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why does raster rise and fall next to walls?


lowcountrycamo
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I have tried and tried to stop this but I can’t make it stop.  I’ve used containments spaced off the wall the tool radius plus an amount to no avail.  I’ve tried making the walls check surfaces with varying amounts of check distances all without success.  I use waterline for my walls and raster for my floors and just edit the gcode, a real PITA!

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I've seen this kinda stuff before and I've always chalked it up to a minor surface variation (tolerance, etc) that isn't worth spending my time on. The cut move likely takes less than 2 seconds. I'm not gonna spend time figuring out why it happens. You gotta pick your battles.

I *do* find it interesting that in your sample, the jump is right by that hole. If I found it too bothersome, I'd simply change my cut depths to a Z value not much above that floor value.

Anyway, nothing wrong with asking...

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I just did a similar but different part with no side hole.  I still rises but not so much.  And it rises differently on the other side.  I also attached a sample part if you want to look.  I am leaving 0. on floor.  .01" on walls.  Checking silhouette boundary only changes where it rises.  This is a 6al-4v part so I have a low feed plunge rate.  I use many of these raster ops so it will increase run time one a high production part where I am looking for every advantage. 

Thanks.

raster next to walls 3.png

raster next to walls 2.png

raster wall climb.mcam

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1 hour ago, skyking01x said:

Can someone explain  “associated to the avoidance surfaces” and “control surfaces” referenced in previous replies?

Avoidance surfaces are used in the newer format High Speed surface toolpaths, they are essentially check surfaces similar to what were used in the legacy surface tpaths. However you can have multiple avoidance surface groups selected with different values for stock to leave. In the HSpeed surface tapths you can also have multiple machining surface groups selected with independent stock to leave values as well

The issue with Low Country's part file of the tool climbing up the wall was corrected by eliminating the avoidance surfaces and changing the control method to a containment boundary. It all has to do with how the tpath is looking at the geom and how it effects the math, there was something about those surfaces that required the tpath to do a retract. Remove the offending surfs, retract is gone, need to find a different method of controlling the tpath along the edges.

 

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I see you already got an answer, but you could also limit the movement of the tool with "depth limits." I flowline a ton of external fillets on rod end linkage and for some reason it does the same thing moving in z minus below the edge of the fillet. I have to constantly set limits so it only travels along the surface. 

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3 hours ago, CJep said:

there was something about those surfaces that required the tpath to do a retract.

Those don't look like retracts to me. They look like cut moves that, for some reason, went up the wall. There's a difference. Just sayin.

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It is climbing to avoid contact with the wall avoidance surfaces when the toolpath puts it right against the wall surfaces and it thinks the tool is interfering, be it actual interference based on stock to leave or even a loose tolerancing issue or unseen sliver areas/non-perfect surfaces in the avoid selection.

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15 hours ago, CJep said:

semantics you know what I was sayin

I wasn't busting your chops...but it's not semantics. The toolpath going up the wall because the algorithm determined that it needed to (for whatever reason) is different than the tool retracting. Since your reply wasn't clear on which one you were referring to, I was just pointing out the difference. I'm not trying to take anything away from your reply, I'm simply adding to it.  :thumbsup:

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I have written about this problem in the Mastercam forums. There is no logic why it raster fails and unnecessarily raises up, or in my experience goes down. If it was a surface issue it would be repeated. But I have tested paths that raster fails on with old school surface finish parallel. And never has it failed for me. I wish they would figure it out one day. Broken quite a few tools to this flaw.

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8 hours ago, medaq said:

But I have tested paths that raster fails on with old school surface finish parallel. And never has it failed for me.

Completely different algorithms. The key to utilizing the newer paths is to not think they behave the same as the legacy paths, they don't.

It was shown already how it's simply how the tool was driven. I'm not sure it's a tool path issue but think it's more of bad user input.

JM2C YMMV

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Different algorithms or not, Raster fails a ton.  And I do not expect it to behave the same. But when one path was designed or added to replace a legacy tool path. I should be able to expect similar results and not crashes. Yes crashes, cause raster will for no apparent reason dive into material and break a tool. And no, it is not necessarily bad user input. I have posted on this to the mastercam forums on this same subject, it is currently logged as R-20372

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