Minimizing tearout on CNC router - wood types and other tips?


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    Default Minimizing tearout on CNC router - wood types and other tips?

    Doing some small rosettes for window trim on a CNC mill with a high speed spindle so flex of frame shouldn't be an issue. Tried it with a cheap cutter and some lumber yard wood and was pretty bad but proved out some things. Now wanting to do the final ones. Got a better carbide cutter and wondering what wood I should try. They will be painted and not wanting to spend more than I need to. No super fine details. Is poplar a good choice?

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    Last edited by Jim27; 01-16-2021 at 09:34 AM.


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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    Depends on the types of cuts you are making. Generally, harder wood will cut cleaner. I find poplar to be quite difficult, but it depends what you are doing with it. Also note that poplar can vary greatly in hardness, so you can get some boards that route very cleanly, and other that are terrible.

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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    any specific suggestions on wood that won't break the bank? Obviously finer grain will work better at least I think that's true



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    A good quality set of sharp cutters is far away the most important. Hardwood is better than soft - maple tends to cut fairly clean for me. Also, your finishing pass(es) can make a difference.

    Since you are painting them, you might consider MDF. It will take a little more prep for finishing - perhaps a bit of extra sanding. It cuts very consistently and will hold fairly fine detail.



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    Down cut spiral bit for a clean top surface.



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    Quote Originally Posted by pippin88 View Post
    Down cut spiral bit for a clean top surface.
    That is good for a lot operations, especially with plywood. He is doing carving which probably uses a ball nose bit. Might help with roughing, though.



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    Tulip poplar varies a bit,but the good stuff will work and basswood cuts easily.The problem with either is that you will get a fuzzy finish,which will still be many times better than the fuzz you will have on the machine after trying 3D carving in MDF.Whatever you choose,it will take a lot of detail sanding to get a good finish and certainly more time than it took to machine.It gets even worse if you aim for a clear finish rather than paint.I'm not saying it cant be done but it isn't as quick a process as you might imagine.

    The other thing to be aware of is holding a small workpiece in place while machining it.With a ball end cutter you have a strong chance that the tip will be digging into the spoilboard by an amount equal to the tip radius.Which obviously removes any restraint on the central section moving.I have often used tags to hold small jobs in place when 2D cutting and you may have software that allows boundaries to be set which will leave a portion un-machined so that it acts as a bridge to the body of the blank.Which will need to be cleaned up by hand at a later stage.



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    Let me give a bit more detail. I am using a V cutter not a ball nose. I also am not cutting the parts clear through. I am just putting a pattern on the face of a block that is precut. I am replicating some Anderson windows rosettes since I would like to add some that match what I already have and the prices are high. Plus it's an excuse to make something on the CNC router. Here's the shape.
    Minimizing tearout on CNC router - wood types and other tips?-rosettemedium-jpg

    I saw that the rosettes at the big box store I checked were made of maple so I picked up a small board to try.



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    OK, with a decent quality and sharp V bit, you should be able to get great results with that design. Even with the softer hardwoods like poplar/alder/... I'd definitely use a fairly thin finishing pass. By the way, if you are careful, you can dress a V bit with a couple of strokes with a diamond stone on each edge and get longer life out of it.



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    That looks like a very easy job,particularly if you have an engraving tool that matches the angle between the facets.It is important to have an engraving tool and not just a bevel too as the sharp point is important when determining the Z datum as well as when cutting the surface.



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    Default Re: Minimizing tearout on CNC router - wood types and other tips?

    Quote Originally Posted by routalot View Post
    That looks like a very easy job,particularly if you have an engraving tool that matches the angle between the facets.It is important to have an engraving tool and not just a bevel too as the sharp point is important when determining the Z datum as well as when cutting the surface.
    Very good point (no pun intended). The first tool I got from a big box store was a V bit but the point was only a sharp point when looking at it perpendicular to the flutes. When looking down the flutes the point was the full width of the carbide pieces. It made a small square channel at the bottom of the grooves. I picked up a better tool that comes to a point in all directions. They both matched the angle of the facets



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Minimizing tearout on CNC router - wood types and other tips?

Minimizing tearout on CNC router - wood types and other tips?