Using scallop to control stepover doesn't appear to be working with 3D/Planar

[surfcam_ken]

I am hoping someone can explain why I am getting two different toolpath between 3D/CUT over 1 extruded surface and 3D/PLANAR cutting over 5 surfaces that have the same size and shape as the extruded surface?

I am using the same ballmill tool on both, with the same scallop height set on both, and leaving the same amount of stock on both.

I ended up sending the 3D/CUT toolpath out to the mills, because it did not have the big stepover in the corners as the 3D/PLANAR toolpath did.

I am concerned about this because there is going to be a time, when my only option is to use a 3D/PLANAR toolpath cutting across multiple surface's and I am going to have to be able to trust I am getting a .0001 scallop height, and it seems at this point only 3D/CUT does this correctly.

Thanks, Ken

[Yossi]

Look like your surface is too "simple" for planer.
Try this :
Switch to Step type : increment and enter a small number,
Change Surface tolerance to a smaller number.
Let me know .......

[surfcam_ken]

Originally Posted by Yossi Look like your surface is too "simple" for planer.

Thanks, that's a good one. I've never heard that one before.

[Judge Leo]

I have seen this when planar cutting many times, the tool path will "jump" over the transition to the next surface.

I often use the "project" tool path. I create a 2D pocket path, then project it onto the surface. It keeps your end mill climb cutting, extends the tool life and delivers wonderful results.

One hint though, when cutting an inside pocket with vertical walls leave a small amount in the 2D path, say .001" so the 3D path doesn't "climb" the vertical walls of the pocket. I usually finish the vertical walls with a 2D or 3D finish path first, then project onto the face.

Project also works well to "clean up" surfaces that other tool paths won't finish properly.

[scubanick]

Originally Posted by Judge Leo I have seen this when planar cutting many times, the tool path will "jump" over the transition to the next surface. I often use the "project" tool path. I create a 2D pocket path, then project it onto the surface. It keeps your end mill climb cutting, extends the tool life and delivers wonderful results. One hint though, when cutting an inside pocket with vertical walls leave a small amount in the 2D path, say .001" so the 3D path doesn't "climb" the vertical walls of the pocket. I usually finish the vertical walls with a 2D or 3D finish path first, then project onto the face. Project also works well to "clean up" surfaces that other tool paths won't finish properly.

i got the project part..i never knew you could prject a 2d path into a 3d path.. that will come in handy... but i dont understand this...
do you think you could post an example?

Originally Posted by Judge Leo One hint though, when cutting an inside pocket with vertical walls leave a small amount in the 2D path, say .001" so the 3D path doesn't "climb" the vertical walls of the pocket. I usually finish the vertical walls with a 2D or 3D finish path first, then project onto the face.

[surfcam_ken]

Thanks everyone, for taking the time to answer

Originally Posted by Judge Leo I have seen this when planar cutting many times, the tool path will "jump" over the transition to the next surface.

I was concerned about that being the case. This is not good as we cut a lot of 3D parts and we need to have the same scallop height over the entire 3D shape. either .0001", .0002" or .0005"

Originally Posted by Judge Leo I often use the "project" tool path. I create a 2D pocket path, then project it onto the surface. It keeps your end mill climb cutting, extends the tool life and delivers wonderful results.

I have used project before, but you can not set a scallop height with Project. So you end up not really knowing that you have a .0001" scallop height over the entire 3D surfaces.

[jeff1000]

You can try 3D Offset.

[surfcam_ken]

Originally Posted by jeff1000 You can try 3D Offset.

I will give that a try.

But why is 3D planar not working correctly? It has a setting to control scallop height over multiple surfaces, but it does not appear to work 100 per cent of the time.

And others appear to be seeing the same thing at their sites.

On the "to simple" example I am showing this should be a no brainer for any 3D CAM system with this scallop height option. If it does not work with 3D Planar over multiple surfaces, then it should be fixed to work correctly or removed as a option.

My Surfcam rep has not yet responded to my email on this, dated 5-21-07

[moldcore]

I do a lot of multiple surface machining and see this all the time. At first I was bothered by it but upon closer inspection I found that the area that appeared to be skipped over was actually within the specified scallop height. If it still bothers you, try rotating the planer direction enough so it’s not parallel with the surface seams. Sometimes using a flow surface to control the cut direction will tighten up the gaps, but not always. The 3D offset works good also but can take time to generate the tool path and most of the time it’s no difference than a projected one.

[surfcam_ken]

Originally Posted by moldcore I do a lot of multiple surface machining and see this all the time. At first I was bothered by it but upon closer inspection I found that the area that appeared to be skipped over was actually within the specified scallop height.

Thanks for all the input. But my original question is still not being answered. Please look at my two examples in my original post. Then explain why the 3D CUT toolpath and the 3D PLANAR toolpath look different. They should be the same toolpath in this example. One of them is not cutting correctly. And I believe it is the 3D PLANAR toolpath that is not correct. On another part with a different shape entirely, that we cut here, there was a large scallop left after using 3D PLANAR because of this issue with edges and multiple surfaces. It is beginning to look like this is a known SurfCam issue that their software developers will have to correct. Still have not heard a thing from my SurfCam rep. on this issue.

[surfcam_ken]

Originally Posted by moldcore I do a lot of multiple surface machining and see this all the time. At first I was bothered by it but upon closer inspection I found that the area that appeared to be skipped over was actually within the specified scallop height.

moldcore, you may want to take a even closer look the next time you see this. You just might end up being bothered by this as I am beginning to be.
I was able to determine that in the example I am showing in my original post. The scallop that SurfCAM is leaving using 3D PLANAR is .0018", I need .0001", I had the scallop height set to .0001" in SurfCam.

[moldcore]

Ken,

Don’t hold your breath. I’ve seen this for as long as I can remember, 11 years at least. Yes I have seen your example and I see it everyday here. I just feel its not that big a deal and easily worked around. Like I said before, I’ve checked those “gaps” and they’re not as bad as it appears. I do understand that some controllers on older machines really slow down if, using your example, you were to rotate the planer direction angle to 45 deg, from where you have it now. On newer machines the cut times are close to the same regardless of direction but the files are larger.