Fusion 360 Multiple Passes max depth not being honored?

[friolator]

I'm trying to run a fairly large adaptive clearing pass on a piece of 1" HDPE. I used the same end mill and same settings on a piece of 1/2" HDPE and found that the best results were with the stepdown set to .03"-- Cut like butter. So when i went to do the other half I modified my Fusion 360 file so that all the operations using the 1/4" end mill have the same stepdown (I'm doing this in Passes / Multiple Depths / Maximum Roughing Stepdown). 

However, when I ran the piece, the first cut immediately ramped down to .125"

I tried setting it to an even smaller number - .02 - and post processed it. Same result in UGS - it's ramping down to .125, which is too aggressive for this, and the router starts to chatter while cutting. 

Any ideas?  

[Derek the Admin]

I would suggest posting the Fusion file so one of us can look at your setup and tool paths.

[friolator]

Sure. Here's a link: www.dropbox.com/s/z832q4yysdl0ew8/Dust%20shoe%20v28.f3d?dl=0

The part i'm having trouble with is the more complex top frame, not the brush frame, which ran successfully last night. 

I guess the question is - what is the right place to set the stepdown? I used the Passes/Multiple Passes/Maximum Roughing Stepdown setting, which seems logical. But it didn't seem to have any effect on this one for some reason. 

[Derek the Admin]

I’ll give it a look this evening when I am at a computer bud.

[friolator]

Thanks. No hurry - I'm not going to be back near the router until Monday anyway!

[Derek the Admin]

Here are a couple observations:
You are adding some extra stock to the bottom of your material. Your model is 1 inch and you are adding 0.012 stock to the bottom. If your material isn't 1.012" thick and you are zeroing exactly to the top of the stock, then you will cut through there.

I can't say why you it initially goes 0.125" deep but I have a feeling you don't have something set right. Looking through your CAM toolpaths you aren't going to get what you want. Simulate it with stock and you can see it is leaving a bunch of material that isn't there in your model. You have the wrong things selected in your adaptive clearing. You are selecting contours and not getting the material cut away. Select the face instead.

[Big Man Black T-Shirt(Patrick)]

Good on ya, Derek, for the in-depth reply. I often browse through and learn a lot from other people's problems. Your involvement and willingness to help us will surely pay dividends with your business. Not many other business owners are as involved in the community aspect as you are.

[Derek the Admin]

Thanks Patrick. I think this has gone so well for us because I really love this stuff and seeing people succeed. We can’t officially support the applications side of things (IE particular projects), but I do like these public discussions that help make everyone more successful.

[friolator]

Just to follow up (been swamped with regular work and haven't been down to the workshop in over a week), Derek was right - my CAM settings had a stock offset that was causing the problem.

[Derek the Admin]

Glad that helped out.