Adaptive Clearing - Initial Stepdown

[tnfjield]

I'm running adaptive clearing as a rough clearing pass for a relief carving.  I've got a woefully underpowered and flexible CNC router, so I take many passes with small stepdowns.  The adaptive clearing works pretty well except for the first z-level clearing pass -- it takes off too much material.  (So I get a lot of chatter due to the machine flex.)

I've set both my maximum roughing and fine stepdowns to 0.5 mm.  But the FIRST stepdown is about 1 mm; almost twice the maximum.  Please see the attached images.  The first is a closeup of the edge of the carving with the adaptive clearing toolpath visitble.  The machining layers are all 0.5 mm apart, but you can see the distance from the stock top to the first layer is larger.

Can anybody tell me why that is?  What am I missing?  Thanks!!

[johnswetz1982]

though not an answer to your question, you can choose order by depth and it will cut from top layer down rather than cut max depth and step up several times.

[engineguy]

@tnfjield 

Without a file to check settings this is a bit of a guess, going with 2D Adaptive Clearing here 🙂

Could be a combination of a couple of settings, one check your Stock size in your Setup, this setting usually defaults to a stock with a height offset if using a "Relative size box" so there will be (In Metric mode) 1.0mm of stock above the model.

Second is your "Top" setting under the "Heights" tab, if that is set to either a "Selected Contour" or "Top of Model" then that is where the 2D Adaptive goes to at the start of cutting, in your example if you have a 0.5mm stepdown and a 1.0mm Z offset in your stock then you would get a first DOC of 1.5mm so double check what is set for your stock and also your Height setting 🙂

In the images below you can see what the stock is set to in "Setup" and where the first DOC goes to, in the example I have a 1.0mm stepdown and a 1.0mm Stock Top offset and you can clearly see in the highlighted area where the first DOC is in fact -2.0mm. 🙂 🙂 🙂

Example file attached, hope it is of some help to you 🙂 🙂 🙂

Regards

Rob

[tnfjield]

Thanks, @johnswetz1982  and @engineguy.

@engineguy, I think your reply helped, but it also added to the confusion!  First, sorry for not uploading a file.  It's huge because of an imported STL and probably doesn't add much.  I could make a simpler version for the same example.  And I'm using 3D adaptive clearing, but I'm guessing the logic is the same.

You said that in your setup you have a stock offset of 1 mm above your model, and your stepdown is set to 1 mm, so the first cut is at 2 mm deep.  I understand the math, but I don't understand the logic.  For example, if I'm setup so that my stock is 5 mm above the top of my model, and my stepdown is set to 1 mm, then my first cut is going to be 6 mm deep?!  Why wouldn't the max stepdown be honored and the tool make several passes through the stock material, each at the maximum stepdown DOC?

I would understand the logic above if the Top in my adaptive clearing settings was set to top of model, but mine is set to stock top.  So I would assume that Fusion would think it needs to start removing material from the top of the stock, and would do it at the maximum stepdown per pass...

[engineguy]

@tnfjield 

You must have something else wrong, I have just used a 3D Adaptive toolpath and set the stock in the Setup to be 5mm above the top of the model and I have set the Top Height to "Top of Stock" with a 1.0mm step down and it works correctly, in my example here the toolpath does indeed do 5 passes of a DOC of 1.0mm so it takes all those cuts just to get to the model so I am at a loss to understand just what you are doing. See images below.

Can you do a small example file of how you are setting up your 3D Adaptive operation ?

Here is the Top Height setting

Here is the toolpath, starting 5mm above the Model

Here is the Simulation showing the first DOC is only -1.0mm and is way above the actual Model.

It works fine here 🙂 🙂

Regards

Rob

[tnfjield]

@engineguy

Thanks for confirming that it works like it should!

OK, I made a simple test file (just a block) and everything looks right.  The model is 3 mm thick, and the stock is 6.35 mm thick.  The maximum stepdown is 0.5 mm, and the first DOC is about 0.5 mm below the top of the stock.  This is what I would expect.  (The file is attached.)

Adaptive Clearing Test

Now in my actual file, I have it set up the same way.  (At least I think I did!  🙈)  The model is 3.387 mm thick and the stock is 6.35 mm.  The maximum stepdown is 0.5 mm and the Top Height is set to Stock Top with 0 mm offset.  The first pass is shown below.  It's at 5.36 mm, which gives a DOC of 0.99 mm.  I expected it to be at 5.85 mm.

