Trying to cut simple basic shapes

Aspen and Poplar are very soft woods and tend to splinter when you cut them. I found that covering the job with Tyvek House Wrap tape tends to give a much cleaner cut. I have also used the product below with good results.

One more thing to consider. I use 3/4 PVC board for a lot of my projects. I love it. It cuts clean and is easy to work with. They do sell it in 1/4 thickness in 4 x 8 sheets which may be what your using…

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Check your pulleys. Make sure the pulleys are tight on the stepper motor shafts, and that one set screw is over the flat part of the motor shaft.

If the X Axis pulley was loose enough to move, but not yet loose enough to spin all the way around, it would produce results very much like what you are seeing.

Another test - with the power on, everything should be ‘locked’ in place by the stepper motors. Try to move things around and see where the slop is.

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Thanks so much for your suggestions, everyone!!

This article helped explain, thank you.
But still, what is slotting?
What applications would adding geometry be an appropriate for? Both examples in the article are for rounding hard edges.

I had actually skipped the Hello World pen tutorial, but I just did it just now, and it ran through just fine.
I made the toolpath suggestions you offered. And the RPM control had slipped to 4, so I reduced that.
I did not change the offset direction to outside, because I accounted for this when creating my file in photoshop. But it’s good to know, so I don’t have to make that adjustment on the front end anymore!

Thanks for the explanations about speeds, I did raise it to 60.
I do use double stick tape on the bottom of my board in addition to the clamps, so those suckers aren’t moving at all :blush:

Thanks for the Vinyl suggestion, I hadnt though of that at all! The PVC is a nice suggestion also, but I stain all of my shapes lots of bright colors, so it really needs to be wood.

I wiggled everything around and there was a good amount of ‘slop’. Specifically the right side X Axis. So I tightened that pully.

With these adjustments, things were definitely better, but the same problems still persisted: Wonky shapes and fuzzy edges. But now it seems to be only the small pieces that are misshapen, the larger pieces straightened up. Is this a situation for the ‘adding geometry’?

And the edges, although better, still showed all three passes making them fuzzy all the way down, so the suggestion of a vinyl layer on top wouldn’t help the next 2 passes, I suspect. Would the ‘down cutting’ bit address this?

Again, I really appreciate all of this feedback! THANK YOU!

Slotting is cutting a slot as narrow as the endmill.

Adding geometry is appropriate any time one wants to cut as a pocket rather than as a contour.

A downcut endmill would definitely help in getting clean top edges. What is surprising is that you get fuzzies all the way from top to bottom (upcut endmills typically leave tearout on top edges but provide clean bottom edges, and conversely for downcut endmills). I wonder if the endmill you are using is worn out ? Using a new downcut endmill would probably answer that question.

Tearout shouldn’t be as bad as this, but you will also get some. One approach to clean it up is to run a second contour pass at full depth (i.e. keep the contour cuts you have, with the tabs, duplicate that toolpath, and edit it to set a depth per pass corresponding to the full stock thickness. When you run that second pass, theoretically it should not cut anything since the first toolpath already went all the way down, but in reality it will shave off the remaining fuzzies from the sides.

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As a newbie myself, I see issues with the mechanics of your machine. Something is not right as others have said.

I found that sometimes larger bits cut cleaner. Try a 1/4 bit and do an outside cut on all your designs. This may eliminate some of the fuzzies.

Hi @Julien, thanks for your thoughts.

I purchased the started pack endmills from Carbide 5 months ago. It has a #251 .25" downcut endmill in it, so I will give that a try. But should the #102 .125" Flat Endmill be worn out already, after very limited and sporadic use, through soft wood?

Also thanks for the suggestion of a ‘clean up run’, and I see how this could help, but it doesn’t diagnose/address the problem, eps if you acknowledge that the tearout should not be this bad.

So I was thinking the CNC makes 3 passes, and you can clearly see all 3 passes with the fuzzies. In order for this to happen wouldn’t the endmill have to move a tad bit outward each pass in order for it not to keep hitting the same depth wall as it laps around? or for it to be crooked? IDK, just spitballing here…

@Zman suggests something more is wrong with the machine. Is there another test or diagnostic I could do to rule stuff out?

Thanks again

Probably not, if it has not been “abused” (i.e. using incorrect feeds and speeds, for example going to slow is one way to prematurely dull a tool). I just wanted to rule out one possibility, this is not it then.

Hard to tell from the pictures: do the fuzzies really match the passes, or do them happen to match the plywood layers ?

Actually it’s a good hunch, I did not want to mention it to not confuse the matter more, but a severely out of tram router may also leave marks at each depth pass. I’m not sure it could explain so much tearout, but it’s a good thing to tram your router anyway (check out Winston’s YouTube videos)

Curious to see what the outcome of the downcut test will be.

