Feed Rate/Cutting Depth

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1

Hey all,

Quick question regarding feed rate/cutting depth. I have a 12x25in MPCNC with the Bauer (harbor freight) router. I mainly cut wood, specifically oak, walnut, maple, and I have been really struggling to actually get decent cutting settings. Basically I have to run at 0.3mm depth of cut, and around 2mm/s speed to get a decent cut/not get a ton of chatter. Any more than about 0.5mm of depth and I get a ton of vibration, chatter, and overall is just extremely loud. I am thinking maybe the bit is to blame, as I am just using a straight fluted bit. Would a spiral bit work better?
Also, what should I set the router speed to? Right now, I just turn it down to as low as I can while still actually cutting and not pushing.

I feel like my expectations aren’t too high, given the fact I have a relatively normal sized MPCNC. I was wondering what others are using for their speeds and feeds to see what is reasonable.

Feel free to ask any more details, and thanks in advance!

2

Can you post some pictures of your build?

Can you post a picture or link to your bit?

Your speeds / feeds are much slower that what is on the milling basics page. You should be able to achieve those at the very least since they are very conservative.

3

Yes, that’s why I am a bit stuck, as I figured the milling basics speeds were pretty conservative

Here is the current bit I am using.

IMG_3199
IMG_31991284×625 64.9 KB

And here is my machine.

IMG_3081
IMG_30813024×4032 3.21 MB

4

If you run to high rpm and to low feed rate you’ll end up burning your bit and dulling it. After that. It won’t cut well at all.

I run a similar bit, seems to cut well. Rule of thumb for depth is 1/2 diameter. That works be around 1.5mm for an 1/8 bit.

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5

How thick is the material and how are you holding it down, i only mention this as i used to get significant vibrations/noise including rough cuts . It turned out to be the workpeice resonating and more likley to happen with thin stock. I personaly set the router speed quite low (1, 2, 3 on a Makita) but thats about feeds and speeds chip size ect, I havent gone wrong yet with a minimum feed rate of 8-12mm/s with a 3.175mm upcut spiral endmill and use a DOC of half the bit diameter, i can probably go a lot faster and plan on some tests soon but no two machines are the same.

6

Actually, no.

The general rule is hardwood and plywood 1x diameter, for softer wood 2x diameter. Granted, this might be a tad too high for an MPCNC, but it is possible. See here:

I use to cut plywood with a 3.175mm bit, 1x depth and 1200mm/min with a Primo.

Conclusion: something is loose. Can you post a video of it cutting?

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7

Thanks for the help everyone. After playing with my z axis for a bit, it had a tiny bit of play, nothing crazy, but I was able to get it to a point where by wiggling just the z pipes, the entire table moves, aka it seems pretty tight.

Based on your cutting video, maybe I was just expecting a different noise/less noise from cutting from when I just used the router by hand, and the sound of it cutting sounds a bit like what mine did originally.

My new spiral compression bit comes in today, so I will perform some cuts with that and post a video of it cutting. I have been running my old bit at high rpm/low feed rates, so I would have to imagine it is pretty dull. Hopefully a new bit will help with that.

Side note: those speeds look quite impressive.

8

Still trying to dial in my MPCNC. Retightened everything and it seems pretty solid. Just wondering, is the high pitched squeal sound you sometimes hear on your video something I should be expecting? I think maybe I viewed that noise as bad and that I was probably doing something wrong. Obviously I know it’s not going to be a quiet operation, but the intermittent higher pitched noises didn’t seem right

9

This only happens if you go fast and deep, then it should be normal. I found it very irritating as well at first.