Holding tabs, Rest, 2D contours

[lindsay.fowler]

Hi All,

I'm trying to wrap my head around Rest, and I really haven't found a clear explanation yet, so my question might be a bit misguided.

From what I understand, rest machining allows you to optimise the time taken for a job by taking into account what has already been machined. Please stop me there if that is incorrect.

My part is to be cut from stock using a 2D contour. I use 2D contour because it's the only operation with holding tabs. How else can I hold the part?

I decided to do the pocketing and adaptive clearing first because I reasoned that it is best to have a good strong hold on the part during these operations.

Then I did a 2D contour with holding tabs to finish. I ticked rest and was a little confused by "Tool Diameter". The tool tip (pun absolutely intended)  says the tool diameter is "the diameter of the rest material tool" - not very helpful - what does that mean? 

From my reading, and experience, it seems 2D Contour does not do rest machining very well. Indeed, the job I am doing now is doing 40 min of cutting the air, despite the fact that I tried to enable rest.

So the question is, what order of operations should I do to optimise the cutting of this part while still using holding tabs?

Must I do my 2D contour first?

Why can't 2D contour take into account the 3D shape of what has already been machined?

Why is there no 3D contour with holding tabs?

Is there a better way? - because this job time should be taking 25 minutes, not 1 hour and 30 minutes.

Thanks for any attempt to clarify this for folks like me who are struggling! Ta

[LibertyMachine]

"Rest Machining", in regards to 2D Contour, applies mainly to small internal corners, such that you wouldn't want to machine the entire part with that small of a tool. So, we rough it out with a larger tool and come in again with a small tool and turn on "Rest Machining". In the "rest machine tool" field, we enter the size of the tool that roughed all the material away.

3D Contour does not support tabs, although it has been mentioned on more than one occasions. But really, this part doesn't present a good application for 3D anyways

With tabs, one of the better "tricks" you can do is this:

Do all your machining, roughing, contouring, slotting, 3D finish work, all that stuff, but stay off the bottom of the part by the thickness of your tab height. Make the very last operation a 2D Contour with Tabs setting to just cut the part out. All we want to do at this point is cut the perimeter of the part with the tabs, not the entire sidewall profile. So, apply a bit of "Radial Stock to Leave"

You are right, your cycle time should not be that lengthy. Do you mind sharing the file?

File > Export > Save to local folder. Return to thread and attach the .f3d file in your reply

[lindsay.fowler]

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Thanks for your quick and helpful reply LibertyMachine,

It makes sense that rest machining in 2D contour is for corners and that clarifies why the size of the bit that was used before is needed... Although to be honest, I was expecting F360 to be much more intelligent than that and actually make decisions based on the current tool and the remaining stock.

I wasn't sure of this bit though:

@LibertyMachine wrote:

Do all your machining, roughing, contouring, slotting, 3D finish work, all that stuff, but stay off the bottom of the part by the thickness of your tab height. Make the very last operation a 2D Contour with Tabs setting to just cut the part out. All we want to do at this point is cut the perimeter of the part with the tabs, not the entire sidewall profile. So, apply a bit of "Radial Stock to Leave"

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I tried this, but the final 2D contour wanted to do 19 laps of mid air cutting... Am I supposed to restrict its starting height in the heights tab? Again, it seems silly that F360 can't look at the stock remaining from all previous operations and create the tool path that just does the last lap around the part..

I am also not understanding "Radial Stock to Leave and why we would apply it when I want to cut the part out.

Thanks, I'll attach my file and maybe you can show us.

[LibertyMachine · Accepted solution]

All of the 2D toolpaths (except Chamfer) in Fusion are not "model aware". They will do exactly what you tell it to do with no regard for where there is or is not material. So yeah, long cycle times if you don't define and constrain properly

Regarding the tabs bit;

[lindsay.fowler]

LibertyMachine, thank you.

That was really great. Thanks for taking the time to demonstrate those steps in an informative video, using the very part I was working on! I really appreciate it.

Very helpful!