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I am not using plywood, i am using solid poplar, so the 3 rings of fuzzies are definitely from the passes.
I’ll check out the Tram router video and update after the downcut test later tonight.
thanks again

Obviously not, sorry. Somehow I overlooked the mention to poplar and got confused by the last pic :man_facepalming:

Also, if the fuzzies look the same all around the part perimeter, it’s probably not tramming.

So, it’s all fixed. Hard to believe, it’ been so long.

I changed from the .125" endmill to the .25" downcut endmill, changing NOTHING else, and the result was beautiful: Smooth edges, symmetrical shapes. Couldn’t believe it, so I did it again with matching results. Then I tried my new .0625" normal endmill and also got beautiful results. So there must have been something wrong with the .125" endmill I had been using all along, right? But it looks fine to the eye, no distortions, no gouges. So I tried to replicate the ugly cuts with the same .125" but got beautiful cuts here too.

Can you explain this, please? For 4 months, since day 1, I have had consistently wonky shapes and seriously fuzzy edges (with each pass), and had numerous emails and phone calls with the carbide team. How can I avoid this again, if I don’t know what happened?

Don’t get me wrong, I’m excited it’s fixed but a little flabbergasted at the mundaneness of the solution, ya know? I’m kinda holding by breath…

Really appreciate your help.

Further developments:
After making 3 good cuts with 3 different endmills yesterday (including the suspect 1/8) I started today with a basic shape/text test with the same1/8 and it looks fine, contours and pockets:

Believing the prob was over at lonoooog last, I returned to my actual project, using all of the same parameters, same 1/8 endmill, same everything from the test above, & the damn fuzzy edges are back! You can clearly see how it is stepping out with every lap:

Then I changed the endmill again to the 1/16 and got this nice edge:

Please, please, please…what is going on? I am just stuck. 4-5 months of lost time, lost product, lost hope & still not there…

Please contact us at and we’ll do our best to work through this with you.

Try a wood that is NOT as soft as aspen, maybe even Pine as a trial. I tried to mill a bank out of Aspen and it was horrible to work with. You might try that before contacting Carbide just to see if your files work in something else.

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At this point I think it’s a mix of things.

  • Were all the tests above made from the same stock / piece of wood? Part of this might be inconsistent wood quality too ?. Some soft woods are surprisingly hard to cut well (the downcut helps, but…)

  • the 1/8" upcut may be worn out and you got lucky on those interdemediate tests. If you have a loupe you could try and inspect the cutting edges up close. This is what a fresh tool vs dull tool look like under a cheap USB microscope. Also I had a thought: check whether the very tip of the two flutes on that endmill are not chipped : is the tip is chipped, that part of the endmill woud both rip the wood rather than cut it, and would also leave a ridge, like you are seeing. If you have been fighting this for 5 months, I say throw away that 1/8" endmill EVEN if you are not 100% sure it’s bad. Your time is worth much more than a 1/8" tool, obviously.

  • can you remind us what cutting parameters you are using at this point ? That latest bad cut pic you posted has me puzzled because not only do you have fuzzies, you also seem to have steps at different depth ? I may be mistake.


My guess is that the material is moving while you cut, maybe not in the X and/or Y axis, but in the Z axis. It is easy to underestimate the amount of lifting force an upcut bit puts on the material.

While this theory would explain why a 1/16 bit didn’t have a problem (regardless of up vs down cut) compared the 1/8th upcut. The theory only works when assuming your 1/4 bit is a downcut bit, so the material didn’t lift.

In a perfect world, Carbide 3D would ask you “are you planning on cutting wood or metal?” when you purchase a machine. If you say “wood” the starter bits would be downcut, and if you say metal the starter bits would be the (current) upcut. I’m sure there are lots of exceptions and reasons why they don’t, but it’s something most of us had to just learn on our own.

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If you haven’t checked your set screws - it was the major pain point I had as a newbie and I was seeing the exact problem you were showing in the first post.

It was deceiving because I checked multiple times and they seemed tight, but it doesn’t take much slippage to translate to a big problem in your cut. Here’s my original post describing the problem:

Switching to better set screws with a dot of low-strength thread lock is a simple and inexpensive solution to try.

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Hi all, thank you sooo much for all of your thoughts and considerations with regards to my multiple issues. I apologize for the delay of my response, the on button on my laptop fell off (what?!) So I was out of the game until repaired.

But that gave me time to order and receive a 1/8" downcut endmill. Also did an all over screw tightening check and retightened the right pulley strap again (I have the 4 screws fully engaged, dont know how/why it keeps slipping).

All of this combined did make a nice cut, so im gonna close this chapter here. Moving forward, i’ll just keep an eye on all screws/looseness (lock tight is a good idea) and just forget about that dang original endmil and blame everything on him.

Again, really appreciate all of the feedback, I couldn’t have worked through it all without you.
Thank you!

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