[tlharris]

I'm hoping someone can help educate me on this one -
I don't do a lot of 3D milling, so maybe I just don't understand all the nuances of some of the strategies.

Here's a really simple mold part.
My thought was that I should be able to use a roughing routine to handle all the flats. I know that I COULD use a finishing routine after that, but I'm asking why I need one. I'd like to be able to run a 3/8" flat cutter, and use 1 intermediate step to get close to the fillets. Then switch to an 1/8" ballnose to go clean up the corner fillets.

The question is.... why do I end up carving trenches with my 1/8" ballnose? It cuts just exactly the way that it looks in simulation. I would hope that advanced rough should be able to get me down to the flats. Am I missing something really basic?

I can't see where Advanced rough should be leaving anything for a finishing pass.
Many thanks in advance -

Todd

[tlharris]

I should have asked also....
any advice on alternate strategies for things like this would be appreciated.

This particular part is a mold for a foam-cast piece. It's a theatrical prop, so surface finish isn't the biggest concern. Molds like this are cut out of melamine or mdf, then sealed and cast with expanding foams, hard urethanes, or fiberglass. I'd love to optimize my workflow here.

Thanks again

[SBC Cycle]

I could offer other suggestions but both a general strategy and a part specific suggestion would be to always consider using the "Bottom of Job" setting.

With your step down and intermediate step settings, the deepest the toolpath will calculate is -0.300" and the floor of your mold is -0.350". Adding the "Bottom of Job" setting can force the Advanced Rough to the actual depth you want so you don't have to "fine tune" your step down to hit the floor exactly at depth (0.350)"

There are other methods but using the "Bottom of Job" is always useful to me.

[tlharris]

Thanks, SBC.
Bottom of Part does seem to help with the bottom trenching, but doesn't affect the one on the upper flat at all.

Interestingly, It doesn't seem to be an Advanced Roughing issue. Similar results using Z-level rough.
Maybe I'm just naive in thinking that a roughing toolpath will actually compute up to the workpiece? I was assuming that Allowance XYZ of 0 would result in toolpath on the workpiece surface.

[BurrMan]

Here's a video that will describe whats going on:

z_level rough constrained - YouTube

The roughing features are a material removal operation. Not a finishing op. You can make it a finishing operation, but would have to set the parameters to match the surfaces your are roughing. WHat you might want to do, is run a "flatlands" just after the rough. (It would be nice to get a "stepdown" parameter in flatlands that would solve this) You could calc one less pass on the rough, then immediatly run the flatlands with the same tool as the last pass.

Essentially, with a step of .2 you are saying it is ok to leave -.2 anywhere on the part to meet the params.

Hope that helps.

[Force]

BoJ is fine when there is only one in the cavity. In the main my jobs have 2 or 3.

[SBC Cycle]

BoJ won't solve a step down issue when using a roughing toolpath as a finishing toolpath. As I said, it makes it easier to make sure you hit the bottom just right.

I haven't seen Burr's vid yet but in the sample file above I can change the step down to 0.3 and add a BoJ setting of -0.350 and the toolpath will hit all the flats perfectly. If the bottoms of the cavities are too varied to hit "just right" with the stepdown/intermediate functions, you should use a different FINISHING toolpath like Flatlands instead. Advanced rough can definitely be used for a finisher, but be prepared to do some work.

[bobcad guy]

I use advanced rough to finish all the time, cause theres no advanced finish option, but its such a great toolpath, and can save so many steps. that's why I care how well advanced rough works so much. maybe im lazy, dunno, it just eliminates alotta guess work. I sometimes will use one advanced rough op to do one depth, then define another to do the next depth, with a "top of job" set to get past the first depth. or you can use the second adv rough to be your fin, with one step to full depth. its very flexable, I think the only rule is, your step downs must equal the actual amount you want to go. I think when you say a stepdown of .200, and you have a pocket of .250 deep, it will only cut to .200 deep, it wont go back for the other .05. sometimes bott of job forces it to, but it easier to have the equal steps to full depth. I could be wrong, but I believe this all to be true

[BurrMan]

Well, it's a "roughing strategy" and you could use it to finish parts, if your a glutton for punishment.....

[SBC Cycle]

I use advanced rough to finish all the time, cause theres no advanced finish option, but its such a great toolpath, and can save so many steps. that's why I care how well advanced rough works so much. maybe im lazy, dunno, it just eliminates alotta guess work. I sometimes will use one advanced rough op to do one depth, then define another to do the next depth, with a "top of job" set to get past the first depth. or you can use the second adv rough to be your fin, with one step to full depth. its very flexable, I think the only rule is, your step downs must equal the actual amount you want to go. I think when you say a stepdown of .200, and you have a pocket of .250 deep, it will only cut to .200 deep, it wont go back for the other .05. sometimes bott of job forces it to, but it easier to have the equal steps to full depth. I could be wrong, but I believe this all to be true

I agree with just about all you say here, what I bolded would be words right out of my mouth. In particular, creating multiple features to get the correct depths. This is how I expect it to work. I do not expect it to automagically do the step down work for me. It is easier and more predictable to create an extra Advanced Rough feature to accomplish the job the OP expected from one feature. IMO, that IS the lazy way. I can't imagine it takes more than 2 minutes to save a feature, reload it, and enter new DoC, ToJ and BoJ settings. Sometimes I feel like working hard and making it all happen in one feature by calculating the necessary step and intermediate steps (I have a formula that helps) and I can hit every floor, perfectly. Waste of time, most of the time. That's my workflow and just like you, it's because I'm somewhat lazy.

I realize the OP is new to working in 3D milling and is looking for a workflow. We can have a discussion about how me, you, and OP think Advanced Rough should work. But that's not helpful to OP because there is a certain way it works, and that's that. I can break it down in detail how the Advanced Rough handles step downs and intermediate steps (with and without XYZ allowance) with ToJ and BoJ settings but that should be well covered in the Help documents.

I would do the flats in OPs part with one Advanced Rough feature, Depth of Cut @ 0.300, 1 intermediate step, BoJ at -0.350. Done.

Pencil for the bottom and boss fillets. Done.

Either Slice Planer or Z Level Finish for the 2 corner rounded edges that are left if you want to stick with the ball nose and generate it. Me personally, I would use a 2D profile and a corner round tool. Done.