Soundproofing A CNC Mill Conversion

The Proxxon MF70 is a nice desktop sized milling machine with a lot of useful add-on accessories available for it, making it very desirable for a hacker to have one in his or her home workshop. But its 20000 rpm spindle can cause quite the racket and invite red-faced neighbors. Also, how do you use a milling machine in your home-workshop without covering the whole area in metal chips and sawdust? To solve these issues, [Tim Lebacq] is working on Soundproofing his CNC mill conversion.

To meet his soundproof goal, he obviously had to first convert the manual MF70 to a CNC version. This is fairly straightforward and has been done on this, and similar machines, in many different ways over the years. [Tim] stuck with using the tried-and-tested controller solution consisting of a Raspberry Pi, an Arduino Uno and a grbl shield sandwich, with stepper motor drivers for the three NEMA17 motors. The electronics are housed inside the reclaimed metal box of an old power supply. Since the Proxxon MF70 is already designed to accept a CNC conversion package, mounting the motors and limit switches is pretty straightforward making it easy for [Tim] to make the upgrade.

Soundproofing the box is where he faced unknown territory. The box itself is made from wooden frames lined with particle board. A pair of drawer slides with bolt-action locks is used for the front door which opens vertically up. He’s also thrown in some RGB strips controlled via the Raspberry-Pi for ambient lighting and status indications. But making it soundproof had him experimenting with various materials and techniques. Eventually, he settled on a lining of foam sheets topped up with a layer of — “bubble wrap” ! It seems the uneven surface of the bubble wrap is quite effective in reducing sound – at least to his ears. Time, and neighbours, will tell.

Maybe high density “acoustic foam” sheets would be more effective (the ones similar to “egg crate” style foam sheets, only more dense)? Cleaning the inside of the box could be a big challenge when using such acoustic foam, though. What would be your choice of material for building such a sound proof box? Let us know in the comments below. Going back many years, we’ve posted about this “Portable CNC Mill” and a “Mill to CNC Conversion” for the Proxxon MF70. Seems like a popular machine among hackers.

20 thoughts on “Soundproofing A CNC Mill Conversion

  1. There’s not much energy in those high frequencies. If I were doing that I’d glue laminate 1″ cheap polystyrene insulation panels between two skins of ply or mdf. I was worried about my 42k RPM spindle bothering the neighbors, but it turns out that if my garage doors are closed then I cannot hear the spindle at all once I’m 20 feet down the driveway.

    1. Correct: I made a soundproofing box for my small CNC router, out of the very thick 3 ply corrugated cardboard, assembled with craft paper. It does work very well and costs close to nothing (if you can find some polycarbonate sheet, cut a window and make a double layer on each side.

  2. Galvanized Sheet steel. Lasts forever, should quench 20k .
    Venting is the tricky part.
    Gentlemen… if you are concerned about what you Neighbors think, you should also consider FIRE SAFETY. Stuffing a fairly high wattage machine in a sealed box, with tiny tiny aluminum chips in the contained air is a description of a incendiary bomb if you are at all unlucky or leave it run uncleaned for even an hour or two.
    Heat, cutting oil, hot spindle bearing grease vapors… spark from the spindle motor?
    And if you’re cutting aluminum, you will be using lube or spray mist. That collects and gets messy. Ball end milligrams chips are insidious because they will stick into anything that touches them, from any direction and even light pressure. Don’t wipe with your hands!
    Enclosures are one of the most difficult things to get right on machine tools. Cost, cleaning, effectiveness, durability and EASE OF USE and not limiting access…. that’s a lot to balance.
    Even for small machines.

    1. Thanks for pointing those out LTD. Light (homeshop) use, regular cleaning and a monitor mechanism would minimize those risks, no? I don’t want to find out if it’s bomb-proof…

  3. Two thoughts:

    1) All of us have a glass slab in our pocket that is a semi-functional SPL meter. Would be nice to see some actual numbers of sound dampening effectiveness.

    2) FIRE! Seriously though, doesn’t milling run the risk of throwing sparks or hot metal around? ‘course this is a TINY mill…but a $15 smoke detector inside the (highly-flammable) box would be a life-saver.

  4. My coworker had a great idea for housing/noise proofing a small machine that repeatedly actuates a product for lifespan testing.

    His idea was to throw it in a mini fridge (unplugged). We picked one up used (cheap) and didnt care if it kept food cold or not.
    It turns out the that thermal insulation also generally works for noise insulation. Using the fridge saved time designing an enclosure and saved headache of trying to get the door to seal, latch, etc. And building a double walled enclosure would have surely cost more than our used fridge we picked up from a college house. Although the sound we were trying to muffle was a little different than a high RPM cutting spindle, it would surely be a viable solution for a lot of small projects. You could even plug the fridge in to keep your machine cool :P

    1. A deep chest freezer can be had for around 50$ on Craigslist. Just setting that on a bench with the top door rotated towards the user would allow easy access. Add in 2 hatchback assist springs, and you would have a very large and sealed box for any desk sized machine.

      PS.. I’d obviously gut all of the freezer electronics before attempting this!

  5. Try sorbothane sheets and isolation foot pads to Isolate Vibration and noise. Its used on computers to reduce noise and other scientific equipment.
    See https://en.wikipedia.org/wiki/Sorbothane
    Or one of many other sites like https://www.sorbothane.com/material-properties.aspx – they say Sorbothane can absorb over 50 percent of vibration energy over most of its temperature operating range at frequencies from 10 to 30,000 hertz.
    Hope this Helps….. shop around price varies wildly.

  6. Zackly, a dB app. Once soundproofed from a hot tub bubbler to and incl the tub. Got free high density acoustical fiberglass from a small mfr of who knows what. Sound energy is reflected back each time it meets a new medium, so, layers. People hear what is 2 ft from their head more than 6 feet below them and their carpet, Susoend it, using, again, many dif mediums in the “chain.” Airports reflect noise up with a “flimsy” angled barrier. Use angles too. Idea, sound canceling mic-phones… make a big one. Send anti-noise.

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