2.5D Cutting Issues

[Smooth90]

I am trying to cut 2.5D parts using meshcam and emc2 but I have hit a few minor snags.

First off the cutting time takes FOREVER for a simple part. This is because it is making many passes and I am not sure how to reduce it. I'm cutting a .35in thick LDPE cutting board and should be able to tackle it in one pass at most two.

*Look at the picture showing the tool path

Second I continue to get cut lines on the top of the stock (during the first pass only) when it goes to cut internal pockets and holes.

*Look at the pictures of the two white plastic parts - the black circles show where to look.



By robofreak at 2010-12-29


By robofreak at 2010-12-29

Now I think that the computer messed up somewhere because these plastic pieces look a bit odd in places (not meshcams fault). Probably due to high latency in emc (old computer). However the dragging in the pictures is different the issue is that its not raising the tool enough before it moves.


By robofreak at 2010-12-29


By robofreak at 2010-12-29



So do you guys have any idea how to fix this problem????

Thanks in advance!

[ger21]

First off the cutting time takes FOREVER for a simple part.

That's because you're using a program designed for cutting 3D meshes for 2.5D parts. Plenty of 2D programs will give you faster, better results.

However, a lot of MeshCAM users cut similar parts with acceptable results, using waterline and pencil toolpaths.
I've been a MeshCAM user since the very first beta, but I can't help you with those settings, as I'd use a 2D CAM program for a part like that.

Regarding the gouges? Is you're stock set to the correct height in the stock setup dialog?

Actually, it seems like the problem would lie elsewhere. All the red rapid lines in the MEshCAM display should be at the same Z height, but only a few of them gouged you're part. Perhaps the machine is losing steps?

Looking at the screenshopt again, though, it looks like the white stock outline is lower than the top of your part. So maybe it is a stock setup issue? Or a Z zero issue?

[Smooth90]

Well I fixed problem number two just a second ago ger21's reply got me thinking and I started looking at the meshcam tool path (first photo). I noticed that one of the yellow lines goes all the way across the top of the stock and matches the gouging on the plastic part perfectly.

I've highlighted the tool path in question in red.


By robofreak at 2010-12-29

Then by checking this box


By robofreak at 2010-12-29

I was able to get that pathway to disappear in meshcam when I generated the tool path.


Here is another picture showing the tool path after I checked the box (notice the yellow line is gone).


By robofreak at 2010-12-29


I haven't tested this on my machine yet but it looks like the gouging should stop.

I was looking at cambam as a 2.5d cutting program but if meshcam can do it I just can't justify spending another $150 on software.


This was the most serious problem now its just how long it takes to cut. If its not possible now it would be nice if in the next few months a feature could be implemented to allow reducing the number of passes.

[ger21]

Increase the step down on the waterline. That controls the number of passes.

[robgrz]

I used to recommend that users get a different program for 2.5D work but I've found that I never even open up my copy of OneCNC anymore for 2D projects- MeshCAM is capable enough for my 2.5D needs. (Although I may be biased and Gerry and I disagree on this one.) The only time I need to go out of MeshCAM is if I have drilling which MeshCAM has no way to do.

I did post a quick overview of the correct way to do 2D/2.5D at Using MeshCAM with 2D Objects . You seem to have figured most of it out so it may not be too enlightening.

If you're using the latest MC releases then the gouges are probably related to an incorrect zero setting at the top of stock. There was a bug like that at one point but it should be long gone by now. If not, please send me the specifics and I will fix it asap.

-Robert

[ger21]

I did post a quick overview of the correct way to do 2D/2.5D at Using MeshCAM with 2D Objects .

You should have a link to that page on your site. I've never seen it, and it would be handy to direct users to, as this comes up very often on your forum.

In my defense, I did point out that a lot of people use MeshCAM for this stuff with good results. I just happen to use a program that I wrote.

[robgrz]

Do I hear the banjos of the dueling programmers? Actually, I always restate your (or anyones) difference with me because I never want to appear like some of the other guys who answer every question with a recommendation for their software.

The article is linked on my site under the poorly-named "Photos" section. I've just recently started adding more content there and I need to rename that section to make it more clear. Oddly, new visitors are drawn to the "Photos" title while returning visitors/users tend to ignore it.

-Robert

[900steve]

Robert,
Great article, very helpful and actually what I have been looking for.

-steve

[adprinter]

The only time I need to go out of MeshCAM is if I have drilling which MeshCAM has no way to do.
-Robert

Drilling IS possible using MeshCAM Art. IF you are using a cutter with the desired diameter for the hole. What I do, (during artwork creation in Corel Draw) is simply create a circle at the desired location on the image in a unique color. Define the circle with something really small like 0.001" diameter, and use the Shape Editor to set that color to cut at a 1 degree angle, to the desired depth of cut. (No Limit) Works for me (but then, I am only working with wood). Even if you need a larger hole diameter, than the diameter of the tool you are using to cut the piece, it is still a handy practice for properly locating the hole centers for later drilling on the drill press.

-Michael