Lots of squealing noise cutting aluminum

CNC Machines Nomad
1

I tried to cut some aluminum the last few days and despite trying many combinations of feed rate, cut depth and RPM, I always end up with loud squealing noise, which makes it impossible to let it run in my environment (neighbors), but I also assume this is bad for the tools/machine/material.

I looked at recommendations from this thread: Recommended speeds and feeds for Aluminum

That’s the one with 10-12IPS and 0.01" depth of cut (I tried 250mm and 0.2mm, and also some higher speeds with lower depth of cut).

The 0.2 mm depth of cut seemed way too much, it seems to get a bit better at 0.1 or even 0.05, but still there’s a lot of squealing. Of course then the job also takes 800-1000 minutes which is too long.

The cutter is a 4mm carbide cutter from Lakeshore Carbide.

Questions:

1.) What RPM is recommended for aluminum, in addition to feed and depth of cut?

2.) What would be the expected duration for a job shown in the videos below?

3.) Where do I select the RPM? I did it in the tool’s configuration, is that where it’s supposed to be done or is there a more direct way?

4.) How high does the RPM effectively go? I tried up to 20000rpm but does it really go that high?

Here are some videos, the third one is the worst, that’s with the 250mm/0.2mm feed/depth:

(make sure to download the videos from the menu in the bottom right corner to get the full size/original version which is much better quality).

Do these videos look normal? Could there be something wrong with cutter or collet or a part of the machine?

Here are some settings screenshots, ignore the finish pass values, so far I didn’t get roughing to work.

(BTW: Could you enable video as an allowed file upload format?)

2

I’m not an expert. Here’s my experience so far:

The best I’ve been able to do is .15 mm depth of cut @ 8k RPM, 400 mm/min feed, and 25 mm/min plunge. Seems you’re not that far off.

As to the squealing, cutting aluminum dry never sounds good. Mine sounds quite similar to the videos you posted.

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3

I saw in another post here that 4mm might be too big, so I tried with 3mm again, but I get the same loud noise. Perhaps I should try some spray coolant.

4

To answer your questions (as I’ve asked them too):

For #3, yes you set spindle speed in the tool definition, which is a bit odd because the speed shouldn’t be per tool but rather per material use-case, so hopefully that’ll get adjusted in some future version of MeshCam, but that’s something to bring up in that forum instead of this one.

For #4 12k RPM is the rated top-speed. I don’t know if it has a “ceiling” that it imposes or if it’ll try to go faster, but it’s probably not a good idea for the life of your spindle bearings to try to find out.

As others have mentioned in other threads, squealing/chatter is usually from rubbing the aluminum instead of cutting it well, so you probably need to adjust your feeds/speeds to respect the amount of lateral force the machine can put out, so that you’re properly loading your cutters.

Also, to reduce over-spray & mess, rather than spraying coolant on you might want to just try using a dropper bottle like this one to carefully apply coolant ahead of the cutter, directly where it’s needed. I use this kind of thing for cutting-oil quite frequently when drilling/tapping.

5

Thanks a lot for your tips.

So in your experience is it possible to cut aluminum relatively noise-free on the Nomad? If so, do you have any settings that worked particularly well and do you have any cutter recommendations?

That needle tip bottle looks good, I was worried about making a mess with a spray. What kind of coolant/lubricant do you put in there?

6

I haven’t cut aluminum with the Nomad yet, I’ve just cut it with a few other machines, ranging from doing it manually with old Bridgeports to using a 60krpm spindle mounted on a KUKA robot :slight_smile:

You won’t get “noise-free” but you can shoot for noise-reduced and just do the best you can with the fact that you’re spinning a cutting bit into a hunk of metal.

Once I’ve tried some aluminum in it I’ll get back to you on the recommendations part. For coolant/lubricant I’m no expert, I’ve just used what has been available in the shops I’ve worked on my projects in and no brand-names really stand out in my memory, but I’m betting some of the machinist folks in here might have some suggestions so I’ll defer to them!

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7

Good point, I guess that puts it into perspective :slight_smile:

8

I’ve since found some answers to some of the questions asked previously in this thread, so I figured it’d be a good idea to put quick summary here:

#4 - it’s actually 10krpm max-speed, there was a typo somewhere in a spec that stuck with me, but now I know better!

For lubricant/coolant, you want a fairly light cutting oil for what we’re doing, so I’ve been using soy cutting oil from www.bitsbits.com since I got it as part of their engraving starter-pack. I don’t know if it’s the best stuff in the world, but it seems to work pretty well for me so far.

Also, you probably want to check out the write-ups on www.precisebits.com about calibrating your feeds & speeds for minimum vibration/chatter/noise. The bottom part of this page in particular talks abut fine-tuning your spindle speeds to minimize noise.

9

I’ve been cutting aluminum recently and mine makes a similar noise. I haven’t tried using lubricants, but I will be getting some soon. Here are my settings:

  • 2 Flute 1/8" end mill included with Nomad 883
  • 7500rpm
  • 0.01" depth per pass
  • 12 ipm feed rate
  • 7 ipm plunge rate
  • 0.08" stepover distance (for roughing pass)

You’re probably already be aware of this… but depending on what you are cutting, you may only need to do the waterline pass. This will cut down on your mill time.

10

Thanks a lot for the update, I will check out that page. I got some cutting oil and different cutters as well and will do another attempt at cutting aluminum soon.