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2D Pocket Leaving Material

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Message 1 of 6
crjcaruana
189 Views, 5 Replies

2D Pocket Leaving Material

Hello,

 

I am having new to CNC manufacturing and am having issues with my 2D pocket. I completely understand my bed is not level- I have recently upgraded my cheap hobby CNC to the upgraded 6060 cheap hobby cnc, I plan on fixing that tomorrow. My question lies within a few spots shown in the picture below... where there is material left in the hexagons, but it's not a "ramp" like I'd expect to see with an uneven machine. There are 3 very distinct "cliffs" on every side; for example, the piece in the black circle has a "cliff" at 1 o'clock, 4 o'clock, and 9 o'clock... it is truly an island where the bit cut lower around the island.

 

Is there a setting I missed? 

 

I have recently posted yesterday, here is a link to that post with all of my settings: https://forums.autodesk.com/t5/fusion-360-manufacture/2d-pocket-adaptive-clearing-won-t-take-small-g...

IMG_7161.jpeg

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Message 2 of 6
a.laasW8M6T
in reply to: crjcaruana

That sort of behaviour comes primarily from tool deflection. 

This is a pretty common problem on low rigidity machines.

 

the factors that affect the tool deflection are generally depth/width of cut and feed rate.

 

2D pocket is generally used for roughing out parts but can also be used for finishing.

 

What I would suggest is to  use one 2d pocket operation to rough out leaving some stock, say 0.01"

then use another to finish the remaining material at a much slower feed rate.

 

Even on my 16 ton VMC at work I still rough out and then finish at slower feeds as tool deflection is an issue even on the most rigid machines(can't escape physics)

Message 3 of 6
crjcaruana
in reply to: a.laasW8M6T

Thanks for your quick response. With the cuts already completed, what can I do to finish this off? Add another 2D pocket (or 2D Adaptive) at a slower speed and disable multiple depths?

 

Also, for reference, I was cutting the last pocket at 32in/min, it took ~1.5 hours. What would you recommend for the next cut? Finally, with adding another action to this set-up, is there a way that the new set-up knows that the 1st was already made (I'm guessing Predrill positions would help?)

Message 4 of 6
crjcaruana
in reply to: a.laasW8M6T

I should also mention, I performed the exact same 2D pocket at 32in/min twice, each taking 1.5hours. The second time around it really didn't touch any of the material (Pine wood)- I thought it might help, but didn't.

Message 5 of 6
a.laasW8M6T
in reply to: crjcaruana

So now you have already machined with 0 stock to leave, if you want it to clean up you will need to apply a negative stock to leave value.

Turn off multiple depths too:

- stock.png

 

Then go to linking and change the ramp clearance height to 0, this will stop the tool air cutting above the bottom of the stock:

ramp clearance.png

 

Then in your heights tab change the top height to selected contours:

heights.png

If you had left stock in the first roughing operation then you would enter that amount in the offset value.

 

Another thing is your machine may not be able to move accurately at 32in/min im not sure, although for your application accuracy isn't particularly critical

 

see attached file

 

Message 6 of 6
crjcaruana
in reply to: a.laasW8M6T

I can give these settings a try tomorrow. Would the speed/accuracy of my machine at speed still affect the Z-height of some of these cuts, especially the second time around?
My thought before performing the code the second time was that if there was any affect from the material, it should correct itself on the second pass. Just for good measure, I’ll run a 2D Adaptive Clearing tomorrow.

Thanks again for your help

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