(How) Can I engrave text with a vee-bit (V-bit)?

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(How) Can I engrave text with a vee-bit (V-bit)?

Postby cnczane » Tue Sep 27, 2016 4:03 am

(Firstly, I put in 'vee-bit' so you can search for it... Search strips out searches for 'V'.)

Is there a way to use MeshCAM to generate G-code to cut out "stroke-fonts" (I believe that's the name of fonts that are composed of center-line "strokes" as contrasted with "outline" fonts which enclose an area: google "Gerber fonts")?

I sure would like to use my friend, MeshCAM, to help me with this latest task.

Thanks.
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Re: (How) Can I engrave text with a vee-bit (V-bit)?

Postby Randy » Tue Sep 27, 2016 10:45 pm

The short answer is "no". The longer answer is that MeshCAM is a surface-following program (as opposed to a path-following program) so it needs 3D surface features to detect. The letters need to be in the form of a groove (the best, because then you can use Pencil finishing to trace them out) or a bump for MeshCAM to follow.

"Groove" letter strokes are best because the V-cutter tip is offset towards the centerline of the groove as MeshCAM traces out the groove, so you can approximate the appearance of a single-stroke engraving. With raised letters, the tip is offset away from the centerline so it will produce the equivalent of an outline font.

Randy
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
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Re: (How) Can I engrave text with a vee-bit (V-bit)?

Postby cnczane » Tue Sep 27, 2016 11:08 pm

tHANKS, rANDY, (AHHH, I SEE ONE OF THE KIDS HAS BEEN AT THE COMPUTER AGAIN! JUST A SECOND, I HAVE A POST-IT NOTE HERE SOMEWHERE REMINDING ME WHERE THE cAPSlOCK KEY IS LOCATED)

tHERE NO There!

Okay.

Thanks, Randy.

I guess I don't know what a Groove font is, but as I read it and got to Pencil Finish, I immediately thought of just stroking a black font in an image file and telling MC "black is down" on loading, and choosing pencil-finish. I'm going to try it.
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Re: (How) Can I engrave text with a vee-bit (V-bit)?

Postby cnczane » Wed Sep 28, 2016 4:34 am

I have a result which suggests it might be doable, after a fashion. The key is certainly in sizing a cutter small enough for MeshCAM to decide it can be fit into the necessary trench.

I ended up defining a 0.015" diameter ballnose, which I don't own, for this particular example, after getting zero-length paths for with the larger cutters I tried, starting at my accustomed 1/8".

If you look carefully at the pencil-finish paths in the attached screencap, you'll see they are somewhat disjoint--again, precisely what you expect from a 3D CAM trying to make a perfect rendition of trenches cut into the shapes of letters.

After getting ANY kind of a result, I was going to slap in a V-bit/vee-bit and take a look at the result. I might just pisk it now.

BTW, can a V-bit cutter be defined in MC with the taper field? Anyone got a tool defn for a standard cutter to share?

Thank you.
Attachments
PencilFinish.png
I asked for 40-degr waterline with the same bit as well, but nothing resulted. Note that the pencil path is erratic.
PencilFinish.png (175.15 KiB) Viewed 851 times
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Re: (How) Can I engrave text with a vee-bit (V-bit)?

Postby Doug » Thu Mar 16, 2017 10:12 pm

cnczane wrote:BTW, can a V-bit cutter be defined in MC with the taper field? Anyone got a tool defn for a standard cutter to share?

I'm trying to cut a guitar pickguard with a 45 degree bevelled edge using a Trend 1/4" diameter 90 degree V Groove bit. Of course, I want the tip of the bit to follow the outline exactly with no margin but guess what very naive newbie error I just made? Yes, I used a 1/4" bit diameter which then had the bit centre 1/8" outside the outline so the entire part ended up larger! :roll:

Does anyone know if it's possible to work around this, e.g. by defining a bit with a zero or very small (it seems to only accept minimum 0.001 mm) diameter say?

Answer... no, MeshCAM 7 crashes. :(

Setting the tool diameter to 0.05 mm with 0.05 mm machining margin and 0.006 mm tolerance did work although I had to use the 16 GB RAM MacBook Pro to calculate the main outline toolpath.

Doug
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