Inspired by the Ultimate HDM Enclosure build thread, I figure I might as well start one for the nomad, albeit with a focus on sound dampening.
I’ve been playing around with sound dampening ideas for quite some time now. These ideas have been fun to ideate and test but they’re all…pretty hacky.
I’ve just pulled the trigger on a bunch of sound dampening material from the best the US has to offer (Acoustiblok) so it’s time to design a proper enclosure leveraging that material.
Let’s get some things out of the way:
Q: Why didn’t I design the enclosure completely before ordering material?
A: The MOQ for this stuff pretty easily covers a few enclosures. So I know I’ll have enough regardless of the eventual design.
Q: Wow, Acoustiblok is spendy! Why not just use standard MLV and Rock wool!?
A: Great point, I actually want to design with the intention of easily building with the standard off the shelf stuff.
I figure folks can use this design to build their own without the exorbitant costs and I’ll build one in each style for a head up head comparison. I want to know if this stuff is worth the extra cost
(To be clear, the result will not be a “budget” version vs an expensive version. It’s much more likely to be an expensive version vs a very expensive version…with a budget minded option coming eventually)
Q: Why is everything designed with metric!?
A: How did you know it would all be metric? Good intuition though, it will be because metric is clearly superior
Ok now that’s out of the way I can start on some requirements…in the next post.
In the mean time, if you have any specific requests or requirements you’d like me to consider feel free to leave them in this thread. I’ll see if they make sense for me to integrate
I know at least 6 people will be mildly interested in the results of this thread. <there-are-dozens-of-us.gif>
These are the hard requirements for the project, if these are not achieved the enclosure is considered a failure.
Enough noise reduction to facilitate cutting aluminum at 24,000 rpm at any hour without complaints [2]
Ability to run long operations without issue from heat or air exchange when cutting aluminum. [3]
Tool free access to the nomad, eg: no locking seals with bolts etc.
Integrated flicker free lighting…Yeah light is a hard requirement.
Reasonably fire safe
Soft requirements
The soft requirements are less important than the hard requirements but more important than the follow on “Nice to have’s”. I expect there will be more soft requirements than seems reasonable.
A good effort will be made to satisfy the soft requirements but I will not block on them.
Plumbing for compressed air (Through the tubes of the extruded aluminum frame? Maybe )
The pullout nomad shelf should facilitate chip clearing, likely by way of steel grating as opposed to a solid shelf
Integrated pull out bottom shelf to act as a reservoir with pump…or just a convenient chip tray.
Bottom most shelf should be easily removable to facilitate cleaning and servicing.
Buildable with just simple hand tools and a 3d printer.
Approach
This is a general overview of the approach for building and dampening.
The structure will be made with extruded aluminum. This material is easy to source ~everywhere and facilitates many of the needs I’ve laid out such as integrated pressurized fluids and various mounting options. It also helps that we can usually send a cut sheet with the order to get lengths ready to go at a reasonable cost.
Soft requirements and nice to have’s should be designed to be optional whenever possible. If someone does not want to integrate a pull out drawer system, it should not require a complete redesign. EG: Optionality should be built up as bolt on wherever possible.
When it comes to sizing and material selection, we will tend towards off the shelf materials/sizing wherever possible. As a contrived example, if it is easy to buy a precision steel rod in lengths of 100mm but we only need 90mm, the design intent would be to integrate the uncut 100mm length as opposed to requiring a cut.
Items that can be easily substituted should be called out along with an example of the suitable replacement. For instance, the 2lb/sq foot Accustiblok can be subbed out for 2lb/sq foot Mass Loaded Vinyl.
Items that can be substituted easily in order to trade cost for effect should also be called out. For instance, the 2lb/sq foot MLV can be subbed out for 1lb/sq foot MLV. This is roughly half the cost but will come at the expense of effectiveness.
In these cases, general guidance should be offered on impact to the rest of the design. 1lb/sq foot MLV is half the thickness, so any design considerations dependent on total wall thickness which may be impacted should be called out.
