Seeking 4th Axis Insight

An introduction: I have a project I'm working on to challenge myself. It's a small ornament ('tis the season, right?) made from 1" round stock using Fusion 360 and 4th axis positioning, 3D surfacing, and eventually a breakoff "tab" that will be buffed out, leaving a finished part.

I'm hoping that some folks can chime in with how they work with complete parts in a 4- or 5-axis setup and wind up with that little tab they can bend the part off of. HSMWorks experience would probably be most relevant, but really any input is good. Do you limit machining areas with sketches, or create extra stock solids to work from as the job progresses? How much indexing is used, and what orientations do you find to be important?

I'm pushing myself where work likely won't so I can learn and get better. Here's sort of where I'm at now, but this may change in the next 12 hours

I did a pretty complex part (sorry no pics, itar controlled) that I machined complete on a 5 axis and did a similar approach. I did not leave a tab to bend off, I left some beefy material (stock size was 2"x5"x5") to machine off. I used Mastercam, so my process is different, but the same principal. I just created some wireframe geometry to represent the "tab" and machined around it. After the part was finished I just took tiny depth cuts, about .01", with I think a 1/4" endmill. I think I stopped leaving about .01-.02" and then I took the part out of the 5th axis vise and used tin snips to separate the leftover stock and the part. I then did as you are thinking and belt sanded/filed the remaining.

Your part is not very big so this doesn't apply, but I did learn to machine the part in 'steps'. Similar to how a swiss type lathe works, they machine segments (or whatever you want to call them) as the stock is then fed through the bushing. What I did was machined the furthest end away from the vise complete, minus like .003" for finishing, and repeated as I moved towards the vise. I think I split this into 3 sections more or less. The part ended up with most sections being a 1/4" thick, think like a top hat, with a hollowed out boss in the center and the "brim" of the hat extending outward. One thing too, the cutter has to be razor sharp or it is going to chatter when doing this method. Even if it feels sharp, you will know immediately if its not!

Heading off to bed now, but here's the roughing I've got worked out thus far. It's constrained in the first operation with a solid, and the second by a solid and a sketch boundary to keep it away from the chuck. As always, insight appreciated!

4th Axis Roughing | Fusion 360 | Autodesk Knowledge Network

Your going to have to take it a little easier on that last op in the video. You may even want to semi finish the "bowl" area before you attack the back end. If any doubt, there WILL be chatter. Leave the most stock you can afford to finish the bowl, then worry about clearing the back side. YMMV

Rstewart said:

Your going to have to take it a little easier on that last op in the video. You may even want to semi finish the "bowl" area before you attack the back end. If any doubt, there WILL be chatter. Leave the most stock you can afford to finish the bowl, then worry about clearing the back side. YMMV

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Oh I intend to. I'm sort of working out the roughing before doing semi- and final finishing paths.

Do you need to remove as much material as you show in your screencast? That tab is getting pretty long. I would leave just enough to finish it off with an 1/8" mill, or so.

Please post as much about this as you can. I have a new part/ possible product that I am looking at making that would be made the same way in the 4th, very similar in many ways to your part. This would be the first I have tried 4th axis programming in Fusion so any info would help.

No CAM makes this easy, you have to really work to figure out how to get it to work from the end of the stock progressively, leaving extra support material along the way to keep things chatter free. You want to finish things earlier than normal in areas where you can still get good support. As others have said, I would not remove too much support before finishing the inside as well as most of the sphere shape.

You should finish most of the bowl shaped part before you work your way back. Maximize rigidity.

Your tab only needs to be about the width of the endmill you'll use to "part off".

In order to make your CAM life easier I would model an "attachment" onto the back of the tab. Something small that necks back to a larger support. That way your CAM won't try and cut the part completely off and you don't have to spend a lot of time controlling it. I've found this is the easiest way on something like this.


I would also divide the surface of the sphere so that it has more than one continuous face in order to rough and finish as you go back. Lets you avoid drawing boundaries and such.

The more prep work you do to the model the better off you will be.

If you send me the model I can take a few pictures on how I would do it tonight.

I normally model a spigot running to the part and label that body as fixturing in gibbs. This causes the surfacing and other ops that are paying attention to material to avoid those areas. Then we snap them off or use a hacksaw and fixture them to remove the spigot from the 4th axis op. Containment sketches and boundaries accomplish the same thing it just comes down to what you're more comfortable with.

How do you like HSMWorks BTW? Seems like very pretty/powerful/affordable software for the cost. They have a free demo and I was thinking about giving it a shot and if I like it use it alongside our Esprit.

StreetSpeed said:

How do you like HSMWorks BTW? Seems like very pretty/powerful/affordable software for the cost. They have a free demo and I was thinking about giving it a shot and if I like it use it alongside our Esprit.

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jid2 is the one to ask about HSMWorks, we just have HSMXpress until the switch in February. That said, I really, really like it. Workflow is intuitive, it's very easy to set defaults, make toolpath patterns to follow alongside in SW, all sorts of things, and continuous development that can be "interacted with" via the forums.

That said, I have heard lots about how it lacks in turning, although supposedly they have handed over that functionality to one guy to fix, so hopefully that's going on.

Sorry about no updates, I've messed around a bit with the roughing order and think I'm pretty happy with it, but will have to start on the finish paths soon.