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OptiRough Stock On Angled Surfaces


Jake L
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This one's tough to explain so please check out the sample file. Basically in a 3D OptiRough toolpath, when leaving a different amount of stock on the face vs the walls the tool doesn't seem to respect both values when milling an angled surface. I think I'm misunderstanding this, unless there's a magic button I don't know about?

The OptiRough toolpath in the file leaves .050 on floors and .020 on walls. What I would expect is something like this:

image.png.832e8c2145bf6c9074b9f3235be55c2c.png

Meaning, if I were to rotate the part and cut the angled face with the end of an end mill (as shown in picture after verify picture), I would not have any marks left behind from the OptiRough operation. However, when I create a stock model or run the two toolpaths thru verify, I get this:

image.png.98daecebeb55a240a740997c60d37f3e.pngimage.png.f1684aa5a1f24617cfec74d15c6d4cb0.png

In conclusion, what am I doing wrong here? If I want the OptiRough operation to leave enough stock so the 2D contour operation to clean the whole face, what do I need to do? Thanks in advance for any information anyone can provide. MC2023

 

OptiRough_Stk_Left_On_Angled_Surfs.mcam

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Program some of this stuff by hand and get a really good idea of what tangential intersection is. Then you will be able to wrap your brain around the process of tool pah calculations. Wall is Vertical in my understanding, but with angled wall you have to look at where the tangential intersection of the radius of the bull endmill will be at the relative point of the Z setup to then see where it falls into place. In your example if i wanted an even amount of stock across that face for a finish operation for a mold surface I would come in leave finish stock cutting with a semi finish operation. Each of the scallops left from opti-rough leave places where tool pressure will not be even. That will translate back to the finish surface even with a flat endmill. A lot of people forgot even the biggest diameter Carbide tool has deflection. I have seen this debated many times over the years and I was fortunate enough to watch someone do something dumb early in my career. They were making a plastic prototype for Kenwood that was a speaker support. They were surface machining Delrin with a 1/4 carbide ball endmill. They didn't pay attention in the CAM software to the shank rubbing as they were coming up one wall. I sat there and watched a carbide endmill bend almost 30 degrees over and not break several times. I thought I was losing my mind seeing this endmill flex like it did and not break. Finally after about 5 minutes of watching this I stopped the program and got the shop foreman and owner who programmed it and had them watch it. We all three sat there dumbfounded. Then a couple years later I was on a nuclear turbine deck helping rebuild the packing that goes between each diagram segment. I was asked to do the sine formula for the amount of movement that 140 ton almost 100 foot shaft that was 36" diameter would move when being fired up. I did the math and come with .020" we then had to make our packing clear each section with .010" more clearance for a total of .030" That was how much that thing moved. I have plenty of other stories from using 11 flute endmills over 7 flute endmills and getting .0002" taper out of part we couldn't over come with the 7 flute endmill.  

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On 6/2/2023 at 4:12 PM, ajmer said:

this might explain things

Thank you ajmer! That was an incredibly helpful video.

 

On 6/3/2023 at 9:29 AM, crazy^millman said:

In your example if i wanted an even amount of stock across that face for a finish operation for a mold surface I would come in leave finish stock cutting with a semi finish operation. Each of the scallops left from opti-rough leave places where tool pressure will not be even. That will translate back to the finish surface even with a flat endmill. A lot of people forgot even the biggest diameter Carbide tool has deflection.

That makes a lot of sense, and it isn't something I had thought about. Luckily, in this situation the toolpaths in the sample file are for a rough operation. In the future this will definitely be in the back of my head.

The couple example stories you gave were mind boggling. I can't imagine seeing a 1/4 endmill bend over like that. And I never would of thought a shaft that size would have that much movement, honestly I wouldn't have expected any movement at that scale.

 

Here is another copy of the original file with the "solution" to my question Mcam File . I added a second machining geometry group for the non-flat faces and input .050 for stock to leave on both floor and walls. This is also my first time using Dropbox so please let me know if I did something wrong.

Thanks again for the replies!

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