as it’s almost entirely air but the air leaks out over time.

Dynamat and others have materials which are designed for “floating floor” sound decoupling. These tend to be heavy, rubbery and designed to not compact over time under load. These are designed to be used between the base floor and an upper layer of flooring to isolate sound and are made of materials with high losses in shear, doing the job of turning sound into heat and getting rid of it.

I don’t have the modelling capability to select a material here but I’d start with a thick rubbery material and try a few things out to see what works. The idea of the design here is that the pads could be swapped out for you to try different things.

Hopefully this sort of design will provide a solid base for the machine whilst decoupling the mechanical noises from the floor.

The mechanical decoupling was designed to deal with the bass frequencies, now we need to deal with the mid and high frequency noises.

An enclosure of some sort, there’s loads of really good enclosures folks on the forum here have built, I have rendered a simple box here, it ought to have a front, you probably want some sort of window in the front so you can see what the machine is up to. The height tends to be controlled by the height of the spindle and dust collection hoses. It seems to be a good idea to be able to lift your enclosure off the base for working on the machine.

Just the fact of being in an enclosure is going to kill a lot of the high frequency noise, it will reflect from even quite thin materials and not make it out of the enclosure.

The trick when we reflect sound (or get complex and use diffuser panels etc.) is that sound level drops off with the inverse square of distance so if we make it travel a longer path the energy gets spread out, if there’s reflections we can get destructive interference helping out and also most reflections are imperfect and absorb some of the energy.

For the midrange noise we’ll need some sort of sound absorbing material, the heavy rockwool you linked earlier would probably be good, there’s also the heavy, rubbery foams that Dynamat and others sell. The job of this material is to move with the sound waves and absorb the sound energy through friction turning it into heat. This lining material will also help to deal with the unpleasant standing waves this very rectangular box will produce at around 120, 130 and 240Hz (plus harmonics) and the strong 80Hz resonance the square room will have. Rigid foams are good for plugging holes that sound can leak through but not actually absorbing, we need the material to flex to dump the energy as heat.

As you suggested earlier, lining the walls of the enclosure with the material is an excellent start.

It’s best not to have another rigid material in front of the sound absorbtion material but something like rockwool really needs to be contained so for that a thick open weave fabric is a very good way to keep it in place. The more rubbery foam products from vendors like Dynamat might not need any additional protection. A big vote in favour of rockwool is you can get completely non flammable rockwool that just won’t burn.

I hope that’s a decent start for how to keep the noise in the box. I’ve not included anything about dust extraction, those can be noisy and you’ll also want to find a way to get the heat out of the room as @BartK pointed out above.

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