Sound Dampening Overview
The sound dampening design is heavily inspired by directly steals the design from a previous post by the most knowledgeable contributor I’ve come across.
Mark Bellon has provided the most complete examples and demonstrates the most complete understanding of sound conditioning that I’ve ever seen. This post was the inspiration for my entire project:
If I could pay Mark to design this for me, I would. Unfortunately I’m about a decade too late
TLDR from his post:
It’s all about MASS , LAYERS , and effective use of materials. The walls are 3.5" thick and have 5 layers of sound suppression - outer skin, Green Glue - inner skin, Accustiblock, Quiet Fiber.
A final note: I use fusion 360 and my design will be fully modeled in fusion 360. If that’s not your jam, sorry. Maybe one of the kind forum folks will translate it to something else or come up with some drawings to share…but it won’t be me
To keep all of the requirements neat and organized, I will just be editing this post. It’s not the cleanest method but I think it will be better than stringing them out through the project as it unfolds ↩︎
Tyler, there’s already been an Ultimate Nomad Enclosure so yours will probably need to be the Ultimate-r Nomad Enclosure (shades of “The New Originals” from This is Spinal Tap…)
I’ve also followed the sound-damping enclosure threads --Mark originally described his extrusion-framed enclosure in the Custom Enclosure Zoo thread
Myself, I wonder about aluminum’s lack of internal damping itself. Since the enclosure isn’t really structural at all, I’ve thought about the light-weight pound-the-junctions-in kind of aluminum extrusions, which could have expandable foam squirted in, or just furniture-padding kind of urethane foam poked in for damping of the frame itself. Hinges and things could still be attached with sheet metal screws–the self-drilling kind used in metal-framed house construction would be convenient… I actually used that kind of extrusion once for an enclosure at work a long time ago in a state far, far away (California…) And it hasn’t occurred to me at all that custom junctions could probably be easily designed and FDM-printed. And as much as I buy stuff from McMaster-Carr every week at work, I will not even point out that they have downloadable STEP files of all the standard junctions…
But wouldn’t all that be better with good ol decimal mm
Granted, my perspective might be skewed considering I rarely work with anything larger than a 40mm cube…so you might be on to something with your decimal inches.
Time will tell, though I’ll still be using metric for this design at least:wink:
I’ve thought about using something other than aluminum extrusion but I quite like the modularity it affords. Hanging things off of the enclosure like in process endmills and other commonly used tooling is just too convenient for me to give up for the marginal cost increase. I also move things around a lot so being able to break down and reconstruct easily is moderately important to me (I should add that to the requirements )
There are also some additional things I’ve thought about using the aluminum extrusion for considering the internal passages tend to be pressure rated. Using the extrusion as a sort of pass through manifold for compressed air and such is interesting.
It might be worth filling those internals with sand or something to increase the dampening. I’m just not sure if it would be necessary/noticeable compared to the rest of the build
I used to design enclosures for compressors (after I was done with the compressor itself). There were three interesting things I learned that weren’t quite “common sense”.
Sound travels along line of sight, through any gap, crack, etc… but that’s a frequency-dependent truth. A narrow slot with long depth - imagine two sheets of paper spaced 1/8" apart - has enough viscous damping along the sides to impact the sound wave, so a cluster of very narrow open slots in a very thick “wall” can be an effective way to damped sound while allowing air exchange. If not intentional, use a gooey sealant on cracks to prevent sound leakage.
Sound can be absorbed (commonly via open cell foams) by anything half its wavelength or deeper. Sound can be blocked pretty much only by decoupled mass. A good absorptive material on 4 sides will dramatically reduce the amount of sound you need to block on the remaining two sides. This absorption is also effective on air ductwork. This is probably why, on earlier enclosure designs, removing panels reduced noise - it allowed it to absorb into the enclosure instead of reflecting out the front.
Frequency response is pretty important when decoupling the machine from the enclosure base. Barry Controls was my go-to, but the Nomad is such a high frequency, a simple A90 urethane pad clamped between the machine frame and the enclosure base might do the trick.
