Strange and Unwanted Tool Path Generated

[mkilloran38SZU]

Hello Everyone,

I'm working on expanding one of our injection molds so its thick and have finally been I'm making chips this week. I have been taking off .010" each operation to get the desired expansion to .050" on the radius, .100" on the ID in the mold, without much issue until now. I'm going to take it do to .010" of the finished ID and decided to change the stepdown from .040" (default it was set to) to .005" to get a smoother finish and less polishing at the end. What I am getting now is that the tool path generated is mushrooming at the top, as in its going farther away from center than I want and its going to ruin the mold. Can someone help explain why its doing it and how to correct it? The walls have a 3 degree taper. My boss is worried it will make a radius at the top of the model and we cannot have that as it needs to mate to the other side of the mold. 

It will be Contour 6 is the specific operation in the file

[UTD7ZNYB]

That's because it's being machined using the tip of a ball end mill.

It can be avoided by using an extended body.

[a.laasW8M6T · Accepted solution]

This is a very annoying and unintuitive thing about avoid surfaces.(And Boundaries)

There is a tolerance that the toolpath works to and that means that it can work right up to the surface.

To prevent this from happening you can add a small radial clearance equal to the toolpath tolerance

On contour6(2) i show a different method using boundaries 

You must turn on Contact point boundary and use a negative additional offset equal to the tolerance

[mkilloran38SZU]

I tried extending the body and still getting the same thing. Is there something else I'm missing in conjunction with extending the body?

[programming2C78B]

Are you adding the extended body into your Model selection for that toolpath?

[mkilloran38SZU]

I extended it, kept them as two separate bodies and said to avoid the extension so it doesn't try to mill it. Not sure if that is correct thing to do.

[a.laasW8M6T]

@mkilloran38SZU I wouldn't bother with the extended body(It does work If you do it right though)

Just add the small radial(or axial) offset to your Avoid surfaces like I show in My file, much less effort

[mkilloran38SZU]

when I do that, it starts milling what looks like half an inch lower than I want. Does that look right or is it a visual glitch? 

Also thank you for helping

[a.laasW8M6T]

That is correct

You have a .5" ball nose so it starts where the contact point of the tool meets the work piece.

If you want to start higher but not have the tool roll over then use an extended body or surface and add to the machine groups

You will just end up cutting air for a while though

[mkilloran38SZU]

Awesome, this is what I was hoping to do. I'm going to give it a try and see how it goes. Is there a way to do a continuous flow, without the retracts and rapid movement, that aren't at the beginning and end, on what looks like the first lap around? (the red, yellow and green lines in my screenshot) With your knowledge, I feel like its a setting right in front of me and I don't realize it

[a.laasW8M6T]

Hi

Sorry should have had the clearance in the axial instead of radial(I found a bug yesterday while I was messing around so got distracted)

If you use 0.001 clearance it cleans right up

[mkilloran38SZU]

I change those settings and still have the same issue. Could there be another setting that could affect it? Again thank you for your help. I'm learning a lot more from you than from fusion help 

[a.laasW8M6T]

Ahh

Looks like I had increased the tolerance in the passes tab slightly too

Another option is to right click on the toolpath and go into compare and edit and change the surface triangulation tolerance to tolerance x0.1(default is tolerancex0.5)

I would also turn on smoothing, Much nicer code.

No smoothing, Thousands of points:

Smoothing on

very few points with nice arc moves

[mkilloran38SZU]

I already had smoothing turned on but the big thing I see is that you have the maximum stepdown as .0005 and I have it at .005. I tried both numbers and it still is happening. I didn't install and setup fusion here, a previous guy did, and he was very particular about things so I have no idea what he could have done.

edit: nevermind on the stepdown. i miss read it. we have the same

[a.laasW8M6T]

I have changed a bunch of defaults over the years to get toolpaths how I like, but I have just tweaked a few things on your file to get it to work.

see attached

You can upload this one and copy My good toolpath into your setup, then select both and right click, compare and edit and select different to see what the different settings are

[mkilloran38SZU]

Thank you so much for your help on all of this. When I copied your tool path, it lost what defined the bottom height. What did you have it set too so it can't change things: the bottom of the model or the bottom of the big radius?

Also, when I select what is different in the settings, the window is blank.

[a.laasW8M6T]

you have the file to see what selections I had too.

just look at at that to see what selected for heights etc, I haven't changed much from your original file in terms of that. 

[programming2C78B]

"the window is blank."
You probably only had one toolpath selected.