#qi-hardware IRC log for Sunday, 2015-08-23

--- Sun Aug 23 201500:00
DocScrutinizer05wpwrak: whitequark: https://www.youtube.com/watch?v=YWMjyAoxOfE  nice cooling/ointment10:08
DocScrutinizer05+ cleaning10:08
DocScrutinizer05lubricant fog10:09
DocScrutinizer05see how debris flies away at end of video when mill starts new job10:09
whitequarkshaking a bit every time it steps down19:43
whitequarki'd do a constant ramp down or something, like a helix19:44
DocScrutinizer05yes. tell that wpwrak20:48
wpwrakwhitequark: DocScrutinizer05 doesn't believe that endmills (in general) can cut straight down :)22:02
rohwpwrak: well.. some can, not all 22:14
DocScrutinizer05generally it's tricky22:18
DocScrutinizer05having X/Y movement while going Z+ is always way simpler/easier to the mill22:19
DocScrutinizer05for those endmills which are supposed to be able to to Z+ only, you still might need to match some other requirements like wetting, correct RPM vs advance-speed factor, or whatever22:20
DocScrutinizer05to do*22:20
wpwrakroh: yup. some will only cut sideways. but they're clearly marked as such. just like endmills that transport material down instead of up.22:21
DocScrutinizer05nah, the problem is system immanent22:21
DocScrutinizer05even mill heads supposed to be able, are still poor on it22:22
wpwrakDocScrutinizer05: you always need to consider spindle speed, feed rate, irrespective of which direction you go22:22
DocScrutinizer05but you deny the fact that there's a system immanent problem with milling Z+ down only22:22
DocScrutinizer05you simply say "that mill head is supposed to be able to do it, so why the heck it doesn't work"22:23
wpwrakthink of an endmill as a short drill. just that it's not pointy but flat. drills go along Z just fine. the don't like XY because they tend to be long, so they'd snap.22:23
DocScrutinizer05just that an endmill is NOT a drill22:23
DocScrutinizer05exactly, it's not pointy22:23
DocScrutinizer05which is the whole problem22:23
DocScrutinizer05huge endmills even *are* ether pointy or inverse-pointy to compensate for the system immanent problem of zilch cut velocity in center of axis22:25
wpwrakpointy vs. flat mainly affects lateral control. e.g., you'd hate to hand-drill with an endmill. but CNC mills are all about firmly holding things in place.22:25
DocScrutinizer05the point is about piercing the material instead of cutting it22:26
wpwrakany drill has a stationary center axis22:26
DocScrutinizer05yes, and since it's pointy it will just go through the material by pressure per area22:26
DocScrutinizer05an endmill can't do that22:27
DocScrutinizer05the pinpoint is not just for centering22:27
wpwraki suspect it's more force on material off-center that just moves the (infinitely thin) center column as well, but again, that's the same in all cases22:28
DocScrutinizer05it's meant to overcome the system immanent problem of zilch cut velocity22:28
DocScrutinizer05you obviously know why it should work, you don't know why in practice it doesn't22:29
DocScrutinizer05I also think I know how it should work (in a different way than your preferred one), and I know it usually works in practice22:30
wpwraki see it work almost every day in practice, manuals from companies making this sort of tools and devices recommend exactly what i'm doing, and other people with experience in the field don't see anything amiss with it either ;-)22:30
wpwrakit almost seems as if we're arguing zeno's paradox :)22:31
DocScrutinizer05you evidently got three system immanent problems: zero cut speed, zero transport speed, and zero transport grooves - in the center22:32
DocScrutinizer05huge mill heads avoid those problems by either a positive or negative cone in the middle22:33
DocScrutinizer05a simple never failing way to avoid the problems by operation principle is to add Y/Y velocity when going Z+22:34
DocScrutinizer05so exactly what whitequark said initially22:35
DocScrutinizer05when you insist in doing it the way that's maybe *supposed* to work, but actually gives you problems - I dunno what to suggest22:36
DocScrutinizer05it's just funny that whitequark and me both noticed even that professional mill in the YT vid I lonked had obvious stress wenn doing Z+ only. which is where the whole discussion started22:39
DocScrutinizer05so you hardly can discuss away that there *is* a system immanent problem with doing Z+22:40
DocScrutinizer05you say it should work nevertheless. I say when it doesn't you should add X/Y velocity22:41
DocScrutinizer05you seem to not like that idea, for whatever reasons22:41
DocScrutinizer05btw zeno seems to have postulated several paradoxes ;-)  https://en.wikipedia.org/wiki/Zeno's_paradoxes  which one you choose?22:51
DocScrutinizer05"Arrow paradox" sounds like an early version of Heissenberg22:53
DocScrutinizer05"Paradox of the Grain of Millet" exceeds my English, or my logical understanding22:56
DocScrutinizer05(endmill) lemme put it this way: when there wasn't any problem, then why do they make nails pointy instead of flat?23:03
DocScrutinizer05on topic: did you know that you should flatten the nail's pinpoint head a bit (by hitting it with the hammer) when you want to drive the mail into normal wood?23:05
DocScrutinizer05otherwise the nail might just split the wood fibres and that split can grow23:05
--- Mon Aug 24 201500:00

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