V-carve Engrave vs 2D Countour "issues"

[rkeyqq]

Hi all, 

Sorry for the noobish question, but It seems to me I do something wrong.

The goal: 20-degree v-carve along curves, need to determine the best depth of a carve (as well as the best speed/feed)

Material: polycarbonate or it might be a plexiglass, not sure if there is a difference.

The issue: 

The engraving operation does not allow me to select open contours.

The 2D contour operation does not allow me to use multiple depths.

The 3D contour seems to be an inappropriate operation.

The Trace will not work as I am not sure yet what must be the depth, so I need to change the Z height of a sketch for experiments. 

So I'd like to select my curves and then set something like -0.01mm from the top per tool run and observe the results. The current output is ugly and probably wants some finishing paths or less depth or I don't know.

Thanks for any hints.

[seth.madore]

2D Engrave requires two closed contours to calculate properly. 

Trace could work if you had a sketch that contained X/Y/Z motion

2D Contour will only give you a fixed Z depth

Does that answer any of your questions?

If you could, please share your file here so we can poke at it a bit more:

File > Export > Save to local folder, return to thread and attach the .f3d file in your reply

[rkeyqq]

Hello and thanks for the reply.

My question was mostly about how to achieve multiple depths for the opened contours in a single tool path for calibration purposes.

If there is no option what would be the best way to determine carve depth? Like drawing 10 lines with different depth offsets? 

I also would like to do somehow a finishing almost polishing path to "clean" the carves. Is it achievable? Because the tool path is not steady and in my case could melt the plastic in corners, for example. While adding the feed rate destabilizes the router head. Multiple depths should help I believe.

Thanks

[seth.madore]

Melting plastic could very well be from running the tool too fast. Even though plastic can be relatively soft, that doesn't always translate into max rpm speeds or max feeds. To do a "cleaning" pass, typically I would just use "Repeat Pass" in the toolpath.

For calculating the depth, it's simple trig; a depth of .001" will result in a top width that is .0008" across

[rkeyqq]

Honestly, I have a cheap and not rigid CNC router with ~10000 rpm

I took some values from the internet and am now trying to play with them and find the best outcome. 

I determined that the machine does chips instead of melting in between 1000-1500 mm/min (~40-60 in/min) with some stepdown (forgot the number actually). When I increased the stepdown the machine sometimes stuck a bit for a moment melt a piece and go further. But at the same time, I want to understand what line width I need. Like .0008" tells me nothing, would it look nice for that small model? Do I need wider or narrower? Who knows.

So my idea was to set up multiple depths with a minimal step-down and just watch the desired output. Then find speed and feed for that particular depth and do two paths: rough and finishing. 

In the current case, I probably need to set up just a closed contour for my tests to determine line width and then do the final model. Not an issue, just a time-consuming process.

I just was surprised why on earth engraving works only for the closed contours, while having the same label "select contour" and the contour does not have multiple paths. Seems strange to me, but I am not a professional anyway 🙂

Thanks 

[seth.madore]

The Engrave toolpath looks at the distance between two closed contours and then does the math regarding how deep the tool needs to go, no other input is required. There is an option in that toolpath to have "multiple depths", one needs to just turn it on.

In the 2D Contour toolpath, we also have a Multiple Depths option, again, one needs to just turn it on:

 

[rkeyqq]

Well... I don't have it. I am using a free edition, could it be related?

[seth.madore · Accepted solution]

Oh, right. That goes away when you've selected a chamfer tool. If you define your tool as a Tapered Mill, it should come back

 

[rkeyqq]

That was unexpected 

Thanks a lot