Failure - a stop on the road to success

[kec-10238]

So I attempted my first project which was just a simple profile shape - nothing else. I was trying to cut .025" thick aluminum (very thin). I sandwiched the aluminum between 2 pieces of wood. I then put a screw into each end of the wood aluminum sandwich combo so the aluminum wouldn't move. Cut through the wood perfectly but then grabbed the aluminum as soon as it got through it and started  pulling the piece along with it (yes it was clamped and clamped hard). hmmm. End result failure! Was using a 1/8" fishtail end mill - 3 flute running the router as fast as it would go. I don't remember what my feeds and speeds were but they were suggested by the bit guy Ron at precisebits.com for doing this. Immediately following the failure I had a computer I went to my computer and it also had a disk failure and I had to reinstall an image back-up to get things going again - an all day time consuming waste of a day! Now all is good and will have to attempt again in the very near future.

[aforww]

Looks to me like it wasn't cutting worth a damn. Without knowing your speeds it's hard to say but I can tell you it got way too hot and you weren't evacuating chips nearly fast enough. Looks like the bit was trying to plow it's way through instead of cutting. I'll remember not to go to them for info. Lol

[kec-10238]

Oct 12, 2017 16:49:01 GMT aforww said:

Looks to me like it wasn't cutting worth a damn. Without knowing your speeds it's hard to say but I can tell you it got way too hot and you weren't evacuating chips nearly fast enough. Looks like the bit was trying to plow it's way through instead of cutting. I'll remember not to go to them for info. Lol

not sure if the speeds are being sent from vcarve to vcarve's grbl post processor and/or if grbl/UGCS is ignoring them and using the feeds in UGCS. not sure. If not, that may be the problem as they are entered in as part of the tool type being used in vcarve - not quite sure what happens when it creates the g code. I have not had a chance to look at it and can't since vcarve and the vcarve projects were the only thing I lost (was not on image file yet-just installed) with the disk failure. So I have to re-enter all my tools/types/geometries again to recreate it. yuk yuk yuk. A learning experience. Install a new program and get it set up - do an image back-up right then and there - don't wait.

[Derek the Admin]

I know what you were getting at with the sandwiching method but I don't like it. Unless you run roughing passes the chips have a hard time clearing out of the kerf created in the wood (same would apply to a deep cut in really thick aluminum).

As Aforww mentioned, it doesn't look like it was cutting very well. Do you know what alloy of aluminum it is? And from the looks of it, is it aluminum dibond? Dibon has a plastic core so it can also be prone to melting and galling to the end mill (as can aluminum). Generally speaking, an alloy like 6061 cuts pretty well. Something like 5052 likes to get gummy, gall to the cutter, and break or just start getting plowed, kind of like happened with you.


On a slight related side note:
I think you have to take feed and speed recommendations with a grain of salt as well. Those are usually aimed at the ideal load on the cutter and presupposes and industrial level machine that will have no problem with the cutting forces resulting from a particular load. For instance, that guy may be telling you to get a .004" or higher chip load in aluminum with a 1/4" cutter. To get there, he could have you running 140 IPM at 16k on the router. Depending on the depth of cut, that going to be too much force. This applies to the CK and really anything in it's class (the Carve King actually takes pretty aggressive cuts for its class).

What feed rate, RPM, and depth of cut did you use?

Also, to answer your question, UGS is just taking the feed rate given to it by the g code. UGS Platform does have a feed rate override for Grbl 1.1 (you have Grbl 1.1), but it defaults to no override.