How to rough machine this piece?

[traditional.builds]

For some reason this piece is giving me lots of trouble. I think it may be because of the large stock I am using. I need to repeat this part 4 times on the same stock, but I'm just trying to lock down 1 so I can understand the toolpath.

I plan to rough cut the part with a 3/8" downsheer and then finish it with a 1/2" ball. The part I'm having trouble with is the rough machining.

It either wants to plow the whole part out, as if it's not there. I was somewhat successful with adaptive clearing, but I keep getting "rapid collision with stock" errors.

Any help would be awesome, even if it's just a point in the right direction. I'll attach the file too.

Thank you!

[seth.madore]

What's keeping the part restrained (what's preventing it from flying off)?

Are you looking at removing ALL material that's not the finish part, or are you expecting to see a "window frame" of material left over?

Are you machining these all at the same time, or are you expecting to rough and finish one before going to the next?

[traditional.builds]

I am planning to onion skin or just leave tabs. I'm working off of a vacuum spoil board, and I can also secure it to the table even more if need be. 

I was hoping to machine them all at once, but was only focusing on 1 for now. I can always duplicate the toolpaths, or just run them one by one if I have to.

I got close, by doing a step down 2D contour, making sure to leave around 3mm, then I set up an adaptive tool path to rough out the slope, and then finally going in with a parallel toolpath with a ball. It's working but it took me a lot of trial and error.

[seth.madore · Accepted solution]

Give this a look.

I went with:

1) 2D Contour (with Tabs) to cut the part out (you'll likely want to have multiple depths and a finishing pass)

2) 3D Contour to rough off the sloped surface

3) Flow (Preview) toolpath to finish the sloped surface, using a ball endmill.

[traditional.builds]

I really like this.

Is there a way to step down the second contour operation that roughs out the slope? I'm machining this out of raw oak and only wanted to step down a few mm at a time. Since it's a contour operation I haven't figured out how to set a step down limit.

[seth.madore]

The stepdown value of 3D Contour (second toolpath) can be controlled by a value on the Passes tab:

 

Or, are you looking for something else, and if so, what/why?

It looks like all the Homag machines are quite beefy in size and ability, so there shouldn't be a huge issue with deflection. I had the 3D Contour leaving .5mm axial and radial "Stock to Leave".

[traditional.builds]

I guess I am being cautious of removing 12mm of solid oak material towards the end of the slope roughing contour operation. I was hoping to step down the operation in increments of 5mm to be safe. When I adjust that stepdown value you showed me it seems to affect what I would call the stepover. Lowering it also creates "rapid collision with stock" error, but I was able to fix this by adjusting the lead in/out values.

This definitely gets me close though! I was just worried about the amount of material that is being removed during the roughing. I already set the maximum stepdown for the initial contour with the tabs.

[programming2C78B · Accepted solution]

assuming this'll be wood

2D contour slot around the part, leave 3mm on the floor. 3D adapt the ramp (if truly needed). STL on the walls is up to you.

3D Ramp, scallop, or even spiral the surface. 5-10% stepover at max feedrate. Avoid the surfaces on the end so it doesn't try to plow down to your table surface. 
2D contour w/ tabs finish OD 

Would take about 15mins to program on my end. 

[traditional.builds]

This got me close enough to finish how I wanted so thank you , this was extremely helpful and by looking at the operations you set up it helps me better understand how they work so I can do it myself in the future. Thanks Seth!

[traditional.builds]

Very similar to what I ended up doing, building off of Seth's response. Thank you!