Adaptive Clearing, Model

Here are my toolpath settings.  The Top Height is set to top of model, but you can see here the first DOC is larger than the 0.5 mm stepdown limit.

Toolpath Settings

Here's the stock setup:

I've exported my model and found it's only 35 megs, so I can actually attach it.  It's included below.

I apologize in advance if you find that I'm just doing something stupid!!  But I've looked and I can't find it.  This isn't the first time I've had the first pass exceed my stepdown; it's just the first time I'm trying to figure out what's going on!  Because I've got such a dinky router, doubling the DOC makes a big difference.

Thanks again,

Todd

[engineguy · Accepted solution]

@tnfjield 

Think I have found your issue, you have both the "Maximum Roughing Stepdown" and the "Fine Stepdown" set to 0.5mm, the "Fine Stepdown needs to be a lower value, if it is the same then Fusion does in effect two stepdowns, I don`t have an answer as to exactly why it does it but I have always set the "Fine Stepdown" to a much lower value so never had your issue, usually 0.1mm, see the image below, you will see that I have changed the "Fine Stepdown" from the 0.5mm to 0.25mm and it now works fine 🙂 🙂

To save all the uploading/downloading of big files just try making that change on your file and it should work OK now, do some tests with different values and see what suits your operations best 🙂 🙂 🙂

As you can see the tool now goes to the 5.85mm that you expected, hope this has helped you some 🙂 🙂 🙂

Regards

Rob

[tnfjield]

@engineguy 

Yup!  That did it!

And that is odd...  I usually set them to be the same...  Because they're roughing passes!  lol.  Even more odd is that the roughing and fine stepdowns were both set to 0.5 mm in my simple adaptive clearing test file, but the initial DOC was as expected there.

But I'll surely make it smaller from now on!  Like I said, sometimes (only sometimes) it would cut deeper on the first pass of a project, and I had no idea why.

Thank you for taking the time to figure that out for me.  I really appreciate it!

[daniel_lyall]

A suggestion model the stock, it can make it easier to see problems if you visually can see the material you just set opacity to the stock material so you can see through it, you can save your self some issues as you can see straight away something is wrong.

[tnfjield]

@daniel_lyall, thanks for the suggestion.  I've heard "model the stock" before, but I'm not sure I understand what that means, i.e. how it helps?  Could you clarify a bit?  

Would I model the stock material as a separate solid body (with the appropriate relationship to my model), and then for my setup I would just set the stock to that solid body?  This is as opposed to defining the stock dimensions in the setup itself, right?

I can see how that would work, but my stock is visible when I define it in the setup, too, so I'm not sure what it buys me?  Is it just that it's always visible, unlike the stock that is only visible when simulating or clicking on the setup?

[daniel_lyall]

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Would I model the stock material as a separate solid body (with the appropriate relationship to my model), and then for my setup I would just set the stock to that solid body?  Yes

I can see how that would work, but my stock is visible when I define it in the setup, too, so I'm not sure what it buys me?  Is it just that it's always visible, unlike the stock that is only visible when simulating or clicking on the setup?  correct, it can save doing a sim and finding it is wrong it is a quick visual.

Below you can see something is wrong before you do a sim to get it, it is just click click,(side view + toolpath) make a adjustment depending on the problem for you the first pass hight you only need to waight to the first toolpath is there its wrong next adjustment

First four hights looks good, let it finish.

If you model all parts into a setup like the stock, fixtures, vices, clamps it reduces the channces of a crash or haveing a big bobo, with 3D toolpaths if you pick what to cut and all bits are in the setup it should miss the clamps or what ever, it is basicly the direction fusion is heading (I do not know if this is going to be in the exstensions what will cost) where you model everything incuding the machine into a setup and when you do a sim it will show a crash where ever it is.

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[engineguy]

@tnfjield 

As your issue had me intriqued I decided to look deeper into just how the 3D Adaptive operates with the "Maximum Roughing Stepdown" and the "Fine Stepdown", it is quite interesting the way it does operate.