There’s some other cool math around Helmholtz resonators and designing panels around certain frequency ranges, but on the whole, MLV with a 2" foam is pretty effective for these frequency ranges. Double-pane windows help (especially if different densities so they don’t excite one another), and drawing air in from a perforated “apron” around the base keeps noise from leaking out as easily. Maybe even do a downdraft table for chip evacuation.
HMU if you want to bounce any more specific ideas! It’s been a few years but I can remember much of it clearly - we got a machine from 115dB down to 81, mostly in the 2kHz range.
Download every part, fitting and extrusion they have - easy peasy. Even set the length of the extrusion and download that exact length. The “40 Series” seems to have the most fittings and options. At work we use the:
40-4040 - “40 Series” 40mm x 40mm t-slot extrusion
40-4080 - “40 Series” 40mm x 80mm t-slot extrusion
40-8080 - “40 Series” 80mm x 80mm t-slot extrusion
40-8016 - “40 Series” 80mm x 160mm t-slot extrusion
You do have to have an account, but I used my least used email account and did not notice an increase in junk emails after registering.
I try to buy from them as much as I can. I grew up near the 8020 operation and they always sponsored the local robotics competitions. (Provided extrusion for all of the fields and such)
They always had a rule that you can’t destroy the field. One time we had to break a beam near the walls…we cut off some of my memory foam pillow and zip tied it to the front of the bot. Slammed into that wall full speed They allowed it.
My Acoustiblok materials are arriving this week. I’ve got vacation all next week, hopefully that means good progress on this project
(MOQ on the 2lb per square foot rolls of their MLV equivalent is ~112 square feet. So it ships on a pallet. All in my order is listed at 516lbs shipping weight )
Took some measurements while cutting with a 274-Z in 6061, 24k/min spindle speed.
Dominant frequencies were a defined spike at 375Hz (am I getting belt slip? Is this my spindle speed, or does the number of poles on the motor line up with the belt ratio to the spindle better than expected?), and between 1000 and 1500Hz. Max noise level was about 87dB at 375Hz (regardless of cutting forces) and 80-84dB at the higher frequencies (mostly during roughing).
For 375Hz, that means 18" of absorptive material to fully block it - so decoupled MLV is a better approach (e.g. MLV on a thin layer of foam, with a thicker layer of foam on its face).
For 1kHz, 6" of foam is pretty effective. For 1500Hz, 4" of foam should do it.
Honestly, MUCH lower frequencies than I was expecting. I wonder if it’s because the door was closed… I definitely learned something today.
So yeah, the high mass approach looks well-targeted. Two-flute endmills might shift frequencies higher, but not by much.
And there’s reason to wonder whether a targeted noise “shield” around the spindle motor might have a huge effect, and whether a dust boot could then be used to create forced cooling through this shield.
I tried measuring the airflow from a router when I was curious about that, and based on a rough/improvised measurement (how long it took to fill a trash bag), the volume of air moved is very small compared to how much air a vacuum moves — that said, I am trying to puzzle out a way to do this on my current setup, but because it vents out and blows air directly at me, which I find annoying.
I’ve read and heard good things about it. It’s most likely to be one of the components that gets called out as a suitable substitute for folks in my plans
Another one is Homasote Soundboard 440. I put this in my laundry room because the wall was shared with my TV room. The Soundboard 440 is screwed to the studs, and the sheetrock is screwed to the soundboard between the studs. The soundboard is like dense pressed cardboard fiber, and really does work well. The only time I hear things like shoes bouncing around in the dryer are when the laundry room door is open.
The accoustiblok material arrived today and I’ve got to say, it’s nuts. Just carrying the whisper mat foam panels from the street to the garage provided an excellent example of what good sound suppression can do. One ear heard every car blow by loud and clear whereas the ear with the material between it and the road was oddly quiet, exactly what I want
And 2lb/square foot rubber is no joke either. The density of that material is very apparent when you’re carrying a roll of it
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They allowed it.
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