Odd CNC ‘enclosure’ decoupling and sound absorption

[LikelyLad (Tom)]

Hi guys, first post on here but been CNCing since the spring. Currently own a 35x35” Millright Mega V but hoping to get a Shapeoko as a second machine, due to its hackability, this community and documentation of what people have done with their machines.

So I’d been thinking for a while of my perfect enclosure design that could house the two machines stacked on two shelves one above the other, before realising that the entranceway area to my house is the perfect size to convert to a ‘CNC room’ - about 120 x 160-ish space leading to a corridor where a door can be installed, converting the space to a massive floor-to-ceiling ready-made ‘enclosure’.

This is one of two entrances to the house so is strictly speaking unnecessary, and right next to the room where I do all my making. Meaning I can move the machines and shop vacs etc into the room, and have loads more space!

I am currently walling off the exterior door and installing a door to the new ‘CNC room’. I’ll be adding an extra layer of two of plasterboard with probably some green glue between to the walls. Next, my plan is to attach rails to the left and right walls (with supports going to the floor), which will support two shelves - my current Mega V below, and the new Shapeoko above. There’ll be a crawl space at the bottom in case I need to get to the far side of the shelves, which will hopefully be rare, and that space I can also use for shop vacs and storage. The shelves will technically be a little too high and a little too low than is 100% comfortable when working with the machines, but I don’t mind making do with a little step/stool respectively.

The main problem with this is the fact that the shelves will be in direct contact with the walls - directly transferring all the lower frequencies through the house (timber-framed). So I was thinking of decoupling the shelves by putting some thick stiff foam between the wall rails and shelves, and have the shelves ‘floating’ (not fixed down - so the shelf just sits on the rail, with foam between) and foam between the edge of the shelves and the wall to prevent lateral movement. The second part of the decoupling would be foam under the machines.

What do you guys think of this general design, and do you have any pointers for the type of foam to use? I live in Japan so will probably be using generic foam rather than specific brands (would ship from the states, but due to COVID shipments seem to be taking a very, very long time to get here). Was thinking of using those 10mm thick jigsaw style floor tile things, cut into strips and layered a few thick, as they are cheap, easy to get hold of in bulk, and not too flimsy. The Mega V is a little heavier (I think about 60kg total) than the SO and uses a rack and pinion system with fast rapids, acceleration/deceleration, so might need more substantial decoupling than the SO.

This design is also favourable to me due to ease and speed of set up. I want to get my machine transferred over the next couple days and running in its new spot as I have some parts that are time-dependent.

As a second point, but I can address later - to absorb the mid to high frequencies and prevent ‘drum syndrome’ was thinking of lining the walls with 15 mm styrofoam, milled into a zigzag surface pattern. Improvements to this idea also appreciated!

Thanks in advance for any thoughts.

[Moded1952 (Lucas)]

For my Nomad, I have a box-in-box enclosure with layers of foam between everything, I’d consider doing the same: put foam on the bottom of the CNC and between the shelf and the rails.

One thing to consider is that without this, the machines might make the shelf itself resonate and act as an amplifier.

As for the kind of foam, you need something kinda beefy for these machines. If the foam is too spongy, the weight of the machine will just compact it and it won’t behave a whole lot better than a solid object. You need foam that still has plenty of air in it even with a heavy machine sitting on top of it. For your rails, that will be even more important, as all the force of the machine will be concentrated on the relatively small area that is the rail.

And you might not be able to get American brands in Japan but I’m sure there are more local businesses that stock sound-insulating foams. There are foams made specifically for insulating machines.

[LiamN (Liam Newcombe)]

The polystyrene will do very little to attenuate noise and is a very flammable wall covering for a machine room, hot steel chips from the mill could easily start a fire in it.

I’d suggest a high density rockwool (there are audio grade rockwools available from sound absorbtion distributors) with a heavy fabric covering if you want to damp mid and high frequency noise effectively. The key is to get a high density grade, not the light fluffy stuff used for insulation;

What type of Rockwool to use for Bass Traps? - Gearslutz

As Lucas says you’ll want a reasonably tough support for the machines. The Shapeoko would be best on a torsion box as it relies on the mounting surface to keep the frame straight and flat. A flooring grade absorber mat such as these would be unlikely to collapse over time;

https://www.trimacoustics.co.uk/product/srs-acoustilay/

[LikelyLad (Tom)]

Great points guys, thank you.

I didn’t think about the fact the shelves effectively become amplifiers! The decoupling under the machine should be high on the list, then.

Good point on about the foam being a fire hazard. I’ve been going with plasterboard rather than chipboard I had lying around for the same reason…

I’ve been thinking about the structure, and maybe isolating completely from the walls - using a stand-alone frame with legs sitting on concrete blocks, dampers between - would be better? The damped section would be reduced (just the feet) but would be disconnected from the walls…

So far I’ve found small square rubber, gel and mechanical dampers… instinctively feel like the gel would be most effective, and the manufacturer has a variety with different load ratings.

[LiamN (Liam Newcombe)]

Yep, a stand that is isolated from the wall is likely to perform better in terms of noise, as you say there’s a whole range of products out there designed to isolate machinery from it’s installation pads from pumps to mills.

Paving slabs are a common choice, if the floor will support them and the machine weight, they spread the load and provide mass on the other side of the damper.

Are the gel products you looked at the sorbothane type gels? They are visco-elastic and designed to convert vibration energy to heat when flexed.

[ColdCoffee (Robert)]

I recently fell down this slippery slope, and regret nothing

I looked over all of the enclosures within the Enclosure Zoo, watched lots of youtube videos, read webpages, and followed advice (like @LiamN suggestion on Rockwool).

I ended up with a large structure that sits in my garage. The wall that the machine is up against is shared with a bedroom inside the house. My kid can not hear the CNC machine when it is running, but can barely hear the hum of the shop-vac. And this is with the enclosure doors open.

Having a CNC room is awesome, and it looks like you are on the right path for reducing the sound. I suggest spending at least as much effort thinking about dust and heat.

Dust Collection: I have not found or even seen a “great” solution, just “good” solutions (my opinion). There are scenarios where my dust collection works really well, and scenarios where it works poorly. One advantage of using an enclosure is it reduces the range of the dust-disaster. But how do you clean the dust captured within the enclosure that didn’t get pulled into the dust collector? Despite all my efforts, I still notice a layer of dust on things in my garage. I hope your CNC room is not carpeted, and assuming your CNC room is part of a central AC/heat system for your house, make sure there is no air intake (aka AC return) for that system in this room. If you dodged that bullet, that means this room will be positively pressured when your AC is running, so make sure there are good seals on the CNC room door. And avoid cutting MDF on your CNC, holy crap the dust problem is twice as bad.

Heat: The hottest thing in my entire setup is the shop-vac. I thought I had a plan for this by building an exhaust vent into the enclosure. I have the exhaust from the shop-vac hooked up to an exhaust port. In the FLIR image below, the exhaust hose can be seen disappearing behind an air compressor. It may help, but it was not a solution.