Basically you have the two stepdowns, Rough and Fine, the Rough steps down by whatever value is input and the Fine steps down in between the Rough step distances, now you all already knew that bit but next is where it does get interesting 🙂

First of all the value in the Fine stepdown must be 50% or less of the value of the Rough stepdown or the Rough stepdown toolpath is changed as follows, example, a Rough stepdown of 1.0mm and a Fine stepdown of 0.5mm or less will result in the Rough stepdown toolpathing out at the 1.0mm between steps, as we would expect 🙂

Now it gets strange, if I change the Fine stepdown to say 0.6mm then what happens is the extra 0.1mm from the 0.5~0.6mm is doubled and added to the Rough stepdown toolpath so instead of getting a Rough stepdown of the 1.0mm depth as input the 0.1mm difference from 0.5~0.6mm is doubled to 0.2mm, as this is added to the Rough stepdown we end up with a Rough stepdown of 1.2mm, which is not what we want 🙂 🙂

So, to sum up, if you want your Rough stepdowns to be toolpathed exactly as per the value you have input to the "Maximum Roughing Stepdown" box then you must place a value of 50% or less of the Roughing value in the "Fine Stepdown" box, otherwise the Roughing stepdown is changed.

Below the 50% value for the Fine stepdowns will determine how many passes there will be in between each Rough stepdown, example, my 1.0mm Rough and a Fine of 0.1mm will give me 10 toolpaths in between each 1.0mm Rough stepdown 🙂 🙂

OK, I ended up rambling again, it is all just for information for those few new individuals who may not have figured out the 3D Adaptive toolpaths so if it is of any use to anyone then enjoy 🙂 🙂 🙂

These ramblings of an old tired mind may be completely messed up but that`s all I have on it for now, anyone/everyone are more than welcome to disect/critique any/all of the above then please feel free, the more input on this the better, obviously the software has been coded to work this way but the why of it is escaping me right now 🙂 🙂 🙂

Regards

Rob

[daniel_lyall]

Chuck in order by depth to the pot.

[engineguy]

@daniel_lyall 

Don`t forget the "Order by Area" as well as the "Order by Depth" 😞 😞 😞

I have still to look into both of those, the "Order by Depth" doesn`t seem to work as I expect, it should move downwards but even with it enabled the Fine stepdown toolpath still goes from the bottom of the Rough stepdown upwards, not sure if that is what is supposed to happen but doesn`t seem right to me, suggesting that is a bit broken, but until I drill down into it I can`t be sure yet !!!!

Regards

Rob

[tnfjield]

@daniel_lyall, that makes sense!  I've seen that Fusion looks like it can avoid clamps, etc., but I haven't gotten around to trying it.  Thanks for the push in that direction!  Next project, I'll give it a go.  👍🏻

[tnfjield]

@engineguy, it sounds like something is broken to me!  I posted the possible bug report over in the Support forum, linked to this thread. 

When you did this investigation, were you using my model?  It seems that my actual model and my simple test file don't behave the same way.  In my test file the initial toolpaths are at the correct heights (dictated by the rough max stepdown) regardless of what I put in for fine stepdown.  The difference is only at the bottom.  With the fine set equal to the rough (both 1.0 mm) the DOC for all cuts is 1 mm, except for the next to last layer.  (I set the stock thickness to 6 mm for even numbers.)

1.0 mm / 1.0 mm

But when I change it to 1.0 mm for rough and 0.5 mm for fine, the all the toolpaths' DOCs are 1 mm.

1.0 mm / 0.5 mm

That's exactly opposite of what I would expect!

So I obviously don't understand the logic behind these values and how the toolpaths are generated.  Worse yet, is that the results seem to be dependent on the model itself, so we need to be sure to double-check that the adaptive clearing toolpath is doing what we want it to do.  It seems like the best bet for now is to follow your original suggestion and leave the fine at no more than half of the rough.  In that case, in both of these models, at least, it seems to produce toolpaths as expected.

As for the "Order by Depth" option, the tooltip leads me to believe that it means when there are multiple pockets then the toolpaths will bounce from pocket to pocket clearing layers by depth, instead of finishing one pocket, then  moving to the next, etc.

But it's a little unclear, and I haven't tested it.  In my simple model, it doesn't make any difference, and I didn't actually notice what was different in the large model.  Whatever it was, it didn't strike me as being important.  I probably need a specific kind of model for it to make a clear difference.

There is no tooltip for Order by Area, and the documentation only says, "Toolpaths are ordered by area rather than by depth."  But I would assume that if I didn't check Order by Depth then it would Order by Area, but I guess not!  🤔  Time to pull out the astrology charts!  🤣