A Matter of Trust

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A Matter of Trust

Postby BigC » Sat Nov 02, 2019 2:46 pm

Just a quick question. I have cut a few 3d models recently (luckily from MDF)
Sometimes the finished product needs a little tweaking usually height relationships
Does everyone run tests first or are they professional enough to go with what the preview is showing?
Even though my previews look ok I'm finding that I really need to fine-tune more often than not
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Re: A Matter of Trust

Postby TReischl » Sat Nov 02, 2019 3:38 pm

Obviously I don't know about everyone else, but. . . .

As I cut more I started to get a better understanding of what the final result would look like. In my case I tended to cut things too deep, especially lettering. It looked a lot better in a preview but the execution can be a pain not to mention if it is going to be painted.

One of the issues with "carving" on a cnc is shadow lines. I have written about this before but I will repeat it (that is what old guys do, repeat themselves). The issue is that a cnc machine when doing 3D work that requires a ball nose bit does not produce a sharp shadow line. When we look at a carving what we see are shadows and shadow lines, that is what tells us about depth. That rounding by the ball nose causes what should be a sharp shadow line to be muddled up a bit and the result is it never quite looks right. Of course that is also dependent on the intended viewing distance vs the radius of the ball nose cutter. Things that are to be viewed from far away need to be cut deeper.

Myself? I have no problem picking up a gouge and sharpening things up. My thought is that the idea is not "oh, look, my cnc did this completely! Isn't that great?" It is more like "I created this and I want it to look right and if that takes using a few more tools, so be it."

As you do more things you will start to get a better feel for how deep you need to cut vs the size and viewing distance of the project.

A good example is a skrat carving I have in the shop. It is not very large, skrat is all of about 3.5 tall. (Skrat for those who do not know is the crazy prehistoric squirrel the Ice Age movies). It is not very large but it is cut very deep, about 1 inch overall. He is typically viewed from about 4-14 feet in distance. With that depth his shadow lines allow him to be seen easily from 14 feet away even though he is small.

The other thing that can really help with a wood carving that is not painted is glazing. The darker glaze helps with the shadow lines a lot.

I am sure a lot of the other folks will wander by and share some of their techniques and observations.
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Re: A Matter of Trust

Postby mtylerfl » Sat Nov 02, 2019 4:12 pm

FWIW, I don’t run “test carves” of any project at all. I’m personally very confident and comfortable with the Toolpath Preview.
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Re: A Matter of Trust

Postby mezalick » Sat Nov 02, 2019 5:39 pm

I agree with Michael.
I rarely run test files, unless it's an extremely complex model.
Just my 2 cents.
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Re: A Matter of Trust

Postby Rcnewcomb » Sat Nov 02, 2019 5:45 pm

I rarely run test cuts now, but I've been doing this for 14 years. The preview is 99.999% reliable.

However, when I started, there were no mistakes, only test cuts. <wink>
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Re: A Matter of Trust

Postby Mark Bolton » Sat Nov 02, 2019 6:19 pm

Something you might consider is using a program like Sketchup (not promoting it in any way) to import your 3D model or do some of your concept design for 2.5D, Vcarving, and so on, for proofs. I personally have a tough time feeling super confident about what I see in the VCarve preview even though I know its dead accurate for whatever reason the display and resolution just doesnt give me a dead clear "feel" for the output. Then if you add in the fact that you may have a job with a 3D object in it, some text carving, some edge profiles, and so on, that are all going to be different colors, finish treatments, and so on, it can be nice to see it in true 3D.

I model most any complex object in SU and apply colors and materials as needed to supply to the customer so they can get a good feel for what the end result will actually be. I can apply shadows, and all sorts of other effects to help visualize the end result. It has saved me miles and miles of problems in that we can orbit around a model and tweak stuff as needed.
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Re: A Matter of Trust

Postby BigC » Sat Nov 02, 2019 11:06 pm

Thanks, everyone for your input
The conclusions I am gathering from this thread suggest that the more experience you have with the software the better you are versed in trusting the previews (which you say are 100% correct)
This is what I've come to suspect.
As a newbie, I'm still on a learning curve so I don't exactly trust my own decisions or calculations within the software. as time progresses and with the help of many experienced forum members and Vectric tutorials and FAQ's one day I may be able to go with what I have
initially selectively entered into the selection boxes. For now, I'm thankful for MDF (which I know is far from the best medium to get a nice looking carve)
Thanks for all your replies
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