Help with cutting circle frames

@MrHume

Try a new Cutter to start.

The Z stepper and the spindle are not related power wise.

Enlarging the slots would alleviate the full depth situation that I think is happening.

Again- wood will expand and move as you remove material, and every peice of wood is different.

Lets see the tool, and I would love to see more of these parts, Really nice.

I use a 10X eye loop and look at the cutting edges. (ebay $4)

Look at a new one cutter, now look at a used one and look for

  1. chipped edges,
  2. worn cutting edges,
  3. wood resin stuck to the cutter, etc.

Some guys will see how it feels against their fingernail (old vs new), scrapping the nail lightly.

I know this may not be a popular answer since Carbide3D only sells end mills (originally designed for cutting metal), but I recommend using QUALITY Router cutting bits from a place like Rockler, etc.for cutting wood They are designed for cutting wood, and produce a better surface finish in my opinion.

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Please use the operating checklist — http://docs.carbide3d.com/article/41-machine-operating-checklist — I suspect your endmill has become dulled, or it may be that a belt is loose or wearing.

Another possible consideration is moisture content, and the wood in question may be “reaction” wood, which wants to bend / straighten after being cut, or it just may be tougher, harder grain.

Best long-endmill which I’ve found is Garr Tools extra reach tools: http://www.shapeoko.com/wiki/index.php/Endmills#Specific_Bit_and_Brand_Recommendations

excellent quality, long narrow bit w/ a long cutting length which makes workholding and fixturing much easier, and making through cuts (w/ a suitable number of passes) on 1" material feasible.

http://www.garrtool.com/tooldetaillogin.jsp?edp=41030

Here’s a couple photos. It was surprisingly hard to get the camera to focus on the end mill, so hopefully these are clear enough.

I will definitely post more about these frames very soon, they are made largely on the Nomad, and then hand finished, and they’re coming out great!

On the subject of wood, assuming I get a cutter in there that is properly sharp, of course, how much should I expect to have to vary my feeds and speeds between Walnut, Cherry, and Maple?

Thanks, @WillAdams and @RichCournoyer, I have ordered some new cutters from C3D, and am also going to look into other brands.

@MrHume
Heres some pics from great wood book.

Looks like Walnut is the hardest of the 3 species you mentioned, Of course, there are lots of different species of Walnut, and Cherry and Maple.

Check the specific gravity number of the wood for its density.

FYI: A wood with a specific Gravity of 1 will not float, example: Lignum Vitae (IMO: the king of all woods)



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Thanks for showing us this book @ApolloCrowe!. I’ll be buying one. Eager to learn about woods.

I wonder if using a 3-fluted cutter might help, since the cutting flutes won’t be directly across from each other in the slot?

Randy

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Some potentially useful references are listed at: http://www.shapeoko.com/wiki/index.php/Books#Wood

esp. note http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf Wood Handbook: Wood as an Engineering Material

That’s an interesting idea. Is the Nomad powerful enough to use 3 fluted cutters? I think I have one I ordered by mistake and then thought I couldn’t use…

Ok, so here it goes. Worked very well right until the final pass, at the end of which it gets stuck, drops a couple steps, and generally ruins my day.

Put my sharpest cutter in there, so I think that let it get farther. Wish I knew why this was happening now, after doing loads of these with no trouble. I need to get them done, soon, so I’m starting to get a bit worried!

If I have no choice but to enlarge the slot, how would I do that? I made these models in CC. Would I just have to add another circle and tell it to do a pocket cut? Or what?

Do you guys think using a 3 fluted cutter is worth a try? I happen to have this one, from Harvey Tool:
Cutter Diameter: .125" (1/8)
Length Of Cut: 1.000"
Overall Reach: 1.000"
Flutes: 3
Shank Diameter: 1/8"
Coating: AlTiN
http://www.harveytool.com/ToolTechInfo.aspx?ToolNumber=33708-C3

It looks like your feed rate is way too high for a Normad.

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I got that speed using G-Wizard, and have been able to run at it pretty well up till now. I did think it was too fast when I first started experimenting with it, but after a few nervous attempts with no issues, it seemed like it would be ok.

I also tried lowering the speed and the plunge rate by nearly half, but got the same result. Admittedly that was with a dull cutter…

@ApolloCrowe If I do need to make the slots wider, would it suffice to just make them wider for half their depth?

As I see it, looking at the video, Richard is right.
But as I hear… When I hear the sound of the cutting process, it hurts my ears.
I hear a quite unhappy cutting process. I hear resonances, vibrations.
This maybe affects the stability of your strategy mounting the stock to the base.
Can you give more information on how you fix the stock?

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Agreed, it sounds dreadful. I don’t suppose anyone could post a video of a Nomad machining some maple (or other hardwood), in long passes, at a reasonable speed, so I can hear what it ought to sound like, could they? I feel like based on the sound, this is running right at the edge of chatter.

I suppose it could be my fixturing. I’m just using the excellent Nitto Tape at present. I have prepared the rest of the blanks for this process with holes so they can be mounted to the bed with screws - since they are 8x8 they take up all space where I could use any kind of vises etc.

What is most vexing is that this did not happen for so many identical pieces, running the exact same program, and now suddenly it is. I wish I knew what changed. Could the addition of the pockets in the top of the piece be causing it to flex?

Have you checked your leadscrews for dust or dirt? Lubricated them?

http://docs.carbide3d.com/article/13-what-oil-should-i-use-to-lubricate-the-linear-bearings

Hopefully once we can puzzle out your difficulty it will be something amenable to being added to the operating checklist: http://docs.carbide3d.com/article/41-machine-operating-checklist (should that be revised / updated / adapted for the Nomad? It was written w/a Shapeoko in mind).

@MrHume

Exact same program, but you added more Pockets.

You added more Ring cuts?

/–|-|–\

The wood is pulling inward is my guess.

@ApolloCrowe Yes! The pockets are cut first. They are about 5mm wide, and stop 10mm from the bottom of the blank. Then I cut the slots, which go nearly all the way through, stopping just .2mm from the bottom. Previous frames were made with only the one larger frame, and not the two smaller ones inside it. I got so hung up on the feeds and speeds being the same as before, it didn’t occur to me what had changed. I can’t believe I didn’t think of it.

Here’s an annotated image to make it clear:

Do you think if I cut from the outside in, first doing the pocket, then the two slots to cut out the frame, and then moving to the next one inside of that, and so forth, that it would help with the issue?

Also, should I slow it down?

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@MrHume

A pocket operation would alleviate the work grabbing the tool at depth.

Im curious if a center out would be better or not.

One thing at a time to diagnose the issue.

If you want a quiet cut, yes slow down.

If you dont mind the noise, and you want to up your production, It may be a good time to get a Shapeoko to help with the heavier cuts.