5th axis tab off

I've been programing our 5 axis machine for about 4 months now (been programing with Mastercam for about 4 years), and I've seen a lot of videos of people machine a part complete, with the exception of the final bottom of the part where they machine away everything but a few little tabs to pull the part off (to either face down that side as a final op or just massage them off by hand).

Some examples:
5th Axis on Instagram: “c l e a n // @amt_machine #cnc #cncporn #runcnc #5thaxis #5axis #instamachinist #milling #machined #billetisbetter #engineering #cad #cam…”

Sam Tait on Instagram: “Drew up and machined this aluminium elbow for a turbo outlet today #cnc #machinist #instamachinist #engineering #designer #cadcam #5axis…”

Fil D on Instagram: “ holding on by less then .02 #matsuura #5thaxis #cnc #cncporn #machining #machinist #tablife #camplete @camplete @5thaxis @matsuurausa”

Is anyone familiar with this method? There doesn't seem to be a lot out there on how to do this, like how to program the final cuts, since I presume you want to cut back and forth to prevent the part from vibrating into the tool, and also how to approach these (ramp milling vs step down etc). Any tips would be greatly appreciated.

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To me this is a hard question to answer, given that tabs are very part specific. I'm currently working on a reasonably large part that is going to be difficult to hold for a second op back removal. So I'm making tabs. Design the tabs in a way where you can remove them easily with a deburring wheel.

First thing I do is make a duplicate solid model in mastercam, Create tabs and stock, move everything around until it looks right and Boolean that shit together to add the tabs and bottom stock to the solid, this is now my part. Draw it exactly as it will come out of the machine. This makes programming easier. For machining in general, I rough my tabs with a larger tool while it's still rigid, then cut away at them with a smaller too, less chatter. Unfortunately in my opinion you are never fully certain you've got the tabs right until you actually make the part.

Trial and error at first.

I think you really need t

This all depends on size and shape of your parts, but I usually just get stock that is about 1/2" taller sticking out and then use an indexable slitter to saw it off. Either to size or leaving .02" for cleanup in another op.

BRIAN.T said:

I think you really need t

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Damn, the 5 axis mafia took him out before he could finish the post [emoji1787]

Thank you though, this gives me a good starting point.

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IMO it is going to be very part specific. Can you get away with belt sanding/grinding off a little bit from the cutoff? If so, like brian said, going to be a bit of trial and error of what works on your machine and materials. If not (cosmetic, tolerances etc) might as well bite the bullet and make a second op to machine away the holding stock. Not ideal, but think about it, you *probabaly* have a part done in 2 ops now instead of 5 or 6 on a 3 ax machine.

Bottlecap19 said:

Damn, the 5 axis mafia took him out before he could finish the post [emoji1787]

Thank you though, this gives me a good starting point.

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Ha, I don't know what that was. I think my phone was about to die...or maybe it did.

Mtndew said:

This all depends on size and shape of your parts, but I usually just get stock that is about 1/2" taller sticking out and then use an indexable slitter to saw it off. Either to size or leaving .02" for cleanup in another op.

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Place I retired from did quite a few aluminum parts with the slitting saw to remove the part from the clamping stock. We would just leave a thin rib holding the part. Then at the work set station, the operator just gives the part a little twist to break if off. Sometimes just trimming off any remaining rib was good enough. Other parts would get skated on some 220 grit, while others would get a 2nd op to clean the edge.

One thing we did to improve the "behavior" of the part while sawing it nearly off, was to model the rib as a curve. That gave the part decent rigidity while allowing a very thin rib which still allowed the part to snap off easily.

Vancbiker said:

One thing we did to improve the "behavior" of the part while sawing it nearly off, was to model the rib as a curve. That gave the part decent rigidity while allowing a very thin rib which still allowed the part to snap off easily.

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Genius VanC. We use a big .122" x 6.3" disk mill and always get vibs on the second side of the cut. Gonna try that next week!

Another thing to improve rigidity when using tooling tabs is to use 3 staggered tabs like a 3 legged stool. Which is essentially what VanC does with his radiused rib. Really glad I checked in today.

Steve Austin