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Does F360 3D Adaptive Exceed Width of Cut in Outside Corners?

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Message 1 of 9
erikhardy339
344 Views, 8 Replies

Does F360 3D Adaptive Exceed Width of Cut in Outside Corners?

I'm currently running some long (9") shell mills in the mill that are sensitive to width of cut loading before they turn into a chatter box. During the roughing stage, I've noticed that every time the tool takes an outside corner it begins chattering. I can stop the feed, restart, chatter is gone. Next outside corner comes around - boom chatter. 

 

I'm running a 1.5" diameter tool with .05" stepover. I zoomed in on the tool path, and it appears the stepover is increased throughout the corner apex. Is there a specific setting that is causing this? 

 

corned adaptives.png

 

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Message 2 of 9

@seth.madore I made an example file and attached it.  I set the grid spacing to represent the .05" stepover distance.  Yes, it appears the toolpath exceeds the stepover in the corners.  Perhaps this is intended?  What do you think?

bradfrancola_0-1688298126700.pngbradfrancola_1-1688298156214.pngbradfrancola_2-1688298283683.png

 

Message 3 of 9

@erikhardy339 I reached out to some smart people and they schooled me on a few things (things I used to know but forgot).  F360 is calculating these Adaptive clearing toolpaths in a way that maintains a constant amunt of engagement between the cutter and the stock.  The center line toolpath looks like it is taking a bigger "bite" in the corners but if you watch the simulation very slowly, you can see what it's trying to do in the corners (maintain a consistent amount of engagement).

 

Here is a nice video you can watch if you'd like:  https://youtu.be/9fSTW8TG5WA

 

If the tool was perfectly rigid and had no deflection, you probably wouldn't get chatter.  But that may not be the case.  You can try to use feed optimization to reduce the feed rate in the corners.  Un check the "Only Inside Corner" check box and play with the Max Directional Change to control how much of the corners you want to be altered.  

bradfrancola_0-1688317001402.png

bradfrancola_1-1688317050191.png

 

 

Message 4 of 9

This is what would happen if F360 did NOT compensate the corners - the engagement would decrease considerably.  

Message 5 of 9


@brad.francola wrote:

 

 

If the tool was perfectly rigid and had no deflection, you probably wouldn't get chatter.  But that may not be the case.  You can try to use feed optimization to reduce the feed rate in the corners.  Un check the "Only Inside Corner" check box and play with the Max Directional Change to control how much of the corners you want to be altered.  

 


I guess the surface speed would be lower on external corners as the speed is the centre line of the cutter? So you might need a higher speed on external corners?

 

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 6 of 9

Hi @HughesTooling .  I know what you are saying.  But, my understanding is the F360 adaptive strategy attempts to maintain a constant load on the tool (even through inside or outside corners) so there theoretically should not be a need to change feed during corners.  But, this assumes the tool/holder/workpiece is perfectly rigid.  If there is deflection some of this "goes out the window" and then there may be a need to alter feed in the corners.  

 

If you go back to the initial post, you'll see the outside corners take a bigger "bite" than the straight line moves.  This change in engagement is the compensation for the outside corner.

Message 7 of 9

listening to my cuts / watching spindle load, i do believe the engagement is constant even in corners etc

Message 8 of 9
erikhardy339
in reply to: erikhardy339

Interesting responses, I appreciate the constant engagement goals. I'm wondering if this is a variable that could be tuned? 

 

For my extended length problem, I had to reduced the step over from .05" to .03" to eliminate the chatter during outside corners. Feedrate reduction had minor effects, In my experience the stepover has a greater impact on chatter than feedrate. 

 

I've run into this issue several times in the past. Back when I had a 40amp 20Hp Haas, I would tune a 3/4" rougher to be power limited. I would choose a stepover and increase the feedrate until the spindle rpms would start dropping and back it off a little. The spindle was happy with roughing cycles particularly on large interior cuts, but the spindle RPMs would start dropping around the external corners and I would have to drop the feedrates about 30% to maintain happiness. 

 

Another instance I've run into this problem was running an 1/2" Diameter Aluminum Roughers 2" LOC (Helical 82023). I followed the cutting parameters given by Helical and it immediately snapped a new cutter around the fist external corner.  I tried it again with another new cutter and same result, Sad day.  The bending load was way too high for the endmill. With the same cutting parameters, the rougher worked fine  on interior roughing cycles. 

 

I suspect the constant engagement is being too aggressive when dealing with outside corners, particularly the initial few passes around a sharp 90 degree corner? 

Message 9 of 9

What G187 smoothing setting are you using for roughing? That's also going to have significant affect on your roughing around external corners

 

If working with extrusion material (most bar stock, sheet etc) are you accounting for variable first cut depth when switching from X to Y direction?

 

When working with Helical recommended Speeds & Feeds I ALWAYS drop it to 80% and significantly reduce the radial depth of cut, especially at greater than 2xD. Curious what your settings were

 

For example if your programmed "stock" is 2.0" in X & Y but due to extrusion is actually 1.95" x 2.05" that first pass can be significantly more engaged and thus lead to that breaking. I add "false" stock to ensure that the first few passes are well outside the stock, so that subsequent ones are all properly engaged

 

I just yesterday took a 4340 Hard block with a 1/2" x 2" Flute length rougher and did .025" full flute length cuts using Adaptive strategy with great results, by ensuring my stock was larger than the actual workpiece it took a few passes for the X & Y 'engagement' to match from not perfectly sized stock

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