Wow, fixed my ATC!! And the existential consequences thereof...



A Mazak SQT has 10mm pitch X axis, and IIRC, 15 mm pitch Z axis. Let your encoder get off 1 rotation on one of those...hehe... 30,000 mm/min Rapid (1181 IPM) You will NOT get it stopped in time with the 'It's too late' button.
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Anthony

You can't 'idiot proof' anything....every time you try, they just make
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the
Those H800's I used to run were the same way....feed hold was about six inches into the crash zone......
==LEARN TO READ CODE---DONT LET IT BE A 'SURPRISE'......
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SVL




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PV,

I
Those are metric screws. Fadal started using them when they went to AC servos. A whole lot fatter and stronger than their old 5 pitch screws. They also have Dowfrost from the spindle chiller runnig through them to keep them stable.
If you want more accuracy, you can program in mm. Four decimal places in mm is alot tighter than in inch.
You were joking about changing them,, right ???
Regards
Mark
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Proctologically Violated wrote:

Dude!
Howja think dem superfast rapid numbers got inta all the 'chine-sellers brochure thingies? Y'all want big rapid rates? No prob. Ah'll jes get me some big, BIG muffuggin pitches on dem screws, an' tighten the strap on mah helmet. Slick as turkey shit, an' stinks jus as bad when the muffuggin bearings git blown right out thru da end o' da muffuggin table!
God, I hate it when people talk like that. I even hate it when I do it.
There was a time, ages ago, when almost every good quality machine tool had 5mm pitch screws. For the folks who wanted to stick with English numbers, there were .200 (5 pitch) models. And for the really big machines, like boring mills, maybe a 10mm pitch; but it was on a screw with a much bigger OD, so the helix angle, and the net mechanical load, were still something that sane engineers could live with.
Then, just when everything was running all nice and smooth, some clever clown in the sales department felt the need for speed. For a while, that was OK. Faster computer chips, faster servo drives, and faster feedback sytems, all added speed to your basic good quality machine tool. They just spun the motors faster, and life was good.
But speed is addictive; and once we got a taste of it, we just couldn't get enough. 10 meters per minute had been ok for a while. And 20 meters per minute had been exciting for about a month. But then we wanted REAL speed, like the kind that never actually happened because the accel/decel curves were longer than the whole machine.
So we maxed out the motors, and then needed more. And the only way to get it was with longer pitch screws. 10mm replaced 5. Then it was 15mm. And now, in the machines that travel at 60% of lightspeed, the pitches are so long that the mechanical advantage is actually upside down, and the thrust produced by a table or spindle is actually LESS than the torque from the motor. But we don't care, 'cause the machines are moving FAST.
And, as someone else mentioned, machinery builders could probably save money if they just didn't bother with the feed-hold or E-Stop buttons. Unless you're clairvoyant, and can see into the future, there's not a chance that either of those will ever do you any good.
And yes, you can and DO get a whole lot more accuracy and resolotion with finer pitch screws. That's why I use 2.5mm pitch screws on my grinders. And 24,000 pulse/rev encoders. In theory, with a calculator, I get a minimum motion increment of just four millionths (0.000004) of an inch. In reality, the machine's not that good. But even if the mechanical stuff screws things up by a whole order of magnitude, I can still split a single tenth into a couple nice equal pieces, and have change left over for my piggy bank.
But accuracy isn't the "hot thing" these days, except in a few specialized markets like mine. Folks want speed. And that's what they buy.
I know of some machining centers that will literally (seriously!) walk themselves across the floor, if they're not lagged down. The sudden, high-rate starting and stopping of surperfast tables and saddles (and whole columns, ferchrissakes!) is an awesome thing to see (as long as you're standing safely off to the side, of course). Other builders, who don't like replacing crushed thrust-bearings on a weekly basis, opt for long accel/decel strokes, to soften things up. The fact that max rapids can only be achieved after the machine has moved a distance aproximately equal to the whole shop, plus the parking lot, seems not to deter anyone who wants to play the speed game. If we can legally claim that it rapids at mach 9, then that's what we're gonna do, even if your stopwatch and your maintenance budget might want to argue.
And for those who are REAL speed addicts, there are linear motors. Nothing rotates. No pitches or screws at all. Just unwind the whole damned servo motor, lay it out flat on the floor, and turn on the power. The only actual speed limit for those babies is the speed of propogation of current through a wire - which really IS within just a few percent of light speed. Of course, since there's a load to carry, and maybe a milling cutter in the path of that load, we haven't actually seen relativistic velocities, just yet. But you can bet your toolbox that somewhere, in the back room of some machinery builder's R&D center, there's a prototype in progress, and some engineers wondering why their wristwatches all seem to run backwards, whenever the rapid over-ride switch is set to 100%
Hold onto yer hat. And hold on to that (relatively) tame screw you've been playing with. Someday, you'll remember it with a fond sense of nostalgia.
KG
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<snipped>
Kirk,
It all has to do with your acceleration curves...top speed is meaningless on a one meter machine if it takes one meter to get it up to full speed...esp. if your workpiece (s) are 1/10th of that size....
IOW, lots of it is simply marketing hype....you can add bigger servos, yes..but at the disadvantage of ( much ) shortened leadscrew life when you go to higher pitches.....
( this message will self-destruct in ten seconds )
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SVL



