"Fuzziness" on 3D milled wood on first ever CNC projects

[jasonwebb]

I just started playing with a Roland Modela MDX-40A about a week ago and have been using VCarve Pro to explore 3D contour milling in various materials. So far I have tried insulation foam, cutoffs of 2x4' pine studs and some blocks of basswood meant for carving. So far, all of my wood projects have been covered in a lots of tiny, fuzzy bits of wood (burrs?), and I'm trying to figure out what is causing it and how to fix it. Pictures are attached of some of the attempts so far.

For all of my projects so far I am using 2-flute, ball nose, upcut end mills stepping progressively down from 1/4" diameter to 1/8" and finally with 1/16". I believe the spindle is running at roughly 40-50IPM and 12,200RPM, though I think I brought the movement speed down really far (40% or so) after experiencing some plunging problems.

From my initial research it sounds like this fuzziness could very likely be the result of using upcut mills rather than downcut - the set of endmills I have access to is upcut only. Would this be the most likely culprit for this problem? If so, can someone point me towards a source where I can buy some 1/8" and 1/16" end mills from? If not, what else could I look into as possible causes?

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[ger21]

Soft woods tend to be much more fuzzy than harder woods.
What stepover are you using? Usually, with harder woods, and 8%-10% stepover, you won't have much fuzziness at all.
Cutting with the grain direction can also help.

I'd also increase your rpm to at least 15,000.

I use inexpensive ballnose bits from Drillman1 on Ebay.

[jasonwebb]

Looks like the stepover for all of my toolpaths are set to 10% - maybe I should decrease it down to 8% if that makes a difference?

I tried cutting with the grain on a block of pine and got similar results, but much more splintering and cracking during the roughing pass. Worked fine, but was a little more scary, haha.

The Modela MDX-40A maxes out at 15,000RPM, so no dice on increasing the speed there :P

Thanks for the eBay hookup! I came across his store a while ago, but it was pretty hard to locate what I was looking for there. I don't see any 1/16" 2-flute ball nose downcut end mills on his site. The closest I've found are some 1/16" 2-flute straight nose downcut mills, but no ball nose. Am I looking for the wrong keywords?

[ger21]

Just about everyone uses upcut ballnose bits.
Downcut ballnose bits are not common, and you'd have a very hard time finding them, if you can at all.

Only do the finish cuts with the grain, keep the roughing across the grain.
Going from 10% to 8% won't make much difference, I don't think.

I think the biggest issue is your choice of wood. As I mentioned before, the harder the wood, the cleaner the cuts. Get some maple and do some tests.

[awerby]

Basswood is notorious for that. Although technically a hardwood, it's actually really soft, and the fibers tend to pull out, leaving that fuzzy texture. Pine isn't much better; it's a softwood with a big difference between the hard and soft layers, so you get tear-out. The best wood I've found for intricate carvings like you're attempting is boxwood, but it's expensive and hard to find. More available woods like walnut, maple and cherry will give you much better results than the basswood. You can try using a fine wire brush to remove the fuzz, but it's better not to produce it in the first place.

Insulation foam isn't going to give a very fine surface either; if you want good detail in foam, go for a much denser product like Butterboard https://www.goldenwestmfg.com/machineable-plastics.html Your 2-flute upcut bits are fine; downcut is only important when you're dealing with laminates that tend to peel off the top layer. It's important to have really sharp tools for wood; anything you've used previously for cutting metals won't work. HSS tools can be sharper than carbide, but they won't last as long. For carving, I like the tapered carving bits that Precisebits sells; they come to a fine point, but aren't as susceptible to breakage as a tool that's 1/16" or whatever all the way up: Tapered 3D C arving Tools

[ihavenofish]

first make sure the bit is new and sharp. wood no like dull bits. carbide is preferable, hss dulls fast. wood isnt hard like metal, but its often abrasive and dulls tools faster than you might imagine.

try hard maple. i find its one of the best for cnc carving in terms of finish quality and its cheap. pine is aweful, as is african mahogany. never tried bass wood. yellow poplar also carves nice, but its full of minerals and will dull hss tools almost instantly and even carbide doesnt last long.