Inefficient 2D adaptive clearing toolpath

[SGoldthwaite]

I crated a circle-diamond-square object that I want to use to calibrate my desktop CNC router (Shapeoko).  I used the 2D adaptive clearing and the toolpath it created seems very inefficient.  The tool keeps lifting up and jogging over to the start of the next section when it seem to me it could change direction and keep cutting wihout all the jogging around.  It's especially obvious when it's clearing the stock around the circle.  Is there a some setting I can change to make the toolpath more efficient?  Here's my model:  http://a360.co/1EGP29C

BTW - this forum website is very very slow at the moment. 

[fonsecr]

Adaptive is very different from a normal pocket/roughing strategy. Adaptive ensures that the tool maintains an optimal engagement for your cutter which again means that you can run as much higher feeds while reducing tool wear significantly at the same time. Normally you would do very deep axial cuts while only shallow radial cuts. But in total the material volume removal rate will surpass that which can be achieved using a conventional roughing strategy several times regardless of the extra retracts. However, CNCs do need to have high feed capabilities and you should be cutting relative hard materials so your spindle load is close to its limit. For it might be that you should just be using the Pocket strategy in your case - at least if you cut very soft materials. Depending on the part being machined you can avoid some retracts by tweaking the Staydown feature on the Linking page. The slower your CNC executes the retracts, the more you want to force the cutter to staydown.

René

[SGoldthwaite]

I'll try a pocket toolpath.  I'm cutting wood and for this part, I can probably cut faster then my CNC router can go.  The router max feedrate is about 20 ipm.  

[Anonymous]

HI!

I also have a Shapeoko (2; with grbl 0.9g, the acme z-axis and DWP611, but otherwise stock) and I find that it's best to create both a pocket and adaptive clearing op and compare the time.  The Shapeoko is not very ridgid and I think much of the advice here is for much more ridgid machines.  That said, if you allow for a finishing pass, you can go quite a bit faster with adaptive even if it means you get some chatter or deflection.  

For instance, in hard wood I was able to run about 60 ipm with a 1/8" 2 flute in adaptive clearing without missing steps, but had to drop to 30-35 ipm when using pocketing.  

On the Shapeoko:

• For adaptive, I use a stepdown = to the bit diameter and optimal load ~ 0.3-0.4 of bit diameter.   I haven't tried to push faster than about 60-70 ipm but imagine it could be done depending on material.
• For pocketing I tend to use 40% of bit diameter as step-over and 1/2 the bit diameter as step-down.  I use this feed/speed calculator as the one in fusion doesn't support the materials I use (wood and tooling board), but in general this ends up being about 30-40 ipm.
• I set Stock To Leave at about 0.02" and I think this is enough allowance for some deflection as these high speeds.

This is with some limited experimentation.  Also: I've had no luck at all with climb cutting on this machine.

I think adaptive tends to do best on parts with access to cativites from one or two sides.  Otherwise I think it gets trapped in pockets and ends up making lots of rapids that don't make a lot of sense.  Here's a good example where it made some silly decisions like these weird stub cuts up what should be a perfectly vertical wall:

If it hadn't done this it could have easily been half the machining time (which was about 30 mins).  The corresponding pocketing operation at 37 ipm was about 40 mins.

One final thing to be aware of is if you have any alignment / squareness / deflection issues at all you may want to avoid long stay-downs, particular those that go "over the top" of a part.  These will leave tooling marks and maybe gouges.  

Hope this is at least a little bit helpful.  Let me know how you make out!

-c

[Anonymous]

Here's an example where I experimented with both pocket and adaptive.  I didn't copy your geometry here, I just made up some arbitrary dimensions.

In this case the adaptive tool path is about 35 mins and the pocketing path is 55 mins.  I used the same basic parameters as I described above.  The key here was setting the stay down settings on the last tab:

This results in this more reasonable path:

The long stay-down distances avoids slow rapids, but note that in this case none of the toolpaths go "over the top of the part".  If you were to see green lines crossing z-levels (particularly on curved or highly pocketed- parts), you may want to reduce the stay down settings.

I was more conservative with the feed settings here (~30 ipm), but the adaptive still wins. 

F&S for Adaptive (deflection of 0.0054")

For pocketing (deflection of 0.0069")

-c