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PrecisionMachinisT wrote:

Welllll .... Santa Cruz Mike had a late-model Chevalier (? think it was a Chevalier) beefy knee mill with a late-model control. Then he bought a 1980 ExCell-O 104. The ExCell-O has about 24" in X and maybe 16 in Y and Z. Cute little horizontal. I think the rapids were actually the same as his Chevalier but the control was a lot older. Same parts, same program ran about 25% faster on the ExCell-O. Sumbitchin' beefy Gettys drives DO make a difference. That'd make a great project, imo - linear motors on that little mill. The thing is built like a brick shithouse.
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With the new digital drives, esp from Siemens, it is possible to really tailor the accel/decel curves a lot. It's not the old linear lopped-off triangle anymore. Parabolic curves are in use now, where you can get the mechanical slop and get everything tensioned before you do any serious acceleration or deceleration, then you ease it out at either the top or bottom of the curve. It saves tons of mechanical wear compared to linear systems, and takes the shock out of the system. It's the jerk that gets you.
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Anthony

You can't 'idiot proof' anything....every time you try, they just make
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Callin me a jerk now are you ???
<G>
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All fine in theory, but exactly how often do you have ten miles in which to accelerate to top speed??..........real handy when all your coordinated moves are all .00125in or less.......NOT...
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Kirk Gordon wrote:

There's one from the airport in pudong to downtown shanghai. 453 kph, I think. It's kind of a fun ride. I always hope they charged the batteries cuz it'd make a heck of a racket if the power went off :)
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hamei wrote:

A linear motor? Really? That's pretty cool. The battery thing is surely important, though. And maybe a REALLY good cow catcher. Is this a walkway, a train, or what?
KG
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Kirk Gordon wrote:

It is pretty kewl - normally it's a one-hour ride but the maglev does it in seven minutes. Only $6, too, but then this *is* a commmmunist country :)
have to admit that your idea is better tho .... a walkway. Maglev boots that you strap on. Whoa babee, *now* we're talkin' Dodge Charger !
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Fields, both electric and magnetic, both propagate at the speed of light, at least according to JC Maxwell. Might be a tad slower in various media. The electric current itself flows quite a bit slower. At least dat wuz what I was told. ---------------------------- Mr. P.V.'d formerly Droll Troll

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Proctologically Violated wrote:

It's a CNC grinder for sharpening high-performance drills. It's small (around 4,000 lbs.), and doesn't need to be real heavy or powerful. It's designed for relatively light stock removal with carbide, HSS, or cobalt. And extreme accuracy isn't optional if you want the drills to work right. The big machine will do drills up to an inch; and the small one is for 5/8" and under, with room for an occasional 3/4" drill if you don't need to go too fast.
What's interesting is that the accuracy really works. I can take the run-out in the work-head spindle, and in the collet chuck, and in the collet, and add all those to the machine's positioning errors in four axes, plus the heat and pressure from grinding, and everythihng else that matters, and still get .0001" TIR lip-height difference on a 5/8 or 3/4 drill. And I can do that all day long. Even under the worst circumstances (worn wheels, high-volume runs, really bad drills that need more than normal stock removed, etc.) my customers typically won't tolerate a drill that runs out more than maybe .0003" TIR, unless they know it's a low-quality HSS drill that probably wasn't straight to begin with.
Prices are around $90k for the small machine, and $140k for the big one. The big one has some bells and whistles, like a three-stage filter system for the coolant (or oil, preferably), and an on-board video inspection system.
How many do you need?
KG
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Kirk Gordon wrote:

I want to test it first... I got a box of drills that need sharpening <G>
John
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